Installing LifePo4 Hab, Battery conundrum in 2011 Autotrail. (1 Viewer)

Feb 9, 2008
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Question ! Has any member solved the riddle of installing a B2B charger in a circa 2011 Autotrail where the wiring from the Alternator is connected to the Sargent system.
As I understand it. There is a Sargent relay somewhere in the circuit that prevents Lithium batteries from being installed.
 

Kannon Fodda

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Does your vehicle have a small fuse box in floor behind drivers seat? If so one of the fuses may be the charger link from cab to leisure that you can pull. That's what was done on my 2018 van.
 
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PhilandMena
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Does your vehicle have a small fuse box in floor behind drivers seat? If so one of the fuses may be the charger link from cab to leisure that you can pull. That's what was done on my 2018 van.
Thanks for your input.
I do have a EM40 fuse unit which I believe is the small fuse box behind the drivers seat and I have a wiring diagram which I do not understand that shows 2 brown and black lines coming out of a VB out box and I assume that is the fuses that protects charging from the vehicle battery? I think I could live with isolating the leisure battery charging via the vehicle battery using the Alternator, providing all the other services like cab battery and 2 way fridge continue to get power from the alternator. Could it be that simple I wonder. Anyway, I have emailed Sargent to see what they say. Autotrail thinks there is a relay that prevents Lithium's from being used and Sargent might have a new relay available. Whatever one of them look like ??
 
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Oct 8, 2014
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I also have an Autotrail Excel. When I installed a CTEK D250 combined MPPT charger and B2B I fitted a N/C relay in the +ve supply, close to the battery. This is energised by the Fridge +ve signal, taken from the EM50 box behind the drivers' seat.

It means that the Leisure battery only charges from the alternator via the B2B, but the battery is connected to the Sargent panel when the engine is off.
 

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Kannon Fodda

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What is your Sargent unit? Mine is a EC176 which is an all in one 12V, 240V fusebox, charger, power supply. Any relay would have been inside that.

Cab battery is at the front of my van near the passenger seat. Leisure battery is at the rear near the EC176. As installed, the wiring of the EC176 all connections from alternator were via the cab battery, through the small fuses behind drivers seat floor, to the rear and using some quite flimsy wires. There will have been a few different connections through that fusebox. One did the main power for the charging relay. Others will have been the D+ type thing that allowed the fridge to work on battery whilst driving, power the radio from the leisure, and so on.

Only thing I've noted with the fuse for main charger pulled is the over door LED panel that should have reported leisure and cab battery voltages now sees only the leisure battery.

Of course new heavy cables are routed to supply the B2B from cab battery terminals through to the leisure.

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PhilandMena
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I also have an Autotrail Excel. When I installed a CTEK D250 combined MPPT charger and B2B I fitted a N/C relay in the +ve supply, close to the battery. This is energised by the Fridge +ve signal, taken from the EM50 box behind the drivers' seat.

It means that the Leisure battery only charges from the alternator via the B2B, but the battery is connected to the Sargent panel when the engine is off.
Thank you for this ! I'm not a sparky and struggle with basic electric's but If I have interpreted your email correctly all I need to do is connected a new positive cable to my cab battery which includes a N/C relay ? and then connect to a B2B charger. (which is then connected to both cab and leisure battery)???? Is the N/C relay attached to anything else ???
 
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PhilandMena
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What is your Sargent unit? Mine is a EC176 which is an all in one 12V, 240V fusebox, charger, power supply. Any relay would have been inside that.

Cab battery is at the front of my van near the passenger seat. Leisure battery is at the rear near the EC176. As installed, the wiring of the EC176 all connections from alternator were via the cab battery, through the small fuses behind drivers seat floor, to the rear and using some quite flimsy wires. There will have been a few different connections through that fusebox. One did the main power for the charging relay. Others will have been the D+ type thing that allowed the fridge to work on battery whilst driving, power the radio from the leisure, and so on.

Only thing I've noted with the fuse for main charger pulled is the over door LED panel that should have reported leisure and cab battery voltages now sees only the leisure battery.

Of course new heavy cables are routed to supply the B2B from cab battery terminals through to the leisure.
I have the EC500 PSU and the EM40. The rest of your message is a bit lost on me to be honest but appreciate your input.
 
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Oct 8, 2014
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Thank you for this ! I'm not a sparky and struggle with basic electric's but If I have interpreted your email correctly all I need to do is connected a new positive cable to my cab battery which includes a N/C relay ? and then connect to a B2B charger. (which is then connected to both cab and leisure battery)???? Is the N/C relay attached to anything else ???
Not quite. The N/C relay has to be installed into the original +ve supply between the Hab Battery and the Sargent panel. When the engine starts, the 12v supply to the fridge becomes live, and this is used to energise the relay, thus isolating the battery from the alternator supply.

New, heavy gauge +ve and -ve cables were then connected from the Engine Battery to the B2B.

I have attached another image showing the original Autotrail wiring as a comparison.

(Edited)
 

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Kannon Fodda

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This is the EM40 behind my drivers seat. Fuse is pulled from the "vehicle" connector and that is sufficient to stop the Sargent units trying to charge the leisure battery. That allowed everything else to keep working, and stops any need to mess about with disconnecting wires or other faffing.

