Is a B2B charger what we need?

Feb 22, 2016
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Have been following various threads on here about B2B chargers or alternator/battery chargers and have ended up confusing myself (actually, not that difficult). Our 2012 Bailey has only one leisure battery, a Varta 105ah. There is a 120w solar panel that feeds to a dual controller so that the engine battery and leisure battery receive a charge, weather permitting.

We stay on a mixture of aires with no ehu and campsites with ehu. Due to cost, we want to minimise the amount of time spent on paid sites. Because we have only the one leisure battery, we feel a little vulnerable if we have a few days of cold overcast weather and so head for a site with ehu. From some of the posts, it seems that fitting a B2B charger won't bring much to the table in terms of charging capacity but our situation seems by other posts to be the very reason to fit a B2B. I am unclear how such a charger would interrelate with the solar charger. The latter is a Sunworks dual controller and has worked very well. We recently bought a brand new Varta leisure battery and are currently enjoying a stay on a Portuguese site with ehu. But from Monday we are moving east to Spain but will not be doing long drives, so there will be little charging by the alternator. In these circumstances, would a charger be a useful addition?
Many thanks.
 
Feb 9, 2008
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You need to do the maths to work out your energy consumption or at worst do an estimate. Basically, the B2B charger works when your driving and a Solar Panel works when your stationary. (My 2011 Autotrail does not have a B2B charger fitted but the Alternator pit's in up to 9 Amps when on tick over depending on the battery state, I would measure what your getting with your set up before splashing the cash).
I have a similar set up to you, 125W S.P. on the roof and 2x100AH leisure batteries and we spend most of our time off Campsites and manage more than adequate. Last year I purchased a 120W suitcase S.P. which we use in the winter months when the days are short and when connected keeps our battery bank fully charged. We find it's not needed in the summer when the days are longer. I would guess more S.P. is the way forward and possibly another leisure battery.

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JJ

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Have you actually run out of electric whilst in Portugal with 120 watts of solar power feeding a new Varta leisure battery?

I fulltime around Portugal with approximately the same solar production but with two leisure batteries.

I have a B2B charger which I no longer have fitted as it turned out not to be needed.

If going for the B2B route, I believe you need to be able to switch off the solar charge when running the engine, otherwise the B2B will read the solar panel output voltage and, thinking the battery is full, won't put any more charge into it.

I am near Silves if you want to check out my no longer needed Sterling B2B charger. It is only 20 amps though.


JJ :cool:
 

Lenny HB

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First step is to boost your storage capacity by adding another one or two batteries, no pont in having better chagre rates if you have nothing to store the power in. First choice then would be more solar and fit a decent MPPT solar regulator.
You could significantly improve your engine charging by fitting the correct size cables, British built vans are notorious for fitting well undersized cables. Replace the cables to the split charge relay and battery with at least 16mm sq cables and you should a big improvement.
If you go down the B2B route have a look at the Votronic unit a bit dearer than the Sterling but a much better bit of kit.

My set up is 3 x 80a/h gel batteries, 300 watts of solar with a MPPT regulator and a Sterling B2B. I only fitted the B2B as I picked up an almost new one on eBay for £130 if I was buying one at full price I would have bought the Votronic one, the Sterling is a pig to set up.
Standard charge from the split charge in the Hymer is an intial 22 amps dropping to 10 amps as the batteries resistance rises, the B2B gives an initial 40-49 amps dropping to 20-35 amps depending on state of the battery.
 

Lenny HB

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If going for the B2B route, I believe you need to be able to switch off the solar charge when running the engine, otherwise the B2B will read the solar panel output voltage and, thinking the battery is full, won't put any more charge into it.

I am near Silves if you want to check out my no longer needed Sterling B2B charger. It is only 20 amps though.
The B2B works on sensing the starter battery voltage, solar shouldn't effect it. The latest ones have an ignition control, I wired the control to the alternator D+ relay so it only works with the engine running, this stops it cycling when the engine is not running if you have solar.

A 20 amp B2B would give no advantage over the standard Hymer setup as Hymer use decent size cables for the split charge.

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OP
Ingwe
Feb 22, 2016
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Have been following various threads on here about B2B chargers or alternator/battery chargers and have ended up confusing myself (actually, not that difficult). Our 2012 Bailey has only one leisure battery, a Varta 105ah. There is a 120w solar panel that feeds to a dual controller so that the engine battery and leisure battery receive a charge, weather permitting.

We stay on a mixture of aires with no ehu and campsites with ehu. Due to cost, we want to minimise the amount of time spent on paid sites. Because we have only the one leisure battery, we feel a little vulnerable if we have a few days of cold overcast weather and so head for a site with ehu. From some of the posts, it seems that fitting a B2B charger won't bring much to the table in terms of charging capacity but our situation seems by other posts to be the very reason to fit a B2B. I am unclear how such a charger would interrelate with the solar charger. The latter is a Sunworks dual controller and has worked very well. We recently bought a brand new Varta leisure battery and are currently enjoying a stay on a Portuguese site with ehu. But from Monday we are moving east to Spain but will not be doing long drives, so there will be little charging by the alternator. In these circumstances, would a charger be a useful addition?
Many thanks.

