Dual battery management system

I have a tjm dual battery management system on my 07 wagon and its chewing up my 2nd battery it must be cooking the crap out of them they only last 12-18 months when the main battery last 4.5yrs , i only use it for my fridge or link up both for the winch (very rare). My question is what do i have to do to preserve the life of my axillary battery do i need to bush this system or do i need a isolation switch to stop over charging i think this system i have is crap any advice would appreciated cheers Eric

Not sure on the TJM system mate but a good battery management system should know exactly what charge the aux battery is and stop when It's charged and never overcharge it.

Hopefully someone who knows TJM gear can help out.

are you running the correct batteries ? if you’re putting gel or possibly some agm batteries under your bonnet the lifespan will dramatically decrease check with manufacturer specifications , also if your 2nd batt is next to your turbo you could try putting in a heat shield around it.
have you got a volt gauge on both batteries independently so you can see when the isolator is charging your aux batt and see what your aux batt volts are once it disconnects maybe its not getting enough charge and is getting damaged that way

If you flatten the second battery it probably doesn't get a chance to charge most of them systems are useless.
Personally i prefer a direct heavy solenoid and cables instead of a system that cuts in and out for hours trying to bring a low battery up in voltage.

i was using deep cycle batteries but lately just putting nz70 in her because there cheap, Its a tlm DBS system which has priority charging for start batteries but i don't think it has a cut out when second batt is charged , this system has no lights or gauges either , i do a lot of country miles charging should not be an issue . If anyone has a good proven system i'd like to hear about it thanks guys

Good proven system high amperage solenoid and heavy cable.
one switch to bypass and ignition on to activate.
Basically run the solenoid between the two positive terminals.
To activate the solenoid use ignition on wich will join the two batteries together when the ignition is on leaving them seperated when it's off.
And have a switch in cab going to earth this will be the bypass or disconnect the two even when the ignition is on.
Simplest design and it works like you would expect.

I run Zap deep cycle for Aux battery, the heat from exhaust ruined it, bulged both ends and the exhaust side, alternator charging correctly , advice I received from so called expert was they will handle the heat , not so , especially in the Pilbra heat, further advice was put aux battery away from heat source. now i find my van batteries deep cycle (Zap) one is stuffed. ( i run solar system in van all done by solar expert in Adelaide) Of the 5 batteries Ive put in 3 are had it,(main) cranking went as well and all less than 6 months old , warrenty not much good when your on the other side of the country. Next new aux battery is going on the tray, it cost me 3 kfor the van solar system 180 watts including batteries, and 1k for aux battery and anderson wiring .

It probably isn't overcharging as that will kill the Cranker as well. A huge percentage of Patrol Aux batteries mounted on the LHS guard die because of sulphation (under charging) or heat or a combination of both.

First thing to know is... Solenoid/Relay style Isolators (Redarc, Projecta, TJM etc ) WILL NOT (except in exceptional and very rare circumstances) control the charging of the vehicle batteries when the Alternator is running.
They WILL NOT ensure the Cranker is fully charged first
They WILL NOT ensure you have a fully charged aux
They can only be relied upon to do 1 thing and that is prevent the Cranker being drained below 12.5 volts with the Alternator off.

If you want your Aux battery charged correctly then the best alternatives are a multi-stage Battery Charger either 240 Volt (at home or in camp) or Onboard. The Onboard jobbies are also called DC DC converters or similar and are a voltage step up device and electronics to charge the Aux Battery.

Ctek, Redarc and many others make units such as the Redarc BCDC1220

Once you have your charging sorted out then it is time to address the heat issue and also the type of battery. Low Charge current AGM batteries such as Full River etc are not ideal for the LHS engine in a Patrol. Look at the battery specs and if the manuf reccomends a max charge current of say 20 amps select a different battery. The battery may be top notch brand and work gang busters as an Aux (I have 2 in my camper) but it is not suited to high engine bay temps and higher charge rates from an Alternator. There are many Deep Cycle AGM's suited for the application but not all of them by a long shot.

Anything you can do to reduce the heat soak into the LHS battery will greatly extend it's life regardless of battery type.

To sumarise...
1. the Solenoid/Relay Isolators will only isolate a Cranker from being drained by an Aux load and are good for bugger all else
2. the DC/DC chargers are the best solution to controlling the charging of the Aux (choose a manuf and capacity that suits you)
3. anything that protects the Aux from heat soak is a very good thing
4. if you don't use an onboard charger then regularly and also after every trip pop the Aux on a multistage charger at home and top it off

Here is a link to get you started, purely FYI http://redarc.com.au/products-and-se...tart-bcdc-1220

Hope that helps a bit

Hi guy`s
Having had some small issues with dual batt systems I opted for dual alternators some years back and have no issues since.
Just left the original system standard and the second alt charges second batt plus the 2 batts in the van.Have had no problems since fitting up this system which has been in service for around 10 to 12 years now. The batts I run are 75aph Optima marine deep cycle

theres no way ill fit a 2nd alt ive got a ctek dc-dc charger on the way should be here any time now

Well there you go i didnt even know a dc-dc chargereven excisted i will need to do some reserch on this product it sounds like the go also i will look for a good reflective shield for aux thanks guys :)