Lithium!

[JeremyG]

I've been struggling for about a year, using flooded batteries.
Basic 100ah flooded battery.
Basic mttp solar controller.
1850watts in panels.
It works great in the day...but the numbers drop fast when the sun goes away.

Everything I've tried hasn't worked.
All the advice I got from you wonderful people has given me great insight (so thank you).

I discovered a YouTube channel called "the quiet nerd". He always uses these enormous LifePo4 batteries and does things with them which I could never imagine doing, using my flooded batteries.
(Making boats, go karts, portable ps5), all powered with LifePo4 batteries.

So...I thought I'd try lithium.
I bought a 100ah LifePo4 + victron mttp 100 | 50.

I gave it the first full 24 hours to charge, before even considering using it.

The voltage stayed strong at 13.5.

Day 2, we tried the fridge (thankfully, it's been sunny all week). The fridge held well and the numbers never dipped below 13.The flooded batteries always bounced around between 12-14v.

Tried a load of laundry...still, voltage stayed at 13.5.

I've unplugged all flooded batteries and I've only got 1, LifePo4, 100ah plugged in...but WOW, the difference!!

Last night, in my basement, I plugged my humble 40" tv + surround sound+ PS4 into it, with a really long extension cord... expecting the voltage to drop really slowly...but it didn't.
It stayed in the 13's.

I'm trying to take it slow...but so far, everything I've thrown at it, it hasn't gone below 13v.

My flooded batteries would often be around 12.5 in the morning.

This lithium has stayed in he 13's the whole time.

The screen shot is from like 8pm to 9pm last night, gaming. The sun was already over the horizon.

It started at 13.5 and 1 hour later, it was 13.13.

My flooded batteries wouldn't have given me 30 minutes.

I'm selling all the flooded batteries and getting more lithium!

 

[DIYrich]

100 ah lead acid battery has 50 ah usable. By replacing with 100 ah lifepo4, you doubled your battery size. That is the main difference.

 

[kommando]

Had some old Gel's I put into service when I got an SMA Sunny Island, had much the same issues as you. Recently went to LFP and the difference is night and day, will not be going back.

 

[Bluedog225]

Same experience here. Sometimes it feels like cheating. My 200 amp hour is SOK never goes below 80%.

 

[robbob2112]

Did you change the charge setting on the mppt to LiFePO or equivalent?

 

[seneysolar]

100 ah lead acid battery has 50 ah usable. By replacing with 100 ah lifepo4, you doubled your battery size. That is the main difference.

I think its worth mentioning that with a 100AH lead acid, you can use the full capacity, its there if you need it, BUT you should expect shortened lifespan. Its not that you have a 50ah battery and it dies instantly at 50% of 100AH.

Im a fan of lead acids but i have yet to see a 12v that actually lasts for deep cycle use. They are fragile at best, the plates are too small and too close together. In my opinion the only true deep cycle lead acids are 6V and 2V.

2 - 6v 200ah golf cart batts in series will kick butt compared to 2 -12v 100ah in parallel assuming all else equal.

If the OP's flooded batteries died in 30 min, they were likely not being fully charged properly or had a bad one in the mix. With 1850w of panels, i wonder what the "basic mppt" was? 100+ amps?

 

[robbob2112]

I think its worth mentioning that with a 100AH lead acid, you can use the full capacity, its there if you need it, BUT you should expect shortened lifespan. Its not that you have a 50ah battery and it dies instantly at 50% of 100AH.

Im a fan of lead acids but i have yet to see a 12v that actually lasts for deep cycle use. They are fragile at best, the plates are too small and too close together. In my opinion the only true deep cycle lead acids are 6V and 2V.

2 - 6v 200ah golf cart batts in series will kick butt compared to 2 -12v 100ah in parallel assuming all else equal.

If the OP's flooded batteries died in 30 min, they were likely not being fully charged properly or had a bad one in the mix. With 1850w of panels, i wonder what the "basic mppt" was? 100+ amps?

I was a FLA OR SLA fan before I needed to replace the last set at 3 years and the cost had gone up a lot.

LFP batteries (LiFePO4) are far more forgiving for minor abuse, and require nothing more than checking the bolts and fuses to ensure they are not getting hot or loose.

You need to have the right charge setting so when they are done you don't equalize them, just bulk and absorption. If your MPPT doesnt have a LFP setting just set it to manual. Read the manual from your battery for the settings.

Being able to use 80% of charge without any damage is a wonderful thing. And at least a 10 year lifespan with nothing special is a plus.

 

[JeremyG]

Did you change the charge setting on the mppt to LiFePO or equivalent?

