Motorola oem nimh battery care tips

Some quick tips on how I get great life out of even the original Motorola oem nimh battery packs …

Despite all the verbage below, it isn’t that complicated - it is just detailed.

Even though I have AA alkalines and high-end rechargeable AA’s like Sanyo Eneloops, Maha MH-C9000 charger / analyzers, I paid for the oem batteries so I might as well use them and treat them right for light duty or extended opportunity-charging use.

The #1 killer of the oem batteries is leaving them in the charger all the time, despite their convenience as a holder. When it comes time to use the radio, the batteries have been slow-roasting for so long that you can make only a few transmissions and they are toast. Moto warns us not to leave them in the charger longer than necessary, but people do that anyway to keep them topped off for emergency use. Not good - the slow-roasting perpetual trickle charge does more harm than good and makes them useless in an emergency. (For techies, this means that the battery has a very high internal resistance - something that can’t be measured with a voltmeter by a consumer!) Moral - don’t leave them in the charger forever! The charging stand is for charging, and is not designed to be a permanant desk-holder.

Nimh batteries have improved greatly since the 1980’s, when endlessly trickle-charging batteries was all the rage. Time and quality even for oem batteries has moved on.

#2 - When I get a new Moto, I follow their directions and no matter what the current state of charge is, I charge for 16 hours. No more. While this may slightly overcharge a pack that already has a bit of charge in it, it equalizes the cells. This is not something you want to do all the time however. Just when new or an attempt to revive an already abused pack. Wait at least 1 hour of rest before doing the following step.

#3 - I personally put the pack through ONE “conditioning” charge. That is, I leave the radio on and totally drain the battery. BUT not to the point of damage. I let it go until I hear the low battery warning chirp, and then ignore that until the radio display goes dead. But now, I IMMEDIATELY turn the radio off - and this means I have to actually be around to hear the chirp when that happens, as further major discharge will harm the batteries. When the display finally goes out, the individual cell voltage is near 1 volt per cell, and this is about as low as you want to go with nimh cells. (about 3v total pack) Moto chose their cutoff voltage wisely. Still - even though the radio seems dead, the batts are still discharging unless you turn off the power switch, so be around and don’t forget to turn off the power switch!

#4 - followup with a normal charge as indicated in the manual. A few hours beyond won’t do a lot of harm at these charge rates, just don’t forget about it!

#5 - If the batteries haven’t been in use for 6 months or more, they need activity and not necessarily a reconditioning charge. Obviously don’t leave them fully discharged.

#6 - Oppportunity-charging

The oem nimh batteries are on the small side, and this means light duty use. For casual contacts, single events etc, they do fine. What you can do is “opportunity-charge”. Instead of draining your battery all the way and doing 100% depletion cycles, just charge when you can. You don’t need to actually finish the charge. Just recoup a little energy during lunch, in the car, etc not expecting a totally full charge. In actuality, doing 100% discharge cycles limits the life of the battery, and opportunity charging can make them last for years instead. Do a full charge when convenient.

So aside from the occasional bad cell from the factory, (I’ve been lucky to not experience that) the oem nimh motorola batteries can be put to good use. You paid for them, and with a little tlc they can do very nice light duty service for years. Mine have.