B2B install options

[steveh57]

We've been doing more and more off grid recently and fear with the bike recharging, shorter days that the 2 x 100ah lead acids may become marginal. I'm thinking of switching to Lithium before Autumn , this I believe ideally involves a B2B charger setup. Current setup is a Toptron EL537 distribution box and I believe the split charge relay resides within, which one of the two I've no idea , one I think states NONC 40A/30A, the other as no markings visible. The yellow wire to the side of the unmarked relay is I believe D+.

If I pull the 50 Amp fuse near the cab battery, the leisure battery no longer receives a charge on engine start up , the step still retracts on engine start up and the fridge works on 12V . So I'm assuming both of these are powered from the leisure battery. Do I need to check any other functions?

If the labelled relay is the split charge relay , and a B2B wired in series prior to this presumably it won't leave me with a lot of scope for charging power i.e 30Amp max according to that relay. I haven't properly checked the cable run yet, certainly it starts off at what looks like 16mm2 but looks possibly 10mm2 at the Toptron Battery 2 terminal

I was thinking leave the fuse out and run a seperate fused at both ends 16mm2 cable from the Cab Battery to Leisure Battery via a B2B- it will likely be a Victron 12|12 - 30A with bluetooth remote setup. Or do I use the original relay cable setup and hope it copes?

The Victron B2B , although it's got the engine start stop feature voltage detection I could feed the D+ signal instead.

Should I decide in future to have more charge power available I can add the same setup in parallel.

 

[Googlebot]

Pulling the fuse as you suggest from the split charge and adding your own cables sounds the best idea.

Just check that that won’t stuff the fridge charging up or anything else, on some systems the split charge relay is integrated into other things and can be a pain.

If you use big enough cables, adding a second will be much easier and I would always use a d+ as well.

 

[Two on Tour]

I wired our Sterling BB1260 directly cab battery to leisure battery via the Victron shunt, bypassing the power distribution unit.
I originally had as voltage sensing, but now have it manually switched.

 

[steveh57]

Thanks, Certainly with the fuse removed at the cab battery, engine on, the fridge set on battery was pulling 9-10 amps from the leisure, and the step retracted and still operates as it should. Just wondering whether there's anything else to check.

 

[steveh57]

I wired our Sterling BB1260 directly cab battery to leisure battery via the Victron shunt, bypassing the power distribution unit.
I originally had as voltage sensing, but now have it manually switched.

The Victron shunt was where I was going to lead the -ve from the B2B, the Victron DC-DC Charger I was thinking would be the non isolated version

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[cmcardle75]

Thanks, Certainly with the fuse removed at the cab battery, engine on, the fridge set on battery was pulling 9-10 amps from the leisure, and the step retracted and still operates as it should. Just wondering whether there's anything else to check.

If everything works with the fuse pulled, I'd keep it pulled (or repurpose it for your new cable run) and bypass the distribution box. You may still notice some features missing, like any battery monitoring of the cab battery, or back feed to cab battery from mains/solar charging.

 

[steveh57]

I'm hoping the Vanbitz battery master I currently use can be fed into the input side of the B2B, the mains charger is a completely separate unit Dometic Perfectcharge 1225 with separate feeds to cab and habitation, that is one thing I need to check again (along with control panel monitors) but pretty sure the SCR is not involved.

 

[John H.]

Just wondering whether there's anything else to check.

Check that the engine battery is still being charged on hook up.

 

[DBK]

I suggest fitting the B2B first with the existing batteries and see how you get on. It depends how you use the MH but it may be you can keep the lead acid batteries.

 

[steveh57]

Indeed, I agree I think that's a sensible way forward but obviously they won't last forever and with the B2B installed already , the swap to Lithium if/when required should hopefully be fairly straightforward.

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[steveh57]

I wired our Sterling BB1260 directly cab battery to leisure battery via the Victron shunt, bypassing the power distribution unit.
I originally had as voltage sensing, but now have it manually switched.

