B2B with Split Charge Relay

[Twinsdad]

I've fitted a Renogy B2B to my Hymer Exsis which comes with an EBL system. I've wired the Starter battery ( +/alternator) to the B2B input and B2B output to the EBL (starter in) with a fuse in both lines. The EBL output has been left connected to the Leisure battery. So the B2B is effectively in series as follows, Starter - B2B - EBL - Leisure with all the negatives connected together or to the chassis
Renogy instructions are not to connect the D+ wire except on a smart alternator as the unit can detect the engine running on a standeard alternator.
I've followed numerous instructions from Renogy, and Votronic and from forums such as this but I am puzzled about what to do with the Split charge relay built in to the EBL. When the engine runs this will surely connect the EBL starter input to the EBL leisure output. Is this right?.

 

[headlight]

I've fitted a Renogy B2B to my Hymer Exsis which comes with an EBL system. I've wired the Starter battery ( +/alternator) to the B2B input and B2B output to the EBL (starter in) with a fuse in both lines. The EBL output has been left connected to the Leisure battery. So the B2B is effectively in series as follows, Starter - B2B - EBL - Leisure with all the negatives connected together or to the chassis
Renogy instructions are not to connect the D+ wire except on a smart alternator as the unit can detect the engine running on a standeard alternator.
I've followed numerous instructions from Renogy, and Votronic and from forums such as this but I am puzzled about what to do with the Split charge relay built in to the EBL. When the engine runs this will surely connect the EBL starter input to the EBL leisure output. Is this right?.

Yes you need to disable the split charge. Someone will be along and explain how to do it on an EBL system.

 

[StillGoing]

How many amps is the B2B?
Depending on the answer, if it’s about 30A then all you needed to do was remove the stater battery + wire from the back of the EBL and put it into the B2B then run a new + wire from the B2B to the EBL.
I would always use the D+ and not rely on the B2B to work out when the engine is running.

Attached is the wiring for a Votronic B2B. Yours should be similar.


.

 

[Pausim]

If your B2B is feeding into the EBL instead of the original direct engine battery connection then the split charge relay does not need disabling. However this is putting all the Amps through the relay which need to be limited to a level the relay can cope with. I did this on my Hymer but used the Votronic B2B settings to limit the flow of Amps. The arrangements on my Carthago had to be different because it had a CBE DS and not an EBL.

 

[LostInSpace]

Our new Hymer does not use the split charge relay.

There is no connection to the Starter Battery input of the EBL 30.

The factory fitted B2B is connected with the input from starter battery/alternator and the output direct to the leisure battery - with settings for different battery technolgies. (both fused)

I am puzzled about what to do with the Split charge relay built in to the EBL

Ignore it. Let the B2B completely by-pass the EBL as Hymer have done on our Exsis-i 580.
i.e. No connection to the Starter Battery input of the EBL.

Use the D+ signal regardless of what sort of alternator you have.

The hook-up charging of the starter battery is done using a different ouput from the EBL 30.

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[autorouter]

I've followed numerous instructions from Renogy, and Votronic and from forums such as this but I am puzzled about what to do with the Split charge relay built in to the EBL. When the engine runs this will surely connect the EBL starter input to the EBL leisure output. Is this right?.

Yes, it's right. The B2B output as you say goes to the EBL Starter battery input, through the split charge relay when the engine is running, and from there to the leisure battery to charge it. That's exactly what you want it to do.

The starter battery side of the split charge relay is no longer connected directly to the starter battery as it was originally, so it won't directly connect the starter battery to the leisure battery, like it did before.

This method of connection channels the B2B output through the split charge relay inside the EBL.That's OK for up to about 30A, which is OK for many B2Bs, but if it's over 30A you should wire the B2B directly between the starter and leisure batteries. Then the starter battery input to the EBL needs to be disabled somehow - either remove the 50A fuse on the starter battery wire, or remove the wire to the EBL starter battery input.

 

[LostInSpace]

either remove the 50A fuse on the starter battery wire, or remove the wire to the EBL starter battery input.

Good point. Thank You. My post above said the Starter Battery connection to the EBL is not needed.

But, of course, if it is not needed and it is disconnected, it still needs the 50A fuse removing to isolate the bare copper at the end of the wire. as well as any insulation which may be applied.

 

[Twinsdad]

Thanks for all the advice guys

Headlight – If I disable the split charge will I need to connect the B2B output directly to the Leisure battery?

Still Going and Pausim– The B2B is 40 Amps but is programmable at 10A, 20A, 30A or 40A. The Votronic B2B shows a 30A connection directly to the B1 input (split charge relay) on the EBL. Are you suggesting set the Renogy B2B that I have down to 30A because the split charge relay may not cope with 40Amps?

Lost in Space - Just to clarify are you saying leave all the factory wiring in place so that the 240v charging still takes place and just wire the B2B between the starter battery and the Leisure battery?

Autorouter – Thanks, that’s what I thought but I’d forgotten that the starter battery was no longer connected to the split charge DOH!



I think the solution that everyone is pointing me towards is to reduce the Renogy B2B output down to 30A as I don’t really need the max of 40A. It will give me the least work to do if I then follow the Votronic circuit.

One final question, why does the EBL wiring diagram from Schaudt show the split charge relay protected by a 50A fuse if it can only handle 30Amps? Or are we just being very safe?

 

[LostInSpace]

Just to clarify are you saying leave all the factory wiring in place so that the 240v charging still takes place and just wire the B2B between the starter battery and the Leisure battery?

Yes, that is how our Hymer Exsis-i 580 is wired from the factory.

Our Hymer factory fitted Schaudt B2B charges the leisure battery at 45 amps - completely by-passing the EBL.

The 240 volt EHU still charges both batteries as Hymer wired it.
using the dedicated starter battery charging output from the EBL, not the starter battery main relay input, which is empty.

Hymer use the D+ to activate the B2B
There is no D+ connection to the EBL
.

 

[Pausim]

Still Going and Pausim– The B2B is 40 Amps but is programmable at 10A, 20A, 30A or 40A. The Votronic B2B shows a 30A connection directly to the B1 input (split charge relay) on the EBL. Are you suggesting set the Renogy B2B that I have down to 30A because the split charge relay may not cope with 40Amps?

I limited my Votronic B2B output to 38A and the EBL seemed fine with this.

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[Lenny HB]

The relay in the EBL is a 70 amp one but I doubt if the wiring would cope with that.

I always recommend you bypass the EBL as I have come across a couple where the relay contacts have carboned up thus reducing the throughput.

Easy to do as the cable Hymer use is normally 16mm², so you can just disconnect it from the starter battery input on the EBL and connect it to the input on the B2B, then connect the output of the B2B to the leisure battery via a suitable fuse.

As said always switch the B2B with the D+, you can pick that up on the front of the EBL.

One other thing to do is replace the 50amp Maxi blade fuse by the starter battery with a midi fuse those Maxi blade fuses & holders have a habit of melting when under constant load.