Battery Price Comparison -- LiFePO4 vs AGM vs FLA
Many pople have told me that Lithium Feric Phospate (LiFePO4 or LFP) batteries are too expensive for them to consider. This is a price comparison of three posible systems for a van dweller with moderate usage, (30-40 Amp-hours per day) and the ability to go a couple of days with limited sunlight. For longer periods of no-sun, the ability to charge from a small generator is included. Prices of quality components from reputable dealers (listed below) have been gotten online without calling for better prices, finding out shipping costs, or using short-term sale prices. The generator and miscilanious wire, fuses, and crip rings are not included, but they will be about the same price for all three systems. Other than the batteries, the systems should last at least a decade with minimal upkeep. These prices can beet, especially for the AGM (Absorbtive Gas Mat variation of Lead-Acid) and FLA (flooded lead-acid) but I would not expect more than a 25% reduction without reducing system quality. In this article, where AGM and FLA have the same properties, I lump them together as "Lead-Acid".
|1||four CALB CA100Fl||$500||two Lifeline GPL-24T||$500||two Trojan T105-RE||$348|
|2||Morningstar SS-MPPT-15L||$213||Morningstar SS-MPPT-15L||$213||Morningstar SS-MPPT-15L||$213|
|3||-||Morningstar RTS||$26||Morningstar RTS||$26|
|5||Meanwell RSP-500-15||$89||Progressive Dynamics PD9245-14.8||$188||Progressive Dynamics PD9245-14.8||$188|
|6||two Renogy RNG-100P||$290||Renogy RNG-100P RNG-150D||$365||Renogy RNG-100P RNG-150D||$365|
Batteries (row 1)
GBS, CALB, and Winston are the most reputable LiFePO4 batteries. After the demise of Balqon (due to the electric truck side of the business) Winstons are harder to get in the US. Lifeline has the best reputation for AGM, and Trojan for FLA.
Usable Watt-Hours are used for comparison between chemestries. 80% discharge at 12.8v average is used for LiFePO4, and 50% discharge at 12.2v average is figured for Lead-Acid. The peak current (in amps) is shown for each, the available power will decrease minimally on LiFePO4, some on AGM and a lot on FLA if this is exceeded significantly. The batteries will still need the full charge however. (Amp-hours is rated at the 20 hour rate on Lead-Acid, the 2 hour rate on LiFePO4.)
Solar Charge Controller (row 2)
LiFePO4 require an MPPT controller as the voltage pulses from a PWM controller can damage the battery. The same controller was specified on the Lead-Acid for ease of comparison.
Battery Temperature Probe (row 3)
Lead-Acid require higher voltage (and charge less efficiently) at lower temperatures. The probe lets the controller compensate for this fact. LiFePO4 do not want charge voltage changed with temperature, but should not be charged at a high rate below freezing. All batteries have reduced life at high temperatures.
Controller programmer (row 4)
Since none of the controller profiles match LiFePO4, set the controller to Gel and use this with a compter to reprogram the settings on install. 13.8v absorbtion voltage for 1/2 hour and 13.3v float is reasonable for this system. (Choosing this could be the subject of an entire article.) The "float" is only to prevent discharge when solar power is available, it is not a continuation of the charge like on Lead-Acid. This can also be used to monitor the controller operation, and is not a bad idea to have for Lead-Acid to optimise settings and do monitoring.
Converter/charger (row 5)
This takes the output of the generator or shore power and charges the battery. None of the reasonably priced options here are good, and getting close to the price of the rest of the system for something used infrequently is rediculous.
The Meanwell chosen for LiFePO4 needs set to 14.0v (or 13.8v) at install, and needs to be turned off manually when full charge is reached. (After about 3 hours if the battery was discharged to 10%.) Leaving it on after full charge is reached will reduce the battery life.
The Progressive Dynamics charger chosen for FLA does not have remote voltage or temperature sensing. If used by itself on a battery discharged to 50%, it will take 6 or 8 hours to charge the battery.
Either option could be used with AGM, with the charge time of about 5 hours. (Setting the Meanwell at 15v or using the fob on the PD to get it to stay at 14.8v.) The PD has the advantage of not overcharging if left on.
The best way to determine charge state when charging is via the battery current, but that is not an option on any converter/charger I know of.
