making a battery for my Skybox, supplier and misc questions.

[Dforster67]

I've read a lot of information here, but figured I start my own thread to get individual advice and give everyone a new user to pick on..

I am planning to get 16 270 ah cells from Michael C from this forum, I don't know the details of his cells but trust him from what I've read and chatted with him for a while. He's also going to provide me the daly 200amp 48v bms for my project. I expect to have them pretty soon so need to gather my other stuff up.

My application is just home use, I have a single skybox with 5.3kw of dc solar input, all setup and running on a grid zero setting currently. we use about 15-30 kwh/day depening on AC use. without AC we are only using about 15 kwh. I do hope to get a day or two of backup with the batteries and plan to add another 280ah bank soon. My critical loads never go above 25 amps (basically everything except the electric water heater and the AC and dryer), and normally we idle around 500 watts during the day w/o AC or dryer & hot water so we could get by on 4kwh easily if needed. So the battery banks are twofold, 2-3 days of critical loads backup (12wkh over 3 days) and when we get the 2nd bank I hope to offset nighttime loads (probalby AC and idle loads equal to around 10kwh/night). And who knows, with a 3rd bank we might be able to go off grid once I replace my electric dryer and instant water heater. We do have propane water heater for floor heat I could divert to our hot water supply, and we use propane for cooking and wood for most heating.

Some of the questions I can think of would be:

1. what various parts and pieces do I need, testers for my 48v battery, wires, lugs, etc. Do I need to test and top balance the cells, etc?

2. is a 200 amp 48v daly going to work with my application? I think it should be ok. I think the skybox battery input is 175amp breaker so that concerned me a little, but I think the skybox should manage the load by combining battery/grid/ and solar so it shouldn't try to get more than 175 amps battery, but I guess I'm not sure about that. If I were just doing the minimal 500 watt critical loads backup it wouldn't need to be 200 amps I think. Is it better to have the larger bms for faster charging also? I'm not sure how fast skybox charges, but does have a 175amp dc breaker. I'm guessing it is able to charge at least at 5kw of solar.

3. For my second bank, I'm not sure who I will use to buy those. I'm hoping Michael as well but he is not sure if his supplier can meet all his needs right now. So I want to find a backup Chinese supplier and get some on the way, I'd be ok with 3 banks eventually if my skybox will support it. Of course the $120 cells from Amy sound like almost a sure thing, but I'd rather find something less than $100 even if I have to test and worry a little..

I have a price from Huizhou Rui Dejin New Energy Co below, seems a little high for a non DIYSolarforum approved seller. But they are one of the first to respond to my request. I also have a better price from Mushang ($85), but read a post on here to avoid them. Also have a reply from Alithor, but they didn't give me a price yet. I expect that tomorrow.

I also have a local guy who resells from china, He sells a lot on ebay but if I pick them up he'll just tack on $100 reseller fee, $80 per cell and $310 total shipping so around $1700 total. I'd drive a couple hours to pickup. These are untested by him but he trusts his supplier and normally does test them I think.

CATL3.2V280Ah Lifepo4 battery
Brand new Class A battery price 95USD
16PCS*95USD=1520USD
Gross weight of battery 90KG
Shipping cost is 375USD
Total total: 1895 USD

Thanks in advance for any inputs! Sorry for the long post. I'm a new poster and love the forum!

 

[Ampster]

.....
Some of the questions I can think of would be:

1. what various parts and pieces do I need, testers for my 48v battery, wires, lugs, etc. Do I need to test and top balance the cells, etc?

I would start with a good quality multimeter with DC current clamp. I found a hydraulic Crimper invaluable. Top balancing is always preferred.

2. is a 200 amp 48v daly going to work with my application? I think it should be ok. I think the skybox battery input is 175amp breaker so that concerned me a little, but I think the skybox should manage the load by combining battery/grid/ and solar so it shouldn't try to get more than 175 amps battery, but I guess I'm not sure about that. If I were just doing the minimal 500 watt critical loads backup it wouldn't need to be 200 amps I think. Is it better to have the larger bms for faster charging also? I'm not sure how fast skybox charges, but does have a 175amp dc breaker. I'm guessing it is able to charge at least at 5kw of solar.