The installation of the B2B and it's completely separate large cabling bypasses all the Sargent stuff and is made direct between the cab and leisure batteries .

Autotrail EM40.jpg

Try pulling that fuse and see if everything else is still running normally.
 
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PhilandMena
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Not quite. The N/C relay has to be installed into the original +ve supply between the Hab Battery and the Sargent panel. When the engine starts, the 12v supply to the fridge becomes live, and this is used to energise the relay, thus isolating the battery from the alternator supply.

New, heavy gauge +ve and -ve cables were then connected from the Engine Battery to the B2B.

I have attached another image showing the original Autotrail wiring as a comparison.

(Edited)
Many kind thanks for that ! So! I would need to find the positive cable from my Leisure battery that goes to my EC 500 PSU and fit a N/C relay into it. I'm a bit familiar with the wiring going to my Leisure battery as the three fuses for the Webesto Heater are part of the wiring and I assume there will be a separate positive cable ? I have found a brown cable that if my memory serves me correctly without going out and looking at the motorhome goes into the PSU and the Sargent Charger from the Leisure battery positive terminal.
Thanks again for your kind help. I'm getting there I think.

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Oct 8, 2014
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I'd be annoyed if it was that simple with the EM50.

This was the reply from Sargent when I asked them the question about disabling the split charger when I installed the CTEK D250S.

Screenshot_20230310-143052.png


In response to this question.

Screenshot_20230310-143419.png
 
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PhilandMena
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This is the EM40 behind my drivers seat. Fuse is pulled from the "vehicle" connector and that is sufficient to stop the Sargent units trying to charge the leisure battery. That allowed everything else to keep working, and stops any need to mess about with disconnecting wires or other faffing.

The installation of the B2B and it's completely separate large cabling bypasses all the Sargent stuff and is made direct between the cab and leisure batteries .

View attachment 725123
Try pulling that fuse and see if everything else is still running normally.
Yep! same as mine . Does this just stop the alternator from charging the leisure batteries, or does it also stop the Sargent charger from charging cab battery and or both.
 
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PhilandMena
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I'd be annoyed if it was that simple with the EM50.

This was the reply from Sargent when I asked them the question about disabling the split charger when I installed the CTEK D250S.

View attachment 725142

In response to this question.

View attachment 725143
Can you show me the N/C relay you fitted. I think the way you have gone about this is the bettr option of the 2 being discussed and I would probably get a competent person to do it for me anyway.
 
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Oct 8, 2014
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Many kind thanks for that ! So! I would need to find the positive cable from my Leisure battery that goes to my EC 500 PSU and fit a N/C relay into it. I'm a bit familiar with the wiring going to my Leisure battery as the three fuses for the Webesto Heater are part of the wiring and I assume there will be a separate positive cable ? I have found a brown cable that if my memory serves me correctly without going out and looking at the motorhome goes into the PSU and the Sargent Charger from the Leisure battery positive terminal.
Thanks again for your kind help. I'm getting there I think.
The wiring to my battery seems very similar to yours. I have the 3x +ve red & 1x -ve brown cables going to the Webasto, and then a +ve brown/blue and -ve white/red going to the Sargent charger. I cut the brown/blue to insert the relay.
 
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Can you show me the N/C relay you fitted. I think the way you have gone about this is the bettr option of the 2 being discussed and I would probably get a competent person to do it for me anyway.
I extended the cables because I didn't want the relay in the battery box, for safety reasons. I will take some photos and post them later.

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I extended the cables because I didn't want the relay in the battery box, for safety reasons. I will take some photos and post them later.
I'm not sure how much help this will be. I pulled the brown/blue cable out from the battery box and added a 20Amp fuse. From the fuse, a Red wire goes to the Relay with another Red cable then going back to the Battery +ve Terminal. (Note: I've made an error with the cable colour from the fuse to relay and relay to +ve terminal in my wiring diagram)

My battery box is a Mess!! I should have introduced a remote +ve Bus-Bar!

I added a 2nd Battery in the locker above, together with the CTEK Unit.

Isolating Relay.jpg



Battery Box.jpg
 
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PhilandMena
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That is a lot of cables ! However, very, very helpful. Thanks again. I may come back to you in time if I go down this route with some more info about what specific relay I would need to purchase but will cross that bridge when I get to it.
 
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Kannon Fodda

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Yep! same as mine . Does this just stop the alternator from charging the leisure batteries, or does it also stop the Sargent charger from charging cab battery and or both.
hmm, dunno.

I have an EC176, so probably even more simplistic than your Sargent unit. My thingy, even in a 2018 built van only offers one all out 13.8V charging voltage (no profile for lithium, no absorption phasing for lead acid, na-da). That has meant installing a separate mains charger for my lithium. The solar controller was also upgraded.

On my system only the leisure battery could have been charged on mains power from the Sargent thing. I now have the vanbitz battery master fitted to enable the cab battery to be trickle charged from the leisure when I'm on EHU or solar.

