# Fitting a battery to battery charger



## RichardD (Sep 14, 2009)

Has anyone done this?

I can see that the wiring on the Sterling website is pretty straightforward. My leisure battery is fairly close to the vehicle battery so not a problem, but my query is what happens to the existing charge cable from the alternator/vehicle battery to the CBE DS300 distribution panel.

Does that need disconnecting or can it just be left in place?

If I disconnect then the power to the fridge will be lost whilst travelling.

Any advice appreciated.

Richard

PS, this is the start of the move to lithium power.


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## Pudsey_Bear (Sep 25, 2008)

Not 100% sure, but I would think any cabling should remain as is, if you are only changing type of battery, why would you change/remove a cable.


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## raynipper (Aug 4, 2008)

Yep Kev.
Richard are you just trying to charge an extra battery or both chassis and leisure ones?

Ray.


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## trek (May 1, 2005)

Could be a can of worms Or a simple straight forward job I suppose it all depends on the current power distribution in your camper

If this was a new self build then easy But i guess this Sterling battery to battery charger is for your Carthago so as you mention how will it interact with existing system

And you want to boost / improve the charging of your leisure battery bank via the engine battery ?


Why do you want to fit this charger are you finding your existing setup insufficient ?

I suspect your plan is to charge your leisure batteries faster when the engine is running than you currently can

Presumably you are not a regular user of hook ups , do you have solar panels ?



From sterlings website :-
Battery to Battery Chargers
How does it work- 
The unit monitors the engine start battery, the unit will not start until the battery voltage exceeds 13 volts, then it waits for 2.5 minutes to ensure that some charger is replaced after engine start, it then pulls the engine battery down to no less than 13 volts, this enables the engine battery to still receive a charge and ensures the alternator works at its full potential to further ensure the engine battery is OK


See details
Sterling Power IP21 Pro Batt Ultra 12v - 30a Pro Battery to Battery Charger PN: BB1230
Sterling's range of Battery to Battery Chargers (B2Bs) has grown significantly over the past few years. The B2Bs have become extremely popular as they fast charge batteries as you cruise along without the need for complex wiring, touching your alternator, voiding the alternator's warranty and tampering with the electronic control units (ECUs) Sterling Power Pro Batt Ultra This Battery to Battery Charger is Regenerative Braking / Smart Alternator Friendly - ideal for Euro 5 / 6 + engines

See details
Sterling Power Wildside Caravan Battery to Battery Charger PN: BBC1225
The electrical requirements onboard caravans have increased in the modern world (laptops/tablets/phones/microwaves/hairdryers / Caravan movers etc.). When at campsites this is no problem thanks to AC hookup. However, if touring is your forte and don't wish the extra cost and limitations at campsites, or simply unable to operate your fridge and charge you caravan/mover battery due to the new euro 6 engines then this is the product for you.


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## trek (May 1, 2005)

http://forums.outandaboutlive.co.uk.../Sterling-battery-to-battery-chargers-/15889/

If the reason for fitting this is to charge a new set of lithium batteries and this B2B charger has a setting for them but your existing charger doesnt then Yes you would have to prevent the exisiting charger from working

Still in my mind a can of worms and why bother ?


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## trek (May 1, 2005)

Maybe ask Mojo ?

https://motorhomer.com/forum/motorh...t/15020-finished-lithium-battery-installation


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## RichardD (Sep 14, 2009)

My main goal is weight saving as I've had to downsize to 3500kgs.

I've currently got a 80Ah gel leisure battery as fitted by Carthago. I can get a 50Ah lithium which will have about 20% more capacity than the 80Ah gel and it only weighs 6.7kgs. Total weight saving will be approx 20kgs.

The battery supplier has confirmed that the existing mains charger is OK for lithium but recommends a battery to battery charger to get a full charge.

Having given it more thought I don't believe there will be a problem, however, I have posed to question to Sterling and Road Pro.

We are not major wild campers but can spend 5 or 6 days on Aires. A B2B will almost completely recharge the 50Ah lithium in about 1.5 hours of driving from being flat. Our previous van had an Efoy as back-up in this circumstances.

Richard


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## WildThingsKev (Dec 29, 2009)

RichardD said:


> Has anyone done this?
> 
> I can see that the wiring on the Sterling website is pretty straightforward. My leisure battery is fairly close to the vehicle battery so not a problem, but my query is what happens to the existing charge cable from the alternator/vehicle battery to the CBE DS300 distribution panel.
> 
> ...


When I fitted a Votronic b2b to my Rapido (which also has a CBE system) I fitted a relay between the batteries and the CBE box which isolates them once the b2b starts.

So, in operation the leisure batteries are only connected to the b2b charger; the fridge, truma dump valve and all internal power works as normal. The cbe display will show only vehicle battery voltage on both vb and leisure battery settings and the amps shown will be about zero, I fitted a separate nasa battery monitor to show b2b charging current which is also much more accurate the rest of the time.


