24 kW Sunny Island system with 190 kWh of CATL battery storage and 12kW SI system with 44kWh as back up.

[Calvin98]

24 kW Sunny Island system with 190 kWh of CATL battery storage and 12kW SI system with 44kWh as back up.

I have been looking to switch to lithium for many years now. I have been using a large 48V forklift battery as the power source for the split phase 12 kW Sunny Island system for several years up until now to use as back up in case of grid outage. It’s been working fine for years. Since I already had the electric forklift, it seemed like a good idea to use it’s 48V battery for home back up also. Didn’t need to buy a new battery that way. Been waiting for the prices to come down on lithium and to find a BMS that’s compatible with our Sunny Island system. I’m in Northern California and the utility sent me a notice in the summer saying that my net metering was coming to an end after 21 or 22 some odd years and that we were transitioning to their new Solar Billing program. So I had to make the switch as soon as possible. The new Solar Billing program basically means you get nothing for whatever you feed into the grid and you have to pay full retail rates for whatever you take out. Which of course means there’s no point in feeding anything to the grid at all anymore.

The Batteries
The batteries were 12V 228 Ah 4s CATL LiFePO4 modules that Hedges and I got from Big Battery down in LA. They had a listing for them on eBay in the summer at a real good deal and Hedges let me know about it. We did some checking and found that the JKPB series BMS was working with the Sunny Island‘s in closed loop communication. Since both Hedges and I have Sunny Island systems, we needed a BMS that’s compatible. And thanks to Kommando who had the JK PB series BMS installed and working in closed loop communication in his Sunny Island system, we took the plunge. In the end, I ended up driving down to LA like three times and I picked up at least five pallets of batteries as I remember. We probably ended up getting close to 500 kWh of storage. The 64 individual 12 V batteries we have installed now are roughly equivalent to 14 Tesla Power Wall 3’s, but at a fraction of the cost.

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Pictures of the batteries.


These do seem to be really nice batteries. They are housed in a sturdy powder coated metal case and covered from five sides with heavy duty steel. The case is riveted together with some heavy duty rivets, so the compression seems to be taken care of. The bus bars are also welded on which is nice. Each battery also has a heating pad built-in. You can also see that on the top of the battery there’s a connector where you can connect all the BMS leads to. That connector also includes a temperature sensor built into the battery. We didn’t end up using it yet, but it’s possible to use in the future if we wanted. They have some nice terminal caps where the sides can be broken away and still have the cover be usable when it’s connected to a bus bar or lug.There’s also a nice thin plastic cover the covers the bus bars that can keep dust and dirt out. Did some searching and I was able to find the original manual for the battery also. That’s a really good manual too. It lists all the specifications in detail. Plus it lists the specs and part numbers for the Molex terminal for the BMS connector and the connectors for the heating pads. We searched online and found a place that we were able to buy the BMS connector from a company in China. They were also available at Digikey, but terminals were out of stock there initially.

Manual link

The heating pad connector male and female

https://www.digikey.com/en/products/detail/molex/0039013028/2405392

https://www.digikey.com/en/products/detail/molex/0039013029/1784883



Pins male and female

https://www.digikey.com/en/products/detail/molex/0457503111/2404789

https://www.digikey.com/en/products/detail/molex/0039000081/1643442



Crimper

https://www.amazon.com/gp/product/B0BZD5XQZX?ie=UTF8&th=1



BMS Molex connectors and pins we got at Digi Key.

The trick with the BMS connector was that you needed a very special and very expensive tool for the crimping. I think Hedges said it was several thousand dollars for the tool. He found a hand-held one for a similar terminal size on eBay at a good deal and modified it so that he could use it for the pins for the BMS leads.


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[Calvin98]

The JK PB Series BMS
I did a bunch of searching online to see where to buy these things. Long story short is that JK seems to have a trading company and their own company which both sell the BMS on Alibaba and Aliexpress. Then of course there are all the third-party sellers that also sell the same BMS who also all say they are “JK”. We ended up going with the factory on Alibaba.

Tip: you can order the display with an extra long cable. Normally they come with a short cable, but you can also get a 6 + foot long cable if you want to mount the display far away from the BMS.

