Typical current draw for 12 volt systems to aid planning of battery needs and future trips without EHU? (1 Viewer)

[PlacidoD]

I thought it best to start a separate thread on this for the benefit of relative newbies like myself.

I am after knowing typical current draw for "essential use" items when overnighting or indeed staying over 24 hours on a site without EHU (and assuming no engine use to top up leisure batteries)

Lighting - (In my case I can safely say no more than 40 watt per hour max as I am replacing bulbs with leds though I am left with some higher draw fitting that it is just not economic to replace in particular 5 light fittings in the loo! But plainly they have limited use)

Fridge - I expect this to be the heaviest draw

Water pump

TV should I choose to run it. - In my case an Avtex 23" Smart TV. I have an SatFi dome on the roof which I have yet to check out. It will be a bonus if it works!

Sundries - (12v circuits to Truma gas only heater/boiler, also 12 volt circuits to fridge if I choose to run on gas)

There will be some incidentals like electric door step

Have I missed anything?

I do have a small freestanding 150 watt inverter that would allow me to charge my Dell XPS13 notebook or my Ebike battery. Given that I can charge either via the cigar lighter socket in the cab I cannot see that being used more than one hour per day max.

It seems to me that if I run the fridge off gas (I have two 11kg SafeFill bottles) the draw should be very modest indeed unless using without EHU over winter months.

The figures will allow me to ensure I have enough "juice" for two nights without EHU and without engine running which is the maximum I foresee. It will also allow me to spot any excessive current draw via my newly ordered multi-meter indicating a problem.

Of course what those figures will not tell me is the speed with which the 240v charger or running the engine will replenish the leisure battery . I am about to fit a new leisure battery today and explore to find the charger which I suspect is in a panel behind the battery under my driver's seat! If that is a very slow charge that will indicate a need for more leisure battery capacity, restricting 12v use or upgrading the charger.

P.S. One day I might swap to LiPo but prices will need to come down before that will make sense to me (And I have some learning to do - At the moment my understanding of French, German and Italian far exceed my understanding of LiPo technology!!!)

Chris

 

[funflair]

Have you got a compressor fridge or a 3 way, as 3 way will/should be on gas when you are not driving.

EDIT sorry you confirmed that lower down

 

[funflair]

The bits that run very occasionally like step and even water pump don't make a huge dent in your battery capacity, the bit's that need more research would be the ones that run for longer periods, the easiest way really is a reliable ammeter or even better a battery monitor in the van as that takes away the guesswork, again re charging from battery or hook up a battery monitor will tell you what you are actually getting, a Victron SmartShunt would do the job without any additional wiring for an internal display as you can view everything on a smart phone (smart phone not included ) get back from a drive and the display will show you charge as a graph over a given period.

Just one screen shot from the shunt (you might not get 90 amps )

You don't mention solar, do you have any as that can cover a lot of your daily requirement.

 

[Spriddler]

Have I missed anything?

Do you have any solar panels?

 

[PlacidoD]

Yes. One solar panel of, I think, 150 watts but, sods law, my two days off EHU will be heavily overcast and pouring with rain hence not factoring it in.

P.S. Victron SmartShunt sounds interesting. But I can fit a 2nd battery for that price! However all new learning is useful! Thank you.

Chris

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[headlight]

PlacidoD If I remember correctly you have just bought an 85AH lead acid battery ?
If that is the case then with no charge input you have 42.5 amps of usable power.
Of course solar will add to that depending on weather.
Really you would have been better off working out your usage first then sizing your battery to suit.

 

[Richard n Ann]

Yes. One solar panel of, I think, 150 watts but, sods law, my two days off EHU will be heavily overcast and pouring with rain hence not factoring it in.

P.S. Victron SmartShunt sounds interesting. But I can fit a 2nd battery for that price! However all new learning is useful! Thank you.

Chris

My panel is 150w. Been very cloudy today in Louth and it was charging at 2.8 amps

 

[berni109]

But yourself a cheap battery monitor (BM2) and that will give you a voltage graph over time which should give you a good idea of your consumption. Then consult a table that shows voltage against state of battery charge. You should aim to keep battery above 50% state of charge.
Using more than 50% add a battery.
If you go lithium in the future you can get all the electrical gizmos and spend all of your time monitoring the state of the battery.

 

[68c]

Buy a clamp on multimeter, such as the Uni-T UT210E. Make sure it has a DC amp function. Easy to use, just clamp it on the negative lead from the leisure battery then turn on things on one at a time and note the readings.

 

[funflair]

Yes. One solar panel of, I think, 150 watts but, sods law, my two days off EHU will be heavily overcast and pouring with rain hence not factoring it in.

P.S. Victron SmartShunt sounds interesting. But I can fit a 2nd battery for that price! However all new learning is useful! Thank you.

