Database Users

Mains adaptor query

Appologies for duplicating this post here and on the accessories forum but needed a quick answer!
Anyone technically minded who can answer this....
I am using a HTC Touch Pro mains charger for my X1 (as it has a longer cable) which charges the X1 fully.
I did notice the back of the X1 getting a little warm, so double checked the outputs on the original X1 charger and the TouchPro one.
X1 = 5v 700mA
TouchPro = 5v 1A
Is this likely to be a problem?

You should definately not mix power adapters like that. On the other hand they both use mini-USB plugs so if they follow the USB standard (Battery Charging Specification) you are okay. The spec allows for up to 1,8 A, but that does not mean the X1 can take it.
I would have rather bought an extension cable for the X1 charger. Then you are safe _if_ anything happens and you damage your X1. :|

If you need a longer cable, just plug in a standard USB extension cable It will work perfectly and you can extend to plenty of meters if you need to.
Regarding the use of the 1A charger, I don't think it will be that much of a problem, but I wouldn't count on it to cause no problems either. The battery getting warm is not that odd when charging, as batteries generally generate heat when they get charged. The fact that it gets warmer with the 1A, instead of the 0.7A charger, is just because you charge the battery quicker, which in turn causes more heat. You should keep it mind though that heat is a bad thing for LiIon batteries like the X1 uses. Having it being warm reduces lifetime quicker then when it's cool.

maedox said:
You should definately not mix power adapters like that. On the other hand they both use mini-USB plugs so if they follow the USB standard (Battery Charging Specification) you are okay. The spec allows for up to 1,8 A, but that does not mean the X1 can take it.
I would have rather bought an extension cable for the X1 charger. Then you are safe _if_ anything happens and you damage your X1. :|
Click to expand...
Click to collapse
Thanks for your help. I assumed - like you - that USB was USB in regards to power output. But I will take your advice and get an extension and stop using the old one.
Cheers
.

What I've seen on battery charging on mobile phones is that they have an internal intelligent charging system, at least the Siemens and Wavecom systems I've been using.
LiIon batteries are normally charged using constant voltage/constant current until a certain voltage level is reached, ~4.2V for 3.6V batteries. Then the charge current is reduced with a constant voltage until the charging current reaches zero. This implies that from a 5V charger there has to be some sort of internal charging system to make it work.
If you get a charger for USB it is the internal system that handles the current rate, not the charger. The specs on the charger shows the maximum current possible, not the charger's constant charge rate.
So if the phone's internal charging system thinks it's ok with 1A it will use it, but as mentioned earlier, it will produce more heat, but with a faster charging.
Though USB charging specs is limited to 1.8A, most charging circuits is possible to set to less current, with some part charging the battery, the rest powering the phone.

on8a said:
What I've seen on battery charging on mobile phones is that they have an internal intelligent charging system, at least the Siemens and Wavecom systems I've been using.
LiIon batteries are normally charged using constant voltage/constant current until a certain voltage level is reached, ~4.2V for 3.6V batteries. Then the charge current is reduced with a constant voltage until the charging current reaches zero. This implies that from a 5V charger there has to be some sort of internal charging system to make it work.
If you get a charger for USB it is the internal system that handles the current rate, not the charger. The specs on the charger shows the maximum current possible, not the charger's constant charge rate.
So if the phone's internal charging system thinks it's ok with 1A it will use it, but as mentioned earlier, it will produce more heat, but with a faster charging.
Though USB charging specs is limited to 1.8A, most charging circuits is possible to set to less current, with some part charging the battery, the rest powering the phone.
Click to expand...
Click to collapse
Thanks very much that's very informative.
I am wondering if the X1 has this internal intelligent charging system you mentioned. Would be useful to know.

Actually the mA ratings are what the charger can deliver. Not what they actually will deliver. A 700mA rated charger will supply up to 700mA if asked for by the device. This is a two way thing. The charger side will never provide more than it's maximum rating, it's a built in safety thing. The charged side should never ask for more than it can handle, providing that it is a well built piece of electronics. I trust the X1 to be well built on this. USB standards rate a maximum of 500mA for high power devices. The X1 does adapt and thus will charge slower.