Tip: if you have more than one BMS once you set the address with the dip switches, the BMS will rename starting with 00, 01, 02 etc. You can connect up to 16 BMS’s together for communication. The numbers for the first battery starts at zero so battery number eight is actually end ends with the serial number 07.

Tip: if you have more than one BMS, it helps to write the serial number on the BMS so that you can make sure you’re changing the settings on the correct BMS. I have mine all labeled since I have 16 different ones. And of course, remember that device zero is your first battery and so on.

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Battery Set Up.
Since the cells were already packaged in 12 V packs that sort of limited the options in terms of set up. I ended up doing a square layout and connected them with some flexible copper bus bars to make 48V packs. Also, since everything was in a 12 V pack without high-current access to busbars (can't wire 8p16s, only 16s8p), that meant every 48V pack needed one dedicated BMS. So for my 190 kW of storage I would need 16 BMS‘s for each 48V pack. By the way, the limit of addressing for closed loop communication on the JK is 16 BMS. You can connect other batteries, but they have to be open loop then. They should follow charge of discharge same as the other batteries but you won’t get any SOC readings. But it should still follow. I haven’t tried it yet, but that’s the way it’s supposed to work as I understand it.



TIP: Kommando says that SOC % is just a number. Pay little to no attention to it. It is the battery voltage that is important. SOC does drift if the batteries 100% SOC is not reset regularly. SOC reported to the SI is just the pure average of all the individual readings. As soon as 1 battery SOC goes to 0, the average still remains the same and battery continues to function normally until the low voltage set points are reached. I have had as much as 30% difference in SOC, but voltages are all the same. The battery with the low SOC probably has the same amount of energy in it as the others, but the meter is just counting it incorrectly.

Polaris Bus Bars.
When Hedges and I were talking about how to put the system together, he came up with a great idea of using a dual sided Polaris as a bus bar. Pictures below. I used 250 MCM dual sided six port Polaris connectors. One for each set of eight DC+ and another one for each eight DC- wires. Times two for 16 packs. In my particular set up, each battery would need 5 1/2 feet of wire from the battery terminal to the Polaris. Since we were using pass-through port Polaris, I cut 11 feet of cable, took the insulation off the middle and inserted it into the Polaris. I did put some 1/0 Ferrules over the wire to protect it from the nut in the Polaris. Since the ferrule wouldn’t fit over the insulation, I ended up cutting two ferrules in half and covered the copper wire that way. The outer ports of the Polaris go out to each battery pack and either have another ferrule on them or a lug. In the middle four ports, two holes are meant to go to the Sunny Island DC terminals. These seem to work pretty well. Been running the proof of concept design for about four months now without any major troubles. For the proof of concept shelf, we used a Costco shelf with some cement board on the bottom and cement board all around for protection. Each shelf contains 2 pcx x 48V packs. I also use some Don Rowe 200 amp class T fuses for each 48V pack. We decided not to add a breaker for the time being as that just adds another part that could potentially fail.
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[Calvin98]

The cabinets.
One of the first considerations with lithium batteries was to keep everything safe and not keep them inside the house or near anything flammable. I read about that unfortunate incident with the house burned down due to the lithium batteries (LiFePo). Want to avoid that at all costs. I had some custom cabinets made for me as shown. These are nice heavy duty cabinets and can support the weight of the batteries easily. Nice thick metal that should do well in case of any disaster. Cabinets are large enough and the shelves spaced out far enough so that you can work on the batteries easily. I tried to minimize the number of holes in the batteries for fire protection, but I did have to have two pieces 2 inch holes to pass the positive and negative battery leads from one cabinet to the next cabinet. I ended up getting a conduit knockout punch from Amazon. That does a really nice job of cutting large round holes. I did also put some cement board on the shelves to reduce the bending from the weight of the batteries. At some point in the future, I’ll have to add some sort of bracket to the bottom of the shelf to keep everything nice and flat. But also since I’m using flexible bus bars, each battery can move independently from the others without causing problems. Hopefully, if any disaster happens, it will be limited and contained inside the metal cabinet. I wanted to get the cabinets small enough to fit into the shipping container, but large enough so that I could work on any individual battery. As it is, there’s room for one more 48V pack on the bottom and if I ever decided to add more, there’s probably enough room for another one battery in addition. So each cabinet could potentially hold six packs.

