Victron B2B with original CBE setup ?

[autorouter]

Any charger like a B2B, solar controller or mains charger will have diodes to prevent any unwanted back-feeding of current. They can be safely wired to the battery, and the one with the highest voltage does the charging job. The point about the split charge relay is that it is a direct metallic connection across the input and output of the B2B, effectively shorting it and therefore making it useless.

A B2B doesn't necessarily have a higher voltage than the alternator output, it just usually does. When the leisure battery is full, the B2B will drop into float mode, but the alternator might still be at 14.4V or more. When the starter battery is full, the alternator will reduce its output voltage, but if the leisure battery is not full the B2B will continue to charge at the optimum voltage. If the leisure battery is a different technology (Gel, AGM etc) the B2B can charge it correctly, independently of what the alternator does to the starter battery.

 

[Tombola]

Question on this is that I have a lithium (installed) and a B2b that I haven't yet installed as the alternator puts 40 + amps into the leisure battery when required.
As you say the alternator still goes at 14+ volts but my battery has a cut out when full charge is reached to avoid over charging. I then see via Bluetooth that it is receiving zero from the alternator when full...is it ok to rely on the batteries cut out in this scenario.

And should I ideally be charging the lithium every now and then via my victron main 3 stage to keep the best condition

Thanks

 

[JockandRita]

No need just put a normally closed relay on the existing engine battery connection to the CBE, which will open using the D+ signal when the engine and B2B are running. See link at #16 for pictures.

Paul, I've had a look back at your thread, but haven't found the size of the NC relay you used. Can you remember please?

Thanks,

Jock.

 

[Pausim]

Paul, I've had a look back at your thread, but haven't found the size of the NC relay you used. Can you remember please?

Thanks,

Jock.

I think it was 60/70A. With a 50A fuse I reckoned this was sufficient.

 

[JockandRita]

I think it was 60/70A. With a 50A fuse I reckoned this was sufficient.

Thanks Paul.

Cheers,

Jock.

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[Pausim]

Thanks Paul.

Cheers,

Jock.

Might have been one of these.

0-728-72 Durite 12V 80A-100A Mini Extra HD Changeover Relay

Durite 12Vdc changeover relay from Arc Components Ltd. Automotive 12 Volts 80-100A heavy-duty changeover switch relay. 3 x 9.5mm and 2 x 6.3mm brass terminals.

www.arc-components.com

 

[autorouter]

And should I ideally be charging the lithium every now and then via my victron main 3 stage to keep the best condition

Lithiums are entirely different from lead-acids regarding maintenance. A lead-acid needs charging fully to 100% about every couple of weeks, preferably every week, to avoid gradual deterioration as the lead sulfate hardens into crystals. In contrast, Lithium batteries can be left for months, even years, at the 50% to 80% level, with hardly any deterioration. Also, overcharging causes rapid deterioration. Keep them in the 10% to 90% range and they will last for decades.

How to do that is the big question. I don't know of an off-the-shelf charger that does this, but some have custom settings. The usual 'lithium profile' charges them up to about 100%.

 

[Tombola]

Lithiums are entirely different from lead-acids regarding maintenance. A lead-acid needs charging fully to 100% about every couple of weeks, preferably every week, to avoid gradual deterioration as the lead sulfate hardens into crystals. In contrast, Lithium batteries can be left for months, even years, at the 50% to 80% level, with hardly any deterioration. Also, overcharging causes rapid deterioration. Keep them in the 10% to 90% range and they will last for decades.

How to do that is the big question. I don't know of an off-the-shelf charger that does this, but some have custom settings. The usual 'lithium profile' charges them up to about 100%.

a switch on the cable from alternator charge it is then

 

[pete4x4]

The other alternative is simply to isolate the battery from the split charge with a NC relay driven by D+, that way your B2B will not be running the fridge as well.

 

[Pausim]

The other alternative is simply to isolate the battery from the split charge with a NC relay driven by D+, that way your B2B will not be running the fridge as well.

On my CBE setup it does run the fridge. The 12V fridge connection comes from the CBE DS not directly from the engine battery. When the engine is running the normal set up links the 2 batteries through the relay and in effect the leisure battery and the fridge share the power coming from the engine battery/alternator. Having added a NC relay and a B2B the engine running link is replaced by the B2B supply to the leisure battery which is still connected to the CBE which in turn continues to provide the 12V to the fridge.

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[pete4x4]

I dont know the CBE setup so in your design does the B2B provide its maximum output to the LB when the fridge is also on?

 

[Pausim]

I dont know the CBE setup so in your design does the B2B provide its maximum output to the LB when the fridge is also on?

All the output goes to the leisure battery but as this is also supporting the 12V fridge the net gain is reduced. It still charges the leisure battery much more effectively than the original system which has always shared the the output of the engine battery/alternator between the leisure battery and the fridge.

 

[pete4x4]

All the output goes to the leisure battery but as this is also supporting the 12V fridge the net gain is reduced. It still charges the leisure battery much more effectively than the original system which has always shared the the output of the engine battery/alternator between the leisure battery and the fridge.

So by putting the relay in between the leisure battery and the cbe the B2B would just charge the leisure battery and the split charge would feed the fridge so a lot more efficient.

 

[Steve and Denise]

So by putting the relay in between the leisure battery and the cbe the B2B would just charge the leisure battery and the split charge would feed the fridge so a lot more efficient.

That’s exactly how mine is

 

[Pausim]

So by putting the relay in between the leisure battery and the cbe the B2B would just charge the leisure battery and the split charge would feed the fridge so a lot more efficient.

Yes I suppose it would make the battery charging quicker. I am not planning on changing my arrangement because it works well as it is but if I was starting again I might look at some other solutions. When I made my alterations in 2019 I was trying to avoid nipping out the resistor because I wanted to be able to reverse things if there were some hidden consequences. CBE were no help, all I knew was that leaving the loop looked like a bad idea.

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[Antique]

So by putting the relay in between the leisure battery and the cbe the B2B would just charge the leisure battery and the split charge would feed the fridge so a lot more efficient.

I am in this position atm and have an auto sparky visiting tomorrow to hopefully sort it.

My Votronic solar regulator is connected to trickle charge start batt, I believe this is causing a problem for the b2b which has no D+ connection atm.
Apart from fitting the above relay, would it be advisable to also connect the b2b D+ ?

Many thanks for any advice

All the best
Antique

 

[autorouter]

My Votronic solar regulator is connected to trickle charge start batt, I believe this is causing a problem for the b2b which has no D+ connection atm.
Apart from fitting the above relay, would it be advisable to also connect the b2b D+ ?

I think that's a good idea. B2Bs triggered by voltage thresholds are OK on simple systems, but cause problems with more added charging options.

 

[pete4x4]

I am in this position atm and have an auto sparky visiting tomorrow to hopefully sort it.

My Votronic solar regulator is connected to trickle charge start batt, I believe this is causing a problem for the b2b which has no D+ connection atm.
Apart from fitting the above relay, would it be advisable to also connect the b2b D+ ?

Many thanks for any advice

All the best
Antique

Yes I would connect the D+ to the B2B as well as the relay. By connecting D+ to the B2B it would prevent the B2B from discharging the starter battery when the solar regulator trickle charge voltages reach the B2B turn on thresholds

 

[Jim Jackson]

I have been following this thread after fitting a larger battery to my van and wanting to improve charging when driving.
So looking to fit a b2b charger and leave the CBE unit in my van to work as normal (except charging from the alternator).
Researching online I found this diagram relating to a Sterling b2b to a CBE DS300 unit as in my van which may help with other CBE units?