The B2B question (1 Viewer)

[Pausim]

Looking at the option of a high current relay suggested in this thread to short-out the input and output of the B2B when engine is not running would seem to be an ideal solution to the limitations caused by using a B2B with the NE237 power supply. Just wonder if shorting out the the input and output +ve's of the 'running' B2B immediately the engine stops will cause it any harm ??

I don’t really understand this bit, I know nothing about Nord Electronica units. However shorting out the input and output doesn’t sound ideal before the voltage has had a chance to decay. I use a relay to isolate the distribution unit from the leisure battery whilst the engine and B2B are running. The B2B feeds the battery directly and my battery monitor shunt, which is on the negative connection of the leisure battery, picks up all the charging and discharging. Everything is connected normally when the engine is not running. This arrangement suits me but I know others have chosen different solutions that suit their set ups.

 

[footscray188c]

Bluetooth enabled lithium . Watch gadget John on U tube

 

[andy63]

My Adria power supply is a Nordeletronica NE237 unit and when the B2B is fitted in series with the engine battery feed you loose the ability to charge the engine battery from EHU and also because the solar regulator is connected via the NE237 for current and voltage measurements the ability for the solar to charge the cab battery is lost also as you cannot feed current backwards through a B2B unit.
In addition to this voltage measurement of the cab battery voltage is also lost.
Fortunately the votronic B2B senses the leisure battery voltage going above a certain higher voltage, being charged by solar power or ehu for example and can apply a charging 'bridge' automatically to back-feed up to 1A max to trickle charge the cab battery. Not really shure this is adequate as the cab battery voltage seems to fall day on day down to 12.6v as the MH is parked up with just a little solar some days.

.Looking at the option of a high current relay suggested in this thread to short-out the input and output of the B2B when engine is not running would seem to be an ideal solution to the limitations caused by using a B2B with the NE237 power supply. Just wonder if shorting out the the input and output +ve's of the 'running' B2B immediately the engine stops will cause it any harm ??

Hi..hope iv understood your points..
You have wired your battery to battery into your existing split charge circut..and lost some features available when on ehu etc..
Would it not be easier to just wire the battery to battery charger directly to the batteries and employ a relay to isolate the split charge system as has been discussed... a known to work solution..
Your proposed solution of fitting a relay to short out or bypass the battery to battery when the engine isn't running sounds like it would work ..at the end of the day just try it and see if it works ..the end result will depend on how quickly the battery to battery shuts down..how quickly the split charge/ battery parallel relay comes out and the trigger you use for your proposed relay..

Just wonder if shorting out the the input and output +ve's of the 'running' B2B immediately the engine stops will cause it any harm ??

I did run the battery to battery charger and the existing split charge system at the same time when I was playing around and there were no drastic consequences..

Andy.

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[Tombola]

Bluetooth enabled lithium . Watch gadget John on U tube

ordered 200ah lithium a few weeks ago, with victron b2b and have 400w solar on the roof via victron100/30.
delivery of new battery replcing my lead acid is due 7 december. Very helpful guy at polinovel/quality source

 

[Pausim]

Bluetooth enabled lithium . Watch gadget John on U tube

I think Gadget John is the muppet who couldn’t set his Li batteries up properly and eventually took them out in favour of AGM. In my opinion there is little useful to learn from this source. You will find better advice from Funsters.

 

[Lenny HB]

Bluetooth enabled lithium . Watch gadget John on U tube

Is that something else he has got totally wrong.
If you want lean anything he is the last person you want to watch.
He gets so much wrong.

Edit: Pausim beat me to it.

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[Pausim]

Is that something else he has got totally wrong.
If you want lean anything he is the last person you want to watch.
He gets so much wrong.

Edit: Pausim beat me to it.

It is a message well worth reinforcing.

 

[DIY campervan]

Hi guys.
After alot of expert tips and guidance of installing my lithium, i have ordered a B2B Victron 30Ah charger.

I have a CBE DS300 distribution box with integrated battery splitter. And its the version without the r37 resistor you can remove to fit a b2b.
My main question is this:
I have a 10mm2 positive cable from startbattery with a 50A fuse that goes to the +B1 on the ds300., and a 10mm2 positive from +B2 to leasure. Could i just wire the B2B directly to the +B1 and +B2, or do i have to pull a new cable all the way to the start battery?