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[Calvin98]

BMS mounting.
In my proof of concept layout of the batteries in the Costco shelf, I hadn’t yet figured out a good way to mount the BMS to the batteries. Initially, I took some cable tie holders with double faced tape, and stuck them to the side of the battery case and then used cable ties to attach the BMS to the battery. I also used some Velcro with adhesive to attached display to the battery case also. This didn’t work out so well. The heat of the summer and the weight of the BMS just made all those plastic holders come loose. In the end, I did figure out a good solution though. I used some 3 inch angle brackets from Home Depot And bent them a little bit and attached to the existing holes in the top of the battery. This works out pretty well. The BMS is only attached to one battery and the space between the BMS and the battery for air circulation. The bracket is robust enough to hold everything securely. Used some M4 screws and lock nuts to attach the BMS to the brackets. Those I attached somewhat loosely but still secure enough so that nothing will fall off. Still need to find a good way to mount the displays and the PCB board. Found two 3-D printable options that might work.

Still need to figure out a place a to mount the displays and boards.

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Link for display

https://www.thingiverse.com/thing:6751498


Link for PCB board print

https://www.thingiverse.com/thing:6571347



Heating pads.
The batteries came with built-in heating pads. I connected all eight 48V batteries in series. When 120V is connected across the heating pads they pull about 3.5 A of power and that’s enough to heat the batteries slowly. Once they’re in the cabinets then I’ll have to adjust the heating time as needed. Probably can have the battery heat to 25°C during the day and then turn the heating off at night. Since they’re in cabinets in an enclosed container, the residual heat should be more than enough to keep the batteries warm until the next morning. Right now on an exposed set of batteries I’m getting about 6 kW of power used to keep the batteries at 20°C here in the winter time. Outside air temperature is about 9° in the morning. Once they’re in the cabinets and closed from air circulation the heat loss should be less and I should be able to get that 6 kW down quite a bit.

Link to Amazon temperature controller.

https://www.amazon.com/gp/product/B0D2SS4RBJ?ie=UTF8&psc=1




Problems.
During the initial set up, we had a problem with the Sunny Island thinking that the batteries were at 0% SOC and then it would do a shut down. We set up a raspberry pie in Home Assistant that records all the data. We basically threw everything at it to figure out that SOC problem in the end it turned out to be fixable with a firmware update on the Sunny Island. That took several weeks of troubleshooting.

SI SOC going to zero link
Link to the battery SOC problem.

https://diysolarforum.com/threads/n...t-up-problem-and-solution.91583/#post-1244119



The other problem we had was that the Sunny Island suddenly went to 70 Hz one day. I posted a link to the prom and solution here.



Link to the Sunny Island 70 Hz problem.
https://diysolarforum.com/threads/s...0-hz-problem-and-solution.93481/#post-1277186

Note: Had it happen again when I connected the other 8 packs. Adding 4 more packs was ok for communication. As soon as I added 4 more, the SI wanted to ramp to 69 hz again. Fixed it temporarily now by not having communication on the last 4 batteries. They are connected to the other packs, they charge and discharge the same but there is no communication. Seems to work fine, but need to get to the bottom of why the Si is ramping up frequency any time 1 more battery is added.

 

[Calvin98]

The Generator.
We have a 20 kW Perkins diesel generator as back up for charging. Has a nice small 4 cylinder Perkins diesel engine with a Stamford alternator. Had an extra large 150 gallon storage tank built onto it for extended run times. It’s a really nice, quiet running generator. You can stand in front of it and hear yourself talk still. My old small 5000 W Coleman you had to wear earmuffs when you got near it. That thing was really loud. One of the nice things about the diesel generator is that it runs at 1800 RPM instead of the 3600 RPM that a normal gas or propane generator runs. Half of the engine speed plus the enclosure means a whole lot less noise. But still when running the generator, we can add about 10% charge to the battery every hour. When you think that we have to run the generator for 10 hours to charge the battery full when the sun can do that from PV for free Every day it’s kinda amazing. With only half of the 16 batteries installed, we only had to use the generator two or three times during the winter to charge up the batteries when we had four or five days of no sunshine. We are using the mini split A/C for heating in the Winter. We also added and ESP32 board to the generator and connected to to Home Assistant via ethernet so we can turn the key on remotely, we can also start and stop it remotely.