Glad this is being discussed; as my X1 is a UK model, I don't have a US wall charger.
I found some on monoprice.com, see under the Power to USB section at the bottom:
http://www.monoprice.com/products/subdepartment.asp?c_id=103&cp_id=10311
They have 3 varieties:
High-Speed WALL Power to USB Female Converter (1000mah) - Black
High-Speed WALL Power to USB Female Converter (1000mah) - White
[**cant tell a discernable difference between those two, but one is larger...**]
WALL Power to USB Female CHARGER Converter - Black (500mah)
[**many people complaining about this not charging their devices; either it really does suck or they didnt get one with enough output**]
I WONT kill the phone picking up a 1000mah?
Anyone else in my situation needing a new US charger, this site has great prices on this stuff... these adapters are under 2 bucks, and USB cables are super-cheap too!

Charging voltage and current for X1i?

Hi.
What is a correct voltage to charge Xperia's battery?
Is it 4.3V, 4.6V, 4.7V or 5V?
I took my Xperia from some cheap shop with no original wall charger and I'm not sure the original USB cable doesn't decrease the USB 5V to something less.
Also what is the maximum current I can use for charging? Can I use a custom made power supply with 1A or 1.5A? That would be much faster for 1500mAh Xperia's battery...
Thanks in advance.

miniUSB is always 5volts
but with all such things
it works with +-20%
and yes you can use different levels of amps
which is also why the wall charger charge much faster
then having it charge over usb

2Rudegar
Thanks.
I just now discovered the battery is actually 3.6V 1500mAh and not 4.6V as I thought earlier. That means the X1 has internal voltage regulation circuit to downgrade USB or the wall charger's 5V to 3.6V.
What I was afraid of the original USB cable has internal 5V-to-3.6V regulator. But as far as I can see the only things it has are two ferrite blocks.
I believe now I can supply 5V 1A (up to 1.5A) to Xperia without risking to ruin tho phone. Better add a diode to further protect the unit...

Stock SE charger is 5v 700mah.
USB from PC supplies 100ma. This is why USB from PC takes forever to charge if phone is not off or in standby.

Do mind that it's generally better for a battery if you charge it slowly.

Ok, I do understand the idea of slow charge is better vs the fast one.
I'm going to build a permanent car charger unit with about 4.7-5.0V 500-600mA.
Thanks to everyone.

Almost all cellular phones/PDAs have an internal charge (including the xperia) circuit that does all that is needed for the battery to safely recharge, for the newer the battery technology the charger circuit is more complex.
Also, the internal circuit "sets" the battery current charge according the actual level of remaining charge, while the battery is almost completely discharged, the circuit (hence the phone) ask for more current to the power supply.
My xperia charger is rated 5V, 1A, maximum allowed current for a computer USB port is 500mA (total for all available ports), most computers do monitor (if at all) the total current of usb ports, thus if you have only the xperia connected, the computer most likely will supply up to 500mA to it, only expensive mother boards tend to have a better current control for usb ports.
Stick closer to the 5V required, normally, once you exceed the current needs of the PDA -in terms of charger power availabilty-, all that exceeding current availability will be left unused -if everything's ok with the phone and the battery.

Not cheap, but this is what I'm going to fit to my motorbike
http://www.mobilefun.co.uk/product/17362.htm

[Q] cheap battery questions

Hello,
i ve been searching for a way to extend the autonomy on the a501.
do you think i can use a cheap 12V lithium battery to charge it or take over when the internal battery is depleted ?
i m not very knowledgeable in electronics, i wouldnt want to damage the internal battery.
there seem to be very few commercial products that would fit this tablet and i m not really interested. i dont have 50$ for a +2h battery life --;
i was thinking of buying a 12V 5000mAh something battery from china and solder the appropriate DC connector on it, but im wondering if there are issues like, the Current needs to be stable at 1,5A or i might reduce the internal battery durability, things like that.
can anyone answer that ?

It's more complicated than that. The power supply probably has a circuit to regulate the flow of energy to the tablet, perhaps the tablet itself also has a circuit that works together, I don't know.
Short answer: buy a second power adapter

There are backup battery/chargers. Scosche goBAT for example.
Just Google around to find the best fit for you.