Solar Panels (row 6)
With an MPPT controller, house panels are cheapest if they can be obtained localy and you have the space for the larger panel. Freight costs can easily exceed any cost savings, so smaller panels are specified here.
Since the Lead-Acid batteries are less efficient, require more charge time, and should be kept as close to fully chaged as possible, 250W of panels compares well to 200W of panels on LiFePO4. 250W of panels can produce more power than the specified Solar Controller can use, but with non-tilted panels that will only be on days where the panels produce more power than the batteries can handle anyway.
Total Price (row 7)
Total system price being cheapest on LiFePO4 surprised me. AGM not being cost-effective did not, but Lifeline GPL-4CT are cheaper per Watt-hour than the GPL-24T. True deep-cycle FLA not being available in smaller sizes and specifying the RE varient of the Trojan T-105 (which may not be cost-effective) upped the price of the FLA. If the roof space is available, some cost saving by using 300W of panels and a PWM controler on the Lead-Acid. Shopping around can reduce the cost, more so on the Lead-Acid than the LiFePO4.
No Cell Ballence Boards or BMS
Cell Ballence Boards are frequenty recomended for LiFePO4, but anacdotal evidence shows they may cause as many failures as they prevent on low-voltage (less than 36 volt) low current (less than 50A for a 100Ah) system. Cell ballencing is only an issue near full charge or full discharge, conditions that should be avoided for long life of an LiFePO4 battery anyway. Lead-acid batteries have been shipped for over 100 years without even the ability to easily monitor cell ballence, and it is an issue with them as well.
A BMS (Battery Management System) with monitoring, high voltage cutoff (for failed charger), low voltage cutoff (for excessive use) and out of balance cutoff (for mismached cell charge levels) would be nice, but is not cost effective on a small system like this.
FLA require checking acid levels and refilling if needed. Monthly is recommended. FLA require a vented compartment with easy access to the top for this checking. An equalization charge does about the same thing as cell balancing for LiFePO4.
AGM recomend a vented compartment.
The Meanwell power supply is not designed as a battery charger, and needs manual intervention to shut off. Since this is only done when on a generator or shore power, rarely with this hypothetical situation, it may not be much of an issue. A "countdown timer" can be used to shut off the charger after a programmed time. It also does not come with a power cord, switch, or fuse.
LiFePO4 should be installed with pressure plates to avoid capcity loss due to cell distortion. This is mostly an issue high temperatures or high charge or discharge rates. Terminal up mouting is recomended on most brands, and large side down should be avoided.
LiFePO4 are about 1/2 the volume and 1/3 the weight of equivelent usable power Lead-Acid. Shape differences can be an advantage or disadvantage.
LiFePO4 systems are comparable in total price to an AGM or FLA system for a fulltime boondocker. When you add the longer expected life (2000-4000 cycles rather than 500-1000) the life-cycle cost winds up much cheaper. FLA can be cheaper to set up, but only significantly if lower cost options are used throughout reducing system reliability and costing more in the long run.
Part Sources used for prices
The Best Battery for Full-Time Boondocking: LiFePO4
For use as a house battery for a full-time boondocker, prismatic Lithium Ferric Phosphate batteries have huge advantages over Lead-Acid (including AGM and Gel). Half as many amp-hours have more usable power, you don't need as much solar to charge them, and generator run-time for when that is needed is reduced by a lot. Lifetime is much longer as well, but how much is difficult to know since there have not been long-term studies at "low" charge and discharge rates yet and no one has had them long enough to wear them out without mistreating them. (For use as a house battery, seven to ten years is a reasonable expectation.)
While not everyone will agree, I do not believe a BMS is needed for this usage. Anyone that can handle a Lead-Acid bank should have no trouble avoiding over-discharge, and charging at 1/2 C or less tends to put the cells into balance. (For multiple C charge or discharge, a BMS may be a good idea.)
Rarely mentioned is that you can get by with less solar when using LiFePO4. Besides them being more efficient batteries, they do not need the slow finishing charge of Lead-Acid, and they prefer not to be fully charged rather than having their life reduced by not being fully charged. While it will vary depending on your usage, you can probably have a happy battery bank with 25-50% less solar than would be needed for Lead-Acid.
