2 Dead Batteries

[skippymoss]

Hullo.
The van's not been moved that much for a couple of weeks whilst having bodywork type stuff done.
Cranking battery is now too low to start the van this evening; got that on charge now, read the Wiki and will get round to trying to find the drain sometime soon.

However, I've just noticed that the leisure battery is even deader - as a doornail in fact.
What I am asking is; if the drain is on the leisure battery circuit, should that be able to then suck the charge out of the cranking battery in order to carry on draining?
Even when the van's just sitting about?
If so, isn't this a bit of a design fault?
(If camping and running the battery right down, I would rather have no interior lights than no interior lights and no chance of going anywhere!)

Just a few added points;
- Had the van since May this year.
- Found 3 receipts for leisure system charging faults from spring last year.
- The fuse from the leisure battery had been removed when I first got the van, now replaced. (but maybe not for long)
- The bloke I bought from was wittering about new stereo draining the battery hence the crappy partially working radio going back in.
- Had no trouble over the summer but tended to hook up for a couple of hours before going anywhere to get the fridge cold.
Any comments/ helpful advice please?
Ta

[kevtherev]

you have a drain somewhere
do you have and know how to use a multimeter?

Stereos use a little to keep the memory alive but not so much as to drain a battery dead in two weeks in my opinion

Oh and NO the leisure battery and cranking battery are and should be separate when the engine is OFF

[DentedDevon]

Skippymoss , you have pm

[Reg the Wedge]

You definitely have a drain somewhere, a partial short to earth. Given the receipts for the charging faults and the missing fuse, you may have a couple of faults. First, the drain (I had a problem with a flip down TV/DVD player. In the end I fitted an on/off switch), that should be relatively easy to find with a volt meter or voltage tester. Secondly, there could be a problem with the charging relay. This should drop out, disconnecting the two batteries when it detects that the alternator is no longer charging and the voltage drops. If the relay is faulty the batteries will remain connected in parallel and will both drain.

These kind of faults are relatively easy to find, though sometimes harder to cure.

By the way, voltage testers are on sale this week at Aldi for £3.99!

[chriscburgess]

You definitely have a drain somewhere, a partial short to earth. Given the receipts for the charging faults and the missing fuse, you may have a couple of faults. First, the drain (I had a problem with a flip down TV/DVD player. In the end I fitted an on/off switch), that should be relatively easy to find with a volt meter or voltage tester. Secondly, there could be a problem with the charging relay. This should drop out, disconnecting the two batteries when it detects that the alternator is no longer charging and the voltage drops. If the relay is faulty the batteries will remain connected in parallel and will both drain.

These kind of faults are relatively easy to find, though sometimes harder to cure.

By the way, voltage testers are on sale this week at Aldi for £3.99!

How do you check the relay or do you just replace as a precautionary measure?

[kevtherev]

A continuity test usually confirms a simple gate relay or headlight relay.
There are usually four terminals on a simple relay
Two for the trigger (constant continuity) and two for the load (switched continuity)
switch on the item and check for continuity across the load terminals (thicker connector or wire to them)

[Reg the Wedge]

Although what Kev says is correct for most relays the usual, more modern, type of split charge relay is slightly different. You’ll have a + 12v input, the connection from the main battery, a + 12v output, the connection to the leisure battery (both thick red wires), and a – 12v that usually connects directly to the main battery negative terminal. This – 12v provides the circuit for the relay to detect the charging/non charging voltage. This needs to be accurate; hence it’s connected directly to the main battery negative. To test the relay, disconnect the +12 v output and test from this terminal to earth. When the alternator is charging you should get approx 14v. When it’s not charging and the relay drops out, you shouldn’t read anything.

There may be other +12v outputs, but these will be smaller diameter wires intended for a fridge, etc.

[skippymoss]

Thanks for your sensible replies everyone.
Meanwhile been out trying to approach this logically and in a scientific fashion...
(Easy to forget how difficult it is to be scientific in a carport in the dark)
Charged both batteries
Planned to remove the fuse from the carrier on the now charged leisure battery in the style of the previous owner as that had obviously worked for him
Turns out it had already popped - did another one just to check - that popped too
So I've got a problem there - left that for a bit and went onto cranking battery (like I say logical )
Disconnected the negative terminal from the cranking battery, stuck the multi-meter between battery -ve post and the now disconnected -ve Earth strap, and got a number (0.28 on 200mA setting).
Have no idea whether that is significant but suspected something to do with crappy radio as that was the last place I saw electrical sparks when I was fiddling with it
Went to disconnect the radio and saw that the little red LED was still on - turns out the radio's connected to the leisure battery
Made mental note that the radio has nothing to do with little fuse carrier
Disconnected terminals of leisure battery - red LED goes off - OK (see - scientific!)
Reconnected leisure battery and just for fun decided to see if I can pop another fuse - nope not this time - that particular problem has gone for a bit apparently
So went back to multi-meter on cranking battery and the drain's gone - just zeros on the multimeter now
Checked all the fuses in the glovebox in case a fuse had gone and taken the drain with it - nope
Wondered what a charging relay might look like for a bit and decided I wouldn't recognise the charging relay if I was pissing on it, so decided to lock up and do some more research on here instead
(“I have not failed. I've just found 10,000 ways that won't work.” ― Thomas Edison)
Maybe time to take up that offer of advice from someone who knows what they're doing

[DentedDevon]

Sounds "interesting"
Battery drains first ,
30 milli amps - no problems (0.030 A)
50 still OK
80 at the limit - you are now loosing 2 amp hours a day

Effective fault finding,
You have got to know what you are dealing with , which pieces of equipment are connected to what and exactly where the various relays , switches and fuses for each one are.
Measure the voltage at each battery (hopefully they will be different) so you know which battery is suppling the power, make notes or label wires with masking tape and build up a picture of what youve got.
On an old camper there are likley to be many "improvements" (bodges!) that have been carried out over the years.
When you have worked out what youve got the fault finding gets much easier.

Out of interest which battery do the original VW interior lights work off ?
Only they are on the same circuit as the VW radio feed.

[skippymoss]

The one for the sliding door works off the main cranking battery
Assume the drivers door does too
If you saw my carport you'd understand why I don't know about the driver's side!

[DentedDevon]

That sounds OK, I have seen it where the leisure battery feed to the radio has back fed to the cranking battery.

Has it got a "Zig" unit and if so what model ?
If it has a CF8 there is a switch marked Touring/site , in the touring position it simply links the 2 batteries for charging, regardless of whether the engine is running.
In the site position it connects the leisure battery to the charger. Ancient system intended for pre 1980 caravans!

[skippymoss]

Bloody Hell, what a numpty
This last bit has prompted a re-read of the manual.
"In order to save a drain on the main battery...it is best to set this switch to... 'on site' when the vehicle is stationery or garaged"

[DentedDevon]

[duffnutt]

Bloody Hell, what a numpty
This last bit has prompted a re-read of the manual.
"In order to save a drain on the main battery...it is best to set this switch to... 'on site' when the vehicle is stationery or garaged"

AAAARGH............ That could be why my battery keeps getting slaughtered! I have a CF8 memo to self read everything!

[skippymoss]

Glad I'm not the only gumby out there!