Power (Batteries and Solar) 101 Questions

[Kojiro]

Can someone point me in the right direction?

Current boat has house batteries totalling 280 amps.

I've read somewhere (can't find it now) that assuming one uses up 50% of house capacity/day then ideally one needs solar panels that over say 4 hours/day will replace the 50% used.

So, based on the above, solar panels around a total of 300 watts should come close to enough......300/12 x 4 = 100amps/day.

I'm not living on board until next April and don't, really know exactly how much the boat and I will consume but wanted to get my thoughts clear (or ready) about solar panels and replacement house batteries.

[senormechanico]

Do a search on this website about solar, mppt controllers, lithium batteries, LiFePo4, and you will have more information than you can handle.

Good luck.
I'm converting to LiFePo4 as we speak.

[Unicorn Dreams]

6-135 Watt panels may do the job in good conditions in your time frame.

4-135 Watt panels would do it in perfect conditions, haha

I have 1125 AH battery bank and use 4-135 panels and a 400 Watt windgen to keep my bank topped off. Total theoretical charge rate is 940 W/13.6 = 70 Amps, give or take. That would be in perfect conditions..

[noelex 77]

100Ahrs a day is a reasonable figure for consumption, but it vary enormously between boats.
Even without living on board you can measure the power consumption of at least the major items and do a crude power budget.

On the production side 300w of solar will just about produce about 100AHrs, but it will also vary enormously depending on location and time of year.

If you are keen to fit solar at this stage I would simply fit the biggest solar array that will physically fit.. No one complains they have too much solar power.

If you are consuming 100AHrs a day you will also need to think about upgrading the size of the battery bank. Somewhere in the range of 400-600AHrs will be needed, but I would leave this until your current house bank needs replacing and your consumption patterns are clearer.