(Yes...that's one of the first things I did, when I installed the app and started navigating the menu)

I've got my eyes set on a 240ah LifePo4 that's $1,000. The "quiet nerd" YouTube guy uses that large battery for everything.


seneysolar

"If the OP's flooded batteries died in 30 min, they were likely not being fully charged properly or had a bad one in the mix. With 1850w of panels, i wonder what the "basic mppt" was? 100+ amps?"

This is where things get confusing for me.
During the day, especially in great weather...the 4x 12v batteries I have in parallel, get to 14.5 pretty quickly.
The EZSUN mttp screen says 100%.
But, as the sun goes down, the 14.5 (or whatever number it's at), drops down, very slowly to about 12 or even 11.
I bought a multimeter and it says the same thing.
I've tried plugging in the batteries individually, tried charging them with the grid via a truecharge 20+ charger...but the number would always go down nice and slow.
(Even with nothing plugged into them).

They're new batteries...only a year old.

I can barely charge my cellphone+ plug in the baby monitor at night.

So...I thought I'd try LifePo4...and thankfully, it vastly exceeded my expectations.

 

[Ykdave]

Nice! I recently set up my first solar setup and with past experience of FLA batteries just sucking in general I went straight to a pair of 280ah lifepo4 and couldn’t be happier with them. I originally planned on a much larger battery bank, but after seeing how these performed last weekend I don’t really see the need to, or at most add one more pair for 560ah 24v

I’ve used a pair of gr31 FLA in my service truck to power an inverter for running chargers and some tools and they just didn’t seem to hold their ground very well.

 

[seneysolar]

(Yes...that's one of the first things I did, when I installed the app and started navigating the menu)

I've got my eyes set on a 240ah LifePo4 that's $1,000. The "quiet nerd" YouTube guy uses that large battery for everything.


seneysolar

"If the OP's flooded batteries died in 30 min, they were likely not being fully charged properly or had a bad one in the mix. With 1850w of panels, i wonder what the "basic mppt" was? 100+ amps?"

This is where things get confusing for me.
During the day, especially in great weather...the 4x 12v batteries I have in parallel, get to 14.5 pretty quickly.
The EZSUN mttp screen says 100%.
But, as the sun goes down, the 14.5 (or whatever number it's at), drops down, very slowly to about 12 or even 11.
I bought a multimeter and it says the same thing.
I've tried plugging in the batteries individually, tried charging them with the grid via a truecharge 20+ charger...but the number would always go down nice and slow.
(Even with nothing plugged into them).

They're new batteries...only a year old.

I can barely charge my cellphone+ plug in the baby monitor at night.

So...I thought I'd try LifePo4...and thankfully, it vastly exceeded my expectations.

Well, 12.6 would be about resting voltage of a fully charged FLA. With a load on them id expect 12.1 or .2. BUT voltage is not an accurate measurement for state of charge unless the circuit is open and resting. If they were just crashing to charge your phone something was wrong.

Dont get me wrong, I agree that LFP performance is fantastic. Whatever battery chemistry you use, proper charge profiles will be key. Your victron 100/50 will do most of it for you. Enjoy!

 

[JeremyG]

New to victron.
I got myself a 100|50

I've got a PWM (which isn't plugged into anything).
I've got a simple EZsun mttp (which has been promoted to the shed solar set up).

My question is, I had set the "shut off" to 10.8 (if the voltage had gone to 10.8, the inverter would beep and I'd shut it down to charge more).

Admittedly, the lead acid was really difficult to figure out/maintain.

I've been using a 100ah LifePo4 for this past week and it's been way, way better.

When setting up the numbers, my research says to set up the resting voltage to 13.5 (would it damage the battery if i select a higher voltage...like 14?

The Lowest safe voltage was 3.2?
I'm SO used to the inverter beeping at 10.8.

Do I have to reset my brain too, and be ok with the voltage going down slowly to the 8's, 7's, 6's, 5's (like during a cloudy day?)

Can I/do I need to set the inverter to give that warning beep, if the voltage goes down to 3.2?
(I'm not sure where on the victron menu to do that .. because I'm still learning the terminology).

Thank you for your help.

 

[seneysolar]

What brand/make/model battery did you get? They should give you specs for charging and the high/ low limits of the BMS.

The victron mppt has a pre set for LFP batteries that is generally decent/safe to use. You can tweak settings if you want but it will require some closer monitoring to avoid nuisance bms trips. Something like a victron smartshunt.

You will likely never get to an inverter low voltage cut off. The battery bms will cut off first.

