What temperature is the battery held at. If it's pretty warm I would keep it at 50% if you can. Better thing to do is to use that power somehow. If it's a cheap small battery I would just run it hard.
Will Prowse says charging 0%-100% daily is a non-issue for lifepo4 battery longevity. Thoughts?
- Thread starter Speng
- Start date
No, its a home built with eve 304 cells in my truck camper. so normally when I camp in use about 1/10th to 1/8th of the power, depending how cold it is and how much the furnace is running at night, but the battery is in the space so room temp say 18C. verry very low C rates as I haven't installed an inverter yet, but even then the discharge C rate will never be over 0.3 and charge.. I thin the max I can do while camping is 0.07C. I can triple that at home if I plug it in and have the solar going haha so it is what you were talking about for the most part a solar that cycles in the top 1/8th of the battery capacity with the odd dip deeper when the weather is bad and there is no sun for a few days.
12VoltInstalls
life passes by too quickly to not live in freedom
My lfp batteries have only shut off once in two + years.
And I bought the batteries to use as I’m 100% offgrid
I just let the system run.
kw5kw
New Member
I have a "mix" of EG4 LL batteries (six 5120 wH ea) and 'off brand' (eight 14336 wH ea) for a total of 145,408 wH. These are wired together using a Victron Lynx power in and distribution buss bar system. These batteries do not communicate with each other.
I set my EG4 18KPV to run on voltage and to begin charging at 51.2 V (3.20v/cell) and off at 56.8V (3.55v/cell) using the grid if/when necessary. Now that it is winter, my first with this system, I'm getting way too much shading on my panels to completely charge daily in spite of having 16kW of panels. I need 20 more panels that would get full sun! Currently I am going 4 days between charging, then it takes nearly a day to charge my batteries. OR, I could perform a supplemtal charge a couple of hours (or so) at night and a couple of hours during the day. I have done both and can't quite decide which way actually works the best, I'm really leaning towards the daily supplemntal solution.
I am a bit OCD about low voltage and shutting my system down. I just can't go down to 48 volts before I start charging! I have a 24 volt system in my RV with two Lifepower batteries. They last just under 6 hours running one AC and the refrigerator while on the road... No solar on the trailer at this time (wife won't allow the holes). I know this because the first trip I had calculated the six hours and was right on time until we were delayed by a road construction project. [It] Delayed us enough that my system was dead when we got to the campground. I almost never got the system going again, It kept reading 12v from the converter not 24 v to get the charging going again. It took me a couple of hours to get it going again after fretting over it. It happened once again while at home in storage and I had the shore power off while setting up my 18KPV. This time I knew how to get it going again, but still not worth the hastle. I don't want to do the same with my 48v home system! Nope, not going below 51.2!
I set my EG4 18KPV to run on voltage and to begin charging at 51.2 V (3.20v/cell) and off at 56.8V (3.55v/cell) using the grid if/when necessary. Now that it is winter, my first with this system, I'm getting way too much shading on my panels to completely charge daily in spite of having 16kW of panels. I need 20 more panels that would get full sun! Currently I am going 4 days between charging, then it takes nearly a day to charge my batteries. OR, I could perform a supplemtal charge a couple of hours (or so) at night and a couple of hours during the day. I have done both and can't quite decide which way actually works the best, I'm really leaning towards the daily supplemntal solution.
I am a bit OCD about low voltage and shutting my system down. I just can't go down to 48 volts before I start charging! I have a 24 volt system in my RV with two Lifepower batteries. They last just under 6 hours running one AC and the refrigerator while on the road... No solar on the trailer at this time (wife won't allow the holes). I know this because the first trip I had calculated the six hours and was right on time until we were delayed by a road construction project. [It] Delayed us enough that my system was dead when we got to the campground. I almost never got the system going again, It kept reading 12v from the converter not 24 v to get the charging going again. It took me a couple of hours to get it going again after fretting over it. It happened once again while at home in storage and I had the shore power off while setting up my 18KPV. This time I knew how to get it going again, but still not worth the hastle. I don't want to do the same with my 48v home system! Nope, not going below 51.2!
sunshine_eggo
Victron's little biatch
Personally, in these conditions, I would prefer to charge a smaller amount daily and to start at higher states of charge to retain the backup duration, since you have unfavorable PV conditions.
