Changing the midset of an old fart on batteries.

[JeepHammer]

I started 30 years ago off grid, everything was lead/acid, and you fall into the mindset of getting batteries at 100% SOC and keeping them there...

That ment I was forever on the hunt for MORE PANELS. Get the Watts, get them in the batteries at all costs.

So about 10 years ago I started with Lithium, but kept the mindset. Get them charged to 100% and keep them there as much as possible.

I STILL use 20%-25% of battery capacity, but I have FINALLY figured out that 20%-25% doesn't have to start at 100% SOC since the voltage doesn't drop like a rock.

It took me a LONG TIME to connect the dots Lithium produces the actual Ah rating before voltage drops, unlike lead/acid, and you don't have to get Lithium to 100% SOC to keep them healthy. Keeping lead/acid healthy was a full time job, you pretty much can ignore Lithium if you have enough capacity and good BMS units.

Why stick with 20%-25% capacity like i did with lead acid? Longevity.

Lead/acid has a hard expiration date from the time electrolyte hits the plates. Keep them at 100% SOC their entire lives and they still have a fineite expiration date. This is before you figure in charge cycles which degrades the battery faster.

Lithium has a shelf life starting at a decade. Not hundreds of charge cycles, but thousands, with a really LONG shelf life.

Total game changer for me, and it took me a LONG time to grasp this in practical operation. I had to observe it personally before I connected the dots.

With two decades on lead/acid, and having to watch every Watt, and constant maintiance, it took me a very long time to get out of that rut.

Anyone have an experence like this where you had a hard time adapting your thinking?

 

[BartHenry]

I have been using the same 12 AGM batteries since 2015. I want to make the switch to lithium, but my batteries are still going strong... if its not broke...

 

[Rocketman]

I am still that way a bit…
Full-time in an RV, enough solar &battery so I seldom run the generator.

But I want to see the battery hit 100% every day even though I could go 2 days with no problem… maybe even three. Ifi it doesn’t hit 100% for a few days part of my brain starts to worry… the other part cant seem to make the worrier shut up!… lol..

 

[Crowz]

I had the problem getting used to it to some extent but the REAL problem I have is keeping my old 4215bn's from running the things UP to 100%.

I play with settings all the time trying to cripple the chargers to keep from running the lifepo4's to 100%.

I shouldn't have the problem when I get around to getting the server rack batteries for the aio unit that runs the house but for my current dc stuff which has the lifepo4's on it now its been a royal pain.

If I set them low enough to stay at 80% or so max soc on sunny days then they don't charge but to 60% or less on rainy days which is pure weird.

If I set them to charge to 80% on rainy days it goes to 100% on sunny days.......

 

[Tomthumb62]

I had the problem getting used to it to some extent but the REAL problem I have is keeping my old 4215bn's from running the things UP to 100%.

I play with settings all the time trying to cripple the chargers to keep from running the lifepo4's to 100%.

I shouldn't have the problem when I get around to getting the server rack batteries for the aio unit that runs the house but for my current dc stuff which has the lifepo4's on it now its been a royal pain.

If I set them low enough to stay at 80% or so max soc on sunny days then they don't charge but to 60% or less on rainy days which is pure weird.

If I set them to charge to 80% on rainy days it goes to 100% on sunny days.......

Hope you don’t mind a question as I’m still learning. If my lifepo4 can be charged to 100% at 14.4v, if I only charged it to 13.7v, would that be equivalent to only charging to 70% or so? Do people do this typically to extend life of the battery?

I’m reading a lot about different charge profiles for lifepo4 and it’s rather making my head spin lol. Thanks for any insight you have.

 

[Crowz]

Hope you don’t mind a question as I’m still learning. If my lifepo4 can be charged to 100% at 14.4v, if I only charged it to 13.7v, would that be equivalent to only charging to 70% or so? Do people do this typically to extend life of the battery?

I’m reading a lot about different charge profiles for lifepo4 and it’s rather making my head spin lol. Thanks for any insight you have.

13.2 is 70%.

13.6 and above is 100% soc according the charts I have that I go by.

That's resting readings not while charging of course.

I use a shunt to measure actual power in and out of the battery to keep from having to battle with getting voltage readings since my stuff is either charging or discharging all the time.

 

[scubadoo]

Hope you don’t mind a question as I’m still learning. If my lifepo4 can be charged to 100% at 14.4v, if I only charged it to 13.7v, would that be equivalent to only charging to 70% or so? Do people do this typically to extend life of the battery?

I’m reading a lot about different charge profiles for lifepo4 and it’s rather making my head spin lol. Thanks for any insight you have.

"...extend life of the battery?"
Don't overthink it. How long do you expect it to last?
Number one. Buy a quality battery.
Our 4 cell 300Ah Sinopoly LiFePO4 battery has survived 9 years of full-time travel in our motorhome with just a 5% capacity loss. I'm hoping that it may last another 9 years but a few theoretical experts on forums warn me it may just die of old age before then?
Our setup: No charging source exceeds 14.1V. 80A alternator, 50A solar, 30A battery charger.
Battery is ALWAYS at 100% SOC when the battery terminals reach 14.1V regardless of charge current. No absorption necessary although it is sustained by the alternator if still driving. "Float" at 13.40V = c98-100% SOC.

 

[JeepHammer]

It's that BoobTube 'Degree' disinformation thing again.

A charge cycle with Lithium is CAPACITY.

