Hi John,

The subject was discussed here and here.

Thor

NiCd batteries are still widely available. Batteriesplus have tagged 2400 ma NiCds for just over £2 each for 10 (gives you 12 volts.) The snag with NiMh batteries is that they have less current output than NiCds so they are not ideal for things like battery drills. You will get less torque with NiMh batteries.

As far as charging NiMh batteries with a NiCd charger, it will work, but take a much longer charging time.

Andrew.

Edited By Andrew Tinsley on 24/06/2021 13:10:55

Will there be a big bang and magic smoke? No.

Will the battery recharge? Probably.

Is it a good idea? No. In the good old days batteries and chargers were both dimwitted so battery management was either done manually by professionals, or no-one bothered. Managed batteries have much longer lives and better performance than unmanaged batteries because the latter degrade. Big difference between:

• 20th century Lead Acid submarine batteries where engineers constantly controlled charge and discharge rates, monitored cell chemistry and checked the condition of the plates, and,
• Motorist charging a Lead Acid car-battery with a cheap charger. Car batteries are easily spoiled and there's a rich sub-culture of battery bodges to extend their lives a bit. Revived batteries are unreliable compared with batteries in good condition, OK to revive batteries yourself, but if you buy one you've been ripped off.

Modern batteries are likely to come with a built-in management system. The management system can be in the battery, in the charger, or both. What happens if the battery and charger are mismatched is anyone's guess. Expensive batteries and their chargers are often intelligent enough to refuse to charge unless they specifically recognise each other. Slightly less sophisticated systems rely on the battery telling the charger to maximise battery life by varying volts and current throughout the recharge cycle; the charge is optimised. Others simply limit charge time, rely on constant current, or have an overheating sensor. The customer doesn't know: he buys an appliance with a particular battery and a particular charger and is meant to replace them with compatible parts, not to mix and match.

Is it a bad idea? Maybe not. If the battery charges the result is unlikely to be outright failure. More likely, the battery won't quite be fully charged, and/or the number of recharge cycles it takes before clapping out will be much reduced: a battery that should last 1000 cycles, might only do 500 or less from the wrong charger. That may not matter!

However, if reliability is important, I'd try to find the right battery for the drill. Anything wrong with these?

Dave

I've had problems with sophisticated chargers undercharging due to getting NiMH and Nicad mixed up.

Nicad have a voltage drop, where with NImH the voltage rise slows down (as I recall) so NIMH chargers can undercharge nicads and nicad chargers can overcharge NiMH (as I recall) I may have this slightly wrong

Trickle chargers at 1/10 C for 14 hours (i.e. 200mA for 2Ah etc.) will be fine for either chemistry.

Neil

I think you are thinking of Lion batteries.

NiMH are the safest of the common rechargeables, without the toxicity of lead acid or Nicad and they don't burn l;ike Lion.

Neil

Yes Neil, you’re right.
Sorry for the false concern, I don’t have direct experience with NiMH 🤪

Cheers Will

Lion = Lithium-ion (not iron although some formulations use iron in them) is a catch-all for all lithium batteries including Lipo.

en.wikipedia.org/wiki/Lithium-ion_battery#Fire_hazard

(Edit) I guess you thought I meant lithium-iron-phsphate (Life) cells – these are indeed much less likely to catch fire if abused.

Neil

Edited By Neil Wyatt on 27/06/2021 13:32:21