Adding storage to my Enphase system

[Frank in Thailand]

One way to have Wifi to monitor the cells is the DIYBMS

GitHub - stuartpittaway/diyBMSv4: Version 4 of the diyBMS

Version 4 of the diyBMS. Contribute to stuartpittaway/diyBMSv4 development by creating an account on GitHub.

github.com

DIYBMS v4

Discussion of DIYBMS version 4 Source code and files (GITHUB open once project is launched)

community.openenergymonitor.org

I have them.
easy to build / program and relative cheap.
($3 per cell module, $10 for controller (include Wemos D1), optional 4 channel relay $2)

Funny to see the active balancer BMS!
I got one of the first.... It worked for 3 days.
Seller got many (all) defective returned.
As the are still for sale, new batch must be better.

One negative thing is that the BT antenna is covered by the metal casing.
if you open it, your range increase a lot.
the case is normally not needed for cooling (as you can feel, it does not get hot)
seller gave me this tip to improve BT range.

 

[svetz]

Didn't see the CV absorb you mentioned in the graph, but good that you're getting into that stage of charging.
Pity about those pictures! ;-) Glad you all are still doing okay out there!

...Do we have of way of tracking PGE’s curtailing commands? Just logging grid frequencies?

A number of locations (e.g., California, Hawaii, Peruto Rico, Canada, New Zealand) have passed laws (e.g., CA Rule 21) that enable grid operators to curtail renewable energy from residential homes. I like the idea of monitoring frequency. In regards to the conspiracy theories.... it wouldn't surprise me if grid operators did misuse it at some point (just as some people screw up bridge traffic for political reasons). But I have faith that someone monitoring it will sue them. It might only be a couple of bucks per home, but as it would be easy to prove the lawyers would be motivated as they'd make millions.

 

[Ampster]

A number of locations (e.g., California, Hawaii, Peruto Rico, Canada, New Zealand) have passed laws (e.g., CA Rule 21) that enable grid operators to curtail renewable energy from residential homes.

Interesting take on those regulations. Prior to those regulations frequency changes would just force GT inverters to go off line all at the same time. The new regulations made the grid more resilient because new inverters will modulate instead of just turn of all at the same time resulting in a shock to the system. They also make AC coupling more efficient because inverters designed to that standard will modulate instead of just turn off and have to wait 5 minutes to reboot when frequency comes into spec again.
Jack Rickard advanced this as a conspiracy theory that the utilities would do this to protect their revenue stream. I think he was trying to instill fear so he could sell more hybrid inverters.

 

[GXMnow]

I just checked in on my system and the panel cleaning does seem to have helped. It is basically tracking last year, when the panels were only two months old. Already over 1 KW of output by 8:45 am, it has not been that good since before the Lake Fire started. I went out and looked at the panels from the front yard in the sun, they certainly look a lot better, but I did not get them as clean as I thought in the in the dark. There is still a little haze across the glass. I didn't use any cleaning solution, squeegee, or rags. I just let the water flow from the top down.

With the settings I left last night, the XW did start charging as scheduled. I think I will set the start time a little later. At 9 am, with the higher current, 26.3 amps, it has already put 3.4 KwH back into the batteries in 2.5 hours of charging. At this charge rate, it will try to put about 12 KwH's into the battery bank. It will most likely top out at just over 10 KwH's. If it does go into Absorb, it will have about 2 hours before it starts exporting again. Too bad it most likely is not going to export without manually adjusting some settings again.

Hopefully I will be able to move the solar and some loads over to the essential loads panel tonight after it is done exporting at 9 PM. At that point, it is just sleeping anyways. Too bad I have to leave it in run mode overnight for it to pass through to the load panel. It takes about 30-40 watts to keep the box alive. Not a bad loss when charging or inverting, but when it is idle, that is one heck of a phone charger being left plugged in. But that is the cost of having it on standby to be able to take over in a power failure. It is less than my old PC I leave in standby, but much more than my new PC in sleep.

Speaking of Jack Rickard. I just watched "most" of his latest video. He is now saying how terrible 48 volt systems are, and he is switching to 396 volt (96S at 4.125 per cell) and using a complete Tesla Model 3 battery on a 30 KVA inverter. His old system was 12 KVA at 48 volts = 250 amps. The new one at 30 KVA at 396 volts is just 76 amps. Less than 1/3 the current for over double the power. And 96S seems to be the EV standard. Tesla, Chevy, BMW all use 96S as their complete battery bank. I guess 400 volts is the max anyone wants to go. My C-Max is a little lower, only 76S in the Hybrid version. Too bad the inverters to handle that voltage are crazy expensive.

 

[ArthurEld]

Kind of weird but kind of cool that EV batteries and home batteries have so much in common.

 

[GXMnow]

Of course, I am trying to see how much my panel cleaning did, and a big cloud bank moves in. I can only hope I get some clear sky near noon for a decent comparison.

I am certainly doing my part to flatten my duck curve. With the clouds over right now, I am at near zero power at the grid meter as the power coming from the panels is matching the power used by the house and going into my battery. Only pulling 2 kw when the A/C cycles on.

