Caution - only for those with an hour to spare! More B2B Queries and Advice Required

[Bustup15]

For anyone following my saga of trying to get a Sterling B2B working in conjunction with a Dethleff WITHOUT losing any existing features such as battery monitoring - list of attempts below.

I have added in simplified wiring outlines for the various steps I have tried and detailed the pros and cons.

What I have been unable to achieve to date is a fully working B2B, with all original battery monitoring AND to break the loop back between the existing charging regime linking the battery banks together. I'm not convinced this is possible but if not can someone confirm that I'm not doing any harm from the setup in Attempt 3 which provides the best outcome currently.

Attempt 1 - details wiring connections prior to any changes

Attempt 2 - as per the Schaudt manual for a Schaudt booster which from the tech specs seems to do exactly the same job as the Sterling. Disconnect the input form the HSM, feed this as the input to the B2B and the output of the B2B goes to the original input to HSM. Although this doesn't seem logical it is as per the provided wiring shown the the HTM manual to connect a booster. This only works at the first engine startup. After that the B2B never starts again due to showing low or missing leisure battery. I suspect this is caused by the inbuilt relays separating the 2 battery banks when the ignition is turned off and the B2B not seeing them at 2nd start for some reason?

Attempt 3 - disconnect the input to the HTM altogether. Feed the output of the B2B directly to the leisure battery. This works but provides no indication of the engine battery at the main panel or the Zenec display. Shows charge at the B2B with 12.8V incoming and 14.4v output. However as the 12V input to the HSM is missing there is no D+, so no voltage at fridge when engine is running and it remains on the gas feed.

Attempt 4 - best so far. Replace the engine battery to HSM feed as per the original wiring, feed the B2B in from the engine battery in position on the HSM. When ignition off, all the battery monitors show correct voltages. Engine running both battery banks show virtually identical voltages at 14v+ although the main battery monitor for the leisure battery also shows maximum load going out - I assume this is the loop back between the 2 charging systems causing the monitor to read incorrectly. On ignition off, the displays return to normal. Is this causing any other issues such as overcharging?

Attempt 5 - there is an option a booster out feed on the HSM in conjunction with a jumper change. The German manual on translation seems to infer if the B2B sits between the engine battery and the HTM then the HTM can't charge the engine battery back through the B2B. I'm not clear if his refers to on engine running or on mains hook up? However if the engine battery is connected to this output the original battery in connection is dead therefore the B2B doesn't start.

 

[autorouter]

I think you have two separate problems, possibly three.

First, if the B2B doesn't fire up when the output doesn't see the Leisure battery, you need to find an alternative input method that connects to the leisure battery all the time. The split-charge relay (Trennrelais) connects the starter battery to the main distribution bus inside the HSM-01 when the engine is running. The main distribution bus connects to one side of the measuring shunt, and the leisure battery connects to the other side of the shunt. You need to find an input that goes direct to the bus, not through the split charge relay.

There's a whole list of things that connect to this bus, including the inverter, User circuits 1 and 2 (Kreiss 1 & 2), the solar controller output and the EBL Leisure battery connection. You could use any of these if they are spare. Kreiss 2 for example. This would be the same as connecting direct to the leisure battery, but with the advantage that the amps would be measured and accounted for by the display, because they pass through the shunt.

The fridge 12V while driving is another problem. Originally it connected to the starter battery wire inside the HSM01 between the starter input and the split charge relay. If you move the starter battery input as above, that disappears. There is provision for this. The solution is to move the jumper that connects A12 to A13, so that it connects A11 to A13 instead. Then you have to run a wire from the alternative starter connection (the Booster connection) to the starter battery, with a suitable fuse, max 25A.

So to summarise, it's like the '2nd Attempt' diagram but with the B2B Leisure out connected to Kreiss 2 instead of Eng +. And another additional wire from HSM01 Booster input to Starter battery with a 25A fuse.

This will also solve another minor niggle, and the mains charger will then charge the starter battery as it did before.

The D+ problem I haven't looked at yet, but you might find it's OK now.

Edit: Just realised the extra wire from the HSM01 Booster terminal doesn't need to go all the way back to the Starter battery, it can go to the B2B ENG IN terminal. Don't forget to switch the A12/A13 jumper first.

