B2B preference

[Pausim]

Looks like it is back to school for me.

 

[G-RMPS]

Thanks for the explanations on how surplus alternator capacity is used to optimally charge the cab and leisure batteries. Now, with the engine off and EHU does the B2B work "in reverse" to maintain both batteries?

With the engine off, and no EHU, but a solar panel fitted does the same logic apply? Which battery gets priority?

 

[DBK]

Thanks for the explanations on how surplus alternator capacity is used to optimally charge the cab and leisure batteries. Now, with the engine off and EHU does the B2B work "in reverse" to maintain both batteries?

With the engine off, and no EHU, but a solar panel fitted does the same logic apply? Which battery gets priority?

No is the answer to both. I think this is because the B2B doesn't sense sufficient difference between the voltages of the cab and leisure batteries.

 

[G-RMPS]

Thanks. So does a Battery Master do this? If so, is it desirable/necessary to have a B2B setup and a Battery Master?

 

[Deneb]

No is the answer to both. I think this is because the B2B doesn't sense sufficient difference between the voltages of the cab and leisure batteries.

My Votronic 1212-30 (and possibly other Votronic B2Bs although I have no knowledge of them) supplies a trickle charge to the vehicle battery from the leisure batteries as long as it has been wired to operate from a D+ signal (required for smart alternators, otherwise optional but provides greater charging ability than wiring for pure voltage sensing control). Up to 1A current is supplied to the vehicle battery when the ignition is off and the voltage at the leisure batteries is greater than 13.1 volts (13.5 volts for LiFePO4 charging program).

So it will be active when on EHU or via solar charge whenever the leisure battery voltage is sufficiently high. The function is disabled if it has been installed in pure voltage sensing mode, without a D+ signal.

Edit: Just realised G-RMPS also asked a second question - the Votronic solar controllers also send a small current (up to 1A on the MPP controllers, up to 0.8A AFAIR on the SR range) to the vehicle battery when conditions are optimal, as they prioritise the leisure battery charging. I found this function perfectly adequate to maintain the vehicle battery when the van is parked up on my drive.

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[nicholsong]

Have you seen Charles Stirling on You Tube?

Excellent videos

Charles Sterling demonstrates that the old 'chalk and talk'(now whiteboard and marker) method by an well-qualified engineer can be as effective as highly-produced graphics and videos.

It reminds me of the Aviation Engineer who conducted our technical course on the Boeing 737 - so much better than Boeing's video. And we could ask questions and get clarification on anything us 'thick' pilots did not get first time. He too was Irish.

I also liked some of Charles Sterling's comments - like 'why do they save £200 on a £80,000 MH?' Of course one answer is to sell you an 'Extra' of a B2B which they will charge £2,000 for fitting - we fitted ours for approx. £250.

Geoff

 

[Pausim]

My Votronic 1212-30 (and possibly other Votronic B2Bs although I have no knowledge of them) supplies a trickle charge to the vehicle battery from the leisure batteries

The Votronic 1212-45 is the same but if it has been wired through a separation relay or EBL it becomes isolated and will not be able to trickle charge. In other words it needs a direct connection to both engine and leisure batteries for this function, a Battery Master would overcome the problem.

 

[Diabalo]

There are a lot of variables, what with all the different systems, different batteries and different split charging. For me with an Autotrail Sargent say not to fit a battery master as it will interfere with the way their setup charges the Hab and vehicle batteries. I am waiting on a response from them around fitting a B2B charger.

 

[AMK]

So I thought I would have a measure up yesterday for a B2B.

Then I came across my first head scratcher.

I have an Elddis encore 255 and the two batteries at the back of the van.
Although I have two batteries the wires don’t parrellel from battery to battery on a short live and neg. The live and neg actually run alll the way back to behind the fuse box for both batteries.

With this in mind do you think it’s still ok to run the B2B live and Neg to live on one and neg on the other.

I suppose what I’m asking is, because the batteries are factory wired in parrelel this way will it still be ok to fit the B2B,

Anyone else come across this problem.

