Anything new in batteries for solar

I'll have to try and remember the 'outback nano carbon fiber AGM'
Something to think about as an upgrade to the next RV

We are full timers with solar/LFP battery banks in both systems: 34' fifth wheel and 19' (2002) Roadtrek.

5h wheel has 9+ kW-hrs LFP battery bank at 48 V (nominal). Our son designed and fabricated system 4.5 years ago and there is no noticeable degradation. He (with me standing about) trialed it with air conditioner (2+ kW), water heater, and microwave operating simultaneously through the 4.5 kW PSWI. We were drawing over 4 kW (0.5 C). We have run a/c for 4.5 hours as combination of solar/battery suite. We generally are outside on hot days and just run a/c for half an hour to drop cabin temperature below 90 F. 12 V fans are sufficient after that.

The Roadtrek has about 4.5 kW-hr of LFP (two Manzanita Micros batteries as opposed to four in 5th wheel) and it is sufficient to run the smaller a/c for two hours.

So we do a minor discharge/charge cycle each day since we primarily boondock even if we are in an RV park. Read that Liberty Coaches had done full cycles of their batteries over 3000 times. I mentioned this on a thread and a Liberty Coach ($1.8 M and up) said they had done far more cycles since that 3000 cycle article had been posted.

We do try to keep the charge to 50% SOC and higher but have gone below at times.

Our solar has allowed us to use line power less than 10% of our stops. We did use line power for a bit in Yucatan and San Cristobal de las Casas since we did have several days of rain (Roadtrek). We have run into a lot of "dirty power" in USA as well as Mexico so we always run line power through battery charger to the LFP banks.

Do not go to Solar Panel Talk for LFP information. Two of the primary posters are absolute Luddites.

Reed and Elaine

pianotuna wrote:
That is why LI is so attractive even at the premium price.

However the Firefly, and Outback batteries can handle undercharging for 30 cycles and still come back to full capacity. They don't have a price advantage over LI, and of course they are heavy as the dickens. But they can be charged in extreme cold without dying.
...

That Outback Nano-Carbon AGM 100A 12V is US$255 at the Alt-E store you linked to earlier. That's similar in price to other quality AGMs I've seen. And apparently it's not as fussy as other AGMs about PSOC (like LandYacht's NorthStar), and can do 2500 cycles down to 50% or thereabouts. So if I were buying an AGM, that's what I go for.

More cycles than 2000, heck, more cycles than 1000, I don't really care about. We're not full-timers. I figure 100 deep discharges per year max. So 1000 is more than enough. The batteries will age out, get stolen, or I'll be dead, or new technology will make them obsolete in ten years.


On the other hand, I do like those BattleBorn LiFePO4 because their BMS seems to be very proactive in protecting the cells. With the low temp charging cutoff (assuming 7 below freezing is good enough), you could possibly leave them out through the winter. They would stop charging when it got too cold, and prolly stop feeding loads later on when the battery V dropped too low. But when it warmed up, they could go back into business, or at least that's the way their literature reads. Haven't seen any other LiFePO4 BMS with such thorough protections built in.

That is why LI is so attractive even at the premium price.

However the Firefly, and Outback batteries can handle undercharging for 30 cycles and still come back to full capacity. They don't have a price advantage over LI, and of course they are heavy as the dickens. But they can be charged in extreme cold without dying.

I solved the charging problem with twin banks that could be switched so one bank was in use and the other was charging.

2oldman wrote:
Li handles undercharging just fine. I rarely equalized my acids because it's so darn difficult to get a full charge first.

BFL13 wrote:
..you get many incomplete recharges so sulfation sets in. I wonder how they manage in stick houses with all those big expensive batteries and the owner is unaware of any problems.

Li handles undercharging just fine. I rarely equalized my acids because it's so darn difficult to get a full charge first.

Yes, being on solar can "hide" things. Makes everything look good, but you get many incomplete recharges so sulfation sets in. I wonder how they manage in stick houses with all those big expensive batteries and the owner is unaware of any problems.

