Dual Battery Management System Vs Manual 3-way Switch System

Submitted: Wednesday, Mar 26, 2008 at 12:16
ThreadID: 55933 Views:5740 Replies:9 FollowUps:2
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Me again

I know there's a lotta views out there about this subject; but what's the Pro & Cons of a simple 3-way Switch (mostly fitted on boats I believe).
I know there's been a lot said about this subject & I've read most of it. It's the simplicity of the 3-way switch that attracts me. Let's say I THINK I wouldn't mind having to remember to "switch over & switch back" (big note staring me in the face!). In the most basic terms, how do cabin-mounted switches work in reality?
Treat me as a complete novice.

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Reply By: pepper2 - Wednesday, Mar 26, 2008 at 12:42

Wednesday, Mar 26, 2008 at 12:42
I have had two popular electronic battery systems fail over the years,changed to a manual switch,so far works faultlessly.BTW if you wire the batteries in parallel and fit a cut out device on the fridge you may not NEED any switching at all as the batteries are never drained below the cut off voltage leaving heaps of energy to start vehicle.

Other advantage of batteries in parallel is longer life i have the original starting battery in my patrol from 2002 still going.

If you have electric winch this may not suit i have hydraulic winch.

In my view electronic isolators are un necessary others will give differing views.
AnswerID: 294806

Reply By: Jim from Best Off Road - Wednesday, Mar 26, 2008 at 13:05

Wednesday, Mar 26, 2008 at 13:05
If you have even a slightly suspect memory invest the $120 in a Redarc Isolator. Yes they can fail, but can be manually overidden so it is not a life and death issue. If they do fail, they still protect the start battery, you manually override it to charge the aux batt.

I recommend Redarc for one good reason. My first one failed and it was out of warranty. I mailed it back to them and had a brand new replacement, at no cost, within three days. You can't ask for fairer than that.


AnswerID: 294807

Reply By: new boy - Wednesday, Mar 26, 2008 at 13:08

Wednesday, Mar 26, 2008 at 13:08
I have a dual system in my Patrol put in by the 24 volt man that works on our crayboats . The new auxillary battery runs everything on the vechicle the oringinal battery is just for starting only. The auxillary battery is getting charged 100% of the time, to charge the starting battery there is a switch inside the cab which then diverts the charge to the starting battery .Should the Aux be flattened the cab switch can be held down which links the 2 battery giving ignition from the starter to the aux and you can start. I have done a lap no porbelms all I did on a long legs was charge the starter one for couple of hours this I only did about once a month .Should you forget to charge the starter your memory will be jolted with a sluggish startup.
AnswerID: 294808

Reply By: Member - Phil G (SA) - Wednesday, Mar 26, 2008 at 13:28

Wednesday, Mar 26, 2008 at 13:28
I currently use a switch between twin N70 Exide Extreme batteries. I keep it switched on all the time. Over easter, I ran two 40l engel fridges from the twin batteries, and the voltage never dropped below 12.53v, but we were driving every day. So I didn't even need to isolate the batteries.

To do it this way, the batteries need to be identical, and are best bought in pairs. If one battery were to suddenly fail, you'd end up with two dead batteries, so its not a good system for a lone traveller. But the upsides are that its very simple, and its less stress on each battery.

I also have used electronic isolators, and they are a set and forget device. You should always be able to to start your vehicle. Just monitor the second battery voltage to know whats going on.

While we were away, someone had an isolator fail - caused the voltage to drop to 5V on their auxillary battery - not good. To fix it, we bypassed the isolator, recharged the battery with a days driving, and left it paralleled.
AnswerID: 294809

Reply By: pepper2 - Wednesday, Mar 26, 2008 at 14:09

Wednesday, Mar 26, 2008 at 14:09
So of the few replies so far we know of FOUR electronic isolators failing ,,,,,think ill stick with parallel wiring and simple set up.
AnswerID: 294815

Follow Up By: Member -Signman - Wednesday, Mar 26, 2008 at 15:05

Wednesday, Mar 26, 2008 at 15:05
That's 4 failures...I wonder how many haven't failed ??

FollowupID: 560728

Follow Up By: Sand Man (SA) - Wednesday, Mar 26, 2008 at 17:43

Wednesday, Mar 26, 2008 at 17:43
But on the other hand, isn't an isolator failing better than a battery failing???

My electronic Isolator (Piranha DBS150) has performed without a problem for 6 years or so.

During that time, I have buggered two auxiliary batteries by allowing them to drain too low, too often. This was my fault and not that of the Isolator. In fact the Isolator provided protection of the starting battery by keeping it electrically isolated from the auxiliary so it won't drain down regardless, so the isolator has done the job required of it.

I now use a cutout device to protect the auxiliary battery from over-draining by heavy use. (Fridge, etc.)

With a "dumb" isolator, or a simple switch, you need to rely on yourself to switch off the parallel connection to stop the starting battery from being drained.

Even worse, in a simple parallel type connection of two batteries, any fault in one battery will cause disastrous results with the other. The result could be two dead batteries and you are in deep doodoo.

Simple decision for me.


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FollowupID: 560744

Reply By: Smudger - Wednesday, Mar 26, 2008 at 14:42

Wednesday, Mar 26, 2008 at 14:42
I am a huge fan of the manual switches. One time I spotted dripping green coolant when I lifted the bonnet to isolate the battery at the end of a stinking hot day in the remote outback. In the cool of the evening I got to fix what was a very small leak, that could well have become a very large headache next day.
Same goes for the morning routine of lifting the bonnet to re-engage the battery, perfect discipline for a quick vital signs check of the engine ..oil, coolant, general look over.
4 years and more than 30,000ks out there, and the switch never let me down.
My current truck has an automatic isolator, but I'm now in that daily routine ..hopefully the electronic gizzmo won't let me down. If it does I'll probably replace it with a manual boat switch.
AnswerID: 294822

Reply By: Mainey (wa) - Wednesday, Mar 26, 2008 at 18:01

Wednesday, Mar 26, 2008 at 18:01
get a quality built Electronic battery isolator and you can FORGET about the battery system altogether.... how simple is that !!

I originally had a redarc (mechanical solenoid) fail, so replaced it with a Piranha Electronic system, upgraded to Rotronics Electronic, no hassles in about 8 years.

(will be all reasons you can imagine given for both sides of the 'argument' - just remember the "manual switch" relies solely on you - the Electronic system is fully automatic)

Mainey . . .
AnswerID: 294852

Reply By: Member - Davoe (Yalgoo) - Wednesday, Mar 26, 2008 at 18:36

Wednesday, Mar 26, 2008 at 18:36
Yea had solonoids both mine and work vehicles never again. the irst you know a battery is stuufed is when you cant start it. Part of your pre start with the manal switch is startin on 1 battery then the other. You pick up straightaway a dodgy battery and can keep it isolated.
Oter thing is you would have to forget to isolate theswitch for at least 2 days before flattening both batteries are you that forgetfull?
All the hardcore esploration vehicles Ive used have had manuel switches (cole hersy) and ive neve walked due to a flat battery so thats good enough for me
AnswerID: 294858

Reply By: Rumbler - Friday, Mar 28, 2008 at 15:23

Friday, Mar 28, 2008 at 15:23
Thanks everyone who took the time to express their experiemces.
I think I look into the RedArc system. Downloaded all files.
Thanks everyone.
AnswerID: 295249

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