I have to charge 2 12v batteries for my wife's invalid buggy, but the
24v charger that came with it has died. I have charged the two batteries
separately using a 12v car battery charger, and they are both fully
charged now, but I have to keep swapping the charger from one to the
other to keep them floating. Can I wire them in parallel and leave them
on the charger, or will one of them end up discharging and the other
If the batteries are not car batteries you could be damaging the batteries
using a car battery charger!
If they are get SLA (Sealed Lead Acid) or GelCell type, then disconnect car
charger and get a proper charger before you have to buy new batteries (a lot
How do mean the charger "has died" ? Have you checked that the fuse in the
plug or the flex to the charger are all OK ? Did you get maintenance
instructions with it ? How old is it ? Chargers are very simple things,
even when they are called intelligent, so are very easily repaired.
Do the lights all come on as they should ? Does it make any humming sounds
when it's switched on ?
It appears to be doing all the things it should - it just doesn't charge
the batteries. It has a Cannon connector to plug into the scooter, and
there is 24v on that, but when I leave the batteries in the scooter they
don't charge as they should.
One battery was dead when I rescued the scooter from mother-in-laws
garage, where it had supposedly been left on charge, but the other has
recovered. I now have one new battery and one older one. The scooter
runs happily when I charge the batteries one at a time, but during
periods of inactivity I have to keep swapping them over to top them up.
I'm wondering whether a 24v charger might be better and charge them in
Series charging is not a good idea, believe me. Does the charger have
automatic cut-out on it ? Have you checked that all the connections are
clean and clear, and made off properly ? If you have any loose connections
or broken cables then the system is not going to work. A bit obvious, but
I'm thinking out loud. :-))
My first question should have been, how old are the batteries, because these
types of batteries only have a life span of around five years, so if they
are any older than that, then it might be time to go for new ones.
If the charger has automatic cut-out, then it could be possible that it is
cutting out to quickly because it was left on to long, so isn't giving time
to charge the batteries properly. Most chargers did have thermostatic
cut-out on them, so this might be the problem. If you can get a test meter
on the batteries when they are in the scooter and then put them on charge
and leave it for a while, the meter might tell you if the cut-out is
activating to quickly and needs replaced.
If you find that the charger isn't doing the job right, then drill the
rivets out and you can get in to make repairs on it. Seal it again with
self-tapper screws or nuts and bolts.
The idea of having damaged cells in the middle of a battery preventing the
other cells from taking their full charge. In parallel the two batteries
have a chance for at least one to get fully up to speed, and could show that
the other battery needs replaced. But having them in series while charging
often shows as both batteries being faulty. Maybe that's just me though.
Oh, so a car battery isn't made up of series connected cells then? So each
cell is in fact 12 volts and they're parallel connected? And I've never
seen a truck with two 12 volt batteries to provide the 24? Or does it use
some clever system to charge them separately? And John is wrong that this
is *precisely* how the wheelchair was charged as supplied?
I'd say you need to take that 'textbook' out of your arse and try
understanding it. Or get one which gives real world applications.
*I don't have a license to kill, but I do have a learner's permit.
Dave Plowman firstname.lastname@example.org London SW 12
If the batteries are both the same age, type and have had the same use, then
However if you have an old battery, and a new one, then NO!
You may end up overcharging one of the batteries because they are not
This will then cause damage to that battery - possibly the risk of it
overheating, and maybe exploding in an extreme case!
On Fri, 30 Jan 2004 00:40:16 +0000 (GMT), Dave Plowman
Assuming they are car batteries that is, I would still say they are
SLA batteries though.
A car battery would more than likely be one, usually to get the
required Ah 2 SLA's are required.
I use 12v 70 a/h SLAs at work.
I'd also say you'd get away with charging a large SLA with a modern car
charger of the type most would have - say up to 10 amps (genuine) or so -
provided you didn't leave it on charge for long periods and kept an eye on
the charging voltage. My few years old Halfords 11 amp (bit generous that
since I've never seen more than 7 amps out of it) never exceeds 14.4 volts
as most car batteries are now of the low maintenance type and don't like
being allowed to 'gas' like we once did.
*Ever stop to think and forget to start again?
Dave Plowman email@example.com London SW 12
Yes, you can. Aklthough this seems at fairt sight a dodgy thing to do,
teh charge/disharge voltage/current relationships mean that it actually
works wuite well.
Campers with motor and leisure batteries will charge them in paralell -
so it's done on a regular basis.
Many thanks for all the helpful comments on this. Luckily my wife
doesn't need the buggy at the moment, so I have time to play around with
The car-battery charger I have is a fairly intelligent one, it charges
in three stages, the final stage being a trickle charge. The two
batteries that were on the scooter were sealed Yeasu <sp?) ones, and
one recovered when I charged it, but the other didn't. I also suspect
the latter is losing electrolyte as there is a damp patch on the floor
underneath it. So I bought a new battery and the buggy ran fine on those
two, but it wouldn't re-charge using the charger that came with it. So I
took the batteries out and charged them with the car-battery charger,
and both are now at the trickle charge level.
From what I have read here, I'm going to connect them in parallel and
leave them on trickle charge till I can hack my way into the original
charger and find out what's wrong with it. However there is always the
thought that it may interact with the electronics on the buggy, but I
suspect they are not very sophisticated.
"accumulators" to the pedants.
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