Going from flooded to LiFePO4….. And upgrading…..

[LithiumCanuck]

Ok…. First real post on this forum…. I hope I placed it where it should be… (love this forum and members btw )

I have off grid cabin with this solar setup:

4x 275W panels
4 x 6V 430 Ah batteries = 24V, 430 Ah
Epever 4215BN charger
Edit: my 120V charger is a Samlex EVO-4024

My batteries are dying and I will replace them with with LiFePO4 ones. In the process, I want to increase the capacity to avoid having to use the generator during rainy days and winter. I know that I willl get more just by switching to 24V 400 Ah Lithium, but “more” is not enough.

I was thinking of using 3 x 24V 200 Ah in parallel to increase to 600 Ah but I don’t want to add panels. Adding panels would be a real pain since I am surrounded by large trees and I don’t use much electricity ”most of the time“ anyways. I live north and while charging at low C during summer, I charge at very low C during winter for a shorter period of sun. This should not be a problem since I go to my cabin every one or two weeks And if I ever get two weeks of clouds, I still have my generator…

I am not worried about capacity but I want to make sure that I will not damage the batteries in a long run charging at a very low C…. I already killed my lead batteries because of my abusive usage in winter, I don’t want to destroy a second set lol.

(Regarding low temp, I intend to keep the basement above freezing starting next year )

I am open to any comment or suggestions !!!

 

[Greendream]

LFP batteries will charge with any current coming into them. My 48v LFP batteries ran in parallel can accept 1-100A current with suggested charge current of 50A though I believe the C rate is a bit higher running them in parallel. With 3 batteries in the bank they generally don't see more than 25A current each, while peak sun. We have 345AH @ 48V but wish we had a little more during cloudy days. We also over-paneled for this reason. 4.8KW of panels charging 15.3KWh battery bank.

 

[Steve_S]

Welcome to the forum.
You can easily swap in 24V/600AH for what you have now. I'd suggest 2x 24V/304AH in parallel, as that is more cost effective and simpler.
16 cells, + 2x 8S BMS + 2x 200A fuses.
Low C-Rate charging is no problem for LFP but a good Kick in the Pants every once in a while is good for them. They are 99% efficient at normal temps and therefore they charge faster than ol Lead. With your current amount of Panel & Charge capacity, you'll never charge 400AH let alone 600AH to 100% SOC.

Couple of things to keep in mind...
A 304AH pack would be capable of providing 304A for 1 hour and taking 152A charge for 2 hours but that does not mean it should. Also by Paralleling the packs you are immediately dividing load & charge which is just less energy moving to/fro each pack.
Because LFP is so much more efficient and capable of taking a higher charge rate, even charging by Generator will provide greater actual runtime from the batteries.

I changed from Lead to LFP a while ago, am up in the Algonquin Park area of North Ontario. Cold Cloudless & snowy days are normal. Oivey ! (And really freaky days like today). I can charge by Genset pushing 120V/23A from Genny on the L5:30 port through my Inverter/Charger & charge at 24V/75A for 8 hours which in turn gives me 3.5 days runtime off battery, bit more if I go into frugal mode. I have a 1190AH/30.4kWh LFP Bank. That is of course on a zero Sun Input day.

The REALLY Important thing with standard LFP is that you cannot charge them below 0C Temp and no more than 0.25C-Rate till 10C Temp after that you can go up to 0.5C-Rate.

As for being in the bush, I live here off the grid smack in the middle of nature... Sometimes a couple of select felled trees makes a difference. Maybe using an adjustable Ground Mount or other options may be available to consider.

PS: I am also using a Midnite Classic 200 & Samlex EVO-4024 with E-Panel in between.
Samlex Charge Profile #2 "3 Stage Type-2" (Lead Acid Battery Type selected) temp sensor to Lithium thing not needed*.
Absorb is set to 27.45V "Actual" at battery terminal (27.75 @ Inverter due to line drop)
Float is set to 27.20V "Actual" at battery terminal (27.50 @ Inverter due to line drop)
“ABSORP EXIT AMPS" is set to 14A in my case using Highest AH Pack in bank 280AH X 0.05 = 14A.

* The temp sensor line can be used with a Relay Based BMS to turn charging/inverting on/off but this is for One BMS or a centralised advanced managed BMS system. see docs for extended discussion.

NOTE: Check Voltage at Battery Pack & compensate for voltage drop with Inverter Programming.
Program Inverter settings during CHARGING to see the actual real difference.
ALSO when NOT charging, just Inverting, program cutoff & alarm points again compensate for the difference/drop between battery terminals & inverter. The Differential during Charging with Inverter & Discharging IS DIFFERENT !
I "Alarm at 22.20" and cut off at 22.0V and allow a 30 Second Delay for Load Sag which can trip & shutoff inverter when low.

Hope it helps, Good Luck

 

[fratermus]

I want to make sure that I will not damage the batteries in a long run charging at a very low C…. I already killed my lead batteries because of my abusive usage in winter, I don’t want to destroy a second set lol.

Off Grid Garage on YT has done a lot of testing with LiFePO4 charging to various voltages at various C (including very low C).
My takeaway based on his tests is that low-C charging is a non-issue, but tends to stuff in more amps when charging to any given voltage setpoint.

 

[chrisski]

Can you program the charging voltage in the EVO 4024 to the tenth of a volt? If so that’s perfect.

I have a charger that will charge at 28 volts on a GEL setting, but higher on a Lithium setting 28.8. These voltages are pre-set with dip switches, so if I ever need to use this I will manually turn the charger on, and when I get enough amp hours back to make it through the next day, I manually shut the charger off. I have found for normal day to day charging 27.6 volts from the SCC is not enough, does not quite charge to 100%, but when I upped it to 27.8, I get 100%.

