Battery Shorcut

[maesitos]

Hi guys yesterday I was installing my new LiFePo4 48v 20Ah (vpower.hk) and while I was soldering a wire the positive pole of the output of the BMS touched the blak pole right in the broken bridge you see in the picture:

The bridges are all connected to the negative pole (black) so I accidentally connected the positive and negative pole thought one of the bridges. An intense light came up for a second and I could see what you see in the picture, a broken bridge (just one).

Well now I don't know if my battery was damaged, I hope the bridge worked as a fuse... but I don't really know... I don't have any wattmeter to test the amp/hour and unwrapping battery I think isn't a good idea yet. Everything works all right, I can read the same voltage as before the shortcut and today I could go 40km light pedaling before the BMS cuts off (2nd cycle)...

Any Ideas? should I be worried? Any way to test the battery?

Sorry because of my english, this is a bit hard to explain in my non-maternal language.

Thank you.
Guille.

 

[liveforphysics]

Not really a bad place to short on your BMS if you had to short somewhere. I bet it's all fine.

Solder the shunt's back together, and don't use copper when you do it! Only make a solder bridge, laying copper across it would really throw off the resistance value of the shunt.

 

[dogman dan]

The battery is likey to be just fine. The way to find out for sure, is to use the unplugged balance plug as a point to use a voltmeter. You can put the probes on the end two contacts giving you the voltage of that cell group, then move down one, and measure the next etc.

To see the whole pack voltage, you would put the probes on each of the end contacts on the plug.

 

[maesitos]

The battery is likey to be just fine. The way to find out for sure, is to use the unplugged balance plug as a point to use a voltmeter. You can put the probes on the end two contacts giving you the voltage of that cell group, then move down one, and measure the next etc.

To see the whole pack voltage, you would put the probes on each of the end contacts on the plug.

That is what I did and I there was the same voltage diference between the cells (3.5V)... Does this test check every cell in a group (serie) is ok?

Thank you

 

[liveforphysics]

The battery is likey to be just fine. The way to find out for sure, is to use the unplugged balance plug as a point to use a voltmeter. You can put the probes on the end two contacts giving you the voltage of that cell group, then move down one, and measure the next etc.

To see the whole pack voltage, you would put the probes on each of the end contacts on the plug.

That is what I did and I there was the same voltage diference between the cells (3.5V)... Does this test check every cell in a group (serie) is ok?

Thank you

If they all have the same voltage between them, they should be fine.

 

[maesitos]

I tried again after charging all night and I get 3.7V between the series group except in 2 that I read 3.4v and 3.3v Is this just not well balanced? (it's in its 3rd or 4th cycle) is this normal?



Thank you!

 

[maesitos]

I bought from vpower.hk and I'm a bit nervous... I don't really trust those guys (how can you trust a seller who don't pay the DHL insurance when they make you pay for it?), not serious seller from my point of view, next battery I'd buy from ping. I don't know if that unbalance is normal... maybe battery was damaged while shipping... you don't really know when you don't trust your supplier. I need to do a serious test, I'm on time till August 4th to claim using PayPal.

 

[dogman dan]

Yes, a new lifepo4 can be pretty unbalanced for the first 10 cycles or so. I like to do some very short rides followed by leaving it on the charger for a long long time when the battery is new. So ride around the block, then charge till the green light comes on, but leave it charging after the green light turns on so it can continue balancing. The battery charger may turn on and off for quite some time. After it settles down, then ride around the block again.

If the bike isn't set up yet, a car headlight or a heating element can do a discharge. You just need to bleed out enough power to kick on the charger again.

 

[maesitos]

Yes, a new lifepo4 can be pretty unbalanced for the first 10 cycles or so. I like to do some very short rides followed by leaving it on the charger for a long long time when the battery is new. So ride around the block, then charge till the green light comes on, but leave it charging after the green light turns on so it can continue balancing. The battery charger may turn on and off for quite some time. After it settles down, then ride around the block again.

If the bike isn't set up yet, a car headlight or a heating element can do a discharge. You just need to bleed out enough power to kick on the charger again.

Thank you, thats what I'm doing now. I'll be watching those cells. I hope they will balance.

I'm starting to love my ebike.