Don't set the Float Voltage too high! Graph to show perfect float voltage..

You bought a 12v Lifepo4 battery and are not sure what to set your solar charge controller to when it comes to Bulk / Charge voltage and Float Voltage? I believe this will give you a better understanding.
Items in this video:
Timeusb 12.8V 50Ah Pro LiFePO4 Battery, 4000+ Cycles Times Battery with Grade A Battery Cells, Built-in 50A BMS, Perfect Deep Cycle Lithium Battery for Solar System, Home Back Up, RV, Caravan etc
Timeusb website: www.timeusbpower.com/?ref=ymw...
Timeusb Amazon link: amzn.to/42xrMZi
LeTkingok EBC-A20 Lithium/Lead Acid Battery Capacity Tester Charge 5A Dischage 20A Electronic Load (EBC-A20)
amzn.to/3HEyFys
_________________________________________________________________________________________
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Thanks!
#12voltbattery #LifePo4 #offgrid

[@Paul_______]

It's not just about AH remaining, it's about balancing the batteries. I'm now sitting at 61kw of LiFePo4. I was charging at 3.45v per cell. It worked well for a few months but I noticed when I get low on charge that my packs will get up to 300mv difference. I've increased charging to 3.50v per cell and the issue went away. You want to get into the steep part of the curve but not max out. I run two houses full time with these batteries. For those with pre-made packs it's 14.0v bulk 13.4v float, 28v bulk 26.8 float, or 56v bulk 53.6v float

[@OffGridBasement]

Thank you for the information and the comment.

Hello, just wondering which cells you have and the BMS?? Some have a setting to equalize when charging and when you turn that off it equalizes all the time and does a better job of keeping the variation low.. I bought 2 with active balance that does up to 2 amp transfers between cells..

[@Paul_______]

You only want balance to start when the cells reach 3.45v/cell. For my 24v system I still use 28.0v bulk, 26.8v float, balance start at 3.45v/cell. I'm using eve cells sold by Gobelpower and 2a jk bms

[@junkerzn7312]

Note that the vendor specifications for a lot of these fly-by-night brands are just plain wrong. Often these vendors don't even know how the BMS in their own battery is programmed. For LiFePO4, if you don't have control over the BMS settings, you generally always want to charge to 14.2V (3.55V/cell). The reason is not to try to get the battery to 100%. That has nothing to do with it. The reason is that the BMS may not start balancing the cells internally at a lower target voltage and if the BMS's balancer is not operating, the individual cells will go out of balance and some of them will wind up at 3.65V (the BMS cut-off) despite you having that lower target voltage. Because of this, 14.2V is generally the best choice. 3.50V/cell (14.0V) is also a fairly safe bet. But lower than that is not a good idea. i.e. you can wind up putting more cycle wear on the battery with your lower target voltage than with a 14.2V target. So this is why you pretty much always want to charge to 14.2V. Don't worry about cycle life, charging to 14.2V won't hurt the battery. Discharging the battery all the way to BMS disconnect will put far more cycle wear on the battery than charging it to 14.2V will. Like an order of magnitude more. -- Now, for float, the float ALWAYS must be set to 3.35V/cell to 3.375V/cell. That is, 13.4V to 13.5V. NO EXCEPTIONS! This is the voltage range where load support can be provided without discharging the battery (for example, in a solar application), while at the same time not being so high that the battery continues to charge while sitting at that voltage. This is also the voltage range which puts the least amount of wear on the cells from sloshing around as the load changes and the charge controllers try to match it. If the float is set higher it will continue charging the battery, ultimately overcharging it. If the float is set lower, it will discharge the battery and also the sloshing from the load-following the charge controllers do will put more wear on the cells. -- If you are still worried about charging the battery up to 14.2V you can always take a little off the top after charging is completed by putting a load on the battery for a minute or two. If the battery is permanently connected to an inverter or a system that always has some load, even if only very small, you don't have to worry about it at all because the battery will more or less immediately drop to near the float due to that load, after charging has stopped. -- In terms of attempting to charge to a particular SOC below 100%... its a bad idea, because the BMS will generally not be able to balance its cells internally if you charge to a lower SOC. For discharging, if you can control when to turn off your loads it depends massively on the amount of load. For light loads (up to around 0.3C), a 12.0V floor gets you 95% of the battery. For heavy loads you can go lower. The issue with discharging is that discharging all the way to BMS cut-off, repeatedly does an ORDER OF MAGNITUDE more damage to the cells than anything else you could possibly do to the battery. Its ok to do it, it won't destroy the cells, but you are putting a lot more cycle wear on the cells by discharging them that low. Also, if you fail to charge the battery in a timely manner (like fir a week or two) after it has been discharged to that degree, you risk the cell self-discharge from taking the cell voltage into territory that will significantly damage the cells. LFP batteries are far, far more likely to be destroyed by over-discharging them / letting them sit while discharged, then by "overcharging" (holding them at a charging target voltage for days or weeks on end). Holding the battery at the float 24x7 is fine, but in that case choose the lower-end of the float spectrum. 3.35V (13.4V). And in solar applications you generally don't have to worry much at all due to the cyclic nature of the charging and discharging. -Matt

[@jws3925]

Perfectly stated!

