Solar 12 volt system

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Solar 12 volt system

Postby mango58 » Thu Jun 04, 2009 6:06 pm

Hi I have just bought a 80W solar panel for my camper. Come with a morningstar controller and extra cable. What I need to know is what size 12 volt deep cycle battery do I buy. I check the web and there seems to be quite a few on the market. All I want to run is lights and a 12 volt frig. Could I run a converter(what size) with this size solar panel and run a TV or radio or a small bar fridge. We are off travelling for 3 months from Aug to Oct and plan to camp where there is no power. Sorry but I don't following all the watts, Amps, volts etc talk. Is there a expert out there that can help me. Cheers
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Re: Solar 12 volt system

Postby mawilkinson » Wed Sep 02, 2009 5:15 pm

Mate

I am no expert but the bigger the battery the better. not for any other reason but available power. It is amazing how quick a fridge and other 12v appliances can drain a battery, especially if you have kids. If you are on a non powered site and using your panel you are limited by the weather and how much charge you get.

My camper came with an 80ah and it is too small for my needs. I will link another 80ah soon to give me 160ah.

Good luck
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Re: Solar 12 volt system

Postby Komodo » Fri Sep 11, 2009 1:53 pm

Mango I'm no expert but I have played around with 12V chargins systems a fair bit.

You need wo work out your total power (watts) use over 24hours. double that (as a minimum) divide that figure by 12 and that will give you the minimum capacity battery.

ie if you have a fridge that uses say 1.2amps per hour then we go 1.2*12=14.4watts per hour * 24 hours = 345watts per 24 hours. multiply that by 2 = 691.2 watts divide that by 12V = 57.6 amp hours

Personally I think 90ah battery size is the minimum you should look to fitting to a camper or as an auxillary battery.
Your solar charger will charge this size battery with simple loads like a fridge and a few lights no problems - but in case you get a few over cast days you want to make sure you wont get caught short. Plus the bigger you battery the less charge you with draw = long lasting battery shelf life!
Batteries arent cheap - but buying bigger now is cheaper than replacing a smaller battery 3 or 4 times due to discharging it too much!

Id also recomend an onboard 240V charging system for when at home (or van parks) & an anderson plug connection for charging whilst driving to your destination.
Most larger vehicles have alternators that can put out about 80amps - thats equivilant to 960watts worth of solar panels - or a little over 1hp (actually closer to 1kw)! that'll get that auxillary / camper battery up and charged in no time when your on the road. (theres more to it than that - but thats the basics)
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Re: Solar 12 volt system

Postby Derek Bullock » Fri Sep 11, 2009 3:07 pm

Komodo wrote:Mango I'm no expert but I have played around with 12V chargins systems a fair bit.

You need wo work out your total power (watts) use over 24hours. double that (as a minimum) divide that figure by 12 and that will give you the minimum capacity battery.

ie if you have a fridge that uses say 1.2amps per hour then we go 1.2*12=14.4watts per hour * 24 hours = 345watts per 24 hours. multiply that by 2 = 691.2 watts divide that by 12V = 57.6 amp hours

Personally I think 90ah battery size is the minimum you should look to fitting to a camper or as an auxillary battery.
Your solar charger will charge this size battery with simple loads like a fridge and a few lights no problems - but in case you get a few over cast days you want to make sure you wont get caught short. Plus the bigger you battery the less charge you with draw = long lasting battery shelf life!
Batteries arent cheap - but buying bigger now is cheaper than replacing a smaller battery 3 or 4 times due to discharging it too much!

Id also recomend an onboard 240V charging system for when at home (or van parks) & an anderson plug connection for charging whilst driving to your destination.
Most larger vehicles have alternators that can put out about 80amps - thats equivilant to 960watts worth of solar panels - or a little over 1hp (actually closer to 1kw)! that'll get that auxillary / camper battery up and charged in no time when your on the road. (theres more to it than that - but thats the basics)


He said it all. :***
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Re: Solar 12 volt system

Postby oldtrack123 » Fri Sep 11, 2009 10:08 pm

Hi Mango

Your 80w solar panel will only put out about maxof 30 amphrs on a GOOD day.
As a general rule for long battery life they should not be discharged below 50% of their capacity so a 100amphr bat is good for 50amphrs without recharging.
If your daily use exceeds that put in by the solar you are drawing your battery down.
Do as Komoda says,
Find watts rating of each devise divide by 12 x by expected hrs of use per 24hrs ,add all together & you will get total 24hr amphr use, add about 25% to total to allow for charging in efficiencies
.You will now have what you need to replace with charging per day.
from that take away the solar input[ max 30amphrs] leaves you with what you are loosing from battery. Divide that into 50% of batt capacity & result is days your batt will last without some other form of charging [ie driving with alternator charging ]& HEAVY cables between both batts
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