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optimum panel for 85 amp battery
11 October 2014, 16:59,
#1
optimum panel for 85 amp battery
I have just bought a leisure battery for powering an electric fence(£46 posted) was way cheaper than I was expecting which has made me consider getting more for my preps , I just need to know what size/kind of solar panel would be the optimum to charge this 85 amp battery in a reasonable timescale.
Nothing is fool proof for a sufficiently talented fool!!!!
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12 October 2014, 11:18,
#2
RE: optimum panel for 85 amp battery
Couple of questions:
What is a reasonable timescale to you?
Will it be expected to never run out of power?
How much power does the fencing use?
Will it power down the battery overnight?
Skean Dhude
-------------------------------
It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is the most adaptable to change. - Charles Darwin
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12 October 2014, 11:38, (This post was last modified: 12 October 2014, 11:39 by Midnitemo.)
#3
RE: optimum panel for 85 amp battery
The expected usage would be a small LED light set up and a hour or two usage per day on a 300watt inverter just to top freezer up....not very technically minded so I don't know what the amp draw for this would be but I'd like to deploy the panel during the day perhaps hanging in a window or lay out on the back garden all day and have a well charged battery to use at night so I guess somewhere around 7 to 12 hours charge time season dependent.

the electric fence is not part of the prep scenario that's a horse thing in the present.
Nothing is fool proof for a sufficiently talented fool!!!!
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13 October 2014, 11:44,
#4
RE: optimum panel for 85 amp battery
You might be asking a bit much of that battery to run a 300w inverter.

Recommendation for long battery life is to not run it down by more than 12%

Without efficiency losses ( of which there is a good deal on an inverter) your inverter will be able to be run for a max of 25 mins after the battery is fully charged.

If that's enough for you, you'll need approx. 600w generating power to replace the charge in winter months, but only 50w or so generating power in summer months.
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13 October 2014, 16:23,
#5
RE: optimum panel for 85 amp battery
Thanks LS .... the 25 min's use is that 12% of the battery capacity or run down near empty.... would a 150w inverter be sufficient to run a chest freezer.... what kind of usage would I get with the 150w inverter.
Nothing is fool proof for a sufficiently talented fool!!!!
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13 October 2014, 19:43, (This post was last modified: 13 October 2014, 19:47 by Skvez.)
#6
RE: optimum panel for 85 amp battery
Lets assume you have a freezer with an A rating for efficiency and it consumes about 325 kWh/year (about typical for an A rated freezer).

Lets assume it runs about 1/3 of the time (mine seems to keep adequately cool only running 8 hours a day)
So that’s about 2920 hours a year
Or 111W when running

So your 300W inverter could run it but might struggle to start it as starting surges can easily be 3 times the running load.

Lets assume you meant an 85Ah battery

If you don’t want to take it below 80% that 20% power to work with which is 17Ah @ 12V = 204Wh

111W at 204Wh is just under 2 hours (ignoring efficiently losses which we really shouldn’t as they could be 30%).

The problem here isn’t what panel you use or what inverter you use the problem is that fridges require *big* battery banks to operate.
No matter what size of solar panel you had, if you got two or three cloudy days in a row your freezer would defrost.

It’s just not practical for most of us to expect to operate a fridge or freezer in a grid down situation off battery power. If you really need a fridge/freezer (for instance if you are diabetic and need to keep you insulin cool) I suggest you look at gas powered fridge and get a big gas tank.

On the other hand that battery will be comfortable running LED lights for many days between charges.
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14 October 2014, 12:12,
#7
RE: optimum panel for 85 amp battery
thanks Skvez....was thinking in terms of just keeping the freezer going long enough to eat its contents without any spoiling....the led lights are the primary use.
Nothing is fool proof for a sufficiently talented fool!!!!
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15 October 2014, 08:30,
#8
RE: optimum panel for 85 amp battery
If a fridge is important then could I suggest a look at your local caravan seller or go to a caravan spares/accessories web site as there are fridges that use a combination of elec and gas or both at the same time. The fridges themselves use the absorption principle as opposed to having a compressor mechanism and therefore use less power and make less noise. They are also more efficient using gas.
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