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## nicholsong (May 26, 2009)

trek said:


> http://forums.outandaboutlive.co.uk.../Sterling-battery-to-battery-chargers-/15889/
> 
> If the reason for fitting this is to charge a new set of lithium batteries and this B2B charger has a setting for them but your existing charger doesnt then Yes you would have to prevent the exisiting charger from working
> 
> Still in my mind a can of worms and why bother ?


Maybe you do not understand the purpose of the Sterling BtoB charger.

It is to overcome the limited charge that that the alternator gives to the leisure batteries. The alternator output is normally controlled by a voltage regulator set at 14(?)volts, so when the engine battery reaches that(about 7 mins after a start) the charging rate is reduced to very little, so there is not much going into the leisure batteries.

The Sterling product('Battery-to-Battery' is a misnoma as the alternator feeds both batteries directly) controls the alternator output according to the charge required to top-up both engine and leisure batteries, so continues to give a high rate of charge till both are full.

In our case after 2-3 days off-grid it will fill our leisure batteries with 30 mins of engine running. If I remember we fitted a 80amp Sterling BtoB.

Geroff


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## trek (May 1, 2005)

I understand the principle but having had 8 campers / motorhomes over a period of some 35 years unless i was building from scratch or the existing CBE / Sargent/ electoblok whatever you have fitted packed in i just still wouldnt see the need 

(And my wife can testify that i do like my gadgets ) 

I have never had a problem charging with the existing factory fitted setups especially with a solar panel on the roof 

I agree with wildthingskev’s idea of a relay that it would be wise to isolate when the B2B is charging


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## Pudsey_Bear (Sep 25, 2008)

We only wild camp, and all year round, and never seen a need for extra gizmos, with 100w solar and usually 250ah of LB never had a problem despite using heater and TV etc, the weight issue is a different problem, I assume there are medical reasons why you have lost entitlement Richard, I hope I keep mine when the time comes in 30 months.


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## RichardD (Sep 14, 2009)

Hi Kev, yes it's a real bummer having to go down to 3500kgs. The DVLA entitlement categories are a joke!!

I've lost my C1 but kept the BE which means I can tow up to a 3500kg trailer and up to a 3500kg vehicle depending on the vehicle specification. On the B category I can drive a 3500kg vehicle plus a 750kg trailer.

Yet I can only drive a 3500kg van on it's own! Doesn't make sense to me.

Surely it would be better to say a max train weight of 4250kgs and then you can please yourself how this is made up.

Sorry rant over,getting off the subject.

Richard


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## Pudsey_Bear (Sep 25, 2008)

Not a rant Richard, it's important to others to know what can happen, understanding that and perhaps why might help someone else.

Maybe worth mentioning in a more appropriate thread so it's not hidden in a different topic.


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## nicholsong (May 26, 2009)

RichardD said:


> Hi Kev, yes it's a real bummer having to go down to 3500kgs. *The DVLA entitlement categories are a joke*!!
> 
> I've lost my C1 but kept the BE which means I can tow up to a 3500kg trailer and up to a 3500kg vehicle depending on the vehicle specification. On the B category I can drive a 3500kg vehicle plus a 750kg trailer.
> 
> ...


Richard I agree with all your post.

Unfortunately the categories are in the 'Vienna Convention' 1936(?) signed up to by the British Government, together with 127(?) other countries. This would be very difficult to re-negotiate.

Of course the UK government could waive the rule within UK, but could not restrict a licence only to UK use.

Geoff


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## trek (May 1, 2005)

https://www.motorhomefun.co.uk/forum/threads/sterling-power-pro-batt-ultra-60a-b2b-on-ebay.165752/

Some electtroblok connection tips on this recent thread


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## RichardD (Sep 14, 2009)

Having done some more reading including the links from your responses it looks pretty straightforward.

The RoadPro data about their lithium batteries have wiring details.

https://www.roadpro.co.uk/userfiles/PDFs/product information/NDS/3Lion-3Link manual V1.1.pdf

The other interesting product is the range of chargers from CTEK which can take a solar input and has built-in MPPT regulator.

https://www.roadpro.co.uk/product/0.../ctek-d250sa-dual-dc-dc-charger-c8664a/C8664A

Richard


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## RichardD (Sep 14, 2009)

Spoke to Sterling and he agreed that the current CBE arrangement needs to remain as it needs the power from the alternator for the fridge and you need the connection back to the leisure from the CBE for the mains charge.

Does anyone know of an expert on the workings of the CBE distribution box just to double check?

WildThingsKev, where did the relay actually fit? Was it the feed back from the CBE to the leisure battery?