Cheers Alan

 

[Diabalo]

Alan

My Autotrail is exactly the same and I'm not sure what to do for the best. When I trace the wires back to the Sargent PSU each of the separate battery leads plugs in separately. I suppose I could join the 2 together at the PSU side and run a new cables down to the batteries and parallel them up in the normal way, that would be easy for me as the the batteries and PSU are reasonably close to one and other.
Another thing for me is the split charging is built in the sargent |PSU and Sargent advised me this week that the Vehicle battery link into the PSU would need to be broken by a relay when the engine is running or else the whole thing will get it knickers in a twist.

Nothing is simple,is it?

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[AMK]

Alan

My Autotrail is exactly the same and I'm not sure what to do for the best. When I trace the wires back to the Sargent PSU each of the separate battery leads plugs in separately. I suppose I could join the 2 together at the PSU side and run a new cables down to the batteries and parallel them up in the normal way, that would be easy for me as the the batteries and PSU are reasonably close to one and other.
Another thing for me is the split charging is built in the sargent |PSU and Sargent advised me this week that the Vehicle battery link into the PSU would need to be broken by a relay when the engine is running or else the whole thing will get it knickers in a twist.

Nothing is simple,is it?

Frustrating When a simple job turns out like this.

Hopefully we can get some advise from a funsters that’s already fitted one to a system like this.

 

[autorouter]

Excellent videos

Charles Sterling demonstrates that the old 'chalk and talk'(now whiteboard and marker) method by an well-qualified engineer can be as effective as highly-produced graphics and videos.

These videos are good, but I wouldn't say excellent. He talks about a '100 to 200 amp battery', as if he wanted the charging current to be 100 to 200 amps.

The recommended charging current for a 100 to 200 amp-hour lead-acid battery bank is C/5, which is 20 to 40 amps.

 

[nicholsong]

These videos are good, but I wouldn't say excellent. He talks about a '100 to 200 amp battery', as if he wanted the charging current to be 100 to 200 amps.

The recommended charging current for a 100 to 200 amp-hour lead-acid battery bank is C/5, which is 20 to 40 amps.

I was not endorsing his figures, which I have not checked, nor the video, but just his explanation of why any B2B system boosts the charging from the alternator to the leisure batteries. Which they do.

Geoff

 

[Diabalo]

Another thing I don't understand with all this is, with decent sized wiring and heavy duty split charge relay the alternator will be putting out far more amps directly to the batteries then then say a 30 amp B2B charger will be. What am I missing?

 

[JockandRita]

Another thing I don't understand with all this is, with decent sized wiring and heavy duty split charge relay the alternator will be putting out far more amps directly to the batteries then then say a 30 amp B2B charger will be. What am I missing?

My take on it Dane, is in conditions when the alternator is feeding the headlights, heated mirrors, heater fans, air con, etc, and maybe not able to give enough charge to the leisure batteries, that's when the B2B comes into it's own, as it boosts whatever it is getting, to 60A, in the case of the unit I would want to fit.
I had the 50A model for several years, and it did in a 2-3 hour drive for my leisure batteries, what my 90A alternator wasn't doing. When I got home and plugged in to EHU, the batteries would then take the final low amp conditioning charge for a few hours, before going on to a maintenance trickle charge.
Before fitting the B2B, that mains charge would be a high one, and sometimes take almost 24 hrs to come down to a trickle charge.

Cheers,

Jock.

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[Raul]

A B2B is necessary if you got a new style smart alternator, usually euro6 up for diesel on vans. Also if you charge different chemistries: I.e. starter lead/ house Lithium.
otherwise old alternators work well with split charge on lead.

 

[Diabalo]

A B2B is necessary if you got a new style smart alternator, usually euro6 up for diesel on vans. Also if you charge different chemistries: I.e. starter lead/ house Lithium.
otherwise old alternators work well with split charge on lead.

My understanding is that smart charging/regenerative braking is disabled for motorhomes,

 

[Raul]

It may be, but on PVC it’s there. I know I got it, and I charge lithium. In my case is necessary.
If I would had old style alternator and lead for the house batt, then a auto sensing HD relay would of been my choice.

 

[Pausim]

My understanding is that smart charging/regenerative braking is disabled for motorhomes,

Not all. Mercedes based motorhomes have been using smart alternators for a few years now. Fiat were disabling theirs but now that they are no longer allowed to cheat the emissions figures I suspect the new ones will be active.

Another thing I don't understand with all this is, with decent sized wiring and heavy duty split charge relay the alternator will be putting out far more amps directly to the batteries then then say a 30 amp B2B charger will be. What am I missing?

