Thanks Dan.dogman dan wrote: ↑Feb 27 2018 8:44amSomehow, I got the idea this was a remote controlled boat. With a person aboard, if possible go with the safest chemistry you can, lifepo4.
If you do need to go a smaller and lighter chemistry, just get the battery modules from a very high quality source. $$$
It could be possible to get true 12v by doing a 4s pack, then voltage convert to steady 13v. ( like a 12v lead battery full)
The battery can be smaller in AH, not larger in size or weight. Just same size in watt hours.
Example. 10 ah of 4.2v is 42 watt hours. 5 ah of 8.4v is also 42 watt hours. Both could be the same number of 18650 cells.
Just to clarify, it is not a remote control boat.
The auto-pilot is like having a really good-tempered, second crew-member on board who doesn't eat (accept electrons, gobble-gobble), sleep, bitch, whine, and very, very rarely makes mistakes and allows me to fly the kite, eat, etc.
At 3.7 v max from lipo cells, that makes 14.8 peak voltage 4s.
!2.6v would be the objective but "voltage converting?
I'm a mariner, not an electronics tech.
How would this be done, reliably, safely, economically by a competent novice?
Some kind of "limiter" I would imagine.
No matter, I think the fire risk is simply too high with the 18650's compared to the lifepo4 chemistry.
And way less work to build and install.
Even if I can contain a fire, I'm still out of the race without power.
On that note, is it okay to embed the lifepo4 in insulating foam?
The case will be a snug fit with no ventilation, i.e. sealed.
I could run copper tubing ($$$) salt water cooling off a venturi vent in the hull only inches away at zero risk.
But I'd rather not.
I suspect 15 amp max charging is a reasonable charging rate for a 75 ah lifepo4.
I guess it would be prudent to put a temp sensor on it so I know.
I can always retrofit cooling if need be.