Chris

Do the SmartShunt first and put the extra battery money towards Lithium

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[Boldly]

Buy a clamp on multimeter, such as the Uni-T UT210E. Make sure it has a DC amp function. Easy to use, just clamp it on the negative lead from the leisure battery then turn on things on one at a time and note the readings.

Why the negative lead?

 

[PlacidoD]

Buy a clamp on multimeter, such as the Uni-T UT210E. Make sure it has a DC amp function. Easy to use, just clamp it on the negative lead from the leisure battery then turn on things on one at a time and note the readings.

This arrived from Amazon this morning:

https://www.amazon.co.uk/gp/product/B00O1Q2HOQ/?tag=mhf04-21

New 95 Ah battery installed this evening plus lots of led bulbs to replace tungsten elements. I am leaving the driver's seat off overnight to check all is OK and then will take some readings tomorrow.

P.S. Hoping I can find an access point to get at the cables with the seat still mounted!! No way do I want to be demounting it to take readings with any regularity!

Chris

 

[Boldly]

I got one of them on the recommendation of other funsters from my daughters for father's day. The batteries that came with it are flat already

 

[Lenny HB]

I assume you have Truma Combi heater, although their power consumption is not that high it adds up if on morning & evening.

Our usage has been in summer around 20 to 30 ah a day, using heater for hot water in the morning, LED lights & fridge on gas.
Spring/autumn 50 to 60ah a day.

 

[oldiesontour]

Shunt type battery monitors with and without Bluetooth can be bought from AliExpress fron £15 obviously not the bells and whistles of a victron but they tell you what is going in and out and what is in the battery and don't have the added feature of emptying your wallet

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[Lenny HB]

Shunt type battery monitors with and without Bluetooth can be bought from AliExpress fron £15 obviously not the bells and whistles of a victron but they tell you what is going in and out and what is in the battery and don't have the added feature of emptying your wallet

They are very basic don't have anything like the features or setting of the Victron they will only give you a. Rough idea of battery state.

 

[ChrisL]

I use around 30ah a day but I have 250w of solar that pretty much covers all use during the day and still refills the battery by lunch time if it's sunny or the afternoon if it's overcast, yesterdays usage was 22ah despite watching tv most of the day and it raining torrents all morning. My current state of charge at 09:00 is 93%, and i've been off hookup for nearly two weeks.

 

[VXman]

I assume you have Truma Combi heater, although their power consumption is not that high it adds up if on morning & evening.

Our usage has been in summer around 20 to 30 ah a day, using heater for hot water in the morning, LED lights & fridge on gas.
Spring/autumn 50 to 60ah a day.

Presumably not using electric for heating the hot water? There will be some electric consumption involved in hot water heating but minimal if using gas. Most consumption will come from running the fan when using the heating.

To the OP - I would say the biggest draw on your list will be the TV and the heating in Spring/Autumn. I would expect 1 night to be fine - possibly 2. With good sun and economic use maybe 3.

 

[Speve]

Presumably not using electric for heating the hot water? There will be some electric consumption involved in hot water heating but minimal if using gas. Most consumption will come from funning the fan when using the heating.

To the OP - I would say the biggest draw on your list will be the TV and the heating in Spring/Autumn. I would expect 1 night to be fine - possibly 2. With good sun and economic use maybe 3.

He said it was a gas only boiler in his first post

 

[VXman]

He said it was a gas only boiler in his first post

I was responding to Lenny (not the OP) who said he was using his heater to heat hot water in the morning and referring to his electric use. I was just wanting to clarify what Lenny was using to heat his water.

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[Lenny HB]

I was responding to Lenny (not the OP) who said he was using his heater to heat hot water in the morning and referring to his electric use. I was just wanting to clarify what Lenny was using to heat his water.

Gas heating for hot water but as you say it still uses some electrical power.

 

[TheBig1]

In previous vans before we had solar panels, we could get 5 days use off grid from a 110ah battery. With solar it becomes possible to be able to cope indefinitely

 

[oldiesontour]

They are very basic don't have anything like the features or setting of the Victron they will only give you a. Rough idea of battery state.

Think that's what I said

 

[PlacidoD]

Thanks all for your input.

I think I should be reasonably safe for my 7/8 nights away later this month:

Night 1: 200 odd mile drive down to CAMC site at Mertsham just off M25 but arriving post 20:00 and will have to overnight in the overspill.
Night 2: On EHU at Mertsham
Day 3: Drive down to Newhaven for the 17:00 ferry. Arrive Dieppe and overnight at an Aire (Ideally the one round the corner and I assume no EHU (I can then walk or bike into Dieppe and do a food shop before moving on))
Night 4 & 5: On EHU at a site near Dieppe (La Source, Hautot-sur-Mer)
Night 5 & 6: On EHU at a site in Le Crotoy (Les Trois Sabliers)
Day 7: Back to Dieppe for 17:00 ferry back to UK. Unsure of plans on landing at Newhaven. I may press on home arriving circa 03:00 or maybe park up somewhere enroute for a few hours sleep.

