Adding Second Battery

PhilGV8

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Jul 31, 2011
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My UK 90 Colorado V6 has a single battery, mounted nearside front. I am looking to add a second battery for auxiliary lighting through a split charge system so I can ensure the engine will always start, regardless of lighting use.
My problem is where to site a second battery. I have seen a picture on here of a single battery mounted nearside rear of the engine compartment, where I have a vacuum unit (which would move I guess). My first thought was to mount it offside front as on the Prado, I have the clamp fixing there (although no battery tray), but my air filter lives there, and looks pretty immovable.
Was there ever a twin battery version of the petrol?
Has anybody else carried out this mod?
Any thoughts appreciated, pictures would be excellent :)
 

Chris

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I have as have quite a few people. In the UK it was fitted as standard on nearly all LWB auto diesels and was called the 'Winter Pack'. Actually it was completely unnecessary in my view. If it had been a split charge it might have been better but what tends to happen is that as one battery starts to fail it drags the other with it. Best mod is to rip out the aux battery completely. Or split them and use one for leisure. I just made a battery tray and stuck it behind the nearside headlight. I used an IBS battery system which is an intelligent system rather than simply voltage sensing. It's pretty easy to do. That way you can link them with a switch if yo need a boost. Not that many petrols on here, but there are some. Not conversant with the layout and space under your bonnet.

Welcome to the forum

Chris
 

sae70

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I don't think that the petrol version has the room for the second battery as us owners of the Diesel versions are used too!

I found this picture of J66P's petrol 95 and you can just see the air box where we'd expect one of the two batteries to be.

Picture837.jpg


Maybe J66P can help you with an answer as he's got a petrol one and also has a winch fitted, so may have found space for a second battery somewhere.
 
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PhilGV8

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Jul 31, 2011
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Thanks the replies :)
Yes, as you can see, a bit of a problem.
I might attack it a different way, and maybe increase my single battery size, plus put some voltage monitoring in so I can see whats happening.
I also have the problem of the battery going flat after about 10 days standing, seems a common thing.
I just replaced the battery with a Toyota 28800 YZZJA 65A/Hr 590A BCI, as they recommended, but I suspect they got it wrong. I saw somewhere 800A is correct?
Maybe fitting the highest capacity I can find, I have seen mention of 1000A 95A/Hr.
Also I am not sure of the alternator output, but I have seen mention of around 100A??? Although this does not ring true, as it is unable to support my additional lighting load.
I have fitted LED lighting where I can, side and internal, to reduce the standing load. My additions are drawing up to an extra 38A. Last week after 3 hours use (with the engine running!) the battery was unable to start the vehicle, which was embarrassing to say the least. So I need to sort something fairly quickly, preferably a quick fix!
 

Graham

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Are you sure the alternator is doing the business?
If your pulling an additional 38 amps, well I would suggest that the alternator is not delivering correctly.
It is then as you can see, allowing the battery voltage to drop.
I would firstly confirm the size / output of your alternator.
Then whip it off and have it properly load tested at a well versed auto-electrical place.
Perhaps you may find that your for example, your 90 amp alternator, can only make 60 amps at best.?

Is there an alternative alternator that can be fitted?
Just a suggestion.

Gra.
 

wobbly

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I was under the impression from a previous thread on alternators that a 100A alternator will only put out a max of about 80% ?

This may explain the problem, as an extra 38A may take your output into negative territory.

Could you mount the battery remotely in the truck, maybe the boot area?

Pete
 

PhilGV8

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Jul 31, 2011
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I have the fuse box behind the battery, but have considered a pair together the other way around on the battery tray, but a lot of work.
Have considered the boot, but I already carry a load of gear, so I would have to re-home stuff to make room. There is enough room under the back seat, but don't really want to go into major mods!
I will do some voltage tests on load when I get a moment, try to see exactly what is happening, and how much I can draw without discharging the battery.
Anyone got any info on maximum battery size I can fit, other than my taking some measurements and going as large as I can.
Meanwhile I have ordered a digital voltmeter off eBay to fit on the dash, so I can get a reminder of the situation whilst in use, should be able to find the minimum voltage I can drop to and still start the vehicle.
 

Graham

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Hi Phil,

When you are going to do load tests on your alternator, there is no need to rev the balls of the engine.
Makes very little difference.

I would say that by the time the engine is revving at about 1300 rpm, than that's more sufficient to allow the alternator to develop full output.

Gra
 

Chris Green90

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Hi Phil.

I am sure the alternator on the diesel is 90A output, When mine packed up recently I upgraded it for the larger 120A model from a D4D engine. Not sure if they are the same on the petrols but may be worth looking into

Chris
 

Crispin

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If you standing with the engine running and the alternator cannot keep up the demand, adding a second battery will only give you another battery which will be flat.
Having a look at (random) alternator output curves on the 'net, they ramp up quite quickly from 1000RPM. Not sure what an alternator runs at when the engine is idle?

If you're using and extra 38A at idle, that's pretty far out from what would be normal so not really surprising that the alternator might not be coping? Maybe a brick on the accelerator? :lol:
 

sae70

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Due to my resent winch install I've a lot of time reading about the subject and one of the items that may be of interest here is that if you are using a winch with a single battery install then before commencing winching it is strongly recommended to increase the engine revs to 1500+ rpm so that the alternator can be of some assistance during the processes :icon-smile: I'm looking at cutting a little wedge that I can slip between the idle screw and accelerator cable cam to hold my engine revs up while winching :icon-smile:
 

BobMurphy

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I'm looking at cutting a little wedge that I can slip between the idle screw and accelerator cable cam to hold my engine revs up while winching :icon-smile:
My old Series III Landrover had a hand throttle - a lever in a quadrant-shaped gate - that was used when winching.

Of course, it was intended for the Capstan winch - which I had and was excellent.

It was positioned near the passenger footwell so that the driver couldn't reach it when driving (it wasn't a cruise control :whistle: ).

It simply rotated the throttle shaft slightly, it doesn't need much motion to gain a couple of thousand revs.

Maybe something simple along those lines would do the trick :confusion-shrug:

Bob.
 
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