FAO GRAZY - Leisure Battery/Split Charge

[zkot]

Ok guys, heres the thing. Mate of mine has 2 batteries running in parallel and so only has one fuse box....not sure if he has the relay in place...! Is it possible to just wire across from one battery to another, + to +, - to -. Will this work or will something blow up?

 

[NeilG88]

First off... Hi from the forum newbie!!

Has anyone used this type of smart relay? If so where did they mount it and did it work?!
Love the site, been a regular visitor but never felt the need to post until now!
Cheers!

 

[Todster]

Hi Zcot,
Welcome, I am also a noob to earlybay, but am returning to the VW scene after a long layoff (15 years) You're thoughts about connecting two batterys together + to + and - to - reminds me of a generator failure years ago on our bus the night before we were due to set off for a 2 week surf trip to Ireland. At the time I worked for a Tyre company and we ended up paralleling up 3 massive tractor batterys borrowed off the company in the old bus (took out the cool box of the dormobile) ended up driving 2 weeks around Ireland without charging (disconnected the generator and ran off the batterys) - so it can be done. Make sure to use cable of correct rating (great big stuff) to connect all the batterys together. All that happens is that, in effect, you add the AH ratings of the batterys together. Seem to think, if I remember rightly, we ended up with something like 900 AH!

Todster

 

[froggy]

I run this new type of relay and i'm not totally convinced by it.
I have issues with the relay not switching off even with the ignition off.
The feed is from the start battery / alternator into the relay and then from the relay to the leisure battery. But because the relay will always see a voltage above the cut off voltage of the relay then it will always be energised and trying to charge the leisure battery until the start battery voltage drops and then the relay will cut out, but then with no load the start battery voltage picks back up and energises relay etc etc causing the relay to chatter. This is what happened to me at bus types and in the end i pulled the in-line fuse from the start battery to the relay, now thinking of re-wiring it via a old type relay that so that it requires an ignition input to turn the relay on.
Anyone got any other ideas?

 

[Joval]

I just fit a relay (30amp) as in Moby's diagram. It works well so why not?

What is the switching voltage of the 'smart' relay? Should be 13, no?

 

[froggy]

Yeah think it is around 13v, but if the start battery is above 13v (which a good battery should be) then the switching relay is permanently switched.
Think i'm going to go for a 30A relay as in the original drawings

 

[Joval]

12.6v is a full charged battery.

 

[froggy]

Was hunting around in the garage earlier and have found a couple of 40A relays, so guess what my weekend job will be :lol:

 

[slammedresto]

ive got a voltage meter on my leccy panel with my zig unit, but im told im best to use an amp meter to monitor the leisure battery so i can see how much is used and avoid draining it to far.

Any ideas where to get one from, also seen something caaled a shunt, which im told i might need?????

all a bit confusing, and ideas?????????

 

[Araon]

amp meter or ammeter can be purchased as a dash instrument from the usual autometer suppliers or from a hobby/electronics shop, the shunt resistor is used to drop the current through the meter as most meters will only handle low current in the region of milli amps or thousanths of an amp then a simple piece of ohms law will get you the true reading not accounting for the loss of the meter which again will be in the region of milli amps which is negligable for your applications.....

Obviously the dash version will have a shunt installed and be roughly calibrated, usually a zero centred jobbie with a few graduations so a rough guesstimate can be achieved.

Oh and the ammeter is in series with the circuit path i.e. break the line that you want to measure and the shunt will need to be in parallel with the ammeter.

 

[Araon]

Or forgot all about these

http://www.maplin.co.uk/Module.aspx?ModuleNo=46931&TabID=1&C=SO&U=strat15&doy=search" onclick="window.open(this.href);return false;