Wiring Votronic B2B through an EBL119

[gerry mcg]

Apologies for the long post, but I’m looking for a bit of assistance wiring my Votronic VCC1212-50 B2B via my EBL119.
ive had some electrical gremlins since it was wired by my local auto electrician, and ive removed it until i can get to the bottom of things.

i have an EBL119, so if i understand correctly, i can wire the 50A B2B through the EBL and utilise the Split charge system in the EBL. Am i correct in saying the EBL has an “internal” split charge relay, as in it is inside the EBL? (Out of interest, if i wanted to wire the B2B directly to the leisure battery, how would i disable the EBL split charge relay?)

i’m attempting to wire the B2B as per this configuration.

I have fitted

• a D+ wire,
• a fused Vs+and Vs- paired wire direct from the starter battery terminals;
• a fused Bv+ and Vb- paired wire Direct from the leisure battery terminals; and
• a temp sensor wired direct to the -ive terminal post of the lithium battery

so the wiring to the front of the B2B is pretty straightforward

the question relates to wiring main battery cables to the VCC1212-50 and EBL.

my EBL has the following cables,

• a red “Starter battery +ive input” on the left which is fused to a 50A maxi fuse in the under floor starter battery box
• 2x brown ”common ground” -ive wires in the central terminal, and a
• single Black leisure battery +ive output

My question is how to wire the B2B into the loop.
my understanding is

• the red “Starter battery +ive input” which was on the left terminal of the EBL (which is fused to a 50A maxi fuse in the under floor starter battery box) should be wired to the left (IN START) terminal of the B2B, and
• i should add a red “Starter battery +ive output from the right (OUT BORD) terminal of the B2B to the “Starter battery +ive input” terminal of the EBL.

But what do i do with the Common grounds?

Do i move one / both of the pair from the EBL to the B2B? Or add another to the system? This is the bit that is not clear. If i understand teh B2B wiring diagram, i do not need to deal with the small relay circuit to the right og the diagram.

With the B2B set to 14.4v Lithium profile, am i correct to expecting the voltage across the B2B “IN Start +” and “12v Comm -” terminals to be the alternator voltage (say 13.7v with the engine running?
and the voltage across “12V Comm -“ and “OUT Bord +” B2B terminals to be 14.4V (and no higher)?

and the voltage across the EBL “Start In +” and -ive terminal should be 14.4V (as that is what is incoming) and the Voltage across the EBL”-ive” and Black Leisure out should be whatever the leisure battery voltage is at at the time (same as what the BMV shunt reports?)

 

[Lenny HB]

I think you have it right assuming the grounds in the EBL one goes to the hab battery and the other to the B2B, often with B2B's it's recommended to put another ground wire between the batteries so you are not relying on chassis grounds.

 

[gerry mcg]

the 2 grounds in the middle terminal of the EBL are the way the van Came from the factory & this is the bit i am stuggling with to understand to be honest...

I guess one id from the statter battery and one is from the leisure battery...
so the question i have is to work out whether it is OK to move one to the B2B and leave one on the EBL, , or some other solution...
do i need to be careful which one i move or is it irrelevant, or important?
the Auto electrician just wanted to put a ground cable from the B2B to the chassis via a seat bolt.... but i was not so keen on that idea. It didnt seem correct to me

 

[Googlebot]

I just moved them both to the B2B and then put one large cable back to the terminals.

Thread is here.

Post in thread 'Making the change from lead acid to lithium - a thread with pictures'
https://www.motorhomefun.co.uk/foru...um-a-thread-with-pictures.233686/post-4304108

 

[Lenny HB]

I would put a busbar in for the grounds then connect those 2 grounds to it a cable from the busbar to the EBL and another to the B2B.
All the cables look a bit on the small side to me probably worth replacing with 25mm sq cable.

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[gerry mcg]

Would 25mm2 not be overkill? I know big is better….. but…
its a German van, and cables are normally sized sensibly.
(however i get that the charge via an EBL split charge is normally limited to 18A or thereabouts and the B2B will push up to 50A And the cables were possibly sized for the std installation with 20A charge rate

From 12v planet, they state
10mm2 cable is rated at 70A,
16mm2 cable is rated at 110A and
25mm cable is rated at 170A
and there is a 50A fuse in the system at the moment.

I guess i might need to up the 50A fuse to say 70A, and in that case, i guess the 10mm cable would be too small as the fuse would no longer protect the cable… 16mm2 would surely be adequate? (Ive only got a 200Ah battey and short cable runs (1-2m)

something to thinks about for sure.

 

[paddymcc]

The only thing I would add is that the lithium charging voltage may be a bit over 14.4 depending on what the temperature sensor is recording. I can never remember which way round it is but I think a battery at a lower temperature can take a slightly higher voltage - so in this weather it may take 14.5v or so...

