B2B Battery 2 Battery charger

xsilvergs

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41
Today I called into Sterling Power in Droitwich, I was passing, and looked at their BB1260, a 12 volt 60 amp battery to battery charger.

Why? Our 2017 Fiat's alternator puts out quite low voltages and hence struggles to charge the Service Battery, a Varta LA95 AGM battery, quick enough. See image for voltage, current and SOC on today's drive on motorways and A roads.

The best way to connect the B2B's I think is:- B2B input to Car Battery - B2B output to Service Battery. The only trouble is the Car and Service batteries will get connected by a parallel path when the split charge relay in the Nordelettronica NE196-T controller is energised when the engine is running. I have used the terms Car and Service for the batteries as per the circuit diagram.

I have looked around the www for ideas to stop this parallel path:-
One idea is to disconnect the Service battery from the J2 terminal using a relay whilst it is being charged by the B2B.
Second idea is to put a 100 amp diode between the Car Battery and J1 terminal.

I do have my own idea which is more complicated (i was an electronics technician in my working life) but I thought I would ask others their views.
 

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andyjanet

Rally Organiser

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861
I doesn’t matter about the split charge relay, the electronics in the sterling unit will charge the battery over and above any split charge unit,
If you get some decent wires from van battery to sterling and then to habitation battery
Electricity will find path of least resistance,
,
I used lengths of battery cables from the battery under passenger floor to rear garage in the merc rapido and the voltage drop was negligible
 

wildebus

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2,216
Do you have plans on getting another and/or larger Leisure Battery?
Just asking as a 60A B2B Charger is a bit oversized for a 95Ah Battery - it will not be able to put in anywhere close to 60Ah and more likely 20A would be the maximum into the battery (and quite possibly less). Just saying this as the bigger B2Bs tend to be quite a price jump and you could spend maybe a fair bit less and get the same results.
 

xsilvergs

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41
wildebus,

Very shortly (I'm guessing) I'll be switching to a Relion RB-100 LiFeP04 battery but in the meantime the 60 amp B2B can have its output limited to 30 amp.

What are your thoughts regards the relay RE1 as it could reduce the B2B's effect. It theoretically puts a short across the B2B.
 

Okta

Full Member

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427
wildebus,

Very shortly (I'm guessing) I'll be switching to a Relion RB-100 LiFeP04 battery but in the meantime the 60 amp B2B can have its output limited to 30 amp.

What are your thoughts regards the relay RE1 as it could reduce the B2B's effect. It theoretically puts a short across the B2B.
If you are planning to move over to a Relion battery you need to make sure the B2B has LiFePO4 profiles. When I was going through this I found the Votronic VCC1212-45 far better suited than other B2B chargers. You can also temporarily reduce the output of the B2B to levels that are less likely to fry a single lead acid battery. However, I think you might need to solve the issue with the relay that links the car and service batteries because the higher voltage out of the B2B will feed through the relay back to the car battery, creating a loop where the B2B is feeding itself and possibly over charging the car battery.

When I had a Schaudt EBL I simply intercepted the car battery supply to it. Now I have a CBE with a linking relay it is a bit more complicated, I believe I can cut out a resistor in the CBE to disable the linking relay but this seems a bit too drastic on a new vehicle under warranty. I was also thinking of a relay to cut off the supply when the B2B cuts in but I have yet to find a normally closed relay that looks up to the job. Normally open relays are easy to find but normally closed seem rather rare.
 

wildebus

Full Member

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2,216
wildebus,

Very shortly (I'm guessing) I'll be switching to a Relion RB-100 LiFeP04 battery but in the meantime the 60 amp B2B can have its output limited to 30 amp.

What are your thoughts regards the relay RE1 as it could reduce the B2B's effect. It theoretically puts a short across the B2B.
Makes sense to get a powerful B2B then :) good move if your alternator only outputs a lowish voltage.

