Flooded vs, AGM vs Li comparison - interesting but not objective I think

[MNmtb]

Saw this post up on my news feed and thought I’d give it a read. I’m no expert but I think it says more for what is omitted than what is says in the data.

Batteries Tested! The Best RV Battery For The Money - MOTM

Lead-acid vs. lithium-ion batteries: Which is the most cost-effective? We ran the tests and reveal the results: the best RV battery!

mortonsonthemove.com

Discuss.... ?

 

[OllieChristopher]

It's an interesting read but as you say not objective. The tests were not done over years of abuse. Granted I don't have all the fancy test equipment but I can tell you LiFePO4 batteries are getting better all the time. I'm coming up and 9 years and hundreds of hours of the hardest abuse you can imagine on mine. I will "discharge abuse it" over and over until the BMS shuts the battery down.

I also do not buy into the detrimental effects of cold charging a LiFePO4 battery. Even at freezing temps you can simply power up devices to warm the battery so it will charge safely.


Bang for the buck I am of the opinion that AGM batteries are still a tried and true option for those on a budget.

 

[john61ct]

LOL fast charging an LFP bank when well below freezing temps can render a 20,000 investment instant scrap dead as a doornail.

How anyone "feels" about that fact is irrelevant, and it's very easy to test if you really doubt it.

Now milder temps and slower rates, you might only be losing a few hundred cycles per incident iff the back end, might not notice for 15 years, so yes hard to get data, lots of variables involved.

LFP as a generic chemistry is only "getting better" in two senses

1. manufacturers have been improving energy density (not power density)

2. we now know better how to treat them in order to get 8-10,000 cycles before SoH hits 75-80%

The problem compared to 15years ago, is that the list of proven top notch quality cell makers has hardly expanded, but there are hundreds of "cheap Chinese" vendors selling via eBay and Ali, and then all the so-called "drop ins" and powerpacks where no one know what the cells are like, often not user replaceable, so have to assume 2-3000 cycles is best case scenario.

Bang for the buck in lead, so long as you are buying true deep cycle units

by far is FLA.

Unless you really need the higher C-rates, or mounting on their side or something.

The best lead battery value by far is Duracell (actually Deka/East Penn) FLA deep cycle golf cart batteries, 2x6V, around $200 per 200+AH @12V pair from BatteriesPlus or Sam's Club. NAPA relabels it here: https://www.napaonline.com/en/p/NBP8144 Deka self-labeled also sold at Lowes.

The only good AGM for true deep cycling usage is Odyssey, Northstar and Lifeline

with some special use cases justifying Firefly Oasis.

But the cost per Ah per year is at least 2-3x the Deka's.

 

[john61ct]

RTFA feedback.

Yes lead batteries are 99.99% of the time grossly "optimistic" in their Ah capacity ratings.

Even if you do your precisely timed CC load cap test at slower than the standard 0.05C (20-hr rate)

And of course the actual capacity you measure at commissioning time (after break-in period)

will be sharply declining each quarter if you repeat the benchmark,

so your 50% guideline is also dropping in absolute Ah.

In the LFP world, good cell manufacturers in the pouch and especially prismatic universes

routinely deliver 5-15% **greater** Ah capacity than the nameplate.

This is not a major factor in all those taken into account in comparing the chemistries.

Especially in a market where LFP costs 5-10x as much per usable Ah.

 

[john61ct]

The measure of a good lead battery is **not** how accurate their nameplate ratings are

but how slowly SoH% declines per say 100 cycles, the total lifespan before hitting 75-80%.

Compared to the price per actual usable Ah of course.

As stated above the EPM GC's are the king of the NA market in that regard.

 

[john61ct]

It is not correct that Wh should be used for capacity.

So long as the nominal voltage is in the same ballpark (e.g. not comparing 12V to 24V)

Ah give a much more accurate and usable representation of "energy quantity" in and out when dealing with batteries, any DC storage/ discharge system really.

 

[john61ct]

Lifetime cost per sable Ah **per year** would only be lower for LFP f you were doing 100+ deep cycles per year

ideal for those fulltiming off grid for decades.

And **only** if nothing happened to reduce lifespan, even with BMS protection "stuff happens." 10+ years to get ROI is silly risky.

There are **lots** of good reasons to go LFP

but purely economic calculations really go the other way.