GullyFoyle said:
There are backup battery/chargers. Scosche goBAT for example.
Just Google around to find the best fit for you.
Click to expand...
Click to collapse
How would that work? Does the goBAT include a charging tip compatible with the A500?

Hello,
thanks for dropping by
its not helping really this is bs
power cat you say "probably" regulates the current. yes that is what i wrote that is what i hoped someone would clear up for me. i dont see how buying another wall charger is going to help me extend the tablet autonomy i would just as well carry the original one around.
gullyfoyle same sideways reading of the OP i would not pay 80$ for a marketed battery/charger.
i hope there are still people out there who can give an educated answer :/
this guy for example http://www.youtube.com/watch?v=LqxhEkDGkbg he says he learned it the hard way (bricked his phone?) because he put 4x(1.5V?) batteries to charge his iphone without the resistors (to get the voltage from 6V down to 5V?)
so there again, can there be issues with the discharge current rate or is it something about lithium batteries behaving differently from alkaline ones ?
i think i ll go ahead and try anyway. worst case scenario the battery will just sit there not putting out anything.

Why wouldn't you pay $80 for a backup battery charger. It was just an example. I'm sure you can find one cheaper after Black Friday, or even with a bit of Googlefu.
We aren't talking about normal chargers but portable charge devices.
http://www.scosche.com/consumer-tech/product/2073
For anyone in need of extra power, the goBAT II provides an innovative solution to the dreaded ‘low battery’ warning. The goBAT II is a powerful backup battery and dual port charger for your mobile devices. The internal 5000mAh ion battery will keep your devices going long after they normally would.
Advantages and Applications
A drained iPhone 4 can be charged 2.6 times with a fully charged goBAT II. An iPad can be charged up to 55% of full charge. This is the ideal battery for long commutes, airport travel and camping.
The goBAT II provides 2 USB charging ports that can be used at the same time. A 2.1 Amp port gives you the ability to charge mobile devices including tablets (iPad and Samsung Galaxy Tab). An additional 1.0 Amp port lets you charge your additional devices (iPhone, iPod, etc.).
Click to expand...
Click to collapse
Remember this is JUST AN EXAMPLE. The idea is to show these devices exist and are available for purchase.
http://www.engadget.com/2011/02/23/scosches-gobat-ii-portable-battery-pack-handles-two-usb-devices/
We'll just keep it real simple for you: the object you're looking at above is the Revive II charger, but slimmer, and with a rechargeable battery pack thrown in rather than a wall / cigarette adapter. Got it? Good. The goBAT II contains a 5000mAh rechargeable lithium ion battery, and it offers a pair of USB ports for charging. One's a 10-watt (2.1 Amp) port capable of handling high-maintenance devices like Apple's iPad, while the other is a more conventional 5-watt (1 Amp) socket. Scosche is also throwing in a USB adapter for the Galaxy Tab, theoretically letting those with divided households charge both an iOS and Android tablet at the same time. Brain melting, we know. It also works with the company's Revive charging app, which indicates how long a device will take to charge on any of Scosche's chargers and can also be configured to send an email notification once a device has been fully charged. She's all yours down at the source link for $89.99
Click to expand...
Click to collapse
See, others deem it "BRAIN MELTING".
And the cost of that type of thrill is reasonable, for the job it does.
But I can understand how someone would encourage another person to experiment with the guts of electronics they don't fully understand. Screw it up and you can always buy a new one.
Then again, you could buy three or four Gobats and save all the fuss and bother.