 

[Ampster]

I am certainly doing my part to flatten my duck curve

We may have different utilities but we share the same statewide duck curve.

 

[GXMnow]

I was basically saying my effect on the duck curve. SCE just posted my useage from yesterday.

Yes, instead of exporting from 6 am to 3 pm, I am using a little more power, helping pull some of the duck from my neighbors grid tie systems, and then using much less power during the peak on the ducks head. My peak at 7pm, was still only 2.4 KW. And I exported again in the 8 to 9 hour. I turned my duck upside down, so I am helping the grid overall. For just setting a fixed current charge and a fixed power export, this is looking very good. With a WattNode and proper programming, it could really flatten it out. Looks like I will use less A/C today, but these clouds are messing with the solar production, so it is a win/lose situation.


Sun just poked through the clouds for a full 15 minutes, and my production with the clean panels is better than last year, and well above yesterday. It made the next 15 minute step as I was typing, and it is even more above last year. Just hit 3.4 KW, last year, same time, was 3.2 KW. Yesterday, without clouds, it was just 2.9 KW at this time. The ash on the panels was soaking up nearly 15% of production. Wow, The last 3 times I cleaned then I never saw that big of a change.

 

[GVSolar]

I have always thought that bulk terminates at the same voltage point that Absorb voltage is set at. Maybe that is some trick way to have a longer Absorb time but who knows. I have always thought of Bulk at constant current mode and Absorb and constant voltage. Mine does have a rebulk voltage and that is useful if you have fully charged during the day from solar but have a big load after charging is done. That way you can get another full current bulk charge to fill it up later in the day.

Don't know if this is helpful or not, but in "Schneider-speak" bulk termination can be somewhat confusing. I was having trouble getting the charge profile that I wanted until I set the bulk termination voltage higher than my bulk setting - that allowed the profile to get closer to my target voltage. I have an off-grid SW4024, but I am both AC & DC coupled, so this might be useful info for you.
From the Schneider SW4024 manual:
"Absorption charge is the second stage of battery charging and provides the batteries with a controlled, constant voltage. During this stage, the current drawn by the batteries slowly decreases. When this current falls below 2% of the battery capacity, or when the configurable Absorb Time expires, the charger switches to the Float or NoFloat stage, depending on the selected charge cycle. The timer begins when the battery voltage is above the bulk termination voltage for three minutes."
Best.

 

[Ampster]

Don't know if this is helpful or not, but in "Schneider-speak" bulk termination can be somewhat confusing. I was having trouble getting the charge profile that I wanted until I set the bulk termination voltage higher than my bulk setting - that allowed the profile to get closer to my target voltage.

Interesting. I have only one voltage setting which is the point where constant current converts to constant voltage. Skybox uses the same terms as Schneider, Bulk and Absorb. I also have a Rebulk voltage which I explained earlier. Could that be what that other Bulk setting is on your Schneider? What you are telling me is the Bulk termination is the end of the Constant Current stage. Maybe the other Bulk setting has to be lower and it starts constant current when voltage sags to that point. You don't want them too close together or you will have too much cycling.
I have set my Float slightly below the constant voltage point but it starts pretty soon after constant voltage has ramped down. I generally have a load and the voltage of the pack sags enough to trigger Float. I don't have any control over Float volatage but from my BMS I am guessing it is around 5 Amps.

 

[400bird]

Talk about duck curve! I'm definitely not helping

 

[GXMnow]

Don't know if this is helpful or not, but in "Schneider-speak" bulk termination can be somewhat confusing. I was having trouble getting the charge profile that I wanted until I set the bulk termination voltage higher than my bulk setting - that allowed the profile to get closer to my target voltage. I have an off-grid SW4024, but I am both AC & DC coupled, so this might be useful info for you.
From the Schneider SW4024 manual:
"Absorption charge is the second stage of battery charging and provides the batteries with a controlled, constant voltage. During this stage, the current drawn by the batteries slowly decreases. When this current falls below 2% of the battery capacity, or when the configurable Absorb Time expires, the charger switches to the Float or NoFloat stage, depending on the selected charge cycle. The timer begins when the battery voltage is above the bulk termination voltage for three minutes."
Best.

This is my problem. The "Bulk termination Voltage" will not go above 57.6 volts. But then the "Bulk/Boost Voltage Set Point", "Absorption Voltage Set Point", "Float Voltage Set Point" entries will all go to 64 volts. I have all 3 at 58 volts now, but it terminated the charge at 57.6 volts, and did not do any real Abosorption as the current fell to 0 in under 15 minutes, and the voltage fell a tenth, so it was not doing any real CV cycle. At least it did not throw the DC overvolt error again.
Here is my current charger settings.

And here is the graph of today's charge cycle.

