I'd like to fit second battery with split charger kit to my van and wonder what size/capacity other use and can recommend? Not sure what is the stock battery yet but I guess second one should be similar? Not gonna much energy just for laptop, cooling fan and lighting.

Id the second battery is going to be for things such as charging a laptop up and lighting ect you want to get a caravan/leisure type battery as these are better but for handing constant loads rather then a engine battery that's made for a large current over short periods

For maximum battery life, it is generally recommended that you do not discharge the battery by more than 50% of its nominal capacity.

A dual purpose battery which has engine starting capability, as well as being able to withstand a relatively deep discharge is worth considering. The Varta LFD95 is a popular battery of this type. There is a smaller LFD75.

For the split charging facility you will need a relay operated from the alternator D+ terminal which is often difficult to access. As an alternative you could use a small voltage sensing relay operated from an IGN+ supply, with its output driving the split charge relay. Examples https://www.ebay.co.uk/itm/New-12V-Relay-Voltage-Control-Delay-Under-Voltage-Protection-for-Car-Battery-UK/152604603429?hash=item2387f17425:g:Ya0AAOSwAXZa4ElD.

https://www.ebay.co.uk/itm/Waterproof-Automotive-Relay-12V-100A-5Pin-SPDT-Car-Control-Device-Car-Relays/152505187447?_trkparms=aid%3D1110002%26algo%3DSPLICE.SOI%26ao%3D1%26asc%3D225076%26meid%3De85fbecb99b942449ffb2aea7c86ac7f%26pid%3D100008%26rk%3D2%26rkt%3D12%26mehot%3Dag%26sd%3D152604603429%26itm%3D152505187447%26pmt%3D1%26noa%3D0%26pg%3D2047675&_trksid=p2047675.c100008.m2219

For safety please include 50A fuses close to both battery +ve terminals.

If your vehicle has an intelligent charging system, you could have problems which would need the expensive addition of a battey to battery (B2B) charging system, such as a Schaudt WA121525 or similar item.

offnote said:

I'd like to fit second battery with split charger kit to my van and wonder what size/capacity other use and can recommend? Not sure what is the stock battery yet but I guess second one should be similar? Not gonna much energy just for laptop, cooling fan and lighting.

Click to expand...

I don't see why it has to be similar. My motorhome has two 110ah leisure batteries connected in parallel which are charged by the alternator via an inbuilt split charge system. You could start with a single 85ah leisure battery and see how you get on.

One thing I forgot to add
You'd better off with a slightly lower capacity battery thats well made rather then a larger but cheeper made one



Cheep battery's rarely have the capacity they are supposed to

it really helps to read "a&n caravan services" site for good reliable independent advice, on batteries , chargers and vehicle alternator setups
,,,,please dont add 2x 110ah batteries charging off a standard alternator as when the van starter battery is charged the alternator will only output a float voltage that wont touch your leisure batteries at all -a 120amp alternator will be severely overloaded trying to charge 330 ah of batteries

madwrx said:

it really helps to read "a&n caravan services" site for good reliable independent advice, on batteries , chargers and vehicle alternator setups
,,,,please dont add 2x 110ah batteries charging off a standard alternator as when the van starter battery is charged the alternator will only output a float voltage that wont touch your leisure batteries at all -a 120amp alternator will be severely overloaded trying to charge 330 ah of batteries

Click to expand...

When strictly reviewed, this thread is more of a motor caravan matter, than a Fiat one. However as it is obvious that many of the forum members own older motor caravans, I think that is pertinant to add a few comments.

I cannot fully agree with some of the facts quoted above.

In older vehicles the alternator is regulated at about 14 volts or slightly higher. Within the capabilities of the alternator, this voltage is maintained irrespective of the voltage at the starter battery, and will NOT decrease when the starter battery is fully charged. I see no reason why the alternator will not continue to charge a second battery. (The 90A alternator on my 2006 2.8JTD does continue to charge the habitation batteries.)

In normal operation only a small amount of charge is taken from the starter battery when starting the engine. This is soon replaced.
The quoted figure of 110 ah for habitation batteries is based on a 100hr discharge rate. Current practice is to use the 20hr rate when quoting battery capacity. This gives a lower capacity of about 95hr for similar batteries. 190ah of battery capacity is not so frightening as the stated 330ah. I wonder?


On the other side of the argument there are pictures on "a&n caravan services" website of damaged equipment due to adding batteries without consideration of the additional current flows.