There was a means where apparently I could have used the over door control panel to switch the habitation use battery from the leisure to cab as a backup (a rather silly idea even in emergency as then you'd have no hope of starting the engine). That doesn't work with the EM40 fuse pulled.

Bottom line, pulling the fuse did the desired trick for me (in fact it was Vanbitz who did it as they did my original lithium install, and which I've subsequently tweaked), without messing other wiring. Pulling the fuse prevented whatever 12V charging relay from alternator existed in the Sargent EC176 from working on the leisure. It also prevented any back loop from the leisure to the cab that might happen with some B2B installations.
 
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PhilandMena
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hmm, dunno.

I have an EC176, so probably even more simplistic than your Sargent unit. My thingy, even in a 2018 built van only offers one all out 13.8V charging voltage (no profile for lithium, no absorption phasing for lead acid, na-da). That has meant installing a separate mains charger for my lithium. The solar controller was also upgraded.

On my system only the leisure battery could have been charged on mains power from the Sargent thing. I now have the vanbitz battery master fitted to enable the cab battery to be trickle charged from the leisure when I'm on EHU or solar.

There was a means where apparently I could have used the over door control panel to switch the habitation use battery from the leisure to cab as a backup (a rather silly idea even in emergency as then you'd have no hope of starting the engine). That doesn't work with the EM40 fuse pulled.

Bottom line, pulling the fuse did the desired trick for me (in fact it was Vanbitz who did it as they did my original lithium install, and which I've subsequently tweaked), without messing other wiring. Pulling the fuse prevented whatever 12V charging relay from alternator existed in the Sargent EC176 from working on the leisure. It also prevented any back loop from the leisure to the cab that might happen with some B2B installations.
Thanks for this. I'm a bit surprised Van bits pulled the fuse when he could have fitted a relay like @Revolver did and still maintain all the Sargent systems and protected the alternator. Assuming it would ? your set up is very alien to me and I suspect very newish which begs the question why Autotrail did not allow for Lithiu to be fitted without major surgery / Still, like I said this is all a black art to me and I have to admit Im out of my depth when it comes to installing Lithium Leisure batteries. So much for the drop in replacements the manufactures claim they are.
 
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Ours is a 2013 Autocruise Alto, with a Sargeant EC460 PSU. When installing a Victron B2B I also took the approach of using a relay to disconnect the vehicle battery from the PSU when the ignition is switched on.

I need to finish writing up my thread on the install - but it's been working well for us since September last year.

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Tombola

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Thanks for this. I'm a bit surprised Van bits pulled the fuse when he could have fitted a relay like @Revolver did and still maintain all the Sargent systems and protected the alternator. Assuming it would ?
a good reason for this from vanbitz is probably that the sergant EC176 is a woeful piece of kit with a 240 charger, piss weedy wiring and that at best will give about 7-8amps when on hookup to charge batteries if other things are being used even less, so waste of time on lithium.
I had the same unit in a 2019 Autotrail and installed a seperate Victron 240v charger and Victron b2b & mppt then disabled mine after installing lithium.
 
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Kannon Fodda

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Vanbitz pulling the EM40 fuse was the simple, reliable, solution. Bear in mind my main Sargent EC176 wasn't up to the job for the lithium (it wasn't up to even lead-acid in 2018, and I suspect was used for cost alone as so much of the V-Line was designed to look good on the surface, but under the skin was a little more limiting). It's entire charging of leisure from alternator was to be disabled. The B2B effectively replaced any need for relays and other tricks.
 
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That is a lot of cables ! However, very, very helpful. Thanks again. I may come back to you in time if I go down this route with some more info about what specific relay I would need to purchase but will cross that bridge when I get to it.
I have been going through my records to see which relay I used, but I'm sure it would have been similar to THIS, though probably a 30/40A would be sufficient.
 
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PhilandMena
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Thanks! Is that grey thing you have the voltmeter on, the Relay ???? and the two connectors removed from the PSU connection, joined together in the relay.

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Tombola

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Thanks! Is that grey thing you have the voltmeter on, the Relay ???? and the two connectors removed from the PSU connection, joined together in the relay.
No he just bypassed the relay and connected the 2 connectors together (that would go to the relay) to show what would happen when the relay is activated ..
The reason was because he had the system out of the van so he could show how it works on that particular sergent unit.

It's the same as if the relay was working.
 
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PhilandMena
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No he just bypassed the relay and connected the 2 connectors together (that would go to the relay) to show what would happen when the relay is activated ..
The reason was because he had the system out of the van so he could show how it works on that particular sergent unit.

It's the same as if the relay was working.
Thanks ! That method is totally lost on me !
 
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Steve and Denise

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I also have an Autotrail Excel. When I installed a CTEK D250 combined MPPT charger and B2B I fitted a N/C relay in the +ve supply, close to the battery. This is energised by the Fridge +ve signal, taken from the EM50 box behind the drivers' seat.

It means that the Leisure battery only charges from the alternator via the B2B, but the battery is connected to the Sargent panel when the engine is off.
That’s exactly how I did it on my cbe very simple and also easy reversal in future.
Been working fine for over 2 years🙂
 
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