Tommy,
If you go the LiFePO4 route you will quickly realize how conservative the a-hr rating is. There is a group of about 50 of us using them as housebanks on our cruising sailboats and all have discovered that for the same usable a-hr, we only need 1/2 the capacity of our old lead banks. Part of this is due to almost nil Peukert effect, but the ratings are based on different tests over lead. A lead acid battery gets its a-hr rating at a easy 0.05C discharge all the way to depletion, even though in real usage you shouldn't go deeper than 50% DOD. For a 100 a-hr lead battery that is pulling 5 amps for 20 hours and the battery has nothing left in it. The a-hr rating given to LiFePO4 cells is a brutal 1.0C test to 80% DOD. On a 100 a-hr lithium battery that is pulling 100 amps for an hour, leaving 20 a-hr of capacity in the battery.
I noticed from your site you plan on selling construction DVDs, and for this reason you should include high and low cell disconnects to protect the lithium investment. These cells will give over 2000 cycles IF you ensure that no single cell drops below 2.8 volts or during charging exceed 3.7 volts. They will last even longer if you tighten that range up so you never enter the charge and discharge voltage knees, so 3.05 volts to 3.45 volts per cell.
Your MPPT controller will do an excellent job with these cells and as a bonus due to no phony surface voltage that lead is famous for, you will get max charging for 90% of filling, instead of the constant taper you experience with lead.
As to weight, LiFePO4 cells do not have the energy density of LiPO, but the positive of this trade off is a very safe battery (no fires with these) and a lower price. My two banks give together 200 a-hr (100 a-hr apiece) for a total weight of 60 lbs (30 lbs each).
If you really want long outings (weeks instead of days) with lithium you have to option of running an Engel 12 volt portable freezer. This will keep your steaks frozen and along with water bottles that you transfer to your ice chest as needed to thaw and keep the ice chest cool. If your boating in areas that due to fire danger don't allow the building of a fire pit, an inverter and induction hot plate will keep you in hot meals.
Your doing what I like to do, self sufficient kayak or canoe cruising that includes many days out. For stability reasons I'm not using solar panels even though I have considered out riggers like you did to address the stability issue. Instead I just carry a 8 lb 50 amp charger that will fully recharge one pack in under 2 hours while having lunch at any lakeside eatery or marina.
Good luck with your projects, keep us posted.
Bob
From: Tommy Boy <tommy033107@gmail.com>
To: electricboats@yahoogroups.com
Sent: Thursday, March 20, 2014 2:21 AM
Subject: Re: [Electric Boats] Electric Kayak
I have 2 deep cycle 109ah batteries in my solar canoe "Serenity" right now and if I am understanding you I just replace my batteries with a 4 pack series or two 4 packs in parallel like the batteries in the boat now are.
Nothing else needed ? I have a pretty high quality Morningstar MPPT controller and if I hearing you right then I just keep that and the solar panels as they are and wired the same ? On Wed, Mar 19, 2014 at 9:50 AM, Robert Lemke <robert-lemke@att.net> wrote:
Tommy,Serenity Two would be a good candidate for LiFePO4 cells. I got my cells from Balqon, (8) 100 a-hr 3.2 volt cells, 4 in series to make (2) 12 volt packs. For me without solar, one pack is the outbound pack, the other is the return pack. It is compatible with solar, and since the cell resistance doesn't allow a artificial surface voltage, will allow your solar panels full output without tapering so you will get more energy into these batteries in a shorter time vs lead when charging.Balqon has been a bit flaky on delivery times for cells that aren't the big 700 and 1000 a-hr cells, so check these folks out.Bob
From: Tommy Boy <tommy033107@gmail.com>
To: electricboats@yahoogroups.com
Sent: Saturday, March 15, 2014 12:40 PM
Subject: Re: [Electric Boats] Electric Kayak
TommyHere is my canoe. It has (2) 109ah walmart deep cycles in it now.I built a solar canoe and would love to upgrade to that type of battery. 18 miles to 80 miles wow ! What brand and model is your battery ? where did you buy it at ? Is it compatible with solar panels and wired up the same as lead acid ? Does it charge at the same rate as a lead acid ?Sorry so many questions but you really grabbed my interest with your post.
https://sites.google.com/site/serenitysolarcanoe/
On Thu, Mar 13, 2014 at 12:48 AM, <ewdysar@yahoo.com> wrote:
Hi Bob,Doesn't 200Ah weigh about 250 pounds? Wait, maybe not, you didn't mention voltage. 200Ah@12V should weigh about 65 pounds, 24V close to 130 pounds, 36V about 190 pounds, and so on....I'm guessing that your original FLA batteries were rated with lower capacity. Same weight? Lithium weighs about 40% as much as FLA or AGM for the same rated capacity and voltage. That generally leads to only 3 times the range for the same weight battery pack at the same speed (2.5 times on capacity alone, the rest from lithium's lower Peukert's coefficient). So a 5 times range increase sounds like 60% more battery weight and about twice the battery size (volume).
80 mile range? At what speed? We all know that speed has a huge influence on overall range. Should we assume that 80 miles means about 70 nautical miles? We are discussing boats after all....All of this is an educated guess, but there's not much info to go on. Can you let us know if any of these guesses are correct? Providing more specific info is a bigger help to those who would follow in your footsteps.Fair winds,EricMarina del Rey, CA
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