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OP
Ingwe
Feb 22, 2016
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Thank you for posting. I have posted previously about the feasibility of another leisure battery. There is no space in the current battery tray but don't know whether a second battery could be fitted elsehwere.

@JJ we are very close to Silves (Mikki's place) and thanks for your kind offer to look at your B2B. At the moment, we haven't had a problem yet with electricity on this trip but am always looking ahead in case. For the moment, will see how we do with our existing solar and leisure battery. When we get back to Blighty, will look at what the alternator puts out and whether upgrading the cables would be worthwhile.
More solar is always preferred but as was pointed out, pointless if no capacity to store it i.e. another leisure battery.
More research needed but thanks all for the pointers.
 

JJ

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The B2B works on sensing the starter battery voltage, solar shouldn't effect it. The latest ones have an ignition control, I wired the control to the alternator D+ relay so it only works with the engine running, this stops it cycling when the engine is not running if you have solar.

A 20 amp B2B would give no advantage over the standard Hymer setup as Hymer use decent size cables for the split charge.

But OP says his engine battery is also connected to his solar system so it would "read" that too...

Correct about the 20 amp being a tad low though... ;)

JJ :cool:
 

Lenny HB

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But OP says his engine battery is also connected to his solar system so it would "read" that too...
If using one of the older units without the ignition control it is best to fit a relay on the output of the B2B that is switched from the D+ or the ignition. Most people fit them not relising that they will just keep cycling without some form of switching. The solar will take the engine battery voltage up and the B2B turn on, engine battery voltage drops, B2B turns off, solar take Engine battery back up and so on.

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two

Aug 4, 2011
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A B2B can recharge hab batteries on much shorter journeys, or even just idling the engine (using it as a generator), but you might achieve a good enough result by beefing-up the wires from the alternator (via the split charge relay) to the battery.
I suggest you get a battery monitor first, though. then you will be able to see how much charge there is in your battery and how close to 'empty' you are actually getting. You may not need anything more but, if you do, you should have an idea of how much extra charge you need and then where to get it from.
 
OP
Ingwe
Feb 22, 2016
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@rogher-is the upgrading the cable from the alternator something I could do myself? And is a battery monitor something I can permanently fit?

It is the recharge of the hab battery that attracts me to a B2B.
 

Lenny HB

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@Ingwe If you look at my post No5 you will see what you can expect from upgrading the wiring .
Yes it easy to do as all you need to do is follow the path of the existing wiring replacing it with heavier cable or running an additional cable in parallel. You will also need to replace the wiring from the split charge relay to the battery.

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two

Aug 4, 2011
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@rogher-is the upgrading the cable from the alternator something I could do myself? And is a battery monitor something I can permanently fit?

It is the recharge of the hab battery that attracts me to a B2B.


I've not actually done that as I went the B2B route. I also don't know your capabilities. However, the difficulties you might meet might be routing the thick wires and then terminating them properly (crimp machine & heat shrink required).

A battery monitor is not too difficult to do, either. You may need to amend your circuits a bit. Everything needs to pass through a common shunt or you're wasting your time (I fitted Victron).
 

DABurleigh

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I have a 50Amp Sterling B2B for sale, but offer the following advice in your situation:

1) More battery Ah is a priority.
2) Check your alternator charge rate into your leisure battery depleted by at least 50%. With decent cabling, plenty should be on tap, but with just a single battery, thinner wiring may have been used to protect battery life. For maximum life, the maximum charge rate in Amps should be no greater than one fifth of the capacity in Amp-hours.
3) With decent cabling and a depleted battery, a B2B will buy you nothing, initially.
4) As more charge gets into the battery (say 30-40% depleted) the B2B will give a charge rate streets ahead of just the alternator direct to leisure battery. This phase can be important in maximising the utility of short journeys between overnight stops.
5) Finally, though the charge rate will drop off as the battery gets charged further, the B2B can give your leisure battery a greater capacity than just the alternator would.

In sum, a B2B can maximise the utility of your battery capacity when touring off EHU with limited solar charging. But don't think it is necessarily any better than simply doubling your battery capacity to start with, plus checking you have decent cabling between alternator and leisure battery.

Dave
 
Jan 28, 2008
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an extra battery would on its own double your time off grid ab2b only works whilst travelling or running engine
we have two varta batteries and 189 solar and weve never run out just done 3 months france spain and portugal that was with normal usage and maybe 90 mi9ns tv each night

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OP
Ingwe
Feb 22, 2016
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Wow, plenty of excellent advice here. I think my DIY skills are not up to changing the alternator cable/relay etc.
I will seriously see whether a second battery can be fitted. This seems key.
I will also try and gauge our usage.
Thanks all
 

TerryL

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When I had a second leisure battery fitted there was no room in or near the original so I obtained another through-floor battery box from Cak Tanks (?) in Kenilworth and it went under the seat on the other side of the van. Not ideal as the connecting leads were not as short as ideal but have had no problems. Incidentally all the new cables had fuses at both ends.

