Thread: Dual Batteries

Hi numpty, KhunMoo and Bushie, if you like the manual switch method and remember to use it, so be it but CraigE already has an automatic set-up with his TJM that not only removes the need to switch between batteries but more importantly, it removes the need to remember to switch.

It’s a case of each to his own but I personally do not like any set-up that has the ability to disconnect the cranking battery from the alternator, even with marine battery switches that make-before-break when changing from one battery to the other. The potential is still there to accidentally go to the OFF position.

As I posted, if a manual switch set-up is for you then an ON / OFF battery switch that simply connects the auxiliary battery to the cranking battery without effecting the connection between the cranking and the alternator, is a much safer way to go.

Cheers

The only thing that concerns me about a smart DB system is if you drop a cell in your main battery and it does`nt acept full charge, your second battery will theoretically never get charged, leaving you with the possibility of 2 flat batteries, where as with a more primitive split charge solinoid this should never happen.

Hi cils110, that is a highly unlikely scenario as the cranking battery would have to drop the cell after starting because most DB controller work to protect either battery if the other is faulty.

So if the cranking battery had a faulty cell before you want to start, you just can’t start and your auxiliary battery would be protected by the DB controller.

If the cell did fail after starting then there is a good chance the auxiliary battery will still have some charge in it and if the failed cell in the cranking battery was that bad that it dragged the vehicle’s voltage down that much, the DB controller would cut out, again protecting the auxiliary battery and giving you the ability to start your vehicle off the auxiliary battery.


On the other hand, if you had your switch set to both batteries and were not aware of the failed cell, you would not have anything to protect either battery.

Cheers

A friend of mine that had been burnt in the past by DBS that control all charging was very happy to find that the new systems really just control the charging and operation of the second battery. This means it's unlikely they can cause much in the way of problems with the main.

I had a dissasterous fraser trip with my batteries, but after thinking about the events that unfolded and the causes I couldn't have really asked the DBS to do anything more than it did. The problem was insufficient charge from the alternator. There isn't much you can do to get around this.

Originally Posted by drivesafe

Hi numpty, KhunMoo and Bushie, if you like the manual switch method and remember to use it, so be it but CraigE already has an automatic set-up with his TJM that not only removes the need to switch between batteries but more importantly, it removes the need to remember to switch.

It’s a case of each to his own but I personally do not like any set-up that has the ability to disconnect the cranking battery from the alternator, even with marine battery switches that make-before-break when changing from one battery to the other. The potential is still there to accidentally go to the OFF position.

As I posted, if a manual switch set-up is for you then an ON / OFF battery switch that simply connects the auxiliary battery to the cranking battery without effecting the connection between the cranking and the alternator, is a much safer way to go.

Cheers

Know what you are saying, but don't know how you can accidentally turn it off, if you turn the switch through the top position each time. All it takes is a little bit of memory and some practice.
BTW, last year whilst away, two of the other Landrovers in our party had smart chargers of some description fitted (and no I don't know what type so I suppose this is a generalisation), and they both had trouble with the charger deciding it would rather put power into the already charged battery rather than the one which needed charging. A couple of times we stayed in the one place for three days and they had to go for a drive to recharge, and I did not ( all running 12 volt fridges). The only way one worked was to try and trick the system by driving with lights on to allow some sort of balance between 1 & 2.
The switch system which we use I believe is foolproof and only cost around $50 to fit and as I say has never given me any grief.
My opinion of course.

Well I must be honest and say I do truly like manually switched battery systems, as no amount of advertising could give me more work than the number of times people have either forgotten to set the switch correctly and have ended up with flat batteries or like you, have been out with others, who have forgotten and in the middle of nowhere, had to be jump started after few days camping.

As for having to trick the DB controller to charge the other battery, there is only one make of DBS that would suffer from that problem and ironically they are one of the dearest, so just goes to show, you don’t need to spend a fortune to be able to get a fit and forget piece of mind type DB system.

Cheers.

i have a manual and have forgotton twice to connect the batteries back together, lucky for me it has never left me stranded, i wonder if the solar panel saved me, nah

Originally Posted by drivesafe

Hi cils110, that is a highly unlikely scenario as the cranking battery would have to drop the cell after starting because most DB controller work to protect either battery if the other is faulty.

So if the cranking battery had a faulty cell before you want to start, you just can’t start and your auxiliary battery would be protected by the DB controller.

If the cell did fail after starting then there is a good chance the auxiliary battery will still have some charge in it and if the failed cell in the cranking battery was that bad that it dragged the vehicle’s voltage down that much, the DB controller would cut out, again protecting the auxiliary battery and giving you the ability to start your vehicle off the auxiliary battery.


On the other hand, if you had your switch set to both batteries and were not aware of the failed cell, you would not have anything to protect either battery.

Cheers

Yes mate, you are right, it is not a normal scenario, and would probably never happen.