 

[Lenny HB]

Would 25mm2 not be overkill? I know big is better….. but…
its a German van, and cables are normally sized sensibly.
(however i get that the charge via an EBL split charge is normally limited to 18A or thereabouts and the B2B will push up to 50A And the cables were possibly sized for the std installation with 20A charge rate

From 12v planet, they state
10mm2 cable is rated at 70A,
16mm2 cable is rated at 110A and
25mm cable is rated at 170A
and there is a 50A fuse in the system at the moment.

I guess i might need to up the 50A fuse to say 70A, and in that case, i guess the 10mm cable would be too small as the fuse would no longer protect the cable… 16mm2 would surely be adequate? (Ive only got a 200Ah battey and short cable runs (1-2m)

something to thinks about for sure.

Battery cables in our Hymer are 25mm sq that's the standard Hymer wiring.
It's not so much about current capacity but reducing volt drop which makes the system more efficient.
With short runs 16mm sq is OK, that's what your cables look like.

Edit:
50 amps at 14v, 16mm sq cable will lose nearly 2%, 0.3v, going to 25mm sq will nearly halve the voltage drop.

 

[Lucky]

I admit to being ignorant about these things although I am trying to learn, so please excuse my ignorance.

What is the dotted line shown on the wiring diagram connecting the -ve terminals of the starter and onboard batteries. Is that the extra cable Lenny suggested in post #2, and is it optional (hence the dotted line)?

 

[Lenny HB]

I admit to being ignorant about these things although I am trying to learn, so please excuse my ignorance.

What is the dotted line shown on the wiring diagram connecting the -ve terminals of the starter and onboard batteries. Is that the extra cable Lenny suggested in post #2, and is it optional (hence the dotted line)?

View attachment 561619

Yes.

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[gerry mcg]

Hmmm.
I rewired the B2B last night and tried it.
It ran fine for about 5 min, pushing out 35A or so (lithium battery is pretty much full)
The B2B output voltage across the B2B "12V Com -ive" and "OUT Bord +ive" terminals was 14.85v with the Liesure battery voltage climbing from 13.3v to 14.2ish volts,

Then the 50A fuse by the starter battery blew

I could up the fuse to 70A, . But I wonder why it blew in the first place when it appears to only have been passing 35A..

Before I do that i guess I need to confirm the cables are 16mm2 and rated to 110A and are not 10mm2 and only rated to 70A.

I can recableif if necessary. It's just a hassle

 

[Lenny HB]

The B2B output voltage across the B2B "12V Com -ive" and "OUT Bord +ive" terminals was 14.85v with the Liesure battery voltage climbing from 13.3v to 14.2ish volts,

The output (Bord) voltage I should be the same as the battery voltage apart from any volt drop across the cables. I would try bypassing the EBL the split charge relay contacts could be a bit carboned up.

Then the 50A fuse by the starter battery blew

Could be startup current Lithium's have a very low internal resistance.

 

[gerry mcg]

How does one disable the internal EBL split charge relay? Is it as simple as pulling the 50A fuse from the starter battery area (the one that blew) and running a new larger (fused) cable from the starter to the B2B?
As per

 

[Lenny HB]

Disconnect the starter battery input lead from the EBL and connect it to the input of the B2B. Then connect the output of the B2B directly to the hab battery.

 

[gerry mcg]

^I’ll try that. And the B2B negative would / could go to the ground on the EBL? Or would i be best taking that to the ground terminal of the BMS Shunt?
Out of interest, Is this the split charge relay behind the EBL?

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[Lucky]

Like I said earlier, I know very little of these things but I do have the same B2B and the installation manual provides the fuse requirements. See below.

 

[gerry mcg]

Thanks Lenny HB , i noticed that too. So the 50A is prob undersized.

 

[Lenny HB]

The split charge relay is inside the EBL.
I would leave the ground connections as they are at the moment, get it all working first, assuming your EBL ground connection goes to the shunt.

 

[autorouter]

Then the 50A fuse by the starter battery blew

I could up the fuse to 70A, . But I wonder why it blew in the first place when it appears to only have been passing 35A..

When I fitted my 70A B2B I wired in a 100A Maxi fuse next to the starter battery. It blew, not when first being used but while out on a drive. I replaced it with another 100A Maxi fuse, and the same thing happened. I measured the amps as 69A with a clamp meter.

After discussion with Sterling, they suggested changing the 100A Maxi Blade fuse for a 100A Midi (flat link) fuse. I did that and had no further problems.

 

[gerry mcg]

I’m pretty sure the cabling fitted from the battery to the EBL is 70A Rated 10mm2, not 16mm2 or 25mm2, which is perfectly adequate for the 50A fused cable that goes to the EBL in its standard configuration,
but im a bit nervous about its Factor of Safety for 10mm2 when supplying the higher current to the B2B, so
ive decided to

1. put in new 110A rated 16mm2 cables from the starter battery to B2B,
2. fused with the 80A midi fuse as per the wiring directions direct to the “IN Start +IVE‘ B2B terminal,
3. disconnect the 10mm2 cable from the starter battery, remove the 50A fuse and disconnect from the EBL to remove the Split Charge relay from the system
4. wire the “OUT +ive Bord” B2B terminal direct to the leisure battery +ive via new 16mm2 fused with 60A midi fuse as per the simpler second Votronic wiring diagram above,
5. wire B2B “12v Com -ive“ B2B terminal to the Ground side of the Leisure Shunt With new 16mm2 cables

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[Lenny HB]

As you are going to change the cables might as well fit 25 mm sq and reduce the volt drop to a minimum. Also while at it change the cables from the hab battery to the EBL.
I'm a bit surprised being a German van they only used 10 mm sq cabling.

