Fitting a B to B Charger (1 Viewer)

[Ian Bosman]

I have a CBE charge controler on my 'van and the 'loop' problem you alluded to has concerned me as I too . was thinking of fitting a B2B.
So you are suggesting that I could safely ignore this point and not go down the route Pausim mentions?
Trevor

Examining my CBE system it would appear that the system charges both batteries so wonder if the debate about B to B is necessary. The display panel shows both being charged when the engine is running with a symbol for the two batteries.

 

[JockandRita]

Examining my CBE system it would appear that the system charges both batteries so wonder if the debate about B to B is necessary. The display panel shows both being charged when the engine is running with a symbol for the two batteries.

Having run the 4 x 80A Gel batteries down quite a bit (intentionally), and with very little solar output, the highest reading I have seen on the CBE panel from the alternator charging was 37A.
After a 7 x hour drive, we plugged into the EHU. The onboard charger was pushing in just over 16A. 24 x hours later, that charge was down to 3.5A.
This leads me to believe that the fitting of a 60A B2B is still necessary, and something I have been contemplating for sometime, but just wasn't sure of the output from the alternator, until now.

Although it is a 90A alternator (same as was on the Hymer), I was only getting just over a third of that, even with the starter battery fully charged, and no other power usage to the prime mover, ie, lights or heater etc.

Enquiries indicate that a 130A replacement alternator is available, so I might go down that route when it needs replacing.

Cheers,

Jock.

 

[Ian Bosman]

Surely you would expect that after 24 hours the charge pushed in would be lower as you have just been pushing the 16Amps. With batteries getting on a bit you will never get down to zero charge

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[JockandRita]

Surely you would expect that after 24 hours the charge pushed in would be lower as you have just been pushing the 16Amps.

It was Ian, ie................

24 x hours later, that charge was down to 3.5A.

With batteries getting on a bit you will never get down to zero charge

When fully charged, we often get a reading of zero charge on the panel. As soon as you turn something on, a charge registers immediately, until fully charged again.

I'm not sure how old the 4 x batteries are, but will find out hopefully.

Cheers,

Jock.

 

[Driventemple]

Having run the 4 x 80A Gel batteries down quite a bit (intentionally), and with very little solar output, the highest reading I have seen on the CBE panel from the alternator charging was 37A.

I presume this is with a B2B installed?

 

[JockandRita]

I presume this is with a B2B installed?

No, not yet.
I do have the B2B and all the kit needed to install, I just put it off hoping that the alternator and cabling were large enough to give me 40 x plus amps.

Cheers,

Jock.

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[andy63]

Examining my CBE system it would appear that the system charges both batteries so wonder if the debate about B to B is necessary.

well the battery to battery does ensure a proper regulated charge to the leisure batteries( like fitting a modern smart charger ) regardless of alternator voltage which can vary considerably with smart alternators and result in the leisured never really been fully charged by driving alone..
some vans have inadequate wiring from start to leisure batteries which further reduces the potential of the alternator..
Andy

 

[Insider]

Hi.. Insider after reading your post I had a look at my system...which I've been exploring on and off for a few months now..
I had obviously missed the possibility of such a simple solution that you had suggested..
Gave it a try this morning..a few min work to remove one wire.. works perfectly and can't see any drawback on my particular system..
Cheers..
Andy..

Andy,

ran a test yesterday. Found the feed from the battery to the EC400 and disconnected. Powered on the control panel and all as expected - no vehicle battery but everything worked as expected. Ran the van and saw 10Amp coming from the leisure battery when I put the fridge onto 12V - this made me happy as when the B2B is fitted this would be supplying that 10A as well as charging the leisure batteries with the potential other 50A. Problem was today I decided to connect up the EHU and run the same tests. Nope - on EHU when the vehicle battery disconnected the control panel would start and then stop - every time I started.


To Andy and everyone else!!
Pauism has mentioned that the leisure battey charge would feed back into the vehicle battery on post #15 but I can't see that happening(but will stand corrected as I'm a 12V newb). Anytime I look at their voltages via the EC400 display they are alway different. I presume there's a diode in there somewhere to prevent that sort of thing happening. What would worry me is the charging profile of the Sterling could be affected by the voltage\current coming off the EC400 while driving as the EC400 is also charging. Thinking out loud the sterling is charging on bulk and the EC400 is also feeding in a resonable high voltage with a good few amp. Would the sterling not think that job done, time to go over to float as I see a decent voltage here on the leisure battery? Hence a relay on the EC400 now would make sense.

I think Sterling alluded to this yesterday but to be honest I didn't understand half of what was said to me as it was rushed. I do have a query into Sargent at the moment and hopefully will hear from them tomorrow but TBH if I am right then it is nothing wrong with either of their systems, just how to marry them as one is not fully adequate due to budgetary/design contraints.

