# Fitting B2B and solar with old Elektroblock



## WelshTom (Sep 30, 2018)

Hi everyone

I've recently become the owner of a 1998 Hymer and am looking to upgrade the electrics a little bit to allow us to camp comfortably without the need for EHU very often. The van currently has a single 110ah leisure battery fitted and uses the older Elektroblock EBL 104-3. I'd like to add a second leisure battery and fit a large solar panel to the roof. I've read loads of posts and articles, but most relate to the more recent versions of the EBL so I'm a little confused!

I read on the A and N website about the problems associated with running 2 batteries off that EBL, that the charger built in is too small to support larger battery banks when running on the alternator so I thought about utilizing a B2B charger with built in solar regulator and bypassing the EBL for the leisure battery charging. I've looked at the CTEK D250 and Ring RSCDC30 B2B chargers as these both take a solar input as well as the alternator and automatically decide which input to use. They also regulate the charge to the leisure battery to make sure it gets a proper charge without destroying the battery (which seems to be the main concern with some B2B chargers).

My questions are:

1. Is this a sensible approach?

2. Am I correct in thinking that if I did this I would wire the charger in battery to battery and excluding the EBL totally? 

3. Would I then need a relay on the wire between the EBL and leisure battery to isolate the EBL charger when charging via B2B? How would that work with the solar part? (I'm assuming that if I isolate the EBL from the leisure battery when the engine is not running it wouldn't get power from anywhere? Would I therefore need the relay to sense where the power is coming from and isolate the 12v or not depending on whether the B2B or solar is charging? 

4. Would I be better off scrapping the B2B and having a basic voltage sensing split charge relay to charge the Leisure battery (with a second relay to isolate the 12v from the EBL when this is running), and a separate solar regulator which could be left on all the time? 

I appreciate that loads of similar threads exist and have tried my best to read them all but none seem to address the questions I'm raising directly so any help would be much appreciated. 

Many thanks, Tom


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## powerplus (Oct 6, 2014)

hi and welcome

i think the main problem with the alternator and chargers playing up is when there are 2 batteries connected and they get to low resulting in the alternator or charger working to hard

if you keep on top of the batteries and dont let them get to low then the charger wont work to hard

if you have had experience with old battery chargers with a ammeter on them when you first put a flat battery on charge the ammeter reads high and as the battery tops up the ammeter reduces its output

a decent solar panel will help no end i started with 100w but ended up going to 200w


barry


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## erneboy (Feb 8, 2007)

There are old threads on here covering this topic in detail. Advice from Schaudt is included.

In effect a B2B is more than an EBL can handle, so you just go directly to the battery. The downside is that your EBL readings will be inaccurate till it sees that the batteries are fully charged.

That's from memory but I did this around 8 years ago and involved Schaudt for advice. All the info is on the old site. A search may turn it up.

I'll try when I have time but I'm travelling for the next day or two.


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## erneboy (Feb 8, 2007)

Here's one thread which covers it. https://forums.motorhomefacts.com/182-electrical/121406-b2b-charger-question.html

It seems the advice from Schaudt varies.

You can email them your questions and they'll answer.


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## WelshTom (Sep 30, 2018)

Hi both, and thanks for the replies.

*erneboy* - Thank you for the link, however that thread is for the EBL 99 which is a more recent version than the EBL I have. With the EBL 99 they fixed a lot of the issues I have (they uprated the cabling, swapped the 20a connectors for 50a ones, and upped the power of the charger). I'm pretty sure the maximum input that the EBL I've got can take is 10a which wouldn't be enough for either the B2B or the Solar unfortunately. I may take your advice regarding contacting Schaudt, suppose they are the best ones to ask!

*powerplus* - Are you saying then that as long as I look after the batteries and don't let them discharge too much I should be OK with the built in charger (both from the alternator and the 240v)? I appreciate that the solar should help keep them topped up but i really don't want to wreck the EBL!


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## WelshTom (Sep 30, 2018)

Hi everyone

I think I've got this all worked out now. I've ordered a Ring RSCDC30 combined B2B and solar regulator and will wire this directly between the batteries and connect up a 280w solar panel that I've also bought. I've just got a couple of little questions I'd like some more help with if anyone can:

Do I need to isolate the EBL from the battery while it's charging? I'm concerned that there is a risk of too much current being forced into the EBL via the battery from the B2B. I'm thinking that a simple relay would suffice when travelling but it gets more complicated when on solar. 

Is it possible to use a 240v to 12v transformer to power the B2B when on a hookup? I know this sounds like an odd one, but surely all 240v to 12v chargers must use a transformer, and the charging circuitry in the B2B is likely more sofisticated than that of a 20year old EBL? I'm also thinking that in this setup I could inset a diode between the battery and the EBL to allow the current to go to the EBL, but stop the EBL charging the battery. That way I can make sure that the B2B handles all leisure battery charging and the EBL and alternator look after the starter battery. This should ensure I don't overload the EBL regardless of how big a leisure battery bank I use, and the leisure 
battery gets a constant multi step charging. 

Any thoughts would be greatly appreciated, thanks.


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## nickkdx (May 26, 2009)

I fitted a second battery to my 2001 Hymer b584, the battery is under the seat and had no problem.
I’ve got a Schaudt LR1218 solar regulator for sale and this charges both battery’s, I changed it for a MPPT type regulator but only to help in low light times, the LR1218 has worked fine for several years, charging 2 off 110amp battery’s and the engine battery.


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## WelshTom (Sep 30, 2018)

Hi nickkdx, thanks for your post. Unfortunately by 2001 I think all Hymers had the EBL 99 fitted which doesn't have the same issues as the EBL in mine. The maximum solar input is 10a, which is less than the 280w panel I've got could potentially deliver so I know I have to circumvent the EBL for the solar input. If I had the later EBL I would definitely have been interested in the solar regulator you've got.


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## Pudsey_Bear (Sep 25, 2008)

My thinking would be to turn off the EBL altogether, use the new set up, and only use the EBL if there is no sun or no need, IE on EHU and/or van covered in snow, then I would take out the solar panel fuse.


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