Fitting a B to B Charger (1 Viewer)

Jul 29, 2007
6,526
39,280
Ipswich
Funster No
32
MH
RV and PVC
Exp
30 years
After reading DABurleigh excellent post on fitting a Sterling B-B charger I decided to do the same.
Sterling are still selling the same charger on there clearance line at £169 and with a next day delivery so I very quickly got my grubby hands on it.
Installation is simple just connect positive and negative from the engine battery to the unit and one positive to the hab batteries, the hard part is working out the route and best way to connect to the engine battery.
I decided to run out of the rear passenger seats where the batteries are, under the raised floor where Swift have provided a little cubby hole, into the base of the drivers seat, out the front and under the carpet and into the battery compartment in the front of the passenger seat

Next connecting the batteries, the negative was simple just squeezed a lug on the end of the cable and bolted it to the chassis connection the engine battery uses. The positive had me scratching my head, I needed to fuse as close to the engine battery as possible so started with an inline fuse from Amazon but I didn't like the result. Swift have fitted a fuse holder directly ontop of the battery and after a bit of thought I used that by extending one of the metal strips and mounting another 70amp fuse inline with Swifts.
Fitted split wrap anywhere on the cable that looked vulnerable and clipped it all down.
I am going to have a chat to Sargent to see if its possible to disconnect their charger although it seems to work fine with it connected.

B to B.jpg


The cubby hole very handy for the cables but also for tins of beans etc.
Lookin at the cubby hole.jpg
Negative connection.jpg

Positive connection.jpg
 
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OP
olley
Jul 29, 2007
6,526
39,280
Ipswich
Funster No
32
MH
RV and PVC
Exp
30 years
Where's that?

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May 12, 2019
545
794
Tyneside-Cadiz: All points between!
Funster No
60,781
MH
Autotrail Delaware
Exp
Years Tugging - Newbie MHing
Where's that?
Isn’t there a D+ or perhaps an ignition connection on th B2B?

That is typically used to let the charger know the engine is running.

AFAIK, if not connected to an ignition source one of two issues might occur:

1 when starting the engine, the charger may continue to feed the hab batteries starving the cab battery of cranking power. Similarly if the ignition is on but no engine running.
2 It has been said that without the ignition source the charger may drain the hab batteries in favour of the cab battery (in reverse of what’s wanted).

I’m not an expert just relating some of the points (I think) I’ve learned from those who know better on the forum!
 

andy63

Free Member
Jan 19, 2014
4,672
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I wouldnt worry about it ..
The ignition feed or it could be a engine run signal is only going to be necessary if you have a smart alternator that may not reach the threshold voltage for the b to b switching on ...which could be the case if you are stationary and the engine idling..
..even if you fit it the unit will still operate on the voltage sensing as default..
Andy
 
May 12, 2019
545
794
Tyneside-Cadiz: All points between!
Funster No
60,781
MH
Autotrail Delaware
Exp
Years Tugging - Newbie MHing
I wouldnt worry about it ..
The ignition feed or it could be a engine run signal is only going to be necessary if you have a smart alternator that may not reach the threshold voltage for the b to b switching on ...which could be the case if you are stationary and the engine idling..
..even if you fit it the unit will still operate on the voltage sensing as default..
Andy
I stand corrected. Thanks

Thanks for the write up too Olley

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andy63

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Jan 19, 2014
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since 1990
I am going to have a chat to Sargent to see if its possible to disconnect their charger although it seems to work fine with it connected.
There has been a fair bit debate on that subject..
When I fitted my Stirling bat to bat charger I was not sure that disabling the built in charging facility of in my case the cbe unit was necessary..but eventually went with the solution that was suggested by Pausim ...
I did however fit a switch into the relay coil circut so I could disable or enable that feature..
I have played around with it and leaving the cbe charging loop in certainly doesn't damage anything..in fact in some circumstances the alternator was supplying a better charge than the batteryto battery charger..
The battery to batterycharger is however a proper dedicated charger and in the long run will im sure look after the batteries better..
Andy
 
