How to load test lithium battery

[fsoender]

Hi,

I was wondering if you guys have a way to load test a 29.6v / 10A lithium battery pack to 10A?

Would a multimeter and a 2.96 Ohm / 296 W resistor work?

 

[KlausST]

Hi,

First I'd contact the datasheet. Jusg to be sure where the limits of the battery are.
Safte first. Avoid explosion.

Then for sure you could use a 2.96 Ohms resistor, if you find one.

I'd try a constant current circuit. 10A...or adjustable.

Mosfet, simple circuit. Easy heatsink mounting. Maybe additional fan for smaller heatsink.

If you need more/better help, then you should give detailed informations.

Klaus

 

[fsoender]

Klaus,

That sounds good. Yes, the battery can handle it, its multiples in a series-parallel pack.
I can drop the voltage to about 24 V, and use this resistor I found on the net?

2.4 ohm - 400w Milwaukee 26-136 Ribwound, 1-5/8" x 8-1/2" $49.00

- - - Updated - - -

Hi,

First I'd contact the datasheet. Jusg to be sure where the limits of the battery are.
Safte first. Avoid explosion.

Then for sure you could use a 2.96 Ohms resistor, if you find one.

I'd try a constant current circuit. 10A...or adjustable.

Mosfet, simple circuit. Easy heatsink mounting. Maybe additional fan for smaller heatsink.

If you need more/better help, then you should give detailed informations.

Klaus

Would it be better to use a MOSFET? How easy is that done?

 

[Audioguru]

You also need a circuit to detect "low battery" when a cell voltage has dropped to 3.2V then it disconnects the load. If you discharge a cell to below about 3.2V then it is permanently ruined and might catch on fire if you try to recharge it.

 

[fsoender]

You also need a circuit to detect "low battery" when a cell voltage has dropped to 3.2V then it disconnects the load. If you discharge a cell to below about 3.2V then it is permanently ruined and might catch on fire if you try to recharge it.

I just want to load test for a few second

 

[Audioguru]

I just want to load test for a few second

But the voltage of a fully charged Lithium cell drops in the first 30 seconds of a heavy load then it levels off. Usually the power of a cell is measured and recorded at 30 seconds.

 

[fsoender]

But the voltage of a fully charged Lithium cell drops in the first 30 seconds of a heavy load then it levels off. Usually the power of a cell is measured and recorded at 30 seconds.

OK, so I found this site: http://denishennessy.com/2012/04/08/measuring-battery-capacity-with-an-arduino/

Can I replace the resistor with the high watt I found and use this project and reduce the volt to the Arduino?

 

[Audioguru]

The Arduino was testing alkaline batteries that are completely different to Lithium batteries.

 

[fsoender]

The Arduino was testing alkaline batteries that are completely different to Lithium batteries.

Well I know that, heard about modification?

 

[Audioguru]

Well I know that, heard about modification?

Yes, to prevent an explosion and a very hot fire you must limit the discharge current and shut it off when each cell's voltage drops below 3.2V.
The capacity of the Lithium battery cells are not exactly the same so the one with the lowest capacity will reach 3.2V and drop lower first. Therefore the voltage of each series cell or group of parallel cells must be separately monitored.

 

[c_mitra]

Just like the battery pack in your laptop, each individual cell has to be monitored for good health. Series parallel combination brings in additional difficulties (one fellow may driver another fellow that has fallen sick on the way). Some cells come with individual electronics (mounted on the bottom- negative terminal: these cells are longer by about 1mm) that prevent overcharging or deep discharge.