B2B

nabsim

Full Member
I know Del has posted asking about makes but my question is a bit different so thought it best to start a new thread.

I think I know what a B2B is supposed to do but not certain I know all the pros and cons so can you explain please? Also is the fitting explained on the instructions the ‘best’ way to fit?

Also my Sprinter could have a 90ah, 120ah or 200ah alternator, that is if it is original. What should I expect from each of those?
 

grath

Full Member
Check out the simple Battery Master from Van Bitz
Had one on a couple vans and they work very very well!
I even have a new one on my present van, (used for one day) but since having the Schaudt Solar regulator I don't use it
Highly recommended!

battery-master
 

yorkslass

Moderator
Check out the simple Battery Master from Van Bitz
Had one on a couple vans and they work very very well!
I even have a new one on my present van, (used for one day) but since having the Schaudt Solar regulator I don't use it
Highly recommended!

battery-master
Does a battery master and Schaudt charge the leisure batteries while travelling?
If they do, how do they work, are they the same as a B to B?
 

grath

Full Member
The ScahdtI am talking about, is the solar regulator that splits the charge between the leisure battery and the engine battery.
Hymers have a Scaudt EB***** (different ones) that operate all of the charging while on hook up or driving and charge both batteries.
The Battery Master is a device that when the engine battery drops a little below the leisure battery, it switches the charge from the leisure battery to the engine battery. So you don't get a flat engine battery.
 

wildebus

Full Member
I don't think the Battery Master is the same thing as the B2B charger Neil is asking about?

My understanding is the Battery Master is a device that provide a trickle charge that is designed to provide a maintenance charge to the starter battery when the van is getting a charge from mains hookup or solar.

a B2B - Battery to Battery - Charger is a device that gets activated when the engine runs (so powered from Alternator) and charges the Leisure Battery Bank.
The main benefit over a basic Relay Charger (either VSR or D+ Switched Relay) is that they are a 'smart' charger, same as a good mains charger or good solar charger and will provide a proper charging algorithm in terms of voltage and current.
A basic Relay just straps the two (starter and leisure) batteries together and will never fully or optimally charge a battery.
That is the key Pro. The Con is they are a lot more expensive than a Relay.

How it comparts to the Factory Split-charging system you have right now, Neil, I don't know (but I suspect a modern B2B will be better, just like a modern mains smart charger is better than the typical standard fit factory motorhome mains charger)


Fitting can vary depending on the model of B2B. The one I added to my van just needed supply from Starter and Leisure Batteries, just the same as a VSR. (In fact, I wired it up in parallel with the VSR so I can choose between VSR or B2B with a toggle switch to evaluate and compare the two)
 

nabsim

Full Member
I have been doing some reading but getting farther away rather than it becoming clearer. My solar controller supplies a fixed 1amp charge to the starter battery when the panels are harvesting with the bulk going to the hab batteries. What I have just been reading says this can result in discharging/killing the starter battery as the B2B will see the charge coming in and wrongly assume the 3ngine is running. It says about using the D+ but that’s when my eyes started clouding over.

I run fully sealed, no maintenance lead acid batteries so it doesn’t look like I really want to bang lots of amps very quickly into them, or am I reading this wrong? Looks like there is va lot more to B2B’s than my limited knowledge can comprehend at the moment.
 

Minisorella

Moderator
I've been trying to get this electrickery clear in my head for months now Nabs but I'm no closer either. At the moment, I've got the battery master like Grath... had it installed along with the solar panel and the solar controller 7 years ago. It does what Grath said... determines if the starter battery has fallen 0.5V below the LB and switches the flow to the front, be that from mains power or from the solar. If I upgrade the solar panel, I know I'll need a new controller for the extra juice but can't determine if the battery master will still do the job of looking after the starter battery or if I'll need a B2B or if an MPPT does both jobs or what the heck a ring thingy is or a split charge relay... my head's spinning with stuff I just don't understand :cry:
 

wildebus

Full Member
I have been doing some reading but getting farther away rather than it becoming clearer. My solar controller supplies a fixed 1amp charge to the starter battery when the panels are harvesting with the bulk going to the hab batteries. What I have just been reading says this can result in discharging/killing the starter battery as the B2B will see the charge coming in and wrongly assume the 3ngine is running. It says about using the D+ but that’s when my eyes started clouding over.

