Recommendation to expand the capacity of my battery

[lukassteiner]

I am seeking your advice on what to buy to increase the capacity of by DIY battery bank.

Currently I have a 16S, 48v, 200Ah battery bank with blue CALB cells and a Daly BMS.


I get about 5kWh capacity when I run a capacity test on them.

I would like to ideally have a battery capacity of 10-15kWh.

The options that I see are:
Buy another 12 CALB cells and a Daly BMS for 700 USD -> 5kWh more capacity (I already have 4 cells laying around that I don't use at the moment)
Buy a 10kWh server rack battery for 2200 USD -> theoretically 10kWh more capacity

Important note: I live in Thailand and shippings from China are super cheap and fast to Thailand. Getting products from the US is however very costly and takes a long time.
My stores to buy from are aliexpress.com and lazada.co.th

Additional to either of these batteries, I will need to buy a class T fuse and a busbar to connect the new and the existing battery in parallel.
To connect them safely, I would follow this video from Will.
I will need to buy this from Europe or the US as I did not find either of these products in a Thai or Chinese shop with good enough quality and it will cost be around 150USD.

Given my circumstances and needs, which option would you go for from your experience and why?
Or is there an other, potentially better option that I have not seen yet?

Thank you for your help!

 

[robby]

Since you can get the cells cheaply from China I Would assume you can also get some of the same rack mounted batteries sold in the USA but under different brand names.
I would first check out what that would cost.

 

[100kwh-hunter]

Also negotiate with the seller if they are 80% under advertisement--->free return.
Dont buy waste.

 

[DIYrich]

I am seeking your advice on what to buy to increase the capacity of by DIY battery bank.

Currently I have a 16S, 48v, 200Ah battery bank with blue CALB cells and a Daly BMS.


I get about 5kWh capacity when I run a capacity test on them.

Shouldn't 200ah @ 48v be closer to 10kWh? I would figure out that problem before investing in more batteries. If they are near end of life, dump them and possibly reuse the bms on 300ah cells.

 

[lukassteiner]

@robby Thanks. I will check that. I assume they are in the range of the second battery that I linked. Around 2000 USD for 10kWh
@DIYrich Yes it should. How would you go about figuring out that problem and potentially fixing it? Capacity test every single cell separately? How do I know if they are new end of life?

 

[DIYrich]

@DIYrich Yes it should. How would you go about figuring out that problem and potentially fixing it? Capacity test every single cell separately? How do I know if they are new end of life?

Charge at 54.5v and watch the individual cells. Keep charging until the BMS says the cells are balanced (my JK BMS balances to within 0.005v).
Increase voltage in 0.50v increments and repeat until 57.5v. Any cells that tend to lead or lag? Runners?

Let the battery settle. Note any cells that are outliers.

Discharge the batteries to 48v. Any cells discharging faster than others? How many Amps/kWh did you get out?

Let the battery settle again. Note any cells that are outliers.

That may give you some insight into which cells are better and worse than the others.

I'm guessing that your battery lost top balance, and the Daly couldn't keep up. What voltage have you been charging too? What float voltage are you using? How long do you float at that voltage?

If you can't get the cells to balance in a reasonable amount of time (30ma may take forever), then you might need to get an active balancer, BMS with active balance (my vote), or disassemble the pack and use a power supply to balance them to 3.60v. $185 for a JK BMS with 2A active balance may be a cheap way to get back most of the 5kWh you are missing. Then you will know if it is worthwhile to spend on your next battery pack.

Note: Maybe get the JK BMS for your next pack. Use it to charge up and balance the new pack. The swap the BMS with your old pack, and let the JK work on that pack. If the Daly pack becomes unbalanced, you can swap BMS again. A lot of work, but saves you some money.