Small Cabin

# Posted: 20 Apr 2024 10:04pm - Edited by: gcrank1
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Probably a CYA thing, especially if it really isn't an LFP battery but one of the other Lithium chemistries.
LFP has proven to be very safe, but not the same can be said for all chargers.
Fwiw, I monitor all my rechargeables to get a sense of the charging curve and don't leave them on charger past a reasonable time or 'full charge indicator'. I don't even like leaving my cell phone or laptop plugged in overnight.
You could use an inexpensive household timer to run the charger for x hours and shut off. That would give you the rest of the 24 as a buffer.

travellerw
Member

# Posted: 20 Apr 2024 11:38pm
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LiFePO4 is super safe.

but it is a battery. I'm super careful with all of them as I have even seen FLA melt down.

# Posted: 21 Apr 2024 09:04am
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I also feel that is a CYA thing, most especially due to the E-Bike shenanigans which has been hyperinflated by the fear mongering chicken littles. E-Bikes are NOT LFP either !

Gcranks Timer Idea is a GOOD ONE if you have any doubts and until you have confidence.

There is a catch... Sorry. But some of these "chargers" are not the best, usually the cheapest & simplest they can use of course. FAR TOO MANY companies push an envelope of stupidity by pushing the charge voltage too high. Make sure to take a Voltage reading on the chargers terminals to see what voltage it's at, it should NOT be over 13.8V (3.450V per cell X 4 cells). If it is higher, that is overdriving the LFP beyond Working Voltage spec.

It would be useful if ou could post a photo of the Charger & it's specs or a link to the info on this product.

Just in case anyone else comes along. Keep in mind that LFP (LiFePo4/Lithium Iron Phosphate) cells can be either: Pouch, Prismatic (big blue square) or Cylindrical in formats with various AH ratings.

paulz
Member

# Posted: 21 Apr 2024 10:18am
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Agree, CYA thing

Quoting: Steve_S

NOT be over 13.8V (3.450V per cell

Ok, just lowered my solar charger to 13.8. Actually saw 14.1 on the MY50 display yesterday. Suns finally out!

# Posted: 21 Apr 2024 10:31pm
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Yeah, E-bike fire and recently battery powered scrub brush fire. So much junk coming out of China. The mower sat in my garage for a year (one initial charge before winter) because I hate mowing short grass. This year it got about 14" tall so wife gave me marching orders, get the mower going.

I was worried that not charging it (don't know if the charger is also a maintainer) would have harmed the batteries. But they came right back. The batteries measure 13.8 after 5 hours charging, they measured 12.5 after sitting one year.

Folks at Super Droid Robots could not tell me if the charger would function as a maintainer also.

"It is generally safe to keep these batteries on a charger, but we recommend to not over extend charging time to keep the life of the battery healthy and to keep yourself and the unit safe." Yeah, CYA.

The mower is now living in the backyard under the roof overhang with a cover to keep rain off. The day I mow, I hook up the charger and wait five hours. I'm surprised the batteries didn't die waiting for months in the garage. Do LiPoF04 survive not being charged better than other batteries?

Thanks for the responses guys!!
Dave

# Posted: 22 Apr 2024 08:20am
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YES, they do. The self discharge (as long as there are no active or phantom draws) is very low. The recommendation for long life is to not store at full charge, but 60ish%. Also, unlike LA, LFP does not need to be recharged asap after use.
Was the 13.8v observed right after charging or after settling a few hours? You want to wait a bit.
Note that voltage is Not a good good way to measure the state of charge of LFP. It will give you an indicator of the high and low ends but the usable power range is so flat that it is very hard to tell just were in that band you are.
If I were you, Id use the mower as needed, just for drill take a note of the voltage after it sits for some hours and store it.
Before use I would charge it, but sans a state of charge indicator on the unit, keeping an eye on the voltage rise. Once it reaches 13.8 stop rather than continuing. The amps will have fallen off and you will have probably 95% soc.
After a few cycles of use the battery will settle down too and you will have a better sense of how long to 'top it up' prior to use.

# Posted: 22 Apr 2024 08:27am
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LFP is actually one of the best when it comes to retention. BUT they must have some charge, generally between 30-50% when being put into storage for a period of time. They can sit at 50% for over a year "inside" without much loss at all *(IF the BMS is not drawing power). If the BMS is pulling, it will be minimal but can draw down the battery.

