Victron B2B only pulling 200w when driving

[Ads86]

So when we were on idle this morning we were pulling in around 400-450w from the B2B charger, however when driving now at a steady 2000rpm we appear to only be drawing max 200w, more like 90w from the B2B.

Does this sound like an alternator or battery issue? I'm not sure which to look at when I get home to the UK.

Full victron system with 608ah fogstar battery.

 

[autorouter]

A bit more info needed. Which Victron B2B?

Is it possible that the battery is actually full? That State of charge value is a calculated value, not measured. The shunt needs to be told when the battery is in the 100% charged state, and also the Ah capacity of the battery. It can then calculate the new state of charge based on those values, by measuring and timing the in and out amps. But if those original two values are not correct, the State of Charge display will not be accurate.

The shunt has an algorithm that has a jolly good guess as to when the battery is at 100%. This works fine if it's a mains charger, that is on continuously for hours. It works less well for a B2B, which starts and stops a lot more often.

 

[mikash]

Is the B2B in agreement with the shunt?

 

[AdrianChen]

While you were driving was the fridge on 12v? The shunt will see the net charge going into the battery, so for eg. if it were a Victron Orion 12/12/30, and the fridge was using 17amps the shunt wouldn't see more than 12amps going to the battery. If it were that model, then it would probably get hot and reduce its output to around say 24amps, in which case the battery might see 7amps net.

If the fridge wasn't on, then I'd look at the cable connections etc, taking into account autorouter comments

 

[Hoovie]

While you were driving was the fridge on 12v? The shunt will see the net charge going into the battery, so for eg. if it were a Victron Orion 12/12/30, and the fridge was using 17amps the shunt wouldn't see more than 12amps going to the battery. If it were that model, then it would probably get hot and reduce its output to around say 24amps, in which case the battery might see 7amps net.

If the fridge wasn't on, then I'd look at the cable connections etc, taking into account autorouter comments

This is a good catch BUT ... it would depend on if the fridge is on the B2B output - in which case a lot of the output of the B2B would indeed go to the fridge, but if it was on a direct connection (via relay) from the starter battery (like my Autotrail, for example), then the whole or at least great majority of the B2B output will go to the battery.

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[Barti Ddu]

This is a good catch BUT ... it would depend on if the fridge is on the B2B output - in which case a lot of the output of the B2B would indeed go to the fridge, but if it was on a direct connection (via relay) from the starter battery (like my Autotrail, for example), then the whole or at least great majority of the B2B output will go to the battery.

Yes. Our Autotrail PVC has the fridge directly connected to the starter battery. All of the output of our B2B therefore goes to charge the lithium leisure battery with nothing diverted elsewhere.

 

[Lenny HB]

If your Carthago has a smart ternator and the B2B is a factory fit the B2B will be supplying the fridge so that will account for 15amps.

If not a factory fit, another recent thread with a similar problem.
It turned out that the neg of the B2B was connected to the chassis reconnecting it to the negative bus bar cured the problem.

 

[DuncT]

Yep. I had a similar problem and it ended up being how the neutral was/wasn't routed. I'd overlooked this and the neutral was eventually connected to the chassis but through much narrower cable.

Connecting the leisure battery to the same neutral/earth as the b2b instantly sorted it

 

[AdrianChen]

If your Carthago has a smart ternator and the B2B is a factory fit the B2B will be supplying the fridge so that will account for 15amps.

If not a factory fit, another recent thread with a similar problem.
It turned out that the neg of the B2B was connected to the chassis reconnecting it to the negative bus bar cured the problem.

Yes our previous E Line was wired like that, the S Plus thankfully has a non smart alt.....

 

[rod_vw]

Yep. I had a similar problem and it ended up being how the neutral was/wasn't routed. I'd overlooked this and the neutral was eventually connected to the chassis but through much narrower cable.

Connecting the leisure battery to the same neutral/earth as the b2b instantly sorted it

We don't have a 'neutral' in 12v DC circuitry, it's -ve, earth or chassis ground depending whose language you are speaking. May even be terminal 31 in DIN automotive language.
By the way, if the vehicle has a battery monitor module on the engine battery -ve terminal than NOTHING else should be connected the -ve terminal.

