Outer Limits 4x4 Board

hey guys im posting for a mate.

he has a GQ shorty safari model 24 volt,

he has an inverter running his fridge and head unit, and needs to take his head unit off to turn it off. the other day we tried to start his car and it was flat battery because the invernter draining the batterys for a little over 3 weeks with not being turned over, i jump started his car with mine 12 volt straight over to one of his batterys. we have also ran a 12 volt compressor off one of his batterys.

my question is can you run the head unit and amp(not in car yet) straight off one of the batterys without damaging them or do you need inverters with them all or maybe some kind of resistor.

cheers guys

You can't run the stereo etc off one of the batteries, or you'll end up with two failed batteries.

There is no really straightforward, inexpensive way of getting lots of 12V current out of a 24V system.

You could try something like one of these:

http://www.powerstream.com/dc1.htm

... but they aren't exactly cheap.

Or one of these which is a bit cheaper:

http://www.powerstream.com/dc24-19.htm

If it were me and I wasn't up for converting the whole vehicle to 12V (which would be a huge job) I'd probably seriously consider running a 3rd battery for the stereo power, maybe a sealed one inside the car right next to the amp, and keeping it charged with one of the dc-dc converters above, or a second (12V) alternator.

Good luck.

On the upside at least you can get 24V compressors and winches that go well.

or disconnect the inverter if the car is going to sit for any length of time. it happened to me aswell when i went on holidays last year. i came home and it had dragged one bat down to 0.1 volts and the other at 1.5v, i managed to save the 1.5v battery just. i still use that one for a camping batt. when you do replace them it is wise to replace both at the same time, and both the same brand/type. otherwise you may get over/undercharging on either bat.

on a side note, ya should be able to jump a 24v car with just one jumper, my MQ can be easily jumper with my mates 12v 4runner....




back onto topic, ya can just rig up the system so that nuthing runs unless you actualy have it turned on, then theres nuthin to drain the power... mine has sat there for nearly 2 monthes without being turned over and all my 12v stuff still works fine... its just not on if the car isnt on...

macca81 wrote: ya can just rig up the system so that nuthing runs unless you actualy have it turned on, then theres nuthin to drain the power... mine has sat there for nearly 2 monthes without being turned over and all my 12v stuff still works fine... its just not on if the car isnt on...

it can be done but then there still needs to be power to keep the memory in the sterio.

not a good idea to run things of one battery in a 24v system.
i did it on one of the trucks at work for a quick sterio install and it stuffed one of the batteries within a few weeks.

macca81 wrote:on a side note, ya should be able to jump a 24v car with just one jumper, my MQ can be easily jumper with my mates 12v 4runner....

Yes, it can be done, but it's still not good for the batteries. A 24V system needs the same current to flow through both batteries at all times. As soon as you jump just one you throw out the balance.

If the donor car is running, its alternator will be charging the "jumped" battery and not the other. During cranking the non-jumped battery will flow the same discharge current as comes from the donor vehicle - so it will be discharged more than the jumped battery. And the balance can never be restored by the vehicle's charging system.

-Scott- wrote:

macca81 wrote:on a side note, ya should be able to jump a 24v car with just one jumper, my MQ can be easily jumper with my mates 12v 4runner....

Yes, it can be done, but it's still not good for the batteries. A 24V system needs the same current to flow through both batteries at all times. As soon as you jump just one you throw out the balance.

If the donor car is running, its alternator will be charging the "jumped" battery and not the other. During cranking the non-jumped battery will flow the same discharge current as comes from the donor vehicle - so it will be discharged more than the jumped battery. And the balance can never be restored by the vehicle's charging system.

It will eventually balance itself, but it will need to overcharge the less flat battery which can damage it.

I remember reading something on here about a voltage float or something which draws power from the most charged battery and actively floats between the two batteries to maintain them. Ill see if i can dig up more info on them.

redarc make a 24 volt charge equaliser, it can be used to maintain adequate charge in both batteries and/or used on a 24v system to charge a third 12v battery

i hooked up a 12 volt cd player to the mq run permanent power straight to aux battery and tapped the other power one into the cig lighter, when i went to start it the earth terminal on battery sparks up , wen i disconect the power wires for cd player it starts fine, what is the solution????????????

anyone know???????????

this may be what is happening...
is a mq a 24v car? if so the signal wire you have used i think will be creating a short accross one of the batteries through the cd player. or something similar to that.
id start again from scratch and run all of your cables from the one power source. if you want it always on (not switched with acc) just run one cable in from the battery (the 0-12v one) and connect both the yellow conductor (power) and the red conductor (usually the switch wire) to the cable from the battery. if you do want it switched with accesories, measure the voltage (key in ign acc on) from chassis to the supply feeding the ciggie outlet. should be +12, also measure between the ciggie outlet active and the active feeding the cd player. should be zero. if it is zero connect the red conductor to the ciggie supply. if it measures 24v to chassis use a 24v relay to switch the 12v supply from the battery and the red conductor.