Thank you guys so much for clear crisp recommendations, and also thank all of you for all of your contributions in all of the other threads and blogs.
(Back from the relatively remote Ilets de Petite Terre, and now have some data roaming off my phone.)
Going LiFePO4 not new AGMs
I am definitely
sold on the benefits of
LiFePO4. @Navy_Davy the Carbon Foam
batteries seem like a really good solution for upgrading lead, but I actually do want to have the full benefits of Lithium and I am enjoying the
learning process.
Fully integrated solutions?
@
OceanPlanet Bruce Schwab,
JOHNMARDALL, I have much respect for your
work and recommendations, and I have also studied
Emerald Sea Life's
installation on a sister
Lagoon 450. I am sure these solutions are excellent. While I can afford a fully integrated-marine
installation, I do not want to spend
money that I do not need to spend. As I have already purchased a Xantrex FW3000 and 3 Outback 80s I believe I already have good sub-components to
work with. And a
DIY LiFePO4
project would push me to learn more about my
boat – which is actually a major sub-goal of cruising for me. I will review again the OceanPlanet website when I get true
WIFI and try to figure out what I am missing of the more integrated solutions. The MasterVolt website really didn't explain to me what you are
buying.
DIY Solution High-Level
Handling Overcharging:
Solar:
As
44'cruising cat pointed out, the Outback 80s I have can be set to 13.8 bulk and 13.5 float so as to effectively turn off float
charging after
charging the
batteries. This handles over-charging from
solar.
Generator:
We also have a Onan
generator that I now run once every couple of months, really to just keep it use. As the 2000 watts of
solar cover all of our
current needs as long as we stop the
inverter for the laptops around 8-9pm. The
generator output is coming into a Xantrex Freedom 3000
charger /
inverter that has custom
battery settings, and even a two-stage no-float mode. So, like the Outback I can program the
charger to keep the Lithium safe. So even if we are starting and stopping the generator manually, if we are having an evening party and we are distracted we will not take the Lithiums above the knee for high voltage.
Alternators:
Finally, the alternators. We have the stock 80 amp alternators running into I believe under-sized stock Cristec 40 port & Cristec 60 stbd
battery chargers. If we have the engines on, it is usually for the relatively short period of
anchoring. If however we have decided to thumb nature and insist on motoring windward for hours and hours, then it seems like I have the option to shut-off the circuit breaker for these chargers. To do this safely, I turn off the engines, shut the circuit breaker, then fire up the engines again and continue to
motor into the
wind? But there is probably a more elegant voltage detecting relay device that I could put in here that would handle this automatically, as well as turn it back on!
This handles over-charging right? I do not need a diversion load setup? (Although my wife would love hot showers inside of the
boat instead of the hanging camp
shower )
Under-charging
This seems like not a problem to me. We already live under a low-voltage
alarm regime with the current
AGM setup. So there would be no difference to us for an
alarm to sound and to respond. However, going a bit deeper. We are full-time cruisers and have yet to leave the boat overnight, but we will at some point want to leave the boat for a week or two. I would think that I would empty the fridge & freezers, turn them off. The inverter would be off, the bad-boy off. The only loads that I could think we would want remaining would be the
bilge pumps, (possibly a light and some 12 fans). In the case of the
bilge pumps I would rather drain the Lithiums down to 0% than to disconnect the bilge pumps. So it seems to me that low-voltage automatic cut-off is not required. I am most likely missing something? (Also I believe I am currently throwing away 300 amp-hours a day on the lead batteries, so as a practical matter, I do not see how I get to low-voltage unless I am filling
SCUBA bottles - also below.)
What about my lead-acid starting batteries?
Besides the house battery bank, I have a starter battery for port, starboard and the generator. Can't I just leave them as-is and have them charged with the custom Lithium profiles above? Even if these are sub-optimal charging profiles, these are used just for start-cranking and by definition charge themselves as soon as they are used. But maybe I am confused and these 3 lead batteries are only charged by the dino-gas engines and I do not have to worry about the differing profiles.
Creation and Installation:
Alright so I buy quality cells from Winston, Sinopoly, CALB or A123.
Space & Size – this is easy, my battery bay is 15 inches tall so I do not even have to worry about laying them on their side. I could theoretically fit 20 cells of 400 ah each for 2000 ah at 12v! Wow that is a ridiculous amount of amp hours. Currently I believe I will go for about 700-900 amp-hours of Lithium. So space, no problem.
Then it comes down to reputable dealer, stock,
shipping to St. Martin and then finally
price. Would love current, specific recommendations. The various threads go back years and vendor performance changes.
