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Changing from SLA to LifePo4 batteries
dochubert:
Hi guys,
The second bank running my water heater setup is 6 modules in parallel for 24v. They stay pretty even so far.
The main bank, being 48v, is going to be more challenging. Yes I've watched David Poz' videos on them. He did a great job and I learned a lot watching him before I started with mine. I'm not doing things quite the same as he did, but not that different either. Since there is limited sun in January here, it's been fairly easy so far. 16s bms for balancing on each of the four 48v parallel sets. Haven't got balancing on the 24v bank yet, but working on it. To balance those I either have to parallel all the cells across all 6 or put a separate bms on each. Since I'm only using the bms for balancing, not charging or discharging, I'll probably go with a bms on each. Still pondering...
Ah, politics.
140 M registered voters.
Trump officially got 74 M.
Biden got 80 M.
That's 154 M total votes "counted" out of 140 M?
Yeah, I'd say it's broken. Corrupt beyond repair.
dochubert:
AsI mentioned, I used flattened thick-wall 3/4" copper pipe for my bus bars. 1 pos and one neg. Bought large copper lugs from home depot to put on the battery posts, then bolted thru to the bus bar. Ran new #6 copper wire to each of 4 charge controllers. Still using xantrex c40 for charging. Bulk charge set to 55.2v and float at 54v. As mentioned, charging above 56v leads to unbalances in cells so will try to stay in the narrow range and see how that works out. No higher than 56 and no lower than 48v. Usually between 52 and 55v
Added a temp control and 4 small fans to the charge controllers. Last summer I just set a desk fan blowing on them.
About time I did something better.
dochubert:
Next was connecting up the bms'. Too much trouble using the connectors on the BYD modules so just cut the wires (1 at a time) and connected to the bms wire harness. One 16s bms to span the 2 byd modules in each 48v leg. x4 so lots of little connections.
Just used silicon to stick the bms to the module case.
Then added a little blue voltmeter to each module. They are not super accurate but gives me a ballpark idea of whether cells are even at a glance. Used some plastic wire looms to try to dress up all the leads.
dochubert:
Finally, I added a little blue led to the right of each bms. Since these bms are relatively cheap, I can't monitor cell voltage directly, and I'm not using them for charging/discharging, only for balance. The led just connects to the unused bms' charging lead so it will always be on if the bms is in normal mode. If a cell goes too far out of spec the blue led should go out, indicating the bms has 'disconnected'. Same if the total module charge gets too high or too low.
This summer when I will have 120 to 150 amps going in (thru 4 controllers) I'm hoping these will help me make sure the parallel legs are charging evenly. Also why the charge controllers are set just below 56v instead of the 58-59v the system should be able to accept if it was new. As for now (January) I'm happy on days where there is enough sun to run the house during the day. And of course if the grid goes down I can run for a few hours with minimal usage.
WooferHound:
Wow , Too Cool . . .
Nice to see someone else converting Lead Acid to Lithium.
Would love to hear about the differences you have seen between the two systems ?
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