mr.bryce said:
Hello,
thanks for dropping by
its not helping really this is bs
power cat you say "probably" regulates the current. yes that is what i wrote that is what i hoped someone would clear up for me. i dont see how buying another wall charger is going to help me extend the tablet autonomy i would just as well carry the original one around.
gullyfoyle same sideways reading of the OP i would not pay 80$ for a marketed battery/charger.
i hope there are still people out there who can give an educated answer :/
this guy for example http://www.youtube.com/watch?v=LqxhEkDGkbg he says he learned it the hard way (bricked his phone?) because he put 4x(1.5V?) batteries to charge his iphone without the resistors (to get the voltage from 6V down to 5V?)
so there again, can there be issues with the discharge current rate or is it something about lithium batteries behaving differently from alkaline ones ?
i think i ll go ahead and try anyway. worst case scenario the battery will just sit there not putting out anything.
Click to expand...
Click to collapse
You will break your tablet.
The charger contains a complex integrated circuit. Sticking on a few resistors isn't gonna do ****.
Look at this for example, a simple wind generator has a complex charging circuit to regulare all the power:
http://www.instructables.com/id/How...nd-turbine/step8/Build-the-charge-controller/
Just google "how to make a charge controller" it's really not as simple as you think.
Quote from the site:
The general principal behind the controller is that it monitors the voltage of the battery(s) in your system and either sends power from the turbine into the batteries to recharge them, or dumps the power from the turbine into a secondary load if the batteries are fully charged (to prevent over-charging and destroying the batteries).

ok thanks ^^
now i understand that part
Short answer: buy a second power adapter
Click to expand...
Click to collapse
you are saying the overcharge controller (and other safety features) are all in the wall charger and are not integrated in the tablet.
so if i really really wanted to try i could plug any battery between 12 and 24V to this little guy couldnt i ?
http://www.ebay.ca/itm/220826123824#ht_3149wt_1163

As far as I know...as long as the voltage is correct (eg 12 volts) and the power adapter can produce the required amperage (1.5A) then the tablet will only take the current it can use.
So even if the power adapter is capable of producing 10A say, it doesn't mean it's forcing the 10A onto whatever is connected to it. If you use 1.5A (and if there was a way to connect multiple devices to it) you would still have 8.5A of current you could still take.
Oh the charge regulator would not be in the power adapter, that would be a very stupid design. It would be in the tablet it self to regulate how much charge it requires. I don't know of any power adapter that takes feedback from what it's charging to regulate the current.
It's the same with laptops, that's why you can buy universal laptop chargers when the one you have breaks, you just need to make sure it can supply enough amperage to power your device.
The power adapter is just a simple device that converts 110-240v 50/60hz voltage to 12v and upto whatever amperage it is designed for.
Power plugs in the house are designed at 110-240v to a maximum of 2400W (so ~20a for 110v and 10a for 240v) do you think whatever you plug into it uses up 2400W of electricity at once? No, it just takes what it is required (amperage), that's why you can plug a power strip with like 2-10 additional plugs without any problems unless if try to take more than 2400W in total.
Basic high school physics should of taught people this.

first sensible answer i get thank you daemos i m just not gonna take any chances considering the lithium technology and the fact they could use a "stupid design" for shorter gadget lifespan. if anyone has ever modded a car charger i d love to read about it.

mr.bryce said:
first sensible answer i get thank you daemos i m just not gonna take any chances considering the lithium technology and the fact they could use a "stupid design" for shorter gadget lifespan. if anyone has ever modded a car charger i d love to read about it.
Click to expand...
Click to collapse
Lithium ion batteries must be charged at a very specific voltage. So all charging regulation mechanisms would need to be inside the tablet.
I'm pretty sure the ones inside the tablet are definately below 12V so anyone thinking that the AC adapter has any fancy mechanisms to detect feedback, and regulate charge and control the voltage given to the Li-ion cells is incorrect.

Is it safe to use one of THESE to charge or run the tablet?
They also have a 6800mAh ver.

WOW YOU MEN Complicate everything
SIMPLE EASY .. Look at the output voltage of the the power brick for the iconia.. the part that you plug into the wall..
got something that OUTPUTS 12V AT 1.5 AMPS and you are done.. the Li Batteries as in all LI BATTERIES HAVE THERE OWN charging regulators in them.
The reason for this is because if a Battery is drained to a low state it will GET HOT AND OVERHEAT.. NI-CD Batteries can take and handle this heat.. Li batteries become a mini bomb at these temps.. So the are self regulating.. This can be proven by getting a cordless drill hold the shaft from running.. the drill will heat up the battery the device will STOP FUNCTIONING.. Remove the battery and put it back in . it will work again..
Now with that said.. most Li devices say make sure you have 20% or more battery life before flashing and so on.. This is because the DEVICE WILL NOT RUN On the power port. the port only connects to the battery. and in some cases the display lighting.. My cell is this way. if i run the battery until its dead or using gps on it. it will drain the battery faster then it can charge . causing it to not work until you charge it for 5 minutes or so.. this would assume that using a external battery to charge it .. the external batteries themselves would need to be more then 12 volts and atleast double the amps.. then regulated to the 12v 1.5 amps . think of this like pooring water thru a funnel.. to maintain the 12v 1.5 amps. You can test my theory by taking the battery out of your cell phone and trying to run it just on the power adaptor only.. I KNOW MINE WILL NOT RUN.. however if it has older battery technology it will..