Sounds very complex and hard to understand. Im not advocating change your set up but the ctek D250se Dc to Dc battery charger eliminates any need for a split charge relay and sits in between both starter and leisure battery and is a simple set up. It takes power from solar and charges your leisure battery first but if topped up the energy is diverted to the starter battery. Alternatively, if your taking power from your alternator, the power tops up the starter battery first then diverts the surplus to the leisure battery and all without the need of a split charge relay.
If things get too complicated where electrics are concerned then you must see an auto electrician for advise because fires are a consequence of wrong wiring system.

 

[autorouter]

Fortunately the votronic B2B senses the leisure battery voltage going above a certain higher voltage, being charged by solar power or ehu for example and can apply a charging 'bridge' automatically to back-feed up to 1A max to trickle charge the cab battery. Not really shure this is adequate as the cab battery voltage seems to fall day on day down to 12.6v as the MH is parked up with just a little solar some days.

Are you saying the cab battery voltage falls with the Votronic B2B fitted, or was that the situation before it was fitted?

The cab battery normally doesn't require much charge current. You arrive at the site or at home with the cab battery fully charged, so a trickle charge of less than half an amp ought to be enough to keep it topped up . 1A should be plenty. Unless you are running loads from the cab battery - the radio for example.

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[Tombola]

I think Gadget John is the muppet who couldn’t set his Li batteries up properly and eventually took them out in favour of AGM. In my opinion there is little useful to learn from this source. You will find better advice from Funsters.

He is back on Lithium now. but I find the resources here are great in my short time here.

 

[Lenny HB]

He is back on Lithium now. but I find the resources here are great in my short time here.

You really need to take anything he says with a huge chunk of salt.

 

[Pausim]

He is back on Lithium now. but I find the resources here are great in my short time here.

Well he certainly made a complete dog‘s breakfast of his first attempt.

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[Pausim]

Sounds very complex and hard to understand. Im not advocating change your set up but the ctek D250se Dc to Dc battery charger eliminates any need for a split charge relay and sits in between both starter and leisure battery and is a simple set up. It takes power from solar and charges your leisure battery first but if topped up the energy is diverted to the starter battery. Alternatively, if your taking power from your alternator, the power tops up the starter battery first then diverts the surplus to the leisure battery and all without the need of a split charge relay.
If things get too complicated where electrics are concerned then you must see an auto electrician for advise because fires are a consequence of wrong wiring system.

The problem is most of us start off with an existing relay in the standard distribution system that links the two batteries when the engine is running. In many cases this causes a loop which means the B2B is not only feeding itself but back charging the the engine battery at a voltage more suited to the leisure battery. Very inefficient and best avoided.

 

[andy63]

The problem is most of us start off with an existing relay in the standard distribution system that links the two batteries when the engine is running. In many cases this causes a loop which means the B2B is not only feeding itself but back charging the the engine battery at a voltage more suited to the leisure battery. Very inefficient and best avoided.

I'm with you on all aspects of what you say other than the back charging..
The loop created most probably does prevent the battery to battery from functioning correctly..
from the playing around I did the charging still continues through one of the loops.. but the power input required to do the charging of the leisure batteries can not be equalled on the output side of the charger..there have to be losses..so it can't then charge the start battery through another loop..
Its like the battery powering the inverter to run a charger that charges the battery thats running the inverter..it can't happen..the power on the input side can not equal the output power.. thats the way i keep looking at this anyway... the battery to battery will function correctly if the loop isn't there and most probably wont when its input and output are shorted .. but i don't see that any back charging will take place..
I think we have been here tofore havent we..
Happy to be told I'm missing something but I cant get me head round anything else


Andy...

