Leisure battery draining

[mr_marrakesh]

Hi there, I have a Bongo with a professional full side conversion. The leisure battery appears to getting drained by something connected to it all the time. It seems to charge if you drive or hook up but quickly drains again after that. I measured it's voltage after turning engine off and could see the volts dropping quickly. If I do the same but disconnect the leisure battery after turning the engine off the volts on the battery stay constant implying something is draining it rather than it's dead. As far as I can tell there's nothing plugged in or switched on to make it drain.

We don't actually use the leisure battery much but it appears to be wired to the passenger door, sliding door and tailgate central locking so if it's flat and you try and remote unlock it only unlocks the driver door which is quite annoying. If the battery has some charge it will lock/unlock all the doors. Also the leisure battery seems to power the stereo.

Does anyone know of anything obvious I can check or am I going to have to take it to an auto-electrician?

Kind regards, Henry

[g8dhe]

You will have several circuits connected to the LB via fuses, if you have a swap loom in place to the original fuse box, then at least 4 fuses, start by removing the 4 fuses then use your meter in current mode and measure the current flowing in place of each fuse, this will then let you see which circuit is drawing the power, the 10 Amp fuse (original top left) will draw about 50mA as backup to the radio, ECU and any remote key fob, but the 2 blind circuits should not draw any current, and the Ancillary 15 Amp fuse (original top right) is most likely to be the problem with something drawing significant current like the radio main power or something plugged into one of the sockets etc.

[cmm303]

In addition to the normal 4 circuits swapped over to the LB that g8dhe mentions above, what in the conversion runs off the LB such as a fridge or inverter?

You say the LB voltage drops quickly when connected. Is that minutes or hours? What voltage? Battery AH?

[mikeonb4c]

When i read of battery power leaks i'm always inclined to suggest stemming the leak initially by using something like this:

https://www.amazon.co.uk/dp/B019XQRFNG/ ... 1xb9Z4C74A

You can then investigate the cause without feeling so pressurised to find it

Isolating the leisure battery during periods of disuse seems like good practice so these switches seem useful anyway.

[mr_marrakesh]

Thanks for all that info. I've had a chance to get under the bonnet with the multi-meter.

In answer to cmm303's questions: The LB drops from 13.6V immediately after disconnecting hook up to 10.2V in 15 minutes. Disconnecting LB and doing the same it drops to about 12.3V (what you'd expect?) and then stays there. LB is 110Ah. The fridge, water pump, internal LED lights run off LB, there is no inverter. Keeping all of these off the LB still drains.

Regarding g8dhe's points: There appears to be a swap loom. It is sitting over the starter motor battery but is wired in from the LB via a thing called a Votage Sensing Relay which interestingly was warm to touch (the engine hadn't run since the day before) and has 7 fuses.

From top to bottom they were:
1. 15A drawing 320mA (ancillary?)
2. 15A drawing 0mA
3. 15A drawing 0mA
4. 10A drawing 120mA (backup for radio?)
5. 25A drawing 0mA
6. 15A drawing 20mA (?)
7. 25A drawing 0mA (this one is wired to starter motor battery)

Inserting fuse 4 with fuse 1 in turns the radio on but inserting it with fuse 1 out doesn't.

So I'm guessing it's fuse 1 / ancillary that's the problem but where do I go from here? Also according to my calculations that's a total of 460mA which if we call it 0.5A should take 220 hours to drain a 110Ah LB. Could it be that the leisure battery is a bit knackered and therefore has a lower capacity meaning it can't cope with the 460mA drain on it? I'll do a test where I have it fully charged and then leave it overnight and test the voltage but I'm sure it would be so flat in the morning it wouldn't be able to unlock the doors.

[g8dhe]

That sounds very much like the case, an old / well used LB. However it also sounds like there might be some draw from the SCR as its warm, it might even be permanently on. The basic LB wiring setup is shown below;

[mikeonb4c]

Have you ordered an isolator terminal yet. If not you should. Then you can debate the clever stuff at leisure (no pun intended!)

