Nicad vs Nimh

cjfox · Feb 11, 2009

I have an old nicad video light battery pack, the batteries need replacing, and I would like to replace them with NiMh, will the old charger work with NiMh? the charger model is BCW-310-140-01-00N.
Thanks

DA Aquamaster · Feb 11, 2009

At the most basic level, all you really need is the proper voltage and it will ball park work. Of course it will not be what you would call a smart charger, and you would have to monitor the charge and remove the battery when the voltage peaks. It is a lot easier and not too much more expensive to just get a charger designed to work with NiMH batteries.

But the charger is probably not your biggest problem. If the power drain is too high, NiMH batteries may not be the way to go and you may be better off with nicads. If it is a halogen light, it may drawn more current than an NiMH pack can support as they tend to be designed for much lower drain electronic applications.

cjfox · Feb 12, 2009

I am aware of that, but I can't find what the apprpriate discharge rate should be. I'm currently drawing 8 amps from a 5ah nicad pack, and I would like to switch to 11ah nimh, same draw.

DA Aquamaster · Feb 12, 2009

It depends on the pack, but even the best available AA cell based packs will only support 6-7 amps. A new style NiMH cell - the HeCell is supposed to allow a higher discharge rate.

The other issue with NiMH batteries is that they self discharge around 2% per day, so figure 40-60% total discharge per month.

If it were me, I'd stay with nicads a while longer.

spoolin01 · Feb 13, 2009

DA Aquamaster:
At the most basic level, all you really need is the proper voltage and it will ball park work. Of course it will not be what you would call a smart charger, and you would have to monitor the charge and remove the battery when the voltage peaks. It is a lot easier and not too much more expensive to just get a charger designed to work with NiMH batteries.

But the charger is probably not your biggest problem. If the power drain is too high, NiMH batteries may not be the way to go and you may be better off with nicads. If it is a halogen light, it may drawn more current than an NiMH pack can support as they tend to be designed for much lower drain electronic applications.

I was interested in the high drain comment. Can you expand on this? It runs contrary to other advice I've encountered about the load capabilities of NiMH vs NiCD, particularly at colder temps. Also, I'm trying to read between the lines, but Ikelite advises that the NiMHs will blow the oscillator circuitry in their older NiCd-engineered strobes - I assumed that had to be a current capability issue since the voltages are the same and voltage under load is fairly constant with either chemistry. My knowledge is fairly basic - that may be obvious by now - but I'm interested to understand this since it's such a practical issue.

Mike

DA Aquamaster · Feb 13, 2009

My understanding is that NiMH batteries are great in digital cameras, LED lights, etc as they offer more battery capacity and perform very well as long as the current drain is comparatively low. Large HID or halogen video lights however could draw more amps than a NiMH pack can sustain. Again, my understanding is the limit is around 6-7 amps for AA cell based packs.

Most of my battery experience comes from RC flying where the current draw can be very high and nicads still rule there in anything other than receiver packs.

I am guessing that minor differences in voltage/power curves would cause the oscillator issues.

cjfox · Feb 13, 2009

The pack I have uses 10 D cells, and I know Ikelite makes a new NiMh pack for the halogen video lights. I want to make a bigger capacity battery out of the old larger nicad pack for halogen lights.

Ikelite Staff · Feb 13, 2009

cjfox:
I have an old nicad video light battery pack, the batteries need replacing, and I would like to replace them with NiMh, will the old charger work with NiMh? the charger model is BCW-310-140-01-00N.

The older style charger you reference will not terminate the charging cycle and switch to trickle charge mode with NiMH batteries. The new #4066.1 Smart Charger is compatible with both NiMH and NiCad batteries.

Regards,
Jean / Ikelite
IKELITE Underwater Systems

Nicad vs Nimh

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