# 12 volt system and battery life



## dovtrams (Aug 18, 2009)

Hi

i am sure i will get an answer for what is probably seems a simple question. for the first time yesterday, i ventured out in my mh and used only the 12 volt system. a couple of lights, the tv using a camos and maxview receiver. a lovely day by the sea, but kept thinking how long will the battery last. is there a simple calculation which can be used to determine this ie power being used into battery capacity? or do you just wait until the lights go out!

would appreciate some help on this.

regards

dave


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## eddievanbitz (May 1, 2005)

Hi Three main options!

Option one: Wait for the lights to go out! :wink: easiest But, if using this method keep a rough eye on the time so you'll have a better idea next time!

Option two: Add up the wattage of everything your using, divide by 12 and that is how much an hour your using. Look at your battery, find out the amp rating. Divide this by 50% and that is your usable power before the battery needs re charging. Look at your hourly rate, this will tell you how many hours (note to Clive DAB and Frank I know I know! this is an easy way of explaining it :lol: )

Option three: Have a Battery computer fitted (circa £150 -200 installed) This will tell you how much power you have left and how long before your scuppered, how much your using and how to conserve

Have fun

Eddie


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## Vennwood (Feb 4, 2007)

I agree with Eddie here but for total peace of mind I'd go with option 3 (even twist his arm on price) or shop around as there are cheaper, not as good, options that will do the trick

Once a battery has gone below the 50% level then you will have trouble later in its life if not immediately


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## vicdicdoc (May 14, 2005)

You could do worse than fit one of these . . . we have one and know the battery state exactly. 
http://www.allgadgets.co.uk/ag/product.asp?dept_id=1&pf_id=AG3975#


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## Losos (Oct 28, 2009)

vicdicdoc said:


> You could do worse than fit one of these . . . we have one and know the battery state exactly.
> http://www.allgadgets.co.uk/ag/product.asp?dept_id=1&pf_id=AG3975#


That's a neat little unit, I like the fact that it uses a 100A shunt load, to me that is the acid test (Sorry about the pun!)


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## Telbell (May 1, 2005)

> You could do worse than fit one of these . . . we have one and know the battery state exactly.
> http://www.allgadgets.co.uk/ag/product.asp?dept_id=1&pf_id=AG3975#


Chipping in for a minute vdd-I know the above is quite sophisticated but doesn't the normal Control Panel show you what's left of the battery voltage? and if it does, what would be the safest reading to go down to? (assuming 2x110a batteries)

Ta


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## trevorf (May 16, 2005)

Another method is just to use a digital voltmeter and the following table.

Voltage State of Charge
12.6+ =100%
12.5 = 90%
12.42 = 80%
12.32 = 70%
12.20 = 60%
12.06 = 50%
11.9 = 40%
11.75 = 30%
11.58 = 20%
11.31 = 10%
10.5 = 0%

Its best not to let your batteries fall below 50% as has already been said so 12V is really the point where you stop using power and recharge.


Trevor


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## dovtrams (Aug 18, 2009)

:lol: 

thanks to you all for the information you provided. i think i have a better idea now, but if you see a mh on the sea front with the lights out it will probably be me!

dave


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## Telbell (May 1, 2005)

> Its best not to let your batteries fall below 50% as has already been said so 12V is really the point where you stop using power and recharge.


So you're suggesting not to rely on the converter's Control Panel Trevor?
What about the regulator thingy which I now have fitted in conjunction with a Solar Panel?


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## sallytrafic (Jan 17, 2006)

Roughly the same as Trev

Be aware of the notes though.

I would have put the device in that Vic illustrates but haven't just have 3 LEDs

more or less fully charged
getting low
too late!

imagine how boring I could be with all that extra data from the computer - Its by far the best method though.


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## hogan (Oct 31, 2006)

Thanks Frank
Have just printed this out and will put in van.Sad or what????