If on EHU the cab battery is being charged with an absorption voltage of 14.4, ( I never seen the cab battery at that voltage ) does that mean if I use Voltage sensing for the B2B that this will then activate as it thinks the engine is now on and will continue to operate until the cab battery drains and reaches ‘engine off‘ voltage. If so is this a problem i.e unnecessary charger and Battery wear. I’m still thinking of using D+ just musing options

 

[Two on Tour]

If on EHU the cab battery is being charged with an absorption voltage of 14.4, ( I never seen the cab battery at that voltage ) does that mean if I use Voltage sensing for the B2B that this will then activate as it thinks the engine is now on and will continue to operate until the cab battery drains and reaches ‘engine off‘ voltage. If so is this a problem i.e unnecessary charger and Battery wear. I’m still thinking of using D+ just musing options

Yes, looks like a likely scenario.

With our D+ at the base of the drivers B post, I found it easier to manually switched our B2B at the dash, plus I rarely need to use the B2B as with the amount of solar we have on the roof, it normally keeps our LifePo4 battery topped up anyway.

 

[steveh57]

I have had a more detailed look at the wiring today prior to fitting the Victron B2B 30A all the wiring seems to focus around the terminals on the Toptron distribution box. The Cab battery supplies a fused 16mm2 +ve to the battery 11 pole and 16mm2 -ve to the common -ve terminal. The leisure battery supplies 2x1 meter lengths - 10mm2 +ve to the battery 1 pole and 10mm2 to common -ve pole on the distribution box.

Am I correct in thinking this short run of 10 mm2 to the common -ve is ok. I think I've read the charts correctly. The B2B is non isolated and was thinking of a fused either side 16mm2 +ve cable direct to the leisure battery via the B2B from the cab and a -ve16mm2 cable from the B2B to a chassis ground yet to be determined.

 

[Pausim]

If on EHU the cab battery is being charged with an absorption voltage of 14.4, ( I never seen the cab battery at that voltage ) does that mean if I use Voltage sensing for the B2B that this will then activate as it thinks the engine is now on and will continue to operate until the cab battery drains and reaches ‘engine off‘ voltage. If so is this a problem i.e unnecessary charger and Battery wear. I’m still thinking of using D+ just musing options

D+ is a much better way of activating a B2B.

 

[autorouter]

Current setup is a Toptron EL537 distribution box and I believe the split charge relay resides within, which one of the two I've no idea , one I think states NONC 40A/30A, the other as no markings visible

Can't be certain without probing with a meter, but I think the unmarked relay is the split charge relay. It's right between the two battery terminals, with a couple of beefy connecting tracks on the circuit board. I don't think that helps you much though.

Be careful using that yellow wire you think is the D+. I can't read the writing next to it on the board, but it looks like 5V0, which is electronic-speak for 5.0V.

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[John H.]

D+ is a much better way of activating a B2B.

Certainly works well with our Sterling BB1260.

Be careful using that yellow wire you think is the D+. I can't read the writing next to it on the board

Our Hymer actuallly has "D+" written on the side of the yellow wire.

 

[steveh57]

Can't be certain without probing with a meter, but I think the unmarked relay is the split charge relay. It's right between the two battery terminals, with a couple of beefy connecting tracks on the circuit board. I don't think that helps you much though.

Be careful using that yellow wire you think is the D+. I can't read the writing next to it on the board, but it looks like 5V0, which is electronic-speak for 5.0V.

Thanks for that, it is a pretty scrawny yellow wire, anyways in order to sleep better I've just been out and checked the voltage, O volts on the meter until the engine starts, then it's showing over 12V, plus with it disconnected the step stays out- so I'm hoping I can use that for D+ ????

I've found some labelling for that larger relay it's hidden on the side not visible-FRC3A-1A So I think your correct it's the split charge relay, aren't they usually 70A?

