12v fridge/freezer>Battery>Solar Panel Setup

Submitted: Tuesday, May 27, 2014 at 20:17
ThreadID: 107975 Views:2975 Replies:4 FollowUps:6
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I'm wanting to eg. purchase a 60lt>100lt fridge/freezer running @ 2.5>6ah (averaging 2.5>3ah's) connecting to say a 125>150ah agm battery via a 195>240watt solar panel + fuse. So my ? is can any1 tell what size battery and solar panel I would need to run a fridge freezer? (This may draw between 50 and up to 80ah's in 24hrs)I have ideas but wanting experienced people on this to comment to get a better understanding, hope somebody can help,

Regards David.
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Reply By: steved58 - Tuesday, May 27, 2014 at 20:39

Tuesday, May 27, 2014 at 20:39
I would say what you have allready mentioned is about right
I run a 80 lt waeco fridge freezer with 2 100 ah batteries and 120 watt solar it works ok but at times 200watt solar would have been nice
Cheers steve
AnswerID: 533267

Follow Up By: David W28 - Tuesday, May 27, 2014 at 21:12

Tuesday, May 27, 2014 at 21:12
Thankyou steved58 appreciate your time.
FollowupID: 816604

Reply By: Ross M - Tuesday, May 27, 2014 at 21:40

Tuesday, May 27, 2014 at 21:40
David W28
Apart from the expected ah usage and the days when you get less from any solar, with that factored in, you can also do the following.

Make sure your fridge, whatever size, has more insulation that just the proprietary BAG they supply in fridge deals. The more you can keep ambient heat away from the fridge the better. Ie less AH used each day. A sleeping bag or additional blanket over the fridge compartment will keep the cool in and the heat way.

Make sure it always has a supply of cooler changed air, which is changed by a small fan and if possible some ducting to get the new air to the fridge condensor so it expells any stagnant hotter air which would reduce the efficiency and add to the run time.

I have found having the additional insulation and a computer fan which, may run all the time if needed = 3.6ah of fan run time in 24hrs and will save more than the 3.6ah it uses by making the fridge run less. You may only need it in the heat of the daytime.= less than 3.6ah used.
AnswerID: 533277

Reply By: chisel - Tuesday, May 27, 2014 at 23:25

Tuesday, May 27, 2014 at 23:25
My first question would be - does the battery also get charged by the car when driving and how much will be driving?

My initial thought is that if you're drawing 80AH/day then you'd want to be supplying more than that on good sun days ... say 100AH, which is going to be in the 250W panel wattage range. Lots of variables involved though.
AnswerID: 533281

Follow Up By: David W28 - Tuesday, May 27, 2014 at 23:40

Tuesday, May 27, 2014 at 23:40
Thanks for your reply chisel. I don't think it would run 80ah/daily that is max calculation. I think on ave it will run on 2.5-3ah plus it cuts out. No not for travelly in car Na just camping for 2-3 weeks. Cheers.
FollowupID: 816614

Follow Up By: chisel - Wednesday, May 28, 2014 at 15:02

Wednesday, May 28, 2014 at 15:02
If you're looking at a Waeco 80L or something like that then it will draw around 3A on average, or 72AH per day ... depending on conditions. In summer it could definitely be higher.
Some of the other options in that size might draw less, say 50AH per day but I think you should work with your original 80AH estimate as a guide for summer. Luckily in summer you usually get more sun so your solar will be working well. Still need that 200W+ if it is your only source of charge (not driving, not using generator).

(Note: If you run as 100% fridge (no freezer) your usage should be about 30-40% lower ... so a max of around 50A per day in summer.)
FollowupID: 816653

Follow Up By: David W28 - Wednesday, May 28, 2014 at 21:21

Wednesday, May 28, 2014 at 21:21
What size battery would I use say with a 200w s-panel eg.
125.0 AH/6.00A (20hr,1.80V/cell,25°C)
135.0 AH/6.75A (20hr,1.80V/cell,25°C)
150.0 AH/7.50A (20hr,1.80V/cell,25°C)
165.0 AH/8.25A (20hr,1.80V/cell,25°C)

Thanx again chisel
FollowupID: 816682

Follow Up By: chisel - Thursday, May 29, 2014 at 12:56

Thursday, May 29, 2014 at 12:56
2 factors with battery size:
1. How long do you want your fridge to keep going when solar is not producing much
2. How long do you want your battery to last - which is dependent on how frequently and how deeply it is discharged.

Without trying to get into more detail (and honestly there are others on here who are far better placed to answer this stuff) I would say you want at least the 150AH type range in order to survive a couple of days of poor weather without trashing your battery.
You'll use less power on those cooler days but it could still end up being 100AH across 48 hours which is about all you should be sucking out of a 150AH battery (and best to only do that very occasionally).

If you have space, and happy to pay, then the more battery capacity you have, the better.
FollowupID: 816725

Follow Up By: David W28 - Thursday, May 29, 2014 at 23:00

Thursday, May 29, 2014 at 23:00
Thanx for replying chisel this will help me heaps I might go 240w s-panel with the 165ah agm deep cycle battery which get me going. I normally camp summer months and luckily get good sunny weather. Cheers Regards David.
FollowupID: 816769

Reply By: mack c - Tuesday, Jun 03, 2014 at 19:14

Tuesday, Jun 03, 2014 at 19:14

Regardles of your solar and battery capacity Also take a 20a AC charger combined with a small 1\2 tp 1 kw Genny.
100kw of solar no good in 1 week of rain or heavy cloud cover. Believe me. I've bin there.
cover your arse.

With the fridge. I have an 80ltr Waeco. Magic as a freezer, which is what I basically use it for on my three\4 monthly trips.
Find a Ducting insulation supplier.
1 1\2 mtrs of 17mm Solid lagging (silver backed) gives you the BEST insulation avail for these things in back of your car\tray.
My 80ltr in rear of Patrol in summer as a freezer. Uses very little juice. and lifting the cover from the lid there's a full layer of condensation over lid of fridge.
VERY efficient. Cost me around $72 but that's 5 or 6 ish yrs ago.
BETTER than any bags\covers you pay a zillion $$$'s for.

Don't overload with battery's, it's no good if you don't have the solar charging power to keep them up. You'll just find yourself digging in pocket regularly for new battery's.
and Dc to DC charging is just a big con financially.Ac\Dc is much better.
AnswerID: 533679

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