I run fully sealed, no maintenance lead acid batteries so it doesn’t look like I really want to bang lots of amps very quickly into them, or am I reading this wrong? Looks like there is va lot more to B2B’s than my limited knowledge can comprehend at the moment.
Ok. I see where you are coming from. A voltage sensing B2B will switch on when the starter battery is above a certain voltage (that voltage will only appear when the battery is being charged by something - be it mains, alternator or solar). This can have the effect of using the starter battery to drive the B2B charger. I posted about this actually on an update to my "show us your motorhome" thread here - https://www.wildcamping.co.uk/forums/show-us-your-van-motorhome/65892-clarence-safari-camperbus-9.html#post972793

For your installation you would have to have a mega-sized B2B charger to worry about too high an amperage going in so that aspect is not one to worry about I would say.

The D+ is a control signal generated by the alternator that says when it is running. It is this that drives the battery symbol on the dashboard for example. It can also be used to control devices such as chargers, fridges, etc.
 

nabsim

Full Member
So better to have a B2B switched through the D+ signal then Dave?

@Jennie your Battery Master will continue to top up the starter battery ok so you can ignore that one. If you are increasing you solar then you may need a new controller as well, mppt gives more yield than pws so it’s worth paying the extra. All you should need (I think) is to match panels to controller and make sure cables from panels to controller to battery bank are big enough. I know not everyone agrees but I fitted fuses after cables enter habitation area so I can isolate panels if I want to do anything at battery or controller end, easier than covering the panels for me :)

My controller is for dual battery banks and has the facility to trickle charge the starter battery so I do not need a battery master. I am looking at options for getting more power to my leisure batteries when off grid for longer periods. I do have space for more solar but I would also have to swap my controller so it’s an option I don’t want to take just yet.
 

Minisorella

Moderator
Thanks Nabs... that's set my mind at rest about the battery master. I'm certain I'll need to replace the 7-year-old solar controller, as I'd be going from 130W solar to 245W and have already upped the leisure batteries from a single 110 to 2 x 130s. Plus a better controller would likely future-proof things a bit. I don't know about the cables at all but I guess that's something that can be checked when the time comes. Hmmm... I think the company that installed it all are still thriving, so I might give them a call and get some details about what I've already got. Meanwhile, I'll keep reading threads about electrics in the hope that I'll see the light one day - pardon the pun :giggle:
 

wildebus

Full Member
As an example, my B2B is voltage sensing BUT also needs a specific wire to be at 12V. I have that tied to 12V permanently because that suits how I want to use it in my van, but that same wire I could link to the D+ instead so it can only be potentially active with the engine running OR I could link it to the ignition (much more common for auto-sensing B2Bs) as it cannot be active without the ignition on.

So in your setup, I'd probably suggest linking the B2B control line to an ignition line and you will never have it active with the starter battery on charge as you wouldn't leave the ignition on. If you wanted to use a D+ signal, you have one under the driver's seat anyway.

Ref solar, there is nothing to stop you having multiple controllers if you wanted more solar but like your existing controller
 

Bigbarry

Full Member
I have been doing some reading but getting farther away rather than it becoming clearer. My solar controller supplies a fixed 1amp charge to the starter battery when the panels are harvesting with the bulk going to the hab batteries. What I have just been reading says this can result in discharging/killing the starter battery as the B2B will see the charge coming in and wrongly assume the 3ngine is running. It says about using the D+ but that’s when my eyes started clouding over.

I run fully sealed, no maintenance lead acid batteries so it doesn’t look like I really want to bang lots of amps very quickly into them, or am I reading this wrong? Looks like there is va lot more to B2B’s than my limited knowledge can comprehend at the moment.
I am with you on that Nabsim
 

Edina

Moderator
Neil, I don't want to confuse you further but if it will help I'll explain what I have now got fitted.