Mar 23, 2018
412
604
East Devon
Funster No
52,960
MH
PVC
Exp
Since 1995 + 20Yrs a 'Tugger' first.
I have played around with it and leaving the cbe charging loop in certainly doesn't damage anything..in fact in some circumstances the alternator was supplying a better charge than the batteryto battery charger..
The battery to batterycharger is however a proper dedicated charger and in the long run will im sure look after the batteries better..
Andy

I have a CBE charge controler on my 'van and the 'loop' problem you alluded to has concerned me as I too was thinking of fitting a B2B.
So you are suggesting that I could safely ignore this point and not go down the route Pausim mentions?
Trevor
 
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olley
Jul 29, 2007
6,526
39,280
Ipswich
Funster No
32
MH
RV and PVC
Exp
30 years
Mine is fitted with a Sargent EC 651, I can't find a wiring schematic for this anywhere on the web, and Sargent don't list it for sale so I presume its made just for Swift.

I haven't seen pausim's post.

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andy63

Free Member
Jan 19, 2014
4,672
15,017
south shields
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I have a CBE charge controler on my 'van and the 'loop' problem you alluded to has concerned me as I too was thinking of fitting a B2B.
So you are suggesting that I could safely ignore this point and not go down the route Pausim mentions?
Trevor
The truth is I dont know anything for sure ..
I did go down the route of fitting a relay in the hab battery circuit so it would disable when the engine was running and the battery to battery was active..but as I said above..I did fit a switch in the relay coil circuit so that I could try various options..
The outcome of what I've found so far is it is no different to fitting a number of charging sources to the hab batteries...
The higher voltage source takes priority..
Heres a look at the battery to battery in action..the cbe loop is disabled..
20200928_163213.jpg

And confirmation on the monitor
20200928_163155.jpg

I'm on the gel 2 profile and you can see that the charging voltage is 13.8 v..the current at 2.3 amps..

Now I switch out the battery to battery and revert to the cbe charging loop from the alternator..which is at that time generating 14.5v..
You can see the charge current has increased to 3.5amps..
20200928_163249.jpg


I still have retained the relay so that I can disable the cbe loop as the battery to battery charger is still imo the better overall charging source..and I want a lithium profile anyway
 
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olley
Jul 29, 2007
6,526
39,280
Ipswich
Funster No
32
MH
RV and PVC
Exp
30 years
Sorry JockandRita its was DBK not DAB. :doh:

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JockandRita

LIFE MEMBER
Aug 2, 2007
11,402
148,458
Lincs/Cambs border
Funster No
49
MH
N+B Flair 8000i
Exp
Since May 05 (Ex Tuggers).
Sorry JockandRita its was DBK not DAB. :doh:
No problems Olley. I've seen DBK's thread which was very informative, but thanks for the link anyway. (y)

Cheers,

Jock. :)
 
Apr 27, 2016
6,800
7,837
Manchester
Funster No
42,762
MH
A class Hymer
Exp
Since the 80s
The higher voltage source takes priority..
The split charge relay will short out the B2B charger, so that the input and output voltages are the same. AFAIK this does not cause damage to the B2B, just stops it doing anything useful.

A Sterling B2B has three modes. Mode 1 is voltage-sensing, with various upper and lower voltages that determine its operation. This works fine for non-smart alternators. No D+ required.

Mode 2 is like Mode 1, in that it is voltage-sensitive, but also has a D+ connection from the alternator. When the D+ is high (= engine running) the B2B will charge the leisure battery even if the starter battery/alternator voltage is a bit low, as happens with smart alternators.

The latest Sterling B2Bs (with a green stripe) have a Mode 3, which is not voltage-sensitive. It only charges when the D+ is high.

Mode 3 is useful if other things like solar and mains chargers are likely to raise the starter battery voltage and trigger the B2B in other modes.
 
May 7, 2016
7,187
11,609
West Sussex
Funster No
42,951
MH
Carthago Compactline
Exp
Since 2003
I see my name has cropped up in this thread so I thought I would explain why I consider an extra separation relay is needed.

Alternator charges engine battery at (say) 14.3V. Engine battery powers B2B. B2B converts volts to 14.6V and charges the leisure battery. Leisure battery feeds 14.6V back to the engine battery through the original relay and the loop is completed. This loop means the B2B is not only feeding the leisure but the engine battery and it’s own supply. Doesn’t seem right to me. The B2B can’t know when the leisure battery is fully charged because it is also charging the engine battery and powering itself. Confused? Well the B2B certainly is and possibly the vehicle ECU too.

