Pointless Electrical Consumption

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crinklystarfish
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Pointless Electrical Consumption

Postby crinklystarfish » Fri Jul 07, 2017 7:17 am

Whilst on with pondering my original electrical installation and doing the recent manual relay over-ride conversion, I measured the consumption of a few other bits of hardware when in standby state.

All @24V:
40A relay = 85mA
60A relay = 165mA
18A DC-DC Converter = 280mA
1800W Inverter = 330mA.

Leaving this combination of items on standby was something that we sometimes did when out and about and it came as something of a surprise to realise that to do so was 'costing' us 860mA an hour.

As before, we're normally parked up for about 17hrs per overnighting spot so were effectively giving away 14.62A. One 24hr period would equate to the consumption of 20.64A - and all this without actually using any domestic equipment.

Put another way, these losses might otherwise run the compressor fridge on a low setting and in moderate ambient temperature. Proper shocker.

I'm glad I did the measurements. Manufacturers tend to underplay standby / quiescent loads and I confess I had - until recently - pretty much just shrugged it off.

Again, my electrical installation is comparatively simple and doesn't include that much hardware.

I'd urge everyone - who hasn't already - to reduce / eradicate these pointless losses - battery performance / longevity can only be improved.

Incidentally, using extrapolated figures from real-world solar panel use, it would have taken an 80W solar panel from dawn till dusk on a sunny summer day just to offset the 20A loss that my 40A relay / 60A relay / DC-DC / converter / inverter combination would 'steal'.

:o

Mark Hadley
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Re: Pointless Electrical Consumption

Postby Mark Hadley » Fri Jul 07, 2017 7:34 am

I'm surprised by the DC - DC converter. The other are what I would expect. I have a switch on my invertor, which is normally off. An invertor is important for us but rarely used - just to recharge items that don't have a 12V or USB charger.

The relays will only draw power when they are on.

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christyler
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Re: Pointless Electrical Consumption

Postby christyler » Sat Jul 08, 2017 11:15 pm

all good points,

for the big relays you could use blue seas RBS type relays they are magnetically latched either on or off, and as such they do not draw any current when either off or on.
i have used there on all the main battery circuits, and they have the advantage of being remotely controlled.

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Re: Pointless Electrical Consumption

Postby crinklystarfish » Sun Jul 09, 2017 6:50 am

Good link Chris, when I was at the design-and-build stage I looked for heavy-duty DC latching relays to act as master-switches for my 24V and 12V circuits but didn't come across these.

I've now re-jiggled my automation so there's zero current draw unless and until we actually use an appliance / fixture.

I accept that with huge battery banks and big solar arrays (on sunny days) 'losing' 20A in 24hrs might not be critical but for our modest reserves it represented a huge chunk of our available capacity.

It bothered me that with our nominal 100Ah 24V capacity that - in reality - given with open lead acid batteries it's wise to avoid discharge to below 50%, plus there's no way that they'd ever reach 100% state-of-charge whilst on the road, that we probably only had a meaningful capacity of maybe 30-35Ah@24V at the best of times.

Don't get me wrong, because we travel every day (and we have an additional nominal 100Ah@12V) the system's worked well for us, but I should have paid more attention to the avoidable losses before now.

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Re: Pointless Electrical Consumption

Postby Mark Hadley » Mon Jul 10, 2017 2:54 pm

it makes sense to deal with it, every little helps. Looking at the two biggest culprits: can you simply add a switch to the circuit and switch them on when you want?

crinklystarfish
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Re: Pointless Electrical Consumption

Postby crinklystarfish » Mon Jul 10, 2017 5:20 pm

Could've done that Mark but a bit of a re-jiggle and converting the existing relays to incorporate a manual over-ride function cost me nothing and allowed me to retain all my original (OCD) wiring. I also quite like that I can still use the relays conventionally if I choose.

I was genuinely surprised by the extent of the cumulative standby and quiescent consumption and, as you say, it's well worth addressing - every bit helps with battery performance and ultimate longevity.

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NeilandPat
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Re: Pointless Electrical Consumption

Postby NeilandPat » Mon Jul 10, 2017 8:06 pm

I have often thought about this very subject, but then distracted by stacking the tins in my cupboard a bit straighter.

Only joking, love you guys

Good point made

Neil

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bromleyxphil
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Re: Pointless Electrical Consumption

Postby bromleyxphil » Tue Jul 11, 2017 7:39 am

I must admit I can go to bed with the system full and not use any power then the Solar is pumping a bit more in in the morning. I thought it was down to temperature difference at the batteries, or maybe that infernal chatter of the "taco". Do you all have a taco that rattles and ticks all the time? Is it worth trying to sort out?

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Re: Pointless Electrical Consumption

Postby crinklystarfish » Tue Jul 11, 2017 7:45 am

Phil, you're a 'motorcaravan' you can legally take it out.

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NeilandPat
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Re: Pointless Electrical Consumption

Postby NeilandPat » Tue Jul 11, 2017 8:28 am

Mine also rattles ( but not loud )

I think its part of the drivers time clock. I am sure that this element could be disabled leaving it as a simple Speedo.

I think the problem taking it out is that it leaves a big hole to fill .

A spanner in the works is worth a try

Neil


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