Richard


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## trek (May 1, 2005)

Is it really worth all this bother especially if your not 100% sure 

Like I said originally it can be a can of worms and once you start to buy the gear and start to fit it all it could give rise to issues down the line that you hadnt even thought of at the outset

If it aintbroke why fix it - the more complicated it is the more potential for problems


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## RichardD (Sep 14, 2009)

The 20kg weight saving is worth the effort.

Richard


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## coppo (May 27, 2009)

Richard, have a look at aandncaravan services website as Alan talks loads about charging, batteries etc, he has thoughts too on the new batteries you are considering.

Worth a read before you commit.

He sells B2B's I think that are compatible with some systems.


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## nicholsong (May 26, 2009)

For what it s worth we fitted a B2B but kept it independent of our charger which is an electroblok. It is just wired from the alternator to the leisure batteries with sensor on both engine and leisure batteries.

Works fine.

I think complications arise when one rties to integrate systems which may be incompatible. Sterling advised they had not found a way to do it with their B2B and our Elecktroblok, because the design geometry is different.

Geoff


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## coppo (May 27, 2009)

nicholsong said:


> For what it s worth we fitted a B2B but kept it independent of our charger which is an electroblok. It is just wired from the alternator to the leisure batteries with sensor on both engine and leisure batteries.
> 
> Works fine.
> 
> ...


Do you have a separate battery monitor Geoff, to tell you what's happening/state of charge etc?


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## nicholsong (May 26, 2009)

coppo said:


> Do you have a separate battery monitor Geoff, to tell you what's happening/state of charge etc?


No Paul but I can see during charging from the B2B that the voltage is way up and that after engine shutdown, and a rest period, what the resultant voltage is, which is all I had to monitor the state of the batteries before fitting the B2B. Afier half an hour or so driving the voltage is usually very healthy.

I then just monitor the battery voltage at least once a day when parked.

Geoff


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## coppo (May 27, 2009)

nicholsong said:


> No Paul but I can see during charging from the B2B that the voltage is way up and that after engine shutdown, and a rest period, what the resultant voltage is, which is all I had to monitor the state of the batteries before fitting the B2B. Afier half an hour or so driving the voltage is usually very healthy.
> 
> I then just monitor the battery voltage at least once a day when parked.
> 
> Geoff


Cheers, what type batteries are you usuing?


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## nicholsong (May 26, 2009)

coppo said:


> Cheers, what type batteries are you usuing?


Vented Lead Acid.


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## WildThingsKev (Dec 29, 2009)

The relay is fitted in the +ve cable from the main board to the batteries and switched by the D+ output (which I took from the cbe unit - it's shown in the manual).

I was concerned that the truma dump valve might open in the few milliseconds of changeover but it never has.

Kev
Sitting in the van at 1570m in Grimentz with loads of snow and fully charged batteries - life is good!


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## RichardD (Sep 14, 2009)

WildThingsKev said:


> The relay is fitted in the +ve cable from the main board to the batteries and switched by the D+ output (which I took from the cbe unit - it's shown in the manual).


So the power feed to the distribution board from the alternator/vehicle battery was left in place?

And the power feed from the distribution board back to the leisure battery had the relay fitted to it?

What type of relay did you use? I can only find a changeover with push on terminals.

Richard


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## WildThingsKev (Dec 29, 2009)

Yes
Yes
Will look tomorrow


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## RichardD (Sep 14, 2009)

@WildThingsKev did you find the details of the relay that was used on your system?

Richard


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## WildThingsKev (Dec 29, 2009)

No, sorry but I forgot. We are away skiing in the van at present but I have to find a screwdriver to undo the box it is fitted inside of (awkward location).


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## RichardD (Sep 14, 2009)

OK Kev, not to worry at the moment, but if you can look when you get home that would be great.

Richard


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## WildThingsKev (Dec 29, 2009)

Hi Richard

Sorry for the delay but the relay I used to isolate the batteries from the habitation side whilst the b2b is in operation was a Durite 12v mini heavy duty change-over relay 072870 which I bought for about a tenner from SED Ltd.


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## nicholsong (May 26, 2009)

Excuse me all but, although I have gone back through this thread, I do not understand the reason for this isolation.

I have a Sterling B2B which is wired directly to the vehicle and leisure batteries. It does not, on advice, operate through the Elektroblok.

Is there something I need to know about isolation?

Geoff


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## RichardD (Sep 14, 2009)

I have now spoken to a couple of dealers who sell CBE products but unfortunately they have no ability to give technical advice.

I did speak to Southbourne and Marcle and they both advised to disconnect the main alternator feed to the CBE DS300 distribution box.

The supply for the fridge etc whilst on the move would be supplied via the habitation battery which would be charged from the B2B charger attached between the cab battery and the hab battery.

I assume that the ignition feed +D would provide the trigger for the relay within the DS300 to connect the hab battery to the fridge. I believe that the electronics within the DS300 only triggers this relay when it sees more than 13.2 volts.

To be honest I'm still trying to think this one through and probably will have to do some experimenting.

Richard


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