Car battery charger, no charge.

[Sylvester]

Discovered car battery charger isn't doing its job, ammeter isn't showing much activity, voltage no load is about 8.5v dc, not checked ac before rectifier as yet, what ac voltage would I be looking for before the rectifier?

The charger is a 6 amp with various options 100% charge, float and an unregulated type charge, has a s6015l thyristor and a KBPC1201 bridge rectifier and what looks like some kind of resistor? in the ammeter circuit.

Post pics later

[budm]

Re: Car battery charger, no charge.

Pictures of the units. You are reading 8.5VDC because it is more likely because it dose not have filter cap, it is basically pulse charging. Did you try with another batteries yet, it may have detection circuit to check the condition of the batteries being hooked up to first.

[Sylvester]

Re: Car battery charger, no charge.

Hooked it up to battery on compact tractor, turned on lights and no difference to charge rate, reading about 12v, IIRC the charge voltage should be about 14.6 or so.

[eccerr0r]

Re: Car battery charger, no charge.

I think even without a filter cap it should be more than 8.5VDC. Would like to see pics and AC voltage measured, but I kind of have to assume bad rectifier diode pack, SCR, or bad switch at this point. I've been meaning to take apart my car battery charger to see what was inside, it has baffled me too. The SCR might be the clue that I need to figure out what's inside without opening it...

Usually ammeters are voltmeters that read voltage across a fixed resistor, but usually if that resistor breaks the voltmeter breaks too...

[Sylvester]

Re: Car battery charger, no charge.

Not much to it, the pcb is quite small, some resistors, prob a zener and a few transistors along with the scr and bridge rectifier, not sure what the ac voltage to the rectifier should be?

[budm]

Re: Car battery charger, no charge.

Since it is 100Hz pulse (if it is full wave) is not going to show 12~14VDC on the meter. But if you look with the scope, it will show different reading that the meter will not show.
Learn more here:
https://cdn.badcaps-static.com/pdfs/...b46f74ced4.pdf, page 7, see what the wave form of the unfilter DC voltage looks like from full wave rectifier page 17, 22.
You can do some experiment with the rectifying circuits with and without filter cap to see what your meter will indicate.