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Home Assistant.
We monitor everything through a raspberry pie with Home Assistant. Works pretty well so far. And we record all the data. We also have an Emporia monitoring individual circuits. Both of those items help when troubleshooting. You can identify different loads and different times when things happen. Plus you have all that history. You can go back to it any time and that helps with trouble shooting.
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Link to Home Assistant post.

https://diysolarforum.com/threads/s...-6048us-monitoring-with-home-assistant.91280/



The Future.
The idea is to mount these four Sunny Island‘s and four cabinets of batteries into a refrigerated shipping container. Either 20 foot or 40 foot. Refrigerated container because it’s already insulated and made of stainless steel and aluminum. Very little or nothing to burn in there. Plus, it’s a turnkey solution. If you get a normal shipping container, you have to insulate it first. That’s a lot of money and takes a lot of time and you end up paying about as much as you would for a refrigerated container. In the summer will also use a mini split to keep everything cool inside. Depending on the temperatures, we could also use cool outside air for cooling.



The dream set up would be like this:
Victron container link.

https://www.google.com/search?clien...ate=ive&vld=cid:261eb24a,vid:Lj2L8hcCKfs,st:0



Since I have extra batteries and extra Sunny Island‘s, I’ll also set up a split phase 2 Sunny Island system with 44 kW of battery storage as back up. That would let me keep power in case the 24 kW system needs maintenance or goes down for any reason. It might be set ups with an automatic transfer switch or it could be a manual transfer switch or even both. Neither will be grid connected in general. We do have the grid, but not using it.



Had an interesting call form the utility one day. Guy said he wanted to come by to replace the meter because it was not working. I told him that is was fine, that I just turned the main breaker off. Apparently, the utility gets a flag is someone does not use power anymore and they get worried. He says many of the older meters were failing and insisted on replacing it anyway. Another weird thing that happened later was that we did not get a bill that month. Now, another month later, there is apparently a bill, but with $0 owing.

So far, we have 186 kWh of storage up and mostly working. We’ve made it through the winter solstice and only had to use the generator to charge the batteries three times or so. With the other 93 kWh of storage we should be OK year-round. But have to see. Need extra for EV charging also. “Mostly” because the last 4 batteries are connected to power, they charge and discharge as they should, but communication does not work.



Tip: you can connect more than 16 batteries to the JK. The other non communicating ones follow the “communicating” one in charge and discharge pretty well.



Work in progress…

 

[Calvin98]

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[Calvin98]

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[Calvin98]

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[Calvin98]

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[1201]

Bro!

 

[Hedges]

Thanks for blazing the trail ahead of me (and making multiple runs to San Diego for the battery purchases we split.)
You struggled through several problems so now I can avoid them. One of the toughest to figure out was that SI needed to be updated to latest (ca. 2020) firmware so it didn't randomly get confused about SoC and shut off.

My NEM 1.0 ends and I get pushed onto Solar Billing Plan March 1st 2025. That means my backfeed will be credited about $0.02/kWh and I'll buy power for $0.40 to $0.60/kWh.

All I've got going so for is SMA SBS & LG RESU-10H, which is only giving me 7.5 kWh capacity now, not the 9.2kWh I saw initially. I use that up early evening and draw from the grid for the rest of the night.

I need to reconfigure from my 4x SI & 20kWh (gross) 14kWh (usable) AGM "Grid Backup" to 2x SI & LiFePO4, "Grid as Generator" so I don't buy any kWh.
I don't think I'll have that done in time, will probably just flip the switch back to gas heat.

My CATL & JK battery, probably 96kWh, will get hung on a retaining wall away from the house and covered in foam board.
I'll hook up thermostat to power their heating pads like you did.
I am considering A/C to keep it from getting above 70F, although I hope earth behind retaining wall keeps it cool. Probably need a vapor barrier there.