 

[john61ct]

Waiting 24 hours or more to get accurate resting voltage is actually done **all the time** in lab condition testing.

But is not necessary to get "good enough" SoC data points, an accurate shunt based coulomb counter can be used, but you need to get the Peukert coefficient and CEF sorted first.

In reality just going from the very precise and objectively defined 100% point, to an LV cutoff calibrated for your chosen CC discharge C-rate

is all you need to benchmark actual useful capacity at that rate.

 

[john61ct]

duplicate post

 

[john61ct]

As to "objectivity" there of course is no "one best" battery.

Too many owner- and use-case specific real life variables involved.

For someone only cycling say under 80 nights per year off grid and not a wealthy person showing off they have all the latest tech

Those Deka FLA GCs just cannot be beat for value.

If you **really** want sealed, then it will cost you, but likely only a couple hundred or so more per year.

If you just **can't** treat them properly so you only get a few years out of them maybe a bit more,

really better off with the cheapest - but still true deep cycle - at ~$1 / Ah@12V

If you are meticulous with proper care then Rolls Surrette FLA can last 14+ years in daily use, and that's without the LFP complications.

 

[OllieChristopher]

The only good AGM for true deep cycling usage is Odyssey, Northstar and Lifeline

Yes John, The X2Power (rebranded Northstar) are the ones I'm thinking on getting for my dual battery setup:

X2Power Premium AGM Battery for BCI Group 78 SLI - SLI78AGMDP at Batteries Plus Bulbs

X2Power group 78 AGM replacement battery designed for low maintenance and dependable engine starting power. Designed or Chevrolet, Cadillac, GMC and more

www.batteriesplus.com

The 5 year replacement warranty is a good selling point. And the distributer is just a few miles from me.

I originally was going to go with a couple of Optima Yellow Tops. But the Amp hour rating is a little less. I'm just a little shaky using that brand as I'm of the belief the longevity is not quite up to par with some of the other offerings. And the warranty is only three years.

15 years ago I would have not batted an eye and went with Optima hands down. A lot of the off road racers still use them as they are super durable and impervious to vibration and shaking.

 

[john61ct]

Yes Odyssey / Enersys originally brought that spiral TPPL technology to the NA market, and under their strict testing & production QA, Optima was a super product, suitable for true deep cycling.

Then they sold the line to JCI (Johnson)

meh. Just like Sears Diehard!

Still fine for a robust Starter though, even support occasional winching etc.

But not true deep cycling anymore, hardly anything sold in automotive or big box retail channels is

99.99% fraudulently labeled all, shame there is no standards body or gov Consumer Protection to enforce objective standards

whole industry is dominated by scammers throughout

 

[OllieChristopher]

whole industry is dominated by scammers throughout

That's just about for anything we buy these days. When I was younger you had only a few choices of any giving product. These days you have to sift through a bunch of bad to find the good.

My favorite kind of reviews are the long term testing ones using math. What makes being objective difficult is tests like the one above. I'm pretty confident at some point we are going to get really close to perpetual motion as far as energy is concerned.

 

[DirtWhiskey]

Well I'm no battery expert and some of the stuff you're talking about sounds like a different language, so please take this with a grain of salt. I've burned up dozens of SLA and AGM over the years (probably because of above), but I will for sure be doing Lifepo4 for my camper build this year. The advantages of not dealing with absorption charge, high amp alternator charging (the biggest advantage IMHO), deep discharge ability, light weight and no need for venting are too much to overlook. I don't really camp all that much in really cold weather but the temp issues seem easy to overcome.

 

[john61ct]

Yes so long as well protected against all the possible murderous "events"

despite costing 6-10x more than lead up front, it is "possible" to work out cheaper over say 20 years use

especially if cycled very frequently.

But that math, requiring decades before getting ROI is **not** persuasive.

The reasons you cite are the main ones.

An energy source at high enough amps can supply days' worth, even a whole week, in just a couple hours

And no need to ever get near 100% SoC

Those are the two big ones.

The low temp issue has several solutions, easiest being make modular packs and just take them with you when the living space you're leaving will be dropping down to freezing while you're gone.

Of course the biggest to pro's for LFP are that the owner loves learning new electrikery tinkering as a hobby, and

the joy of bragging rights, being on the bleeding edge.