[@OffGridBasement]

Thank you for spending the time to give us all of that great information!

[@atburke6258]

Notice that some vendors that claim1.0C as the charge rate in their instructions now recommend 0.2C on a regular basis and a max of 0.5C. They learned from claims and angry comments about early failure.

Thanks for your test information.. I am building a monster dual 15kw 48v battery for 30kw at a top charge of 58vdc using 17 LiFePo4 EVE cells and have been watching quite a number of videos to basically learn the craft.. Still trying to settle on the top charge per cell between 3.4v and 3.5v with a bottom of 2.9 to 3vdc.. My 8kw inverter can accept an input between 40 and 64vdc so if I keep the voltage higher it will make more power for less heat because as the volts get lower the amps get higher and amp flow is heat.. Bought 2 JK BMS that are the slightly older version but have the 2 amp active balancer which allows the bypass of the stringing cells and charging them to 3.65v to get balanced cells.. Instead I will check all cells to make sure they are similar 3.0 to 3.2 near the bottom then assemble the pack, setup the BMS and controller and gradually walk the battery to 3.6v per cell to get 61.2v over a couple of days as the active balancer levels out the cells.. Once top balance is achieved I will back the voltage down to that undecided operational level.. As for the float voltage from the charge controllers I am thinking that I will set it just a couple tenths of a volt lower so during the day the solar panel production once the battery is full will handle as much of the loads as they can and to prevent micro charge cycles..

[@OffGridBasement]

Your plan looks good. Getting all the cells to top balance is key. Enjoy your huge setup! Thanks for the comment.

[@americansafarico]

Fantastic. Needed this .

[@OffGridBasement]

Glad it was helpful!

[@jws3925]

I know you watch Andy at Off Grid Garage and he has done a deep dive on this subject. He initially set his charge voltage approximately where you were at (3.4--3.45 per cell). I believe he has since changed that to a slightly higher value due to the balance function of the BMS. Everything you have presented here agrees with what others have found out about this chemistry. LifePo4 is so interesting and makes one re-think everything we learned about batteries (lead acid) over many decades.

[@OffGridBasement]

Andy's channel is great and I watch it all the time! Thanks for the info and the comment!

[@dollylaning1613]

Thank you for the information. You definitely want your batteries to have the longest life possible. Thank you for the video!

[@TheRenoir]

I too have watched most of Andy's vids on LifePo4. He did some extra vids after commenters mentioned balancing would be easier with slightly higher voltage. His tests I believe did not confirm this. I think he sticks with 3.45v per cell(13.8) and recommends an active balancer over the lower amperage passive balancer built into most BMS. It's a very interesting topic. I bought the same tester/discharger/charger. Pity it's only 5A charge at 13.8 odd volts. I now parallel charge a 10A and 20A charger and finish off with the EBC unit as its programmable to stop at a set current. Great unit to have for around $100.

[@garyenwards1608]

Im using an EPEver 40 amp charge controller on my 200amp 12 volt Ampere Time battery. I had it set to Bulk 14.4V for 30 mins yesterday and Float 13.6V. Today I turned it down to 14.2Bulk 30 mins and 13.6V Float. Im going to turn it to 14.4V Bulk once a month so the BMS balances the cells once a month. Im on the fence about Floating at 13.5V or 13.6V. The only load is a mini fridge. Its plugged into a Xantrex Prosine 1000watt that Idles at 1.5watts in Power Save Mode and the compressor kicks it out of that mode 1/3rd of the time to run the compressor.

[@jamesfalvey77]

Thanks for the valuable info

[@OffGridBasement]

My pleasure. Thanks for the comment.

[@dougiee6589]

Useful findings which I need observe with 24V

[@OffGridBasement]

Glad I could help. Thanks for the comment.

[@Zirrad1]

Thanks for this. The float voltage needs to be at a level where your solar panels will kick-in to provide power rather than the batteries. I use the "Equalize" setting on my charge controllers to occasionally ensure the BMS in the fully charged batteries will have the voltage to run its top balance program

[@OffGridBasement]

Thanks for the comment.

