We had similar issue. In our case the “ON” led on the pcb didn’t light up. Reason : the NTC (situated behind the big plate) was broken. ( totally burned).
Replacing that NTC made the charger function again.
Could you please share what NTC you replaced it with?
I think this has just happened to a unit I inherited recently. The unit has been without use for a long time. As my neighbour upgraded to LiPo batteries.
I powered it up to charge my Lead Acid batteries at 12.1V. It did 60 Amps for about 6 minutes and then suddenly dropped to 10 Amps and now will only go as high as 15 Amps if I am also drawing out load on my system. Otherwise it’s 100% stuck on 10A.
Checked cables, connectors, fuses etc. Haven’t checked behind that yellow “plate” yet with the plastic screws. Haven’t flipped over the PCB yet either. Definitely want to get it working again, whether it’s a cold solder issue or something else.
After a week DigiKey did nothing and when I inquired they said the payment didn’t go through… just tried a second time and it looks again that it has not gone through. So I have been sitting here without a charger and now 3-4 days of heavy rain ahead. Great!
In the meantime I had a proper look at the existing NTC. Did not manage to find this last time I looked but here it is.
Circled the one on my device in red (12V / 60A version)
Here is the existing NTC. Note the crack and excreted hard resin on the corner. It feels sharp and rusty to the touch. I think DVH is right on the money, this is definitely my problem. Was very hard to catch/see initially because it was on the side I could not see and I only found it when touching the NTC with my fingers and then bending it a little into view.
I will try and buy a replacement from Mouser. Super annoying that postage at any website costs between $24 to $115 dollars just for these tiny things!
I got and installed this brand of thermistor: SL22 4R014 which took 3.5 weeks to arrive from DigiKey on account of FedEx being utterly useless. I do note that it is 4 Ohm at room temp and not 1 Ohm like the old one. However:
When I installed it, I still had the same problem. Charger would only output only 10 Amps of current. If I put a heavy load on the batteries through my inverter, the current would climb to a maximum of 18 Amps. The charger heatsinks get a bit warm, same with the new inrush thermistor but still largely no current. I also tested the bridge rectifier and it is working fine.
After talking with Claude.ai, it seemed likely that because neither of my two fans spin (ever). The charger is likely seeing the tach(ometer) pin on the fans at 0 and is deliberately holding off charging. The fans likely spun for about 10 minutes when I plugged the charger in after it was sitting for 3 years and then both failed, or they didn’t run at all (and the charger overheated). Then the current went from 60 Amps down to a max of 10. So either two of my power stages are blown, so I am limited to one, or the 0 rpm on the fans is the culprit. If the power stages are blown (they look fine to me) then the charger likely goes in the bin.
I’ve ordered 2 new fans. They were $22 AU each, not cheap as fans go.
The ones on my 12/60 model were: KDE1208PTV1 3 Pin 12V 1.6W.
I also measured 6.36V on each of the two fan terminals but neither of them spin at all even at half speed with that power.
I will report back again when I get the two fans, if plugging them in makes the charger function normally again. Fingers crossed.
In any case the thermistor still needed to be replaced. I bought the superseded version of the 1 Ohm in case the new one is also going to be a problem after the fans get fixed. Still beats spending $750 for a new charger.