Example:
You're charging once every 4 days , so let's say, you're losing 20% per day. You get down to 20% after day 4 and then spend the next day charging to full. Why not charge from about 80% to 100% (whatever voltage that works out for you) every day instead? Same amount of total charging but done daily for shorter times and never letting the battery get below about 80% for when things go south and all you have is PV or generator.
Being OCD about avoiding BMS cut-off is good. Stay the course.
kw5kw
New Member
Yes, this is what i was thinking as well, I could use this strategy from November through February and then go back to my ,more normal, voltage settings. By the end of February my shading issues should be mostly mitigated.
Thanks.
DougfromdaUP
Solar Addict
I don't discharge below 51.2 volts either, but only to save some energy for the occasional utility problems, not because I'm trying to save battery life.
Kudos to Will for reading and posting about what he's learned.!
Kudos to Will for reading and posting about what he's learned.!
OffGridForGood
Catch, make or grow everything you can.
I am with you neighbour - winter months are the most likely (by far) to be when we get a power outage, also when it can be the most damage caused by lack of power available!
I like to keep a close eye on the weather forecast, and any crappy stuff heading my way is a signal - time to make sure the ESS is powered up just in case of an outage. Better to be safe than sorry.
wpns
Solar Joules are catch and release
Strangely, there was no response to this.
DVD
New member and getting older
I’m of the same thinking as Will and others. 0-100% is normally not a problem. Certainly not for the battery.
Potential problems can arise with the overall system when the batteries LVP disconnect and the system isn’t designed well.
Potential problems can arise with the overall system when the batteries LVP disconnect and the system isn’t designed well.
Do I need to watch the video again to get the answer for what is 0%? The title says it but did I just miss it in the video? My batteries, which I don’t have yet, stop discharging at 2.9v according to the specs in the user manual, but the manual is weird in saying SOC < 15% OR cell voltage < 2.9v. There’s no way that 2.9v is 15% SOC. Their literature also says DoD “up to 100%”. What the heck does that mean? 2.9v?
In the cell data sheets, 0% is 2.5V. At 2.9V, you're pretty close to 0% - in fact, there is very little energy in a cell left once you hit 3.0V.
I've been using my 2 EG4 rack mount 48v batteries for a while. Not really pushing them real hard. Recharge at around 45% disconnect around 95%. The other day I was down at <45%, very mild load. Maybe 10 15a load. The batteries went into cell low voltage alarm on just a few cells. Apparently quite a bit out of ballance. So trying to top ballance now. Slow going at the top. One or 2 cells will hit the OV cutoff, while others are still quite a bit below 3.5v. 3.625v-3.456v. They settle out at around 3.3334v with very little difference overnight.
Is there any way to set the BMS to top ballance charge mode to disconnect the charging if cells get say 0.01v out of ballance from each other? Or some other possibly more reasonable amount? Or is 0.2v difference, under charging conditions considered as acceptable?
DougfromdaUP
Solar Addict
200mV difference isn't acceptable.
You've got to charge your batteries to a voltage high enough to let the balancer start working or this will continue to get worse. Why stop at 95%?
Also, since you never charge or discharge your batteries enough the bms' estimate of SOC is certainly way off.
I've had LiFePower4s for over two years, and even their wimpy passive balancer does a good job if it can work a little while most days.
wattmatters
Solar Wizard
Mine are there to be used. Here's the SOC of my LiFePO4 over the last 30 days:
Mine won't go below ~ 8% as they are in a hybrid set up with some sealed lead acid, so as LiFePO4 SOC gets low, the SLA picks up the slack giving the LiFePO4 a soft landing. I only discharge about the top 5-10% of the SLA - those are (cheap) reserve capacity.
