Charge to cab battery (1 Viewer)

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Feb 22, 2011
10,090
20,924
Newcastle under Lyme
Funster No
15,397
MH
Hymer B544 A Class
Exp
Since 2015
I have recently fitted the Votronic 250 duo solar mppt controller and it has a + output to the cab battery to supply a charge that I`d like to use.
What confuses me is there is no - connection, so how does that work please ??? confused.com
The leisure battery has both so why not the cab battery ?
I understand I need a 5 amp inline fuse, do I just bolt the cable onto the + battery terminal.
Thanks and apologies if this is a numpty question, or I missed something.
Manual attached, page 3 for wiring diagram
 

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  • Voltronic Solar-Regler MPP 165 - 430 Duo ab 07-2018_e.pdf
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Apr 10, 2010
562
586
Bedfordshire
Funster No
10,998
MH
Carthago
Exp
Since Sept 2003
I'm no expert, but it seems to me that the regulator is only supplying a trickle charge to the cab battery (5A fuse) and the return path is via the earth to chassis.
 
Nov 23, 2011
479
408
durham
Funster No
18,991
MH
Lowline
Exp
since 2006
Looking at the diagram it's a common earth for the leisure and starter battery so probably only one earth is needed
 

andy63

Free Member
Jan 19, 2014
4,672
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south shields
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since 1990
I understand I need a 5 amp inline fuse, do I just bolt the cable onto the + battery terminal.

Yes....

Below is a copy / paste from the instructions on connecting the start battery... basically saying whats been said in the posts above:xThumb:

''Usually, the minus poles of the starter battery („Start II“) and of the supply battery („BOARD I“) had already been connected by the customer. If not, this connection must be made for charging of the starter battery.''
 
Sep 1, 2017
222
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Funster No
50,291
Trickle charge I think, maybe 1Amp from memory.

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Apr 27, 2016
7,025
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Since the 80s
What confuses me is there is no - connection, so how does that work please ??? confused.com
The leisure battery has both so why not the cab battery ?
The cab/chassis part of the MH is basically a metal frame. Manufacturers save on copper wire costs by connecting all the device negative returns to the metal chassis/frame. To complete the circuit, the starter battery negative is also connected to the chassis/frame. Think of the whole chassis/frame as one large negative battery terminal.

The habitation section is made of fibreboard or plywood lining, with PU foam and an aluminium or glass fibre skin. It doesn't have nice guaranteed metal return paths. Habitation circuits are usually wired with full positive and negative wiring, right back to the fuse box or battery.

The habitation batteries normally need to have the negative connected to the chassis/frame, because they are charged by the engine alternator which also has its negative connected to the chassis.

If you need to verify this (eg if are working on an oddball diy conversion), you can check this by measuring the resistance (ohms) between the habitation battery negative terminal and the starter battery negative terminal. You should get a reading of zero, because it should be too small to measure on a normal multimeter.

If the solar controller negative is connected to the habitation battery negative, it will automatically be connected to the starter battery negative too.
 
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OP
OP
Figaro
Feb 22, 2011
10,090
20,924
Newcastle under Lyme
Funster No
15,397
MH
Hymer B544 A Class
Exp
Since 2015
Your last paragraph explained it nicely.
I knew about the vehicle ground / earth but I hadn't appreciated the hab would also be earthed to the chassis.
I'm on a learning curve (y)
 
Jan 19, 2014
9,485
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Your last paragraph explained it nicely.
I knew about the vehicle ground / earth but I hadn't appreciated the hab would also be earthed to the chassis.
I'm on a learning curve (y)

The EHU earth is also the same point, so never try and solder a positive wire, ask me how I know :ROFLMAO:
 

funflair

LIFE MEMBER
Dec 11, 2013
19,679
31,699
Guisborough
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29,351
MH
MORELO palace
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since 2012
The EHU earth is also the same point, so never try and solder a positive wire, ask me how I know :ROFLMAO:
I tried that with a soldering iron running off the inverter Pft, permanent live to radio not live anymore and couldn't find a fuse.

Martin

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Nov 4, 2011
6,082
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Funster No
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When I fitted my 250 duo recently and fitted the battery charge wire with inline fuse into the connector on the bottom of the EBL
 
OP
OP
Figaro
Feb 22, 2011
10,090
20,924
Newcastle under Lyme
Funster No
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MH
Hymer B544 A Class
Exp
Since 2015
When I fitted my 250 duo recently and fitted the battery charge wire with inline fuse into the connector on the bottom of the EBL
Did you have to remove the ebl ?
What connections are on the bottom ?
I don't want to connect mine up yet until I got my problem sorted out with the wiring to the front bumper. Removed the bumper and wiring to fog lights and indicators all wrong on reconnection. I think it might be the snaplock connection block damaged but not been able sort yet.
 
