Lead acid vs EFB vs AGM

[Cadan]

Hi everyone,

I have been reading quite a bit recently about lead acid, EFB and AGM batteries.

Most people seem to agree that AGM are the best, but how about EFB in comparison to conventional lead acid?

Would an EFB behave better than a conventional if you do not charge it very often? (Hold charge for longer especially at low temperatures?)

From what I understand, EFB charges faster, right? Do they also last longer in time?

EFB batteries cost quite a bit less than AGM, is the difference in performance that significant?

Thank you,

Cadan

 

[Hedges]

I wasn't familiar with EFB.
Apparently meant as an economical battery for the new automotive way of operating, where engine shuts off at every stop and then has to crank over again.

What is an EFB Battery?

What is an EFB battery and why are more new cars and trucks coming with them? We'll explain in the Power Source blog.

www.optimabatteries.com

EFB or AGM – Which battery do I need?

<p>New starter battery technologies extend the range available, but also make it difficult for some workshop employees to find the right replacement battery for the vehicle. It cannot always be assumed that the battery which is already installed in the vehicle is really the best technology for...

batteryworld.varta-automotive.com

AGM, I'm expecting 10 years float life or 700 cycles to 70% DoD from my SunXtender, based on manufacturer documentation.
FLA, some people report 20+ years in off-grid use of forklift or Rolls Surette batteries (I think sized for 15% DoD most nights, sufficient capacity for 3 days without sun.)

What is your application?
Most people here are now using LiFePO4 for solar applications, some have repurposed lithium-polymer, and some select lead-acid.

 

[Zwy]

Hi everyone,

I have been reading quite a bit recently about lead acid, EFB and AGM batteries.

Most people seem to agree that AGM are the best, but how about EFB in comparison to conventional lead acid?

Would an EFB behave better than a conventional if you do not charge it very often? (Hold charge for longer especially at low temperatures?)

From what I understand, EFB charges faster, right? Do they also last longer in time?

EFB batteries cost quite a bit less than AGM, is the difference in performance that significant?

Thank you,

Cadan

Application? If solar, look into LFP instead if the battery will be charged above freezing.

 

[Daddy Tanuki]

i went the AGM route initially and paid for it in the end, if you do not fully charge them on a regular basis (minimum weekly) you will walk the capacity down quickly. my AGM bank lasted not quite 3 years in an offgrid system running my cabin. I now run liFePo4's and am much happier.

the AGM's were being cycled 65~70% up to 100% but I found out that I was not truly hitting 100%. not enough absorption time to saturate the cells and thats what walked the system down.

the lithium do not need extended absorption, bring them up to 3.4 and float them and you are good to go. even if they do not hit 100% for weeks on end they do not seem to lose capacity like the AGM's did.

 

[Zwy]

i went the AGM route initially and paid for it in the end, if you do not fully charge them on a regular basis (minimum weekly) you will walk the capacity down quickly. my AGM bank lasted not quite 3 years in an offgrid system running my cabin. I now run liFePo4's and am much happier.

the AGM's were being cycled 65~70% up to 100% but I found out that I was not truly hitting 100%. not enough absorption time to saturate the cells and thats what walked the system down.

The only way I know that one could reach 100% SOC with full absorption is to run 2 banks where one bank is being charged thru full absorption while the other is used to power loads. Then switching banks so the other 100% fully charged bank powers loads and the other is charged thru full absorption.

Attempting to hit full 100% charge while powering loads with any lead acid battery using solar will kill the battery eventually because it most likely will never complete absorption before the sun goes down.

the lithium do not need extended absorption, bring them up to 3.4 and float them and you are good to go. even if they do not hit 100% for weeks on end they do not seem to lose capacity like the AGM's did.

LFP likes partial charge, the only reason to go above 3.4V is to enable cell balancing in a pack. Well suited for a solar powered system.

 

[Mattb4]

Interesting. I was unaware that they are making cars that shut down every time you stop and than must be restarted before you go. Would not be something I would want at all. For a minor gas saving you are subjecting your engine to repeated stress of starting. Not to mention the loss of engine cooling unless they maintain circulation with a electric coolant pump and electric radiator fan. No wonder they need a more robust battery to handle such operation.

I doubt that any of the LA chemistries has anything to offer the Solar crowd now that LiFePO4 is more common. The best of which was the traditional FLA in heavy deep cycle battery designs.

