best dual battery set up

Submitted: Monday, Mar 06, 2006 at 05:41
ThreadID: 31457 Views:2153 Replies:6 FollowUps:6
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anyone ever tried putting a second alternator in a Prado 120?
(imho this is the best dual bat system as immediately the engine is started both batts are getting the charge they need - much faster than anything thinks...?, had this set up once b4 in a landy & it was great)
please correct me if necessary

PS; also gives a second alternator in case main one fails


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Reply By: Derek from Affordable Batteries & Radiators - Monday, Mar 06, 2006 at 08:15

Monday, Mar 06, 2006 at 08:15
Hi Steve,

Not much space in the newer 4bies. I would rather go solar as this gives you the abillity to charge while camping and will also help you out if the alternator totally fails. The Toyota warranty could also be voided if a 2nd alternator is fitted.

Regards Derek.
AnswerID: 158831

Follow Up By: Member - Doug T (QLD) - Monday, Mar 06, 2006 at 10:58

Monday, Mar 06, 2006 at 10:58
Ohhh Noooo Derek
here we go again on Alternators...?? LOL
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Follow Up By: Member - Craig M (VIC) - Monday, Mar 06, 2006 at 17:23

Monday, Mar 06, 2006 at 17:23
Hi Derek.
I've recently bought a 2003 Prado GX (V6 petrol), and want to put another battery under the hood. It looks like the power steering resevoir will need to be moved - do you know if this is the case? I am concerned among other things about voiding the warranty (but will talk to Toyota bout that).

FollowupID: 413427

Follow Up By: Derek from Affordable Batteries & Radiators - Monday, Mar 06, 2006 at 17:33

Monday, Mar 06, 2006 at 17:33
Yes it needs to be moved. It fits between the brake master and the air filter.

It is very easy to move and you use the exsisting pipework and bracket.
FollowupID: 413429

Follow Up By: Member - Craig M (VIC) - Tuesday, Mar 07, 2006 at 12:27

Tuesday, Mar 07, 2006 at 12:27
Thanks Derek, I appreciate that.
FollowupID: 413568

Reply By: Ken - Monday, Mar 06, 2006 at 08:46

Monday, Mar 06, 2006 at 08:46
Steve, you are spot on with the 2nd alternator system, like you I had this setup in several older landies with Holden 6 cyl and V8's where is is a very straightforward task and with it never had a problem with the second battery.
Not so easy in a Proado I suspect or other newer, serpentine belted motors. Can't see why there would be a warranty issue but it could depend on how the addition was done. One way could be to fit a V belt pulley to one of the existing pulleys, aircon compressor, power steering or altenator, and run a short belt to the 2nd alternator. The other difficulty is there isn't much room under the bonnet in modern cars and not many places to hang the alternator from existing mounting points and in a position where it can be driven.
My only disappointment with changing to a Nissan was no 2nd alternator and no aircompressor !
AnswerID: 158833

Reply By: Member - Oldplodder (QLD) - Monday, Mar 06, 2006 at 08:58

Monday, Mar 06, 2006 at 08:58
Just a point of interest, was your old landie running maybe dual 40 amp alternators? What's your new prado running?
Are you doing a lot of winching and need the batteries charged as quick as you can?
Why not upgrade to something like a 120 amp plus alternator?

If camping, why not solar?
AnswerID: 158836

Follow Up By: Steve & Mish - Monday, Mar 06, 2006 at 12:50

Monday, Mar 06, 2006 at 12:50
Hi Oldplodder

The main alt was 50 or 55 amp and the other was 60 amp - given to be by a friend. It was very easy mount on the 3.5l V8 in the series 3 (1981 model).
Don't actually have the tojo yet but very keen on the 120 - not sure of its alt size, just need to find one I can afford (and sell our tribute)

We carried a solar panel for a while but sometimes found it a bit of a hassle to find somewhere to stow it, get it in the sun - but vehicle in shade (we should have had a longer lead), was worried that someone might pinch it if we left it in the sun in a campground while we went for a wonder. We don't have that old one any more but maybe there is a smaller modern one we should seriously consider.

The second battery is mainly for an Engel - no winching at this stage. It is just that dual alternators, I think, is the only system where the instant the vehicle is running, two batteries are getting the proper charge they need.

With a solenoid, if one bat is lower than the other it won't be charging nearly as quick as it could (I think). Also if second bat is flat and engine is run for too short a time, could flatten the starting bat!

While a smart system switches between the two batts, charging one at a time.
Also, I remember hearing that the smart systems don't quite get either battery all the way to 100% charge.

So if we were camped somewhere for a week or so, with 2 alts we could run the engine for a shorter time each day to keep the batts topped up.

I think maybe we'll have to look at a smart system (rotronics maybe) and an easy to pack solar panel.


FollowupID: 413386

Reply By: Mike DiD - Monday, Mar 06, 2006 at 16:29

Monday, Mar 06, 2006 at 16:29
I have a 120 amp Alternator as standard in the Pajero DiD - there is absolutely no point in increasing Alternator capacity - batteries are limited in how much current they can take.

Charging a battery too fast will just shorten its life.

AnswerID: 158907

Reply By: wheeleybin - Sunday, Mar 12, 2006 at 13:23

Sunday, Mar 12, 2006 at 13:23
Id like someone to explain to me what a smart charge system really is as I think the term is loosely used as there is nothing smart about diverting current where that current s still controlled by regulation that does not change and in 240V to me three stage charging is not smart if it uses fixed time parameters.
To me a smart charging system calculates the battery condition and charges it accordingly.
AnswerID: 160069

Follow Up By: Steve & Mish - Monday, Mar 13, 2006 at 00:06

Monday, Mar 13, 2006 at 00:06
hi wheelleybin

i'm an amateur in this regard so i'm sure there is better info to be had than i can supply, but.....

as i understand it there are basically two approaches to charging separate starting & accessory batteries with one alternator.

One is most commonly done with a simple solenoid (and timer i think), or sometimes done with electronics (the cheaper rotronics kit might be an example). So that some minutes after the car has been started, the second battery is automatically connected in parallel. The alternator then sees the two batteries as one for less than ideal charging.

The other "smarter" system only has one battery connected at a time. This might work with first the starting battery being charged, then being disconnected while the accessory battery only gets charged. While the system constantly monitors the starting battery so it is switched back in - on its own - if it falls to say, 70 or 80 % charge------- and 'round we go again.

I suppose this second example is referred to as 'smart' as it is more complex, expensive, and much better than a parallel system. thoughts anyway


FollowupID: 414821

Reply By: wheeleybin - Monday, Mar 13, 2006 at 07:46

Monday, Mar 13, 2006 at 07:46
Hi Steve thanks for the response.
You call yourself an amateur but your approach appears to be outside the square of amateur approaches as you are looking to find an efficiency solution rather than just accepting inefficient basic add ons to an existing inefficient system your vehicle or maybe you have inefficient adds on now and are looking to overcome them.
Make what youve got efficient first before adding anything else on and this not only applies to single alternators it also covers the duall alternator situation too because adding one extra you are still adding inefficiency due to the designed purpose of the alternator.

When you talk of the single alternator way with the smarter smart system you mentioned do you know of a specific product and have you information on that specific product because my idea is that is where you should start and once improved every add on then becomes a viable economic efficient enhansement.
Regards Wheeley

AnswerID: 160177

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