5kW is only 100 Amps at 50 volts. I have limited my charging arbitrarily to 80 Amps. I may make a separate post about my theory about BMSs.

3. For my second bank, I'm not sure who I will use to buy those.

I first started buying cells last Spring when I found this forum. Over the past year I have purchased 48 cells from three different vendors. My last purchase of 16 cells I paid a little more to get the same LF280 cells just to make my pack assembly more consistent. Lishens would have been $200 less expensive. My preference is for one big pack and one BMS so that drove my decision making. There is a good argument for multiple redundant packs.

 

[Dforster67]

I would start with a good quality multimeter with DC current clamp. I found a hydraulic Crimper invaluable. Top balancing is always preferred.

5kW is only 100 Amps at 50 volts. I have limited my charging arbitrarily to 80 Amps. I may make a separate post about my theory about BMSs.

I first started buying cells last Spring when I found this forum. Over the past year I have purchased 48 cells from three different vendors. My last purchase of 16 cells I paid a little more to get the same LF280 cells just to make my pack assembly more consistent. Lishens would have been $200 less expensive. My preference is for one big pack and one BMS so that drove my decision making. There is a good argument for multiple redundant packs.

So does the skybox only charge up to 5kw then? I just assumed since it is a hybrid and is capable of combining grid/solar/battery it might charge more, with the 175 amp dc breaker. Can it also only discharge up to 5kw? if so there isn't much need for the large BMS. although I'm assuming that won't hurt anything and may increase life?

Good idea on the meter. My cheapo one only does AC current.

 

[Ampster]

So does the skybox only charge up to 5kw then?

The maximum setting for charging is 100 Amps and 125 Amps on discharge. The circuit breaker is to protect he wire. I actually used 4/0 wire because that is what I had. I would not use anything smaller than what is rated for 175 Amps based on distance and whether it is open air or in conduit. I do have a small section of #1 AWG THHN in open air but I also have a 150 Amp Class T fuse which is sized to protect that wire.

 

[Ampster]

My philosophy on BMSs is shaped by the fact that I already had an Orion BMS going back to 2015 when I had an Outback Radian at another home. The Orion has great CANBUS communications and is plug and play ready with many standalone chargers available in the DIY EV space. That is their heritage and a hobby that I briefly dabbled in before I got into stationary storage. To be frank there is no support from Outback for integrating a BMS with the Skybox. It is still possible to use a contactor and I am experimenting with using one of the outputs from the Orion to softly turn off the inverter using a relay in series with the RSD controls. I think that is preferable to relying on a Contactor which would create a big shock if it was disconnected under load.

I also have never felt the need for redundant packs so I initially configured my pack as 2P16S. The additional 16 cells I purchased are still awaiting integration into my pack. The 28 kWh of current capacity is adequate for my needs. If I was not wed to the Orion and the information it provides I might consider redundant packs because there are some good BMSs capable of handling half or a third of my maximum discharge. In other words three packs each with their own BMSs would share 125 Amps. Three quality BMSs would cost less than one Orion Jr BMS.

Later we can talk about the different modes available for operating your Skybox, once you get batteries. My external CTs arrive later today and I am anxious to give them a try to maximize my self consumption.

 

[Dforster67]

Not sure I know what you mean skybox won’t integrate with a bms. So skybox won’t support using a diy battery setup the way I want to do it? Maybe I’m missing something.

 

[Ampster]

There is no communication except Modbus that the Skybox can talk to. It depends on what you meant by support? It works to have the BMS shut off the pack with a contactor. I have just used the settings on the Skybox to keep the battery in a conservative range of SOC so the contactor never has to open.

 

[Dforster67]

Ok. So it will work as a "dumb" battery, it just wont' have any communication with the skybox? at this point I'd be fine with that.