EVE Cell degradation.

[ppzzus]

I live in my bus half the year, other half is in a regular house. I run a 24v system with epever mppt charge controller, 900w in panels, current connected bms. 8x eve 3.2 v cells. I stay in southern California during the winter so sunshine generally isn't a problem.

Last year I was able to run pretty much everything I wanted with no need for power conservation. I was gaming on my PC, running a mini fridge, wifi, etc. Generally it was a set it and forget it type setup. Got to CA last week and now I'm suddenly facing a power crisis.

I wake up yesterday morning and I'm in the low 25's, never seen that before. I'm watching the voltages and it goes up to low 26's. Normally it would hit low 26.5 then by the next morning I'd be at 26.1. Before I go to bed I hit 25.5 and by the time I wake up I'm dipping into the 24's. I e never seen it gets that low before and I've never had an issue with running them low.

Today the sun was out and I see the power move to 26.5, 5ish hours of charging @ 15-20 amps. 2 of 10a, then 2-3 more @ 5a or so. I didnt run anything but the mini fridge and wifi. Watched the power drop like a stone from 26.5 to 26.1 over 3 hours.

I currently have a plug in power meter on order, forgot mine. Going to do some testing with the power meter to see if anything is drawing way more power than before. I did leave home with around 25.5v in the system. I didn't feel comfortable having the panels on since it dipped below freezing in the morning. Didn't turn them on until I got out west and the temps were good.

Also my 4th cell seems to be a bit of a quitter and drops much faster than the others. Do y'all think my cells have degraded? They were of the AliExpress variety, but are only 12 months old. What are my options for cells these days? I know the lifepo4 world moves pretty fast. Cells also show no signs of bloat. Only thing I can think that's changed is adding a 12v 20a power supply for the heater that I only used a few times, will the power supply draw that much even if the heater isn't in use?

 

[Bud Martin]

"Today the sun was out and I see the power move to 26.5, 5ish hours of charging @ 15-20 amps. 2 of 10a, then 2-3 more @ 5a or so. I didnt run anything but the mini fridge and wifi. Watched the power drop like a stone from 26.5 to 26.1 over 3 hours."
20A @ 26.5V = about 500W of charging from 900W of panels. Did you see > 20A of charging last year? What is the spec of the Solar charge controller charging current? 20A? 40A?....
How many panels and how are they wired up? May be now you are getting less power from panels than last year due to bad connections?
What is you battery rating 280Ah?
Do you have clamp on DC Amp meter to check the current draw from battery?

 

[ppzzus]

"Today the sun was out and I see the power move to 26.5, 5ish hours of charging @ 15-20 amps. 2 of 10a, then 2-3 more @ 5a or so. I didnt run anything but the mini fridge and wifi. Watched the power drop like a stone from 26.5 to 26.1 over 3 hours."
20A @ 26.5V = about 500W of charging from 900W of panels. Did you see > 20A of charging last year? What is the spec of the Solar charge controller charging current? 20A? 40A?....
How many panels and how are they wired up? May be now you are getting less power from panels than last year due to bad connections?
What is you battery rating 280Ah?
Do you have clamp on DC Amp meter to check the current draw from battery?

20a seems to be about average compared to last year. I believe the max output of the panels output about 29.9a total at peak output (combined). 3x 315w panels in series. Charge controller is the 40a mppt controller, 4215nb iirc. I actually didn't redo any wiring between last year am now, which is why I'm so confused. Ill check all my connections to be sure, I was pulling my charge figures straight off the BMS app so if there was poor connection it would be between the BMS and the battery itself.

Might be on the right track, it's a 2200 Mile drive to socal, lots of vibrations. I did use red loctite on all my battery connectors though.

 

[400bird]

What did you do with your rig for the last 6 months? Did you disconnect the battery? Or did you leave it idle over the summer?
Did you charge the pack up or do any checks before hitting the road?
Does the bus alternator charge the pack over the 2200 mile trip?

I didn't feel comfortable having the panels on since it dipped below freezing in the morning.

What? Solar panels will do fine in the cold. Plenty of installs get snowed on and frozen in the cold winter.

 

[Bud Martin]

20a seems to be about average compared to last year. I believe the max output of the panels output about 29.9a total at peak output (combined). 3x 315w panels in series. Charge controller is the 40a mppt controller, 4215nb iirc. I actually didn't redo any wiring between last year am now, which is why I'm so confused. Ill check all my connections to be sure, I was pulling my charge figures straight off the BMS app so if there was poor connection it would be between the BMS and the battery itself.