[Q] connectiong external battery directly to internal one.

Is it possible/safe to connect an external battery of same voltage but different mAh directly to the internal battery of a tablet to raise its mAh?
I am thinking about moding a tablet case to have a built in battery pack for my Iconia a500 tablet. I can easily squeeze 4 cell phone batteries in between the folds and make two 3.6v 3000mAh(or higher) battery pack with out adding much bulk or weight to it. can probably squeeze a usb hub in there too while i am at it.
I looked at the internal battery and it looks like i can splice its wires and add a connector to hook to the two 3.6v packs for easy connection.
I don't know much about electronics, but from my limited knowledge and layman point of view, as far as the tablet is concerns, it will just have a higher capacity battery, wont it?
can it be done safely without any other electronic components?

I'm not expert in that matter, but I think there's LiIon battery, and AFAIK it may make some confusement to your Fuel Gauge IC and Battery Charging IC, as these are probably calibrated to work with that certain battery type and capacitance. But I don't believe it may damage something if you connect it paralelly.

I would be careful with that if I were you. While it seems simple enough, batteries are much more complex than just voltage and capacity.
Most of the time, external batteries just go through the charging connection of the device so it can handle the power itself. If you connect it directly, you may bypass some part of the charging circuit (often times there's a circuit in the battery itself). Basically, I'm thinking the batteries may not fully charge or one will overcharge. It really depends on how it's set up. I'm not an expert with the design of rechargeable batteries though, so it may be safe.
In short, I would suggest connecting the batteries to the charger to extend your battery life. I'm sure others can offer additional insight.

A good read about batteries: http://batteryuniversity.com/learn/article/serial_and_parallel_battery_configurations
I can't comment on if it will work or if it is safe..

cellphone batteries have a built in protection to prevent them from overcharging or discharging, don't they?
The problem i have with connecting to the charging port is that it needs 12v. connecting 3 or 4 of battereis will give me either too little or too much volt. cant get 12v out of 3.7v batteries with out some kind of additional electronic parts to regulate the voltage. I don't have the sufficient knowledge to do that. this is why i figured ill do it directly. And charging would be simpler too if i can use the charger to charge both the internal and the external batteries at the same time.
Was hopping to hear from someone who did that already. I guess no one is brave/dumb enough to try it.

Sounds intresting looking forward for it

In a "perfect" environment this would be possible.
The inner resistance and voltage difference of the different batteries would even out the different capacity while charging.
You can avoid having these currents between the batteries by using diodes to separate the charging currents.
However my recommendations in terms of reliability, safety and efficiency is to use two or more batteries with the same capacity and dis-/charging curve.

is it the phone or the battery that cuts current when the battery is fully charged?

ridethisbike said:
is it the phone or the battery that cuts current when the battery is fully charged?
Click to expand...
Click to collapse
On most phones tablets etc. it's the device that cuts off the charging current when the battery is fully charged.
However nearly ever batteries has also a protection circuit that cuts off the battery in case of
under, over voltage and over current, sometimes even over temperature.

samotronta05 said:
On most phones tablets etc. it's the device that cuts off the charging current when the battery is fully charged.
However nearly ever batteries has also a protection circuit that cuts off the battery in case of
under, over voltage and over current, sometimes even over temperature.
Click to expand...
Click to collapse
ah, well it seems to me that if the battery has to take action, then you're doing it wrong.
I'm not sure exactly how diodes work so I can't comment on that, but definitely use like batteries (two 3000mAh batteries as opposed to one 3000mAh and one 3600mAh) as to not confuse the device about the charge, causing the 3600 to not get fully charged. just make sure they get connected properly (in parallel) and it should work just fine.
in reality its no different than someone using 4 car batteries to power their car audio system. as long as its done properly (in parallel), there is really no harm.