I'm just wondering now since the step and the fridge are powered by the leisure battery when d+ is active and I've already got a 16mm2 cable from the cab battery whether to place the 30Amp B2B the cab battery side of the split charge relay near the distribution box, with the SCR rated at 70A surely that's within design limits and I'm also assuming the B2B is one way traffic i.e no flow from leisure to cab when the B2B is not active.

 

[autorouter]

I've found some labelling for that larger relay it's hidden on the side not visible-FRC3A-1A So I think your correct it's the split charge relay, aren't they usually 70A?

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[steveh57]

I wired our Sterling BB1260 directly cab battery to leisure battery via the Victron shunt, bypassing the power distribution unit.
I originally had as voltage sensing, but now have it manually switched.

So I understand correctly you've taken the -ve feed from the B2B through the Shunt? I'm guessing the shunt then provides the details of the state of charge of the leisure battery with input from the B2B as well?

 

[autorouter]

I'm just wondering now since the step and the fridge are powered by the leisure battery when d+ is active and I've already got a 16mm2 cable from the cab battery whether to place the 30Amp B2B the cab battery side of the split charge relay near the distribution box, with the SCR rated at 70A surely that's within design limits and I'm also assuming the B2B is one way traffic i.e no flow from leisure to cab when the B2B is not active.

Yes that's a good way to do it, when the B2B amps can be handled by the existing circuitry. The B2B will block both ways when not active. One way round that (if it's a problem) is to wire a relay between the B2B input and output, which connects the two when the B2B is not active. If you trigger that relay with the D+, you will need to use a relay with a Normally Closed (NC) terminal, which closes when D+ is off, and opens when D+ is on.

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[steveh57]

Bugger , woke up thinking about 12v electrics My Vanbitz battery master. I need to see if I can continue to use it. If I use the original cables for the B2B then presumably I will need a relay as suggested above for it to function. However if I use a separate feed for the B2B from Cab to leisure can I not fit the Battery Master to the B2B terminals?

 

[Two on Tour]

So I understand correctly you've taken the -ve feed from the B2B through the Shunt? I'm guessing the shunt then provides the details of the state of charge of the leisure battery with input from the B2B as well?

Correct, and the same with my Vanbiz Battery Master.

As I have added quite a few gadgets to our van, I have all my negs of my hab circuits connected to a bus bar and then I just have the one cable from the bus bar to the shunt.
Makes life a lot easier for adding circuits in the future. I also use a bus bar for all the +ve from circuits I have added.

 

[Pausim]

steveh57 now you have identified the split charge relay are you intending to disable it when the B2B takes over charging or feed the B2B through it?

 

[steveh57]

I'm in two minds, sadly. One option is to use the original cables with the B2B before the splitcharge and use D+ for the B2B as well. But then the battery master I believe won't work without an additional relay around the B2B, with this option the original cables are nearby, however the B2B is difficult to locate without unhooking the Truma exhaust feed out of the way to fix the B2B to a panel, just also thinking near the boiler is not going to be the coolest place to locate it

The other option is to leave the fuse out of the feed from cab battery to the split charge relay/ distribution box. So although the relay is still active via D+ I'm assuming I've broken the loop back? Then fused new cable runs to the B2B and leisure with the Vanbitz battery master connected around the B2B, with additional input from D+. This way is a lot lot easier to site the B2B in the cooler service locker.

The latter at present is what I'm leaning towards.

 

[autorouter]

One option is to use the original cables with the B2B before the splitcharge and use D+ for the B2B as well. But then the battery master I believe won't work without an additional relay around the B2B, with this option the original cables are nearby,

No need for a relay just for this. Connect the BatteryMaster between the B2B cab battery input and the leisure battery terminal on the Toptron box. It only takes a small trickle charge current, so thick wire is not necessary.

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[steveh57]

No need for a relay just for this. Connect the BatteryMaster between the B2B cab battery input and the leisure battery terminal on the Toptron box. It only takes a small trickle charge current, so thick wire is not necessary.

Thanks, I'm always trying to overcomplicate things However is is not best to find somewhere cooler for the B2B than near the boiler which is where it would be with the original cables.