Jump starting horsebox help please, numpty q!

3

3bh

Well-Known Member
Joined
17 November 2011
Messages
511
Visit site
Hi all, have read lots of threads re jump starting horse box here but not got quite the answer I needed!

I need to jump start my horsebox, it has 2 x 12v batteries in parralel (solely running the engine, the leisure battery is another seperate unit in a different part of the vehicle).

I've got a 12/24v charge and start unit (this one to be precise: http://www.machinemart.co.uk/shop/product/details/bc410e-battery-charger-engine-starter) and I believe as they are in parallel I would connect to positive on one battery, and negative on the other.

But do I need it on the 12 or 24v setting? Have read conflicting info on google and can't quite pin down the answer I need, vaguely remember from dusty corners of brain from learning at school that if they are in parallel, isn't the total still 12v?


Huge thanks for anyone that can answer!
 
Are you sure they're connected in parallel? both positives connected together, both negatives connected together, this would give you a 12v output with double the current.
Lorrys generally run off 24v, suggesting that they should be in series - negative of battery 1 connected to the positive of battery 2 with the output comming from the positive of battery 1 and the negative of the battery 2, giving you an overall output of 24v, hope that makes sense.

If it is 24v and you try to jump off 12v it just won't have the power to kickstart the engine
 
If they are connected in parallel ie + to + and - to - then that gives 12v
If in series + to - (one connection only on each bat) then that gives 24v
 
Turns out, I was being a proper numpty (I did warn!) and they are in fact series., only discovered this once I'd virtually climbed in the cabinet to find the markings of the polarity on the batteries, it wasn't obvious by cable colour or anything?

Thankfully(!) I'm a bit of a woos when it comes to anything technical so hadn't tried mucking around, instead I bleated and did the damsel in distress thing and got neighbouring helpful friendly farmer to do it. He took them both out of the lorry to check their condition, found one was faulty, went out and bought me two new batteries, and it started first time. Phew!

Looking into the idea of the solar panel in ciggy ligher thing as he said we might possibly have a drain in the circuit? How does such a thing work?
 
Last edited:
I've got an isolator switch on our lorry which isolates the batteries so that they cant get drained as we were having loads of problems with it not starting.
 
So do I, should know better really but never used it nor had problems starting.... Even over the winter it would happily start up first time after weeks of not being moved, maybe I shall start to use the isolator on a regular basis now!! (God I'm coming across like a right dippy mare aren't I!!)
 
3bh said:
So do I, should know better really but never used it nor had problems starting.... Even over the winter it would happily start up first time after weeks of not being moved, maybe I shall start to use the isolator on a regular basis now!! (God I'm coming across like a right dippy mare aren't I!!)[/QUOTE

Lol!!!! You need to use the isolator!!!! ;) :D :D

Mine goes on everytime the lorry is standing, even at shows, its just habit, I get out of the cab and put the isolator on.
Click to expand...
 
Tempi said:
Mine goes on everytime the lorry is standing, even at shows, its just habit, I get out of the cab and put the isolator on.
Click to expand...

Same - I have an isolator key so as soon as jump out of cab, habit is now to grab key and zip in pocket of breeches so I can't lose it!
 
You must log in or register to reply here.
Top