I wouldn't recommend it. While technically it is something that you can do like other posters have said the internal power system is configured in a particular matter. It is likely that the regulation and protection are minimal if they only expect the internal battery. There is also the issue of charging, if you did as you say, you would be discharging the batteries into each other if they weren't exactly at the same levels. So this isn't the recommend method.
What I would recommend you do is put them together so you get something over six volts (two 3.6V packs in series) and put a 5V regulator on it. Then connect it to a USB cable and charge through there. That way you utilize the systems built in protection, aren't messing with the battery connections and can swap it in much easier.

You can... as far as u meet these requirements.
1) notice ur original battery voltage..
2) buy some same kind of them, or u may use others, provided the voltage is same. If u can find higher watt-hour( current) battery of same voltage, go for it.
3) never mix up different amp/ voltage rated batteries together. Ie if u have 3.7v 3200ma batt, and planning to add one more batt in parallel to it go for another 3.7v 3200ma , and not 3.7v 1500ma or 3.5 v 3200ma batt.
4) if u cant find a higher capacity batt of same voltage, go for parallels. Ie join together the positives of two or more batt, and also join together their negatives too.. connect it to the batt terminals of tab,
5) no problems will be caused if u use high current batt, provided u have suited the correct voltage. In ur case u have to ensure proper voltage only. And current can increase to any value.. the system takes only what its needed.
6) the sad thing is it will take more time for charging. But never try to increase the charging current. It will damage the power section. But increase ur patients. Most of the tabs got 1-1.5 amp charger. Never increase the limits.
U may go for it. If u can manage these...
Sent from my HD2 using XDA App

giritrobbins said:
I would recommend it. While technically it is something that you can do like other posters have said the internal power system is configured in a particular matter.
Click to expand...
Click to collapse
Yes, to charge with a constant current until a certain voltage is reached.
giritrobbins said:
There is also the issue of charging, if you did as you say, you would be discharging the batteries into each other if they weren't exactly at the same levels.
Click to expand...
Click to collapse
Yes, this is the main problem and it's also the reason i recommended using two batteries with the same capacity. Otherwise the constant charge and discharge depending on the size of the difference between the batteries makes the system very inefficient.
giritrobbins said:
What I would recommend you do is put them together so you get something over six volts (two 3.6V packs in series) and put a 5V regulator on it. Then connect it to a USB cable and charge through there. That way you utilize the systems built in protection, aren't messing with the battery connections and can swap it in much easier.
Click to expand...
Click to collapse
Which would make it even more inefficient.
showlyshah said:
3) never mix up different amp/ voltage rated batteries together. Ie if u have 3.7v 3200ma batt, and planning to add one more batt in parallel to it go for another 3.7v 3200ma , and not 3.7v 1500ma or 3.5 v 3200ma batt.
Click to expand...
Click to collapse
You can mix up different batteries when the voltage is the same, however this is not a the recommend way, since you will not encounter much gain in capacity.
The in terms of capacity smaller battery will be charged by the bigger one all the time.
However if you say i don't care about the efficiency then you can mix up for e.g. a 3.7v 3200mAh and a 3.7v 3000mAh battery.

samotronta05 said:
Yes, to charge with a constant current until a certain voltage is reached.
Yes, this is the main problem and it's also the reason i recommended using two batteries with the same capacity. Otherwise the constant charge and discharge depending on the size of the difference between the batteries makes the system very inefficient.
Which would make it even more inefficient.
You can mix up different batteries when the voltage is the same, however this is not a the recommend way, since you will not encounter much gain in capacity.
The in terms of capacity smaller battery will be charged by the bigger one all the time.
However if you say i don't care about the efficiency then you can mix up for e.g. a 3.7v 3200mAh and a 3.7v 3000mAh battery.
Click to expand...
Click to collapse
The issue when you connect them like that will always occur when they are in parallel (you need to add some logic or some diodes in there). Using the same ampacity battery will mitigate it to a point but the internal resistance of a battery will dictate how fast it drains down.
As for the charging, that isn't what i am saying. The internal circuitry that he cannot change is expecting a certain battery with certain characteristics. Putting a second battery in there in parallel will potentially mess with that stuff. If it doesn't realize the size of all the attached battery it will register a fault because it won't be charging correctly.
He isn't going for efficiency here. And a linear regulator is easy, if we want efficient we can do that too. I was just suggesting an alternative that could be easily done.
And the most important point is not about voltages but about chemistry. Different chemistry have different voltages and different knees where they drop suddenly.

