Turbo Start QPET 16V/25A racing charger repair

[CapLeaker]

Another weird charger. Didn't even know that there is a 16V AGM battery. I guess that's what racing guys use and it's quite the complicated thing looking at the inside of it. Never have seen a charger like that. No schematic or anything.
Complaint: It doesn't charge the battery.
Anyone knows what a HIS235 or HS10235 is? Can't find anything about it.
The unit turns on red PWR Led is on and I've got like 40V laying on the secondary of the main transformer, but get nothing at the cable clamps. Not sure, but I think it may want to see an actual battery on the charging terminals before it turns on. I also think it is an AGM battery charger and it does have a timer circuit.

[R_J]

Re: Turbo Start QPET 16V/25A racing charger repair

I would thiink it needs to see a battery connected before it outputs any voltage.

[CapLeaker]

Re: Turbo Start QPET 16V/25A racing charger repair

I measured around for shorts / opens. Well... those HIS235's are bad. I took both of them out and they have a failed in a strange way. The center pin isn't connected to the tab. Both outer pins are shorted together. There is no connection from center pin or tab to any of the outer pins.
I think the AC form the secondary side of the transformer needs to get rectified. The HIS I think is standing for SCR, but what 235 or 236 means in an actual rating, I have no idea. A SCR in a TO247 package should have a pin out of Anode, Cathode and Gate. That means in my case anode and cathode are wide open, but the anode is shorted to the gate. Makes sense, why the charger doesn't work.
Better question is now with what do I replace these HIS235's with?

[CapLeaker]

Re: Turbo Start QPET 16V/25A racing charger repair

HIS235 translates to SCR 200V 35A. It should be Cathode, Anode, Gate. Both SCR’s are shorted cathode to gate (pin 1 to 3). The tab and anode (middle pin 2) are wide open. The case style is a TOP3. Now I wonder if more is wrong with the gate drive or not.

[CapLeaker]

Re: Turbo Start QPET 16V/25A racing charger repair

Ordered some Little Fuse S4035JTP SCR 400V 35A TO218X with isolated tabs. That should do the trick. Didn't find anything wrong with the components on the Gate.

[redwire]

Re: Turbo Start QPET 16V/25A racing charger repair

It looks like a typical battery charger using phase control. The SCR's gate is driven by the H11 opto-couplers U4, U5. There's a current-transformer so it must do CV/CC control.
The only scenario where the SCRs could fail I think is a reverse polarity connection to the battery.
You'd have to sketch a schematic to figure out the calibration trimpots.

[CapLeaker]

Re: Turbo Start QPET 16V/25A racing charger repair

Yes, this charger isn’t that dumb. It’s also got a timer IC in there. The parts in the gate drive are good, just both SCR’s are shorted cathode to gate leaving the anode wide open. There is a trimpot for trip, limit and current, each. Each SCR does a half cycle of the sine wave.

[CapLeaker]

Re: Turbo Start QPET 16V/25A racing charger repair

Turns out the SCR's are actually O.k. when tested with my bench PSU. The DMM and another component tester didn't have enough oomph to trigger the gate.

Problem was in the wiring. A chaffed cable to case GND!

Unit works fine now!