Charging Lithium Ion

[windozeuser]

I have a fairly new laptop battery (less than one year old) I bought. Then my laptop had an unfortunate accident. I want to use the battery, 10.8 Volts 3800mAh Lithium Ion laptop battery for my robot. What I want to know is how do I charge this, polarity of charge, charging voltage, charging current. Any help is greatly appreciated.

 

[Gayan Soyza]

You can use that laptop charger for that.In the charger its printed the current & voltage.
Its little bit harder to design a Li-ion charger.Li smaller capacity batteries prefer fast charge than a slower charge 1C rate.But bigger ones prefer slower charge like 0.8C rate.But continuously charging with this rate will damage your battery.( No trickle charge is applied because lithium-ion is unable to absorb overcharge)

 

[Sceadwian]

By 'unable to absorb overcharge' he means if you don't know what you're doing the pack will burst into flames.

 

[sam2]

10.8-11.1V is the nominal voltage for three cells, so you would want your charger output voltage (with no battery attatched) to be 12.6V MAX.
12.6V is a fully charged 3 cell lithium battery

.7C-1C is the max current you want ,so 2660- 3800ma.

Polarity: red +/ black -.

I have built a number of these(1-3 cell) for for myself and friends, and they work great. https://shdesigns.org/lionchg.html

Check your lap top charger to make sure that it puts out 12.6V or a little less unloaded. Some electronic devices like cell phones have the charger circuit built in and the power supply is unregulated.

Dont use any charger not designed for lithium batteries or you will have a fire.
There has been a huge number of fires (houses, garages , cars) by overcharging or charging damaged lithium batteries.
Sam

 

[Alex_rcpilot]

Or if you're interested, browse Maxim IC homepage for their Li-ion charger solutions. They offer pretty good IC's dedicated for such use.

 

[justDIY]

Linear has a good selection of lion/lipo chargers too, probably a bit more of an "up to date" catalog than maxim in that regard.

the power pack that came with your laptop IS NOT a lithium ion battery charger. It is an external bulk power supply, and the charger is built into the computer. Trying to recharge a laptop pack with a simple charger will be quite a challenge. the laptop pack is a series + parallel arrangement, along with fuel-gauge chips (columb counters), charge balancers, anti-counterfeit id, thermal sensors, over charge and discharge protection circuits, etc. even if the old laptop is destroyed to where it won't run, will it still charge the battery? that will save you much work.

 

[windozeuser]

THanks a lot for all your help

 

[sam2]

I have gutted alot of those packs and as long as the leeds are long enough after ,you are good to go. You can take them apart and put them back together in any series parallel configuration you need.

If you dont have a balancer you can charge each cell seperatly at the same time( these chargers are cheap, less than $5) and then hook them up in series.
A balancer is easy to build also.
sam