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Wonky quick charger?

Posted: Tue Feb 05, 2008 7:35 am
by surgeon
Hi all,
I just bought a used NTN4734A Motorola Saber battery charger and I'm a bit curious whether if it behaves as it should or not. The problem is this: I have two old batteries (one Motorola 1800mAh NiCd and one a thirt-party brand, also 1800mAh NiCd) and when charging them none of them makes the charger turn on the green light (charge complete/trickle charge). The light in itseld does work; the charger does the quick 'light all the icons in quick succession'-dance when powered on. So far I've left the batteries in the charger for up to 70 minutes, at which point they are almost scalding hot to the touch. I can hold them in my hand, but I can't really say it's a pleasure, as it almost hurts my hand.
According to the maintenance manual there is some 'intelligence' for overcharge protection and the like in the form of a thermistor and such in the battery pack itself. Is that all there is in the way of such intelligence, or is there something in the charger as well?
The question becomes: is the charger misbehaving and should get a one way ticket to the scrapheap, or are both the old batteries crappy, with something seriously wrong with the thermistor or such?

Re: Wonky quick charger?

Posted: Tue Feb 05, 2008 8:19 am
by Tom in D.C.
Good chargers, like your 4734, have voltage sensing circuits that are used
to sense a completed charge. Yours has obviously quit, but that's not
so bad because 4734 chargers have really gotten to be cheap these days --
almost a throwaway item -- so why not dump yours and get another one and
stop frying the batteries? I think you SHOULD be getting a trouble indication
on start up but no matter, it's easier to just replace the charger.

Re: Wonky quick charger?

Posted: Tue Feb 05, 2008 8:22 am
by surgeon
Tom:
Yeah, that's what I thought. Pity they're so heavy; that makes for an interesting distribution of cost between the item and shipping to Sweden ;) Anyway, got a couple inbound to test. Thanks!