Charging lithium to 29.2 is 3.65 volts the max per cell, and probably not wise. Some battery chargers I’ve seen exceed that.

 

[LithiumCanuck]

Welcome to the forum.
You can easily swap in 24V/600AH for what you have now. I'd suggest 2x 24V/304AH in parallel, as that is more cost effective and simpler.
16 cells, + 2x 8S BMS + 2x 200A fuses.
Low C-Rate charging is no problem for LFP but a good Kick in the Pants every once in a while is good for them. They are 99% efficient at normal temps and therefore they charge faster than ol Lead. With your current amount of Panel & Charge capacity, you'll never charge 400AH let alone 600AH to 100% SOC.

Couple of things to keep in mind...
A 304AH pack would be capable of providing 304A for 1 hour and taking 152A charge for 2 hours but that does not mean it should. Also by Paralleling the packs you are immediately dividing load & charge which is just less energy moving to/fro each pack.
Because LFP is so much more efficient and capable of taking a higher charge rate, even charging by Generator will provide greater actual runtime from the batteries.

I changed from Lead to LFP a while ago, am up in the Algonquin Park area of North Ontario. Cold Cloudless & snowy days are normal. Oivey ! (And really freaky days like today). I can charge by Genset pushing 120V/23A from Genny on the L5:30 port through my Inverter/Charger & charge at 24V/75A for 8 hours which in turn gives me 3.5 days runtime off battery, bit more if I go into frugal mode. I have a 1190AH/30.4kWh LFP Bank. That is of course on a zero Sun Input day.

The REALLY Important thing with standard LFP is that you cannot charge them below 0C Temp and no more than 0.25C-Rate till 10C Temp after that you can go up to 0.5C-Rate.

As for being in the bush, I live here off the grid smack in the middle of nature... Sometimes a couple of select felled trees makes a difference. Maybe using an adjustable Ground Mount or other options may be available to consider.

PS: I am also using a Midnite Classic 200 & Samlex EVO-4024 with E-Panel in between.
Samlex Charge Profile #2 "3 Stage Type-2" (Lead Acid Battery Type selected) temp sensor to Lithium thing not needed*.
Absorb is set to 27.45V "Actual" at battery terminal (27.75 @ Inverter due to line drop)
Float is set to 27.20V "Actual" at battery terminal (27.50 @ Inverter due to line drop)
“ABSORP EXIT AMPS" is set to 14A in my case using Highest AH Pack in bank 280AH X 0.05 = 14A.

* The temp sensor line can be used with a Relay Based BMS to turn charging/inverting on/off but this is for One BMS or a centralised advanced managed BMS system. see docs for extended discussion.

NOTE: Check Voltage at Battery Pack & compensate for voltage drop with Inverter Programming.
Program Inverter settings during CHARGING to see the actual real difference.
ALSO when NOT charging, just Inverting, program cutoff & alarm points again compensate for the difference/drop between battery terminals & inverter. The Differential during Charging with Inverter & Discharging IS DIFFERENT !
I "Alarm at 22.20" and cut off at 22.0V and allow a 30 Second Delay for Load Sag which can trip & shutoff inverter when low.

Hope it helps, Good Luck

Thanks a lot for all this useful information!

I spoke with Amy concerning LFP cells but she said they can no longer ship to Canada over sea…. They have to ship by plane. That killed my DIY project. I was thinking of buying 3 EG4 rack mount batteries if I can’t find cells at a decent price.

Thanks for the settings, this will be helpful as well. Concerning the trees, I have two very big and old trees near my cabin and cutting them would break my heart. I could eventually place a 50’ pole at 100’ from the house buy I think a larger battery bank will be more easy to install and also cheaper.

BTW, thank you for your contribution to this forum. I read lots of your posts and they help a lot.

 

[LithiumCanuck]

Off Grid Garage on YT has done a lot of testing with LiFePO4 charging to various voltages at various C (including very low C).
My takeaway based on his tests is that low-C charging is a non-issue, but tends to stuff in more amps when charging to any given voltage setpoint.

I will sure have a look at his channel!

Thank you

 

[LithiumCanuck]

Can you program the charging voltage in the EVO 4024 to the tenth of a volt? If so that’s perfect.

Just looked at the manual…1/100…. Probably very useful if you’re using silver wires. Lol

 

[Steve_S]

The 4024 CAN do charging up to 100A !!! BUT !!! It will run Really HOT and if you can forget passthrough.
During my Thrash Tests I pushed the EVO to 100A for one of the test runs and while it took it, it was not pleasant I did, however, discover that the "sweet spot" is between 65-75A while using Passthrough power as well.

Regarding Amy / Luyuan & Shipping to Canada (All Vendors ATM, not just Luyuan)

Logistics companies are temporarily unable to ship batteries to Canada, just because at present there are very few containers to Canada and the price is very high, so they suspend accepting packages to Canada. After this situation alleviates a little, they will recover that.

Till now, we still have several Canadian orders that have not been sent yet, and we are asking more logistics companies whether they can send, even if higher cost, for us, it is urgent to send out these packages before the holiday.

I spoke to my own S&H contacts as well and yes, at this time BC is blocked up and has put a hold on shipping till backlog is cleared. The damned roads & rail lines being washed out did it... It was just ticking along and managing and that 3 weeks of kerfuffle from the wash outs pushed it over the edge... Luckily it's not as bad as the US so hopefully it (backlog) will be cleared sooner than later.

Even Air-Freight slowed up a little once things get to Anchorage as things are getting terribly backed up there too. It's all a domino effect.