Ref relay effecting B2B. Not something I have tried running in parallel but I am inclined to agree with you. The B2B charging algorithm could definitely be confused. It would not get a true picture of the battery charge state and so could end up getting into the the wrong charge state prematurely.

What I have done in a similar situation when I had both a Relay (for bulk charge at low battery SOC) and a B2B (for optimum charge at higher SOC) is simply use a switch to select between the two (I switched the ground out).
How you do that with a B2B does depend on the B2B model. On a relay you could intercept the control line if it is switched by a signal rather than voltage, or you could intercept the ground line (that would work on all Relays, be they switched or VSR type).

Is there any point in having the Relay ever there once the B2B is fitted? Maybe just disconnect the supply end or pull the fuse if it has a dedicated one?
 

xsilvergs

Full Member

Messages
41
Makes sense to get a powerful B2B then :) good move if your alternator only outputs a lowish voltage.

Ref relay effecting B2B. Not something I have tried running in parallel but I am inclined to agree with you. The B2B charging algorithm could definitely be confused. It would not get a true picture of the battery charge state and so could end up getting into the the wrong charge state prematurely.

What I have done in a similar situation when I had both a Relay (for bulk charge at low battery SOC) and a B2B (for optimum charge at higher SOC) is simply use a switch to select between the two (I switched the ground out).
How you do that with a B2B does depend on the B2B model. On a relay you could intercept the control line if it is switched by a signal rather than voltage, or you could intercept the ground line (that would work on all Relays, be they switched or VSR type).

Is there any point in having the Relay ever there once the B2B is fitted? Maybe just disconnect the supply end or pull the fuse if it has a dedicated one?
The relay RE1 is part of the Nordelettronica box, it's soldered to the PCB I believe, as it's still in warranty I'd rather not go in there.

Disconnecting the Leisure battery while it is being charged looks a good option, I think a relay powered by D+. When the engine runs the Leisure battery would be disconnected from J2 and charged by the B2B, the fridge etc would still be powered while driving via J1. When the engine is stopped the Leisure battery comes back on line and the B2B would have stopped charging.

Can you see a flaw in this idea?
 

John Thompson

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21
With the newer Auto stop start and regenerative breaking vehicles the alternator does always produce power and voltages can fall below or above the levels needed for a simple split charge relay to function.

I understand you need a smart B2B. I read this week that Stirling have put out information on this. This particularly affects fridges when run on 12v while driving as they are not getting the voltage necessary for them to cool .
 

wildebus

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2,216
The relay RE1 is part of the Nordelettronica box, it's soldered to the PCB I believe, as it's still in warranty I'd rather not go in there.

Disconnecting the Leisure battery while it is being charged looks a good option, I think a relay powered by D+. When the engine runs the Leisure battery would be disconnected from J2 and charged by the B2B, the fridge etc would still be powered while driving via J1. When the engine is stopped the Leisure battery comes back on line and the B2B would have stopped charging.

Can you see a flaw in this idea?
So the fridge is never connected to the leisure battery (LB) at any time, only the starter battery and then only when the engine is running?
You could use a relay indeed. I think this is how I would do it off the top of my head ...

Put a Relay between J2 and LB.
Use a 5-Pin relay so it has NO (Pin 87) and NC (Pin 87a) connections.
J2 goes to Pin 87a, LB is on Pin 30, D+ is on 86, GND is on 85.
When engine is running, D+ goes high, Relay is on and Pin 30 is connected to Pin 87 - which is not connected to anything and so the LB is disconnected from J2
When engine is off, D+ is low/floating, Relay is off and Pin 30 is connected to Pin 87a - so LB is connected to J2
Using a relay wired like this is handy as it is not powered for the majority of the time but only when driving, so will be a lot more reliable over time (and the NC connection can handle more current anyway - a 40A relay is really only 30A when on, but 40A when off).
The B2B would be connected directly to the LB with new cabling (and fuses), and switches off automatically on engine stop.

