>I would think that putting jumper cable clamps across a 12v car battery and
>plugging the other end into a 24v slave cable plug would damage the 12v
>system.
>
It certainly would, damage would likely be wholly catastrophic, culminating in
vehicle fire.
>It wouldn't help crank the 24v system either.
>
Certainly would not.
> In a pinch, you could
>use regular jumper cables to charge one battery at a time. BE sure to
>disconnect the cable that connects the two 12v batteries together before you
>try to charge either one.
>
Without giving offence, if this question of 12V/24V battery jumping has to be
asked it is safer not to attempt it in any way, there is a very real danger of
exploding a battery owing to severe over-volt application or gassing, and/or
starting a vehicle fire; far better to use another 24V vehicle, but it is
possible and I have done it, it is fraught with danger though. Not a
recommended procedure at all, beware.
As was recently discussed on the list bear in mind a heavily charging battery or
one nearing full charge (2.3V/cell ~ 13.8V on a nominal 12V battery) out-gas a
perfectly proportioned explosive mixture of H2 + O, the resultant combination of
these elements is water of course, but the process of combination involves a
violent explosion usually triggered by a spark at a battery terminal.
Ensure the 24V vehicle has all electrical systems off, preferably isolated with
a two-pole master battery switch. Even better for safety, disconnect and
isolate the 24V vehicle's positive and negative battery connections and
disconnect the inter battery link lead.
Each 12V battery in the 24V system can receive a charge in turn from the 12V
slave vehicle using regular jumper cables, observing polarity, and connecting
directly to the terminals of the individual 12V batteries of the 24V vehicle one
at a time.
Disconnect both jump leads from one battery before connecting to the other to
ensure that 24V cannot be inadvertently applied to the 12V slave vehicle, or a
jump lead short circuit occurring via the inter battery link cable should this
be still connected.
If, for whatever reason, the 24V vehicle batteries cannot be readily isolated
then the following is crucial.
Under no account use a jump lead to make a chassis to chassis connection between
the two vehicles, make absolutely sure no inadvertent contact to chassis can
occur from the jump lead clamps and ensure absolutely no metallic contact of any
type, especially inadvertent body to body contact of the two vehicles can occur
by whatever means.
Only the jumper cables can be allowed since it is likely when charging the "top"
battery of the 24V vehicle, the slave vehicle body will be 12V above the ground
reference.
It is not necessary to remove the 24V vehicle inter battery link lead but highly
sensible as a safety precaution to alleviate the potentially dangerous situation
as above.
Remove all jump lead connections before using any electrical circuit or
attempting to start the 24V vehicle.
Richard
(Southampton UK)
===
To unsubscribe from the mil-veh mailing list, send the single word
UNSUBSCRIBE in the body of a message to <mil-veh-request@skylee.com>.