Another quick B2B question...sorry!

[ManTheVan]

Didn’t want to hijack any other threads.

I‘m considering upgrading to a LiFePO4 100Ah battery so need to change my EHU charger and install a B2B.

If I went to fit a B2B (probably a Sterling BB1230), could I use the existing cabling from the engine battery that terminates in my CB box in the garage? When I fitted the battery master, this is what I did, although in this case I would obviously have to bypass the split charge relay in the CB box.

Many other threads here seem to involve people running new cables and I’d like to avoid this if possible.

 

[Lenny HB]

All down to the size of the cables and the cable length with only a 30 amp B2B you could probably get away with 16 mm sq but the bigger the better.
A run of 3m with 16mm sq will give a volt drop of 0.19v.

 

[Wagoneer]

You say your CBE box is in the garage. If your leisure batteries are located amid-ships it might be better to install the B2B near to the leisure batteries with a direct new cable from the starter battery.

Perceived wisdom on here seems to consider it best to run the B2B in isolation from the CBE system with a relay to prevent back-feeding (looping).

 

[ManTheVan]

You say your CBE box is in the garage. If your leisure batteries are located amid-ships it might be better to install the B2B near to the leisure batteries with a direct new cable from the starter battery.

Perceived wisdom on here seems to consider it best to run the B2B in isolation from the CBE system with a relay to prevent back-feeding (looping).

The leisure battery is in the garage with all the electric boxes, so about as far away from the engine battery as possible!

I would need to keep the engine battery connected in some way to the CBE box, so that it maintains the readout on the control panel inside the van, too.

 

[Hymerbell]

Didn’t want to hijack any other threads.

I‘m considering upgrading to a LiFePO4 100Ah battery so need to change my EHU charger and install a B2B.

If I went to fit a B2B (probably a Sterling BB1230), could I use the existing cabling from the engine battery that terminates in my CB box in the garage? When I fitted the battery master, this is what I did, although in this case I would obviously have to bypass the split charge relay in the CB box.

Many other threads here seem to involve people running new cables and I’d like to avoid this if possible.

No probs....just make sure you connect negative to negative and positive to positive....don’t worry about all the rest.

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[Hymerbell]

I forgot to say I’m a bit of an expert on this electricity business.....I once kept a battery operated alarm clock going for 5 years....please feel free to tap into my expertise any time....if I’m not available you will just have to rely on Lenny HB and others who may be able to help.

 

[Wagoneer]

No reason why you can't use the existing cable from starter battery to CBE box provided it's of reasonable size to reduce volt drop, as Lenny mentioned.

The trick is to remove the cable (originating from the starter battery) where it connects with terminal B1 at the CBE box. Divert this cable to the B2B input. The B2B output goes to the positive on the lithium battery. Connect the positive terminal on the lithium battery to terminal B2 at the CBE box. Then insert a relay in the system so the split-charge relay in the CBE box is effectively disabled when the alternator is running. When the alternator is not running, normal services are retained.

This method is described in greater detail by Pausim in the following thread:

Carthago Split Charging Unit

I'm exploring the possibility of putting a B2B charger on my Carthago, but I understand that I'll need to disable the existing split charging unit. Does anybody know where it is? Is it a separate unit, or is it built into the electronic gubbins in the boot? I can't even identify a fuse for it...

www.motorhomefun.co.uk

Edit, you may find that removing the cable connection at B1 may affect other electrical circuits such as EHU charging of the starter battery etc. Best to initially remove the connection at B1 and see if any services are affected.

 

[Pausim]

I wired the B2B directly to the leisure and engine batteries, not via the CBE. I then intercepted the engine battery connection at B1 on the CBE and inserted a normally closed relay that would open and break the connection when the engine and B2B were running. The B2B being D+ operated.

 

[Wagoneer]

I wired the B2B directly to the leisure and engine batteries, not via the CBE. I then intercepted the engine battery connection at B1 on the CBE and inserted a normally closed relay that would open and break the connection when the engine and B2B were running. The B2B being D+ operated.

