# Battery to Battery Chargers



## Midnightrambler

I am thinking about installing a Battery to Battery Charger to my Rapido.
Have any of you guys fitted one, if so your comments would be appreciated. 
Do they really charge the leisure battery much quicker?
Thanks
Alan


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## whistlinggypsy

> I am thinking about installing a Battery to Battery Charger to my Rapido.


Had one fitted to my previous m/h a Rapido 985F, Sterling B2B the best bit of kit I ever installed.

Bob


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## gnscloz

hi can concur whistlinggypsy best thing fitted to van inc dome.


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## JockandRita

whistlinggypsy said:


> Had one fitted to my previous m/h a Rapido 985F, Sterling B2B the best bit of kit I ever installed.
> 
> Bob


Aye, and guess what unfortunate sod dipped out when Bob was flogging his off.............only because I wasn't fully aware of what it was capable of. 

Now I am seriously considering one too. :wink:

Regards,

Jock.


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## whistlinggypsy

> Aye, and guess what unfortunate sod dipped out when Bob was flogging his off.


Sorry Jock, I wish I could have one on my Autocruise but this ruddy Nord system wont allow it.

Bob


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## PeterandLinda

Hi

We had a Sterling charger fitted by VanBitz and it really does knock spots off the Hymers inbuilt capacity to recharge the leisure batteries. We often stay on Aires and wild camp without Power and provided we move on every couple of days or so the batteries are fine with a couple of hours driving.

P&L


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## CliveMott

"but this ruddy Nord system wont allow it"

Oh yes you can!

C.


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## Roger7webster

I have just fitted (yesterday) a Sterling B to B charger to my 2003 962m Rapido. 
Sited the unit in the garage for convenience. Easy diy job using 35mmsq cable 
Unit works as described on the box but there is a possible problem with the Rapido electrical system when used in conjuction with the B to B 
In my case the unit continued to operate when on hook up and the onboard battery charge was in use ie fan runs continuosly 
Checked with Sterling tech support who recognise the problem with the Rapido battery charging control system and suggested fitting a 100 amp battery isolating switch in the supply cable. 
This has now been fitted and the system is operating ok 
Hope this helps 
Roger


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## Midnightrambler

Thanks for all the replies guys, looks like thats my Christmas present sorted!!
Just to clarify please Roger. Regarding the Battery Isolator Switch, not being technically minded, do you have to switch the
Isolator off manually when you are on hook up?
Thanks again
Alan


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## Roger7webster

Yes the isolator is manualy operated. I did consider fitting a remote relay switch but the manual arrangement is simple to operate and cheap to fit.


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## CaptainBligh

Midnightrambler said:


> I am thinking about installing a Battery to Battery Charger to my Rapido.
> Have any of you guys fitted one, if so your comments would be appreciated.
> Do they really charge the leisure battery much quicker?
> Thanks
> Alan


I had one fitted by Solar Solutions with a Nasa Clipper Battery Monitor- it charges up to 38 amps when batteries are low. I have since had the temperature sensor disconnected from the alternator as Vanbitz advised that it often can show a false overheat warning light.

I hope this is helpful.

Captain Bligh :brave:


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## eddievanbitz

CliveMott said:


> "but this ruddy Nord system wont allow it"
> 
> Oh yes you can!
> 
> C.


You took the words right out of my mouth!

Eddie :wink:


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## whistlinggypsy

> CliveMott wrote: ‹
> "but this ruddy Nord system wont allow it"
> 
> Oh yes you can!
> 
> C.
> 
> You took the words right out of my mouth!
> 
> Eddie


Well guy's I have asked on several occasions if its possible and each time I have been told "no" you cannot with the Canbus/Nord system, so come on chaps give us a clue :?

I will be most upset as I sold my Sterling B2B at a give away price now I am regretting it. 

Bob


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## jontan

Midnightrambler said:


> I am thinking about installing a Battery to Battery Charger to my Rapido.
> Have any of you guys fitted one, if so your comments would be appreciated.
> Do they really charge the leisure battery much quicker?
> Thanks
> Alan


I also am about to purchase and fit one....just have one question

As i have moved my leisure battery from under the drivers seat would this be a good place to fit the b2b charger.