 

[andy63]

Andy,

ran a test yesterday. Found the feed from the battery to the EC400 and disconnected. Powered on the control panel and all as expected - no vehicle battery but everything worked as expected. Ran the van and saw 10Amp coming from the leisure battery when I put the fridge onto 12V - this made me happy as when the B2B is fitted this would be supplying that 10A as well as charging the leisure batteries with the potential other 50A. Problem was today I decided to connect up the EHU and run the same tests. Nope - on EHU when the vehicle battery disconnected the control panel would start and then stop - every time I started.

trying to follow... so your fridge works on 12v direct from leisure batteries when your engine is running...
but on ehu the fridge is not running on 240v.. is that correct?
and are you saying your control panel switches off when you start your engine...that is normal on some vehicles ...no hab electrics when on the move..

as for the point about disabling the split charge system to install a battery to battery charger, ive already commented on that after installing my Stirling battery to battery... I have disconnected the split charge system first by installing a relay as suggested by pausim, and later by disconnecting the vehicle battery loop as you mentioned.. I missed that easier option at the time.. so easy to get wrapped up in things and miss the obvious....
but I did have a play around and had both charging sources running side by side ...my conclusion was its does no harm.. and imagine from reading some posts that there may be quite a few battery to battery installs that have been done without disabling the split charge loop..
hope you can get a satisfactory solution and I think the one reached by pausim of installing a relay in the split charge loop may be your best option if a simpler solution isn't available...
Andy

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[Driventemple]

and are you saying your control panel switches off when you start your engine...that is normal on some vehicles ...no hab electrics when on the move..

I think this is standard on UK manufactured vehicles in order to comply with NCC Rules.

 

[Insider]

trying to follow... so your fridge works on 12v direct from leisure batteries when your engine is running...
but on ehu the fridge is not running on 240v.. is that correct?
and are you saying your control panel switches off when you start your engine...that is normal on some vehicles ...no hab electrics when on the move..

as for the point about disabling the split charge system to install a battery to battery charger, ive already commented on that after installing my Stirling battery to battery... I have disconnected the split charge system first by installing a relay as suggested by pausim, and later by disconnecting the vehicle battery loop as you mentioned.. I missed that easier option at the time.. so easy to get wrapped up in things and miss the obvious....
but I did have a play around and had both charging sources running side by side ...my conclusion was its does no harm.. and imagine from reading some posts that there may be quite a few battery to battery installs that have been done without disabling the split charge loop..
hope you can get a satisfactory solution and I think the one reached by pausim of installing a relay in the split charge loop may be your best option if a simpler solution isn't available...
Andy

Andy

When I disconnected the vehicle battery and started the van engine I decided to run the fridge on 12V as would be normal while driving. The fridge ran and while it was running I saw 10A leaving my battery via Victron BM. I turned off the fridge but left the van running and the 10A dropped to almost 0. This is all normal and I only mentioned it in passing. In normal circumstances the power would be coming from the alternator, via the vehicle battery but since I had broken the circuit the power came from the leisure batteries. While this would not be sustainable, if I fitted a B2B it would be fine as it would continue to operate as normal.

What surprised me was what happened on EHU. I did not start the engine while on EHU - I think there might be a bit of misunderstanding there seeing your response. I do type faster than I think and I'm not a fast typist!! My control panel would power on and then off immediately while on EHU, with the vehicle battery disconnected and the van engine turned off and the key out of the ignition. This was unexpected and means that I cannot use the simple solution of disconnecting the vehicle battery.

Short term solution is to order the B2B, install it and monitor its performance. Long term approach would be to use the approach suggested by Pauism if the charging performance does not seem right.

Thanks

Rory

 

[Insider]

I think this is standard on UK manufactured vehicles in order to comply with NCC Rules.

Misunderstanding somewhere of what I was saying. The test was being done while on EHU with engine shut off which is what surprised me. 12V systems take a lot more understanding than I had thought at first!!

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[andy63]

Hi Rory..
im with you now..
in spite of the panel behaving as it did when on mains did your fridge run on mains anyway..
I cant offer an explanation for the control panels behaviour im afraid..
My control panel takes its supply from a tapping in the main leisure battery relay which is a separate item from the cbe distribution unit..And it does not switch on or off without a manual press of a button..
What I do know is my charger has a sense wire that supplies the cbe distribution unit and is responsible for one or two functions..but can't think how that would cause your issue you have even if your charger had a similar feed to your Sargent..
The more you play around with the system and wiring the more will be revealed..
Andy..

 

[Pausim]

Short term solution is to order the B2B, install it and monitor its performance. Long term approach would be to use the approach suggested by Pauism if the charging performance does not seem right.

Some people argue that the B2B will run fine without any intervention because the voltage drop in the wiring means that by the time the loop gets back to the engine battery the voltage has fallen. My motorhome is wired up with good sized cables so I did not want to rely on this. My guess is that your leisure battery will get a good charge with no intervention but the B2B will be less good at monitoring the battery and knowing when to shut down, so probably less efficient.

Having a LiFePO4 leisure battery which I want to look after I decided to find a separating solution that suits me. If you have a smart alternator then I would think it important to separate the systems because the ECU may try to reduce the voltage of the engine battery.

