Battery life question

[Surfer]

We have a 110 amp battery in good condition plus a 150w invertor. The TV is a 12v Kogan 15" screen so can plug directly into teh caravan system. Sky box is 240v and is the Amstrad Sky + digibox. Maximum wattage 42w. We have ALDE heating with a double door fridge.
If watching 6 hours Tv per day, how long will the battery last taking into consideration that ALDE heating requires the pump to be running which is one of the reasons why we dislike the ALDE heating system? I think the fridge also requries a 12v supply even though it is on gas. Thanks to any maths genius as I cannot seem to come up with the correct figures.
Cannot afford a solar panel yet so that is out of the question.

 

[NickinFrance]

I don't know how much you can take out of a 110 Ah battery before it becomes unusable but to give you a start:
The TV consumes 35W, so just under 3 A from the battery
At 42W, the Sky Box consumes 3.5 A at 12 V but as the inverter is only about 80% efficient, you would be taking 4.2 A from the battery
The Alde system consumes 0.6A on gas (http://www.alde.co.uk/itemdetails.php?itemId=1)
The fridge would only use a minimal amount for control & a few Watts for the light, so would discount that.
Which means that the TV & Sky box would use 39Ah in 6 hours & the heating 14.4Ah per day a total of 53 Ah so if (big if) you could get 110Ahr out of the battery, you would have 2 days.

 

[graham_somersham]

It depends a lot on the condition of your battery and how much charge it will take which may not be the same as when you purchased it. Additionally if you are charging it on the built in charger you are unlikely to get a full charge due to the nature of most inbuilt caravan chargers. I have a feeling that you TV and Sky boxes actually use less than you have quoted and that these figures are the maximum the devices would draw.

Given that the Alde pump does not run continuously and is very low consumption anyway I would not worry about it too much. I have done 8 nights off ectricity using a 110A battery without any probs. I managed to resist the temptation of the Murdoch empire. I still had enough power to use the motor mover to get caravan onto my driveway when I got home after a short journey.

 

[emmerson]

...........or leave the tv at home!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

[JTQ]

As a guide you "should" not usually take more than 50% out of your battery, and that only if it is a good quality one. Many are far from that!
Your Sky box is a killer with such a massive drain, compounded by requiring an inverter. Time to buy something like a 12 volt Comag unit taking 12 Watts; this will be a generic decoder so will get the normal TV channels but not Sky unique ones.
Your TV would take something like 25 Watts if designed for caravan use, probably more if it is a domestic market unit.
The Alde will take very little if not actually fired up; if fired up as said it will draw 0.6 amps with the burner on full belt; extra power is needed for the circulating pump and the amount varies greatly with the type fitted. Mine an inline is just under an amp; the in header type are reportedly far less. Clearly the total the heating takes is dependant on how long and at what output it needs to operate so weather and time of year are very important issues.
Without bothering to do anymore arithmetic i feel your 6 hours of TV, plus some lights is but a dream for more than a winters night without addressing the excessive drains or aspirations.
You could simply pull out the EHU cable and try things before venturing off EHU properly but you are set for dissapointment.

 

[Gafferbill]

.........get more batteries

I have 70Ah I can drain from the tow car battery as it is 180Ah and 110Ah is enough to start the engine.
I have a further 110Ah leisure battery permanently fitted to and charged by the tow car for sole use by the caravan.
I have the standard 110Ah caravan battery and I have a portable 110Ah leisure battery that can be quickly be connected to the caravan.
This gives me 400Ah for use in the caravan if I so wish.
All of these batteries can be charged by the tow cars alternator if I so wish.
OK my wiring is non standard and considerably beefed up....but it can be done.

 

[JTQ]

"portable 110Ah leisure battery"

Now that does stretch the imagination

Might have coped 20 years ago.