Agreed. If the OP wishes to retain the existing cable from the starter battery, the normally closed relay would need to be inserted prior to the B1 terminal and the connection to the B2B tapped off prior to this relay.

So, ignore my previous comment about disconnecting the feed from the starter battery to terminal B1.

Think I've got it right this time but happy to be corrected

 

[ManTheVan]

Really detailed advice, as always. I’m fine with doing everything up to the Insertion of a normally closed relay, which starts to expose my lack of knowledge! Not sure what kind of relay but willing to learn.

I’ll check through the suggested thread by Pausim to see if I can find the detail.

Thanks folks.

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[Pausim]

I think I used one of these

0-728-70 Durite 12V 40A-70A Mini Heavy-duty Changeover Relay

Durite 12V heavy-duty 40-70A changeover relays at Arc Components Ltd. Automotive changeover relay for switching load input lines from one output to another.

www.arc-components.com

with one of these

Durite Heavy-duty Bulkhead Socket for Relays | Re: 0-729-04

Durite heavy-duty bulkhead and panel socket for relays at Arc Components Ltd. Gang mountable sockets accepting 4 x 2.8mm, 2 x 6.3mm and 3 x 9.5mm locking terminals.

www.arc-components.com

 

[ManTheVan]

Thanks Pausim .Much appreciated.

 

[Wagoneer]

I think I used one of these

0-728-70 Durite 12V 40A-70A Mini Heavy-duty Changeover Relay

Durite 12V heavy-duty 40-70A changeover relays at Arc Components Ltd. Automotive changeover relay for switching load input lines from one output to another.

www.arc-components.com

with one of these

Durite Heavy-duty Bulkhead Socket for Relays | Re: 0-729-04

Durite heavy-duty bulkhead and panel socket for relays at Arc Components Ltd. Gang mountable sockets accepting 4 x 2.8mm, 2 x 6.3mm and 3 x 9.5mm locking terminals.

www.arc-components.com

I ordered the relay and socket. However, I found the socket really difficult to use as you first need to mount the socket with a screw, then add the relay, then insert the spade terminals. Pretty difficult when installing in a confined space. I gave up in the end and used insulated spade terminals for the smaller D+ wiring (insulating tape for the large terminals) and secured the relay with a homemade bracket. Anybody want a free socket ?

I believe Pausim secured the relay + socket in place by taping it to adjacent cabling.

 

[Lenny HB]

For high current I use the relays with studs and I have a hydraulic crimping tool for the terminals, much more reliable.

 

[Wagoneer]

For high current I use the relays with studs and I have a hydraulic crimping tool for the terminals, much more reliable.

The heavy duty stud relays tend to be of the normally open type (4 terminals), as far as I know, although I'm willing to be educated if this is not the case.

In this particular application a changeover relay is required (normally closed) with 5 terminals. This only seems to be available with blade terminals.

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[Lenny HB]

The heavy duty stud relays tend to be of the normally open type (4 terminals), as far as I know, although I'm willing to be educated if this is not the case.

In this particular application a changeover relay is required (normally closed) with 5 terminals. This only seems to be available with blade terminals.

You are right I didn't check before posting.

 

[Pausim]

I could not find a NC relay with studs and resorted to a changeover one with socket. I made no attempt to mount the socket but bound it up securely with self amalgamating tape.

 

[foxy]

Hi has anybody found a true b+ signal and if so where it located on 2015 ducato could use fridge cable but would be live if engine not running and key switch on found u tube clip that shows splicing into cables around ignition switch but does not state it's a true d+ supply any information appreciated

 

[Pausim]

Hi has anybody found a true b+ signal and if so where it located on 2015 ducato could use fridge cable but would be live if engine not running and key switch on found u tube clip that shows splicing into cables around ignition switch but does not state it's a true d+ supply any information appreciated

I would expect the 12V fridge supply to be D+ activated rather than ignition switch activated. It is another load that you only want to kick in when the alternator is running but I guess different constructors may not all use the same wiring. What make is your 12V distribution CBE, Schaudt etc?

