My tablet battery has swollen up so might spontaneously combust. It is 3.7v Lithium Polymer 2588158 with 4100mah and 3 wires. When I measure the charge current at the 5v usb port it is only 870mA so about 0.29C.

I cannot find for sale a similar 3 wire battery that is thin enough to fit in the tablet. I can only find 2 wire or 6 wire batteries.
like this:

2 WIRE

https://www.amazon.com/4000mAh-2890...HDH4P/ref=psdc_10112773011_t3_B07MXV8C6Q?th=1

6 WIRE

https://www.amazon.co.uk/Trconelect...ords=asus+nexus+battery&qid=1597855373&sr=8-4

I presume the original battery relies on the tablet's own charging circuitry which monitors a thermistor in the battery via the third wire for safely charging.

Q.1 The 2 wire replacement battery has a small control circuit inside the battery but no thermisor wire for the tablet charging controller. Is it safe to charge a 2 wire battery without connecting a thermistor sensor to the tablet charging circuit? I mean to ask, do all 2 wire batteries internal control circuits prevent dangerous conditions when charing with just 2 wires? Does the 2 wire battery have an onboard thermistor which is monitored by it's internal control board instead of the tablet charging controller?

Q.2 How could I get the 6 wire battery to work?

(with the 2 wire battery I could trick the tablet charging controller to be always on by connecting the thermistor sensing wire to ground via fixed resistor. This will only be safe if the 2 wire battery is able to control the safe charging by itself hence my question). How are 2 wire batteries afe if they have no third wire?

 

The White wire is usually a Temperature sensor, this is connected to Negative terminal. You could replace it with a two wire one and use the thermistor from the old battery, .

Easily checked by using a DVM on Ohms and hold it in your hands to warm it up, it should change in resistance.

 

Thanks for reply.

I did think of that but how can I remove the thermistor without spontaeous combustion? Unlike the photo my battery has puffed up like a balloon.

I could buy a new thermistor from somewhere I guess and connect it. I did think of just connecting the thermistor wire to a fixed resistor and hope the 2 wire battery internal control board will take care of safety?

I have now ordered a 3 wire battery but it is only 2700mah compared with the original 4100mah.

The charging current with the original battery at the 5v USB port is 0.870A so I expect it is low enough not to overload the smaller battery.

Do you think the smaller battery will work OK? Are there any other considerations I might not know about e.g. I don't know number of cells, etc.

 

My guess is that the 6-wire battery is really a 3-wire battery, with two of each wire. I'll bet if you check you'll find 0V and 0Ω between the two red wires, and also between the two black wires, and between the two white wires.

 

Aliexpress have the correct replacement battery however shipping costs are crazy.

I doubt the Asus Nexus battery will fit, in any case its not available. The thermistor will be a standard 10kohm one but if its not integral to the pack it might as well be a 10k resistor as it won't detect thermal runaway soon enough to act in shutting the charge off.

If the integral charge/discharge control chip (BMS) in the 2-wire battery doesn't mirror the settings for the tablet's own BMS you may find it won't charge properly/fully, or the internal protection may shut down unexpectedly during discharge on peak demand that the tablet's own BMS would find acceptable.

The original battery is charged at 0.2C, the smaller one will charge at 0.32C, but equally will be discharging at a higher C-rate. It will have a shorter life as a result.

The Onyx Book Note 2 is quite old, how long have you had it?