So, assume that I buy 8x 400 ah prismatic cells to build a 2p4s 800ah house bank. This would take up less than half my battery bay and have room left over in case our energy
consumption changes in the future. I see I can buy 0.8C for $466, and 1C for $508, it is a small
price difference, but I have no known use for draining my batteries even at 0.8C, so I should just go with the 0.8C – correct? These would have a nominal cost of about $3800 from
Lithium Batteries - Prismatic
I ship these 8 cells to St. Martin and buy/borrow a quality bench top
power supply and perform the top-balancing that is well documented in several places.
While allowing these batteries to settle as long as possible (2-6 weeks), I build a
compression case to hold these batteries and protect them from vibration wear and tear.
Day of Switch-Over
Change the
power charging profiles on the 3 Outbacks and the Xantrex while still connected up to the Lifeline AGMs.
- Shutoff all equipment.
- Remove all equipment from the 12v socket receptacles.
- Kill the solar via the circuit breakers.
- Use the manual disconnect for the house bank
- Use the manual battery disconnect for the 3 lead acid starter batteries
- Disconnect the AGMs. Lift those heavy f*ckers out the stbd hatch.
- Install the compression case for the Lithium
- Install the individual Lithium cells, now in their final 2p4s configuration (do this at least once before day of install to be sure the bank is working as planned and fits into its compression case).
- Connect the Lithium house bank
- Verify voltages (DVM) and wiring (pretty much all the time.)
- Manually re-connect the house bank
- Check the voltage at the 12v socket receptacles.
- Turn on something simple and cheap like fans, assuming that the fans are working and happy, start turning on equipment in escalating value
- Once everything the house normally runs is up and running, start to verify charging is working well.
- Manually re-connect the solar at their circuit breakers, verify the Outback is still on the current charge profile – maybe it got reset with the power off – so check again.
- Verify that the Xantrex has its correct profile. Assuming that the house bank was at 50% SoC, before the Solar takes up, turn on the generator and have the Xantrex fill the lithiums, verify that it shuts off and not over charges. This should also be a good test of the Outbacks.
- And done, I have a working lithium house bank.
I also have an unexpected benefit of this setup:
By using the Outbacks and Xantrex charge profiles, I still have the ability to re-install a lead house bank if for example I had a total failure of the Lithium bank in a
remote Pacific Atoll with only some lead available on the supply ship.
The current draw-backs that I know of:
- Relying on the pack-level voltage monitoring of the Xantrex and 3 Outback controllers, so after the initial balancing I would not have cell-level voltage monitoring. But I could address this by buying some more stuff (would appreciate suggestions) for these 8 cells.
- No automatic low-voltage load cutoffs. The Outbacks actually have low-voltage option so I could isolate my lower priority loads to a bar to be automatically cutoff. The Xantrex already has a low-voltage setting for the inverter and this is practically the only thing that sends my house battery low right now. So I still feel like I do not need this.
Other Questions:
What are the smaller bits that I should buy at the same time as my order?
- Bits?
Some braided connectors? My own desktop power supply? A few more manual emergency disconnect switches? Heavy red&black cable (expensive on islands)? Terminals.
- Induction Cooking?
We currently use propane and butane for cooking gas. I like the idea of switching over, or at least having the option of using an induction cooktop. In daily use, what is your typical amp-hour usage for cooking by induction. And I assume that the Xantrex 3 kw inverter is strong enough? (If I know what typical induction amp-hour usage is, it might change my designed size to 1200 amp-hours of Lithium.)
- Filling SCUBA Bottles?
Does anyone have experience using a Baer Junior air compressor with the electric option? What does it take to fill an 80L tank? I have seen estimates of 220v @ 14 amps for 18 minutes = 77 amp-hours to 600 amp-hours. With our 2050 solar install, I have been averaging 700 amp-hours per day here in the West Indies. We have 3 divers on board and typically dive 2-3x a week. Fills are sometimes hard to get ashore. I would like to avoid a gas-driven compressor. If it took say 200-300 amp-hours per bottle, then a group dive is 600-900 amp hours. Our typical daily use about 430 amp-hours including washing clothes, ice and water-making. So, I believe I am currently throwing away ~300 amp-hours of energy every day. With planning it seems like I could keep our bottles filled off of solar/lithium/invert with careful use of each day's power generation. If not, I have the 5k generator to supplement the solar on a big fill day. Am I thinking about this wrongly?
Thank you again for everyone being so generous with their time and hard-won experience and skills.
-Erik