Batteries being drained while truck if off

[HippoNZ]

Hi guys

I'm not sure where to look on this one but I have 2 brand new batteries which are being drained while the truck is sitting over night/during the day etc. I thought it was the old batteries so they got replaced with two bigger and higher amperage ones. I have nothing left on while the truck is off and pull out whatever is being used in the cigarette lighter. Can a once used cable that has been cut be draining the batteries? I also noticed that the volt meter on the dash used to display over 24v now it sits under it. Would love to hear opinions before I'm stranded somewhere with a flat battery lol

cheers in advance
Brett

[YNOT]

Start by checking the alternator, it should be puting out around 26-27 volts (assuming 24 volt system) at 1200rpm.
After going for a drive for a few hours check the specific gravity (SG) in the battery cells with a hydrometer. SG of 1275 or higher indicates battery is fully charged.
If the alternator is fully charging the batteries then you need to check for power drain with an amp meter. Remove the negative battery cable and put the ampmeter between the cable and the battery terminal so the amp meter is now in the circuit. If you have more than 0.05amp drawer then start pulling fuses out until you find which circuit has the drain. You will then need to find the drain in that circuit.

Tony

[HippoNZ]

Cheers Tony, do I check to see if the system is putting out 26-27 volts by chucking a volt meter across the main battery? A point I just found out I chucked the battery charger on the second battery and wasn't drawing any juice but then I chucked it on the main battery and shes drawing 8amps at the moment, so this got me thinking, is my alternator not charging my main battery? And your assumption on a 24v system is correct.

[YNOT]

Yes, voltmeter across the mai battery while the engine is running.
That's interesting that only one battery seems to be discharging in a 24 volt system. Are there any 12 volt accessories running directly off the main battery?

Tony

[HippoNZ]

I'll add a correction to that, sorry I didn't leave the battery charger on long enough on the second battery. They are both drawing 6-8 amps on the charger. There are 12v accessories running off the main battery which still work when the ignition is off, the CB (which has been unplugged since I've known something is not right and the cigarette lighter which has nothing plugged into it, that's all I'm aware of at the moment. I'll test what voltage is being drawn when I get these batteries charged up and the truck running again. I don't particularly like the feeling of things being able to still run with out the key turned on in the ignition but I guess the fella who had it before me went the cheaper way and didn't use a 24v -12v step down and went direct to the battery.

[timbar]

so u are running 12v and a 24v system??

[HippoNZ]

so u are running 12v and a 24v system??

Yeah well the truck is a 24v system but for the likes of the dash lights, radio,cb and that sort of stuff is running 12v system. Half of the 12v system is done properly and the other half is a DIY " she'll be right" job lol ( previous owner).
I want to tidy this up at some stage but not my biggest priority, but then again maybe it is if it's draining my batteries cause I ant getting far without em lol

cheers
Brett

[HippoNZ]

Hi Tony
Batteries charged, I ran the truck at 1200rpm and put a volt meter accross the main battery terminals and it reads 10volts? Wondering if you could tell me what to do from there.

Cheers
Brett

[Finly Owner]

check wiring on back of alternator and make sure none are loose or have broken

Tim

[katwoman]

Stating the obvious ?? An interior light or DVD, radio ect staying on, you dont see ? I had a boot light staying on, took ages to find it !!