dogman dan wrote: ↑Feb 24, 2018 8:22 amStarting point on your math is the output of the panels. Potential max output matters not, since it might be cloudy on race day. Even just thin high clouds have a huge impact. So its not 300w x 18 hours.
That is correct Dan, thank you. Like I said, the panels are rated (for your reference) at 5.5 max output.
That is in direct sun, mid-day, clear sky, clean panel, and new.
300w of panel, figure if you are lucky, you get 1500 watt hours per day. Could be less though, or a lot more depending on season and weather. I'm just starting there with 5 hours average daily insolation for a figure.
[The season, as I said, is mid June, the latitude ~50 degrees north.
I did the same math but used six hours a day vs your five./b]
divide by 24 hours, you get 62 watt hours per hour to work with. Sounds like not enough to me. 5 amps x 12v is 60 watts, so 60 wh per hour. Yes, inside the number, but not much leeway for having cloudy weather even part of the day.
4 panels would do er for sure I think.
I simply don't have the space for more than three panels.
This is not a large boat by any means.
Or, start with a larger, full battery. You have 1000wh, so 16 hour reserve. That could be plenty if the race is short, like 3 days. If its 15 days, not that big a reserve.
The race should be 2 - 4 days.
Your calculations mirror what I have thought about solar charging a bike on tour. At some point carrying enough panel just gets impractical, unless you can periodically put more power in.
I just watched the show on the solar plane that went round the world. It had to carry really impressive size panels, and enormous battery to get through the night, AND, serious navigation to avoid any clouds at all.
Thanks John.John in CR wrote: ↑Feb 24, 2018 7:54 amDon't even consider putting craptastic cheap RC lipo batteries in a boat. Use only safe chemistry batteries. A fire that can't be extinguished is a bad thing on a boat, especially a boat that is almost 100% flammable. I assume you aren't racing a shipping container. There are much better and safer battery options for your needs that are less costly too.
Why such a low voltage?
If I had to rely on them, then Yes. For puttering around in an RC vehicle, the Turnegy are fine. If my safety was on the line, or if I had invested a lot of money in something like a race boat and planned on winning, and wanted reliable safe equipment, then I would pay for the best I could get.
Unfortunately for RC lipo packs it is not that unlikely. The quality control on these packs is spotty at best so can suffer internal faults, but they are also have poor mechanical protection, so being tossed around at sea could result in cells chaffing through. Any saltwater ingress would also be wicked straight into the packs and wet the connections between cells where you can't dry it.
Thank you.Drunkskunk wrote: ↑Feb 24, 2018 4:44 pmIf I had to rely on them, then Yes. For puttering around in an RC vehicle, the Turnegy are fine. If my safety was on the line, or if I had invested a lot of money in something like a race boat and planned on winning, and wanted reliable safe equipment, then I would pay for the best I could get.
But it doesn't have to be that much more expensive. Sanyo 2900ma have almost 50% more capacity, so twice the cost more per cell (of the 50% off sale price of those turnegy) only means 50% more cost per equivalent capacity.
Thanks John, I like the idea of that.John in CR wrote: ↑Feb 24, 2018 10:00 pmLifepo4 for a real 12V, which 3s of lipo is not. I'd imagine all those electronics will work on up to 24V, since that's also a common marine voltage. If slightly more than 12V works, then 4s using automotive batteries is the way to go. Get the energy density equivalent to RC lipo, but in a properly engineered pack format with a battery chemistry that won't go into thermal runaway. Then all you have to do is make it waterproof and secure it properly, so that's weight savings over RC lipo in a steel can plan.
Thank you.Hillhater wrote: ↑Feb 24, 2018 7:56 pmYou need to be sure that 3P of those cells will keep your equipment happy.
By the time you have 50% discharge , you will be down to near 9 volts, and running the pack down to low capacity will definitely be in the 8 volts range .
Some of your instruments etc may not work at all, or lose accuracy.
Most 18650 pack fires are from build faults, charging errors, wiring faults, and human error...rather than cell defects. Assembling and completing a safe , secure , well engineererd , reliable , pack is not easy quick or cheap.
Why not go safe, and simple, with something like this 12 v, 100 ah , deep cycle LIFEPO4 , for $1200 ?
http://www.batteriesdirect.com.au/mobil ... 2-100.html
Likely cheaper elsewhere..?
Thank you.Punx0r wrote: ↑Feb 24, 2018 5:44 pmUnfortunately for RC lipo packs it is not that unlikely. The quality control on these packs is spotty at best so can suffer internal faults, but they are also have poor mechanical protection, so being tossed around at sea could result in cells chaffing through. Any saltwater ingress would also be wicked straight into the packs and wet the connections between cells where you can't dry it.
Good quality 18650 can cells, like the Sanyos, are similar chemistry to the the RC packs but are much better protected and much, much more reliable, but I'd question whether you really want to build a pack this big. It's a lot of work and the resulting construction can introduce a load of potential failure modes if you're not meticulous.
I'd say check out Nissan Leaf modules as they're OEM quality high capacity cells in a metal can but they're 2S so 7.2V 58Ah so probably no good for your 12V system (unless you'd consider a dc-dc converter [it's another thing to fail though]).
I would consider prismatic LiFePO4 cells. These are lower voltage and less energy dense, but the chemistry is inherently much safer and even a serious fault shouldn't result in a fire and 4S gives a genuine 12V. They come in high capacities in a plastic case with simple stud terminals, very much like a lead-acid battery. You might only need 4S1P with simple wire connections to join them up. You'd need some recommendations for a decent manufacturer though as there are some poor quality ones about.
Your pack construction sounds sensible and well though-out. Possibly overkill if anything if you use LiFePO4. If it can be accommodated in the boat, maybe consider splitting the pack into to physically separated parts? That way if the worst happens and you have a battery fire/internal short/failure you can disconnect that and still power your necessary kit from the remaining half.
It was this part (in blue) of my original post I was looking for feedback on.BlueBell wrote: ↑Feb 23, 2018 4:34 pmOkay, if I configure 126 Turnigy 18650 2000mAh 3.7V Rechargeable Li-Ion Batteries,
in 3s46p for 84Ah at 11.1V,
draw them down at 4 - 5 amps continuously, 24/7,
could I charge them through a
ALLPOWERS 20A Solar Charge Controller Solar Panel Battery Intelligent Regulator with USB Port Display 12V/24V,
and 3 Solar Panel ALLPOWERS 100W 18V 12V Bendable SunPower Solar Panel 5.5A max output, Water/ Shock/ Dust Resistant?
This is for a motorless, racing sailboat.
The race is in June at the 50th parallel north.
New construction and considering to purchase the above arrangement.
Max draw is 10 amps but highly unusual, and at worst, intermittent.
Avg draw 3 - 5 amps, 24/7.
Thanks for any feedback before I go ahead and purchase the above.
Have you actually costed your 18650 pack, (branded cells) with protection, extinguisher, container etc ?
Costed, you mean I have to pay for them????Hillhater wrote: ↑Feb 26, 2018 6:16 pmHave you actually costed your 18650 pack, (branded cells) with protection, extinguisher, container etc ?
Ditto its weight and size in completed form ?
Have you confirmed that voltage range (9-11v) is acceptable ?
..i suspect you will find the real differences in size , weight and cost , are not as big as you imagine .
Even less so if you actually need 12 v and 100Ah.