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Discussion Starter #1
Can anyone tell me what i need and how to set up a dual 12 volt batery system in my 88 suzuki samurai ?
 

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First question is WHY?

How you connect dual batteries depends on why you're fitting them.
 

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There's a few ways to do it but this comes to mind first:

Install a "Marine Battery Selector Switch"



If you plan to charge both at the same time while running then both batteries have to be equally in good shape otherwise one will draw the better one down.
If i had that switch and two different condition batteries i would charge each separately then always have the spare new one if needed or just run your extras off say battery 2 and switch to that mode when out in the wilderness.
Your post has me kicking around doing the same mod now.:)
Joe
 

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For winching purposes, hard wire both batteries together and upgrade your alternator - for auxiliary lights upgrade your alternator. The marine selector switch is nice, but 350A is a little underrated for a hard winch pull.

Oh - I forgot - you'll need both batteries to be the same type, capacity & approximate age. Paralleling batteries with different chemistries will result in charge problems, paralleling batteries with different capacities will result in the larger battery ending up with the same capacity as the smaller one, paralleling batteries of different ages will result in premature failure of the newer battery (yes - it will fail at the same time as the older one).
 

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Discussion Starter #6
i have the alternator from the sidekick right now, what kind of alternator would you suggest, and would i need some kind of isolator or just run the two batteries in a parallel, so i ground one and the power to the other one no isolator? or the marine switch would also run both batteries in a parallel? or both on a seperate line with two whole different +,-?
 

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Use google, find some offroad forums (try ZukiWorld), do some research and find out what you're getting yourself into, and what your options are.

The purpose of an isolator is to allow both batteries to be charged from the same charge source (alternator) whilst keeping them separate (or isolated) so the load on one does not affect the other - this is how you would set your batteries up if you wanted to use one as a "camp site" power source, for lighting, maybe run a 12v fridge, without draining the starting battery.

The marine switch will connect between the vehicle's electrical system and the two batteries - it will allow you to select #1, #2, both or none - select either battery by itself and the battery that's not in use will sit there, self discharge & eventually sulphate (unless you remember to periodically switch from one to the other - lead acid batteries do not do well when left idle, they must be charged at intervals) - the people I know who use that style of switch end up leaving it in the 1+2 position - which is the same as hardwiring the batteries together.

Both battery negatives are going to be wired to the frame/chassis - what you do with the positives will depend on how you choose to wire it - if you use an isolator, wire as per the isolator manufacturers instructions - there are different types of isolator, so pay close attention to those instructions - if you use the marine switch, wire as per the marine switch manufacturers instructions, and NEVER turn the switch to OFF with the engine running.
 

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1 big battery better than 2

I just use a single big Costco deep cycle Marine/Starting battery.
Had to remove the steel battery "compartment Flap thingy" to fit it in.
I go 6 hours running a bluetooth deck, amp and wakeboard speakers, bazooka sub, and a 7 amp waterpump (for the hot tub). and she'll turn over and start with no problems. go driving for half an hour and repeat...all day long!!
See below

https://www.youtube.com/watch?v=PUChKgZikAc[/url]
 

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Discussion Starter #9
ya i got the optima blue top deep cycle, but i need to run an warn winch,5 sets of off road lights, belly camera, plus the stereo and head lights, so i am looking for an easy dual battery setup.
 

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A dual battery system is not the solution to your needs - batteries are storage devices - they have a finite capacity, if you want to run large loads you need a high output alternator to supply them.

If you must run five sets of offroad lights, consider switching to HID or LED to reduce the amp draw.
 

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Im lit up like a Xmas tree.... but not one incandescent bulb is left on my vehicle. total draw of headlights, fog lights, driving lights rock lights reverse floods and step side lights is less than 15 amps.All LED and HID. But you are right. a winch would blast that battery pretty quick. I have seen on dude, with a dual batteries in parallel. One of them with a big switch on the pos lead. he would turn it on when he was winching, and when he was cruising on the highway. Off when he was 4x4in and camping. that way his "spare" was always ready to go.

As Fordem said, the proper way is to use a bigger alty, and I like a bigger batteries bigger than O' blue!!
Or get a battery isolator. most are set up to automatically switch the "spare" battery off and on automatically when current is avail to charge or when you need current to run your goodies, but will shut off with an alarm sound if voltage goes to low. But that gets pricey!

We have several service vans in our fleet that use these systems with mixed success.
 

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Something I think needs to be pointed out - there are different types of batteries - deep cycle batteries are intended to provide relatively low discharge currents (tens of amps), for relatively long periods of time (hours or days), starting batteries are intended to provide relatively high discharge currents (hundreds of amps) for relatively short periods of time (seconds or minutes, rather than hours) - the internal construction of these batteries is different, use either battery in the wrong application, and the end result is the same, reduced battery life.

http://d26maze4pb6to3.cloudfront.net/9513/4583/5023/BLUETOP_Full_Specs_Sheet.pdf

The link above will get you the Optima Bluetop battery data sheet - it is a marine cranking battery rated to deliver 800CCA (cold cranking amps), the quote below is taken from the data sheet.