The original battery is 7.4v 3350mah. and the charger is 12v 1.5a.
so matching or passing that with batteries I can fit in the space I want it to fit in is a problem.
I was going to use 4 i9000 1500mah batteries, which would fit perfectly, to make a 7.4v 3000mha. but that would be lower then the original. i guess i can try to find higher capacity batteries that i can fit in the case
But if i understand it correctly, the current will keep flowing from the larger capacity battery to the lower one, it will keep them at 100% until the original will drop to lets say 3000mah and then they will all drain at the same rate until they are all empty. and when i charge them, the charging circuitry will get its information only from the original battery, so it will keep charging until the original is full. it may not be as efficient, but it should still get me a significant boost, wouldn't it.
I suppose I could connect them all to make a 14.8v 1500mha with a 12v regulator and use the charging port, but that will leave me with the problem of charging the external pack. no idea how to do that. how do i cheaply and safely charge a 14.8v battery pack?

ronkoni said:
The original battery is 7.4v 3350mah. and the charger is 12v 1.5a.
so matching or passing that with batteries I can fit in the space I want it to fit in is a problem.
I was going to use 4 i9000 1500mah batteries, which would fit perfectly, to make a 7.4v 3000mha. but that would be lower then the original. i guess i can try to find higher capacity batteries that i can fit in the case
But if i understand it correctly, the current will keep flowing from the larger capacity battery to the lower one, it will keep them at 100% until the original will drop to lets say 3000mah and then they will all drain at the same rate until they are all empty. and when i charge them, the charging circuitry will get its information only from the original battery, so it will keep charging until the original is full. it may not be as efficient, but it should still get me a significant boost, wouldn't it.
I suppose I could connect them all to make a 14.8v 1500mha with a 12v regulator and use the charging port, but that will leave me with the problem of charging the external pack. no idea how to do that. how do i cheaply and safely charge a 14.8v battery pack?
Click to expand...
Click to collapse
Hey why are u going to make a 14.8v batt pack when urz original ones are 7.4??? I dont realy understand the logic. If u have extra batt, then make the pack like this
Batt pack of 7.4v × 2 and connect them in parallel, thatz all, no need to modify charging circuits, no need to regulate the voltage, and no loss in voltage/ current,
But if u make a high voltage pack, u have to regulate the o/p with some ic, and in turn u will suffer some v/c drop.
Sent from my HD2 using XDA App

i like to connect directly to the battery, but some seem to believe it is not wise if the mAh of the original is higher then the external pack.
The 14.8v pack with a 12v regulator option is for use with the tablet's charging connector which require 12v . A safer option, but leaves me with the charging problem.

ronkoni said:
i like to connect directly to the battery, but some seem to believe it is not wise if the mAh of the original is higher then the external pack.
The 14.8v pack with a 12v regulator option is for use with the tablet's charging connector which require 12v . A safer option, but leaves me with the charging problem.
Click to expand...
Click to collapse
http://www.ebay.com/itm/USB-2-0-fem...ultDomain_0&hash=item3f0cd836f3#ht_2792wt_902
that actually took me a lot longer to find than I had originally planned... lol. of course.... you're going to have to find the rest of your charger. but that'll be easy with that adapter