 

[Gafferbill]

JTQ.....best stick to rolling out the mains cable then

 

[colin-yorkshire1]

Your Sky box is a killer with such a massive drain, compounded by requiring an inverter. Time to buy something like a 12 volt Comag unit taking 12 Watts; this will be a generic decoder so will get the normal TV channels but not Sky unique ones.

thats fine if all you watch is freesat, but if you like watchin sky channels like atlantic, fox, universal and discovery, tough???

 

[Surfer]

Thanks for the input. The reason for the Sky is firstly because we pay a subscription and secondly something to watch in the evenings. Unfortunately not a very good move for me to sit outside in the evenings. We do want to invest in a suitable solar panel at some time, but the price is a bit off putting at the moment.

 

[JTQ]

Your Sky box is a killer with such a massive drain, compounded by requiring an inverter. Time to buy something like a 12 volt Comag unit taking 12 Watts; this will be a generic decoder so will get the normal TV channels but not Sky unique ones.

thats fine if all you watch is freesat, but if you like watchin sky channels like atlantic, fox, universal and discovery, tough???

I had already made that point. Whether there are power efficient SKY boxes I have no idea but as I thought they ought not be used away from the registered property then probably SKY don't think licencing a 12 volt power efficient decoder has much relevance?
A route might be to use the better power efficient set up for all but the particular programs where there is no alternative to using the power greedy SKY one?

 

[graham_somersham]

Thanks for the input. The reason for the Sky is firstly because we pay a subscription and secondly something to watch in the evenings. Unfortunately not a very good move for me to sit outside in the evenings. We do want to invest in a suitable solar panel at some time, but the price is a bit off putting at the moment.

PV panels are pretty cheap now. There were some 120W panels on ebay recently that went for about £90 or slightly less. 80W are even cheaper. Its simple to make a basic stand yourself and the controllers can be picked up easily for not a great amount (MPPT are still a bit dear). An hour spent installing controller and connecting up to the battery etc and you would have a system that would keep you going indefinitely.
I know Parksy likes the roof mounted panels but freestanding are a lot more efficient to get the max out of as you can position them and easily add extra panels if needed in the winter months when the sun is lower in the sky. A big advantage is you don't have to lug them about if you know you are going to be on ehu. I keep my 80W panel connected all the time at home as it charges better than the caravan charger and also saves me a few bob a year in electricity.
If you must pay money to the evil empire (Sky) you are probably going to need to get a pv panel and maybe you will consider more sites off ehu in the summer months and save on the ehu costs. I covered the costs of my setup in less than one year by staying on sites without ehu.

 

[Parksy]

Thanks for the input. The reason for the Sky is firstly because we pay a subscription and secondly something to watch in the evenings. Unfortunately not a very good move for me to sit outside in the evenings. We do want to invest in a suitable solar panel at some time, but the price is a bit off putting at the moment.

PV panels are pretty cheap now. There were some 120W panels on ebay recently that went for about £90 or slightly less. 80W are even cheaper. Its simple to make a basic stand yourself and the controllers can be picked up easily for not a great amount (MPPT are still a bit dear). An hour spent installing controller and connecting up to the battery etc and you would have a system that would keep you going indefinitely.
I know Parksy likes the roof mounted panels but freestanding are a lot more efficient to get the max out of as you can position them and easily add extra panels if needed in the winter months when the sun is lower in the sky. .......

If and when you decide to invest in solar power Surfer give me a shout if you need and advice or practical help, I'm only down the road

I agree that the price of monocrystaline solar panels has come down significantly since we bought ours Graham.
I read a lot of old rubbish about cheap panels not being as good as expensive ones on various caravan forums but the plain fact is that the overwhelming majority of the panels are imported from China, where the crystals are grown on an industrial scale.
The expensive panels that we see now are only expensive because the vendors here add a large mark up, especially those who supply 'caravan solar panels'.
This is because they can rely on the ignorance of the general public to swallow their sales patter hook, line and sinker rather than carry out some research before they buy, and of course anything containing the word 'caravan' in the product description is invariably advertised at a premium price because the vendors think that we're mugs.

