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Overly sensitive NiMH battery chargers
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13hm13:
I own two different AA/AAA NiMH battery chargers from  MAHA Energy (Powerex). I bought them brand new from Amazon in 2009.




Since day one, both chargers "fault out" (refuse to charge) a relative high % of batteries (including Maha's own Powerex brand batteries).

I have an older Lemnar charger which can charge the same faulted-out batteries.



Is there any way to adj the Maha chargers' circuitry so that they are a bit more "accepting"?
ogden:
Many smart chargers refuse to accept overdischarged (below 0.5V or so) NiMh batteries. Solution is: use exclusively low self-discharge type, such as Sanyo Eneloop, IKEA Ladda and similar batteries, regularily check your battery stock (if any) and cycle all batteries every 2..3 months or so. Also avoid using NiMh in dumb (motor+switch+battery) devices/appliances that do not have low battery 0.8V/cell cutoff.
13hm13:

--- Quote from: ogden on July 29, 2019, 11:10:00 pm ---Many smart chargers refuse to accept overdischarged (below 0.5V or so) NiMh batteries. Solution is: use exclusively low self-discharge type, such as Sanyo Eneloop,...

--- End quote ---
Almost all the NiMH batts I now use are Sanyo Eneloop.
I can charge them up to well above 0.5v on the Lenmar. But they still fault out if I, then, stick them in the Powerex chargers.
Resistance/impedance issue, perhaps????
GLouie:
I also have a Maha C9000, use only Eneloops AA/AAA, and occasionally get "cannot charge" errors when older AAA batteries are reported as too high a voltage. I suspect it's something to do with the initial test algorithm and internal cell impedance. AFAIK there are no internal adjustments. I have never had a problem (high or low) with Eneloop AA, and by discharging the problematic AAAs in a flashlight for a few minutes, can proceed with charging. I never seem to have any overdischarged cells - my devices cut off inteliigently, or I just recharge before it's really needed.

My better solution was to get another brand charger (Xtar VP4+), which lets me charge 4 LiIons as well, and with the Maha, charge twice as many NiMH cells at a time. The Xtar has quirks of its own, but so far has not refused to charge a cell.
ogden:

--- Quote from: 13hm13 on July 30, 2019, 12:37:30 am ---I can charge them up to well above 0.5v on the Lenmar.

--- End quote ---

So you overdischarge them. Long time below 0.5V leads to capacity loss. Charger may refuse to charge overdischarged, near-death battery with little remaining capacity - especially if it is high speed charger that does not support small < 1Ah batteries. Cycle those refused batteries, look what is reported capacity. If >=1000mAh and charger still do not accept such at >=0.5V - your charger may be faulty.
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