Mine won't go below ~ 8% as they are in a hybrid set up with some sealed lead acid, so as LiFePO4 SOC gets low, the SLA picks up the slack giving the LiFePO4 a soft landing. I only discharge about the top 5-10% of the SLA - those are (cheap) reserve capacity.
wattmatters
Solar Wizard
I have Solar Assistant integrated with Home Assistant. In HA I have InfluxDB to store the data and Grafana for charting.
Fancy. I’m probably heading that direction since I seem to be obsessed with monitoring everything. I’m sure if I had any idea what I’m getting into I wouldn’t start, but I’m retired with an abundance of free time, and I need a hobby, so it’s likely the natural progression from where I am now.
wattmatters
Solar Wizard
Home Assistant will fill the void.
Because that's where it had gotten to when it was time to leave. I found out that "meh, close enough, actually wasn't. But, when trying to reconcile this mistake. The EG4 didn't exactly want to get top balanced. The OV Warning and shut off would drop the Charge MOS off, with some cells at 3.65, and others spread out to 3.375. It takes quite a while for the bms to normalize all 16(×2) cells back to 3.337 volts (overnight). Then hit it with the charger again. But the low cells are coming back up. Slowly. They were at 3.425 volts this last time before the OV Cutoff. It just may take a few days cycling the pack like that to get there. The packs report 100% at cutoff, even with the low cells. And 99% in the morning after normalizing.
I only realized that the batteries were badly out of ballance when they went into LV Cell Cutoff at 45% SOC, to 0% SOC in a matter of minutes with very little load.
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SolarCzar
New Member
I am reading this thread with great fascination. I've asked Signature Solar some questions that I can't get a definitive answer on...
1) The EG4 PowerPro states 8000 cycles @ 80% DOD. Does that mean if my batteries are used down to 10% SOC, that I'm in warranty violation? What happens in an outage in the middle of the night and my batteries are set by default for off-grid cut-off at 0% SOC, will this trigger a warranty violation?
2) From EG4 opinion...is using the PowerPro down to 10% SOC present a technical problem irrespective of warranty? Meaning, am I anticipating a loss of longevity or potential damage?
For now, to be safe, I've moved back to 20% SOC. I can just about pay for the batteries with an extra couple hours of battery usage per day over the course of the battery's 10yr warranty period. It's that meaningful, so it's an important question.
Thanks guys
1) The EG4 PowerPro states 8000 cycles @ 80% DOD. Does that mean if my batteries are used down to 10% SOC, that I'm in warranty violation? What happens in an outage in the middle of the night and my batteries are set by default for off-grid cut-off at 0% SOC, will this trigger a warranty violation?
2) From EG4 opinion...is using the PowerPro down to 10% SOC present a technical problem irrespective of warranty? Meaning, am I anticipating a loss of longevity or potential damage?
For now, to be safe, I've moved back to 20% SOC. I can just about pay for the batteries with an extra couple hours of battery usage per day over the course of the battery's 10yr warranty period. It's that meaningful, so it's an important question.
Thanks guys
Does the inverter keep track of depth of discharge? I doubt it, so there’s no way for them to know how often you discharge to below 20%. You can be damn sure everyone is going to use all of the capacity when the power goes out.
wattmatters
Solar Wizard
Is that a warranted performance, or just a performance statement?
This is where is doesn't make sense to me. 8,000 cycles in 10 years is an average of 2.2 cycles/day. That would be an unusual use case.
robbob2112
Doing more research, mosty harmless
wpns
Solar Joules are catch and release
pretending that I didn’t want to spend 18 minutes of my life that I will never get back watching this guy yammer on and navel gazing, is there a TL: DR?
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