Wired two set of nicads together for a home build headlight.
Made of 2 7.2v rc packs. (with two cells removed) So 12v. Charged with a nicad charger for correct time.
Packs were wired as follows as advised by a friend. - + and - from each pack to connectors. other + and - soldered together forming a loop.
Stripey black and white wire of charger assumed positive.Black negative.
First time out pack lasted 5 minutes. Recharged - cells became really hot after 1 hour ( of a 6 hour charge) so i disconnected. Voltmeter says no volts at all?
Any ideas welcome.
Cheers.
If the two packs were unevenly charged to start with then the cells with more charge would have taken most of the charge. You would get a similar effect with unmatched cells. Over-charging would cause overheating in those cells. That could have killed a cell or popped a thermal fuse. Can you measure the voltage across each cell? Best to check charger polarity with a meter, too.
Little confused as to how you have then wired in it should go “ + batter - + hatter - “ then the + and the – from the end should go strait to your bulb. Most cheap hobby chargers will not charge 12V so just be positive yours can. Also is a definatly a NiCd charger as its old tec. If its a time charger you will have to calculate the correct charge time. NiCd are really old school so they may be really old. If so you will have to cycle them a few times to get any life out of them. Also have you got the charger plugged in correctly as its relatively easily to get it wrong? If you stick up some photos of all you kit I can tell you more.
thanks. yeah the charger is for nicads and working. Used to use it for an old an old Smart offroad unit 12volt light jobby. Good point about the cells being charged differently, although they were both new and should be emptyish.
Ziog, sorry not able to do photo's -
4 leads. POS A, POS B, NEG A, NEG B.
2 connected together - POS A, NEG A. connects both packs.
2 to the bulb POS B , NEG B.
Hope that is clearer.
I'll will check each cell with a voltmeter but am unsure of how to do so in the are indeed flat.
Is the charger polarity to be checked a/c with a voltmeter? or d/c. Is it safe?
Cheers
^ unless your As and Bs are mixed up you've shorted one pack
sorry my mistake. POS A NEG B connected.
POS B and NEG A to bulb.
cheers Simon,
If its a basic time charger you will have to know the capacity of your cells and the charge rate to calculate the correct charge time. Or is it a delta peak charger? Though if your only using a 12V charger that could throw a spanner in the works as the battery you have made are actually 14.4V and not 12V. Some chargers can be very picky on voltage some are not so much. If you post up a few photos of the labels on your original betterys, charger and your new batteries I could tell you a lot more.