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## gnscloz

jontan said:


> Midnightrambler said:
> 
> 
> 
> I am thinking about installing a Battery to Battery Charger to my Rapido.
> Have any of you guys fitted one, if so your comments would be appreciated.
> Do they really charge the leisure battery much quicker?
> Thanks
> Alan
> 
> 
> 
> I also am about to purchase and fit one....just have one question
> 
> As i have moved my leisure battery from under the drivers seat would this be a good place to fit the b2b charger.
Click to expand...

ideally locate it as close as poss to the leisure batteries 
the charger will need to get air circulation


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## Midnightrambler

Thanks again guys, some very useful replies.
Alan


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## NicknClair

"Well guy's I have asked on several occasions if its possible and each time I have been told "no" you cannot with the Canbus/Nord system, so come on chaps give us a clue Confused"

As the connection is a direct "Battery to Battery", the Nord system cannot be effected!! This is the beauty about the B2B charger as due to the way it is connected, the B2B cannot effect any other electrical system of void any warranty.
The minor downside to it is more applicable to Motorhomer's that have an electroblok battery monitoring system, which it cannot measure the power going into the leisure batteries from the B2B, hence why it would be recommended to fit something like the NASA display.
Had this set-up on the previous van and going back to VanBitz for them to fit again, along with a Combi S 1500W and a 220AH Elecsol Battery.


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## greygit

Hi
Could someone tell me the avantages of fitting this charger as we don't seem to have any problems with the one already fitted to our Rapido?
Gary


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## Roger7webster

The advantages are well documented on the Sterling web site.


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## rowley

Gary, may I suggest that if it aint broke don't fix it.
I have never had a problem either.


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## eddievanbitz

The "average" van is built for the "average" person to do "average" things! Use every two or three weekends, unplugging from mains, driving 50 miles to a Caravan Club site, plugging in to mains, using the facilities on site, then driving home Sunday night!

The second you deviate from the "average" you will find that things need considering. The first thing that people find is that at that four day MHF rally their battery goes flat. Some then invest in a solar panel, some in additional batteries, some buy fuel cells and some buy a generator. The rich buy all of them or go for a mix and match.

My advit ice is always the same, try it! It it 'aint broke don't fix it! 

The same principle applies to the Thetford cassette where some vans come with two as standard, but if you always stay on sites it is not a problem, wild camp for a few days and it is!

I carry an additional 125L of water when we go to shows as the huge water tank the Winnie has cannot cope with Lyn's hair washing regime :lol: when going to a site it is not a problem.

So use the van in the "average" way everything works Tickity Boo, start to go of the beaten track you will start to find out that things fill up too quickly or go flat to quickly! That is when it is time to start making changes

Eddie


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## NicknClair

Roger7webster is right, as it saves an awful amount of typing :lol: . 
I made the choice to have mine fitted as the cable and fitment need to be spot on to get the full benefits from a system such as this. 
We had all this done so that our "Wild camping" could be more plus with using the inverter for the kettle, toaster etc, we had reduced the Gas consumption which helps alot when getting Gas is harder when you're abroad. 
The NASA panel was a big help when we wanted to monitor our use, so we could determine when to start the engine before the batteries went flat completely. Details of the Nasa can be found on VanBitz website.


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## CliveMott

The basic split charging system using a simple relay and some stout wiring has been used for many years to charge the leisure battery while driving. The charging regime is the same as that applied to the starter battery and is quick to put a large chunk of the energy back until the battery voltage reaches 14 volts. After this the alternator cuts back the charging current so that this limit is not exceeded. However because the leisure battery is frequently some distance away from the alternator and starter battery the resistance of the wiring to the leisure battery will provide a limiting to the charging current. This is why its important to use MASSIVE wiring between the leisure battery and the alternator B+ terminal via the contacts of a substantial relay and fuse for split charging to work well. Over recent years converters have woke up to the requirement to use fat wires. 
The alternator limiting voltage of 14 is set because above this voltage the battery starts to gas and convert the water content of the electrolyte into hydrogen and oxygen gas. You do need to charge above 14 volts for a short while in order to get the remaining 20% of charge back into the battery. The car industry prefers to ignore the fact that the battery is only 80% charged because it means low (zero) battery maintenance and a long battery life. 
For most of us the split charging system is perfectly adequate and inherently simple. 
The B2B charging systems monitor the starter battery voltage and when it has risen sufficiently to denote that it is being charged by the alternator then via the B2B will charge the leisure battery via some electronics that enable it to charge the leisure battery above 14 volts even when the starter is at 14 volts. So it can charge faster and more completely and can follow charging algorithms more associated with fast multistage wall mounted chargers normally associated with electric vehicles. 

