Batboard

Hello, my fire department has been looking for batteries for our minitor III's. We found a cheaper solution from Grainger, however the batteries are 1.22V and are Ni-MH, instead of the standard 1.25V Ni-CD. My question is, would this be OK? And would the chargers have any problems with them?

Thanks,
Mike

Mike: Rechargeable batteries vary somewhat in their voltage, depending on their state of charge, so don't be put off by the numbers in the catalog. A fully charged Nicad will read about 1.35 volts, and a NiMH about the same. You can charge the NiMH in the Nicad charger. You should NOT charge a Lithium Ion battery in your present chargers.

You will like the NiMH batteries compared to the Nicads.

Tom, W2NJS
...in D.C.

Be aware of the downfalls on NiMh batteries compared to NiCad type.
Pros: There is only one, Lighter weight, more capacity per ounce.

Cons: Several,
1) Higher self discharge rate.
2) Approx 2-3 times the operating cost. NiHm generally cost more than NiCad and has approx. 1/2 the charge/discharge cycles. A NiMh will take approx 400 charge/discharges cycles (days if you use and charge your radio each day) where NiCad is about 800 cycles.
3) More susceptable to damage by over charging. Do not leave a NiMh battery in a charger more that 12-16 hrs. Most older (slow) chargers were designed before NiMh were popular will ruin NiMh batteries due to their 10% charge rate type charging. NiMh wants to be rapid charged and then step down to a 3% or pulse maintenance charge.
4) NiMh batteries are not good for radio's/pagers that need to be on monitor (turned on) in a proper NiMh capable charger due to the info above. The low maintenace charge is not enough to provide the current required by the radio and the battery. After the initial rapid charge, the battery will discharge while providing the current to the radio so when you remove the radio from the charger in the morning, you may only have a 60-70% charge in the battery.

Much of this is directed to two-way radio but also will apply to some extent to the pager.

In general, we do not sell NiMh unless size or battery cappacity is the prime concideration and customer is aware he will replace the battery twice as often as he is used to with niCad.