charger blows house fuse

hi guys

I have been charging my second e-bike with a Chinese 48v 4a charger for a few weeks
when during a normal charge the power blew
so I reset the fuse but when I plugged the charger into the wall it blew the house fuse again
I looked inside but there was just a bit of burning by the rectifier
I tried replacing a few of the components but nothing worked it still blows the house fuse when plugged in

so I cut my losses and ordered another one the same , and guess what , after about 5 charges this ones done the same
I have been charging successfully between the charges with a old 36v charger turned up to 48v (54.6)
and this is still in operation but it is a 2A and the 48V are 4A
I know I can go back to the Chinese seller or just buy a different brand
but is there a common cause of this failure where I can solder in an upgraded component that will be better ?
so I can re-use these 2 chargers ?

Possibly the "NTC" (looks like a little disc or "tablet" with two legs going to the circuit board) thermistor (also called an ICL) that is used to limit inrush current has burned out in a way that shorts it. If this happens, then as soon as it's plugged into the wall, so much current flows so fast into the unit to charge it's capacitors/etc that it might be enough to blow the fuse on an already-loaded wall circuit.

There's some posts by Dnmun about NTCs in chargers that might be helpful, starting with this one (see the pic in the post above it for what one looks like):
https://endless-sphere.com/forums/viewtopic.php?f=3&t=13441&p=199495&hilit=%2APTC%2A#p199495

https://endless-sphere.com/forums/search.php?keywords=*nTC*&terms=all&author=dnmun&sc=1&sf=all&sr=posts&sk=t&sd=d&st=0&ch=300&t=0&submit=Search

https://endless-sphere.com/forums/search.php?keywords=*icl*&terms=all&author=dnmun&sc=1&sf=all&sr=posts&sk=t&sd=d&st=0&ch=300&t=0&submit=Search


It could be other things. The fan (if it has one) could've failed, and allowed things to overheat and blow up in a way that leaves the input shorted. Could be the switching FETs, or the transformer, etc. Could even be they installed capacitors backwards, or just defective / leaky ones, etc. Or other things.

But usually any kind of failure that shorts the input *should* blow the fuse on teh charger itself.

If you want to avoid the various problems cheap chargers can have, you could go with something like the Cycle Satiator from Grin Tech http://ebikes.ca , but it is expensive. Worth it in that you can create profiles for several different batteries if you need to, and choose them from a menu whenever you need to, and it's weatherproof and vibration resistant so you can carry it on the bike without risk of it coming apart inside. I use one, and it's very useful with the different voltage and chemistry systems I have here. For just one bike and battery, though, it's versatility is wasted and it's probably more than you'd want to spend for that.

A bit cheaper (but not as cheap as the stuff you've got there) are the Meanwell LED power supplies, like what I built onto the SB Cruiser trike. It's an HLG-600H-54A, which means it'll handle up to about a 12A charge at up to at least 54V (mine adjusts up to almost 58v). There are lower wattage versions that are cheaper (you can look thru my posts (and the rest of ES) for "HLG" and find more info about that.


There's also lots of assorted chargers of varying quality of the more typical ebike variety, some of them posted about on ES (but it would be a lot of reading to find them all; a search on just threads with "charger*" in the title is a lot of hits and that's nowhere near all of them).

Short inside it for sure now. ICL the most likely thing.

thanks for the links they were all worth reading
so I de-soldered the NTC and I have tested it as best I can
it seems OK to me
as I put the teaser needles on the terminals there is an initial "0.000" for a second or two
then the reading climbs to 5.1ohm and if I heat it on the soldering ion it raises value slowly
so not sure if its the issue
on the "short inside" that's what I thought and have been checking for but I cant find any
when I test the phase input terminals on the unit there is no obvious short

I have purchased a different brand of Chinese charger as they are cheep

Probably not hte ICL then.

The short might not show up on a DC test; it might only show up with AC input, or it might only show up above a certain voltage.


Attach pics of the damaged areas on the chargers, and perhaps someone will recognize the failure.

You say it's blowing fuses and you reset it. Since you can't reset a fuse, I'm assuming you mean a house circuit breaker. Check the wiring at the breaker panel. A loose connection there will cause the breaker to heat up and trip the breaker. It could also cause a fuse to heat up and blow also in case it's really a fuse.

ok let me clarify

first occorance
the charger blew its fuse and tripped the house CB
I reset the house CB and replaced the fuse (at this stage I opened the charger and couldn't see and damage )
I left the charger open and after plugging into the wall a switched the wall socket on to "see" the spoke escape
it immediately tripped the CB and blew the fuse again , the spark was at the rectifier between a AC terminal and a DC terminal
I replaced the rectifier but the original one seemed OK under a diode test I also de-soldered the 2 large caps and these were ok so I re inserted them
the next time I switched on it blew the CB again and the RCD? at the house board but it didn't blow the fuse in the unit
then I received a second charger in the mail and started using it until it blew in about 5 or so charges
then I started this post
I was working on the original charger as I wanted to find the issue so I can fix the second charger without bastardising it too much
I have stripped the first charger of most of its components and not really found any burnt parts except the short on the rectifier
the second charger does not have the NTC soldered in from the factory
so I expect the next thing in line is the bit that has failed
i'll post some pix

OK first off a photo of the bikes



this is the "new" second charger that shows no damage but is missing the NTC



this next photo is the state of the first charger , I doubt i'll get it going again



and although blury this is the "shorted" terminals on the rectifier
I'm starting to think it may just be too close to the casing ? and shorting ?

A lot of things could possibly fail. From your description, I'd guess the main switching transistor shorted, and that took out the bridge rectifier. After replacing the rectifier, it blew again, so short is downstream of it.

When those transistors blow, it often takes out the switching controller chip with it and is generally not worth repairing at that point.

I have just taken the board out of the enclosure on the second charger
it has a small burn between the AC terminals of the rectifier
this is similar to the first one

any suggestions or should I cut my losses like fechter implied

If your meter has a diode check mode, you can test each section of the bridge and look for shorts. Also measure across the main cap to see if it looks shorted

Why not plug it into a power strip with a resettable fuse that way you're not blowing your house circuit and can easily be reset.

yep I have given up on this
parts are in the recycle parts bin

thanks for the input guys
I have learnt that I cannot fix everything
no matter how simple it looks !