CBE Panel Battery Load Amperage

[Dave100456]

Hi
Still getting to know my new to me 2017 M/H. Can someone please enlighten me?

I have a CBE display panel (its very similar to a PC180).
On EHU, when I select the battery display I see the engine and habitation battery voltages as well as the current in amps going into or out of the habitation battery - The display shows the (volt and amps) battery charger going through the bulk, absorption and float stages - all good.

The batteries go to float voltage after the expected time yet the thing that puzzles me is that the habitation battery amp reading is always showing a 4.8 amp load. It doesn't seem to matter what consumers I activate; fan blower, water pump etc, the amps reading will only vary by 0.1 or 0.2 amps and always shows a 4+ amp drain. I have looked at the "offset" feature (and previously used this to correct the voltage readings) but the amps offset can only be varied by a couple of amps and thus can't be brought to zero.

Surely when the batts are on float, the battery charger will supply the necessary current for any consumer thats called upon and the amperage readout of habitation battery on the display should be around 0 amps?

Thanks

Dave

 

[Richard n Ann]

Check it with a clamp meter if you can, otherwise you can pull the 12v fuses 1 by 1 to see if any stop the drain.

 

[Pausim]

It seems to me that something is bypassing the shunt. Has someone put a negative connection directly to the battery?

 

[Dave100456]

It seems to me that something is bypassing the shunt. Has someone put a negative connection directly to the battery?

The van is as standard from Frankia. There is only one +ve and -ve connection from the battery to the 12v distribution box. I've not located the shunt and would have thought that it would be placed between the battery and the 12v distribution box before where the 230v/12v charger supply is connected.

 

[ManTheVan]

Ours does the same thing, but when you switch on the master it shows 2.5A generally, increasing or decreasing as you activate various circuits. There just seems to be a draw by the panel itself, maybe.

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[Dave100456]

Ours does the same thing, but when you switch on the master it shows 2.5A generally, increasing or decreasing as you activate various circuits. There just seems to be a draw by the panel itself, maybe.

Thanks for that. I've noticed that the panel always indicates a 2.6 amp flow out from the battery unless the EHU/battery charger has just been connected when the panel shows a "high" amperage going to the battery.
Perhaps its just the way these things are wired but it seems odd to me.

2.6 amps constant drain seems high to me, with a PCB panel, however, i suppose there are a few consumers connected even when everything is switched off. Thinking about it, the previous owner had a tracker fitted. As these are personal to the initial buyer, I couldn't take it over and don't know where it is and also whether its consuming power; anyone help with that one?

 

[Richard n Ann]

2.5 amps would do my head in to the extent of stripping the van into a thousand pieces until I found the problem but that's just me. Our van uses 0.2 amps and that's bad enough, if I switch the main switch off it drops to 2ma (yes I did measure it when the van was new)

Our tracker pulses at about 80ma when transmitting to the mobile network and about 35ma on standby

 

[autorouter]

Check it with a clamp meter if you can,

Another vote for that. You need to know if the 4.8amps reading represents a real current into/out of the battery, or not.

Amps are measured using a shunt resistor in the main current path, usually in the battery negative wire. A very small voltage drop, typically only a few millivolts, is measured using a precision operational amplifier. It doesn't take much to throw this reading off, so there could easily be a fault producing a few extra millivolts that gives a false reading.

A clamp meter will read the current without having to undo any connections. It just clips round the wire and senses the magnetic field generated by the current.

Edit:

There is only one +ve and -ve connection from the battery to the 12v distribution box. I've not located the shunt

The shunt is probably inside the distribution box.

 

[Dave100456]

My DC clamp meter is many miles away from me so can't use that. My multimeter measures up to 10amp which I can put into the battery circuit but to do this I'd need to disconnect the battery temporarily.

Am I correct to presume disconnecting the batt won't loose any settings from the CBE panel other than those that are "user programmed"??

 

[Pausim]

My CBE panel gets isolated by a master switch on the battery whenever I leave the motorhome in storage. The Carthago instructions suggest this. No problems so far.

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[autorouter]

If you can get at the master switch or isolator fuse, you don't actually have to disconnect the battery. For example, set the meter to amps, put the probes on the the switch terminals, and with your third hand turn off the isolator switch. All the current will flow through the meter instead of the switch. When you've got the reading, turn the switch back on before removing the probes.

 

[Dave100456]

So these are the readings at the battery:
CBE panel switched off: battery current draw pulses between 0.03 and 0.08 amp; presume this is the tracker and this current draw is acceptable.
CBE panel switched on: battery current draw 0.18 and 0.23 amp, also acceptable.

All the above amperage readings were taken on my multimeter. However, on the CBE panel the display shows a 2.8 amp draw.

The CBE settings can be adjusted using the amps offset and mine has a range of -2.8 to -8.8. It should be reading same as my multimeter. I have it set the offset to the lowest -2.8amp and I can't adjust it any lower.

Anyone any ideas if I've missed something?

