Leisure battery capacity

[Hughesy1982]

Hi guys,
I'm looking at wiring a split charge relay kit and leisure battery to my 1.9dg but I'm not quite sure what size (ah) battery to go for. For obvious reasons I want to get as big as possible and the place I have in mind for it has more than ample space to cater for a larger battery. My query is could I add implications to my alternator if I go for a battery of a large capacity? I was thinking perhaps a 120 or 130 ah battery to run my compression fidge and basic sound system for nights away.

Thanks

[Mocki]

all you need to remember is that the wiring and split charge relay must be rated big enough for the current being expercted, so forget those weak voltage sensing things, and look for a 140a traditional auto relay and good quality connectors and fusing

[syncroandy]

Also... I have found the D+ / alt. charge output on some alternators (eg. Subaru) cannot always supply enough current to trigger a beefy split-charge relay. My workaround was to use a second relay with a transistorised trigger circuit to switch the main split-charge relay.

[Oldiebut goodie]

all you need to remember is that the wiring and split charge relay must be rated big enough for the current being expercted, so forget those weak voltage sensing things, and look for a 140a traditional auto relay and good quality connectors and fusing

120A and 140A voltage sensing relays seem to be the norm now. Those 30A ones are aimed at the shed draggers mainly, although they can be used to switch a hefty relay themselves. The good thing about them is that they are usually adjustable unlike the big vs relays.

[Hughesy1982]

Thanks Guys,

My worry came from a friend of mine who has t4 and decided to fit a 150ah (I think) battery. This fried his alternator as it wasn't man enough to charge both batteries. In the end he shelled out £500 for an uprated alternator which solved his issue.

[Oldiebut goodie]

There must have been something seriously wrong for that to happen. My Mercs alternator at 70A is perfectly happy with charging 360 Ah of leisure and starter batteries.

[Hughesy1982]

Ok great 360ah here I come

Thanks for your help guys

[California Dreamin]

It'll work harder for longer, get a bit warmer and in turn wear out bushes and slip rings more frequently, which might make the alternator less reliable long term but not necessarily kill it outright.
I think most issues would be around the initial high current draw after a weekends camping. Better get a 100 - 120 watt solar panel fitted as well.

Martin

[Hughesy1982]

I was thinking of getting one in the not to distant future to keep the battery topped up over weekend use.
Thanks for the advice.

[Mr Bean]

The only trouble I have had with my relay switched leisure battery set up is blowing the 30A line fuse if somehow the leisure battery get completely flat. I have thought of connecting the Alternator feed direct to the battery but prefer to have a fuse in this line for safety. The Alternated is rated 90 Amps by the way and at times will of course be charging both vehicle and leisure bateries.
CS