Equalizing on solar can be done by splitting the bank and doing half at a time over a couple of nice days while running the rig on the other half, then switch over and do the other half. Elaborate procedure and requires several nice days in a row and being able to run the rig that long on half a bank. Not possible most of the year around here with our weather.

OldSmokey wrote:

..
I wonder how often the batteries were equalized ?

one of the biggest problems with off grid/RV solar is equalization.
a proper cycle will take 12 to 24 hours. no solar system can do this without generator help.

on a remote solar design many moons ago I overheard the customer complaining why they needed a generator on site, this was supposed to be a solar powered installation ! LOL

I routinely equalize my FLA batteries with solar when the sun's out. They don't take a lot a current at those high voltages as they've already been fully charged. No generator here.

The batts do go for days at PSOC when boondocking. But a good stiff equalization afterwards goes a long ways to keep them happy.

Hi,

It only requires 60 watts per 100 amp-hours of battery bank to equalize. Equalization can be interrupted and continued on the next day at least with some charge controllers.

With bank switching, I was able to maintain and equalize 875 amp-hours of flooded marine jars, using just solar charging. The batteries lasted for 9 years.

OldSmokey wrote:
one of the biggest problems with off grid/RV solar is equalization.
a proper cycle will take 12 to 24 hours. no solar system can do this without generator help.

BFL13 wrote:

N8GS wrote:

OldSmokey wrote:

N8GS wrote:
Just got more info from Battle Born. There batteries are designed for and the BMS permits charging down to 25 deg F. Below that they will not charge but can be discharged without damage.
Saw an post today on Facebook for a Chinese 12 volt, 300 Ah LiFePO4 battery in 8D size for about $1300. The prices are coming down. I have no idea what the quality of that battery might be.
I like my Battle Born batteries, no more issues with low voltage going to the inverter.

nothing really new for the solar market.. the FLA is still the best bang for your buck..

oh, and low voltage issues are mainly due to incorrect battery sizing..:B

That wasn't the case for me. I had 600 Ah of Trojan batteries. Installed in Jan 2012, in Jan of this year I could not use the microwave, the voltage drop was just too great. When I got home, (we had been in Quartzsite, AZ) I found that 2 of the batteries were shot and the other 2 were not performing very well. Switching to LFP batteries has saved me 215# and when running the microwave the voltage doesn't drop below 12.6 volts even when the batteries are 80% depleted. When running the microwave the inverter is drawing 124 amps. I am disappointed in how the Trojan batteries performed, they should have lasted a lot longer than 5 years considering the care that I took to keep them happy.

As you know, it is the number of cycles, and how deep the cycles, that matters- not years of service. However, given that you know that, it is curious they failed. Anything to do with how tall they are? ISTR Mena was always on about that for making sure he got his stirred up often enough.

I am using a set of two 6v Exide 135s from 2011 in parallel with two used T-1275s in parallel, also from 2011--but they did two years in golf cars first then I got them in 2013) - with about 435 AH total at last test for that, and get about 0.6v drop when using the microwave that pulls about 120 amps on the MSW inverter.

It was more like 1.0 volt drop, but I found a loose wire connection and also fattened a wire a bit to get it down to that now 0.6. The batts are not that new at six hard working years, but so far so good.

Anyway, I am interested in what went wrong more than what was stated.
N8GS is no fool, so anything he has to say about all this is worth paying attention to.

I wonder how often the batteries were equalized ?

one of the biggest problems with off grid/RV solar is equalization.
a proper cycle will take 12 to 24 hours. no solar system can do this without generator help.

on a remote solar design many moons ago I overheard the customer complaining why they needed a generator on site, this was supposed to be a solar powered installation ! LOL

2oldman wrote:
Re: 400ah lithium battery

MrWizard wrote:
it has a 20amp charge current, according to the specs, and a max discharge of 50amps

Oh.. I didn't even notice that. That's terrible!! USA 12v 100ah Li's can charge at a tremendously high rate.. 80a. If you have the charger to do that.

yes, those rates are extremely low for Li, It it most likely a limitation of a paranoid BMS !. controlling rates like that may give the
cells a good lifespan an protect from user abuse.. but in the real world it will restrict application to very few cases.