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## dovtrams (Aug 18, 2009)

Frank

thanks for that helpful and easy to use table, i will also keep a copy.

dave


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## trevorf (May 16, 2005)

> So you're suggesting not to rely on the converter's Control Panel Trevor?
> What about the regulator thingy which I now have fitted in conjunction with a Solar Panel?


It depends on the type of panel fitted. Mine just has a cheap looking affair with green yellow and red zones which I would not trust. Some vans have good looking digital displays which may be accurate but I would confirm by checking against a good multimeter.
If you have a decent charge controller for your solar panel then this should give an accurate reading as long as it is connected to the batteries with thick cable less than 1 meter long otherwise there will be a voltage drop from the batteries to the meter.
I have a Stecca charge controller with 6mm cable just 0.7m long which I leave on the battery voltage display setting to monitor mine.

Trevor


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## vicdicdoc (May 14, 2005)

Telbell said:


> > You could do worse than fit one of these . . . we have one and know the battery state exactly.
> > http://www.allgadgets.co.uk/ag/product.asp?dept_id=1&pf_id=AG3975#
> 
> 
> Chipping in for a minute vdd-I know the above is quite sophisticated but doesn't the normal Control Panel show you what's left of the battery voltage? and if it does, what would be the safest reading to go down to? (assuming 2x110a batteries)Ta


Duh . . when it comes to the mechanics of electricity I'm a dummy - but with this NASA battery monitor I can see exactly the state of charge [or more importantly - the discharge & how long my batteries will last] - we've gone 4 days without hook-up easily [but we do have solar panels on the roof]


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## wakk44 (Jun 15, 2006)

Hi vicdicdoc,
Does your battery monitor have an ammeter which displays the current being drawn from the leisure battery.I would like to know how much current the 12 volt appliances are using.

Also can it be wired into a system with 2 leisure batteries wired in parallel?


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## Mike48 (May 1, 2005)

I am a dummy as well but would be happy to use a multimeter. Can anyone suggest a suitable (cheap) one from the Maplin website or ebay. Thanks.


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## vicdicdoc (May 14, 2005)

wakk44 said:


> . . . Does your battery monitor have an ammeter which displays the current being drawn from the leisure battery.I would like to know how much current the 12 volt appliances are using.
> Also can it be wired into a system with 2 leisure batteries wired in parallel?


Yes, as I switch on more lights or operate the water pump / plug in the TV it shows digitally an increase in the discharge & the estimated time the batteries will last.

Also can it be wired into a system with 2 leisure batteries wired in parallel?
If by Parallel you means 2 x 12v batteries wired to give 12v but double the amps - Well mine is ! :silly:


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## DABurleigh (May 9, 2005)

gelathae said:


> I am a dummy as well but would be happy to use a multimeter. Can anyone suggest a suitable (cheap) one from the Maplin website or ebay. Thanks.


http://www.maplin.co.uk/Module.aspx?ModuleNo=37279


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## hogan (Oct 31, 2006)

DABurleigh said:


> gelathae said:
> 
> 
> > I am a dummy as well but would be happy to use a multimeter. Can anyone suggest a suitable (cheap) one from the Maplin website or ebay. Thanks.
> ...


After years of working at BT and using a analogue meter this is the meter i have bought great bit of kit and cheap.


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## dipsticks (Aug 2, 2007)

Wakk44

PM me your mail address if you would like a Nasa monitor manual PDF

Pete


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## DABurleigh (May 9, 2005)

Here anyway?
http://www.jgtech.com/pdf/BM1.pdf


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## coppo (May 27, 2009)

There is a big difference between our hymer DT 201 control panel and our sunsaver 10 solar regulator when assessing battery voltage. The control panel says 12.3v and the solar says 11.3v. This is our third night camping without leccy(we thought £5 a night just for leccy was too much). I have now just plugged in to be on safe(i will pay the fiver in the morning) side as not sure the true voltage state of the batteries.

Paul.


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## coppo (May 27, 2009)

Now been plugged into mains for 10 mins and the control panel says 13.9v and solar 12.9v.

Paul.


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## Telbell (May 1, 2005)

Still seems a big difference 8O


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