A B2B will keep the charging voltage matched to the needs of the leisure battery, including the bulk, absorption and float stages.

 

[Diabalo]

Thanks for everyone's patience I think I'm getting there now, (I HOPE SO) Oi who said that
so as my current split charge system is in-built in my Sargent PSU and it does not work that well and the way I see it I have 2 choices to improve it, 1. a beefed-up split charge relay and wiring or 2. a B2B charger like a Sterling for example.
Both options can be automatic voltage sensing to kick them into life or by a live feed when the ignition is switched on. I have been advised by Sargent that when using the B2B or extra SCR I would have to break the connection between the Vehicle battery and PSU save upsetting it. This is easy enough with a relay but what would I need to do when on hook up? As my PSU has a smart charging function where it can charge either the Hab or the Vehicle battery so I foresee a problem when on EHU and the PSU starts charging the vehicle battery the additional SCR or B2B charger would fire up. Or have I over thought this.

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[Pausim]

Use D+ the B2B will only activate when the alternator is charging.

 

[Diabalo]

Use D+ the B2B will only activate when the alternator is charging

Crikey that was a quick reply.

When you put it like that it's really simple.

Thanks for yours and everyone else's help.

Now where's me credit card before the OH gets in

 

[Robert Clark]

Use D+ the B2B will only activate when the alternator is charging.

That’s what we did

 

[Lenny HB]

Another thing I don't understand with all this is, with decent sized wiring and heavy duty split charge relay the alternator will be putting out far more amps directly to the batteries then then say a 30 amp B2B charger will be. What am I missing?

You are not missing anything.
With one of my Hymer's when I managed nearly flatten the lesiure batteries they were charging at 44 amps with the standard split charge setup.
But where the charge rate will fall off rapidly as the battery voltage rises the B2B will pump more amps in for longer. So if you are a heavy power user a B2B could still be worthwhile.

 

[SomeoneElse]

I removed my Sterling battery maintainer, solar controller and disconnected my leisure battery and habitation controller from the engine battery and installed a Votronic triple with 16mm2 cables to both batteries.
This gives me a 45A B2B when driving, a EHU of 30A of which upto 4A goes to engine battery and an MPPT controller when on solar. Again with upto 4A to the engine battery. All this with 8 different battery types selectable, four lead acid and four lithium. The Votronic is a quality product the EHU can be used world wide and automatically works anywhere with 90 to 270Volts.

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[Deneb]

A B2B is necessary if you got a new style smart alternator, usually euro6 up for diesel on vans. Also if you charge different chemistries: I.e. starter lead/ house Lithium.
otherwise old alternators work well with split charge on lead.

I only have a 30A B2B, but monitoring it with my BMV, it puts out around three times the current that the original split-charge relay on my van could manage.

 

[Raul]

Same battery and same wiring? If yes then your B2B outputs a higher voltage than the alternator can manage.
I dad a Durite in the past on the work van, changed it for a victron cyrix.

 

[Deneb]

Same battery and same wiring? If yes then your B2B outputs a higher voltage than the alternator can manage.
I dad a Durite in the past on the work van, changed it for a victron cyrix.

Same batteries but new wiring. Converter connected the split charge relay to the main power cable in the bodybuilders socket, which runs half way round the cab to the vehicle battery. I wired the B2B direct to the hab and vehicle batteries with heavier cable and a run about a third of the distance.

 

[Raul]

Then is NOT a even comparison. Since ohms law tells us that the current will follow to the least resistance path, your new improved conductors have contributed to better current flow and better power transfer. The old wiring could of been the bottle neck, or simply to much of voltage drop reaching the battery.
You can only push more amps by overcoming the internal resistance with raising the voltage. Hence why for a optimum charge the voltage drop is critical.

 

[Deneb]

Then is NOT a even comparison. Since ohms law tells us that the current will follow to the least resistance path, your new improved conductors have contributed to better current flow and better power transfer. The old wiring could of been the bottle neck, or simply to much of voltage drop reaching the battery.
You can only push more amps by overcoming the internal resistance with raising the voltage. Hence why for a optimum charge the voltage drop is critical.

It's only a comparison in as much as I suspect many converter provided split charge relays are similarly installed such that ease of installation and cost are prioritised over performance.

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