[windywatson]

The voltage sensing relay is sensing the voltage across the starter battery supplied by the alternator. When the engine isn't running the relay doesn't operate. When engine is running & the voltage increases to charge the SB. The relay will sense the increase & complete the circuit allowing current to flow to start to charge the LB. If your voltage sensing relay is getting hot to touch & the engine hadn't been run for a while, I suggest you have found your fault. Something must be faulty with it & drawing current if its geting hot. You don't generate heat without putting in some energy from some where. The one I have fitted is all solid state, if yours is the same it is always possible that there is a component failing. To prove this you could leave your battery connected as is, but just disconnect the live feed from the voltage sensing relay that feeds the +ve 12v to the LB. Then keep checking the volt drop. When testing for these sort of discharge problems, I always disconnect the +ve clamp from the battery & switch my meter to amps & connect inline between +ve terminal & the +ve clamp. read off the current being drawn & disconnect indevidual CCTs one at a time until the culprit is found.

Cheers

[mr_marrakesh]

mikeonb4c, I haven't bought the isolator terminal yet. I do like the fact that it looks a bit like a plumbing valve but I've just been keeping my bongo hooked up whenever it's on the driveway to keep the LB charged up nicely. Which in point of fact is I think why the voltage sense relay was warm that time, because the LB had been charging via hook up. Should charging the LB via hook up make the voltage sense relay warm? When I've not been charging it isn't warm.

I've pretty much convinced myself that it's just an extremely knackered LB. From being charged on the driveway for a long period I unplugged and it went from 12V to about 4V in 5 hours drawing no more than 400mA which makes the LB have a capacity a lot less than 110Ah. So I think I'm going to get a new LB but I may also have a tinker around to see if I can find out what's drawing 320mA on the ancillary fuse.

g8dhe, your diagram seems to match what I have under the bonnet. Thanks for everyone's input.

[windywatson]

When the LB is being charged by the EHU if that is wired correctly it should only being applying charge to that battery. In my experiance (I have worked as an motor home technicain) I wouldn't expect the split charger to become warm. I'm just wondering if infact the EHU has been wired so that it is applying charge to the SB & as that charge is high enough the split charger is cutting in and charging the LB. That would explain the split charger being warm. This is all pointing to me that some investigation is required to find out exactly how your system is wired. You need to ask the installers of the conversion how they have wired it. I wouldn't have expected it have been wired in any other way than to charge the LB directly. I certainly don't have to keep my van on charge all of the time for the LB to not go flat. Mine doesn't get used for weeks some times & is still good.
You mentioned that the voltage dropped rapidly. It is always possible that you have one or more cell within the battery failing, I had a new Numax battery that went thay way within a couple of months. The best way to check the battery for any internal faults is to charge it, disconnect the battery complety & check the voltage regularly. A good battery after charge may drop after inital disconnect from charging but then stabalise at about 12.5/12.8v and should sit at that for many days if not weeks.
You may well be correct that the LB is U/S. However This doesn't explain the split charge relay getting warm when the engine isn't running though.

[mr_marrakesh]

Right, thanks for that windywatson. I think I need to do some thorough investigations and contact the installer (Celtic Motor Homes). I also should have searched the forum and fact sheets before I posted. I think I've got enough info to keep me going trying to find the problem now. Thanks all.

[Bob]

Ed is a top chap, you'll have no probs there.

[mr_marrakesh]

I left this problem unsolved for a while but have come back to it now.

I think the split charge relay had been warm in my original test because I had just previously been charging from the mains hook up. I haven't been able to recreate the warm SCR when I haven't been hooked up so I think that was a red herring.

I retested the current draws on the fuses more thoroughly and realised that they tend to be high for a few seconds when you first make the circuit with the current meter and then drop a bit. Bearing this in mind after the levels have dropped the total draw on the leisure battery when nothing is on is about 200mA.

I bought a Numax LV22MF 75Ah leisure battery and some quick release terminals and this hasn't run out of juice yet although I haven't gone more than two days without driving it. I reckon with a draw of 200mA it should take over a week to lose half it's charge so I think I can live with that and I'm not going to do any more investigations.

Thanks for everyone's help.

[mikeonb4c]

Glad its sorted and thanks for the update. Quick release terminals makes good sense. After all, we turn off the tap on a calor gas bottle when not in use, and for similar reasons.