Thannsk

 

[Pausim]

As suggested earlier it looks like the shunt is at fault. Probably easier to buy a a good battery monitor like the Victron ones than try to fix something built into the distribution unit.

 

[Dave100456]

I've traced the battery +ve cable and I don't think I have a shunt. I think the measurement is done on the CBE fuse distribution box PCB.

 

[Pausim]

I don’t think you can measure amps without a shunt, so as said it is probably built into the distribution box.

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[autorouter]

A shunt is simply a very low value precision resistance. All the amps are channelled through it. An accurate millivoltmeter measures the tiny voltage drop across it. In theory it can be located anywhere in the circuit. Adding a battery monitor, it's easier to put the shunt in the battery negative cable. However inside Elektroblocks the shunt is in the positive feed to the leisure battery, and I would imagine something similar in the CBE box.

 

[autorouter]

If you're thinking of adding a battery monitor, and you're happy with a phone app instead of a display panel, then you could look at a Victron SmartShunt. It is fitted in the negative cable near the battery, and communicates by Bluetooth to a phone app. Saves all that routing of wires and cutting holes for the display.

 

[Dave100456]

Thanks for the replies.
Im not too bothered about knowing every minute what the net current flow is as I know the wattage of each consumer.
Also, the CBE display appears to read amps “correctly” albeit 2.8A too low and I could just add 2.8amps to it’s value. However, being a bit anal I’d like it to read correctly and know exactly what’s going wrong.
I’ll contact CBE if this forum doesn’t produce an answer.
Thanks

 

[Dave100456]

If you're thinking of adding a battery monitor, and you're happy with a phone app instead of a display panel, then you could look at a Victron SmartShunt. It is fitted in the negative cable near the battery, and communicates by Bluetooth to a phone app. Saves all that routing of wires and cutting holes for the display.

Victron smart shunt looks good and I have Victron kit (solar controllers & Quattro) elsewhere its good kit but at over £100 it’s a lot to pay for something I should already have.

 

[Richard n Ann]

Is it reading OK now you've set the calibration setting to minus 2.8?

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[Dave100456]

Is it reading OK now you've set the calibration setting to minus 2.8?

No. I had already set the offset to as "low" a value as possible ie 2.8. If I set it to a higher value of offset, the display error is even worse.

Something can't be right because you'd have thought that the offset could be altered + or - to attune the display to the measured amps. With mine I can only change it - 2.8 down as far as -8.8.

The CBE manual is not great and I think Im doing it correctly as I made the same adjustment to the voltage offset for the engine and habitation batts. I only needed to move these values a few tenths of a volt to get the displayed value to match what my accurate meter showed.

 

[autorouter]

From your description I'd bet it's an actual fault, either a bad contact near the shunt or a fault in the operational amplifier circuits that read the voltage. You expect a bit of calibration drift, and there's an adjustment to compensate for this, as you said. But this is way beyond a bit of an imbalance. If you get no sense from CBE, try Apuljack Engineering, they show CBE units in their list of repairable units.

 

[stevewagner]

Thanks for that. I've noticed that the panel always indicates a 2.6 amp flow out from the battery unless the EHU/battery charger has just been connected when the panel shows a "high" amperage going to the battery.
Perhaps its just the way these things are wired but it seems odd to me.

2.6 amps constant drain seems high to me, with a PCB panel, however, i suppose there are a few consumers connected even when everything is switched off. Thinking about it, the previous owner had a tracker fitted. As these are personal to the initial buyer, I couldn't take it over and don't know where it is and also whether its consuming power; anyone help with that one?

Trackers are normally connected to the cab battery

 

[Dave100456]

From your description I'd bet it's an actual fault, either a bad contact near the shunt or a fault in the operational amplifier circuits that read the voltage. You expect a bit of calibration drift, and there's an adjustment to compensate for this, as you said. But this is way beyond a bit of an imbalance. If you get no sense from CBE, try Apuljack Engineering, they show CBE units in their list of repairable units.

Thank you. Will give them a try.

 

[Dave100456]

Trackers are normally connected to the cab battery

Good point. The 0.05amp pulse must be from something else and its so small it's of little significance.

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[Dave100456]

Thank you. Will give them a try.

Thank you for this recommendation.

I've just spoke with them and they were most helpful and knowledgeable. The chap there confirmed that there's no shunt on my setup and all the measuring of amps is done via components on the PCB of the fuse distribution box.

 

[ManTheVan]

Does that make the measurement more, or less accurate?

 

[autorouter]

I take that to mean there is no separate shunt device inside the CBE box, but the components and functionality of a shunt are integrated into the main Printed Circuit Board (PCB)

 

[Dave100456]

Does that make the measurement more, or less accurate?

I'd have thought that with both shunt and PCB component measuring of current, they could be equally accurate.

 

[Dave100456]

I take that to mean there is no separate shunt device inside the CBE box, but the components and functionality of a shunt are integrated into the main Printed Circuit Board (PCB)

Yes; I understood him to say that there is no shunt at all and current is measured by components in the PCB of the fuse/distribution box.

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