The Ring RSCDC30 battery to battery controller has 6 connections - pos & neg from engine battery, pos & neg from leisure battery and pos & neg from solar panels (not obligatory). There is also a temp sensor lead that connects directly to the LB terminal; that's it, nothing complicated. The leads need fusing of course and it wants to be in a ventilated location.

I connected my solar panels to the unit and did away with the separate solar controller, so there was no conflict between the two power sources.

I also have a Sterling battery maintainer which trickle charges the eng batt (max 3 amps) when the LBs reach 13.3v and cuts off when they drop to 12.9v. Link - battery maintainer. There are other makes that do the same thing.
 

nabsim

Full Member
Ref solar, there is nothing to stop you having multiple controllers if you wanted more solar but like your existing controller
Not sure how you meant this bit Dave so querying it as when I added my second panel I added a second controller, I did it for a specific purpose which turned out to be invalid though. At one meet speaking to Phil and Colin they said the controllers would be fighting each other (can’t remember their words for it) and I wouldn’t be getting full panel output.

I will admit I didn’t really believe what they told me but was easy to check as controllers were side by side. I can’t remember exact numbers now but I did post on WC at the time, my votronic computer went from showing 7 amps harvested to over 11 amps. I removed the second controller and have it in spares bin.
 

nabsim

Full Member
Thanks Chris, that is crystal clear for me, Would I be right in thinking if solar did not go through the Ring unit that could fool your installation into thinking the alternator was charging the starter battery?

I can see how linking to ignition should solve that but you don’t mention it, you don’t have separate solar input though.
 

Edina

Moderator
That was the reason I fed the solar into the Ring unit, so there was only one controller for both power sources. The more you read about this subject the more conflicting 'statements' you get, so I chose the simple way and it works very well. A few years back I might have enjoyed running cables everywhere and testing the voltages to 3 decimal points, but now I just want things straightforward and easy to install ;)
 

nabsim

Full Member
I am the same Chris, nice and easy works for me but I have 300w of solar on the roof with space for at least one more panel. The Ring unit you mentioned would work now but not allow another panel so I need to look what others are available I think, or different ways of implementing it.

Having everything going through one unit was my original intention but I tried with my EBL and that couldn’t do what I wanted. It’s a bit of a bugger as I have what I initially wanted as I didn’t intend staying in one place more than a couple of days, these extended meets/stops in bad (winter) conditions are my problem it seems. We did manage 5 days at Moffat but we got a fair bit of sun, two more days with only an hour running time on the engine and we had to book a site to charge up. Cost is a factor now as I have already spent on the solar and fully retired in two months so need to get it right this time.
 

wildebus

Full Member
Not sure how you meant this bit Dave so querying it as when I added my second panel I added a second controller, I did it for a specific purpose which turned out to be invalid though. At one meet speaking to Phil and Colin they said the controllers would be fighting each other (can’t remember their words for it) and I wouldn’t be getting full panel output.

I will admit I didn’t really believe what they told me but was easy to check as controllers were side by side. I can’t remember exact numbers now but I did post on WC at the time, my votronic computer went from showing 7 amps harvested to over 11 amps. I removed the second controller and have it in spares bin.
I see no reason why you cannot do this. And it is a common thing to do in large arrays. Would be interesting to hear more on why it is not valid.
I don't understand the 2nd paragraph and how it fits into the picture?
Anyways, I don't think I am adding much to the discussion generally on the B2B so I'll just leave it at this .
 

grath

Full Member
I fitted the Schaudt LMR 1218 (note not cheaper the LR 1218) as I show below. I know it is bl*8dy expensive and there are cheaper and possibly as good or even better regulators. I took the easy way out as it simply plugs straight into the Scaudt Blue box (EB****) control units which Hymer always fit.
I did NOT pay the price shown. It works very well!
See below
index.php
 

Trotter

Full Member
it wants to be in a ventilated location.
Hi jacking, sorry. Would every B2B unit need to be in a ventilated location ? I was hoping to shove it in the locker with the batteries with all the other electrickery gubbin's. Out of sight,out of mind.
 

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