I think that would be my wiring?
 

xsilvergs

Full Member

Messages
41
So the fridge is never connected to the leisure battery (LB) at any time, only the starter battery and then only when the engine is running?
You could use a relay indeed. I think this is how I would do it off the top of my head ...

Put a Relay between J2 and LB.
Use a 5-Pin relay so it has NO (Pin 87) and NC (Pin 87a) connections.
J2 goes to Pin 87a, LB is on Pin 30, D+ is on 86, GND is on 85.
When engine is running, D+ goes high, Relay is on and Pin 30 is connected to Pin 87 - which is not connected to anything and so the LB is disconnected from J2
When engine is off, D+ is low/floating, Relay is off and Pin 30 is connected to Pin 87a - so LB is connected to J2
Using a relay wired like this is handy as it is not powered for the majority of the time but only when driving, so will be a lot more reliable over time (and the NC connection can handle more current anyway - a 40A relay is really only 30A when on, but 40A when off).
The B2B would be connected directly to the LB with new cabling (and fuses), and switches off automatically on engine stop.

I think that would be my wiring?
Thanks for your knowledge.
Yes, fridge never connects to the LB for its DC cooling function.
If the van is wired as per the circuit diagram I can simulate the relay with the battery cut-off switch under the drivers seat, well I assume that's what it does, but it is Italian!

I will report back when I've purchased and fitted.

Thanks again.
 

xsilvergs

Full Member

Messages
41
With the newer Auto stop start and regenerative breaking vehicles the alternator does always produce power and voltages can fall below or above the levels needed for a simple split charge relay to function.

I understand you need a smart B2B. I read this week that Stirling have put out information on this. This particularly affects fridges when run on 12v while driving as they are not getting the voltage necessary for them to cool .
Our 2017 Fiat does not have auto stop start, it just seems low on volts. At some point I will connect the second battery input on the BMV-712 to the starter battery and then it will log data, it's just another job on the list of things to do.
 

John Thompson

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Messages
21
The relay RE1 is part of the Nordelettronica box, it's soldered to the PCB I believe, as it's still in warranty I'd rather not go in there.

Disconnecting the Leisure battery while it is being charged looks a good option, I think a relay powered by D+. When the engine runs the Leisure battery would be disconnected from J2 and charged by the B2B, the fridge etc would still be powered while driving via J1. When the engine is stopped the Leisure battery comes back on line and the B2B would have stopped charging.

Can you see a flaw in this idea?
The B2B has both an on off switch and a diode to block return current. I had a 20amp B2B and it worked fine left on all the time. There is no need to disconnect any of the batteries the units do this for you. See my post about newer vehicles problems.

I had solar (260w) charging 3 x 110 Ah batteries and the B2B wired in as well. Still needed to go on hook up in Spain from now until end of January once a week for a night. I coincided with water top up and waste disposal.
 

wildebus

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2,216
Our 2017 Fiat does not have auto stop start, it just seems low on volts. At some point I will connect the second battery input on the BMV-712 to the starter battery and then it will log data, it's just another job on the list of things to do.
I have both batteries connected to the BMV-712 and it really is handy to be able to keep an eye on the starter battery (I have standard step well lights in my van on the starter and the cab doors that are independant on any overhead cab light switch - and which go on whenever the door is open. So when I am parked up and leave the sliding door open there is a constant drain on the starter battery. Handy to check it doesn't go too low!)
 

