oldtimer
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| posted on 21/7/10 at 11:19 AM |
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40W PV panel - what size battery????
Hi all you tech types, I have a 40w photovoltaic panel going to a regulator then 12v output for a battery. What size battery do you think? Use will be
a 40w cooler box and also use as the 'house' (not the starter) battery on my boat. Recommended battery for the boat is 75Ah but will this
be too big for my small panel to keep charged?? Thanks.
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Bluemoon
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| posted on 21/7/10 at 11:33 AM |
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A 40W PV will be two small to run the cooler box all the time as you only get 40W out when full sunshine....
40W/12V = 3.3 A, so a 75Ahr battery would last 11hrs to 50% discharge (you don't want to go less than this, as the batteries don't like
it).
My 5W PV will keep my 75Ahr charged, but not a lot more, i would guess your 40W panel would be o.k., but only if you use you cooler for say 1
day/week..
You would be better off using a lot bigger PV or gas fridge for long term use..
[Edited on 21/7/10 by Bluemoon]
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oldtimer
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| posted on 21/7/10 at 11:37 AM |
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You are right, but I have got what I have got......I am hoping that buying chilled food and using ice blocks and only having the cooler on some of the
time will help.
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jossey
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| posted on 21/7/10 at 11:40 AM |
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i would suggest looking at another solar cell and get a 110ah battery so you can use the cooler occasionally and charge all time.
:O)
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Liam
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| posted on 21/7/10 at 01:49 PM |
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Like a normal kitchen fridge, I expect that cooler wont be running at 40W continuously, but only kicking in every now and again. My full size tall
kitchen fridge is rated at 180kwh/yr which works out to an average of about 20W continuous, so your cooler ought to run considerably less. Therefore
I'd expect that 40W solar panel to keep the cooler running and the battery topped up just fine. Wouldn't need a massive battery to buffer
between the panel's supply duty cycle and the cooler's demand duty cycle. Normal car battery should be fine.
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oldtimer
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| posted on 21/7/10 at 01:53 PM |
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Thanks peeps, think I'll get the 75Ah leisure battery and use for both, and try and limit the cooler hours.
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Bluemoon
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| posted on 21/7/10 at 03:38 PM |
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quote:
Originally posted by Liam
Like a normal kitchen fridge, I expect that cooler wont be running at 40W continuously, but only kicking in every now and again. My full size tall
kitchen fridge is rated at 180kwh/yr which works out to an average of about 20W continuous, so your cooler ought to run considerably less. Therefore
I'd expect that 40W solar panel to keep the cooler running and the battery topped up just fine. Wouldn't need a massive battery to buffer
between the panel's supply duty cycle and the cooler's demand duty cycle. Normal car battery should be fine.
Unfortunately most 12V coolers are solid state, with no compressor, or 12V heater driven ones. They draw a lot of current and do not all have a
thermostat (i.e always draw 40W)..
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