B2b

[Dee101]

I’m looking to fit a B2B.
I have a 1995/6 Hymer. So it doesn’t have a “smart” alternator. Neither is it therefore euro 4,5 or 6 etc. compliant.
I have 2–70ah lead acid batteries that provide me with electricity.
I have looked for something that works, but in the small print B2B’s seem to be for “smart” alternators only.
So if someone can put me in the right direction, it would be much appreciated.

 

[Itsmcb]

B2Bs are not just for smart alternators although they are recommended to use with smart ones. You can use a B2B with any alternator, just ensure its not too powerful for your alternator. 30 amp is what is normally recommended and that would charge 2 -70ah batteries very quickly. Your van should currently have a split charge device which charges the batteries, I believe this would need to be disconnected.

 

[autorouter]

The standard method of charging a leisure battery is to simply connect it in parallel with the starter battery when the engine is running, so that the alternator can charge both batteries. The alternator sees the batteries as one single big battery. This works OK in general, with non-smart alternators, provided the leisure batteries are a similar chemistry to the starter battery. The connection is made with a split charge relay (electrically operated switch), which connects when the engine is running, and disconnects when the engine stops.

A smart alternator does clever things like only switching on when you lift off the accelerator or apply the brakes, so it is using otherwise wasted energy. It purposefully doesn't fill the starter battery, so there is always space to take a bit more charge. So if the leisure battery is just connected in parallel, that won't get filled up either.

A B2B takes power from the alternator in the same way that the lights, wipers and fans do, and pushes out an optimised charging voltage for different battery types. It's a good upgrade for a non-smart alternator, and an essential device for a smart alternator.

If you are fitting a B2B, it may conflict with the split charge relay, so that needs to be accounted for. How to actually do that depends on the details of the existing charging arrangements, but is usually reasonably easy.

 

[Itsmcb]

What he said

 

[jumar]

I'm doing the same with great advice that Lenny HB and autorouter have given to me..

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[rob1234]

hi i fitted the sterling 30 amp b2b to my autotrail ..i spoke to sterling about removing the s[plit charge system ,,the guy said it is possible to leave it in place ,and i should try it and see if it works ,,its been fitted for a around 2 months now and all seems ok ,,,

 

[jumar]

hi i fitted the sterling 30 amp b2b to my autotrail ..i spoke to sterling about removing the s[plit charge system ,,the guy said it is possible to leave it in place ,and i should try it and see if it works ,,its been fitted for a around 2 months now and all seems ok ,,,

I'm expecting the same result....once my new battery is installed...

 

[Hoovie]

The thing with a lot of electrical mods is even if they are not done in the best way, they "seem ok". But it does not make them the correct way to do it and certainly not the optimum way to get the best out of a system.

The typical Split-charge system using a relay to join the Starter and the Leisure Batteries together should not be left active if you want the best out of an intelligent Battery to Battery Charger. End of.

 

[rob1234]

ok thanks i will try disconnecting the split charge to see if it performs any better,,do you think there is any sort of risk of damage or just a performance thing ,,?

 

[Hoovie]

ok thanks i will try disconnecting the split charge to see if it performs any better,,do you think there is any sort of risk of damage or just a performance thing ,,?

Should not be any damage, it should just be a performance thing. Investing an fairly sizeable amount in a B2B, you want to make sure you get the best from it

One thing I did find whilst I was playing around with setups is if you end up with feedback loop e.g. the output of a B2B connected to the input of the same B2B, it can end up running at constant full power and get rather warm! This is what would happen in a setup where a split-charge relay was active as that just connects the two batteries +ve's together, cause the Relay to stick on even after engine stopped (if it happens to be a VSR) and after a time would not be that healthy for the B2B.
The Split-charge on the Sargent system in your autotrail is not quite that basic but still could give potential issues if left running in parallel

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[rob1234]

Hi thanks ...what would I have to do to disconnect the split charge..

 

[Hoovie]

Hi thanks ...what would I have to do to disconnect the split charge..

there are various ways that people employ, depending on how technical you want to get, and also which sargent unit you have (as you have an Autotrail, it is 99.9% certain you have a Sargent system in place).

You could fit a 5-pin relay between the Starter Battery cable and the Sargent unit, controlled by the D+ signal and setup in such a way so when you start the engine, you lose the Starter Battery +12V, and then when you stop the engine the +12V is restored. With no 12V from the Starter, the split charge relay has nothing to do.
This is probably the option that is closest to keeping all the features. If you do a forum search you will find more details and probably some diagrams.

You could remove the D+ signal from the Sargent Unit so it never knows the engine is on and so the Split-Charge never activates. If you do this however, the usual feature of all the hab electrics turning off with engine start doesn't happen. This may be a good thing or a bad thing depending on your viewpoint (I think it is a bonus to remove that annoying 'feature' )


You could just pull the Starter Battery Fuse from the Sargent Unit. This will stop the Split -Charge working but it would also stop you being able to switch to the Starter Battery from the Control Panel or check its voltage. On the later more advanced Sargent systems, it would also stop charging both batteries from EHU or Solar.
This is probably the easiest option but most 'extreme' due to the way it removes features that can be quite handy.


NOTE: The Sargent kit with the D+ kit also controls the Auto Retraction of the Electric Step if fitted and supply of 12V to the fridge when engine is running, and you probably want to retain those features. Depending on the sargent system again may determine the best option to use. The easiest way to check is probably pull the Starter Battery Fuse from the main Sargent box and see if the fridge and step still works. IF they do, then you have lots of options. If not, you need to evaluate more.

 

[autorouter]

One easy method works if the B2B is not too powerful, not more than 30A. The Sargent box should be capable of handling say 30A, through the split charge relay connections.

Disconnect the starter battery input to the Sargent box, it will be connected to one of the terminal bolts, probably labelled B1 or B2. Connect that wire to the B2B starter battery input instead. Then run a new wire from the B2B output to the starter battery terminal bolt on the Sargent box, that you just disconnected.

The charging amps will go from the B2B, through the split charge relay, to the leisure battery. The split charge relay will switch on at the same time as the B2B starts up, and will switch off when the engine stops.

If the B2B is too powerful, say 50A or 60A, the Sargent internal wiring won't be able to handle it, so it's better to wire the B2B directly to the leisure battery and find some other method to disable the split charge relay

 

[rob1234]

h thanks its a 30 amp and i already wired it up as per the sterling website ,,d you have any diagrams of this sounds the easiest for me ,,