So, two questions 

Are you in a hurry to charge your leisure battery while driving? 
Do you require the added complexity and increased maintenance requirements? 

Simples 
C.


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## greygit

So, two questions

Are you in a hurry to charge your leisure battery while driving? 
Do you require the added complexity and increased maintenance requirements?

Simples 
C.[/quote]

question 1, Never had the need.
Question 2 Definatly not!
Thanks
Gary


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## JockandRita

CliveMott said:


> So, two questions
> Are you in a hurry to charge your leisure battery while driving?
> Do you require the added complexity and increased maintenance requirements?
> 
> Simples
> C.


Hi Clive,

Answer to question No 1....Most definitely, especially when hopping from Aire to Aire/Stellplatz to Stellplatz without any mains hookup.

Answer to question No 2...if you mean more regular topping up of the batteries, then yes, especially if easy access as we have. (100 amps x 3).

There isn't one person that I have communicated with, re the B2B, that has not praised the virtues of it.
I just don't feel confident enough to do a DIY fit, without frizzling the MH, despite Mr Sterling telling me otherwise. :lol:

Regards,

Jock.


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## Jean-Luc

I fitted a B2B to my 2005 Rapido a couple of years age and its a fantastic bit of kit, see my other posts on the subject.
HOWEVER, I had some concerns about its compatibility with the sophisticated system fitted to Rapido's in relation to the possibility of the heigh voltage (14.8v) output by the B2B finding its way back to the base vehicle electrics via the original equipment leisure battery charging system when the engine is running. 
Unfortunately Stirling were not a lot of help on that articular issue so I implemented my own simple solution.
I fitted a 'normally closed' 60 amp relay between the leisure batteries and the original equipment which is activated (opened) when the 12 volt supply to the fridge becomes live. This means that when the connection between the vehicle battery and the charging/fridge is made, the leisure batteries are simultaneously isolated from the habitation side of things and only receive charge from the B2B. All the usual 12 volt stuff normally supplied by the leisure batteries remain powered by the original feed from the vehicle battery.
As regards the B2B operating when on EHU, this is because the origional Rapido equipment monitors the vehicle battery voltage and feeds in a trickle charge at 13.2v when required, this has the effect of raising the vehicle battery voltage such that the B2B will 'wake up' and supply charge to the leisure batteries. but at the safer float charge voltage. It's the circular circuit thing I referred to above but without the height (14.8v) experienced when the B2B is whacking in the heigh current/voltage when recharging depleted batteries when the engine is running after a period of off EHU usage.
Apologies for being a bit long-winded and techy but if you wish PM me and we can talk through the process.


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## Jean-Luc

whistlinggypsy said:


> Aye, and guess what unfortunate sod dipped out when Bob was flogging his off.
> 
> 
> 
> Sorry Jock, I wish I could have one on my Autocruise but this ruddy Nord system wont allow it.
> 
> Bob
Click to expand...

Hi Bob,
See my last post. Why not isolate the leisure batteries when the B2B comes into operation. How would the Nord system react to 'seeing' no leisure batteries connected while the vehicle engine is running !


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## NicknClair

Quote "HOWEVER, I had some concerns about its compatibility with the sophisticated system fitted to Rapido's in relation to the possibility of the heigh voltage (14.8v) output by the B2B finding its way back to the base vehicle electrics via the original equipment leisure battery charging system when the engine is running."

Doesn't a good quality 4 Stage mains charger do this on hook up anyway? Doesn't the Rapido system spill into the engine once the Leisure Battery is charged?
Doesn't a Solar Panel regulate at high volts, but has an engine take-off feed again when the leisure battery is charged (it certainly does on the Alden system, which as I understand is recommended by Rapido)?

I would say that it isn't a problem, as the B2B doesn't spend much time at over 14.5, as this is a primary/secondary stage of the 4-stage program, it then drops back to around 13.5v, but has a very high amperage to maintain a good charge.