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[Lenny HB]

By the way, if the vehicle has a battery monitor module on the engine battery -ve terminal than NOTHING else should be connected the -ve terminal.

My Ducato battery negative has the shunt that connects to the alternator and a braided earth to chassis.

 

[autorouter]

My Ducato battery negative has the shunt that connects to the alternator and a braided earth to chassis.

Presumably that means it's only measuring the alternator amps output into the battery. So it's not a proper battery monitor, measuring everything into and out of the battery. Anything that doesn't go through the shunt doesn't get measured.

It's not usual to have an actual battery monitor shunt on the starter battery, because it would need to measure the huge starter motor amps (several hundred amps) and still be sensitive enough to measure small drain currents like an alarm and tracker. Usually with it being a lead-acid battery they just measure the voltage to work out the state of charge.

 

[Lenny HB]

Presumably that means it's only measuring the alternator amps output into the battery. So it's not a proper battery monitor, measuring everything into and out of the battery. Anything that doesn't go through the shunt doesn't get measured.

It's not usual to have an actual battery monitor shunt on the starter battery, because it would need to measure the huge starter motor amps (several hundred amps) and still be sensitive enough to measure small drain currents like an alarm and tracker. Usually with it being a lead-acid battery they just measure the voltage to work out the state of charge.

What is surprising is the earth braid to chaiss which I assume is the main earth, is a clip on connection (from memory I think it is a push button on top to release it) you can swivel it fairly easily on the battery post and there is no way of tightening it.

 

[rod_vw]

Presumably that means it's only measuring the alternator amps output into the battery. So it's not a proper battery monitor, measuring everything into and out of the battery. Anything that doesn't go through the shunt doesn't get measured.

It's not usual to have an actual battery monitor shunt on the starter battery, because it would need to measure the huge starter motor amps (several hundred amps) and still be sensitive enough to measure small drain currents like an alarm and tracker. Usually with it being a lead-acid battery they just measure the voltage to work out the state of charge.

Yes it is normal on modern vehicles with smart alternators to have ALL current entering or leaving the battery monitored by the battery monitor module (shunt). That is how the system knows how to control the smart alternator, if the battery monitor module is bypassed in any way the alternator control is unable to charge the battery to a level leaving headroom for regenerative braking etc. All down to the manufacturers efforts to reduce pollution.

Here is an example of the actual battery connections where you will see that the battery monitor control unit is integral with the earth lead and clamp. That diagram is from a factory workshop manual.

 

[Ads86]

Sorry for the late reply, I'm in Calais and I've run out of data and can't get the camper car WiFi to work.

It seems it was my dometic fridge that was drawing all the amps away from the lithium as people have suggested.

When I travelled in the van with the fridge on gas instead of 12v it was inputting the below which feels about right for a 50amp victron B2B. It did go upto around 575w when the solar kicked in.

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[Lenny HB]

That is a bit low you should be getting nearly 50 amps plus whatever the solar is delivering.
My XS runs at around 48 to 49.5 amps.

You should not drive with the fridge on gas, against construction & use regs.

 

[Ads86]

My vans 2011 so I wonder if the alternator isn't up to the job. Everything seems to be wired correctly

 

[AdrianChen]

Not sure how your E Line is wired up, but I guess originally it may well have been a split charge relay and no B2B, so possibly the Orion has been added recently. If so it would be worth checking the SCR has either been disabled in the CBE DS470 (by snipping a resistor R28) or the SCR has been circumvented by installing a relay. If neither has been done, the output of the Orion XS may be being compromised by the SCR.

Also worth having a look at the alternator label to check the power rating, but even if a lower output (140amp), you should still see getting on for 50amps at least while the van isn't using headlamps, wipers radio etc.

Lastly I would check the cable sizes and connections - if the original 16mm² cable has been used for the B2B, that might be causing a bit of voltage drop, if like mine the B2B is in the garage, and the cable runs the length of the van.

 

[Lenny HB]

My vans 2011 so I wonder if the alternator isn't up to the job. Everything seems to be wired correctly

I expect it to be at least 160 amps.
As Adrian says split charge relay probably hasn't been disabled so it will effectively bypass the B2B.

 

[Ads86]

I doubt my install guy has taken this into account.

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