Last edited:
Nov 4, 2011
6,082
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I did remove the EBL just to make it easier than laying squashed down by the seats.
At the bottom is as this.
AAD184DD-3C3B-43D3-BC70-BD4E75A4E3E7.jpeg
 

andy63

Free Member
Jan 19, 2014
4,672
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The EHU earth is also the same point, so never try and solder a positive wire, ask me how I know :ROFLMAO:

I fell foul of that and got a bit of a surprise when soldering in the van...
Id been doing it off an extension from the house and all was fine..
Think i ran out of lead so plugged the van ehu in and then tried to continue using the vans internal socket...
Result was much sparking etc before the penny dropped :LOL:
Andy.
 
OP
OP
Figaro
Feb 22, 2011
10,090
20,924
Newcastle under Lyme
Funster No
15,397
MH
Hymer B544 A Class
Exp
Since 2015
I did remove the EBL just to make it easier
I'm going to do as you suggest, connect to the cab battery via the connection on the bottom of the ELB. Does it just slide out after removing connections on the top ?
Is there anything I need to be aware of when removing it ?
Obviously I'll remove ehu and turn off 12 volts, anything else I need to do ?
TIA

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Nov 4, 2011
6,082
41,251
Uk
Funster No
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2001
I'm going to do as you suggest, connect to the cab battery via the connection on the bottom of the ELB. Does it just slide out after removing connections on the top ?
Is there anything I need to be aware of when removing it ?
Obviously I'll remove ehu and turn off 12 volts, anything else I need to do ?
TIA
Yes, once you’ve removed the connections, I took a photo so I knew where each one went, and then ease it up.
 

Lenny HB

LIFE MEMBER
Oct 18, 2007
54,497
155,065
On the coast in West Sussex
Funster No
658
MH
Carthago Compactline
Exp
Since 2008 & many years tugging
You don't say what EBL you have but most have a 3 pin block on the front to connect to both leisure & starter battery. Not sure but I don't think thrEBL 99 has the starter connection but all later ones do.
 
Apr 27, 2016
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If your system has an automatic frost protection valve, it is held closed by 12v power via the EBL. It will open when you disconnect the EBL, unless you hold it closed with a clamp, clothes peg or similar.
 
OP
OP
Figaro
Feb 22, 2011
10,090
20,924
Newcastle under Lyme
Funster No
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MH
Hymer B544 A Class
Exp
Since 2015
Sorry it's ELB99. I think it does get a charge to cab battery when on ehu.
Hopefully it will also get it from solar when I've done this connection.
Thanks guys
 
Nov 4, 2011
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Exp
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I hope you positioned your Duo250 out of the way, I put mine under the EBL and glad I did because when it’s dark the Mppt light flashes until it gets daylight on the panels.

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OP
OP
Figaro
Feb 22, 2011
10,090
20,924
Newcastle under Lyme
Funster No
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MH
Hymer B544 A Class
Exp
Since 2015
I put it in place of the schault which was in the cabinet with the slide top behind the ELB so out of the way.
It does say in instructions to allow ventilation which it hasn't got in there but I'll just see how it goes.
If it starts getting too hot I'll move it. Need some sunshine to see.
 

Lenny HB

LIFE MEMBER
Oct 18, 2007
54,497
155,065
On the coast in West Sussex
Funster No
658
MH
Carthago Compactline
Exp
Since 2008 & many years tugging
I hope you positioned your Duo250 out of the way, I put mine under the EBL and glad I did because when it’s dark the Mppt light flashes until it gets daylight on the panels.
Should be mounted vertically with plenty of airflow around it.
 
OP
OP
Figaro
Feb 22, 2011
10,090
20,924
Newcastle under Lyme
Funster No
15,397
MH
Hymer B544 A Class
Exp
Since 2015
Ok I disconnected the EBL 99 and the connection on the bottom for the cab battery is already occupied.
IMG_20190113_113630681.jpg


Do I just add the lead to the votronic controller or is there no need ?
Maybe it's already getting a charge from the solar ???
TIA
Chris
 
Jan 19, 2014
9,485
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Derbyshire
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It’s fixed to the wall, below the EBL, so should be ok

They have a tiny axial fan inside them that comes on when they get warm. Mine comes on when it charges at 6+ amps. It's just a quiet hum (y)

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Nov 4, 2011
6,082
41,251
Uk
Funster No
18,763
MH
A class
Exp
2001
Ok I disconnected the EBL 99 and the connection on the bottom for the cab battery is already occupied.
View attachment 276837

Do I just add the lead to the votronic controller or is there no need ?
Maybe it's already getting a charge from the solar ???
TIA
Chris

I fitted the wire from the Votronic to the engine battery terminal shown, using a crimped blade connector, I think the wire already there is from the main charger unit in the EBL
 

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