At year end, leave the battery at 12.8V +/- a wee bit and no worries. IF the battery drops to 10V it will shutdown (proper BMS function) and should be wakeable with an incoming charge. This depends on the quality of the BMS though.

As an FYI:
I have had LFP cells frozen solid in storage at -30C with 30% charge in them. Once thawed they were fine and still are. LFP can continue to discharge up to -20C but cannot take a charge until they are at +5C internal temp. Limited low charging (0.2C Rate) can happen from 0C to 5C after which full charge rate can be applied.

LFP does NOT explode or catch fire. Worst case that can happen is they overcharge & offgas, at which time they become scrap.

old greybeard
Member

# Posted: 27 Apr 2024 02:03pm
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Just put a LifePo4 battery in my camper. 100AH with a low temp cut off BMS. About $200. Prices have dropped dramatically. When I put new batteries in my cabin 8 years ago they didn't have BMS's available with the low temp cut off. And the batteries were very expensive
When I upgrade definitely going LifePo4

# Posted: 30 Apr 2024 02:07am
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Gcrank1, time for the experiment.
Its been 9 days, time to mow the grass. I measured the voltage, 13.3. Put on the chargers, light is red (charging). Waited two hours, charging lights are green, voltage measures 13.3. Mowed the grass. Next week i'll charge for only one hour.

# Posted: 28 Jul 2024 01:30am - Edited by: DaveBell
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This week, One charged up, the other has been on the charger for 24 hours and is not charging. It's only a year old. I switched chargers, no luck.

Edit: If I have to buy a new one, did you guys who have LiFePO4 batteries use a manufacturer other than Shenzhen? Other Chinese or USA made?

paulz
Member

# Posted: 28 Jul 2024 02:13am
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Can’t help on the brands. But is the dead one showing low or no volts? There was a thread on here awhile back about some chargers not charging super low ones, and jumping with a good battery first wakes them back up enough for the charger to take over.

# Posted: 28 Jul 2024 02:22am
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Curious if you got that one to liven up with a quick 'jump start' off another battery?

paulz
Member

# Posted: 28 Jul 2024 02:38am - Edited by: paulz
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I did get it going again for awhile. had to replace it eventually though. Sounded like others have gone through it. Here's the thread:

https://www.small-cabin.com/forum/3_12038_0.html#msg167908

Might not do Dave any good, just thought I'd mention it.

# Posted: 28 Jul 2024 12:25pm
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It worked for me, think it might be called a 'wake up' for the bms inside after it does a low voltage shut down.

# Posted: 28 Jul 2024 02:33pm
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Quoting: DaveBell

Edit: If I have to buy a new one, did you guys who have LiFePO4 batteries use a manufacturer other than Shenzhen? Other Chinese or USA made?

There are MANY MANY companies in Shenzhen which is a massive city. It's not a Brand Name LOL.

There are several 12V LFP batteries available within the US via Amazon/EBay

LiTime is well rated and their choices with options is pretty good. They have something that fits pretty much every use case and their pricing is respectable. DO READ THE DETAILS !
https://www.litime.com/pages/prime-day-sales

Usually if a BMS sees the voltage as LOW, it will disconnect output to prevent over-discharge but should still allow charging. Unfortunately many "cheapo BMS' " cut off both charge & discharge, essentially bricking the pack. Depending on the BMS there may be ways to unlock it but without knowing specifically what BMS (Make & Model) that can't be determined. That would mean cracking open the box & looking. Warranty on a "No Name" is unlikely. LiTime does Warranty & Service/Support BTW.

Sorry that I cannot help more.

paulz
Member

# Posted: 28 Jul 2024 05:57pm
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Hi Steve,

Hey while you’re here, something I’ve been wondering about. I have a couple of 12v ‘jump starter’ packs, small things about the size of a sandwich, but boy will turn over a car with a low battery. And pretty much right away.

They are LFP, that right? Weigh nothing. I thought LFPs weren’t that good at CCAs. Are they something else? Is there more to them?

# Posted: 28 Jul 2024 06:29pm - Edited by: gcrank1
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Paul, I finally got one of those back in spring and have used it 4 or 5 times, works Great!
from my research before buying they are Not lfp but one of the other lith-ion chemistries that dumps cca quick.
I have charged up my cell phone and a rechargeable lamp off the unit's usb port, also Great, though the car's usb does the same thing at least I can carry that little jump pack away from the car if needed.
If it had a cig-port Id try running my 10" dvd player to see how it does; inquiring mind wants to know! Suppose I could make up a cig female to the plug size at the outlet port (the one for the jump cables).....

