12 V - What's going on?
Submitted: Sunday, Jun 29, 2008 at 13:27
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Ramb0
Hi all,
My cruiser has a dual battery setup to which I've now added a third battery in the cargo are. The idea was to plug the third battery into the socket in the cargo are, hoping that both aux batteries would run together giving me extended run time with the fridge. The problem is that when I plug the third battery into the car, it blows the fuse. This is with no load, just plugging it in does this. I've used merit plugs and sockets everywhere, and 25 amp auto wire to make up the battery box and the connecting cables - what am I doing wrong?
Thanks,
Tony
Reply By: Member - bungarra (WA) - Sunday, Jun 29, 2008 at 13:38
Sunday, Jun 29, 2008 at 13:38
maybe one of the batteries is somewhat more discharged than the other and when connected they are in parallell and the current flow caused by the equalisation is a higher current rating than the fuse........remember as the voltage goes down the current draw goes up and it may be as simple as one of these batteries being down on voltage
If the plug in the back of the cruiser is OEM then it is probably fairly light cable supplying as it is only designed for the average device (fridge etc) using probably max 15 amps......
the only safe way to connect in parallell is to run a dedicated wire between the two of the correct guage and protected by the correctly rated fuse allwing for alternator voltage into a discharged battery etc
AnswerID:
312855
Follow Up By: Member - bungarra (WA) - Sunday, Jun 29, 2008 at 13:43
Sunday, Jun 29, 2008 at 13:43
forgot to add that my rear battery can receive up to 40 amp momentarily when the alternator kicks in after overnight discharge for fridges etc
it usually settles down quickly to around 15 - 20 amp but without the correctly designed wiring harness you are playing with a potential disaster
you have to design on maximum load capabilities for when the vehicle is running just in case
FollowupID:
578869
Reply By: Member - Footloose - Sunday, Jun 29, 2008 at 13:41
Sunday, Jun 29, 2008 at 13:41
Have you checked the polarity of the third battery attachments with a meter ?
AnswerID:
312858
Follow Up By: Member - Tony B (QLD) - Sunday, Jun 29, 2008 at 15:25
Sunday, Jun 29, 2008 at 15:25
I would start by checking out the wiring for a short to earth if you have just done some new connection work. Sometimes its thats Easy. Regards Tony
FollowupID:
578880
Reply By: Affordable Batteries & Radiators - Sunday, Jun 29, 2008 at 16:40
Sunday, Jun 29, 2008 at 16:40
Rambo
You are best to stop now before you damage the wiring or cause a short that could catch fire.
Fit heavy cable and fuses via 50A Anderson plugs for this application.
I would recommend 6 B&S if it is an AGM battery. Also make sure to connect to the aux battery under the bonnet that has the isolator so you are not cranking off the 3rd battery.
Regards
Derek.
AnswerID:
312878