Anything that makes the alternator work harder than it needs to is something I want to avoid. I have been told they use about 5hp under full load and that obviously has to be paid for in power available for driving and fuel used. A smart alternator ECU takes care of this by removing the load when it is needed for driving and increasing the load when slowing down, using the vehicle‘s momentum to charge the battery.

 

[andy63]

. My guess is that your leisure battery will get a good charge with no intervention but the B2B will be less good at monitoring the battery and knowing when t

That appears to be why a lot of people are happy to do it without any separation..
I mentioned earlier that while experimenting with the two systems..ie split charge and battery to battery.. and monitoring the current flow on a separate monitor the split charge system provided a higher current flow than the battery to battery as it was operating at a higher voltage than the output of the battery to battery on its particular charging profile..
As soon as the battery to battery charger becomes the dominant source when I switched the split charge loop out the battery to battery continued to charge at its lower rate and moved straight to the particular part of its charging cycle that was required..in my case the float charge as the leisure batteries were well charged at the time..
Andy

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[RogerIvy]

I did go down the route of fitting a relay in the hab battery circuit so it would disable when the engine was running and the battery to battery was active..but as I said above..I did fit a switch in the relay coil circuit so that I could try various options..

Interesting stuff.

Any reason why you didn't try a diode approach instead of a relay?
I'm not familiar with current specs, particularly how much power you lose going through a diode. But if the loss is negligible it would make more sense than a relay in some ways.

 

[andy63]

Any reason why you didn't try a diode approach instead of a relay?

Sorry..you have last me there..we were discussing the various methods of disabling/isolating the split charging curcut that is normally in place to charge leisure batteries.
One option was to fit a normally closed relay in that circut and activate it using an engine run signal..
Can't see how a diode would achieve that result..it is in its standard form only a electrical non return valve so to speak..

On the power loss front..a silicone diode drops the voltage by around 0.6 or so of a volt I believe ..but in any case it not what I would use to achieve what we were discussing..
Hope ive not missed the point ..
Andy..

 

[Pausim]

Interesting stuff.

Any reason why you didn't try a diode approach instead of a relay?
I'm not familiar with current specs, particularly how much power you lose going through a diode. But if the loss is negligible it would make more sense than a relay in some ways.

A diode would interrupt the trickle charge from the mains charger to the engine battery when on a hook up. The relay only cuts in when the alternator is running.

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[RogerIvy]

Sorry..you have last me there..we were discussing the various methods of disabling/isolating the split charging curcut that is normally in place to charge leisure batteries.
One option was to fit a normally closed relay in that circut and activate it using an engine run signal..
Can't see how a diode would achieve that result..it is in its standard form only a electrical non return valve so to speak..

On the power loss front..a silicone diode drops the voltage by around 0.6 or so of a volt I believe ..but in any case it not what I would use to achieve what we were discussing..
Hope ive not missed the point ..
Andy..

Andy, I was thinking of something like a zener diode that would allow current flow from the batteries to the EBL to do stuff like monitoring and when you're not driving (to run habitation electrics etc).
Being a one-way diode it could prevent the EBL from charging the batteries, thereby leaving it all to the B2B without interference.
However, last I know the half a volt of loss through the diode would be too much - I've not kept up to date with advancements. If the loss was only 0.2v maybe a diode would be a consideration.
Of course, a relay doesn't reduce the voltage ... hence why we go this route, but a relay means that the EBL can't monitor batteries etc.
Rog

 

[RogerIvy]

A diode would interrupt the trickle charge from the mains charger to the engine battery when on a hook up. The relay only cuts in when the alternator is running.

I was thinking of placing the diode between the EBL and batteries, but not between the onboard charger and batteries and not between the solar regulator and batteries. Just a thought, but upon doing some research the v drop is too much using a diode.

 

[Pausim]

I was thinking of placing the diode between the EBL and batteries, but not between the onboard charger and batteries and not between the solar regulator and batteries. Just a thought, but upon doing some research the v drop is too much using a diode.

I thought the charger was inside the EBL so clearly there is something I am missing.

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[RogerIvy]

I thought the charger was inside the EBL so clearly there is something I am missing.

In our case the ehu charger is a stand-alone item easily identifiable and reasonably easy to isolate and/or replace with a more modern Li-compatible unit. I think there are some things attached to the EBL for monitoring purposes that we'll need to ditch.
But the charger from the engine is something else ... we'll need to ID the cable and insert a relay.

 

[Pausim]

It looks like you have some CBE components so perhaps you have a CBE distribution box rather than an EBL which is a Schaudt product.

 

[RogerIvy]

It looks like you have some CBE components so perhaps you have a CBE distribution box rather than an EBL which is a Schaudt product.

Unfortunately you're correct. In the past I've found Schaudt to be very helpful.
CBE don't bother answering emails (same as Votronic). At least Euramobil tell you to sod off in the nicest way possible!

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[Pausim]

Unfortunately you're correct. In the past I've found Schaudt to be very helpful.
CBE don't bother answering emails (same as Votronic). At least Euramobil tell you to sod off in the nicest way possible!

Yes Schaudt are very helpful and I am still waiting for CBE to respond to an an email I sent them in 2019. Very different attitudes.