Quote:
Originally Posted by Honeyboy
Bob and Donna,
I boondock about six times per year for 5 days or more.
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[QUOTE=Honeyboy;3970804]Bob and Donna,
Thirty days of boon docking per year might not justify LFP, LifeBlue or otherwise, if what you have lasts though those 5 day stints. Or if you have solar and/or another charging means. If you are in need of new batteries, do give LFP a look. The advantages are huge.
Comparing them on price with lead acid is tricky. The cost per AH is just the starting point and is unfairly negative about LFP if you stop there.
Dig into this a bit since you have time. You will find things like these to consider ...........
1) you will need about 30% less solar for the same usable energy if you go solar.
2) your generator will charge LFP fully in a few hours while it will not fully charge lead-acid unless you run it for hours on end (as much as 10 hours for a full charge from 50% to 100% depending on your converter/charger).
3) LFP requires just one charge stage; essentially the first of the three normally used for lead acid.
4) lead acid need frequent 100% charges to live long while an LFP will have a long life even if you never fully charge it -- in fact it will live longer if you avoid charging to 100%.
5) because an LFP can be discharged safely to 20% or lower* (compared to lead acid's 50%) you get a lot more energy out of it before needing a charge. Hence a lesser ampere-hour battery will do the job. (* for maximum life stop at 20%).
6) with lead-acid, the voltage drop under heavy load is large and down around 50% charge, your inverter is likely to kick-off on low voltage (down around 11.5V or lower). LFP voltage remains up around 13V even when state of charge is low and load is high.
7) if you don't abuse an LFP it can last 3000 cycles or more (each down to 20%) and easily 10 years or more. The Lifeblue is warranted for 83% remaining capacity at 10 years regardless of the number of cycles.
8) LFP are sealed maintenance-free.
9) LFP weighs a fraction of what equivalent lead acid weights (think more mpg)
10) Modern "drop-in" LFP have built in protection against overcharge (BMS or battery management system), over discharge, short-circuit, etc. Lead acid do not (unfortunately).
11) the list goes on .............
I have a 300 ampere-hour LifeBlue which is overkill, but I easily get 12 days of boondocking from 400W of solar even if the sunlight is minimal due to shade or clouds. And we are relatively heavy electricity users (propane heater, fans, microwave, espresso maker, toaster, computer (not a laptop), home theater, etc. We do not run our AC from the battery (more on that below).
Some Caveats though .......
I've found no real LFP chargers on the market. Supposedly modern "drop-in" LFP do not need special care in part because of the internal BMS. However, the details of that BMS seem to be a trade secret and what one can deduce from the label on the side of the battery, it is not highly protective in terms of normal use and long life. I'm an anal electrical engineer and don't want to abuse my LFP in part because the internal BMS records abuse and can void the warranty. Issues include difficulty knowing when the state of charge hits 20% because voltage does not drop measurably as the SOC drops. And difficulty avoiding going over 100% charge via solar or any other charger because all halt charging based on voltage and the voltage of an LFP does not rise much when fully charged unless you hit it with very high charge current; i.e., the charger does not stop charging at 100% unless it can deliver enough current to get voltage up to a cut-off around 14 volts. My solar never gets voltage above about 13.8V and less on cloudy days, so continues charging well past 100%. The built-in BMS does not help with this.
The LifeBlue (only I think) does have good built-in monitoring and does send information to a cell phone or tablet app via Bluetooth so does allow one to keep an eye on and, for instance, cut off the solar manually as the battery approaches 100% charge. No chargers, solar or otherwise use this Bluetooth data. External SOC monitors can do this but ones I've looked at don't have settings that are appropriate for LFP (i.e., won't halt charging at 100% reliably).
I think one could treat a modern LFP as drop-in and ignore it and probably get decent life out of it, but for me that's not good enough especially on the solar side where charging current can stay quite low and charge well beyond 100%.
Another caveat is limits on charge current and discharge current. My LifeBlue limits are 80 amps charge and 100 amps discharge. This limits an inverter to 1300 Watts (not enough for AC). I don't recall exactly, but I think the 200 ampere-hour LifeBlue is about the same, so two 200 AH units might drive a 2600 Watt inverter. Some other "drop-in" LFP can deliver more current and charge at a higher rate.
The LifeBlue app reads out temperature, voltage (including individual cell voltage), current in or out, and State of Charge in ampere-hours. If you are okay monitoring the battery via this app, keeping the battery safe is not hard. I check it almost daily. Since electricity is so critical when boondocking, I think most RVers would suggest checking any battery system daily.
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