Renewable Energy Questions/Discussion > Renewable Energy Q&A
Charging and Using Lithium Ion 18650 Batteries
rossw:
--- Quote from: Pete on January 02, 2019, 08:55:07 pm ---Hi Ross, just wondering . Did you have to change regulators?
--- End quote ---
I didn't have to change anything at all. I used the same inverter, charge controller, switchgear, everything.
I will admit I tweeked some of the settings to better suit the different technology.
--- Quote ---Your system is big by my standards. We use 12 volt and have 660 amp hour batteries, so 900 amp hour 52 volt is huge to me.
What batteries did you use?
--- End quote ---
The first lot were from a company whos name I now can't remember, but who made the best prismatic 300AH cells for my application at the time. When I went back for more, they were gone and I had to find another supplier. Many more to choose from, but lots of rubbish in there too.
After all my research, I elected to use only the prismatic cells, and so far I've been completely happy with that choice.
--- Quote ---I will look at Life Po4 when my current batteries die, which hopefully won't be for another 20 years. Who knows what will be the new chemistry then.
--- End quote ---
Yeah, I doubt it'll be LFP in 20 years!
solarnewbee:
Hi Ross!
Finally got my system up and running and went with 32 200ah lfp’s. Bit of a learning curve charging these things. I bought 2 off brand mppt chargers I setup according to the book but I’m still not sure if float and refloat and absorb rate are correct.
Found out quick this 24v PJ won’t run everything in this place all at once. Pulled out the manual and it does show 3.5kw is the limit for a 8kw. I will be bringing over a 15kw next year.
I almost bought 12 volt lfp packs that had built in bms with cutoff charging relay but then found out they were populated with 18650’s. I just don’t think I can trust all those cells lasting. If one cell goes, so goes the the pack?
rossw:
--- Quote from: Solarnewbee on January 18, 2019, 02:02:15 am ---Finally got my system up and running and went with 32 200ah lfp’s.
--- End quote ---
They look quite similar to my second bank, although of course you've hooked 'em up differently.
I went 16S of 3P (ie, 3x200AH in parallel, in series with 3x200AH in parallel, in series with....)
I'm sure you'll be loving them.
--- Quote ---but then found out they were populated with 18650’s. I just don’t think I can trust all those cells
--- End quote ---
Yeah, I found quite a lot like that, and it scared the willies out of me. I rejected anything that said it had "cylindrical cells", and by the time I was ready to buy, if it didn't specifically say prismatic, I crossed it off my list!
Good to see the progress!
solarnewbee:
Just awoke to low batteries again. Family plugged in 2 e-bikes to charge and the system ats did its job. I noticed the data on the bms shows the first 2 blocks show 3.032v whereas the others are at 3.1v. Apparent I need to equalize them so I was wondering what you would do. 8 blocks in series for 24v 4 sets in 2 banks. The bms is only reading the first 16 blocks since I haven’t purchased additional sensors. Been so busy working on the house I haven’t even put a meter on them. I’m going to keep the inverter off for 24 hours and see if they reach float and check each cell.
Ok now for the dumb question. “Never disconnect under load”. Should the battery always disconnect first before hitting the pv breaker? Silly questions but after reading threads here and many places some things are just not covered.
I was building the battery bank and needed longer bolts for the cable connectors. Every hardware store had standard thread in a country that uses metric. One exception, Ace Hardware! 2 drive, only in the Philippines 🇵🇭.
William
lighthunter:
So, you have four series strings 8 cells each? Then you paralleled the 4 strings?
Some ppl go off when they see someone using an LFP without BMS on every cell :)
The real world always brings challenges and necessities. I understand completely.
Your existing BMS has done a good job so far and the variance of .068 is not a problem
since you are stopping discharge at 3v. I personally wouldnt touch them with anything
but a meter for now as long as they are all that close to each other. Others may disagree but
always maintain bottom balance (never never top balance) especially if some cells are unmonitored.
Through their life there will be differences in cell capacity and you wont loose a cell if the voltage goes a little high on one but if voltage goes low on one during discharge the stronger cells will run over it and kill it. (that assumes no bms monitor of course). Be careful of factory BMS monitors that leak power from cells unequally and cause unbalance. One such device is the (cellog8S). It works great, graphical display and recording etc, but leave it
connected for a week and expect unbalance. They use the first two cells to power the device. It isnt worthless however, very useful with a connector to temporarily monitor, record details. With your investment you probably want a better BMS with auto balancing. Choose carefully when deciding on BMS equipment though, often times BMS curcuits are less reliable than LFP cells and a bms failure in worst case can ruin a cell. Fun stuff! :)
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version