What is the real battery charge? control panel vs multi meter... (1 Viewer)

[BVan]

Hello,
So we are fairly new to motorhome with only 2 months full timing in our 2003 CI riviera 181 over cab. We can't believe how much maintenance we had to do on our beloved home on wheels since we started... tbh we did change quite a few things which it seems they are not created for! (we did spend the last 6y successfully renovating our brick and mortar house, learning everything from scratch and doing pretty weel... our experience in the moho has proven more challenging so far!)
So today's issue comes from the battery charge which has been very low if we trust the control panel's reading (right now 11.1v) but when measuring at the batteries with a multimeter it shows 12.6v. When turning the engine on, multimeter shows 14v (which should be right, shouldn't it?) but control panel says 12.4v. On the other hand our dometic cfx 40 has turned itself off as it shows 10.8v (it is at the back of the van on 6mm² but still there must be a loss I imagine?) Anyway, question is are we killing our batteries right now? Debating heading to campsite asap or spending another night wildcamping...
I hope I am making a little bit of sense...
Thanks in advance for your help!
Cyrielle

 

[pappajohn]

The panel, depending what kind it is, may need calibrating to the battery.
Never had one of the electronic multi function panels so no idea how they work.

I would be the inclned to completely ignore the panel and believe in the multimeter.

 

[BVan]

Thanks papa John. I will try and borrow another meter to double check (mine being a basic one). The user book for the panel doesn't mention calibrating... I will look into it but if you have more information, I will be very grateful!
Cheers

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[BVan]

Sorry i forgot panel is a nc101c nordelettronica installed by CI. And next is a black battery display fox d1. All installed before we purchased the van so no idea on wiring... Our dometic was installed by us straight from the batteries with 10m of 6mm2 wires.

 

[bigtwin]

I suspect that the Fox unit is associated with a solar panel. Do you have one?

In any case, the Fox will be showing you the leisure battery voltage and, if the sun is shining, will be showing in excess of 13 V.

Ian

 

[autorouter]

I would be the inclned to completely ignore the panel and believe in the multimeter.

Agreed

I will try and borrow another meter to double check (mine being a basic one).

I'd be surprised if it's very much wrong, even if it's a basic meter.

First, when you say 'the batteries' do I take it you refer to the leisure batteries not the starter (cab) battery.

6 mm2 wire drops about 3 millivolts per metre per amp. So for the CFX40, consuming 7 amps, with 5 metres of wire, there and back, the voltage drop would be 3 x 7 x 10 = 210 millivolts, ie 0.21 volts. But you are actually losing between 1 and 2 volts, so the wire is not the problem.

If the system usually works but has developed a problem, suspect the connections. If you've never actually seen it working properly, or it's been modified recently, then also suspect incorrect wiring.

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[Mr Chrysalis]

I would also trust a multimeter, or use it to calibrate your inbuilt voltmeter.

 

[Minxy]

Others may not realise that the Dometic cfx 40 is actually a coolbox ... the consumption is: (DC@5/32°C) 0.665 kWh/24h, whether this makes a difference I don't know bit thought I'd point it out.

I've just done a quick power draw check and if my calcs are correct the CFX is drawing up to 55 amps per 24 hour period! I wonder if it has pretty much fried the batteries and the readings on the multimeter are just the initial level of charge which drops as soon as the CFX fires up?

Electrics aren't my strong point though!

 

[autorouter]

Others may not realise that the Dometic cfx 40 is actually a coolbox ... the consumption is: (DC@5/32°C) 0.665 kWh/24h, whether this makes a difference I don't know bit thought I'd point it out.

I think it's compressor cooled.The compressor switches on and off as required. When it's on, it takes 7 amps.

When working out the voltage drop, the ON current is what matters.

I've just done a quick power draw check and if my calcs are correct the CFX is drawing up to 55 amps per 24 hour period!

Correct. The average energy consumption over a day accounts for the compressor being off for a lot of the time, as you might expect. As you say, 0.665 kWh per day is 665/12 = 55.4 amp-hours per day from a 12 volt battery. But at least that's better than 7 x 24 = 168 amp-hours if the compressor was on 100% of the time.

You don't say what capacity (amp-hours or kilowatt-hours) your batteries are, but they'd have to be pretty hefty to cope with that. For example, two 100Ah batteries would be down from completely full to just less than 50% in 48 hours.

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[charlieisleofwight]

Hi Bvan,
On a different note, please can you tell me how to turn the awning light on on your MH. i have a 2003 181 garage and cant find the switch.
thanks

 

[pappajohn]

Hi Bvan,
On a different note, please can you tell me how to turn the awning light on on your MH. i have a 2003 181 garage and cant find the switch.
thanks

Bvan won't be able to reply as they are no longer able to post.
Maybe start a new thread under the motorhome chat forum.

 

[Minxy]

Hi Bvan,
On a different note, please can you tell me how to turn the awning light on on your MH. i have a 2003 181 garage and cant find the switch.
thanks

As PPJ has said BVan won't be able to answer now as he's used up his 5 free posts and won't be able to do so unless he becomes a full member (£15 a year), however someone else hopefully will be able to answer you (note you've only got 2 free posts left).

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[maxi77]

Others may not realise that the Dometic cfx 40 is actually a coolbox ... the consumption is: (DC@5/32°C) 0.665 kWh/24h, whether this makes a difference I don't know bit thought I'd point it out.

I've just done a quick power draw check and if my calcs are correct the CFX is drawing up to 55 amps per 24 hour period! I wonder if it has pretty much fried the batteries and the readings on the multimeter are just the initial level of charge which drops as soon as the CFX fires up?

Electrics aren't my strong point though!

The CFX 40 is a fridge or freezer and does have a compressor. The current draw is 6-7 amps but the duty cycle as a fridge is around 30% or better under normal circumstances. Adding external insulation can improve the duty cycle. They also run on 240 volts when an EHU is available.