I prefer to separate the circuits.

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andy63

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Jan 19, 2014
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south shields
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Exp
since 1990
The latest Sterling B2Bs (with a green stripe) have a Mode 3, which is not voltage-sensitive. It only charges when the D+ is high.
Thats interesting..maybe there are different software versions of sterling's new green stripe battery to battery..
Mine is a newer green stripe model..but the ignition feed connector as its called..ive chosen to supply it with an engine run 12v supply is still not the default method of switching on.. it still is voltage sensing even if that ignition feed is not active which as you say poses problems with other charging sources switching it on..
I think Stirling say in the instructions that that is intentional so that if the start battery has a solar feed the battery to battery can also be used to supply the leisure battery..
Andy
 
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OP
olley
Jul 29, 2007
6,526
39,280
Ipswich
Funster No
32
MH
RV and PVC
Exp
30 years
After talking to Sargent (who were extremely helpful) this morning they said that several people have fitted a relay but they were of the opinion it only increased charging by about 15% over the inbuilt charger.
They have sent me the full technical print out for the EC600 series power supply/fuse box.
I also want to stop most of the hab services apart from the fridge and heating disconnecting when you start up.
Looking at the drawings and from what they told me when you turn on the ignition a wire from the PS is grounded, when you then start the engine another wire is given a positive feed, so I can disconnect them and see what happens. An alternative is simply to bridge across the terminals at the back of the fuse box to the permanently connected appliances.
 

andy63

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Jan 19, 2014
4,672
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I see my name has cropped up in this thread
Sorry that was me lol..

I prefer to separate the circuits.
And after reading your solution so do I..
I thought I'd made that clear in my post above...but I suspect that there are a lot of battery to battery chargers installed without going down that route and yet no one seems to be claiming they dont work..
So I've just been mucking around a bit to see why.. I suspect that just the heavier wiring that may well have been used installing the battery to battery could be part of the reason..
I also found that when switching from one source to the other ie cbe split charge circut...and battery to battery circuit that the cbe loop produced the higher charging current ..because the alternator voltage was higher than the output voltage of the chosen profile on the battery to battery..
This was all on the lead acid batteries..
I appreciate different chemistries adds to the problems..
Andy

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Apr 27, 2016
6,800
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42,762
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Since the 80s
Thats interesting..maybe there are different software versions of sterling's new green stripe battery to battery..
Mine is a newer green stripe model..but the ignition feed connector as its called..ive chosen to supply it with an engine run 12v supply is still not the default method of switching on.. it still is voltage sensing even if that ignition feed is not active which as you say poses problems with other charging sources switching it on..
I think Stirling say in the instructions that that is intentional so that if the start battery has a solar feed the battery to battery can also be used to supply the leisure battery..
Andy
It may need a firmware update, it needs to be V69 or later. There's a button press/hold combination that shows the software version - in binary code, of course. The user interface is about the worst I've ever seen for a modern device. 69 is 64 + 4 + 1, so it's 1000101 in binary. Google 'binary converter' if it's not that.

To put it into Mode 3, it's a button press/hold for something ridiculous like 40 seconds.
 
Sep 29, 2019
273
486
Funster No
64,845
MH
Forte
Exp
10years
Been following this thread and slow to jump in as I am at the bottom of a steep learning curve but was talking to Sterling this morning as interested in getting the BB1260. I have a Forte which has a EC400. They told me I should disconnect the vehicle battery to the EC400 cable. Does anyone see any issue with that. I have 90W solar and would be fitting a trickle charge for the van battery like a batterymaster at the same time.

Disconnecting the vehicle battery sounds like a simpler solution to fitting a relay etc
 

andy63

Free Member
Jan 19, 2014
4,672
15,017
south shields
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MH
None
Exp
since 1990
It may need a firmware update, it needs to be V69 or later. There's a button press/hold combination that shows the software version - in binary code, of course. The user interface is about the worst I've ever seen for a modern device. 69 is 64 + 4 + 1, so it's 1000101 in binary. Google 'binary converter' if it's not that.

