The B2B question

[Bore1]

Hi guys.
After alot of expert tips and guidance of installing my lithium, i have ordered a B2B Victron 30Ah charger.

I have a CBE DS300 distribution box with integrated battery splitter. And its the version without the r37 resistor you can remove to fit a b2b.
My main question is this:
I have a 10mm2 positive cable from startbattery with a 50A fuse that goes to the +B1 on the ds300., and a 10mm2 positive from +B2 to leasure. Could i just wire the B2B directly to the +B1 and +B2, or do i have to pull a new cable all the way to the start battery?

 

[Winger]

Sorry I can’t help but your back to the top of the page now!

 

[Lenny HB]

Sorry don't know about CBE units but with the unit at the back of the van 10mm cable is on the small side I would upgrade to at least 25 mm sq if not larger to minimise any volt drops.

 

[DBK]

Cable size depends on the cable length not just current load. On this page there is a calculator if you scroll down a bit. Feed in the current (30A), the size (10mm) and the cable length and see what the loss is. You want less than 4% ideally.

Sorry, can't help on installation beyond this as I've no experience of the CBE.

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

 

[andy63]

Hi..id be inclined to make your connections directly to the batteries..that way you will have the option of installing a relay in the start battery wiring to disable the cbe split charge circut..
Hopefully Pausim will look in and point you to his thread which dealt with subject..
Andy

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[bobnick]

Hi guys.
After alot of expert tips and guidance of installing my lithium, i have ordered a B2B Victron 30Ah charger.

I have a CBE DS300 distribution box with integrated battery splitter. And its the version without the r37 resistor you can remove to fit a b2b.
My main question is this:
I have a 10mm2 positive cable from startbattery with a 50A fuse that goes to the +B1 on the ds300., and a 10mm2 positive from +B2 to leasure. Could i just wire the B2B directly to the +B1 and +B2, or do i have to pull a new cable all the way to the start battery?

This may as well have been typed in Chinese for all i could understand of it.

 

[andy63]

This may as well have been typed in Chinese for all i could understand of it.

據我所知，這也可能用中文打了。

 

[bobnick]

據我所知，這也可能用中文打了。

Fully agree

 

[Pausim]

Hi..id be inclined to make your connections directly to the batteries..that way you will have the option of installing a relay in the start battery wiring to disable the cbe split charge circut..
Hopefully Pausim will look in and point you to his thread which dealt with subject..
Andy

I think it was this thread that explored various ways of wiring a B2B with a CBE, started by G7UXG . I used a relay on B1 but I have the DS300 with an R37 resistor, so it may behave a little differently.

Carthago Split Charging Unit

I'm exploring the possibility of putting a B2B charger on my Carthago, but I understand that I'll need to disable the existing split charging unit. Does anybody know where it is? Is it a separate unit, or is it built into the electronic gubbins in the boot? I can't even identify a fuse for it...

www.motorhomefun.co.uk

 

[jongood]

據我所知，這也可能用中文打了。

Sorry Andy Ive looked and looked at this but I think this is a better answer

據我所知，這也可能用中文打了。

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[andy63]

Sorry Andy Ive looked and looked at this but I think this is a better answer

據我所知，這也可能用中文打了。

謝謝


Thanks for the reply and link above pausim..
My apologies to G7UXG for getting mixed up..
And yes I keep forgetting about the differences in the ds300 boards..
Andy

 

[autorouter]

As I see it, there are two problems.

1. When the engine is running, the split charge relay on the DS300 board connects the B1 and B2 terminals together. If you connect the B2B to the B1 and B2 terminals, it will be shorted out, and will have no effect.

The solution is to disconnect the battery wire from the B1 terminal, and the connect the B2B between the B1 terminal and the battery wire. The B2B will then work as designed. The split charge relay will close as before, routing the B2B power to the B2 terminal. So far so good.

2. When the engine is not running, the DS300 uses the B1 terminal for various functions, like measuring starter battery voltage and charging the starter battery. With the B2B in the way, there is no path for these functions.

The solution is to wire a relay that shorts across the B2B when the engine is stopped, but opens when the engine is running. Connect a relay using the 'Normally Closed' contacts, with its coil wired to the D+ (engine running) signal. This will bypass the B2B when the engine is not running. This is the method recommended by Schaudt for their WA1215 Booster, which is their version of a B2B.

Alternatively, if you can find a way to disable the split charge relay, you can connect the B2B to the B1 and B2 terminals and everything will work fine. If there's no designed-in method like a circuit-board jumper that you can remove, then maybe you can find a bodge that will disable the relay. Cutting that resistor r37 is just one of the possible ways. Maybe there's other circuit-board components that will do the job. Or you could remove the relay completely. Anyone who can repair a failed relay on a circuit board can remove the relay and not install a new one.

