The Mitsubishi Pajero Owners Club®

notsabad · Posted: Mon Aug 12, 2019 17:50 Post subject: Which Battery does what?

Hi, My Pajero has two batteries (as everybody's does) but they are different ages. My truck is not starting on a morning now, so I was wondering which of the batteries I need to change so I can get her started again. Is it the one nearest the windscreen that provides most of the power to the starter motor, or is it the one nearest the radiator? Many thanks in advance . . .

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Simon_W · ******* Joined: 21 May 2013 Posts: 4881 Location: Watford

The batteries are wired in parallel to give more power. So both positive terminals are connected to each other, as of course are the earths. If they are being replaced, both batteries need to be swapped out at the same time otherwise a single new one will be drained by the old one. If the batteries you have currently are not a matched pair, that might be the problem.

Several owners have removed one battery and replaced the other with one of a suitable rating. If you do this, remove the redundant cable to the second positive terminal so that there's no risk of a short.

notsabad · Posted: Tue Aug 13, 2019 14:02 Post subject:

Hi Simon, many thanks for your reply. A few years ago when I was having the batteries changed, the guy said to me that one battery does the starting, and to use his expression "the other battery is for all your toys" i.e air con, heated seats etc. When I used to drive an electric forklift in the 1990's I was able to see the "bridging" between all the batteries when I had to re-charge it on a night, but can't see any bridging on my '91 mk2 paj'. I have bought a trickle charger today as my batteries are less than a year old, which one of the batteries would you be inclined to charge up first? Many thanks . . .

NDZ · Posted: Tue Aug 13, 2019 15:27 Post subject:

The err service you paid for getting the batteries changed should have resulted in two identical batteries. As mentioned by Simon, it is counterproductive to mix and match and it doesn't make electrical sense to have two batteries fitted but then only use one to deliver the cranking amps for cold starting, not to mention some kind of charge controller monitoring two batteries. No, I'm going with Simon i.e. they are parallel wired so the circuit only sees one battery but by having two in parallel it gives you double the amps. Get two new ones to be sure, or you could no doubt live with one new battery just fine but that means disconnecting the other.

Mark3 · Posted: Tue Aug 13, 2019 16:30 Post subject:

Yes if changing both batteries try to go for the same and biggest that will fit BUT if just one has died you dont have to change the other!

As long as your other battery is ok you can connect a new battery to the old one (assuming there both 12 volt lol) with no issues at all and they dont have to be the same rating either, i know this because i have done it on my own Pajero, i bought the biggest battery that would fit and it was fine for over 2 years then i sold it Sad

Its all well and good people suggesting this approach, to disregard a perfectly good battery, but their not paying for it are they!

notsabad · Posted: Tue Aug 13, 2019 17:21 Post subject:

Thanks for the replys fellas. So just to clarify, If I ever need to have my truck Jump started with its new batteries in the future, with a power pack or jump leads, are you telling me it doesn't matter which of the two Batterys the restart Jump leads needs to be attached to ?

Simon_W · ******* Joined: 21 May 2013 Posts: 4881 Location: Watford

Simon_W · ******* Joined: 21 May 2013 Posts: 4881 Location: Watford

Mark3 · Posted: Tue Aug 13, 2019 18:47 Post subject:

notsabad · Posted: Tue Aug 13, 2019 19:02 Post subject:

Thanks Simon, but my 2 new batteries are not visually connected (or bridged), and look very separate to me, as they have done so since I bought it my truck in 2005. I'm clearly not an electrician, as you've obviously worked out, so are you saying these batteries work in unison somehow when trying to turn the starter motor over?
I'm not electrically minded as I stated, but if you put Two 12volt batteries together, wouldn't that make the juice to the starter motor 24volt? or am I just a numpty . . .

Simon_W · ******* Joined: 21 May 2013 Posts: 4881 Location: Watford

notsabad · Posted: Tue Aug 13, 2019 20:46 Post subject:

Thanks Simon. I've now got the trickle charger on as I don't use mi truck much nowadays. If you say that both batteries are connected, does that mean I can put the Live lead from the trickle charger to one battery(+) and the other to the Negative earth on the other (-) , so that both batteries could be charged together?

Simon_W · ******* Joined: 21 May 2013 Posts: 4881 Location: Watford

notsabad · Posted: Wed Aug 14, 2019 12:09 Post subject:

Charged it overnight with a new £20 argos trickle charger, with the earth charger lead on one battery and the live on the other battery and mi truck started up straight away this morning, thanks for your help . .

Andy1966 · Posted: Thu Aug 15, 2019 22:40 Post subject:

all good it started at last when had battery problems I changed mine to a single battery had to modify the wiring abit but it worked really well