diy solar

diy solar

EG4 6500EX 120/240 Setup, 48V 105kWh Battery & Overkill 100A BMS Install

I've actually ran into something similar a few weeks ago. I was messing with something and my cells were outta balance. As soon as the one cell would clear the HVD setting, charging would ramp right back up again and that cell would peak shutting down the pack again.

I would be cautious about charging to 3.7v. Every cell spec sheet I've seen has always stated 3.65 max for LifePo4.

The move from 3.65 to 3.70 is basically immediate in both directions. The cell hitting the ramp takes only a few seconds to return below 3.65V. But yeah I'm going to test some new things the next day I have like yesterday. It won't be today of this week. Five days of rain and clouds coming.
 
Yeah I'm contemplating options today. Obviously I chose "aggressive" parameters on both. I still want as much maximum absorption as possible, so I'm will to accept there is going to be cycling on/off that occurs when the bank is full. Here in the NH we're in the wet season and there will be a lot of cloudy days over the next 4-6 weeks.

Lowering the 6500s charging voltage is likely the way to find a sweet spot that keeps the banks open and instead throttles charging.
I'm actually trying to get information from SS on how to configure the Absorption on the 6500. Manual shows it should be configurable between 10 min to 8 hours. So either the manual will be updated and that info will be removed, or we should hopefully get a way to configure the absorption time...
 
The move from 3.65 to 3.70 is basically immediate in both directions. The cell hitting the ramp takes only a few seconds to return below 3.65V. But yeah I'm going to test some new things the next day I have like yesterday. It won't be today of this week. Five days of rain and clouds coming.
With where the voltage is in the charge curve, I can imagine as soon as power is applied or removed, it would trigger either the set or the release.

Good luck. I'm hoping the clouds stay away here. Supposed to have 50's this week where I am in MI. Supposed to...
 
I just adjusted:

setting 26 down to 57.4V
Setting 27 down to 55.4V
Setting 31 down to 55.4V

I'll see what happens if I hit full this afternoon
 
It applies if you have batteries set to USE, which is how I am running.
So you enabled option 30, which is disabled by default?

Maybe you can help me understand the purpose of equalization, cause I'm honestly not exactly sure what it's supposed to do. I've always just heard it's for FLA batteries.
 
Took me a while to find it, but this Victron MPPT SCC manual is where I saw not to enable equalization for lithium cells. Saw this back when I was setting up my 12v system 2 years ago.

 
Yes.

So my logic when installing was I have (8) banks with their own BMSs. No matter how exact I wire, some banks will charge faster and some will be the first to begin discharge. This means the packs will over time create a hierarchy of "who's first" or basically who the strongest and weakest links are.

Given this I thought it would be good to have an extended period of balancing the whole array periodically.

I am honestly not sure if this will work or have a positive effect. It's just what I was thinking when I installed.

I did not stay at a Holiday Inn Express last night.
 
Took me a while to find it, but this Victron MPPT SCC manual is where I saw not to enable equalization for lithium cells. Saw this back when I was setting up my 12v system 2 years ago.


I get you would not use this function with one battery. But is seems to me balancing multiple packs is essentially "top balancing" but at a higher level and would help limit one pack taking the brunt of work from the array, especially at the head and tail of the curve where voltage steepens.
 
Yes.

So my logic when installing was I have (8) banks with their own BMSs. No matter how exact I wire, some banks will charge faster and some will be the first to begin discharge. This means the packs will over time create a hierarchy of "who's first" or basically who the strongest and weakest links are.

Given this I thought it would be good to have an extended period of balancing the whole array periodically.

I am honestly not sure if this will work or have a positive effect. It's just what I was thinking when I installed.

I did not stay at a Holiday Inn Express last night.
Thanks for sharing your thought process. Like I said, I wasn't really sure what the purpose of that function is. Obviously I saw "don't use it" on the internet, so it has to be true, right??? :ROFLMAO:

I look forward to hearing how things end up going for you. Still making me jealous w/ the 8 battery banks...

I must be a little slow this morning (only had 1 cup of coffee), cause I didn't get the Holiday Inn Express reference.
 
A side note we are hitting 50+kWh on full sun days now and I haven't properly spaced the panels yet due to snow and ground frozen still. I learned a lot this winter. Spring/Summer/Fall should be a walk in the park for keeping the house running. I may even move the electric dryer and stove over to the solar.

Winter is really where the rubber hits the road in managing your system. If you can scale to provide full winter coverage in the NE US Nov-Feb, you can basically coast the rest of the year.
 
A side note we are hitting 50+kWh on full sun days now and I haven't properly spaced the panels yet due to snow and ground frozen still. I learned a lot this winter. Spring/Summer/Fall should be a walk in the park for keeping the house running. I may even move the electric dryer and stove over to the solar.

Winter is really where the rubber hits the road in managing your system. If you can scale to provide full winter coverage in the NE US Nov-Feb, you can basically coast the rest of the year.
Yeah, I started hitting just about 30kWh. I think I'm gonna have to figure out a way to move the electric stove, water heater and dryer over this summer, but I'll have to be able to move them back during the winter (at least till I get more panels and battery capacity).

Where I am, I noticed that as soon as Feb1 hit, the shading I was experiencing from the neighbors trees started disappearing. So production really started ramping up. Unfortunately I didn't have my full arrays set up last fall, so I really don't have a "winter start date" from my production standpoint. We also had a lot more snow in Feb than we did in the previous months, so the reflective light off the snow helped as well.
 
Took me a while to find it, but this Victron MPPT SCC manual is where I saw not to enable equalization for lithium cells. Saw this back when I was setting up my 12v system 2 years ago.

Equalization is where lead acid is held at a higher voltage than normal charging. The purpose is to remove sulfation on the plates and bring low cells equal to high cells.

I would not use EQ on LFP.

I have my 6500EX's set for 56.5V bulk, it never does go into float. As the bank voltage gets close to 56.5V, the 6500EX's start to throttle the SCC's similar to absorb. Actual bank voltage is 56.4V according to my Batrium and it's Shuntmon.
 
We're going to move one more time in a few years. The property we choose will be highly driven by Southern sky access.
Equalization is where lead acid is held at a higher voltage than normal charging. The purpose is to remove sulfation on the plates and bring low cells equal to high cells.

I would not use EQ on LFP.

I have my 6500EX's set for 56.5V bulk, it never does go into float. As the bank voltage gets close to 56.5V, the 6500EX's start to throttle the SCC's similar to absorb. Actual bank voltage is 56.4V according to my Batrium and it's Shuntmon.

Sure. But in my case the EQ is not set to a high number. It's basically just a repeat of my float setting. I'm not sure it makes any real difference either way in summer as my pack will be top charged at the end of most days.
 
Psaki'ing back to my last changes, they worked.

So with 57.4V bulk and 55.4V Float the batteries do not constantly force the inverter to toggle charging on off. I did also alter the BMS setting from 3.700V down to 3.670V for single cell over volt. It made basically no difference in the frequency of charge holding. The voltage goes up so fast and drops so fast the second disconnect happens there isn't a real change in timing. I left them at 3.670 to help with equalizing the other cells faster.

Watching a cell go from 3.600V to 3.700V nearly instantly is a good lesson on why everyone preaches about never running LiFePO4 without a BMS. Holy F, you could miss it by blinking.
 
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