I nearly have WuPoG dialled in. LVDs, HVDs, effective capacity, thermal management, discharge/charge aperture, low temp foldback, critical disconnects, meter calibration etc. etc...
I may have mentioned how clever the Swiss are. It's next level, nobody can touch them, this is one of the few products I can't find fault with (Jury's out on the charge algorithm...I'll follow that up some time, for the moment I'm still seeing MS do better)
This:
Actually works.
It's impressive.
I'm a little underwhelmed with Li-ion. It's a lighter alternative the rest is marketing.
Soo finicky and complicated and this BMS lark and not integrative with conventional hardware.
Eg Li-Fi versus Lead-Fi Application Notes.
Anyways I can charge extra because it's fashionable
And she's already about 120kg...sooo yeah, there's that.
She's been derated.
Perhaps it's more accurate to say she was over-rated.
She's 18S 72A CALB LiFePO
4 bricks.
This amuses me because the market says "48volt" compatibility is 16S, there's an example of not thinking (maybe). 12v is 4.5S making 24v 9S I am guessing they say 4S for convenience and then times 4 etc.
Another thing people say is you can use 100% of the battery...you can't but the bit you can't use is hidden by the BMS. Some are designing to 90% (short cycle life) whereas the more prudent are operating to 70% (longer cycle life).
From what I've seen the extra 20% can >quadruple the extracted energy 100% depletion = 600 cycles, 70% depletion = 3000 cycles.
What pi$$es me off is when they say it's good for 3k cycles and then BMS it to 1k cycles for outtov the box performance...a rather all too common practice. Is it lying, is it marketing? You decide.
I'm working to 60% depletion because I know people and the first thing anyone does with a show battery is plug it in all day until they need it. I've limited the Absorption to prevent heat-induced plate deterioration and placed a dump excess to grid low float reduced SOC for on charge storage. This battery storing at 50% is not as good as lead's 100% for a lottov applications outside of underspec-ed input systems.
I have to leave overhead on the bottom end too because those same people are unlikely to charge it after they are done, they'll just stick it on a truck and ship it back to me after storing it in their warehouse over the weekend.
WuPoG is now 2.5kWh
With an impressive 80% empirical NOC round trip efficiency.
So how on earth is a >4kWh battery producing so little.
Here's my operational envelope
Graph taken
from here. That author has inspired me to believe he's smarter than your average bear and the info therein is unbiased.
I've 18 x 3.25V cells x 72Ah = 4.2kWh + 10% because they are genuine CALB = 4.6kWh
I'm using 60% (not a far cry for 50% lead acid is it?...but arguably I can use 70% lead because I can overcharge and offset reduced cycles against linear cost per kWh)
60% of 4.6kWh = 2.8kWh
@ 90% inverter efficiency = 2.5kWh
Truth hurts. I think that's a ~€2k battery (before the BMS). I can pull 4kWh from a 24v flooded golf cart battery no BMS because the expense and volatility of the battery doesn't warrant one beyond the inverter protections for about a quarter that cost...
I think I'll start pushing Oasis Firefly AGM, people don't like flooded. I'm not convinced Li-ion brings much to the party in a static application.
