B2B preference

AMK

AMK

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Feb 2, 2013
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gainsborough
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24,534
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Since 2014
When spring eventually comes the first job on the Moho this year is to fit a 30 amp B2B, I was just wondering about what make to go for.

Is Sterling really the best option or are there funsters who recommend others.

It will be fitted to a Euro 5 engine, and located at the rear with about 7 metres from the cab Bat.

Thanks in advance Alan
 
I am very happy with my Votronic VCC B2B. It is a good quality alternative to Sterling, both have good reputations.
 
I prefer Sterling products. Their product knowledge and willingness to help is brilliant. I love the way that if you have application questions you can talk to the guys who actually design the kit. Great company (y)
 
AMK said:
When spring eventually comes the first job on the Moho this year is to fit a 30 amp B2B, I was just wondering about what make to go for.

Is Sterling really the best option or are there funsters who recommend others.

It will be fitted to a Euro 5 engine, and located at the rear with about 7 metres from the cab Bat.

Thanks in advance Alan
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I fitted a Sterling and it has been fine. They are easily contactable which is useful as they give little to no advice in their written instructions on how to install in a MH.

Some will say 7m is too far from the cab battery but it will be no problem if you fit thick enough cables. Folk on here will be able to advise if you get stuck.

See the link in my signature for how I installed mine.
 
I find the cable size calculator here very useful

Cable Size Calculator - Cable sizing and selection | 12 Volt Planet

Cable Size Calculator - Read our guide to selecting cable of the correct type and size for your automotive, marine or leisure wiring application. Auto and Marine Electrical Components from 12 Volt Planet
www.12voltplanet.co.uk

It looks like 16mm just scrapes in but 25mm would be better.

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Sterling recommend 25mm for a run of 7m. I’m thinking of adding a B2B and, like the OP, will have a cable run of 7m or so. I may go over the top and use 35mm cable. That should ensure minimal voltage drop, or is that going a bit too much over the top?
 
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For 7m at 30A the calculator gives the following voltage drops:
16mm .45V 3.75%
25mm .29V 2.42%
35mm .21V 1.75%
Maximum recommended is 3-4%.
 
What I can never understand is that manufacturers never account for cable size when they design the connection's to there product
 
foxy said:
What I can never understand is that manufacturers never account for cable size when they design the connection's to there product
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What do you mean like this ?

Image1.jpg
 
Another vote for Sterling products.

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G7UXG said:
Sterling recommend 25mm for a run of 7m. I’m thinking of adding a B2B and, like the OP, will have a cable run of 7m or so. I may go over the top and use 35mm cable. That should ensure minimal voltage drop, or is that going a bit too much over the top?
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It's not a big issue with a B2B. The B2B takes whatever voltage is thrown at it, and boosts it to send out the correct voltage for charging the battery. I'd say 25mm2 is fine.
 
G7UXG said:
Sterling recommend 25mm for a run of 7m. I’m thinking of adding a B2B and, like the OP, will have a cable run of 7m or so. I may go over the top and use 35mm cable. That should ensure minimal voltage drop, or is that going a bit too much over the top?
Click to expand...

I fitted a Sterling BB1260 for a friend a couple of weeks back and I think you may well find that 35mm2 will be to big for the clamping terminals on the unit to handle.
 
I have a Votronic B2B, partly as I already had their MPP solar controller, which is excellent. The B2B developed a fault a few months after I'd fitted it. Rather than contacting the UK supplier initially, I emailed Votronic to see if it was an issue they were aware of and whether there might be a simple fix. They immediately arranged for me to send it to them and delivered it back to me within a week, with a covering letter saying that not only had they replaced the faulty component but also replaced several other parts that had been modified in subsequent production and flashed it with the newest firmware. It has been fine since and I call that excellent customer service.
 
just thinking aloud.

The 7 metre cable run from the Hab to the B2B will not be 30 amp because that will be after it’s boosted by the B2B.

So the 25mm2 should only be from the B2B to the Hab.