 

[Stealaway]

My Ducato is a 2018 model but I found some ignition switched lives in the small plastic panel at the side of the hand brake behind the door opening. I use that two switch my B2B.

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[foxy]

Ducato 130 esprit 494 with a Sargent ec400 distribution system

 

[Pausim]

Ducato 130 esprit 494 with a Sargent ec400 distribution system

Sargent is a mystery to me but check whether the 12V fridge feed is coming on with the ignition switch or only when the engine is running. If you have a big B2B you don’t need it turning on before the engine is running because it will put a load on the engine battery just when you don’t need it.

 

[Lenny HB]

Often they is a relay control box fitted by the converter, on my Hymer there is a Schaudt relay control box that distributes the signal from the D+ to all the items that need it.

 

[ManTheVan]

OK. Have taken delivery of the Sterling B2B and Pro-charge lite boxes, both 30A.

I contacted Charles Sterling re the feedback loop issue and he advises simply disconnecting the engine battery from the CBE distribution box.

Thinking about it, I can’t see many ways that this would mess things up.

If I do this, I would also have to wire the wonderful Vanbitz battery master slightly differently, as it’s currently wired between the terminals of the CBE box, but that’s not a problem.

Apart from meaning that my CBE control panel in the MH would no longer show the engine battery voltage (which would be an inconvenience, in truth), would there be any other downside or ramifications to disconnecting the engine battery from the CBE unit?

Pausim, Lenny HB, Wagoneer, or any other electrical know-howers, what do you think?

 

[Pausim]

I am sure Charles Sterling will have given you good advice, he is far more knowledgeable than me. I used a relay so the engine battery will reconnect with the system when the alternator stops. By doing this I have kept the engine battery voltage displayed on the panel and also the CBE trickle charge to it when on mains hookup. Your Battery Master should take care of the trickle charge bit.

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[ManTheVan]

Thanks Pausim. To tell the truth I’d rather go with the relay system and have the best of both worlds, but I’m not entirely sure I understand the D+ concept or where, near/in the CBE box I would pick up the D+ feed to connect it to the relay.

 

[Wagoneer]

On my CBE box the D+ wiring is coloured yellow and marked along it's length with "D+".

Suggest the OP runs the engine with the feed from the starter battery disconnected at B1 and observe if any functions are missing. The fridge on 12v is normally powered from the leisure battery (via connection B2). In my particular case, I found that the orange side marker lights were powered from the B1 terminal via a separate fuse box with D+ input. This can be overcome by powering the marker lights off the B2 terminal.

When connected to EHU the mains charger obviously won't charge the starter battery with B1 disconnected unless a relay is inserted to re-make this connection when stationary.

Some French manufactured vans use a "Boite Relais Securité" which is separate from the CBE box. This 75 x 75mm grey square box contains a heavy duty relay and 50amp fuse. I think the purpose of this relay is to replace the 30amp split-charge relay mounted on the main CBE board. Anyway, it might be worth looking if you have this box as it could influence your future wiring layout.

 

[ManTheVan]

This OP has just ordered the relay from Pausim’s link along with 40A fuses and fuse holders, to do the B2B and pro-charge install as soon as he has his MH back with its new fresh water tank. Will look out for the yellow D+ wire and go from there!

 

[Carado]

Hi
I have just bought an Ebike and would like some advice on charging it’s battery while driving the bike lives in the rear garage but the leasure batteries are under the drivers seat a distance of 7 mts the charger that comes with the bike is 230 volts in with 36 volts out and the garage has a mains socket fitted have thought about connecting an inverts direct to the mains inlet any advice welcome

 

[Rodders1234]

Being a non techie and MH novice (12 months ago bought a SH MH) what is this b2b thing? What are the reasons to have it and how can you tell if you have it or not? Thanks

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