To put it into Mode 3, it's a button press/hold for something ridiculous like 40 seconds.
Cheers.. I just had a look..
Mine comes up with.
001000010
Which Mr Google makes 66 :unsure: :ROFLMAO:
Anyhow cheers but I dont appear to have the 3rd mode function even though it is a newer green stripe model..
Andy

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andy63

Free Member
Jan 19, 2014
4,672
15,017
south shields
Funster No
29,767
MH
None
Exp
since 1990
Been following this thread and slow to jump in as I am at the bottom of a steep learning curve but was talking to Sterling this morning as interested in getting the BB1260. I have a Forte which has a EC400. They told me I should disconnect the vehicle battery to the EC400 cable. Does anyone see any issue with that. I have 90W solar and would be fitting a trickle charge for the van battery like a batterymaster at the same time.

Disconnecting the vehicle battery sounds like a simpler solution to fitting a relay etc
Unless someone has your system you could try what they suggest and see if it is that straight fwd or whether it introduces other problems..
The relay isolation option is not that difficult ..you just need to identify the right circut and find a suitable trigger for the coil..
Hopefully someone can be more helpful..
Andy..
 
Apr 27, 2016
6,800
7,837
Manchester
Funster No
42,762
MH
A class Hymer
Exp
Since the 80s
Cheers.. I just had a look..
Mine comes up with.
001000010
Which Mr Google makes 66 :unsure: :ROFLMAO:
Anyhow cheers but I dont appear to have the 3rd mode function even though it is a newer green stripe model..
Andy
Yes, it's 64 + 2 = 66. I'm not sure how to update the firmware, but the Mode 3 is a software function, no hardware mod needed. It's activated from the menu/button press/hold 'interface'.
 

andy63

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Jan 19, 2014
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Yes, it's 64 + 2 = 66. I'm not sure how to update the firmware, but the Mode 3 is a software function, no hardware mod needed. It's activated from the menu/button press/hold 'interface'.
Yes..ive got that but in my instructions its not an option on any of the button press combinations..ill check again ..
Andy
20201002_160149.jpg

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May 7, 2016
7,187
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West Sussex
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42,951
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Carthago Compactline
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Since 2003
Disconnecting the vehicle battery sounds like a simpler solution to fitting a relay etc
It would be a lot easier. I decided against this because I would lose the mains trickle charge when on ehu and engine battery voltage on the panel. However a battery maintainer would solve the important issue.
 

andy63

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Jan 19, 2014
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south shields
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Disconnecting the vehicle battery sounds like a simpler solution to fitting a relay etc
Hi.. Insider after reading your post I had a look at my system...which I've been exploring on and off for a few months now..
I had obviously missed the possibility of such a simple solution that you had suggested..
Gave it a try this morning..a few min work to remove one wire.. works perfectly and can't see any drawback on my particular system..
Cheers..
Andy..

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Sep 29, 2019
273
486
Funster No
64,845
MH
Forte
Exp
10years
Hi.. Insider after reading your post I had a look at my system...which I've been exploring on and off for a few months now..
I had obviously missed the possibility of such a simple solution that you had suggested..
Gave it a try this morning..a few min work to remove one wire.. works perfectly and can't see any drawback on my particular system..
Cheers..
Andy..
Sounds like that's a win for you and a potentially a win for me. I haven't tried it yet to see what will happen. I'm interested to see will the fridge not work while driving or will it run my leisure batteries run down if the power is run through them. Everything else is isolated while the engine is on. The fridge going thru my batteries would be preferable as the B2B would sort that out. Today's sunng so jobs in the garden. Tomorrow's raining so jobs in the camper!!
 
Sep 29, 2019
273
486
Funster No
64,845
MH
Forte
Exp
10years
olley - you're a very similar van to me and I'm likely to be doing a very similar job to you. Did you use 16mm2 or 25mm2 when doing the run?
 
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olley
Jul 29, 2007
6,526
39,280
Ipswich
Funster No
32
MH
RV and PVC
Exp
30 years
16mm only because I have two 50m rolls, ::bigsmile:
Seriously this is ok its rated at 60amps but very rare if ever the bb will be drawing that through them, it's also easier to thread from one battery to the other.

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