 

[Bore1]

Thanks for great answers guys. Iys fun learning about this, but i am a bit frustrated that its so many "unknown"variables in this kind of system. It would be cool to have both b2b and the ds300 to work together, but i see that "the loop" could make it innefficiant, and maybe damage battery over time. I have bought a battery monitor, so if i got the spirit over me i will make some tests with it and post my results here.

 

[Bore1]

I put together a wiring diagram here of how i think i will wire it. What do you think?
Feel free to destroy it completely

 

[Pausim]

I put together a wiring diagram here of how i think i will wire it. What do you think?
Feel free to destroy it completely

It looks ok to me. Very similar to how I set my system up, though I do not have solar.

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[autorouter]

I think the positive B2B Out should go to the +B1 terminal of the DS300 (not +B2). Apart from that it looks OK. The Bypass (NC) Relay also goes to +B1, so that is correct.

The +B2 and +B1 terminals are connected together by the Split Charge Relay when the engine starts.

Also when the engine starts, the Bypass (NC) Relay opens, so that power flows from the start battery through the B2B to the +B1 terminal.

 

[Pausim]

I think the positive B2B Out should go to the +B1 terminal of the DS300 (not +B2). Apart from that it looks OK. The Bypass (NC) Relay also goes to +B1, so that is correct.

The +B2 and +B1 terminals are connected together by the Split Charge Relay when the engine starts.

Also when the engine starts, the Bypass (NC) Relay opens, so that power flows from the start battery through the B2B to the +B1 terminal.

By going directly to B2 (or the leisure battery itself) the heavy charging current does not have to go through the CBE board and components. This saves stressing components and possibly reduces the voltage drop a little too.

 

[autorouter]

By going directly to B2 (or the leisure battery itself) the heavy charging current does not have to go through the CBE board and components. This saves stressing components and possibly reduces the voltage drop a little too.

If the DS300 doesn't measure the charging current as it goes theough the split charge relay, that makes sense.

 

[Pausim]

If the DS300 doesn't measure the charging current as it goes theough the split charge relay, that makes sense.

My panel and DS300 don’t measure current. There may be some variations that do.

 

[Bore1]

I was thinking not go trough the splitrelay to take the shortest route. Could it be ok to skip the negative straight to startbattery and just connect to the negative on the ds300? or is it imøportant that it goes directly to the battery as the positive? Its not easy to pull a cable trough the car.

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[ManTheVan]

It depends whether the negative on the DS300 is a big enough gauge wire, or you will just be limited to whatever it can take.

When I installed my Sterling B2B I ran two new cables of the gauge recommended by Sterling so I knew the current would not be limited.

@Pausim‘s reasoning and helpful circuit diagram in the thread he had linked was really really helpful. I bought a Durite NC relay from 12v planet which did the job perfectly.

 

[JockandRita]

When I installed my Sterling B2B I ran two new cables of the gauge recommended by Sterling so I knew the current would not be limited.

As did I.
The only cables/wiring which aren't of a substantial gauge to our Sterling 1260 B2B, are those for the temperature sensor, and the D+ signal from the alternator.

Cheers,

Jock.

 

[autorouter]

I was thinking not go trough the splitrelay to take the shortest route. Could it be ok to skip the negative straight to startbattery and just connect to the negative on the ds300? or is it imøportant that it goes directly to the battery as the positive? Its not easy to pull a cable trough the car.

Is far as I know the negative from the leisure battery and the negative of the starter battery are both connected to the chassis. The main negative current flows through the chassis. I think that the negative wire(s) to the B2B are simply to provide a low-power negative for the inbuilt circuitry. I also think the negative to the DS300 doesn't carry a large current, but just the current required for the circuits on the DS300 to function. I can't see a good reason to install an extra negative cable to match the positive cable in size, to either the leisure or starter batteries. It won't do any harm, of course, but I don't think it's absolutely necessary.

I'd say you could connect the B2B negatives to the DS300 negative if that was more convenient.

 

[Bore1]

Is far as I know the negative from the leisure battery and the negative of the starter battery are both connected to the chassis. The main negative current flows through the chassis. I think that the negative wire(s) to the B2B are simply to provide a low-power negative for the inbuilt circuitry. I also think the negative to the DS300 doesn't carry a large current, but just the current required for the circuits on the DS300 to function. I can't see a good reason to install an extra negative cable to match the positive cable in size, to either the leisure or starter batteries. It won't do any harm, of course, but I don't think it's absolutely necessary.

