Don't see an electrical forum, need advice.

[Hooks]

So the boat has 2 batteries on board I'm going to charge/test/etc. Have a friend's 6A charger that I'm going to let run overnight on one Saturday and then connect all day to the other Sunday. Figure I can bring them to Autozone and have them test after. They're different batteries with different specs so I assume I can't wire them up together? I don't need a fancy switch I just want to make use of the 2nd battery.

I have a 3rd next to me a buddy gave me (Everstart 94 27DC 109 AH) I'm going get tested as soon as I hit submit. This battery has one purpose. I want it to keep my mini fridge powered when I don't have shore power so my food don't go bad when I sail her.

So the fridge runs on 85 watts and from what I'm reading only runs about 1/3 of the time. So the internet says to multiply 85 by .3 which is 25.5 and then divide this by 12 volts which gives me 2.125. So technically this thing is supposed to eat 2.152 amps per hour on the battery. So an 8 hour sail will eat 17 of the 109 amp hours leaving 84% of the battery so it shouldn't degrade over time right?

I was looking through inverters and this one looked decent, would it work for my purposes? Does the inverter running nonstop drain the battery? Should I go for a smaller watt inverter? http://www.amazon.com/ENERGIZER-Inverter-cigarette-lighter-compatible/dp/B00ATXERNO

So on top of all of that, I want to be able to charge all 3 batteries from 1 device while at shore. Is that possible with the fridge battery not being a part of the other batteries? I imagine I'd either need a charger with 2 separate charging banks or just alligator clips I take off one battery while sailing?

Also has anyone charged the super cheap solar panels? Something like this - http://www.amazon.com/Instapark®-Bl...Controller/dp/B005LR9IOG/ref=pd_bxgy_e_img_z? I don't have a lot of room on a 24 so just playing with the idea.

Thanks guys and gals! I'm going shopping for stuff to clean my boat now.

 

[Maine Sail]

85W / 12V = 7.08A X 1.20 (inverter inefficiency) = 8.5A

Duty cycle .5/hour (always err on the side of caution) = 4.25Ah's

4.25 Ah's X 8 Hours 34 Ah's

Keep in mind this includes no other loads and does not take into account the Peukert effect or the actual Ah capacity of the battery. They are rarely, if ever, producing their "rated" capacity.....

 

[Hooks]

Wouldn't have anything else running on the inverter. Doubt I'll even be in the cabin when at sea I love being outside and in view of the water too much. At 34 Ah's that would still keep me at 66% battery capacity. From what I've read you don't want to go below 50% or the battery starts to die out on you and stops holding a charge.

 

[Chief RA]

If you are going to keep a reefer running you need to go solar as that is the only efficient way to keep those batteries charged. I use a 160w solar panel system for my boat and I would expect that you would need about the same. You will need about 200 a/h for a battery bank also. To recharge older batteries: charge them up as best you can and then pour out the acid. Put in new acid and then charge again. If they can be used the battery will read about 13 volts when freshly charged due to its age and about 12.6 when cold. Bear in mind that these are merely educated estimates by an old sailor and do accept some moderate variations. My best, Chief