LifePO4 batteries

[Cydog15]

I see a lot of folks are transitioning to Lithium and it reminds me of Solar when it first became popular. It was all about cost per watt. Well there are several companies selling lithium at about the $10 per amp range. BB seams to be the cheapest but their BMS is internal.
Found the Expion 360 line that Airstream is selling and it's 120 Amps in a group 24 box/case whatever you call it. Also has an external BMS that is user serviceable should it ever fail. That got me interested. Anybody using them and what are your thoughts? It does weigh a couple more pounds presumably because there are a few extra cells to get 120 amps in that smaller 24 group box. They also have a monitor that does all of the same things as the Victron and everything is visible on the screen so it's not like the old Xantrex where you have to toggle through the pages. Thoughts?

[mchero]

This is what my 4 FLA house batteries are doing temp wise. Fully charged of course.
https://drive.google.com/file/d/1ji8QU-LaRebAoj002io733fJVdG4j-nZ/view?usp=drivesdk

7 deg. this AM. Happy Turkey day!

[Itinerant1]

Over the past month cycling between a SOC of 35%-85% on the 500ah lfp bank.
At 0630 making the second pot of coffee SOC at 37%, decided to hook up 1 2000w generator and let it go for 3 hours to see what it would dump into the batteries. This is the longest I've kept the generator running the Magnum charger in the past 31 months. Rain/ overcast in the forecast today and with excessive heavy microwave use and tv for Thanksgiving a generator boost is called for. I do hate listening to the generator even the "quite" ones. I'll take the roar of solar power any day.

Start 0650 SOC 37% (185ah)
Finished 0950 SOC 94% (470ah), 3 hours brought bank up SOC 57% or 285ah.

Yes the solar did help in charging of 40ah or 8% in that 3 hour period while watching tv, charging laptops, phones the normal everyday way of life items.

With minimal solar today that should carry the small loads and finish topping the batteries off. I personally like to get the lfp bank back full once every 30 days or so.

Enjoy the over indulgences of Thanksgiving day.

[Itinerant1]

Cydog15 I apologize for hijacking your thread with info pertaining to Lifepo4 batteries as a whole which you asked about granted not the " brand" you asked about. Once you do more homework you'll find out that the lfp batteries are basically the same what separates them will be the bms/ ems that protects them or allows for x amount of power to be used from them? Just remember when thinking about LFP think of the whole system not just the battery. 😉

[MEXICOWANDERER]

Good for an average .4 - .7 voltage drop.

No steenky bueno as a device that serves as 100% charge duty but works for float-only duty.

Make certain you know what you are doing as many ECU regulators drop to the high to mid-thirteens.

The silicon rectifier taps chassis battery (NOT alternator) power then sends the reduced voltage to the Lithium unit. This line MUST be disconnected when engine is not running as it does not serve as an on/off cutoff switch.

[camperdave]

What are folks doing about the alternator? In thinking about switching to LiFe04 for the house batteries, it seems straight forward from the house and converter side of things. But won't the alternator overcharge when driving? I don't want to float the battery at 14+ volts for 8 hours while driving if I'm leaving home with a full battery, right?

I could see a custom BMS triggered relay to isolate once charged, but that seems complicated and I don't recall reading about anyone doing that.

[BFL13]

I don't have Li and never will, but your post should be a good lesson for those who are looking at Li just because they can afford it.

If they are not also "hands on" kind of guys that like to keep track of things closely and get the necessary monitors etc needed, they will come to grief.

I wonder if the people who "cycle" their Li as you describe instead of floating them, believe they need "exercising" like other types of batteries do at times to keep them from going bad. I don't have a clue about Li

I certainly agree about the value of adjustable voltage chargers! I have been in that camp for a while now.

Thanks for taking the time to post all that interesting and valuable information.

[Itinerant1]

BFL13 wrote:


EDIT--BTW, I missed something about Li. I have seen they need 14.6 or whatever so eg, PD makes a special converter that does that instead of their usual 14.4. So why is your setting at 13.6?

OTOH, ISTR the 48v charger was for 54v and 54/4 = 13.5

Having a programmable charger is best.

Remember that my primary charging is all done by solar.
Settings: Bulk 14.1v, absorb 14.2v (10 minute event can't be turned off) I have only seen 14.2v twice this year in Feb., float 13.6v.
Note: I'm calling float under my circumstances as zero charging with solar carrying the loads during the day. Some folks with lfp charge to "their" 100% then turn off charging run batteries down and do over again when needed. Why waste good solar power?

The reason the charger is set as Float 13.6v is when plugged in for a shorter period of time, say at an rv park for a couple days or week. Even then we're living off the solar/ batteries a benefit that was built in when building the system of not having to be reliant/ needing the power cord and if we want to use the power hook up I'll set AC input to 50a or 30a on the me-arc settings depending on source go into the sub panel flip the breaker on for the water heater.