I'd say you could connect the B2B negatives to the DS300 negative if that was more convenient.

I agree with you Autorouter. By my knowledge of standard 12v without the witchcraft of lithium and b2b, it should make no difference

 

[ManTheVan]

I agree with you Autorouter. By my knowledge of standard 12v without the witchcraft of lithium and b2b, it should make no difference

...except if the negative strap from the DS300 is only designed to carry relatively low currents. It MIGHT work, but you might also halve your charge rate. It will charge, but sooo much more slowly.

We ran the dedicated new cables under the van in flexible ducting. It really was not a major job and ensured that our B2B can work as intended. You will probably find that suitable entrance/exit holes already exist. If not, then a small hole can be drilled and fitted with a grommet.

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[Bore1]

Hey. I have started the B2B installation, and i have a quick question. When is the the lithium empty and full?
If i set the batterymonitor to a 100Ah lithium, It will be very important that the voltage minimum and maximum is correct right?

The BMS on the 100Ah lithium has cut out on 10V and 14.6V,
If i set the batterymonitor to empty at 11.5V and full at 14.2V as recommended by Victron, and 100Ah capacity, would that mean that the Batterymontor think i have 100Ah, but in reality i have less because i havent maxed out BMS on the battery?

 

[Pausim]

I would use the BMV suggested Li figures and the stated 100Ah. When it reaches the voltage and the amps drop below the set level the BMV should auto synchronise, re-setting the battery to full. It will then start to count the Ah used since last full.

 

[andy63]

If i set the batterymonitor to empty at 11.5V and full at 14.2V as recommended by Victron, and 100Ah capacity, would that mean that the Batterymontor think i have 100Ah, but in reality i have less because i havent maxed out BMS on the battery?

Hi..i would say thats exactly the case..if the charge terminates at 14.2 v the battery isn't at total possible capacity and likewise on the discharge side..
But I suspect victron err on the side of caution..
At the end of the day the battery manufacturer will have a published spec sheet for your particular battery..it should say what the charge current should terminate at when the cells are full..and the cell voltage at that point
I also suspect that all battery monitors that give a capacity left etc can be taken with a pinch of salt.. it is after all not an exact science or didnt appear that way with lead acid..and I suspect lithium will be the same..just their best guess at putting an algorithm together..
Andy..

 

[Pausim]

I set my battery voltage too high at 14.6V (lithium) and the BMV often failed to synchronise automatically, though it is easy enough to do it manually on the app. I think this was because my charger, B2B and Efoy were shutting the charge off before it synchronised. However if you set the voltage and tail current a bit lower it may synchronise a little early but the charger will continue to charge until the battery is full and the reading will remain at 100% until current starts to flow out instead of in.

 

[Adriaadventure]

I don't know what functions are provided by a DS300 but if it has a split charge relay it could be passing up to 50amps ( depending on thickness of wire in the circuit between leisure and engine battery ) if the leisure battery is well discharged when the engine starts running. I would also think if the DS300 has a mains charger inside it could charge the leisure battery at up to 18amps and also a function to keep the engine battery topped up when on EHU.

I recently fitted a Votronic B2B ( 30A model ) and also a larger 160ah Advanced Lead Carbon ( AGM technolgy) leisure battery which needs the charge voltage to reach a minimum 14.7v for a period of time and a suitable charging profile for this type of battery. I have to say its a great improvement over the simple split-charge-relay system in terms of much faster charging and also a limit of 30A charging current so it cannot overload the NE237's internal circuitry or 70a inbuilt split charge relay, even if the leisure battery is in a low state of charge.

My Adria power supply is a Nordeletronica NE237 unit and when the B2B is fitted in series with the engine battery feed you loose the ability to charge the engine battery from EHU and also because the solar regulator is connected via the NE237 for current and voltage measurements the ability for the solar to charge the cab battery is lost also as you cannot feed current backwards through a B2B unit.
In addition to this voltage measurement of the cab battery voltage is also lost.
Fortunately the votronic B2B senses the leisure battery voltage going above a certain higher voltage, being charged by solar power or ehu for example and can apply a charging 'bridge' automatically to back-feed up to 1A max to trickle charge the cab battery. Not really shure this is adequate as the cab battery voltage seems to fall day on day down to 12.6v as the MH is parked up with just a little solar some days.

.Looking at the option of a high current relay suggested in this thread to short-out the input and output of the B2B when engine is not running would seem to be an ideal solution to the limitations caused by using a B2B with the NE237 power supply. Just wonder if shorting out the the input and output +ve's of the 'running' B2B immediately the engine stops will cause it any harm ??

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