If its a 1,000 Ah battery, and you only cycle 25% (250 Ah) thats 1/4 charge cycle, not a full charge cycle.

Yes, the charger ran, Yes the battery charged, but it didn't do a 100% discharge (cut off voltage) to 100% SOC (cut off voltage), it only did 25% of that cycle, so 25% of a charge cycle for the battery.

I had the HARDEST time understanding that when the factory engineer was explaining it since the factory lead/acid chemist said exactly the opposite about them.

With lead/acid it's how many times the electro-chemical reaction (chemical reaction) reverses. The entire battery has to reverse the electrochemical process every time it switches from charge to discharge (in a serious way) or vice-versa.

There is also the SIGNIFICANT LOSSES trying to get lead/acid to 100% SOC. Internal resistance SIGNIFICANTLY increases as lead/acid reaches 100% SOC. That's a LOT of extra panels to get that lead/acid charged that last 10% or so...

Lithium works almost like a capacitor, load (demand) is either below battery voltage, or supply (charge) is above battery voltage, and there isn't an entire battery chemestry switch each time.

With electrons stored on SURFACES, they kind of fall in sheets, like capacitors, or so I'm told. I'm not "X-Ray Man", no superpowers, I can't see each electron...

I LEAVE BATTERY CAPACITY ON THE TABLE.
I'm never at 100% SOC. My low cut off voltage is about 1/10 high also.
Coincidentally, this is a safety margin thing too, since a damaged cell WILL NOT do full full capacity, it gives me space/time to find that crippled cell before it self destructs, and maybe takes other cells with it.

Now, BIG cells means your BMS becomes economical connecting to single cells, better monitoring/managment that way.

When I told the factory engineer I only used 20%-25% capacity this is what he recommended for 'Issues' as the battery cycled/aged.

To me with 20 years of lead/acid this was burn at the stake talk! Absolute HERESY! It says right here in the Lead/Acid Bible you MUST maintain 100% SOC and float charge them there!

Turns out... He's right and it's no big deal. The batteries don't care if they ever see 100% SOC and from the actual experts, the only time they do see 100% SOC in their industral systems is during capacity and load testing.

THAT FACTOID ALONE BROKE MY (DAMAGED) BRAIN!

If you NEED the power, you NEED to cycle at 100% to keep running, then you don't have the capacity to basically 'Idle' the batteries. No shade on these guys, everyone starts somewhere, and at some point increased usage will exceed, and force, more battery capacity.

I cycled at 100% nearly every day, but with lead/acid and the large inverter didn't tolerate low voltage, so MY 100% battery capacity/usable energy was expended almost every day... The reason I kept spending & building.

But like the experts pointed out, you also have to have PANELS to do that 100% capacity charge every day... Thats a LOT of panels to compensate for other than ideal sun conditions...

If you CAN (have the capacity) 'Idle' the batteries, you have the extra battery capacity, you only ever have to have enough panels for your AVERAGE daily usage since you have battery RESERVE, and that let's the panels catch up from bad sun days over time.

For 25 years I had to watch every single Watt, run generators on bad days or high use days, etc. About 5 years ago when I had a significant amount of Lithium batteries, all that stopped. We can have a bad sun day or two, or an extremely high consumption day and still come nowhere near depleting the battery reserve.

One thing about crappy weather fronts that are slow, we always have a few almost perfect days behind them, the panels easily bring the Lithium storage back up.

Like I said, this broke my brain, I had to see it for myself, repeated over and over, have actual experts explain it to me, go through it all... and I was just stuck in that mindset I couldn't connect the dots and take full advantage of the Lithium batteries.

Maybe I am too close to being a 'boomer', or I ate too much lead paint as a kid...?

 

[JeepHammer]

Number one. Buy a quality battery.
Our 4 cell 300Ah Sinopoly LiFePO4 battery has survived 9 years of full-time travel in our motorhome with just a 5% capacity loss. I'm hoping that it may last another 9 years but a few theoretical experts on forums warn me it may just die of old age before then?

Through testing (I'm compulsive about tracking degradation) I'm dropping about 1% per year AVERAGED over several different Lithium chemestries.

My early used EV cells are fairing the worst, they are pulling the average down a lot... Without those it's more like .4% or .5%

I have a pretty big handful of Headway cells and those things don't seem to degrade at all. I'm figuring the case seals will have to fail before they ever die...

By testing, I can adjust the BMS to keep the cells out of dangerous areas on the charge map.

Adjustable BMS being mandatory if you intend to keep that battery well past it's 'Factory' minus 20% capacity threshold.

Guys say "Weak Battery" like 'Weak' is the key word.

Off grid, when you are cold & in the dark, 'Battery' is the key word! ANY power is GOOD power!

With lead/acid, I had a BIG inverter for the time, and it didn't tolerate big voltage drop, so even maintaining lead/acid at higher voltage they didn't last long (and came with maintaince/corrosion issues out the butt).

Lithium is most certainly the way to go (currently). I'm sure with trillions to be made in batteries for EVs and everything else, or even super capacitors, technology will change. For Lithium will last long enough to get me to the post that stuff is in common production.

Ten years ago when I opened the first Lithium battery I laid hands on I had no idea what a BMS was. I burned my eyebrows off DIY'ing the cells not realizing there was entirely different rules for Lithium. Just not my field of experience, so education and mistakes were in order.

I just failed to grasp the paradigm shift, and I feel slow in the brain pan it took so long to grasp how things changed, all the old rules concerning batteries were pretty much out the window...