Leisure Battery - Power table?

Discussion in 'Tech/Mech General' started by Roryboys Dad, Jan 13, 2013.

1. Roryboys Dad

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Is there a list or table giving details of what power is taken from the Leisure batteries when you use TV, Combi heater, lights, etc?

Or is there a way of working it out for myself?

Or is there a thread on these forums explaining what electrical items drain from the batteries and how quickly, or slowly, the batteries will be drained?

PS - I am not an electrician and basic information for the uninitiated would be appreciated.

2. pappajohnFunsterLife Member

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There are too many variables to have a list but its easy enough to work out.

add together all the wattages of each appliance and divide the total by 12 to give amps.

ie: 100 watts divide by 12v = 8.33amps per hour

appliances should have a label showing their wattage and your lights may b e 10watt or 20watt, usually 10watt.

water pump is negligable due to time running and the heatr fan maybe 10amps when running.

Last edited: Jan 13, 2013
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3. ReallyretiredFunster

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Its going to vary a lot according to what you have but combiboiler is 1-4A on blower. Lights will vary a lot but if you have LEDs will probably be less than an amp. A little TV (15") around 2A if run on 12v but more if you run it from an inverter.

Most things will have a label somewhere giving their consumption (in watts) and if you divide this by 12 (the voltage) it will give you the consumption in amps. Multiply the number of amps by the number of hours its used for and this will give the number of amp hours drawn from your battery (e.g. a 110Ah battery will provide 55Ah to be half discharged, the lowest you should let it go).

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4. PikemanFunster

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Hi Guys,
While you are on this subject, can I get some advice, as you obviously have a better idea on this than me. I have a seconhand van, it has twin leisure batteries. The display panel shows leisure battery power as i.e; C50 and if I keep the button pressed, it will display the voltage. Should I assume it is showing me the percentage of charge in the batteries? The reason for my confusion is that it can go down very low (perhaps C20), then I switch it on to charge and immediateley hits say C85 in seconds.

What do you think?

Keith

5. scotjimlandFunsterLife Member

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I think you are reading it correctly Keith

C20, C50 etc is showing the remaining capacity of the battery in percentage of it's ampere/hours,.. it is reading the battery voltage from which it calculates the remaining charge.. when you switch the charger on it will now read the voltage being applied by the charger.. so it will read higher, this is not an indication of it's remaining capacity.

It will also drop when load is applied and recover with no load. .. at best it is only a guide..

Last edited: Jan 13, 2013
6. Taran_LasFunster

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Is this what you were looking for? (Apologies for the formatting)

Some Low Power Applications Approx. Watts
Digital camera 3W - 19W
Camcorder charger 3W - 20W
Mobile phone charger 5W - 10W
Portable work light 8W - 60W
Electric Razor 10W - 25W
Portable stereo system 10W - 40W
Light Bulb 25W - 100W
DVD Player 35W - 100W
Video game console 39W - 100W
Laptop computer 60W - 90W
X Box 75W - 110W
Baby Bottle Warmer 80W -100W
TV 55cm Screen 85W - 160W
Printer 100W - 300W
CD/Radio Player 200W - 400W
PC and Monitor 20W0 - 400W
Sander (orbital) 250W - 400W
Camp Kettle 750W - 1200W
Toaster 800W - 1500W
Coffee Maker 1250W - 1500W

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7. StealawayFunster

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You could fit an Ampmeterhttp://www.ebay.co.uk/itm/Mini-DC-100A-Red-LED-Digital-Panel-Amp-Meter-Shunt-/180462480607?pt=LH_DefaultDomain_0&hash=item2a0466ecdf

Alex

8. PeterR

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Battery drain

Hi, I'm a newcomer, so I might be asking a question that's come up a lot before. My van is a Devon Tempest, only 2 years old. The leisure battery is 110 a/h. If we stop for the night in spring or autumn with no mains hookup, we find that by morning the leisure battery is so low that the Truma heater won't start up. Our local caravan dealer says that the compressor fridge (Coolmatic 80-litre, 12v only) is taking 4-5 amps. We have 5 dual-tube fluorescent lights that are probably 16 watt units. The manufacturers (Devon) say the battery should be able to cope, but we've had enough of chilly mornings. Does anyone know if a bigger-capacity leisure battery would be the answer? If so, how much bigger should I go?