 

[JeremyG]

seneysolar

Power Queen 12V 100Ah LiFePO4 Battery, Group 31, 1280Wh Deep Cycle Lithium Battery 12V with 100A BMS, 4000-15000 Rechargeable Cycles, Support in Series/Parallel, For Camper, RV, Trolling Motor, Marine

Question #2
I found the setting in the victron for setting my "low voltage".
Google said lithium can go as low as 3v.

But, this "low voltage" setting only goes down to 10.

I confirmed this, today, when I plugged in a couple too many things into it and it beeps at 10v.

I don't plan to over do it.
I plan to get more of these lithium batteries.

How do I set it, so I can do more with the 3v min and 13/14 max voltage?

Thank you.

 

[seneysolar]

seneysolar

Power Queen 12V 100Ah LiFePO4 Battery, Group 31, 1280Wh Deep Cycle Lithium Battery 12V with 100A BMS, 4000-15000 Rechargeable Cycles, Support in Series/Parallel, For Camper, RV, Trolling Motor, Marine

Question #2
I found the setting in the victron for setting my "low voltage".
Google said lithium can go as low as 3v.

But, this "low voltage" setting only goes down to 10.

I confirmed this, today, when I plugged in a couple too many things into it and it beeps at 10v.

I don't plan to over do it.
I plan to get more of these lithium batteries.

How do I set it, so I can do more with the 3v min and 13/14 max voltage?

Thank you.

No, you cant discharge your 12v battery down to 3v. When they refer to 3v, that is per cell. Basically your usability is between 3.0 and 3.65v per cell. (12V to 14.6)

I dont have the specs for the power queen but others may chime in. Look for low voltage protection and over voltage protection in the specs.

You are confusing the purpose of the load control on the charge controller. The inverter should not be connected there. Inverter should be directly to the battery (fused of course)

 

[JeremyG]

seneysolar
3v per cell makes much more sense.

Lithium aren't like flooded.
Do they get damaged if they drop to that 10v, like lithium does?
(I don't plan on letting it get that low)

And Correct on the set up...

3x 230 watt panels on my front porch.
2x 230 watt panels on my roof.
3x 230 watt panels on my back porch roof.
The way the sun moves, there's pretty much always 5 panels getting sun.

All the panels are wired in parallel.
They all join together to a bus bar in the basement.

The panels are plugged into the PV + - and the batteries are plugged into the battery + -.
Yes, they have a fuse.
The 2000watt pure sine inverter is plugged into the battery.

 

[seneysolar]

seneysolar
3v per cell makes much more sense.

Lithium aren't like flooded.
Do they get damaged if they drop to that 10v, like lithium does?
(I don't plan on letting it get that low)

You likely wont be able to get that low, the bms will simply shut off the battery. This is the low voltage protection part of the bms. I couldn't find the spec for the powerqueen so im not sure when exactly that will occur.

 

[Ykdave]

You could always do trial and error, to find out where the bms will cut out. Ideally you don’t want to be hitting the bms cutoff voltage during normal use

Depending on how your setup is wired and what kind of voltage drop you are getting under typical load, you’ll have to check it to determine what your inverter cutoff voltage should be (ie 11.9v at the inverter = 12.1v at the battery)

 

[JeremyG]

Things have changed so much after getting the lithium+ the victron mttp solar controller.

It's almost always 13 or 14.

In fact, the 2000 pure sine inverter has started beeping at us, even though it's in the 13's & 14's.

Google is suggesting there's too much power available and it wants out.
That's never happened before.

Can I trust Google on that?

 

[seneysolar]

Things have changed so much after getting the lithium+ the victron mttp solar controller.

It's almost always 13 or 14.

In fact, the 2000 pure sine inverter has started beeping at us, even though it's in the 13's & 14's.

Google is suggesting there's too much power available and it wants out.
That's never happened before.

Can I trust Google on that?

What are the loads on the inverter? Are you maxing out the 2k watts?

 

[JeremyG]

seneysolar

Am I maxing out the 1850watts?
I highly doubt it.

We are starting off very gentle.
We've got the kitchen fridge plugged in during the day (back on grid at night).

I plugged one of those USB sockets in one of my kids rooms for the baby monitor...so the baby monitor is being powered by the battery at night.
We also have 2 of these USB sockets in the bedroom, thus charging our phones with the battery at night, too.

Tonight, I plugged my gateway/modem into the battery (vs grid), and plan to keep it there contingent on battery levels.

I've plugged in the living room TV+laptop+surround sound into this lithium battery, during the day + a couple hours after the sun goes down.

I plugged my basement chest freezer + bar fridge into the battery.
(Not all of this at one time).

It's been testing 1 thing one day and another the next.

The inverter wired remote plate thing shows 13.5 very consistently.
It hasn't gone into the 12's hardly at all this past week.

Very different experience, compared to the lead acid.