Just to add to the debate, I've also got a Sterling B2B charger, 100w solar panel and a battery master. Never had a flat battery since, leisure or engine.

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Minxy Girl

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Since 1996 we've had Elddis, Swift, Rapido, Rimor, Chausson MHs and Autocruise & Globecar PVCs
We have a 60w semi-flexible solar panel and two 95amp leisure batteries and don't run out of juice and we only ever wild camp or use aires (without hook-up) for 7 weeks at a time.

So get a second battery fitted to match your new one and you'll have more 'input' capacity than us!
 

two

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The best way to get more out of batteries is to take less out(!)
There's only a modest amount of power available. They'll last longer if you can be frugal.
 

haganap

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Hi.
There is a lot of contradicting advice on here so all I am going to give you is my own opinion over many years of B2B usage. You can take it or dismiss it because every poster above has posted with only their own needs and you don't know what your needs are.
firstly. Don't change the wiring, don't listen to the Brit van wiring argument, it doesn't exist these days and if it does the voltage drop is minimal and I mean minimal, what ever charging unit is in your van will be provided, Sorry Lenny and others, it's too old school, and on top of this, if you were going to fit a B2B it would be pointless in changing it anyway.
I have had numerous conversations with Charles Sterling over the benefits of a B2B and have had @jonandshell fit me one with all sorts of relays etc which is the correct method but doesn't mean there isn't another way.
People are talking about adding solar, I have 180w of solar on my van and yesterday in a cold wet miserable day in paradise (North West England) I got basically zilch, diddly squat and all I had on was a few lights (it gets dark early) so depending on where you are going to be enjoying your motorhoming there is no point in adding solar unless of course you are going to be like @mitzimad has been and hanging out down in sunny Spain.

The best bit of advice you have had is to do add two batteries initially. I know you said you struggle for space but it doesn't matter you need to find space... work on it you will find somewhere.

Then having done that see how you go, if your power usage outweighs your batteries then consider a B2B or better still an A2B charger.

I have just refitted in to my new van because basically we are not touring around the south or hotter countries we are in the dark and dingy UK. Once Nikki has ran a hairdryer off the inverter used high power straighteners and then we've tucked in to bed with the heating (was blown air now alde) we can could wake up in the morning with two 100am semi traction batteries already dead.
Therefore the B2B serves two things.
One, it ensures that when we arrive the batteries are topped up to where they should be with it's intelligent charging system.
Secondly, By running the engine with Nikki drying and making her hair look beautiful I can pretty much balance out (or prevent most consumption) if we are staying somewhere a few nights.
My b2b is a 50 amp modern system, I run it with a NASA BM so I can accurately justify all my comments above.

But as said, go with another battery or even as bigger one you can get in your compartment, then see where you are. You might not need a B2B you may not need another Solar and until you have had the years of experiencing the kind of travels and usage you are going to do will never know.

Mine comes from years of kids with laptops (too old they don't come but Nikkis hair is now the issue), using the MH wild camping all year round and skiing with our Motorhome for over 10 years.

I took the one off my last van after reading I didn't need one, I lasted 3 trips before putting it back in, good job I never sold it!!!! although I did try

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Lenny HB

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firstly. Don't change the wiring, don't listen to the Brit van wiring argument, it doesn't exist these days and if it does the voltage drop is minimal and I mean minimal, what ever charging unit is in your van will be provided, Sorry Lenny and others, it's too old school, and on top of this, if you were going to fit a B2B it would be pointless in changing it anyway.
Sorry Paul can't agree my neighbour has a newish Autosleeper the wiring in it is pathetic about 4mm sq for the main hab battery wiring compaired to Hymer's 16mm sq.
 

haganap

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Sorry Paul can't agree my neighbour has a newish Autosleeper the wiring in it is pathetic about 4mm sq for the main hab battery wiring compaired to Hymer's 16mm sq.
not saying it isn't but it will depend on the run and modern system's even with crap wiring will still perform.
 

Lenny HB

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not saying it isn't but it will depend on the run and modern system's even with crap wiring will still perform.
Not if you had seen this Autosleeper the wiring is a joke, well undersized cable taking torchous roots 3 times as long as they need to be, typical British wiring.

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Last edited:
Jun 4, 2016
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I have 3 batteries, 300w solar, a victron battery monitor, a 60amp sterling b2b charger and never use ehu.
I would advise in order to sort out.
1. get a 2nd battery
2. get a battery monitor
3. then get a b2b if needed
 

two

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Everyone's needs are different. I say fit a battery monitor first. This will indicate actual usage and recovery rates, and provide a better understanding of an individual's circumstances/requirements. An extra battery may not be needed if consumption can be controlled better and a battery monitor will assist with that.
 

Lenny HB

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Oct 18, 2007
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Everyone's needs are different. I say fit a battery monitor first. This will indicate actual usage and recovery rates, and provide a better understanding of an individual's circumstances/requirements. An extra battery may not be needed if consumption can be controlled better and a battery monitor will assist with that.
After fitting a battery monitor I was surprised to find I was using 32a/h a day before my estimate was around 20a/h.

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