[@garyenwards1608]

I was just thinking of trying this on my CC. What type of CC are you using? Does it Equalize once a month? I dont see a schedule or time adjustment for the Equalize setting on my EPEver CC. Im using an EPEver 40 amp charge controller on my 200amp 12 volt Ampere Time battery. I had it set to Bulk 14.4V for 30 mins yesterday and Float 13.6V. Today I turned it down to 14.2Bulk for 30 mins and 13.6V Float. Im going to turn it to 14.4V Bulk once a month so the BMS balances the cells once a month. Im on the fence about Floating at 13.5V or 13.6V. The only load is a mini fridge. Its plugged into a Xantrex Prosine 1000watt that Idles at 1.5watts in Power Save Mode and the compressor kicks it out of that mode 1/3rd of the time to run the compressor.

[@dan32one44]

You should bring them up to 14.4 at least once a month to balance the BMS.

[@OffGridBasement]

Thanks for the comment.

[@mortimersnerd801]

....for me that's easy, I use the same battery, a TimeUSB 50 ah and a Renogy solar charger... just set the Renogy on LI default about once a month.. quickly goes to 14.4...but on user setting 13.8-14 for the rest of the month... I use mine for a solar powered a ham radio setup so absolute max AH available is not critical.

[@SolarResurrection]

Good Revision, I set mine to 27.6 volts.. I just got a new MPPT, Happy with Y&H 100A MPPT Solar Charge Controller 12V 24V 36V 48V Max 100V Lithium...30 bucks cheap but nice big screw fixing holes...3 x 375 working fine. I tried expensive Victron but 100/20 but kept blowing fuses even with 1 375 panel. So, I returned it. Think I am set for summer now.

[@OffGridBasement]

That's excellent! I can't wait for the summer sun to return. Thanks for the comment.

[@petersimms4982]

I just charge mine to 80% & it’s fab 😊

[@OffGridBasement]

Thanks for the comment!

[@atburke6258]

Yes, a good way to not stress a battery.

[@OffGridBasement]

Thanks for the comment.

The LiFePo4 cells are far more durable when stressed at the top and bottom than the older Lithium Ion formulas so charging is less critical but as he showed you gain very little when pushing the limit..

[@atburke6258]

Yes, the chemistry should give LIFEPO4 an edge if build quality is the same. But we have not had consumer grade LIFEPO4 cells on line long enough to draw a valid conclusion.

[@shelley131]

I enjoy your informative video a lot. I've been thinking of building a diy 12V portable power system just to learn possibly using a 1500W inverter and 2 or 300ah battery. My question is what amperage charger should I buy 30A, 40, 50A?

[@OffGridBasement]

Lifepo4 batteries like to charge at 20% of the total ah capacity. 20A charger for 100ah battery... 40A charger for 200ah battery and so on. Anything that is slower is totally fine. Hope this helps! Thanks for the comment.

[@mannyfragoza9652]

According to the Jackery web page 13.6/3.40 rest voltage is 100% charged

[@junkerzn7312]

Any LiFePO4 battery can be fully charge to 100% if held at any voltage above the float range for a long enough period of time. Generally that means 3.40V/cell or higher. However, the amount of time you have to hold the battery there is variable. If you stop the moment it hits 3.40V/cell (13.6V), even after waiting for the current tails off, the battery is probably not fully charged. The main problem with using low voltages like 3.40V as a target is that the BMS probably won't balance the battery's cells internally at that voltage. So you wind up doing more damage to the battery rather than less as the cells go out of balance. For example, an out of balance battery held at 3.40V might have cell voltages of: 3.35V, 3.35V, 3.30V, 3.60V. An addition problem with using a low charge target is that at a high charge rate (e.g. 0.4C+) you will reach that target long, long before the battery gets anywhere near 100%. Like you'll hit it at 70% or even 60%. And with the current tail you might reach 80%. Also, once the cells have gone out of balance you can start to lose capacity at your lower target voltage because some of the cells will not reach anywhere near 100%. -- If you have full control over the BMS settings, you CAN charge to a lower voltage by ensuring that balancing starts at e.g. 3.40V and then using a 3.45V charge target. However, this only works well in warmer temperatures. In cold weather you definitely want a higher charge target, regardless. Most batteries that do not give you access to the BMS don't balance at that low a voltage and you need to charge to 3.50V/cell or 3.55V/cell (14.0V or 14.2V) to be certain you are engaging the battery's internal balancer. -Matt

[@mannyfragoza9652]

@@junkerzn7312 good stuff

[@OffGridBasement]

Thanks for the info and the comment.

[@realeyesrealizereallies6828]

Why do the wires come out of the top instead of the bottom and under ground in conduit..

[@OffGridBasement]

I honestly don't know what you are referring to.

[@realeyesrealizereallies6828]

@@OffGridBasement You don't see the wires coming out of the top of your outside battery enclosure, it's probably the only visible wires in the video..They should come out of the bottom, run into under ground conduit and run into the house..