Twin batteries in a Landcruiser - help please!
Discussion
My LC has two and one of them is pretty unwell and I thought I'd change both together as I'm going to keep it for a while.
The obvious tactic is to disconnect both the old ones and put in the new ones. But here I thought I could try and be clever - if I replaced one first and then the other then the car would have power throughout and I wouldn't have to reset the clock, radio etc.
Two things bother me here: The local Toyota dealer says the batteries are used in series to generate 24V for starting - although when I look under the bonnet the +ve terminals of the batteries are wired together, which would contradict this. The other thing is if they ARE in parallel, if I put in a healthy new battery next to a dying one is there going to be a huge current flow between them that could be messy?
Your advice would be much appreciated (I'm getting tired of sticking the thing on a battery charger at night!)
The obvious tactic is to disconnect both the old ones and put in the new ones. But here I thought I could try and be clever - if I replaced one first and then the other then the car would have power throughout and I wouldn't have to reset the clock, radio etc.
Two things bother me here: The local Toyota dealer says the batteries are used in series to generate 24V for starting - although when I look under the bonnet the +ve terminals of the batteries are wired together, which would contradict this. The other thing is if they ARE in parallel, if I put in a healthy new battery next to a dying one is there going to be a huge current flow between them that could be messy?
Your advice would be much appreciated (I'm getting tired of sticking the thing on a battery charger at night!)
Edited by FamilyGuy on Tuesday 1st September 08:12
I may just replace them both together as you say and worry about sorting the radio afterwards.dual batteries (as standard on UK spec 80 and 100 series diesels) run both in parrallel and series.
If you look on the right hand side of the engine bay next to the engine side of the fuse box you will find a plastic "box" which is really just a cover over a very large split charge system.
When you start the car the batteries flick into 24v (and all 12v systems are cut dead) to send 24v to the starter, then when you come off the start position with your key, the split charge flicks back to 12v and both batteries supply 12v.
If yyou have a dodgy battery then change both at the same time- surprisingly i found that the toyota dealer was very good value for batteries (the only thing they are good value for!)- iirc i replaced mine with a toyota 82ah jobbies which because they were toyota supplied they have the terminals in the right place- you need the same batteries but with reversed terminals- you won't have enough play in the terminal wires on the aux battery (the right one) to put in a normal terminal arrangement battery. (hope that makes sense)
If you leave a dead battery in, it will kill the new one. If you use mismatched batteries then you will hasten their demise- best to replace both batteries with a matched pair.
If you look on the right hand side of the engine bay next to the engine side of the fuse box you will find a plastic "box" which is really just a cover over a very large split charge system.
When you start the car the batteries flick into 24v (and all 12v systems are cut dead) to send 24v to the starter, then when you come off the start position with your key, the split charge flicks back to 12v and both batteries supply 12v.
If yyou have a dodgy battery then change both at the same time- surprisingly i found that the toyota dealer was very good value for batteries (the only thing they are good value for!)- iirc i replaced mine with a toyota 82ah jobbies which because they were toyota supplied they have the terminals in the right place- you need the same batteries but with reversed terminals- you won't have enough play in the terminal wires on the aux battery (the right one) to put in a normal terminal arrangement battery. (hope that makes sense)
If you leave a dead battery in, it will kill the new one. If you use mismatched batteries then you will hasten their demise- best to replace both batteries with a matched pair.
oh and with the vehicle off you will lose all settings as soon as you disconnect the negative to just one of the batteries!
just bite the bullet and rely on resetting the clock and radio.
if you ever have to jumpstart the vehicle make sure you use the left battery- and do NOT attach the negative lead to the chassis, but attach both jump terminals straight to the left battery. otherwise you get 24v being fed back to the starting car, which can knacker the starting vehicles battery.
Also even with really good chargers (i have a commercial Ctek for my batteries), very few chargers will cope with the very large dual batteries often found in LCs. Same goes with portable battery starters- haven't found one that will jump start an LC yet! (the large batteries are to supply the massive current needed at the starter to turn over the commercial straight six diesel!)
just bite the bullet and rely on resetting the clock and radio.
if you ever have to jumpstart the vehicle make sure you use the left battery- and do NOT attach the negative lead to the chassis, but attach both jump terminals straight to the left battery. otherwise you get 24v being fed back to the starting car, which can knacker the starting vehicles battery.
Also even with really good chargers (i have a commercial Ctek for my batteries), very few chargers will cope with the very large dual batteries often found in LCs. Same goes with portable battery starters- haven't found one that will jump start an LC yet! (the large batteries are to supply the massive current needed at the starter to turn over the commercial straight six diesel!)
Many thanks, exactly the advice I was looking for! Mines a 120 D4-D but everything you say sounds as if it's right for this LC too. I'll bite the bullet and change both together. I too was amazed by the Toyota dealership being about 30GBP cheaper for each of the two batteries than anywhere else!
To continue the saga - I took some photos. I'm still not understanding the 24V batteries in series to start thing because there is a big solid wire between the two positive terminals which would preclude the positive of battery A to the negative of battery B that's required for 24V. Looks like they are hard-wired for 12V parallel operation?
ETA: All the yellow stuff is what happens if you drive across a field of buttercups...
ETA: All the yellow stuff is what happens if you drive across a field of buttercups...
Edited by FamilyGuy on Tuesday 1st September 18:31
Hi, everybody. This is my first time in a forum so excuse if this is not the done thing but I signed up after stumbling across this thread which is relevant to my project: My old work 2005 Hiace GS 280 d4d stereo upgrade and basic weekend camper conversion.
My questions are on topic regarding this dual battery set up, which my van also has. (Pugwash4x4, you sound like the expert)
I know very little about electrics and don't want to cause damage and drain/destroy the batteries.
So question 1. Does it matters which battery I connect to power my amplifier with?
Are there issues with connecting to just one battery or is it okay? Do I just connect to the positive terminal and then earth the amp just like a normal vehicle amplifier set up? BTW, most of the time I'll be driving when the amp is on, but would be nice to know if when I set up camp and engine is off it would still be okay to play stereo with amp on.
Then eventually I plan to add some other stuff:
Also any tips on where best to run my power leads from for the lights, sockets etc would be great to know.
Many thanks.
Rob
My questions are on topic regarding this dual battery set up, which my van also has. (Pugwash4x4, you sound like the expert)
I know very little about electrics and don't want to cause damage and drain/destroy the batteries.
So question 1. Does it matters which battery I connect to power my amplifier with?
Are there issues with connecting to just one battery or is it okay? Do I just connect to the positive terminal and then earth the amp just like a normal vehicle amplifier set up? BTW, most of the time I'll be driving when the amp is on, but would be nice to know if when I set up camp and engine is off it would still be okay to play stereo with amp on.
Then eventually I plan to add some other stuff:
- One or two lights in the back and in the back door.
- I will need to charge a couple phones so maybe install a couple usb sockets (although I may just use the cigarette point),
- Possibly a transformer for my laptop if I can pick up a cheap one (or switch to usb powered computer).
- Lastly the main draw of power I think I'll be using is to power a 12v cooler for keeping stuff cool. - currently has option of going into cigarette socket (or mains).
Also any tips on where best to run my power leads from for the lights, sockets etc would be great to know.
Many thanks.
Rob
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