Okta

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427
So the fridge is never connected to the leisure battery (LB) at any time, only the starter battery and then only when the engine is running?
You could use a relay indeed.
This is an interesting solution that might also be useful in my CBE set up. However I think in my set up the fridge control panel is powered from the leisure battery, there being a separate feed to the 12v fridge heating element that is only live when the engine is running. In other words for the fridge to run on 12v it needs both circuits to be live. This may not matter in that as the leisure battery disconnects, the battery linking relay should close and supply the whole system from the engine battery. My concern would be a very short interruption to the 12v supply as it switches between batteries, this could well turn off parts of the system and CBE controls have a reputation for wanting things done in the right way.
 

xsilvergs

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41
This is an interesting solution that might also be useful in my CBE set up. However I think in my set up the fridge control panel is powered from the leisure battery, there being a separate feed to the 12v fridge heating element that is only live when the engine is running. In other words for the fridge to run on 12v it needs both circuits to be live. This may not matter in that as the leisure battery disconnects, the battery linking relay should close and supply the whole system from the engine battery. My concern would be a very short interruption to the 12v supply as it switches between batteries, this could well turn off parts of the system and CBE controls have a reputation for wanting things done in the right way.
Our fridge is wired the same.
I remembered I have a Victron Battery Protect (BP), this I'm going to fit and my intention is to use it as a relay. This I will try triggering from the relay that operates the 12 volt fridge supply which comes on with the ignition.

So the order of operation should be:-
Ignition ON and fridge switches to 12 volt operation. This then disconnects LB by setting the BP to open circuit and starts the B2B.

I just need to buy some cable and crimps to fit the BP.

I'll also post a circuit diagram of its function.
 

wildebus

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2,216
Just a word of note: It is not clearly stated or documented in an obvious way but the Victron Battery Protect should only ever be used in one direction (so in other words, you could use this in series from the output of a B2B, but not from the output of a Bi-directional VSR).
If the BP goes between J2 and the LB, is there any current flow from the LB TO the J2 port for any reason?
 

xsilvergs

Full Member

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41
Just a word of note: It is not clearly stated or documented in an obvious way but the Victron Battery Protect should only ever be used in one direction (so in other words, you could use this in series from the output of a B2B, but not from the output of a Bi-directional VSR).
If the BP goes between J2 and the LB, is there any current flow from the LB TO the J2 port for any reason?
Thanks for the note. I now read the instructions and it does say:-
Caution: uncontrolled reverse current will flow through a Battery Protect if Vout > Vin. Therefore never use a Battery Protect for battery to battery charging.

So that's not going to work, back to the old fashioned relay. The wiring between the LB and J2 is about 10mm2 so too large to go into a slide-on (Yellow) tag which most of these relays seem to be.
 

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wildebus

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2,216
Thanks for the note. I now read the instructions and it does say:-
Caution: uncontrolled reverse current will flow through a Battery Protect if Vout > Vin. Therefore never use a Battery Protect for battery to battery charging.

So that's not going to work, back to the old fashioned relay. The wiring between the LB and J2 is about 10mm2 so too large to go into a slide-on (Yellow) tag which most of these relays seem to be.
Interesting. sounds like decent cabling! and if the cable is sized appropriately to the current, then the 5-pin relays will probably be too small anyway? (the biggest I have seen is 60A and you want a bit of leeway)
You could still do this with relays - use a 100A or 200A relay for power transfer with a second small relay as control. I can post a wiring setup for that method if you want?
 

xsilvergs

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41
Interesting. sounds like decent cabling! and if the cable is sized appropriately to the current, then the 5-pin relays will probably be too small anyway? (the biggest I have seen is 60A and you want a bit of leeway)
You could still do this with relays - use a 100A or 200A relay for power transfer with a second small relay as control. I can post a wiring setup for that method if you want?
Yes I'd be interested in seeing your suggestion in a drawing
Did you see my drawing in last post?

I will try and investigate the cable routing to get a better idea how the LB cable gets to the J2 terminal.
 
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wildebus

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2,216
Yes I'd be interested in seeing your suggestion in a drawing
Did you see my drawing in last post?

I will try and investigate the cable routing to get a better idea how the LB cable gets to the J2 terminal.
What are the two 'Coil +Diode' units? added in? not sure how they come into play?

I don't know what relies on what in terms of the existing electrics, but this circuit will disconnect the connection between J2 and Leisure Battery ....

50825
 

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