 

[Pausim]

I'm with you on all aspects of what you say other than the back charging..
The loop created most probably does prevent the battery to battery from functioning correctly..
from the playing around I did the charging still continues through one of the loops.. but the power input required to do the charging of the leisure batteries can not be equalled on the output side of the charger..there have to be losses..so it can't then charge the start battery through another loop..
Its like the battery powering the inverter to run a charger that charges the battery thats running the inverter..it can't happen..the power on the input side can not equal the output power.. thats the way i keep looking at this anyway... the battery to battery will function correctly if the loop isn't there and most probably wont when its input and output are shorted .. but i don't see that any back charging will take place..
I think we have been here tofore havent we..
Happy to be told I'm missing something but I cant get me head round anything else


Andy...

I don’t think you are missing anything and the voltage drop would probably take care of the anomalies most of the time. With an Li battery my concern was that when it is full it shuts down and the B2B might continue to push out 14.6V for a bit longer. In which case there would be minimal voltage drop at the leisure battery so the 14.6V and current would pass down the line to the distribution unit, through the relay back up the connection to the engine battery where it would start going back round the circle. At this point I think the B2B and the ECU monitoring the engine battery might both get confused.

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[68c]

The problem is most of us start off with an existing relay in the standard distribution system that links the two batteries when the engine is running. In many cases this causes a loop which means the B2B is not only feeding itself but back charging the the engine battery at a voltage more suited to the leisure battery. Very inefficient and best avoided.

Why is charging the starter battery at the same voltage as the leisure battery a bad thing? On pre smart alternator the starter battery would have charged at near the voltage the B2B puts out so do not see a problem, plus this would only happen for the limited time the engine is running. Once the alternator stops outputting the split relay would disengage. Different story if you are using a voltage sensing relay, can see the B2B could keep the VSR connecting then.

 

[Pausim]

Why is charging the starter battery at the same voltage as the leisure battery a bad thing? On pre smart alternator the starter battery would have charged at near the voltage the B2B puts out so do not see a problem, plus this would only happen for the limited time the engine is running. Once the alternator stops outputting the split relay would disengage. Different story if you are using a voltage sensing relay, can see the B2B could keep the VSR connecting then.

This would also mean the B2B is powering itself which to me makes no sense. The B2B will be set with a specific charging profile to suit the leisure battery, which it monitors. If it is also charging the engine battery and powering itself it will have no way of monitoring the leisure battery accurately and no way of knowing which part of the charging cycle is needed. My way of looking at it is that it is not worth shelling out for expensive equipment if it can’t then do it’s job properly. Opinions vary and in many motorhomes undersized wiring and voltage drop will probably hide the issues.

 

[andy63]

With an Li battery my concern was that when it is full it shuts down and the B2B might continue to push out 14.6V for a bit longer. I

I've never seen my lithium shut down..other than when they were been bench charged with a dedicated lifepo4 charger..in fact I'm not sure whether it was the charger that shut off or the batteries that shut down..but the current did cease flowing..
Installed in the van ive never seen that... the various chargers including the battery to battery with their various lifepo4 profiles all go to a float charge which reduces the voltage to a level where charging pretty well stops.. because of the reduced voltage..
Andy

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[68c]

This would also mean the B2B is powering itself which to me makes no sense. The B2B will be set with a specific charging profile to suit the leisure battery, which it monitors. If it is also charging the engine battery and powering itself it will have no way of monitoring the leisure battery accurately and no way of knowing which part of the charging cycle is needed. My way of looking at it is that it is not worth shelling out for expensive equipment if it can’t then do it’s job properly. Opinions vary and in many motorhomes undersized wiring and voltage drop will probably hide the issues.

So as soon as the engine stops the split relay opens and there is no path to the starter battery.

 

[Pausim]

So as soon as the engine stops the split relay opens and there is no path to the starter battery.

Yes. There is no problem when the engine stops. I am talking about when the engine is running and the D+ signal has turned on both the B2B and the relay linking the batteries.

 

[Pausim]

I've never seen my lithium shut down..other than when they were been bench charged with a dedicated lifepo4 charger..in fact I'm not sure whether it was the charger that shut off or the batteries that shut down..but the current did cease flowing..
Installed in the van ive never seen that... the various chargers including the battery to battery with their various lifepo4 profiles all go to a float charge which reduces the voltage to a level where charging pretty well stops.. because of the reduced voltage..
Andy

Hopefully it would go to the float charge but I am not convinced it will always do this if it is still supplying the engine battery and powering itself.