Might be on the right track, it's a 2200 Mile drive to socal, lots of vibrations. I did use red loctite on all my battery connectors though.

You have 3 315W panel in series, no way you can have 29.9A of panel current, your panel current rating may be around 7 ~ 8A.
Your charger is MPPT that take PV panels high Voltage low current into the input of the SCC and converts it down to battery charging Voltage at high current up to 40A max charging current of the SCC can deliver to the battery.
So the 20A you see on the SCC is the battery charging current, not PV current, so on a good day with 40A SCC and 900W of panel you should see about 80% of power to the battery, 700W, poor input power from panels will affect the output as well.
You should be able to see what the PV input Voltage, input current be drawn from the panel, can your SCC display that info?

 

[ppzzus]

What did you do with your rig for the last 6 months? Did you disconnect the battery? Or did you leave it idle over the summer?
Did you charge the pack up or do any checks before hitting the road?
Does the bus alternator charge the pack over the 2200 mile trip?

What? Solar panels will do fine in the cold. Plenty of installs get snowed on and frozen in the cold winter.

I wasn't worried about the panels, but the batteries. I know the BMS has built in protection but I preferred not to risk it. 3 months or so I just had it parked without touching it. The other 3 months I had the panels disconnected but that's it, no other changes. Doesn't get very warm where I live so I just left them idle.

I did zero checks besides checking the voltage when hitting the road, because I'm pretty dumb like half the time.

 

[ppzzus]

Oh yeah forgot to mention they are 280ah cells.

 

[sunshine_eggo]

I live in my bus half the year, other half is in a regular house. I run a 24v system with epever mppt charge controller, 900w in panels, current connected bms. 8x eve 3.2 v cells. I stay in southern California during the winter so sunshine generally isn't a problem.

Last year I was able to run pretty much everything I wanted with no need for power conservation. I was gaming on my PC, running a mini fridge, wifi, etc. Generally it was a set it and forget it type setup. Got to CA last week and now I'm suddenly facing a power crisis.

CA = California?

Didn't you just get a lot of rain? We're a day behind here in AZ weather-wise, and my 3kW of well placed PV only pulled in a total of 2kWh yesterday and 2.5kWh today. I can normally pull in 18kWh with clear skies this time of year.

 

[ppzzus]

CA = California?

Didn't you just get a lot of rain? We're a day behind here in AZ weather-wise, and my 3kW of well placed PV only pulled in a total of 2kWh yesterday and 2.5kWh today. I can normally pull in 18kWh with clear skies this time of year.

Yes, It was a little cloudy about half the days and sunny the rest. I could be overreacting a bit, I've been known to do that. Maybe subconsciously I just wanted to buy new toys.

I'll cut down my power usage over the next few days and see what happens. Unplugged the fridge just now, looks like I'm going to the Mexican spot the next few days.

I'm a bit of a shade tree mechanic when it comes to solar, know just enough to be dangerous.

 

[sunshine_eggo]

Yes, It was a little cloudy about half the days and sunny the rest. I could be overreacting a bit, I've been known to do that. Maybe subconsciously I just wanted to buy new toys.

I'll cut down my power usage over the next few days and see what happens. Unplugged the fridge just now, looks like I'm going to the Mexican spot the next few days.

I'm a bit of a shade tree mechanic when it comes to solar, know just enough to be dangerous.

If you were referencing hard data (I can show you my system performance minute by minute), and you saw an anomaly, I would be concerned. If this is a "seat of the pants" situation, it's likely NOT degradation of your cells but a system that's already near its design limit and a couple of days of sub-optimal solar may push you over the edge and require you to change your behavior.

 

[sunshine_eggo]

Here's why I'm not worried about my system:



Friday, I saw my battery hit full (80%) charge, but it's been mostly downhill for the past two days (Sat/Sun).

My "idle burn" is about 4.4kWh/day at my base loads, so I'm not surprised my SoC is falling due to the inclement weather. I can handle another couple days of this, but after that, the genny will be needed.

 

[ppzzus]

Here's why I'm not worried about my system:

View attachment 123129

Friday, I saw my battery hit full (80%) charge, but it's been mostly downhill for the past two days (Sat/Sun).

