Lead Acid Battery Bulging

[Zach Zaborny]

Hello,
I have two 12v 10Ah lead acid batteries that an electric scooter runs on.
I lost the original charger and have been trying to use a car battery
charger I had laying around. When doing each battery individually, they
charge normally. However, I tried doing both batteries (in parallel), one
started "bulging." Also, the bulging battery was very hot after charging,
which may be the cause of the bulging (plastic + high temps = not
good.) But the other battery was fine.

The charger is rated 8A @ 12/6V. It's built-in ammeter says that when
I put both batteries on in parallel, only about 7A is drawn; if that helps.

The charger is supposed to shut off when they are done charging, but
they never "charge" until they no longer draw any current. The lowest
the ammeter goes is 2A when they are on there. I have no idea if this is
normal.

What's going on here?

Thanks,
Zach

 

[CWatters]

Hello,
I have two 12v 10Ah lead acid batteries that an electric scooter runs on.
I lost the original charger and have been trying to use a car battery
charger I had laying around. When doing each battery individually, they
charge normally. However, I tried doing both batteries (in parallel), one
started "bulging." Also, the bulging battery was very hot after charging,
which may be the cause of the bulging (plastic + high temps = not
good.) But the other battery was fine.

The charger is rated 8A @ 12/6V. It's built-in ammeter says that when
I put both batteries on in parallel, only about 7A is drawn; if that helps.

The charger is supposed to shut off when they are done charging, but
they never "charge" until they no longer draw any current. The lowest
the ammeter goes is 2A when they are on there. I have no idea if this is
normal.

What's going on here?

Have the batteries been left empty for any length of time? That's the
fastest way to kill lead acid batteries. If these are wet cells then it's
best to leave them on a charger which has a float charge mode between use.

I think I would be tempted to measure how each battery performs by
discharging it to say 50% capacity using 12V bulbs. (eg draw 5A for 1 hour).
If the voltage on one is much lower than the other while on discharge or
gives out before it reaches 50% then it's probably suspect and due for
replacement.

 

[Jamie]

Hello,
I have two 12v 10Ah lead acid batteries that an electric scooter runs on.
I lost the original charger and have been trying to use a car battery
charger I had laying around. When doing each battery individually, they
charge normally. However, I tried doing both batteries (in parallel), one
started "bulging." Also, the bulging battery was very hot after charging,
which may be the cause of the bulging (plastic + high temps = not
good.) But the other battery was fine.

The charger is rated 8A @ 12/6V. It's built-in ammeter says that when
I put both batteries on in parallel, only about 7A is drawn; if that helps.

The charger is supposed to shut off when they are done charging, but
they never "charge" until they no longer draw any current. The lowest
the ammeter goes is 2A when they are on there. I have no idea if this is
normal.

What's going on here?

Thanks,
Zach

sounds like to me one of the batteries already had a good charge in it
and was getting drained off very fast, or was getting charged very fast
by the other etc..
try using high amp Diodes to isolate them, your charger should have
enough to get over the average .7 volt drop.