So its a about making a batt pack which u can connect to the tab via charging port? And use it like a backup when u r out of power?
If its ur idea, you may tell about the size of the pack, and how long u need to use it( ie backup time), if u do, i will find out the solution, also post ur current batt and charger spec.
And hope i can help with some circuits too..
Sent from my HD2 using XDA App

the idea is to have a battery pack that can fit in between the layers of the stand part of this tablet's case. the available space I want to use is about 2"x9" so since the space is limited, the batteries must be the flat type and be able to get 12v out of them and be able to charge them externally.
this is the original tablet battery and the charger is 12v 1.5a.
4x Samsung i9000 1500mAh batteries fits perfectly. and since i already got 2 extra ones laying around, might as well go with these batteries. unless it is possible to get 12v out of 3 batteries. then i can probably use 3 Samsung note 2500mAh batteries instead.
so, what circuitry do i need to make this thing power the tablet and get charged?
thought about getting one of these battery packs, take it apart and replace its batteries with mine. since it already got the necessary circuitry for regulating the voltage and for charging, it would cut down on the guess work and probably be cheaper to build. i think they use 3 batteries in there which would be better.

5 Blinking Lights. Can't figure out what to do here....

Hey, guys and gals.
Well, I found a Nexus 7 in my car the other day and can't figure out who it belongs to. All I know is that I can't boot it up and can't charge it. All I get is 5 blinking white lights. I don't know what it means but I did some research and it seems to mean that the tablet is too dead to boot up. However, it's not accepting any charge even though I charged it overnight. All I am getting is 5 blinking lights now......before I at least got the screen turning on with an empty battery being shown. (If that makes sense)
I am not using the original charger as I don't have one and am instead using my kindle charger. Could that make a difference?
Also, there seems to be some damage around the charging port area...However, the port itself seems to be in adequate condition.
Any ideas?

If it is taking a charge it should warm up a little when it is on the charger.
No warmth == no current going in.
If the battery is so old that it is nearly dead/shorted, the tablet will get HOT when it is on the charger.
So no warmth means no battery connection, either at the USB port or at the battery connector inside the device. There are threads on here from folks who had units where the internal battery connector wasn't seated well and came loose - the teardown to that spot to seat the connector isn't too bad... search for them.
On a 2A charger it takes ~ 3-4 hrs for a 5-100% charge for a N7. That happens initially at about 1500 mA, so it is possible that the voltage on your charger simply collapses if it is only designed for say 500 MA... if that were the case no charging could occur, or only pathologically small amounts of charging could occur.
Also, the N7 has a TI charge controller chip which needs *some* small amount of juice to operate, so it is unfortunately possible for the battery voltage to get so low that the chip can't operate correctly and you get a chicken-and-egg situation where the battery can't charge, even though it is healthy - the voltage just got so low that the charging chip doesn't work. In these cases, an external charger with current limiting is needed to partly charge the tablet battery to get the voltage up high enough so it can be reconnected to the tablet and charged normally. Note that this is a 3rd scenario where you wouldn't feel any "charging warmth" even though all the connections are good.
There is a report on here of someone doing something incredibly stupid - getting some charge onto the tablet battery by disconnecting the battery connector from the tablet and directly connecting it to a car battery to charge it (That's a recipe for a battery explosion or fire). Please don't do something like that.
Something a little less stupid would be using a power resistor (e.g. 5 Watt, 30 ohms) in series with the car battery to prevent too much current from flowing. That would be safe even if the tablet battery was a dead short ( 413 mA, 5.1 Watts in the resistor ), and if the tablet battery was healthy-ish, it would trickle charge at ~ (12.4-3.0)/30 = 313 mA with 3 W dissipated in the resistor.
The important point here is that wall-wart USB chargers are designed to produce 5V up to a certain current level, but they don't actually control the amount of current; that's the job of the funky chicken-and-egg TI charging chip in the N7. So you can't just hook a 5v supply directly to the tablet battery - as you have removed the current limiting control you need something to replace that function: either something dumb to limit the current (such as a power resistor), or a slightly more advanced charger that allows you to limit the current output to a moderate maximum rate.
Note also you don't need to fully charge the battery this way; you just need to bring the charge up a few percent so it can be reconnected to the tablet and charged the "ordinary" way.
good luck

bostonbeast225 said:
Well, I found a Nexus 7 in my car the other day and can't figure out who it belongs to.
Click to expand...
Click to collapse
Really? [emoji15][emoji41][emoji56]

bluebirch said:
Really? [emoji15][emoji41][emoji56]
Click to expand...
Click to collapse
OP could be a cab or uber driver or something like that

Did u ever get this sorted