Thread: Additional Battery Setup - Not your usual system

A modern 12volt 85 to 130 amp alternator can be sourced relatively cheaply from 90's Commodores, all you need to do is swap the pulley. I personally have been using a semi-deep cycle Besco Extreme battery, part no. N70EX, it has been in continuous service for nearly 8 years. It may not be the most suitable for frequent deep cycling but is very robust and capable of being topped up. If I had 2 new batteries I would leave them in parallel permanently. The amp hour rating of any lead acid battery is highest with the lowest current draw. Also the lifespan is best with a lower total depth of discharge, so drawing both down at once gives the longest life.

Im a big fan of a lot of smaller batteries of the same type in parallel. Its usually cheaper in terms of the batteries and if you kill one you can easily drop it out of the system and still maintain some functionality.

Dont forget to make sure you have isolation of the right type on the new alternator when you get it and dont make it too big if you are going to run pure deep cycle batteries, While they can take a high current charge they last a lot longer with a lower current.

I bought a single SuperCharge 105 ah dual purpose cranking/deep cycle battery. It will be charged by the spare alternator when in the vehicle and a 2600mah charger/trickle charger when at home. The only hard wired appliance is the analogue clock. Plug in appliances will the camping usuals - fridge, lights etc.

So the question is - when out camping etc what is the minimum safe voltage I can let the battery go down too before either switching appliances off or recharging the battery. Also any idea what sort of Ah would have been used from fully charged to the safe voltage.

If this battery works out I will get another and then work out the best way to connect them together.

Thanks

Garry

Garry

Look into CAT 6v batteries and run them in series.... You'll get a ridiculously long run time from them

Hi Garry, and to start off, your 40 amp 12v alternator is the equivalent of a 60 amp alternator in a single alternator set up because yours is not power the vehicle’s fundamentals.

So you may not need to be in too much of a hurry to replace it until you see if it will or will not meet your needs.

Next if you are considering using an electric winch, if it draws more than 30 or 40 amps ( not sure about the current draw of your portable winch ) you need to fit cranking batteries.

Under normal use, dual purpose type batteries are an excellent choice but when high current winching is going to be done, deep cycle batteries can’t be used and I would not even use a dual purpose battery.

For the best all round life span of your batteries, permanently parallel for all the reasons bee utey posted and it doesn’t matter whether they are the same size, brand or age.

If you use a deep cycle battery, you can safely take them down to 30% SoC and as long as you charge them as soon as possible, they should give you a good operating life span.

With Cranking batteries, you can take them down to 30% SoC but they will have a shorter life span so it’s best not to take cranking batteries much below 50% SoC.

This chart will give you the voltage reference to find out the rough SoC of your batteries.

Originally Posted by Tombie2

Garry

Look into CAT 6v batteries and run them in series.... You'll get a ridiculously long run time from them

Tombie - CAT have a 6V Calcium battery rated at 100AH that is very compact.

So if I join 2 of these in series I get a 12V 100AH battery ?

Cheers
Simon

Hi simonmelb, while using two 6v batteries in series will work perfectly, there are some potential drawbacks that you need to consider.

With a parallel set up, you can use any combination of similar or dissimilar 12v batteries to make up the amount of capacity you need and if any of the batteries play up, simply remove it. You can replace it when you get round to it or you can just leave the set up as is.

With a series set up, both batteries do need to be the same type, size, age and preferably the same brand.

In a series set up, if one battery plays up, you really need to replace both batteries or at least get exactly the same battery to replace the failed one.

Furthermore, while you source the battery, you will not have any 12v stored power and if you happen to be on that big trip around the paddock, you may find it next to impossible to get an identical replacement for some time.

Back to a parallel set up and if you do in a battery in, in the middle of the never, never, the first servo, K-Mart, Woolies or what ever, that you come to, you can buy ANY 12v battery and your up back to your normal capacity.

One more point, if you find that your existing battery capacity is a bit small, it's a lot easier ( and cheaper ) to expand a parallel set up than it is to expand a series set up.

Thanks Drivesafe

Makes a lot of sense ! - Im just looking where I can store 100 or 150 AH (or more) in my D2a for a big trip. I havnt decided whether to use the rear storage bins, under bonnet. I do like the parallel setup idea. I have a small generator as backup.

Cheers
Simon