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# max current on rechargeable PP3 battery ?

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#### defcon31

##### New Member
hello,

i have something that normaly works with an 220V->9V adapter, but on that thing is mentioned that it asks 500mA...
now, i changed the adapter with a (rechargeable) PP3 battery (9V) of 150mAh... so in the beginning its normal that i have to recharge my battery after 20minutes...
but that after everytime recharging my battery the 20min became less and less and after a few weeks i can only work 4min with it...

is it possible that the rechargeable batteries become damaged because of the large current they have to provide ???

NICAD batteries do deteriorate with use, and are only rated for a relatively low number of recharge cycles. If it only lasted 20 minutes from new, presumably it's been through a LOT! of recharge cycles in a very short time?.

It's probably not a good idea to run something that takes that much current off a small battery, you really need something much larger, which will be more able to provide those current levels.

so it is possible that my rechargeable batteries are damaged (after recharging not more than 15 times) because of the high current they have to provide ?????

so isnt it a good idea to take 5 of those batteries in parallel at te same time ? so they have to provide each a fifth of the current.... is this a solution ?

This 150mAH battery pack need only 15mA charge current and 14hours.
Apply a serial resistor or current limiter.

defcon31 said:
so it is possible that my rechargeable batteries are damaged (after recharging not more than 15 times) because of the high current they have to provide ?????

so isnt it a good idea to take 5 of those batteries in parallel at te same time ? so they have to provide each a fifth of the current.... is this a solution ?

It's quite possible they could be damaged, how are you charging them?.

I wouldn't advise paralleling NICAD's, use bigger batteries - single cells in series would be far better - eight would give you 9.4V, which is a reasonable replacement for a 9V dry battery.

That is about right. Running a 150mAH battery at 500mA will only give you about 20 minutes when the battery is new but it will very quickly deteriorate. The normal discharge rate for a 150mAH battery is 15mA for 10 hours.

Your best bet is to use Nickel Metal Hydride (NMH) batteries..... eight in series. You can get them as "penlight or AA" size at Radio Shack. If you buy the 1800mAH ones, they should last about three and one half hours before they need recharging.

Trini

Trini said:
eight in series.
Trini

eight in parallel you mean, isn't it??? eight in series will give me 8*9V=63V or am i wrong ???

defcon31 said:
Trini said:
eight in series.
Trini

eight in parallel you mean, isn't it??? eight in series will give me 8*9V=63V or am i wrong ???

Yes, you're wrong! - as I mentioned above, it's not a good idea to put batteries in parallel. The batteries mentioned were specified as AA cells, these are 1.2V each - 8 in series will give you 9.6V (not 9.4V as I previously typed wrong).

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