diy solar

diy solar

LTO cells on Batteryhookup.com

Anyone find a good affordable LTO BMS for it? The challenge is each pack is only 20ah. So, it is overkill to put a 150ah BMS on it when you need 10 of them.
 
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Hi - what configuration will you be using to make the pack I.e for 12v you will need 5 and to increase the aH you will add more in parallel. So for this you could use the Daly LTO BMS. It is pricy at $160 but these things seem bullet proof. I believe they are bringing out the bluetoooth version next year.
Found one - 5S 80A - AU$75
 
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It's a lot more work to convert to 12V. I'd just want to put a 10S BMS in each 24V pack. If the only option is the oversized Daly, you would have to reconfigure to bring down the price.

In that case, you might just reconfigure each 10 cell pack to be in parallel, then run 10 of those in series. Ideally, you'd throw that in some bigger enclosure. "Each pack is 8x7x6 inches". Your 200ah 24V 2-row pack will be 2.5-3 feet long, and weigh over 110 lbs.
 
erik.calco said:
It's a lot more work to convert to 12V. I'd just want to put a 10S BMS in each 24V pack. If the only option is the oversized Daly, you would have to reconfigure to bring down the price.

In that case, you might just reconfigure each 10 cell pack to be in parallel, then run 10 of those in series. Ideally, you'd throw that in some bigger enclosure. "Each pack is 8x7x6 inches". Your 200ah 24V 2-row pack will be 2.5-3 feet long, and weigh over 110 lbs.
Click to expand...
That's a good idea to put each box in parallel but realize that to run an inverter at 24 volts you need 12 s. Not 10 s at 10s most of power will be produced at only 20 volts.
 
Craig said:
That's a good idea to put each box in parallel but realize that to run an inverter at 24 volts you need 12 s. Not 10 s at 10s most of power will be produced at only 20 volts.
Click to expand...
It would be 20-26V at 10S:

1577545284940.png

I'd OK with a 20V cutoff. The capacity would be more limited if I put in parallel with my current LFP bank running 22-27V. It would be closer to 50% DoD at 22V, though this depends greatly on discharge rate.

But, maybe 11S if I wanted more capacity with current bank.

Note that LTO is friendlier with floating and overcharging. This has an intro to LTO.
 
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SolarRat said:
But is your inverter OK with it? You won't get much run time with 5s. Lots of your capacity will be below 12v...
Click to expand...
Low DC cutoff range available is 20.4V to 24V for my inverter. 11S probably makes the most sense to be inline with 8S LFP as well as just work well by itself, but 10S would work by itself with a 20.4V cutoff.
 
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Craig said:
Don't pay attention to that graph I have tested about 50 cells and 50-60 percent of energy comes at the 2.0 to 2.1 volt range
Click to expand...
In theory, that would suggest you are using a high discharge rate.
 
here is a link to a spreadsheet with my data

docs.google.com

Cell Test through voltage Ranges

Sheet2 61,069CGA2064061J93T0003572 Total,43.2459 95.00%,---->,2.43 50.00%,---->,2.13 20.00%,---->,2.05 5.00%,---->,1.97 62,069CGA2195061J8CK0000503 Total,43.4514 95.00%,---->,2.38 50.00%,---->,2.09 20.00%,---->,2.01 5.00%,---->,1.93 63,069CGA2202061J8C00000875 Total,43.7642 95.00%,---->,2.45 50.00%
docs.google.com docs.google.com

this is only 4 cells

it shows at each .1 V how much energy is produced with a .3C discharge rate.
 
this is broken down to .01 volt its raw data from my test rig
left column is volts right is Ah produced
069CGA2064061J93R0003395
2.49 0.0739
2.47 0.0622
2.45 0.1218
2.44 0.1203
2.43 0.1788
2.42 0.4146
2.41 0.4124
2.4 0.3523
2.39 0.4679
2.38 0.3497
2.37 0.5222
2.36 0.3465
2.35 0.4596
2.34 0.5149
2.33 0.5139
2.32 0.5126
2.31 0.4545
2.3 0.5102
2.29 0.5089
2.28 0.3942
2.27 0.5609
2.26 0.5588
2.25 0.556
2.24 0.5527
2.23 0.4952
2.22 0.6028
2.21 0.7109
2.2 0.491
2.19 0.707
2.18 0.6504
2.17 0.7022
2.16 0.6995
2.15 0.9104
2.14 0.7982
2.13 1.1742
2.12 2.3242
2.11 1.7402
2.1 2.9939
2.09 1.7782
2.08 2.028
2.07 1.8171
2.06 1.707
2.05 1.6492
2.04 1.4888
2.03 1.2783
2.02 1.2226
2.01 1.0147
2.0 1.0102
1.99 0.6538
1.98 0.601
1.97 0.5484
1.96 0.298
1.95 0.2967
1.94 0.1968
1.93 0.1469
1.92 0.1463
1.91 0.0971
1.9 0.0967
1.89 0.0962
1.88 0.0479
1.87 0.0477
1.86 0.0948
1.85 0.0471
1.83 0.0469
1.82 0.0466
1.81 0.0463
1.79 0.0459
1.78 0.0456
1.76 0.0451
1.73 0.0446
1.71 0.044
1.68 0.0433
1.64 0.0424
1.6 0.0415
Total 43.4216
 
Craig said:
here is a link to a spreadsheet with my data

docs.google.com

Cell Test through voltage Ranges

Sheet2 61,069CGA2064061J93T0003572 Total,43.2459 95.00%,---->,2.43 50.00%,---->,2.13 20.00%,---->,2.05 5.00%,---->,1.97 62,069CGA2195061J8CK0000503 Total,43.4514 95.00%,---->,2.38 50.00%,---->,2.09 20.00%,---->,2.01 5.00%,---->,1.93 63,069CGA2202061J8C00000875 Total,43.7642 95.00%,---->,2.45 50.00%
docs.google.com docs.google.com

this is only 4 cells

it shows at each .1 V how much energy is produced with a .3C discharge rate.
Click to expand...
Where did you get the cells from that you are testing?
 
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