Discharge Rates For NiMH Cells

[10gauge]

Does anyone know what the discharge rates are for the various Intellect NiMH cells - IB1400, IB3600, IB4200, and the new IB4600?
I think the IB4200s put out about 35 Ah, but not sure about the other cell types.

[G Doggett]

Not sure what you mean by discharge rates.
The model number denotes the batteries rated capacity.
An IB4200 is rated at 4200 milliamp/hours, which is 4.2 amps for 1 hour.
If you increase the amp draw to say 42 amps(times 10) the time reduces proportionally to around 6 miutes( divide by 10 ).
Hope this is what you meant.
Graham.

[10gauge]

Sorry, what I mean is the maximum current that a certain type of NiMH cell can discharge or supply. Just like there is the "C" rating on LiPos, I am curious what are the current limits on NiMH cells.

[Fluid]

It is possible to draw over 300 amps from some IB4200 cells - I've data logged that much for a second or so. In SAW applications 150+ is not uncommon for 4 to 8 seconds at a time. An average of 50-70 amps is pretty safe for ~2 minutes, although if the cells get over 150F their life will be shortened. More than 70 amps works for short periods, a lot depends on how you run and how many high-amp accelerations you make as to cell temperature.

The main factor is cell temperature, keep it below 150F and the cells will last longer. Each time the cells vent (usually over 150F) they lose capacity and performance. Enough venting cycles and the cells are junk.


.

[FE_Chris]

Fluids got it!!!! You can suck on the nimhs till they get hot, and then they are done for that cycle IMO...Unless you wanna have that pack only last 12 runs......

Thats what I do! IMO they only have problems when you discharge to fast for to long and make the cells hot.

[10gauge]

Thanks Fluid and FE Chris! I didn't know that IB4200s were capable of such a high current draw. I'll keep an eye on the temps too.

I guess I should get an inline meter to measure the current loads for the future. I am also trying to get an idea on the IB1400s to use in a micro cat. I am planning to use an 8-cell IB1400 pack with an Ammo 28-45-3600kv motor rated at 40 Amps max. I'll start off with an x427. I wonder if it's possible to draw draw 30 Amps for 1 minute on IB1400s? If not, I'll probably go with the Neu 3S 30/60C 1800mAh LiPo Pack...

Thanks!

[FE_Chris]

The older eagle tree V2's should be able to be found CHEAP. If your not using all kinds of amps, thats a nice inexpensive data logger.

To be honest I do not know actually how many amps the nimh cells will handle, Actually I bet most people don't cause I have asked myself and no one had a definitive answer. Everyone just uses them for anything 4-40+ cells anyway. Thats what we got if you don't wanna run lipo. It's just I know from experiance, the easier you are on them the longer they will last. You can still run the crap out of them! Just take care of them and know the damage limits. Thats the best advice I have picked up myself when it comes to any batterys. Same with lipos. Worse with lipos maybe cause you can have a fire a lot easier!!!!!

[10gauge]

Thanks, I think getting the Eagle Tree v2 Logger seems like the next logical step for proper diagnostics since I am investing more time and money into the hobby....
Ah, how nice it would be to have an outboard module on our radios to relay live telemetry for rpm, Amps, Volts, temperature, speed... I digress!