Here is the way I mounted the my solar cell 35W.
It is not so big but is enough for keeping my battery fully loaded during the winter with the boat under cover on land.
It is also enough for charging the battery fully loaded in sommertime after a couple of days of not using the Mac.
For your info I have only 1 battery 90Ah for starting the engine, the cooler and all other energy users. But it is a LiFeP-battery that have power
for at least the double size of a lead-battery.
Li Ion batteries have tremendous potential, and the energy density is better than Lippo, with the added advantage of each cell can be run down to 2 volts before you damage the battery unlike Lippo that its only recommended you run down to about 3.4 volts, this gives you around twice the energy density.
I was watching an interesting YouTube doco that did a comparison for FPV RC planes, I think the draw back of Li Ion is the charging rate is much lower than the lippos
What is also very important with LiPo-batteries is if you have solarcells that you have a good regulator so you do not overcharge the battery, then it is dead and you have to buy a new expensive battery.
You must have a regulator MMPT that takes care over-voltage and change it to ampere.
I would be looking at Li Ion instead of lippo, Li Ion is almost twice as dense as lippo for energy storage and as you dont need the one big advantage of lippo (the huge draw potential) really on your boat, Li Ion would be a better choice for house batteries.
At this point both Lippo and Li Ion are stupid expensive to make up a decent size battery but I'm sure those prices will drop through the floor like all things in electronics. The $200ea it cost me for my 105ah / 730cca cross over lead acid marine batteries wouldn't get you squat in Li Ion or Lippo.
As no expert (but i do like some decent research) I'm not sure how the electronics would go at 3.7 volts per cell, giving you 14.8 volts rather than the lead acid 2.1 volts per cell giving 12.6 volts. I would appreciate it if anyone could point me to a good article that talks about running 12 volts stuff at 14.8 instead of 12.6 volts
sailboatmike wrote:...I would appreciate it if anyone could point me to a good article that talks about running 12 volts stuff at 14.8 instead of 12.6 volts
Most battery chargers are up around 14.4 -14.8 in the bulk part of the charging cycle. Will depend on battery type. So most 12 volt items can easily take 14.8 volts.
12.6 is the resting voltage of a fully charged lead acid battery. During charging it and anything else turned on will see the 14+ volts for part of the charging cycle,
@ Bertil, Your choice of LiFePo was very good. the Fe in this keeps it safe in the event of water infiltrating the battery (for what ever reason). Your boat won't go up in flames. All other Li batteries have the issue of possibly exposing free Li to air and water. This is an explosive reaction. They may have higher densities per unit weight but are dangerous unless you do what Tesla does and package them up in goo that keeps them from getting exposed in the event of an accident.
I'm not ready for Li batteries yet. The cost is high and weight issues are not important, in fact, having more ballast is a good thing in my 26M
Safe Sailing!
Captain Paula
Last edited by paula_ke on Tue Feb 27, 2018 8:42 am, edited 1 time in total.
