Why is my engine battery flat when I have a battery master?

audlin

audlin

Joined
Jun 1, 2010
Posts
334
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Location
Hampshire
Funster No
11,881
MH
Micro campervan
Exp
Since 2012
After completing two weeks quarantine without using my van, I discovered today that the engine battery is completely flat. The leisure battery is fine, drawing from the solar panel. What I don't understand is that I have a battery master which " will only take power from the leisure battery, never the other way around. ... It is designed that when the engine battery drops half a volt below the leisure battery, Battery Master automatically adjusts the charge and tops up the engine battery." Any suggestions greatly appreciated.
 
Is it an Eddie VB battery master or something different?
 
Battery masters do work - I've got one. If your vehicle battery is flat either it has died or there is a fault in the Battery Master circuit. If you know, where the BM is check if an LED is glowing on it. :)
 
funflair said:
Is it an Eddie VB battery master or something different?
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Something different. I had my van converted to my spec and that was on the spec list. I hope I'm not misusing my terminology: Eddie VB did install a BM on my motorhome a few years ago before I downsized.
 
DBK said:
If you know, where the BM is check if an LED is glowing on it
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Thank you. I don't but I'll have a look.

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audlin said:
Thank you. I don't but I'll have a look.
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It's about the size of a cigarette packet, black, with three wires coming out of it.

Have you got a multimeter to check the battery voltage?
 
DBK said:
It's about the size of a cigarette packet, black, with three wires coming out of it.

Have you got a multimeter to check the battery voltage?
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Two wires if its a Votronic.
 
DBK said:
It's about the size of a cigarette packet, black, with three wires coming out of it.

Have you got a multimeter to check the battery voltage?
Click to expand...
Depends what he has it could be the votronic equivalent.
 
audlin said:
Something different. I had my van converted to my spec and that was on the spec list. I hope I'm not misusing my terminology: Eddie VB did install a BM on my motorhome a few years ago before I downsized.
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I only asked because your description is for the VB one but others work on a voltage threshold of something like 13.6v so if your leisure are not getting to that level nothing will be going to the starter.
 
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It’s worth checking the age of your engine battery, like all batteries they don’t take kindly to being left in a state of discharge for very long when they are starting to age and when charged they don’t hold the charge for long. Engine batteries not holding their charge at this time of year will really struggle when the snow and ice arrives.

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DBK said:
It's about the size of a cigarette packet, black, with three wires coming out of it.

Have you got a multimeter to check the battery voltage?
Click to expand...
I've located the box with three wires coming out of it, called Combi Master e11. There is no LED light on it. I don't have a multimeter; I'm afraid I'm an electrical simpleton. Before I speak to my garage who delivered my van to my home after completing the MOT, I just need an idea of what could be wrong.
 
If you haven't had work requiring the battery/ies to be disconnected the BM is up the spout.
If a battery has been disconnected the wire has probably been omitted on reconnection. .
 
A quick google suggests that a "combi master" is a split charge relay, not a "battery master" ie. Its for powering the hab battery/fridge from the engine battery
 
Combi Master e11 sounds like a split charge relay to charge your leisure batteries or run the fridge, not for maintaining the starter battery.

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If you read a description of the Combi Master it is both a split charger relay and a battery master. As funflair suggested above, if the habitation batteries are down then nothing will go to the vehicle battery. Do you have solar and is it working? Is there an alarm draining the cab battery?

It's difficult to diagnose further without knowing what the voltages on the batteries are.

If you can charge the cab battery up and if necessary the habitation batteries see how things are after another week.

A £10 multimeter is a very useful thing to keep in the MH. :)
 
DBK said:
If you read a description of the Combi Master it is both a split charger relay and a battery master. As funflair suggested above, if the habitation batteries are down then nothing will go to the vehicle battery. Do you have solar and is it working? Is there an alarm draining the cab battery?

It's difficult to diagnose further without knowing what the voltages on the batteries are.

If you can charge the cab battery up and if necessary the habitation batteries see how things are after another week.

A £10 multimeter is a very useful thing to keep in the MH. :)
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I have looked but can't see that mentioned anywhere?
 
The Wino said:
Depends what he has it
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"She " as in the lovely Audrey.
funflair said:
Combi Master e11
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I have a similar split charge relay but mine is wired with the sensing wire on the habitacion battery so when the solar takes it above 13,7 v it operates to charge the van battery.It shuts at 12,8 v- I'm wondering if Audrey 's is similar but lack of voltage hasn't allowed it to reach 13,7 to activate & the van battery has died if there has been small loads on it & lack of charge ?
 
funflair said:
Is it an Eddie VB battery master or something different?
Click to expand...

audlin said:
Something different. I had my van converted to my spec and that was on the spec list. I hope I'm not misusing my terminology: Eddie VB did install a BM on my motorhome a few years ago before I downsized.
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There is the answer to the thread title then! :giggler:

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audlin said:
After completing two weeks quarantine without using my van, I discovered today that the engine battery is completely flat. The leisure battery is fine, drawing from the solar panel. What I don't understand is that I have a battery master which " will only take power from the leisure battery, never the other way around. ... It is designed that when the engine battery drops half a volt below the leisure battery, Battery Master automatically adjusts the charge and tops up the engine battery." Any suggestions greatly appreciated.
Click to expand...
It is possible that solar won't provide enough power this time of year to cause the engine battery to also be topped off. These systems often require a good high charging voltage, which might require either mains or a good amount of sunshine. If your engine battery is supplying a tracker/alarm etc., it might not last very long and may not have been fully charged when you last parked it.
 
"If" the battery was fully charged when you left it, irrespective of whether you have a genuine, original all singing dancing bullet proof Battery Master or a cheap knock off copy :winky: why has the battery gone flat in just two weeks?

Irrespective of everything else "if" the battery is in good order and "if" it was fully charged when you left it there is a problem

"If" your not sure if the battery was fully charged when you left it, it could have been just as easily nearly flat if the state of charge is unknown

How old is the battery?

I ask this question professionally and normally people think that because the van was registered March 2017 the battery is "only three years old"

I ask how the dealer manufactured the motorhome on the same day it was collected!
 
I have just had the same problem but was half expecting it as my battery was 10 years old, the battery master had done a good job keeping it going for so long. I had recently noticed that if left for a couple of weeks the alarm on opening up only gave a weak signal. Fitted a new battery and all is good now

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