These batteries are designed for engine starting applications. They are not recommended or warranted for use in deep cycle applications.
 

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Thats why I use the Costco Marine Start/deep cycle, as a happy medium.
I think I can get away with using it as a car battery as our starters are smaller with lower current drain than most cars and boats. I measured 90 amp draw while cranking cold, fuel pump fuse pulled. I think that is okay for this size of battery. kirkland signature 27DC. But I make sure if I am camping with no other trucks in the bush, I bring a small backup to jump start. Never had to use it...

specs.
Canada Kirkland Auto Batteries Summary - Costco Car Batteries List
 

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I don't know whose page that is but "reserve capacity" is not equivalent to the old "ampere hours" designation - they are different methods of measuring the same characteristic, just as liters and quarts are both measurements of volume.

It's also interesting to note that he quotes the Optima bluetop at 120 mins reserve capacity whilst Optima claim 100 mins in their data sheet.
 

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We could talk about how manufactures or anyone get numbers all day.... but I think we could agree that a bigger battery is not a bad thing.
Compared to the stock size Jimny battery, a bigger marine battery works well for me.
When I first got my rig, with all acces. on I could watch the battery voltage drop as I sat in traffic. 40 amp alty couldn't keep up. Since then I've got a big honkin battery and a 90amp alty. Problem solved. but only a bigger battery nor only a bigger alty wouldn't have solved that issue.
I went with a marine deep cycle because I knew I would be camping with the radio blasting for hours on end.
Whether or not MY battery could support a big winch..... I don't know.
I use a come-along and rope!
 

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When I first got my rig, with all acces. on I could watch the battery voltage drop as I sat in traffic. 40 amp alty couldn't keep up. Since then I've got a big honkin battery and a 90amp alty. Problem solved. but only a bigger battery nor only a bigger alty wouldn't have solved that issue.
Based solely on what you have posted a bigger alternator was what solved that problem.

I went with a marine deep cycle because I knew I would be camping with the radio blasting for hours on end.
That's what the bigger battery gives you.

Traditional explanations liken electricity to water, to make it easier for the lay person to understand - a battery would be the equivalent of a storage tank - let's say you have a 100 gallon tank and there is a pipe (your electrical load) draining the tank at 2 gallons per minute, that tank will be empty in 50 minutes.

Now let's put a second pipe (your alternator), this one is filling the tank at 1 gallon per minute, starting with a full tank, it will be empty in 75 minutes.

How do you solve the problem? A bigger tank (200 gallons) will take longer to empty (150 minutes) so that is not the solution, but a bigger fill pipe (2 or more gallons per minute) will - 2 gallons/minute out, 2 gallons/minute in, the tank will never be empty - you could even use a smaller tank, it will still never be empty.

Ideally you want an alternator that is larger than your expected load, that way there will be enough charge available to replenish the charge required to start the engine or used whilst the engine was off.

Winching is a special case because winches have high amp draw, higher than most available alternators, and winches are in most cases, not used for more than a few minutes at a time, so a high capacity battery with high amp capability is used to supply power and a high output alternator used to replenish the battery.
 

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I like the analogy,
However, lets say someone is having a shower, watering the lawn and flushing the toilet. High load, and you have a nice big fill pipe. BUT its only tricking water in, cause your water pressure is low. ie, sitting in traffic. Your pump is only putting out half a gallon at its current RPM.
I sure am glad I gotta big water tank (most of the rest of the world) on the roof to fill in the gap. or....if my pump breaks down...

So I agree with you...BUT even my bigger alty, at idle and all STOCK accessories on does not supply enough current to charge the battery
 

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BUT even my bigger alty, at idle and all STOCK accessories on does not supply enough current to charge the battery
At idle, the stock alternator WILL charge the batteries with the stock accessories on, so if your larger alternator won't, then it's possible that you're not using the best alternator for the job.

I can think of a number of different reasons, but the solution to most of them would be to change the pulleys to bring the alternator rpm up when the engine is at idle (either a larger crankshaft pulley or a smaller alternator pulley), assuming you have the room to do so.
 

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Discussion Starter #19
so what kind of alty do i need and where can i find one? how much? and would i need to fab a bracket or would it just bolt right in?
 

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Low Range Off Road offer a 78A GM alternator kit and the bracket needed to mount it - the GM alternators are also available from junkyards - the question however is how much power do you need.

It should be noted that you may need to change the alternator drive belt and all the pulleys (crankshaft, water pump & alternator) for a multirib setup, V belts tend to slip as the power demand increases.
 
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