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[68c]

Yes. There is no problem when the engine stops. I am talking about when the engine is running and the D+ signal has turned on both the B2B and the relay linking the batteries.

If the supply from the B2B to the starter battery is higher than the alternator voltage controller setting, the alternater will not output. So I suppose if the B2B can continue to draw on the starter battery you will have the starter battery being discharged and the alternator not charging. Does the B2B not automaticaly stop drawing starter battery power when the starter battery is at a 'below being charged voltage' ?

 

[autorouter]

Does the B2B not automaticaly stop drawing starter battery power when the starter battery is at a 'below being charged voltage' ?

Not necessarily. For example on Euro6 engines the alternator stops charging the starter battery before it is full. Its voltage drops, but it is still able to supply power to any load that needs it: lights, wipers, fan etc. The B2B takes power from the alternator, in the same way that any load does, and boosts the voltage to whatever the leisure battery requires. That's one of the main reasons for fitting a B2B.

 

[DBK]

I'm with you on all aspects of what you say other than the back charging..
The loop created most probably does prevent the battery to battery from functioning correctly..
from the playing around I did the charging still continues through one of the loops.. but the power input required to do the charging of the leisure batteries can not be equalled on the output side of the charger..there have to be losses..so it can't then charge the start battery through another loop..
Its like the battery powering the inverter to run a charger that charges the battery thats running the inverter..it can't happen..the power on the input side can not equal the output power.. thats the way i keep looking at this anyway... the battery to battery will function correctly if the loop isn't there and most probably wont when its input and output are shorted .. but i don't see that any back charging will take place..
I think we have been here tofore havent we..
Happy to be told I'm missing something but I cant get me head round anything else


Andy...

A B2B has a positive feed from the cab battery, a positive terminal going to the leisure batteries and a common negative connection to both. When working correctly the leisure battery voltage will be significantly higher than the cab battery voltage. But if you leave the split charge system in place this effectively connects both positive terminals together. The effect of this will be stop the B2B working completely. The batteries will be charged but only as they would be and by exactly the same mechanism as if there was no B2B in the system. This is because both sets of batteries will see the same voltage less any tiny differences due to losses in the wires. The critical point is the extra charging current you want for the leisure batteries can only come from the alternator pushing out more amps which it does when the cab battery voltage is reduced by the load placed on it by the B2B. By shorting the positive terminals of the B2B together, which is what you do by leaving a split charge system in place, the B2B can't put a load on the cab battery. The only charging current going into the batteries will be determined by the voltage the alternator settles down to.

Or in other words if you leave the split charging system in place you might as well chuck the B2B away because it will be doing nothing.

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[Pausim]

If the supply from the B2B to the starter battery is higher than the alternator voltage controller setting, the alternater will not output. So I suppose if the B2B can continue to draw on the starter battery you will have the starter battery being discharged and the alternator not charging. Does the B2B not automaticaly stop drawing starter battery power when the starter battery is at a 'below being charged voltage' ?

What autorouter and DBK said.

 

[68c]

Yes, I now see I do not really understand these new alternators, and accept the need to remove the split charge relay when using B2B.

 

[Pausim]

Yes, I now see I do not really understand these new alternators, and accept the need to remove the split charge relay when using B2B.

Worry not, we all come here to learn from each other.

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[ManTheVan]

Pausim’s detailed and logical explanations certainly guided me when fitting ours. The relay makes perfect sense and just works.

 

[chrish]

The Victron 30 amp DC- DC charger has a 'control' input that turns the device on and off, if this is connected to the D+ it will turn off immediately the engine stops.
On another note, The Victron Lithium batteries won't charge when they are below 5 degrees C does anybody have any ideas for keeping them above 5 degrees when in storage ?

 

[Robert Clark]

The Victron 30 amp DC- DC charger has a 'control' input that turns the device on and off, if this is connected to the D+ it will turn off immediately the engine stops.
On another note, The Victron Lithium batteries won't charge when they are below 5 degrees C does anybody have any ideas for keeping them above 5 degrees when in storage ?

I wouldn’t worry too much about keeping your lithium batteries above 5 deg when in storage as the UK seldom gets that cold for any length of time

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