Thread: Dual battery/Isolator Help!

Hi Bruiser, this is the area I specialise in so check out my web site and see if there isn’t a set up to meet your needs.

While the kits are already discounted, there is a 10% AULRO discount on individual components

Traxide Tronics

Originally Posted by bruiser69

Hi All,

I have recently purchased a second hand Camper Factory Modcon Camper Trailer equipped with dual 130HR Trojan deep cycle batteries.
These connect to my Disco 2 TD5 via 50A Anderson connector.
What is the best (and cheapest) dual battery/isolator that I can utilise to ensure that my primary starting battery is fully charged , as well as fully charging and isolating the dual deep cycle batteries.

Cheers..Bruiser

I picked up on the "fully charging" and the fact that the batteries are going to be a fair way away from the alternator.

Assuming that the alternator is bog standard and designed to charge lead acid wet cells you will never "fully charge" your camper batteries under normal driving conditions.

A car alternator is not designed to fully charge the car starting battery in the first place, and the voltage drop across the distance between the alternator and the camper battery also needs to be taken in account.
There is heaps of information available on the web about all of this.

The bottom line is that there is no cheap option. You can do it, but it will cost you.

The ideal way would be to use a smart charger that senses the voltage at the camper battery and supplies the correct charge based on that voltage.

I will have to invest in a solar panel when I eventually upgrade to a compressor fridge, so keeping batteries charged should be taken care of (providing not to many cloudy days).

Originally Posted by miky

A car alternator is not designed to fully charge the car starting battery in the first place, and the voltage drop across the distance between the alternator and the camper battery also needs to be taken in account.
There is heaps of information available on the web about all of this.

The bottom line is that there is no cheap option. You can do it, but it will cost you.

The ideal way would be to use a smart charger that senses the voltage at the camper battery and supplies the correct charge based on that voltage.

Hi miky, sorry mate but this is nothing more than a myth, put out by people who have a vested interest in getting people to believe this, so they can sell you some wonder device that will fully charge the battery.

Trouble is that most of these wonder devices do NOT work as well as your alternator.

Hi bruiser69, I specialise in designing and supplying dual battery set ups for all manor of operations, including yours.

What you have to do is work out how you are most likely to use the camper trailer.

Are you planning on going away every weekend or are you going to be doing a long trip every few months and so on. Your planned use is what will govern what you need to do to get the best out of the set up you have.

If you are planning to do a long trip then you need to decide how often you are going to be staying at powered sites and how long you are likely to be away form civilisation.

And the most important consideration, is how long each day’s drive is likely to be. This last requirement has the greatest effect on how you need to look after your batteries.

If you plan to stay away form powered sites for long periods of time but will be doing, on average, at least 2 to 3 hours driving a day, you can easily use you vehicle’s alternator to replace the bulk of the battery power you use while stopped each night.

Originally Posted by drivesafe

Hi miky, sorry mate but this is nothing more than a myth, put out by people who have a vested interest in getting people to believe this, so they can sell you some wonder device that will fully charge the battery.

Trouble is that most of these wonder devices do NOT work as well as your alternator.

The man is right. As an Electronics Engineer I will side with DriveSafe.

I must add that I don’t know DriveSafe nor have I purchased any of his gear, but everything I’ve seen him post here has been on the money. I have looked at a few of the kits and for the $ they are good value.

The "Smart Chargers" available for automotive fitup do nothing, they can’t "boost" high enough to be effective (limited to the alternator voltage) – the 240v smart chargers ($400 up) are a different matter.

REMEMBER – that the TD5 runs at a higher voltage than the average Jap cars or D1 (but the fact there’s 260ah to absorb it may save you) so be sure to check the fluid in the Trojan batteries, even though they are a good battery they are not the best to suit the higher voltage.

Originally Posted by harlie

REMEMBER – that the TD5 runs at a higher voltage than the average Jap cars or D1 (but the fact there’s 260ah to absorb it may save you) so be sure to check the fluid in the Trojan batteries, even though they are a good battery they are not the best to suit the higher voltage.

Out of interest, what voltage do they generate? Are they designed for Lead Calcium batteries?

Would the wiring back to the trailer have enough voltage drop to bring the alternator voltage back to an appropriate level (yes, I realise the voltage drop will be dependant on the charge current).

Originally Posted by p38arover

Would the wiring back to the trailer have enough voltage drop to bring the alternator voltage back to an appropriate level (yes, I realise the voltage drop will be dependant on the charge current).

Hi Ron, they charge at up to 14.7 volts and for most battery set ups this is not a problem and for auxiliary batteries mounted elsewhere in the vehicle or trailer, not only is there a voltage drop, no matter how small but because the battery is not in the engine bay, it will be cooler and this means it can tolerate slightly higher charge voltages.