 

[Cadan]

Thank you for your answers!

Offgrid system at mountain cabin. (Offgrid is common here, remote villages still do not have electricity.)

I am also curious for my old car. I only drive one-two times a week for short trips and never used anything else than the original lead acid batteries it came with. Was thinking of maybe upgrading to EFB or even AGM. Old battery is almost done, had to take it out and charge it a few times last winter.

 

[Mattb4]

Thank you for your answers!

Offgrid system at mountain cabin. (Offgrid is common here, remote villages still do not have electricity.)

I am also curious for my old car. I only drive one-two times a week for short trips and never used anything else than the original lead acid batteries it came with. Was thinking of maybe upgrading to EFB or even AGM. Old battery is almost done, had to take it out and charge it a few times last winter.

Would not make any sense in your car to go with anything but the least expensive FLA starting battery and change it out on a 3-5 year schedule. In my truck that I on average drive once a month I keep my battery on a maintainer to avoid a dead battery. It gets changed at the 5year point. I am on my 4th one here this Spring. Only had one failure to start in all that time and it was the Trucks OEM battery at 4 years due to a side terminal breaking loose in the battery.

Your off grid solar system is likely better off with FLA unless you can afford to upgrade to Lithium.

 

[Daddy Tanuki]

The only way I know that one could reach 100% SOC with full absorption is to run 2 banks where one bank is being charged thru full absorption while the other is used to power loads. Then switching banks so the other 100% fully charged bank powers loads and the other is charged thru full absorption.

Attempting to hit full 100% charge while powering loads with any lead acid battery using solar will kill the battery eventually because it most likely will never complete absorption before the sun goes down.

LFP likes partial charge, the only reason to go above 3.4V is to enable cell balancing in a pack. Well suited for a solar powered system.

that is kind of what I was alluding to...

 

[Daddy Tanuki]

Would not make any sense in your car to go with anything but the least expensive FLA starting battery and change it out on a 3-5 year schedule. In my truck that I on average drive once a month I keep my battery on a maintainer to avoid a dead battery. It gets changed at the 5year point. I am on my 4th one here this Spring. Only had one failure to start in all that time and it was the Trucks OEM battery at 4 years due to a side terminal breaking loose in the battery.

Your off grid solar system is likely better off with FLA unless you can afford to upgrade to Lithium.

the difference between quality flooded batteries and lithium is non existent at this point. at least here in Japan. its cheaper to buy lithium and the bms, etc., etc. then to even think about quality FLA. that is what drove me to AGM's that plus the fact I might not be able to water them every month or so. lithiums solved all of that.

 

[Hedges]

Attempting to hit full 100% charge while powering loads with any lead acid battery using solar will kill the battery eventually because it most likely will never complete absorption before the sun goes down.

I think my system can do that. PV array is large enough to charge at 0.6C, but controller programmed for 0.2C
On a sunny day, can operate A/C all day long, have battery recharged half way through the day, complete 2 hours absorption, keep battery at float until late afternoon.

It was sized for GT PV, banking power for the winter. If used off-grid, would need less load for short winter days (like non-electric heating.) My bank is only sized for one night, not 3 days without sun, so not really for off-grid. Should work with larger battery and less load.

 

[Hedges]

Would not make any sense in your car to go with anything but the least expensive FLA starting battery and change it out on a 3-5 year schedule. In my truck that I on average drive once a month I keep my battery on a maintainer to avoid a dead battery. It gets changed at the 5year point. I am on my 4th one here this Spring.

I think AGM is a good choice, if you're willing to spend the extra money.
It can sit longer without self-discharge. No acid seepage, avoids corroding cables.
I think it wants higher charge voltage, not easy to provide if alternator has internal regulator.

I had small Optima batteries in my Civic; several died in 18 to 22 months.
I had a pair of large Optima in my k2500. At 10 years I noticed it was cranking more slowly so replaced (with Odyssey). That is only drive one to two thousand miles per year on average.

the difference between quality flooded batteries and lithium is non existent at this point. at least here in Japan. its cheaper to buy lithium and the bms, etc., etc. then to even think about quality FLA. that is what drove me to AGM's that plus the fact I might not be able to water them every month or so. lithiums solved all of that.

PV system, not automotive starting, correct?
Lithium could be good for cars if system designed for it, but need BMS that supports 800A cranking (less for smaller engines) and must not disconnect with alternator putting out unless there is a surge arrestor of some sort.

