How to tell if battery rating is accurate

[donnyboy]

I bought 4 new rechargable NiMH 9 volt batteries off of ebay and the rating is 270mAH. I don't know what the average alkaline rating would befor a 9-volt, however they don't seem to last very long in comparison. I'm using them with some proffesional audio equipment and I'm wondering how can I test them to see if they are really 270mAH. I'm using a battery charger that is shuts itself off after they are charged.

Thanks,

Donny

 

[IRstuff]

Maybe, the Duracell Ultra datasheet shows a maximum capacity of around 500 mAh at 7V threshold.



TTFN

 

[felixc]

Chargers for NiMH have to be adapted to the power rating of the battery. They will inject a fixed current during a fixed amount of time. You have to see if the numbers from your charger match those needed for your batteries. If there's not enough charge, well, the charge does not last long. But if there is an overcharge, the battery may quickly degrade and may explode or damage the equipment. There are numerous recalls for NiMH battery packs.

 

[IRstuff]

NiMH batteries have another attribute that affects the apparent capacity of the battery, which is that the fully charged voltage is considerably lower than that of an alkaline.

In many devices, the battery voltage is used to generate the low battery warning, but that's often based on an alkaline battery. Therefore, in those cases, the fresh NiMH battery starts off looking like a slightly discharged alkaline.

TTFN