I would also say that certainly on my 2004 Fiat, running at 14.5/14.8 has never caused any issues at all. Also on the 2001 Vauxhall Movano and my close friend's Iveco Daily, all of which are ECU controlled systems!!!!!


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## Jean-Luc

spud_gun said:


> Doesn't a good quality 4 Stage mains charger do this on hook up anyway? Doesn't the Rapido system spill into the engine once the Leisure Battery is charged?
> Doesn't a Solar Panel regulate at high volts, but has an engine take-off feed again when the leisure battery is charged (it certainly does on the Alden system, which as I understand is recommended by Rapido)?
> 
> I would say that it isn't a problem, as the B2B doesn't spend much time at over 14.5, as this is a primary/secondary stage of the 4-stage program, it then drops back to around 13.5v, but has a very high amperage to maintain a good charge.
> 
> I would also say that certainly on my 2004 Fiat, running at 14.5/14.8 has never caused any issues at all. Also on the 2001 Vauxhall Movano and my close friend's Iveco Daily, all of which are ECU controlled systems!!!!!


I fully understand the output characteristics of the CBE system fitted to Rapidos and you might very well be right about the other stuff you mention, but not being 100% sure myself and not being able to get quality expert information on the effect of hitting the base vehicle systems with up to 14.8 volts (warranties and all that) I decided to err on the side of caution and invest £3 on the relay. 
I am now 100% sure the connection method I have used keeps the B2B output totally isolated from the Rapido/FIAT original equipment which will keep things simple should issues arrive with eithers electrics.


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## Losos

Midnightrambler said:


> Thanks for all the replies guys, looks like thats my Christmas present sorted!!
> Alan


*Have you have had it fitted yet Alan *:?: I have just been reading up on these BtoB things and must admit the basic idea appeals to me, I am planning the build of my MH right now and was not in favour of the many 'split-charge' thingies they seemed to be approaching the problem from the wrong direction.


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## Losos

CliveMott said:


> So, two questions
> Are you in a hurry to charge your leisure battery while driving?
> Do you require the added complexity and increased maintenance requirements?
> Simples
> C.


Thanks Clive, *a very good summary if I may say so*. As to the two questions

a) Yes, my 'modus operandi' will be *long distances between non EHU stopovers*, so using the alternators 'spare' capacity appeals to me.

b) There will be no 'split charge unit' in my van so no added complexity and the leisure battery will be *easily accessed *so the occassional top up will *not add much to my maintenance regime*.


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## 99469

can you tell me how to fit it to a Rapido 962M in a little more detail. Exactly where does it go and do i need to buy anything else. I have a B2B but wa worried it might interfere with the Rapido charging system.

Also I need to replace the leisure battery - any recommendations


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## Jean-Luc

ghindle said:


> can you tell me how to fit it to a Rapido 962M in a little more detail. Exactly where does it go and do i need to buy anything else. I have a B2B but wa worried it might interfere with the Rapido charging system.
> 
> Also I need to replace the leisure battery - any recommendations


See my earlier posts on this topic. 
I have a Rapido and had concerns, which were not allayed by others contributions on the subject and info from Stirling, about the B2B's interaction with the base vehicle and/or habitation electrical systems.
However, I must say it is a super piece of kit, especially for fast charging the batteries if one is only making short journeys between overnight stops. This is best demonstrated by how my batteries were fully recharged after a four hour drive following 48 hours stop in freezing mid winter conditions where we had the heating on continuously and lights and telly on both nights. The voltage was showing only 12.1v on departure.


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## Roger7webster

I agree with Jean-luc response 
On my 962M I installed the charger unit in the garage on the bulkhead above the heater 
You will need about 12m of cable, 8mm swaged terminals and a 100amp battery isolator (see my earlier post) 
Follow Sterlings instructions re cable size and you will be OK


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## Jean-Luc

Roger7webster said:


> I have just fitted (yesterday) a Sterling B to B charger to my 2003 962m Rapido.
> Sited the unit in the garage for convenience. Easy diy job using 35mmsq cable
> Unit works as described on the box but there is a possible problem with the Rapido electrical system when used in conjuction with the B to B
> In my case the unit continued to operate when on hook up and the onboard battery charge was in use ie fan runs continuosly
> Checked with Sterling tech support who recognise the problem with the Rapido battery charging control system and suggested fitting a 100 amp battery isolating switch in the supply cable.
> This has now been fitted and the system is operating ok
> Hope this helps
> Roger