LFP doesn't need 14.6v. You have to decide what level of battery voltage you want to charge too knowing that it will yeild a particular level of capacity.
Meaning if 14.6v (3.65 vpc x4, 100ah) 100% manufactured specs.
I'm using 14.1v (3.52 vpc) which read 99% SOC as "my" full battery but on the battery it around 87-90% charged keeping it away from the upper danger area. I personally have never been below 28% SOC (72% DOD) which is still 12.8v (3.20 vpc) without large load. My inverter will shut down at 12.0v (first line of protection). I remember seeing 12.4v once inverting using the microwave for 4 minutes at that low of SOC. The bms will shut the system down if any cell drops to 2.90v (last line of protection).
With all that said you still have to reset SOC %, mine still happens using the lower voltage explained below by Elite Power Solutions, GBS Batteries.
The EMS system has a minimum recorded resolution of +/- 0.5A so any current below that level is not accounted for. The system could be setup for a finer resolution, but the shunt value would have to be reduced which reduces the systems maximum current capability. 
The system will reset the capacity to 100% whenever the pack voltage reaches 3.49 to 3.52 V/cell on average, depending on how it was programmed, and the pack current must be negative (charging) and typically under 35A and then it will set the capacity to 100%. Again, these are all firmware variables  so it's possible your system was programmed differently. You should continue charging after this point until the battery truly is full to have the reference point of 100% be correct. 
If you have many small loads that are not accounted for then you would occasionally need to re-sync the pack with 100%. The frequency at which you have to do this will vary depending on your application and usage.

My batteries are prismatic cells, 20 cells .

The drop in batteries it seems their bms or ems needs 14.4v -14.6v to reset the capacity % plus balance cells if needed. It won't hurt to charge to less but the SOC % will get out of wack.

I'm sure I left out some info or maybe could of explained better but hopefully get the jist.

[BFL13]

I think you are onto something, but not all questions are answered yet.

The generator still has to supply the 1708 above its 1600. I don't know if that is a problem for the Honda in real life. So far so good in your case. As noted, it doesn't get used that often anyway. Higher altitudes would reduce that ability somewhat.

On the output watts and the high amps, the 1515w is still quite high. Efficiency is defined as output/input watts. (They ignore PF, but here both PFs are 98-97 say)

Input watts with 1708VA and say 0.98PF is 1674w and 1515/1674 = 90%

I got 102 x 14.8 = 1510w out with 1854w in and 1510/1854 = 81%. The usual efficiency of these chargers is around 85%

I doubt the charger in the Magnum is way more efficient than my converter, but who knows?

The key might indeed be the Li battery. I do know a charger can do better if it is just supporting a battery, such as when the battery is being drawn down by an inverter and the charger (not on that inverter!) is providing input at the same time.

You get more amps from the same charger doing that compared with it charging a battery. ( to current limit) Perhaps the same effect is seen with charging an Li compared with a "normal" battery?

EDIT--BTW, I missed something about Li. I have seen they need 14.6 or whatever so eg, PD makes a special converter that does that instead of their usual 14.4. So why is your setting at 13.6?

OTOH, ISTR the 48v charger was for 54v and 54/4 = 13.5

[Itinerant1]

I was thinking about this this morning, you have DC set at 14.8v where mine is set at 13.6v? Resistance in batteries chemistries? Efficiency of charging Lifepo4. Some of the #s your using I don't understand. But when using 13.53v (battery voltage) x 112a that's 1,515 watts is that not within spec of the generator?
Eu2000i AC Output:120V
2000W max.(16.7A)
1600W rated (13.3A)

[BFL13]

Itinerant1 wrote:
No, that was Sept 23 in Black hills National Forest, South Dakota during a 5 day stretch of rain heavy overcast. I normally wait till the bank is lower (25-30%) before charging off the generator but with more days of rain in the forecast and it stopped raining that evening what better time to drag the generator out.

My 100 amp PF corrected charger (run from a Honda 3000) showed this on the Kill-A-Watt:

122.7v, 15.57a, 1910VA, 1854w, PF 0.97 doing 102 amps DC set to 14.8v

Your figures seem to show AC in is 122v at 14a = 1708VA

I am baffled how you can get 112 amps out from 1708VA when I am getting 102 amps out with 1910VA needed and both chargers are PF corrected.

1708/1910 x 102 = 91 amps, which is also about right for your Honda 2000 at 13.3 on the 125 amper. 13.3/18 x 125 = 92

How can you get 112 amps with a Honda 2000?

[Itinerant1]

No, that was Sept 23 in Black hills National Forest, South Dakota during a 5 day stretch of rain heavy overcast. I normally wait till the bank is lower (25-30%) before charging off the generator but with more days of rain in the forecast and it stopped raining that evening what better time to drag the generator out.

[BFL13]

Was any of that 112 when the gen was running from solar?

[Itinerant1]

This is after shutting the generator off that day. Started @ 7:19pm 56% soc (280ah), finished @ 8:04pm 70% soc (350ah) so in 45 minutes it charged 14% or 70ah. Now it's inverting at 13.2v with -12a load.

[BFL13]

You are claiming the Honda 2000 is supplying all the VA to run the charger at 112 amps?

I don't think a Honda 2000 can do that, even when the charger is PF corrected. ( I have done some work on that with my Kill-A-Watt on some gens and chargers, with and without PF correction)

OTOH you know your system and I don't. So it will just remain a puzzle for me unless some others on here can clarify. Thanks for taking the time to try and explain it.