Club 80-90 Forums

Ok a couple of things I wondered now my leisure battery system is kind of in now.

Firstly is that the Rolls AGM 145AH (C20) discharges pretty quickly and I am wondering if i've made a mistake somewhere;

https://www.flickr.com/photos/134122268 ... ed-public/" onclick="window.open(this.href);return false;

Above it how i've wired it in relevant to the Sterling/ the loads and the placement of master switches.

Now if I brim the leisure battery and leave it an hour or so out with the right hand switch in the drawing switched off it will state around

12.80V SOC. Now I think that is what it's supposed to be with an AGM type battery. At first it says near 13V and drops fairly quickly to 12.8V.

There it settles but if I go to test it in 2 or three hours I will be reading 12.75. 4 hours probably 12.70; left overnight it would probably discharge to 12.65. Now this is with the switch from Leisure positive to Loads in (off) position. So I can't work out why is the battery discharging? I just double checked there is definitely nothing attached to positive of leisure battery when the switch is off. All negative connections are still in circuit.

So firstly is this a sign that something is wrong with the battery?
Could a battery lose charge through the negative terminal only? (I am pretty sure this is a stupid question )

Secondly on a fairly low thermatic setting such as 15 degrees centigrade or 1 red mark on my webasto controller how long should I expect my battery to reach 50 percent SOC with the Webasto left on at this setting. At the moment I am getting only 3 or 4 hours until the battery reaches 12.30V (when disconnected and left an hour to come back up.)

To me this seems bllocks and not at all what I should be getting.

Any advice opinion most welcome but I am starting to think this battery is up the swanny!

Doesn't sound much wrong to me....0.15 volts settling after charge, remember 12.65 volts is still regarded as 100% charge state and batteries will hold on to a 'residual' (slightly higher voltage state) for quite a few hours before finally settling down to true standing voltage.
As far as voltage drop is concerned....down to 12.3 volts after 3 - 4 hours! well that's still around 68% and then I'm betting if you turned off the heater and let the battery recover for 15 minutes, that 12.3 volts would be something like 12.4 volts SO....around 80% charged.
Then there is temperature and how it effects charge....it all gets a bit complicated.

So 20% discharge over 3 - 4 hours hmmmm Whats the Webasto use? 1.1 amps continuous, 8 amp initial?


Martin

Pretty normal sounding to me also.
Draw of a Webasto STC doesn't vary much according to the heat output, specs are 14 to 29 w running over the heat range. I see up to 12A on immediate switch on down to 8A glowing during the start up phase on the ST models.
Don't forget that the draw can still be at the higher end if the input air is so cold that the heat output is not reduced.

My webasto will reduce voltage to 12.3 after 3 hours continuous.
After 9 hrs continuous it's down to 12.0v