You can clearly see it rapidly dropped the charge current, then did put out half current fora little as it sloped down, and did another drop and shut off completely by 1PM. It did put 9.1 KwH's into the battery, which is pretty close to what it exported last night, so I am okay with it only getting the battery this full for now. This is actually being very nice to the battery and it will extend it's life, but in a power failure, I would like to pump it up some more. I am leaving close to 20% more energy up there.
Here is a chart from Battery University.

So I am currently stopping charge at about 4.1 volts per cell with no saturation. About 80% full. At that point, I should get well over 3,000 cycles.

 

[GXMnow]

Talk about duck curve! I'm definitely not helpingView attachment 20762

Just scaling off of your plot, it looks like you exported 8.6 KwH's, The is a lot for this time of year here, but cause of the heat I have to use more A/C, but a few weeks ago, I was pushing that much. Your evening usage does not look bad at all. You only peaked at 1.9 KW. My evening peak without the battery was topping 5 KW during this crazy heat wave. With the battery (and the slightly cooler weather) I am holding the peak draw to about 2 KW even with my A/C running hard.

Just noticed my Enphase report for today shows 74F for the outside temp. My outdoor thermometer in the shade on my north side porch is showing 95 right now.

 

[Ampster]

This is my problem. The "Bulk termination Voltage" will not go above 57.6 volts.

Maybe that is a way to force it to be in Constant Voltage mode for a longer period of time. That might be a feature rather than a bug. I notice you have Absorb current set to 72 Amps, the same as Bulk. What if you lowered that would that make CV stage longer.
Also I notice you have charging set to two stage. Would the third phase be Float?

 

[400bird]

Maybe that is a way to force it to be in Constant Voltage mode for a longer period of time. That might be a feature rather than a bug. I notice you have Absorb current set to 72 Amps, the same as Bulk. What if you lowered that would that make CV stage longer.
Also I notice you have charging set to two stage. Would the third phase be Float?

Or increased bulk termination time?

Just scaling off of your plot, it looks like you exported 8.6 KwH's, The is a lot for this time of year here, but cause of the heat I have to use more A/C, but a few weeks ago, I was pushing that much. Your evening usage does not look bad at all. You only peaked at 1.9 KW. My evening peak without the battery was topping 5 KW during this crazy heat wave. With the battery (and the slightly cooler weather) I am holding the peak draw to about 2 KW even with my A/C running hard.

Just noticed my Enphase report for today shows 74F for the outside temp. My outdoor thermometer in the shade on my north side porch is showing 95 right now.

Ah right, well with the threat of rolling black outs the AC was turned up to an uncomfortable 82 if memory serves. Luckily I wasn't home. The wife wants to do her part. Even then, I am surprised the usage was so low. The high that day was 109!

 

[Ampster]

Or increased bulk termination time?

What is bulk termination time?
I have heard to explanations for increased Absorb time. In Pb batteries it is inefficient but if I understood it correctly it balanced the 2 v cells within a 12 volt battery. In Lithium, extended Absorb (constant voltage) allow the BMS balancing shunts to operate longer.

 

[GXMnow]

All of the current settings defaulted to 140 amps, the maximum of the charger. I dropped them to 72 amps, which is just 0.2 C rate on my 360 AH pack. I am being very gentle on these things. Changing those 3 current settings did not change the current, as it seems to just be going by the "Maximum Charge Rate" percentage of 19% 140 x 0.19 = 26.6 amps My charge graph shows 26.19 amps. Here is a zoom in of the end of charge.

The current was still over 26 amps right to the 12:49 pm time stamp. Then at 12:50 it was just 10.68, rebounded to 12 amps, tapering to 11, dropped to 7.7, rebounded to 8.4, and then by 1 pm it was down to zero. So 10 minutes of CV charge. It really seems to be ignoring most of the charger settings.

 

[GVSolar]

FWIW. Again, I don't have an Schneider XW, I have an SW - but it was necessary for me to decrease the "Battery Bank Capacity" setting well below the actual capacity to a calculated percentage - in order to get my absorption exit amperage where i wanted it (2 amps). On the SW the absorption charge ends at a fixed percentage of that Battery Bank Capacity number. Also, to get the the charging profile I wanted I had to use 3 stage charging - in the Custom battery menu - and not on the Lithium setting. Much more flexibility in Custom. The Bulk Termination setting was only adjustable then - and then only in the Advanced Settings menu. Best.

 

[GVSolar]

By the way I am using Lifepo4 batteries - the 24v BYDs - in my configuration. I simply set my "float" to a 26.7, and my recharge to 26.4. I vary my top end charge but keep it well below 100% - I don't want to push the old girls too hard.

 

[GVSolar]

The SW uses 2% as the exit threshold for absorption. That battery capacity figure doesn't really affect anything else that I'm aware of.
SW Manual: "Absorption charge is the second stage of battery charging and provides the batteries with a controlled, constant voltage. During this stage, the current drawn by the batteries slowly decreases. When this current falls below 2% of the battery capacity, or when the configurable Absorb Time expires, the charger switches to the Float or NoFloat stage, depending on the selected charge cycle. The timer begins when the battery voltage is above the bulk termination voltage for three minutes."