Laura & Jeff,
Welcome. Pretty sweet list, eh? Many folks (mostly our trusty moderator) have been expertly nurturing this group for many years!
KingOfNewOrleans right on target about:
the various suppliers of standard systems,
the battery choices,
the spending priorities,
the intended usage questions,
DIY time commitments (include both of your tolerances!).
the various suppliers of standard systems,
the battery choices,
the spending priorities,
the intended usage questions,
DIY time commitments (include both of your tolerances!).
A technical point about LiFePO4 batteries: unlike most other lithium chemistry batteries, lithium iron phosphate batteries trend away from thermal runaway reactions. Other lithiums, particularly LiON and LiPoly batteries can self-excite at out-of-bound voltages, meaning a slight voltage anomaly can within seconds wake the entire chemical house, then neighborhood, then town, then city... all the atoms screaming because one dog barked or one baby cried. This usually results in that one battery bursting into flames. There are Battery Management Systems (BMS) that 1. try to prevent this thermal runaway by disconnecting charge/discharge loads, and 2. try to quickly recover from a thermal runaway by arresting fires.
The more stable LiFePO4 batteries tend to chemically neutralize internally with too high or too low voltages, like part of them permanently goes to sleep each time the voltage is out of bounds. Charge a tiny bit too much, or drain too much, and your $4,000 battery pack acts like a $3,000 pack, then a $2,000 pack, then a $500 pack...
The energy density of LiFePO4 is about 3 times greater than Lead Acid batteries, so if a spear gun pokes a LiFePO4 battery, it will be 3 times more exciting than if a spear gun poked a Lead Acid battery. But then gasoline/diesel have a 100 times higher energy density, so the same spear gun accident (particularly a flaming spear gun!) would be 100 times more disappointing.
Turning the energy point around, leaving the dock with a healthy $4,000 LiFePO4 battery pack (and BMS, and electric motor, and throttle, and propeller....) is like leaving the dock with $4 worth of fuel (and tank, and gas motor, and throttle, and propeller...)
This relatively low energy store brings us to SOLAR PANELS. If you are docked, solar panels are pretty. If you are at sea, solar panels are pretty important, refilling your small expensive tank continuously.
There's another reason even a $50 solar panel is worth its weight in gold: Lead Acid battery sulfation. Every LA battery deteriorates internally when resting, and during light normal use. Lead Sulfate begins to form and grow on both the negative terminal's plates of lead (anode), and the positive terminal's plates of lead dioxide (cathode). These initial tiny lead sulfate growths begin to obscure the internal lead plates (anodes), and lead dioxide plates (cathodes), AND deprive the battery of sulfuric acid, making the battery behave like a smaller and smaller battery. If these minuscule Lead Sulfate growths continue to grow and establish, they harden into Lead Sulfate crystals, which are much more tenacious (most say too tenacious).
A weekly/monthly 2 amp overcharge (100 watts on a 48 volt Lead Acid battery pack) is just the ticket to completely dissolve the pre-crystalized Lead Sulfate amorphous formations. This is the "equalization" process many chargers support, and a gentle and natural daily event with ideally sized solar panels!
Unfortunately, equalization necessarily breaks the water molecules apart into hydrogen and oxygen. Most Sealed Lead Acid (SLA) batteries attempt to catalytically recombine these gasses back into water, but vent excess pressure (about 2psi) so the battery's plastic case doesn't crack open. Most SLA batteries ("maintenance free", Valve Regulated Lead Acid, Gel, Absorbed Glass Mat...) are already starved of water, so losing water (as gasses) also diminishes capacity. Here's the beauty of Flooded Lead Acid batteries: they have removable caps where you can add "distilled water" (no extra minerals to mess up the battery chemistry) to replace the lost water from equalization.
So gentle daily solar equalization that doesn't burp SLA batteries, or make you add distilled water too often to FLA batteries, dramatically increases the capacity life of your LA batteries. I'm at about 8 years on two cheap 60AmpHour parallel deep cycle FLA batteries that are connected directly to a small 15w solar panel (no charge controller). That's about a 1 amp charge a few hours most days, which isn't quite enough to bubble the electrolyte, but is enough to almost daily hold the battery voltage up around 14.3 volts (dissolving sulfates). I add a little distilled water yearly.
Sorry for all the words, but as you know, there are gazillions of details. Another reason to go with the pros.
Mark Stafford
I play with: e-bike, e-kayak, e-scooters, e-cars, e-sailboats, e-houses....
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Posted by: mstafford@natca.net
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