grim

i been looking over the options here for multiple batteries.
what do you guys recommend using to separate them?
an isolator? a solenoid? what are the advantages/disadvantages.
i also just found a switch at a boating store. you can choose 1 or 2 or both batteries being used/charged. Its a Perko battery selector switch. any experience with them. My concern with the switch was that when both are selected could one drain the other?

My end goal is to have 2 bats charged by the alternator. 1 for starting. and the deep cycle for powering a 3000 watt inverter. but i dont want the discharged deepcycle to drain the starting battery.

G1625S

For what you want, the separator switch will work. Yes, when both batteries are connected, the weaker will draw the stronger down. Isolator will also work, it's kind of like a giant diode I think

grim

the switch may not be what i want then cause id like the weaker battery not to drain my starting battery. maybe the isolator?

also wondering about positioning. thinking about moving the washer fluid and putting the bat. there. is it ok that close to the turbo/exhaust?

JustRamIt91

The selector switch for boats are more for emergency purposes. They are deep cycle batteries and seem to hold their voltage better but quickly loose their cranking amps. I've had to use both batteries to get the boat started after playing the radio for too long on both 1 and 2 selections.... then by the time you get back to shore/dock your fully charged again. I ALWAYS switch to OFF when not using power.

I think there are several threads about isolators and solenoids to separate the batteries.

Also for battery location, i've seen a bunch of people using twin optimas mounted sideways in stock location. The seem to fit well and you need to make a custom box regardless, so y not put it there?

jimbo486

NE frmhnd

How about a breakaway kit battery charger then just put it on a toggle switch so you only charge it while the truck is running? Won't charging a deep cycle too fast burn it up?

Semi trucks used to run what they called a "3+1" battery system. They had three main batteries for the truck then a deep cycle for the accessories. I don't know how they hooked them up exactly but the deep cycle was tied into the mains, if your mains were dead you could switch the cables on the deep cycle for a jump start.

BearKiller

There is tons of good multi-battery info on many of the off-road Jeep and Bronco sites.

I would utilize that switch you have for the "self-jump" capability and either an isolator or continuous-duty solenoid for the isolation portion.

The continuous-duty solenoid method is probably the best.

BearKiller

NOTE that those two batteries are shown wired PARALLEL, which gives PLENTY of starting power, plus twice the reserve capacity.

However, not having them isolated, when one goes flat, they both go flat.


99% of big trucks have multiples of four Group-31s wired in parallel.

When you see big trucks that also have banks of isolated batteries, generators, 110-volt inverters, and such, that truck is owned by an individual and is not a company-owned truck.

grim

thanx for all the good info.
for the continuous duty solenoid. does it have the same function as the isolator? just different method? or what are the advantages of the solenoid over the isolator. ive read the isolators last longer.

BearKiller

It is usually the other way around; the isolator succumbs to heat and kills itself.


The isolator is just a big heat-sink box containing some sort of one-way electronic "check valve" that lets the alternators current pass through to both batteries, but will not let the current go the opposite direction; thus, both batteries (or banks of batteries) recieve alternator current, but neither side of the equation can deplete the other.


The continuous-duty solenoid just switches the alternator current ON to the reserve battery(s) when the engine is running; and, when the solenoid is OFF, no current can pass between the two circuits; thus, you can use the auxilliary batteries to a fare-the-well, while, so long as the solenoid is OFF, the starting batteries remain un-affected.

With isolated batteries, it is best to separate the starter to the starting batteries and have all the rest of the trucks electrics powered by the reserve batteries; thus headlights and such have no effect on the starting batteries.


I very much prefer the solenoid set-up.

BearKiller

YOU CAN just use that big switch to isolate the reserve batteries; BUT, you will have to select whichever circuit you wish to use and remember to set the switch to ALL batteries when the truck is running to recharge.


Doing it thus is perfectly fine when all batteries in the equation are good old Group-31s batteries; thus, you can simply leave the switch set to ALL batteries at all times and them behave as if they were simply hooked in parallel.

You would have ALL the cranking power for starting; whereas, in most isolated systems, some sort of heavy switching needs be done to use all the power for starting.


THEN, when you have reason to drain the reserve batteries and still have a HOT battery(s) for starting, just select whichever battery(s) you want to drain and when you get ready to start, switch to the HOT battery.


All manual and not quite so convenient, but it will accomplish the same thing.

Douglas2

hey-Hey!!!,
3kW will flatten a 12V battery remarkably fast. Divide 3000 by 12 and then divide again by the inverter efficiency to see how many amps it will draw. It will also take this load out at 120 cps ripple current which won't make the Pb-A battery any happier.
cheers,
Douglas

JustRamIt91

I have a "trickle charge" on the boat...they last 3-5 years.

BearKiller

Here is one guy's set-up :

http://chrisb.users.superford.org/Br...Batteries.html

Here is another good one, complete with a good diagram :


http://www.sleeoffroad.com/technical..._batteries.htm


Enjoy.

Bumble76

Not always true many companies have began using apu's and multi battery setups.