Come the end of August I am back on the Newhaven-Dieppe ferry for a 15 day jaunt with my furthest destination being Colico, Lake Como. Again I am on the 17:00 ferry and so will overnight at an Aire on arrival but then heading for a site with EHU at Haguenau before communing with family near Zurich for a long weekend (on EHU while there) and then onto Colico. I cannot, of course pre-book the sosta there that I really want where I plan to spend 4 nights. There is a small risk that I will have to park up somewhere off grid for one or even two nights before returning for another family weekend and then retracing my steps for the midnight return ferry (Ugh!!!). I either need a back-up plan for a site somewhere other than Colico or a 2nd battery would be best advised.

I might be more adventurous off grid next year but I only took delivery of this van on 3rd May this year. So I am feeling my way still. And I still work fulltime albeit with generous holiday (and also have heavy singing commitments) so I am more inclined to spend on sites and EHU when I can get away.

Chris

 

[Dave and Jan]

Is there a simple way to understand leisure batteries. For example if you have a 100 ah battery would that equate to 100 hours at 1amp use, 20 hours at 5 amp use, 10 hours at 10 amp use? Does a 130ah give you 30 more hours at 1amp use than a 100ah? In short does the bigger ah battery give you more power or a longer period?

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[CleverTrevorUK]

I do a lot of music festivals during the year. At 99% of the events there are no EHU points. Music fests are very anti generators as am I. I have 6 batteries distributed around the camper and during the events they are charged using 2 x 100w solar panels and a large wind turbine which is fixed on an extending pole secured to the rear ladder. I suspect the 6 batteries could be reduced to 4 to minimise weight but hey ho I love the fact that when i need to use the inverter on those overcast days to charge my electric bike or run a microwave, i can! During the summer i wont even bother to use the hookup when home as the solar and wind keep the leisure and my engine battery fully charged! Happy to say the system keeps my night time festival illuminations (flag pole) and TV running without any sort of power outage. Allways happy when i wake up at 8 in the morning and see the batteries are showing a good 13.5 volt charge or sometimes 14volts!

 

[headlight]

Is there a simple way to understand leisure batteries. For example if you have a 100 ah battery would that equate to 100 hours at 1amp use, 20 hours at 5 amp use, 10 hours at 10 amp use? Does a 130ah give you 30 more hours at 1amp use than a 100ah? In short does the bigger ah battery give you more power or a longer period?

If the leisure battery is lead acid, as in the OP's case, then assuming the battery is new you have half the amps in usable power as lead acids shouldn't be taken below 50% SOC.
So a 100AH battery would give you 50 amps of usable power.

 

[Dave and Jan]

If the leisure battery is lead acid, as in the OP's case, then assuming the battery is new you have half the amps in usable power as lead acids shouldn't be taken below 50% SOC.
So a 100AH battery would give you 50 amps of usable power.

Thanks for that. I have a 100ah LA battery. It’s 4 year old but just been tested good this week as part of the Hab check. We are fortunate to have a Sargent panel that gives you battery readings, amp usage at the time and solar or EHU input. We do spend plenty of nights off grid. Never had a problem but never fully understood it. By the next morning having run everything including some tv, leisure battery will be down to 12.1-12.3v. Generally move again the next day so batteries get charged. Was thinking at some point will need to replace the battery and have looked at 130ah in the belief they would automatically have more power/ last longer?

 

[Folkranger]

If yours is like mine, try not to use the cab radio/speakers as this is one of the highest battery users in my van. I love my music and thought I could utilise the cab head unit amp and speakers for such as my music or to improve TV sound but actually I never use this now when stationary.

 

[headlight]

Thanks for that. I have a 100ah LA battery. It’s 4 year old but just been tested good this week as part of the Hab check. We are fortunate to have a Sargent panel that gives you battery readings, amp usage at the time and solar or EHU input. We do spend plenty of nights off grid. Never had a problem but never fully understood it. By the next morning having run everything including some tv, leisure battery will be down to 12.1-12.3v. Generally move again the next day so batteries get charged. Was thinking at some point will need to replace the battery and have looked at 130ah in the belief they would automatically have more power/ last longer?

A 130AH battery will give you 65amps usable power as opposed to 100AH giving you 50amps usable.
At 12.1v you're taking your battery down to below 50% SOC which is not recommended.
At 4 years old your 100AH battery is probably about 80AH due to degradation.
As regards a hab check pronouncing your battery as good I doubt very much.
All a hab test will do is check voltage not capacity.
They won't test capacity due to it taking to long to do.
Voltage of a leisure battery is not necessarily a good indicator of capacity.

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