 

[Hedges]

Interesting. I was unaware that they are making cars that shut down every time you stop and than must be restarted before you go. Would not be something I would want at all. For a minor gas saving you are subjecting your engine to repeated stress of starting. Not to mention the loss of engine cooling unless they maintain circulation with a electric coolant pump and electric radiator fan. No wonder they need a more robust battery to handle such operation.

Many new cars. You can hear them.
(makes much more sense in a Prius, which can stop and go on battery, or keep running engine while stopped and recharge battery.)
For modern non-polluting cars (1), I see no point, even in stop and go traffic.

I first heard of it in a Honda that was hybrid-lite. 10 HP electric motor in place of flywheel, for a bit of power recovery and assist. But able to crank engine without gear reduction.


(1) A good modern car can drive from San Jose to LA, emitting less pollution than a '65 Mustang sitting parked at the curb. Here, by "pollution", I refer to the substances that create smog and harm health, not organic fertilizer.

 

[Cadan]

As an example, for an 80Ah, prices here are: 100-110 USD for a good FLA, around 130 USD for an EFB, 160-170 USD for an AGM, and at least 4-500 USD for a LifePo4.

(My car is a 2005 BMW, no start-stop on it.)

 

[Zwy]

Thank you for your answers!

Offgrid system at mountain cabin. (Offgrid is common here, remote villages still do not have electricity.)

If this is occasional usage and possibly not above freezing when you are not there, then lead acid would work fine. The reason is even if you don't hit 100% SOC everyday while you are there, the system will eventually hit 100% SOC if loads are minimal when you are not there.

Personally, I'd forget AGM and use true deep cycle flooded lead acid where the batteries can be run with equalization to not only remove sulfation but also to overcome stratification of the electrolyte. Be aware that any lead acid will require more maintenance than a LFP bank.

As an example, for an 80Ah, prices here are: 100-110 USD for a good FLA, around 130 USD for an EFB, 160-170 USD for an AGM, and at least 4-500 USD for a LifePo4.

(My car is a 2005 BMW, no start-stop on it.)

Long term, the LFP will be less cost per cycle. My preference would be LFP and I'd have the system set for 50% SOC charge when I was not there. I'd also find a way to only charge above freezing or a way to heat the bank in colder temps.

This all hinges upon what you want for a system, the operating enviroment, how it will be used and for how long you want the battery to last. Flooded lead acid under light use could go 10 years or more with proper charging and maintenance. LFP could last the rest of your lifetime.

 

[Mattb4]

...

I had small Optima batteries in my Civic; several died in 18 to 22 months.
...

Batteries that die early likely signal a problem either from a continuous drain, charging system problem (Voltage regulator not doing its job), or from a hard starting engine. Many cars nowadays do have a slight draw due to electronics and that is where a maintainer is necessary if the vehicle is not run enough to keep the battery up.

 

[Hedges]

Different kind of death.
The Optima eagerly started the Civic day after day for 18 months. Several times it's final day, few minutes later not even a "click". Could only get a dull glow from headlamps. Auto store tester reported 60 cranking amps, but that is bogus high reading when couldn't light lights.

I think the spiral of lead broke disconnected, leaving a tiny lead plate area in one cell.

Several died a sudden death like this.


The continuous drain is a problem for the Sable. It has gremlins and often thinks driver's door was left open (so I removed dome light). It may keep other things in warm standby? I added a solar panel on the dash board.

 

[Cadan]

Have any of you guys experimented, how much better is an AGM at holding charge than a lead acid? Especially during winter.

I have read in many places that it is better, but I have not seen actual data anywhere.

 

[teal95]

Many vehicles now have ESS (engine start stop). This automatically shuts the engine off when stopped but still in drive, or at least that's how they used to work. Some now shut down while still moving. Anyways this isn't very hard on the engine or starter as the engine is already warm and we'll lubricated. This has now also driven a smaller secondary battery as the voltage from the main cranking battery frequently drops low enough to cause issues with other vehicle electronics.

Newer vehicles also have issues with parasitic draws when shut down. The OEMs have specs for current draws while asleep but there have become far too many intelligent modules (I've seen vehicles with 34 modules).

 

[Vigo]

EFBs are not all that much better than 'typical' fla car batteries except in the specific use-case they're intended for. As 'storage' batteries used at low c-rates i seriously doubt they perform enough better to justify the cost difference.