2 x 12V batteries in series causing enormous sparks

[AHUSAIN]

Hello,

I just received 2 used Valence 12V batteries. I top balanced them in parallel to 14.6 V. A couple days later they were down to about 13.8 V. I tested voltage again right before connecting. One was 13.87 V and the other was 13.88 V. When I connect them in series to get 24V, an enormous spark occurs on the last connection. I have one battery terminal slightly damaged now with black soot around it.

This happened twice and then I stopped.

I am doing the same procedure I just did with my AGM batteries just a few days ago.

Can anyone suggest why this could be happening on a basic series connection? I would really appreciate it.

Thank you.

 

[AHUSAIN]

These are Valence U-CHARGE XP U27-12XP Lithium 12V 138AH.

 

[MisterSandals]

When I connect them in series to get 24V, an enormous spark occurs on the last connection.

When connecting them in series, there is only one connection, the + from one battery to the - of the other battery.

Connecting the other 2 posts together will of course be a tremendous short and create an enormous spark.

 

[AHUSAIN]

Thank you sir. I REALLY appreciate it.

 

[MisterSandals]

Thank you sir. I REALLY appreciate it.

Can you reward us with a pic of the carnage? (no soiled shorts pics please...)

 

[AHUSAIN]

Awe man I read this too late. I wiped up the soot with a towel but the evidence still remains. I am gathering and plan on posting is shortly.

 

[AHUSAIN]

Damage from my incorrect series connection post cleanup though.

 

[Brewman]

Ouch

 

[BlueFox]

Doesn't look too bad at least, a bit of wire brushing and it should be fine!