Discharging NiMH?

[dreamer_1uk]

Hi,

I was wondering, are you supposed to discharge, cycle and equalize NiMH or just leave them alone after racing?

Your thought and opinions would be greatly appreciated!

Dale :D

[NV529]

some people say that nimh don't have memory. BUT in truth they do, but not to degree as nicads. I'll equalize mine at lease every 10 runs. and I discharge them just like nicads. but you'll need to store them with some charge well in storage.

[GTpanda]

yeah, I agee with NV529, they do have memory!!! :(

afaik nimh batts must not be stored empty (discharged) like nicads like to, instead they should have a 30% of charge before storing away for the winter

in current use, you should discharge them (but not with a bulb discharger, only with en electronic one), then you can equalize the individual cells using the pack-equalizers (orion, trinity etc)

the reason for not storing empty is that the self-discharge rate is much higher than for nicads, so you risk a weak cell to go through the bottom and reverse...

[sosidge]

Equalizing is not really recommended for NiMH cells.

They don't like going down to those low voltages - risk it if you like - i equalized my old NiMH's when they were getting a bit weaker, and though the average discharge voltages improved, the batteries "died" soon afterwards.

I store mine discharged to 5.4v between meetings, with no ill effect, but if they were going to be left for more than a fortnight i'd put a part charge in them.

[dreamer_1uk]

Hi,

So, do you equalize the NiMH's or not? and why can't you use bulbs to discharge them? even with a 5.4v cut off device on them?

Dale

PS - Its putting me off getting them now if I have to pay for a digital discharger.

[highroller]

Typically all RC batteries do not perform as expected when they are first introduced. Recommended charge rates are usually incorrect and care usually changes quicker than most can be informed.

There are 2 methods of storing NiMh cells both methods have an effect on how the packs perform.
1. After use, store with whatever voltage is left in cell. Discharge before next use to 5.40 volts allow to cool and charge. This methods leads to a lose in voltage (punch) but runtime lost is minimized.
2. After use, discharge to 5.40volts with any load source, place in an equalizing tray (Trinity Real Time2, Integy, ProMatch) and remove when light on tray goes out. Allow to cool 1 1/2 to 2hours before next cycle. This method improves and lowers internal resistance (more punchy packs), but at a slightly higher lost of runtime.

NiMh cells like constant use up to 4times in a day without a lose in performance. However if packs are not used for 2 or more weeks cycle them 1-2 days before you race. Any cell that is inactive for a length of time tends to run flat cycling the pack 4days before a race for Nicads, and 2 days for NiMh seems to keep their voltage/punch constant and tends to help avoid the false peaking.

I race mostly competitively and discharge then tray my NiMh. When packs have lost runtime to the point of not making runtime in the Modified class the cells are then used for stock racing and new cells are purchased to take the place of the other packs. With the new 3300 we shouldn't have that problem, but then again we said the same thing about the 2400 and 3000 cells, but with motor, gearing and other criteria we found that at times those cells dumped before the end of a race.

[dreamer_1uk]

Hi all,

Thanks for your replies. I found the answers to my questions very interesting and very helpful.

Thanks again,

Dale