# Posted: 28 Jul 2024 09:01pm
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gcrank1 is right, those are either NMC/NCA or LiPo. Those are good for high output - short burst but not sure about long runtime use for much, I suppose it depends on the type because some have extra features & functions but at a $.

# Posted: 28 Jul 2024 11:47pm
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Update
Well I got a piece of two conductor wire and jumped the charged battery to the dead battery, it sparked and scared me a bit. Charged it awhile with no results. So I looked at youtube "LiFeP04 won't charge" and found some more information. Yes the BMS has put the battery to sleep. The charger will not charge because at zero volts it doesn't see a battery.

The charger has to be connected when the jump is connected to trick the BMS and the charger to work. I have sealed male/female connectors between the batteries and the chargers and the positive/negative battery posts have hardened goop over them. They made it as water proof as possible because it's outside.

So tomorrow I'm going to scrape off the goop from the tops of the posts so I can jump it with the charger connected.

HOBOTech on youtube showed three ways to do this. All with the charger connected. Just like jumping you car, you can use another battery, a jump pack, etc. As long as it's 12 Vdc.

Thanks for all your replies.

# Posted: 29 Jul 2024 12:44am - Edited by: gcrank1
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Maybe this just applies to LFP, Ive done it both ways, lfp to a low la and la to a 'sleeping' lfp. It may not be appropriate to do it to other with chemistry?
I know that with a well charged jumper battery the power will flow to the target bat, just leave it hooked up a while to let the charge level come up to where the bms wakes up? It could take a while with your depleted bat to get to the trigger point but there is no overcharge danger to lfp (not sure about the other lith's).

paulz
Member

# Posted: 29 Jul 2024 12:45pm - Edited by: paulz
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I also was able to wake mine with just a jump, however it was a chainsaw battery, so as Steve mentioned it was probably not a Lfp but one of the other types, NMC, NCA or Lipo. These other types are new to me, though I did read a bit briefly. My main concern is the Lfp, since it’s the most important and expensive juice powering my cabin.

Other things around, tool batteries mainly, are all the other types I assume, though Dave’s mower batteries say lifepo4 right on them. Also, many small doodads, motion lights, usb charged things, are also lifepo4 (Lfp interchangeable term?).

These different types have their own traits, CCAs, longevity, safety.. mostly still unclear to me, I just know I use their specific AC chargers.

# Posted: 29 Jul 2024 04:47pm
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LFP = Lithium Iron Phosphate or LiFePo4 - all the same.

LFP, NCA, NCM, LiPoly are all different Lithium Based Chemistries and each have different voltage curves, charge/discharge curves & different capacities per gram relative to the chemistry.

Most laptops, cell phones and small devices like that use LiPoly now (past couple of years) and they could be cylindrical or pouch format. Small devices RARELY use LFP because the energy density is not as high and of course the temperature issues (no charging below 0C/32F for example).

# Posted: 29 Jul 2024 07:14pm
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I cut the goop off of the battery posts and did a voltage reading. 0.20 and dropped to zero fast. Did that three times. Connected the charger, checked voltage at the posts, 14.6 Vdc. So it is charging without the jump. Hobotech did say in his video some chargers will send a charge with the Batt at zero volts. I will check to see if charged in a couple of hours. Got a feeling this Batt may have given up the ghost. Shame, if it only lasted one year. Be back later. Thanks guys!

paulz
Member

# Posted: 30 Jul 2024 12:21am
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I tried to look up the chemistry of Milwaukee tool batts, no luck besides ‘Li-on’. They have a reputation for great batteries of their own design.

Dave, are LiFePo4s the battery type recommended for your setup? Does the mower run on both batts (24v)?

# Posted: 30 Jul 2024 12:41am
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The 42AH LiFePo4s are an upgrade to their standard configuration, 11AH. Yes the LiFeP04 is the only choice. Yes it runs on both batts, 12Vdc motors, one for the right drive motor the other for the left.

Charged the right side battery for six hours today, still dead, charger still supplying 14.4 Vdc. The battery is dead, or the BMS.

I sent an email to Super Droid Robots asking them to replace the battery since its only two years old.

# Posted: 30 Jul 2024 01:13am
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Well, yeah, you gave it a good go....hope they rise to the occasion for ya!