Roger, mine comes on if the on board charger sends charge to the truck battery to cover discharge from the dash radio and/or the two lights on the underside of the pull down bed which are fed from the Original Equipment courtesy light circuit. The charging voltage brings the B2B to life and it float charges the leisure batteries at 13.8v in a circular circuit, mains-Rapido charger-truck battery-B2B-leisure batteries. This does not seem to be a problem, in fact I think it is good for the leisure batteries.
What I have done however is to isolate the the leisure batteries from the OE when the engine is running, using a relay, this creates a circuit, truck battery-B2B- leisure batteries -earth, as I have concerns about the 14.8 volts hitting the OE when the B2B is in that phase of its charging regime.


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## bodgerco

I like the idea of the B2B and have a simple (??) question.

If I get up and discover the batteries are too low to run the pump etc and I start the engine, how long will I need to run it before i get a meaningful charge to get past the early morning needs such as a shower etc?

In this situation the only alternative is to have a genny which would be noisier and have a lower and less efficient charge regime so the B2b might have a value there as an imergency genny.

OK so neighnours wouldn;t want me running the engine but I could always drive around to collect water, dump waste etc. On the other hand when wild camping no one would be too bothered .

Roy


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## Jean-Luc

bodgerco said:


> I like the idea of the B2B and have a simple (??) question.
> 
> If I get up and discover the batteries are too low to run the pump etc and I start the engine, how long will I need to run it before i get a meaningful charge to get past the early morning needs such as a shower etc?
> 
> In this situation the only alternative is to have a genny which would be noisier and have a lower and less efficient charge regime so the B2b might have a value there as an imergency genny.
> 
> OK so neighnours wouldn;t want me running the engine but I could always drive around to collect water, dump waste etc. On the other hand when wild camping no one would be too bothered .
> 
> Roy


The B2B will chuck in charge at up to 50 amps/hour but there a a few considerations.
I believe to safely handle such a rate of charging at least 200 a/h of batteries is the minimum.
The batteries need to be in good condition.
As the charge in the batteries grows the rate of charge fall off, so there wont be 50 a/h going in after half an hour has elapsed
I wouldn't like to be in the vicinity of a cold dirty diesel running at a fast idle speed for the length of time needed to get a useful amount of charge in.
Finally, unless all you have is a single half knackered battery then your original proposition should not arise after one or to nights in off ehu, if it does then a B2B is not your first port of call, invest in a couple of 110 a/h semi-traction batteries as the first step.


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## bodgerco

Thanks Jean-Luc. 

For the record I have two x 130AH batteries, both of which are in good nick, and 100W solar. The van is based on the latest Sprinter so it is pretty well up to date. 

I agree that this shouldn't happen after one night, but it could happen on the second or third or perhaps fourth morning so the same question arises. 

None the less if I understood correctly I think you answered the question by saying it would take an unreasonably long time to get a decent charge back in. That was my thought too. 

For me, the case for me having B2B is not clear. When we drive from one site to another it tends to be long enough to recharge even with the standard charger so to be able to do it faster with B2B would have limited value. On the other hand I appreciate the charging regime on the Stirling charges the battery to a higher level than the built in Electroblok does so that would be nice. Against that the Electroblok display will not display the true state of the battery so would require additional kit ( NASA?) to do that. The costs ( not being a DIY man) start to escalate. 

Roy


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## DABurleigh

Roy,

Yup, that's a decent summary. If one's motorhoming regime suits what the B2B is for, it is a WONDERFUL piece of kit. If not, you won't achieve much bang for your buck. I do wonder how many understand this before they buy.

For quickly bringing batteries from 60% to 85% (before anyone knocks this, it is more valuable than you might think) it is unbeatable. But if they are as low as 50% anyway (any lower curtails life) then Ohm's Law and decent thick wiring does just as well, and although it CAN put more energy in your batteries than an alternator, the charge rate when it does this is low. 

