Help diagnosing blown input battery charger

Thread Starter


Joined Feb 1, 2019
I just purchased a top of the line AIMS POWER 36v / 48v Battery Charger from eBay that was listed as "untested but brand new" for only $50!


Unfortunately when I received it I noticed some small signs of use and that some of the case screws were stripped out! So I decided to open it up first to make sure all was well and I'm glad I did....

The 120v mains input side has been blown up. I will post pictures below.

The input fuse is completely burned up. Immediately next to that is a large thyrister and 2 large input filtering capacitors I believe, that are slightly blackened but may just shmoo from the blown fuse... Maybe.

*** also I noticed on the output of the charger there is a black short circuit mark on the negative screw terminal, and the positive terminal screw is completely missing....

So possibly the output was accidentally shorted together, but would that cause the input to burn like that?

Other than that there is no noticeable damage anywhere else. All the other components look fine as well as the PCB.

There's a large Bank of N-Channel mosfets, I'm going to start checking each one to make sure they're not blown...

There is currently NO short on the input or on the or output.

If anybody could please help with any advice on what I need to start checking, how to confirm it's safe to replace the input fuse and try to power it back up, etc...

I appreciate your help! This is a $400 battery charger and if I could get it up and running that would be fantastic.



Joined Jan 23, 2018
I would return it for the reason that clearly the seller was not telling the truth, which is that the supply is not brand new, but rather used and damaged. It may be repairable, and indeed would be a bargain if it were repaired.
AND certainly you were very wise to open it before applying any power, because we know that the seller would have claimed that you damaged it by connecting the power.
I suggest first asking the seller what they did to cause that much damage. It may have been a reversed polarity connection when powered, or connection to the wrong mains voltage.
Stripped screws point towards an incompetent person working on it.
When and if you apply power I recommend an external means to limit the current initially. That could be a 100 watt incandescent light bulb, as one simple option. If the bulb is not bright under no load condition then full power, with a fuse in line, can be connected.