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Discussion Starter · #1 ·
Hi all,
Just trying to figure out the best battery/charging method to use on a two week camping trip coming up. below is what i could gather from what ive read on the internet, just wondering if i have it right?

So.... to work out total amperage usage per day>

1. evakool fridge drawing 2 amps/hour for 24 hours (will be turning it off overnight)
= 2x24 = 24 amps

2. portable 12v boombox drawing 5 amps/hour when turned up loud for 5 hours +
3 amps/hours when on low volume for 10 hours
= (5x5)+(3x10) = 55 amps

3. Two inverted camping fluros drawing 1.8 amps/hour each for 6 hours a night
= (6x1.8 )x2 = 22amps

SO, total amperage usage per day is 24+55+22 = 101 A/H's.

The battery i will have is an optima d31a which claims to have 75 usable amphours and i was planning to have either a solar panel or generator running a battery charger putting 10 amps an hour into the battery. so if i run the charging method (solar or genie) for 10 hours a day ill have 100ah's being put back into the battery.

My main question is with 101 A/H's of draw per day, is that going to damage a battery with a total capacity of only 75 A/H's? even if i have the charger hooked up to it?

or am i better having two batteries with a total usage of 150 A/H's so i can safely draw the full days usage out of the batteries and not drain them completely?

also is there another form of charging better then a 200watt solar panel which only works when its sunny or a noisy generator?
 

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2010 GU DX CRD Grenade :)
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not sure those calculations are quite correct. as far as i was aware 2x24 was 48, so that makes your draw around 125a/h's. unless you mean 2a/h for 12 hours?

i don't think a battery charger will like having extra load on it while also trying to charge the battery, but the solar setup may be ok.

i think you would be better off running the generator during the day to power the fridge and use either a battery charger off the gennie or the solar charging setup to charge the battery/s for the use they will get at night with lights, etc. if you do it that way, you should be able to run your lights and stereo fine and recharge the battery during the day and just use the battery you already have.

this is also dependant on how much driving you plan on doing during the trip. the battery can charge while you are driving and you just give it a top up with the charger when you get back to camp.
 

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nissan patrol
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Mate, be wary of turning your fridge off at night. Depending where you are of coarse. If the ambiant temp is high enough and your fridge warms considerably, you may end up using more amps pulling the fridge back down than letting it run. Maybe, just wind the thermostat up a frag at night??

Besides, it's not real healthy to let foodstuffs vary in temp to much!!
 

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GU8 CRD
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Having had almost exactly the same setup and draw on a sailing boat I would suggest you need to keep pumping the amps in from a charging source to keep the battery at the minimum output voltage (12.5V). To me, it would be impractical to use solar charging alone to recharge the battery as expecting 100 amp hours per day into the battery out of a solar panel whilst camping is somewhat unrealistic (you would need about 400+ watts of panel by my real world guess). In my case I had 80 watts of panel connected to a 100a/h AGM deep cycle battery running the fridge, lights and radio/chart plotter/stereo and on the panel alone the battery would be near exhausted at the end of the day if not charged via the motor for a few hours. The panels in my case put between 10 to 20 amp/hours into the battery depending on the weather. Even charging with the motor for 3 to 4 hours a day (which was only about 10 amp output) every three days or so the battery needed to be fully charged ie charged until it was back at max capacity.

When calculating charging values, you have to consider that only about 80% of the charging current actually goes towards charging the battery, so you have to increase your charging calculation figures by 25%. I think you either need the two batteries and a charger, or need to charge for 4 or 5 hours a day and you will also need to forget about turning the fridge off at night unless you are only keeping your beer in it.
 

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BORDERTREK 4X4 & FABRICATION
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The Bear
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Originally Posted by silver_pigGQ
2. portable 12v boombox drawing 5 amps/hour when turned up loud for 5 hours +

hell tell everyone where you go, so we dont have to put up with that crap
 

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Discussion Starter · #8 ·
Dont get your kinckers in a knot about the stereo, i am very consious about other campers, and as i (and the other 20 people that camp with me) have the tendancy to make noise i take that into account when choosing a campsite. This particular annual trip will be on miles of open beach so as far as im concerned no one will even hear me. thanks for your comments on that.

Now, i have rectified my calculations and i did mean to run the fridge 12 hours (not 24 hours). its an evakool brand fridge which will be running as a freezer chocked full of frozen food, so turning it off overnight will not drop temperature that much. also as i will turn it back on in the morning i figured it would only take 2 hours to get back down to temp and the difference in amperage draw on normal cycle (3000 rpm), which i will run it on to drop the temp for the first 2 hours, compared economy cycle (2400rpm) is only .8 amps/hour.
so if i turn it off overnight it will save 2amp/hours x 10 to 12 hours = 20 to 24AHs and i only drop 1.6Amps extra during the next morning, so i save a total of 18.4 to 22.4 amps. is this correct?

Also, i have been looking at making a DIY 12 v charger, i can make one, i was just wondering what small engines are out there that are quiet? what has everyone been using engine-wise? the main factor i guess would be noise as i dont wont to hear it buzzing away.
 

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You will find it's always more efficient to keep something at a constant temperature rather than turn it off and bring it back to temperature. If u say it won't drop in temp much overnight then it's not going to draw much power??
 

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Don't turn the frig off... well, you can if you want too up until the frst bout of Food Poisoning. Prev posts are correct that it is better and more efficient to hold a temp rather than try and cool back down.

A 120 Watt Solar Panel, plus a few hours running the gear on a Genny, change your "illumination" to LED and put up with a slightly lower level on the boom box and you will have now worries unless it is heavy cloud all day and you will need a bit longer on the Genny.

I run, 2 x 40 Litre Engels constantly (1 as Freezer and 1 as Frig), 1 Flouro for evening meal and hi intensity 40 LED lights for the camp from a 60 watt panel and a couple of hours Genny.
 
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