My "idle burn" is about 4.4kWh/day at my base loads, so I'm not surprised my SoC is falling due to the inclement weather. I can handle another couple days of this, but after that, the genny will be needed.

Ah, I see what you mean. The daylight hours are only getting shorter and shorter.

One thing I've always wondered is how low is too low? I don't want to push the boundaries but it would be nice to know when I need to shit my pants.

 

[sunshine_eggo]

Lowest cell at 3.00V resting voltage is a good time to shut things down. Should help avoid the pants-shitting.

 

[sunsurfer]

I wasn't worried about the panels, but the batteries. I know the BMS has built in protection but I preferred not to risk it. 3 months or so I just had it parked without touching it. The other 3 months I had the panels disconnected but that's it, no other changes. Doesn't get very warm where I live so I just left them idle.

I did zero checks besides checking the voltage when hitting the road, because I'm pretty dumb like half the time.

There was that couple many years ago that ran one of the first mobile DIY Lifepo4 packs in a bus on a blog and after a few years ruined them while in storage. It turned out an LED bulb drained the batteries way past low voltage risk zone. I don't know about their BMS but I think the LED was on the battery side of the disconnect.

Point is, there are lots of things that can harm the cells, charging while frozen, heat, parasitic drains. Storage can cause issues in unexpected ways.

 

[ppzzus]

There was that couple many years ago that ran one of the first mobile DIY Lifepo4 packs in a bus on a blog and after a few years ruined them while in storage. It turned out an LED bulb drained the batteries way past low voltage risk zone. I don't know about their BMS but I think the LED was on the battery side of the disconnect.

Point is, there are lots of things that can harm the cells, charging while frozen, heat, parasitic drains. Storage can cause issues in unexpected ways.

Do you think the BMS itself would cause a parasitic drain during storage?

 

[sunsurfer]

Do you think the BMS itself would cause a parasitic drain during storage?

I just found the article. Turns out it was an LED on the balance circuit. Not sure if they where part of the BMS or separate. Here is the article. Looks like they went 8.5 years before the incident.

What Killed Our RV Lithium Batteries? 8.5 Years of LiFePo4 | Technomadia

In what seems like another world now, last December we replaced our dead lithium batteries in our vintage bus, Zephyr. We originally installed our GBS lithium cells back in August 2011 - and as far as we can tell, we were amongst the first motorhomes to have a lithium house battery system, and...

www.technomadia.com

 

[sunsurfer]

I just found the article. Turns out it was an LED on the balance circuit. Not sure if they where part of the BMS or separate. Here is the article. Looks like they went 8.5 years before the incident.

https://www.technomadia.com/2020/06/what-killed-our-rv-lithium-batteries-8-5-years-of-lifepo4/

Here is another blog post about 3.5 years in talking about some premature aging. They suspect heat or to much charge but no definitive answer. I would guess heat being in an RV how do you keep them cool in the summer?

Living the Lithium Lifestyle – 3.5 Year Lithium RV Battery Update | Technomadia

One of the most unusual frequently asked questions we get asked out on the road: "How's your lithium batteries working out?" We've even had strangers come up to ask, occasionally without even saying hi first! But I get the curiosity. That we are using lithium batteries for our RV house battery...

www.technomadia.com

 

[Rocketman]

One thing I would recommend is to do an annual capacity test. Do you have a shunt based battery monitor? - like a Victron Smartshunt or BMV712?

Get your battery fully charged and reset to 100%. Then turn off all charging sources and run everything you can. (At the end I use about 700 to 1000 w through the inverter). Run it down until a good set point. I use when my inverter shuts down the first time. My cells still have about 3.01v in them - but that is a good place to stop.

I did this just after installing my battery and something like 527ah - repeated it 1-3/4 years later and got 521ah. (544ah by the spec sheet).

Yes I got this idea of an “annual” test from the above articles from Techmodia.

Good Luck!

 

[740GLE]

Are you cleaning the panels

Rain won’t clean them, try some sort of brush or squeegee and work any dust free.

 

[ppzzus]

Basically turned off all my gadgets for about 4 days, minus my work laptop. They came around after a few days. I had the voltages but I don't think then had the "torque" behind them to go the distance. Back to standard operating procedure.

This thread definitely highlighted some things I need to improve on. First up will be a shunt.