Dave


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## gnscloz

b2b chargers take the worry away if not on ehu, we have one with 2 110amp wet lead batteries, quite simply if we are stopping on a site 4 or more days we just go out for day in van, on the fourth day, this normally suffices in replenishing the batteries for another 3 or 4 days, 
since having a b2b charger alongside a good inverter we often choose not to have ehu, 
its horses for courses, we isolate the b2b charger via switch, we spent week in france moving to different aires, didnt need to switch it on the vans origional 110 amp coped on its own, 
basically i would,nt be without one, best addition to the van imho

mark


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## Jean-Luc

As Mark says, it's horses for courses. We like to use Aires as much a possible and often do not take EHU if on a site.
The B2B means we arrive with 100% charged batteries (2X70ah Varta 956 002 000 A542 semi-traction) after a few hours driving and can use power without scrimping for up to 48 hours in mid winter and up to a week in the summer. So if we are moving on every few days we have all the power we need.


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## JockandRita

bodgerco said:


> The costs ( not being a DIY man) start to escalate.


And escalating costs are the problem, for the other half of my management team. In her opinion, the costs are not justified, coupled with the theory that "we have managed for years without a B2B, so why do we need one now?" 8O

Hmm, a bit more leverage need there, me thinks. :wink:

Jock.


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## airstream

*Temp sensor*

" I have since had the temperature sensor disconnected from the alternator as Vanbitz advised that it often can show a false overheat warning light."

Hi All,
Can Eddie (vanbitz) give a little more info on the above as Roadpro removed and refunded my B2B as the unit continually locked out on alternator overheat 
Regards Ray


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## Jean-Luc

It's important that the max output of the alternator can handle the extra load, which can be up to 50 amps in the early stages of the B2B charging regime.
AFAIK the basic unit on some Ducato models is only 90 amps while other models are 120amps and 150 is available as an optional extra.
Given that one can easily be pulling over 50 amps with heater, wipers, lights, etc. etc. then a 120 amp output unit would seem to be a minimum requirement to avoid overheating.


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## NicknClair

*Re: Temp sensor*



airstream said:


> " I have since had the temperature sensor disconnected from the alternator as Vanbitz advised that it often can show a false overheat warning light."
> 
> Hi All,
> Can Eddie (vanbitz) give a little more info on the above as Roadpro removed and refunded my B2B as the unit continually locked out on alternator overheat
> Regards Ray


Will I do? 

Cannot see any reason why the guys at RP had removed it due to alternator over-temp. We on average fit between 6 to 10 units per month to "standard" Peugoet's/Fiat's/Citroen's etc. On the advise from Charles and Peter @ Sterling, the temp sensor commonly is removed as they facilitate this for engine rooms in boats, where temperatures are excessive and the marine alternators mainly do not have regulator/rectifier packs bolted on them like the vehicle industry. The official word is that the temp sensor was to satisfy US industry requirements. The charging unit itself "knows" what is available at that given time, therfore will not run a risk of damaging the altenator.
Going back to the quote made above, again I have no reason as to why they removed it, but we have had no underlining issues with the units we have fitted, nor the 2 vans I have had them installed to. Certainly no personal complaints here.


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## Bagshanty

*CTEK B to B Chargers*

Interesting discussion - I've been considering a B to B charger for years, but installation does not seem straight forward, and, as the leisure batteries on my Rapido 746 are right aft, the requirement for huge current capacity makes the ancillary costs also huge.

Looking at the Roadpro catalogue, there is a CTEK B to B charger of lower current capacity (20 amps) requiring only 10 mm sq cable, making it all more manageable and affordable. Although 20 amps is a lot less than Sterling's 50 amps, it is still substantially more than the standard split charge, which peaks at 20 amps, but drops back rapidly to about 10 amps, or less as the battery voltage increases. We do spend a lot of time on aires and wild camping, and especially in autumn battery capacity has been a problem (2 * 90 amp/hour).

Does anyone have any experience of fitting and using the CTEK B to B charger?


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## clipper

Hi Bagshanty I have fitted the Ctec B2B charger easy to fit seems to working ok I only fitted it about 2 months ago so I am still checking it out Have been away for 2nights without h/up & 3nights without h/up and did not run out of power It took a little time to sort the battries out will post a little later on as I am travelling soon in France Spain ect.
Clipper


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