9. bungyFunster

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hi and welcome

so in general, a bigger capacity is a bigger physical size , so depending on where your battery is located, it might dictate what you can do in terms of increasing or adding additional ones - so a good place to start would be finding that out, then taking it from there.

worth seeing if you can change the tubes for LED - makes a significant difference, but i guess the fridge is something you will be stuck with

However, its worth checking a few things on the fridge though such as the seals to make sure they are all good, and also increasing the temperature a little in the fridge - it may be working quite hard to keep it cool and increasing the drain

There is a lot of trial and error to this fridge lark Whilst we don't have a compressor type it took us a little while to work out the best way to use ours for it to work well - as in not over filling, getting it down to temperature before setting off on the trip or coming off hook up, being like greased lightning getting things in and out and all that good stuff!!

Given that your fridges average battery drain over a 24hr period is 96 amps, that is hammering your battery, and potentially damaged it because its drained below the magic 50% mark and doesn't now hold a full charge - may be worth testing that as well

But in all honesty, if it was me, id put an additional 110 in if you can, even if you need to move things around to get them both close together somewhere else in the van.

10. G8WVW

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Battery monitor is your answer.

If you rely on battery power and monitor battery state by estimating power usage, guessing split-charge/hook-up charge currents with maybe help of a battery volt meter, you are in for a frustrating time and many flat batteries. I did … and been an electronics engineer for 28-years!

Invested in a NASA BM-1 battery monitor intended for yachts/boats which not only displays battery voltage, charge/discharge current, it estimates battery charge state displaying it as a bar graph in %. It is fabulous and often fairly cheap on eBay.

Cheers.

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12. G8WVW

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Consider putting the fridge on its own 110Ah battery/split charge system?

The fridge is a big chunk of your power consumption. Manufacturer’s website says 'average' consumption is 48W but no qualification on the test condition ie ambient temperature on the outside, internal temperature set by the thermostat etc, in summer it could be more.

You would expect power consumption to be lower at night as the ambient temperature is lower, therefore compressor system has less work to do. All you can do it assume 48W average, that's 4A at 12V. Assuming your fridge is on 14-hours through the night say 7PM to 9AM, that is 14-hours x 4A = 56Ah ie more than half your battery capacity just running the fridge.

Dual fluorescents probably are 16W which with inverter losses in the electronics will be 1.5A each approx. x5 lights (that's a lot of light) is 7.5A. This time of year dark by 5PM, you may run those until say 11PM so 6-hours x 7.5A = 45Ah.

Those two loads above will equal overnight flat battery! Other things to consider:-

1. Battery capacity falls with temperature. The stated Ah is probably at 25 Celsius!
2. The Ah capacity is tested with a current of one-twentieth the Ah rating so for your 110Ah battery this test current was 5.5A. Your two loads draw more than this thereby reducing the Ah figure.
3. Battery manufacturer's generally recommend no discharging beyond 80% of capacity. The control panel in my van disconnects all but one interior light when the battery voltage reaches 10.5V or thereabouts.
All the above considered, your 110Ah battery may only have a 'real' capacity of 60-70Ah. My suggestion:-

1. Make sure you set the fridge temperature to the warmest you can get away with overnight. The cooler the setting, the more power it will use.
2. Make sure the charging circuits are fully charging that battery. With no charge, no discharge full battery should measure 12.6V.
3. Consider putting the fridge on its own 110Ah battery/split charge system so if it does flatten a battery, you haven't lost all power.
Cheers.