 

[Lenny HB]

Going back to square one just wondering why you are fitting another B2B when the HSM01 has a build in 30 amp B2B I can't see the point in fitting another one unless you are going to fit Lithium batteries.

This article may be of interest as its about a Dethleffs.

Future Motorhome Charging?

Ground Breaking Charging and Power Integration in a Motorhome? Dethleffs new approach is revolutionary in starting with a high power backbone that can integrate with any charger manufacturer.

www.aandncaravanservices.co.uk

 

[autorouter]

Going back to square one just wondering why you are fitting another B2B when the HSM01 has a build in 30 amp B2B I can't see the point in fitting another one unless you are going to fit Lithium batteries.

I assume you are looking at something like this:
"The HSM 01 has provision for an 'Alternator charge booster' that will raise the voltage from the Alternator to the 14.4v, or whatever is required, for the habitation batteries."

What he means is that connections are provided for the 'Alternator charge booster', not that one is built into it already.

The OP has already tried to use this connection, and has found at least two problems with it. Maybe other brands of B2B do not give up when they are disconnected from the leisure battery, but this one did. The other problems of the fridge and mains charging would be solved by better instructions, preferably in English, but the German instructions are minimal too.

 

[Lenny HB]

I assume you are looking at something like this:
"The HSM 01 has provision for an 'Alternator charge booster' that will raise the voltage from the Alternator to the 14.4v, or whatever is required, for the habitation batteries."

What he means is that connections are provided for the 'Alternator charge booster', not that one is built into it already.

The OP has already tried to use this connection, and has found at least two problems with it. Maybe other brands of B2B do not give up when they are disconnected from the leisure battery, but this one did. The other problems of the fridge and mains charging would be solved by better instructions, preferably in English, but the German instructions are minimal too.

But it's a brand new van he just imported and I assume it will have a Euro 6D engine so there will be a B2B fitted to charge the leisure batteries as the Fiat Euro 6D have a smart alternator even the ones for the Motorhome market.

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[Bustup15]

autorouter
Many thanks for all the input.
The info on the various connections on the HSM is particularly helpful as I've struggled to find any specific information and auto translating a tech manual always leaves you with a feeling that something horrible may be misconstrued!

See Schaudt comment below, my current wiring scheme 3 is 'approved' although as I now have cables made up with terminated ends it will be a 10 minute job to try your suggestion and if not successful revert to mine.

Lenny HB
Thanks again for your input. The reason I decided on a B2B was I found last year when the sun was hit and miss and we were off hook up the batteries didn't seem to get much of a charge even driving some hours. The Dethleffs manual also indicates that it's not possible to fully charge the leisure batteries whilst driving.

The van was imported new in May 2019 it's not a brand new import.

I did get a reply from Schaudt today as I raised the query with them about the possibility of disabling their inbuilt relays to prevent linking the engine and hab batteries together. They indicated that my option 3 connections are ok and will allow charging and more importantly not do any other damage to the systems.

I bought a Sterling unit as it had so many Funsters giving it good ratings, in hindsight I wish I had purchased the Schaudt unit as it would have been an easier install with full tech support from a single manufacturer. Both Sterling and Schaudt understandably wouldn't commit on tech questions as they didn't know the others systems in any depth.

 

[Lenny HB]

The van was imported new in May 2019 it's not a brand new import.

Don't think it will be Euro 6D so standard alternator, surprised you don't get a good charge the the standard set up. Normally Hymer group vans have decent size cables and split charge relay to give a good rate of charge.

 

[jeffcav]

I wonder if you have the 'missing wire' referred to in this article - http://www.aandncaravanservices.co.uk/the-future.php. they also mention adding a B2B should be a doddle, they seem like nice guys, maybe give them a call might sort you out. good luck.

 

[Bustup15]

I wonder if you have the 'missing wire' referred to in this article - http://www.aandncaravanservices.co.uk/the-future.php. they also mention adding a B2B should be a doddle, they seem like nice guys, maybe give them a call might sort you out. good luck.

I dont think so. The article does state that the issue had already been resolved with a revised wiring loom and doesn't say what the issue was.

They say fitting a B2B should be a doddle, not in my case despite following the provided wiring info for a Schaudt install (although fitting an alternative manufacturers kit).

I'm sure the writer is highly proficient and experienced to resolve issues but my take was this was their first glimpse at a new product and their overview, but not based on any substantial experience of this particular product.

All now resolved and working thankfully.