Sparks flying: are my battery or charger damaged? Please help

Planet Indigo

100 mW
Joined
Sep 22, 2018
Messages
40
This is my first ebike conversion and I'm very worried about my battery.
I received my battery/charger yesterday and before installing it on the bike, I wanted to make sure all fit and worked perfectly.
I inserted the charger connector inside the battery connector and big sparks started flying, I removed the connector immediately but the charger connector is singed and im not sure if the battery connector is supposed to look like this on the inside. For the record, the battery power switch was off (little circle O, not -) since I had heard that batteries should be charged while off.
I attached two pictures.DSCN2483ss.jpg
After googling some it appears that ebike batteries are a rare exception where it's better to plug the charger in the wall first before inserting the plug in the battery. I'm double surprised because it goes against my previous experience with batteries and my seller's instructions were to plug the charger and battery before wall socket...
The cells still seem to have voltage since the battery indicator still reports 1 green light (same as when I received it). My first priority at this point is to not damage the battery cells. I am very afraid of plugging them together now. The charger has a light indicator, and when I plug it alone in the wall socket, the light stays off, is the light supposed to be off when plugged in and only on when charging? Or on in both cases? Should I try to "clean up" the inside of my battery charging port? Is it supposed to look like this on the inside?

I would very much appreciate any advice on what is my safest next course of action given that my priority is not to damage the cells. Thanks.
 
Before starting to worry, test the voltage on the charger and battery.

I can see that plugging some cheap unplugged charger on the battery could pull a rush of current making sparks, but chances that it did damage either of them are little.

Test polarity on both before plugging again. You never know when some idiot would sell you battery and charger with reversed polarity between connectors.
 
Sounds to me like maybe there is a real short in the charger. Or they reversed polarity when they built the charger.

Look at the charger first, plug it in, and see if the inner part of the plug is positive. it should have been. That assumes of course the charger is not fried.

With luck, your battery is still ok, but if it has no voltage, try to find a fuse.

Switch on the battery would have turned off the discharge plug, but not likely the charge receptacle.
 
Hi

Did you buy the battery and the charger from the same place? Local or from China?

Does the battery voltage state the same as the charger. 36v battery, 36v charger? A fully charged battery or charger effective output will show almost 42v usually for a 36v charger or battery.

Yes its good to first connect charger to the wall or there will be a spark, that spark can "maybe" cause this I have no information or assumptions.

What you need to do is either open the battery up(lose warranty or ask seller that you can do that for a test and keep the warranty) and se how the connector that receives the charger input looks. If it has shorted inside it sure needs a new female receiver connector or if the problem comes from the charger. If you can measure the voltage coming from the charger it should be positive from the inside and the middle of the connector and the negative is the outside "dick" of charger plug haha :D

Good luck or ask more questions or try harder
 
Update:
Contacted seller (both from same seller in china). He told me to test polarity on charger and battery.
Charger is dead, no light when plugged in wall, which seller said wasnt normal for this model. No voltage exiting charging plug. Continuity between the + and - on the charging connector. Brought it to an electronics store, several capacitors inside are dead but there was no burnt place that we could see. The connector as seen in picture has that metal part burnt off and gone. The connector was all black before I wiped it clean to take pic.
Battery seems ok. Polarity at charging port is normal, + in center, - in edge. 45.4v like when I received it. (48v battery at 25% or so charge). The usb charging port and switch still work (switch only controls discharge port).
Seller said hes sending me a new better charger with fan and aluminium case. I asked for upgrade to 3a instead of the original 2a, he said it was much more expensive and heavier to ship, I asked to pay 10$ to upgrade, he agreed to that.

Questions:

1) Did my battery get damaged by this event? Voltage seems to have been unaffected, down to tenth of volt. Did this shorten its life?

2) Anyone has a solid idea on what caused this? Could a cheap charger with correct inside wiring have suffered this by being plugged in the battery before wall? Charger had been in transit 2 weeks so it should be safe to assume capacitors inside were all empty?

3) Does a 2a charger allow more life cycles from the battery than a 3a charger on a 17.5ah battery or are both equal in that regard since they are still slow charging? Basically, is there a point where there's no more return in life cycles by slowing down the charge anymore? Is that point at 0.2C? Higher? Lower?
 
If a charger is plugged into battery first, the output caps are all empty so there is a large rush of current in reverse from the battery to charge them, but it shouldn't cause that kind of damage; the caps in the charger are rarely very large (it would take a lot of capacitance to cause a really high current).

But it is possible to get sparking at the connectors that damages them a little each time (pitting, sometimes soot). This happens when plugging the battery into the controller, and is mitigated by a precharge setup of some type. Again, unles there's really big caps in there, it's not likely to cause much damage each time.

Either way, the battery would be unharmed by this.


However, since the charger is now dead, I'd guess a reverse wiring of the cable or connector (common) or a reverse polarity component--caps can be installed backwards, and it's a common enough problem in cheap electronics (there's often no QC at all, no powerup test, just build it and ship it). You can check for that; usually the - sign on the caps, the striped side, goes to a polarity marked on PCB, typically with a half-shaded circle, which is negative on the shaded half. If there's an output fuse, that's probably blown, but it wouldn't keep the charger from powering on (blown caps could).
 
Those cheap Chinese chargers that they give you when you buy a battery, are not living very long anyway. So it is good that you paid a litlle extra for an upgrade. Nevertheless, the upgrade might not be much better. Alu case and fan are not making for polarity or current inrush protection. Be careful to feed and use it properly.

Many of us prefer charging with power supplies that are built with all the possible protections, thus very reliables. I plug 24s of high C rate lipo on my unpowered charging station without any sparks, I could even plug them reversed polarity without any damage. Still, it’s been built with 2 big old Meanwells that I purchased at electronics recycling for peanuts, when I built my first bike 10 years ago.
 
I acquired a 52v bat ( hailong style from BafangUSA) that needed a BMS.
I Wired the replacement as the previous one , but new BMS lacks a cut off switch.
Works well, takes charge, but my basic noname 52 v charger sparks on plug in. Seems to charge OK

Is there a discussion anyone could route me to that explains what could be happening and what to look for in trouble shooting this?
Something like a basic battery charger schematic that outlines components/component groups?
I read through the above thread.
Could it be a self correcting polarity reversal between the bat and charger?

Thanks
 
It is basically a DC power supply. That is ALL the really cheap ones are.
If you are lucky they may add in a Red and Green LED.

Best advice is use an in-line power meter between the charger and the battery.
Something like this:
https://www.amazon.com/dp/B07FYHTBD2

At least then you will have some idea what is going on.
 
Good idea, I needed a wattsap or something like it , anywho.
Thanks
 
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