Unless the battery temperature is near or below freezing, LiFePO4 can be charged from "empty" (10-20% of rated capacity) to full rather fast. 1/2 C for my 260 Amp-Hour pack is 130 Amps, which neither my solar or converter-charger can supply. Combined with not needing to get the pack to full, this means much less generator run time is needed when the solar is not able to keep up.
LiFePO4 is not the same as other lithium batteries, and should not be lumped with them. They perform better (but differently) at fractional-C applications than at high-current ones like electric vehicles, so the recommendations for that use should not be used as a guide how to treat them for house batteries.
What is critical for a long-life LiFePO4 house bank setup is properly set charging equipment. They are not drop-in for Lead-Acid, and will be prematurely killed by treating them as one. For solar charging, I recommend 14.0 volts maximum with 1/2 hour hold time and 13.4 volt float. This will charge them near full then not discharge much during remaining daylight. For a converter-charger I would use 14.2 volts maximum (higher voltage because of the higher current) and 13.2 volts as the float, since LiFePO4 does not like being left for long periods fully charged. With my current converter-charger, I just turn it off after the battery is fully charged.
The lifepo4-resources page I have is updated as I find new information. After a year of use, they are out-performing what I had hoped for them.
LiFePO4 After almost six months
While I can't say that it is a completely fair comparison due to sunnier weather this year and more than twice the usable amp-hours in my LiFePO4 bank than I had in my lead-acid one, the LiFePO4 have exceeded my expectations. On sunny winter days, I was able to fully charge the bank and then run my propane/electric refrigerator (320 watts) on an inverter several hours during the hot part of the day without depleting the batteries. In the late spring, back in the same spot I was last year, I can use the solar panels only to recharge my batteries except when there are several cloudy/rainy days in a row. Last year I was having to run my generator frequently since I only get a few hours a day of strong sunlight due to trees.
The higher efficiency of the LiFePO4 batteries and the ability to accept almost any charging rate until they are full make LiFePO4 much superior to lead-acid when charging from solar panels. On average, I think I am getting 50% more usable power from my solar panels, not including the extra savings due to being able to power an extra load on sunny days.
While I should also see much better performance when charging from a generator, due to my converter-charger not being well designed for them and I have not been able to find the "high-voltage" plug for it, they do not charge quickly from the generator. I also have to turn the converter-charger off on the rare occasions I am plugged in to shore power to avoid overcharging the batteries. With a properly selected converter-charger, the generator runtime to charge the LiFePO4 batteries should be much less than with lead-acid.
As far as I can tell, LiFePO4 have less need of per-cell automatic balancing and automatic over voltage and under voltage cutoffs than lead-acid ones do in a RV house battery where the maximum charge or discharge current is less than one half the rated capacity and it is a "12v" four-cell pack. Overcharging needs to be avoided on LiFePO4, but chronic undercharging (but not to zero) is not a problem for LiFePO4. The latter is much more likely to occur in boondocking situations where solar and generator are used as the main charging sources. Checking cell balance needs to be done occasionally with LiFePO4 if it is not handled automatically , but it is much less of a chore and needed less frequently than checking fluid levels on flooded lead-acid batteries.
My only questions are "Why aren't converter-chargers optimized for LiFePO4 in RV house batteries readily available?" and "Why aren't more people using them?" They are about the same cost as AGM, and should last much longer, making the life-cycle cost less than flooded lead-acid and much less than AGM in addition to the other benifits of LiFePO4.
Virginia City, Nevada
Virginia City Nevada was a silver and gold mining town that is now has tourism as what it sells. There are many small museums, and lots of gift shops and saloons. The first Friday of the month admission to most of the museums is free.
The "Way it Was" museum has mining equipment from the area and the best overall history of the area. The firehouse museum has examples of horse-drawn fire-fighting engines and ladder trucks. The police museum has a large collection of badges from all over the country.
Red Rock Canyon Campground
Red Rock Canyon Campground is located close to Las Vegas, it's only about three miles to the closest grocery store and restaurants. The Red Rock Scenic Loop is a couple of miles in the other direction. Camp sites are $15/night, 14 days maximum. There are over 70 camp sites, some tent only, some RV only. A couple of dozen sites have gazebos over their picnic tables. The campground does fill up even on weeknights during the spring/fall. The city lights and noise are mostly blocked by the hills. Verizon signal is poor, TV is moderate. The sign was missing coming from Las Vegas, turn on the road the BLM fire station is on. (It is about a mile off of highway 159.)
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