 

[gerry mcg]

so am I. There is no marking on it thats I can see easily but it appears to have the same OD as cable I have that is marked as 10mm2

I appreciate what you are saying, but my battery runs are very short (less than 3m) with start battery under passenger floor, B2B under passenger seat and leisure battery under driver seat)

The cable sizing calculator on 12v planet states For a 2m 'one way' I.e. a 4m total circuit)
16mm2 cable at 14v and 50A current draw has a 1.8% (0.252V) voltage drop vs 1.1% (0.154v) for 25mm2 and 2.6% (0.364v) for 10mm2

 

[gerry mcg]

The cables fitted are 16mm2. I found am impression on the positive cable that said 16mm equiv.

 

[Lenny HB]

The cables fitted are 16mm2. I found am impression on the positive cable that said 16mm equiv.

Size of the cable can vary depending on the purity of the copper.

 

[Steve and Denise]

The cables fitted are 16mm2. I found am impression on the positive cable that said 16mm equiv.

I am attempting exactly the same setup on a Cbe unit but only 30amp on 16mm sq wire.

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[paddymcc]

The only thing I would add is that the lithium charging voltage may be a bit over 14.4 depending on what the temperature sensor is recording. I can never remember which way round it is but I think a battery at a lower temperature can take a slightly higher voltage - so in this weather it may take 14.5v or so...

Hi Gerry I just got around to looking at the Votronic manual and realised that I am wrong regarding this: the variable charging profile according to temperature only applies to lead acid batteries not to lithium ( except below freezing of course). Must be something about the different chemistries.
So if it is set to charge at 14.2v or whatever that is what you should see at the leisure battery.

 

[gerry mcg]

Ok, ive wired the B2B direct to the leisure battery as per the direct wire diagram above with new 16mm2 cables and all appears well.

i swapped the 50A fuse beside the starter battery for the cable that supplies the EBL (now B2B) with an 80A one and added a 60A fuse on the +ive cable at the Leisure battery end as per the wiring diagram

ive retained the original starter battery +ive cable , but disconnected this from the EBL119 Starter +ive in and used this as the power supply for the B2B. There is now no Starter battery in wired into the B2B.

Am i correct in thinking by removing the starter battery +ive from the EBL, this disconnects the EBL Split charge relay from the circuit?

im getting 50A now reliably from the B2B to the Leisure battery but the B2B output voltage measured at the “12V Comm - ive” Black and ”+ive Bord” red cable terminals on the B2B is only showing as 14.15V, despite the B2B being set at Lithium 14.4V . Should this be 14.4V? Or should it be the “average” of the 14.4V being supplied, and the say 13.9V that the Leisure battery is registering? (In which case 14.15V is about right)

I am also a bit surprised the B2B green full charge light wasn’t illuminated when the battery was showing as fully charged on the BMS and the B2B was still putting out 50A…. I would have expected it to have tapered off. (When i had it wired via the EBL, the Green light would flicker as it approached full charge, and become fully illuminated as it was fully charged.

there is a Starter Battery and Liesure battery voltage wires connected to the B2B and a temp sensor wire connected from the leisure battery -ive terminal.

 

[autorouter]

Am i correct in thinking by removing the starter battery +ive from the EBL, this disconnects the EBL Split charge relay from the circuit?

Yes, correct. The split charge relay will still switch, but because nothing is connected to its input, it will have no effect on anything.

There's two things with the voltage. First, you wired two thin pos/neg sensing wires to the leisure battery, so the B2B should compensate for the voltage drop in the power wires by increasing the voltage slightly, so that the battery actually gets 14.40V at its terminals. The voltage at the B2B terminals should be a bit more than 14.40V.

However you have also wired the temperature sensor for the leisure battery, and I don't know what effect that will have on the battery voltage. If you disconnect one of the sensor wires, it will work without temperature compensation, so the voltage should be as above.

 

[gerry mcg]

The Votronic B2B won't work on a lithium setting without the temp sensor being attached

 

[gerry mcg]

You will be pleased to know all now appears well. I went out to van this morning and hey presto - all working as i expected!

The voltage across the _ive and +ive B2B output terminals was 14.5-14.6v, (i guess this is >14.4v as the B2B is outputting more at the terminals to make up for voltage drop in the cables - balancing with the voltage sensor wire) with the voltage across the leisure battery voltage sensors 14.2, rising to 14.4v, at which point the green light began to flicker and the Amps began to tail off from 50A to <20A, which is what i expected. The Voltage at the leisure battery remained constant at 14.4v. So all appears well this morning.

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