Maybe best to use both the same though.



Thanks for all the reply’s.
 
AMK said:
just thinking aloud.

The 7 metre cable run from the Hab to the B2B will not be 30 amp because that will be after it’s boosted by the B2B.

So the 25mm2 should only be from the B2B to the Hab.

Maybe best to use both the same though.



Thanks for all the reply’s.
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I stand to be corrected, but where will the 30 amps come from if not from the alternator/cab battery via the cabling to the B2B, the B2B can not magic amps out of thin air.

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Bought us a Votronic as we already have Votronic solar mppt controller and Votronic sinus inverter, which we have found to be really competent pieces of kit!
 
AMK said:
The 7 metre cable run from the Hab to the B2B will not be 30 amp because that will be after it’s boosted by the B2B.
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Technically you are right, it won't be 30 amps. If the output is 30 amps at 14 volts, that's 30 x 14 = 420 watts. If the input voltage is lower, let's say 13V, then the B2B will draw extra amps to provide that power. So the input amps will be 420/13 = 32 amps. Plus a bit more for inefficiencies.

So to get 30 amps out at the boosted voltage, more than 30 amps has to go in.
 
That would be better, more flexible.
 
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Two on Tour said:
If your going to use the 30 amp model, the 16mm2 cable will be plenty as that is rated at 110 amps.
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16mm2 might be good for 110A over a very short distance but if you were pulling 110A through 7 metres your 12v would be down to 10.35V by the time it arrived. Cable capacity very much depends on length of cable and I think manufacturers/suppliers who quote cable capacity in Amps alone are irresponsible.

30A over 7 metres is marginal, with a voltage drop of 3.75%. The recommended limit is 3-4%.
 
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Pausim said:
16mm2 might be good for 110A over a very short distance but if you were pulling 110A through 7 metres your 12v would be down to 10.35V by the time it arrived. Cable capacity very much depends on length of cable and I think manufacturers/suppliers who quote cable capacity in Amps alone are irresponsible.

30A over 7 metres is marginal, with a voltage drop of 3.75%. The recommended limit is 3-4%.
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But it's not going to be 12v as the B2B will be operating with the engine running and the alternator pumping, what 14.2 volts or there about's. (y)
 
Two on Tour said:
But it's not going to be 12v as the B2B will be operating with the engine running and the alternator pumping, what 14.2 volts or there about's. (y)
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True but 7 metres is a long run and even at 14.2V there will be losses. I prefer to have a bit of a margin in my wiring and 16mm2 cable is bang on the recommended limit at 7 metres.
 
Two on Tour said:
Personally, I think Sterling know what they are talking about when it comes to their product.

View attachment 361685
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Fair enough. My calculations are based on flow and return but Sterling could reasonably be assuming direct earthing of the negative to the chassis with minimal losses.

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So I read that as 6mm2 and the awg is the cable thickness 10 mm?
 
AMK said:
So I read that as 6mm2 and the awg is the cable thickness 10 mm?
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The AWG and figure in blue is American Wire Gauge which is another form of measurement for cable, the figure in black is the most common used on this side of the pond.
Although they state 6mm2 on a 7m run and I now I know I'm going to give ammunition to Pausim but I would up that size. :oops2:
 
Yeh I’m going to stick with the 16mm2, I think that’s the best thing to do.
 
It doesn’t matter if you got some voltage drop from alternator to B2B, as long as the cable is capable for a 30a plus few extra for boosting up. Even a 10mm will be plenty enough, but, from B2B to the battery you can’t afford voltage drop, as the battery will se a lower voltage than what is set at B2B. So from B2B to battery you want 16mm for up to a meter. Any tying longer needs 25mm.
 
The Sterling B2B has a facility to cope with voltage drop from the vehicle battery. It's covered in the instructions but basically you run a thin second cable to the battery and connect the other end to the appropriate terminal on the B2B. Because virtually no current is drawn down this wire the device knows the voltage at the battery and adjusts accordingly. :)

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