I used my solar panel as a freestanding floor mounted unit for over a year, and the stand was made out of white plastic waste pipe and a couple of elbow joints fastened to the panel with strong cable ties and it cost less than a fiver.
The panel worked brilliantly as a floor mounted unit but some of the rallies we went on at the time had lots of youngsters who would run around without bothering to look where they were going.
That was one of the reasons why I opted for a semi-permanent roof mount, I'd have hated a little kid to be cut to ribbons if they fell head first into my panel.
The main reason was ease of use though, It's up there doing it's stuff right now and I can simply forget it

 

[Surfer]

Thanks for the input. The reason for the Sky is firstly because we pay a subscription and secondly something to watch in the evenings. Unfortunately not a very good move for me to sit outside in the evenings. We do want to invest in a suitable solar panel at some time, but the price is a bit off putting at the moment.

PV panels are pretty cheap now. There were some 120W panels on ebay recently that went for about £90 or slightly less. 80W are even cheaper. Its simple to make a basic stand yourself and the controllers can be picked up easily for not a great amount (MPPT are still a bit dear). An hour spent installing controller and connecting up to the battery etc and you would have a system that would keep you going indefinitely.
I know Parksy likes the roof mounted panels but freestanding are a lot more efficient to get the max out of as you can position them and easily add extra panels if needed in the winter months when the sun is lower in the sky. A big advantage is you don't have to lug them about if you know you are going to be on ehu. I keep my 80W panel connected all the time at home as it charges better than the caravan charger and also saves me a few bob a year in electricity.
If you must pay money to the evil empire (Sky) you are probably going to need to get a pv panel and maybe you will consider more sites off ehu in the summer months and save on the ehu costs. I covered the costs of my setup in less than one year by staying on sites without ehu.

When I checked a few months ago a 120w was nearly £300. I have never seen one at £90, but then I have not checked recently.

Thanks Parksy I will keep it in mind!

 

[Parksy]

There's a 120 watt suitcase model, which includes the controller, on E-bay for £120.99 with free UK delivery Here
The model shown is polycrystaline, not as efficient as monocrystaline but there's a monocrystaline panel Here for £85 +19.90 P+P.

For the more efficient monocrystalline costing a total of just under £105 you'd need to budget for a solar controller (often called a solar regulator) which would cost anywhere between £30 - £90 depending on which model you chose and how efficient you needed the system to be.
The advert mentions something about the complete kit so check via the Ebay email contact at the bottom to find out what you get before you buy, there might be a controller included and if there isn't there's no harm in trying to blag one off them free of charge, they can only say no

 

[Surfer]

Found a 85amp battery in the garage that I had forgotten about and have put it on charge. Thought maybe an idea woudl be to sue that battery to power the Sky digibox only and the 110 amp to do the TV and the rest of the caravan. Should then last at least 3 days perhaps?

 

[Surfer]

Found a 85amp battery in the garage that I had forgotten about and have put it on charge. Thought maybe an idea woudl be to sue that battery to power the Sky digibox only and the 110 amp to do the TV and the rest of the caravan. Should then last at least 3 days perhaps?

As suggested the drain on the Sky digibox was maximum wattage. Please advise how long the 85amp battery will last if only the Sky digibox was drawing from it via an inverter. Thanks.

 

[Sproket]

I would put the invertor onto the battery & plug a small table lamp into it with a 60w bulb to use the power & keep going back every half hour to check the battery voltage with a meter, then you would at least have some sort of idea how long you might be able to get from it before it requires a re-charge.........

 

[Surfer]

I would put the invertor onto the battery & plug a small table lamp into it with a 60w bulb to use the power & keep going back every half hour to check the battery voltage with a meter, then you would at least have some sort of idea how long you might be able to get from it before it requires a re-charge.........

Thanks good idea!