My goal was to see if I can keep them at between 80-20. I hope that I will have plenty of spare capacity with storms, snow, that we get. Sort of the same thoughts with over-paneling as well.
Help with 128 batteries each one is 280ah, and want to configure for 48v system.
- Thread starter kromc5
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I'm cycling my four 16s banks 20%-90%. 20% gives me enough capacity so I can do something in case generator doesn't start. It's all about winter. In spring, summer, and fall, the battery will never see 20%. So same train of thought. I use a single Batrium which so far is working well across all 64 cells. Max delta I see is .03, but the Batrium with blockmon 8s balances that right out.
Shawn Hayes
Learning Everyday
Are you using 64 M-8’s?
Shawn Hayes
Learning Everyday
Good to know. Currently balancing 64 cells. I am planning to build a 4p16s, but been having an internal debate about changing to a 16s 4p setup. I have a Batrium and 16 M-8s currently. So it seems you have a 16s4p with 64 Blockmons and works great...
so that makes me reconsider my layout. Would need to order more Blockmons however. I like that 16s4p layout for redundancy factors.
Any pointers you can add?
Thanks
I think it's just a matter of preference. I started out going the parallel cell route and then changed my mind. After that, my plan was to make parallel strings and if they couldn't balance, I would just switch over to parallel cells. But balancing doesn't seem to be a problem. My charge controllers are set to 56.6 absorb which is ~56.2 at the batteries. At the end of absorb (15 minutes) the lowest cell is 3.50 and the highest 3.51. Balance volts is set to 3.51. 3.51*16=56.16v which is close to the 56.2 charge rate. I also have two strings with welded studs and two without and so far this difference doesn't seem to matter.
I like multiple strings because if a cell goes bad, I can just drop a string and have power while I work on the bad cell. I can also more easily figure out which cell is the problem cell. In addition, the blockmons have more balance capability when using multiple strings because it's one blockmon per cell rather than one blockmon per 4 cells. But, this configuration is more expensive: more blockmons, battery cables, and fuses. It also means that if you drop a string, there is a bit of a process to add it back so that each string is at same state of charge. You have a similar problem with parallel cells. Bad cell means take apart the battery, reconfigure for 3p, fix problem, get that (or replacement) cell back to same state of charge as others, then reconfigure for 4p. In either situation, the bad cell problem isn't good. But it's really a matter of preference.
I think some of the negativity on parallel strings is when people use multiple bms and contactors. In this situation, strings can become out of sync relative to state of charge when for example a bms drops a string out and the other bms don't and then the bms that dropped randomly onlines the dropped string at a later time. Now you likely have one string that has higher or lower state of charge than the other three.
I would recommend buying an extra blockmon or two. I had either a bad blockmon or a bad blockmon cable. It would intermitently flash 0v or some low voltage during balancing. I suspect heat was involved. It would throw a low cell voltage fault and offline the battery. I initially though connections, but redoing them made no difference. Fortunately I had bought two extra blockmons, so I swapped in a new one and no problems since. I need to buy a couple more to have on hand. On the same note, I wish I had bought a couple extra cells. I probably should do that.
I like multiple strings because if a cell goes bad, I can just drop a string and have power while I work on the bad cell. I can also more easily figure out which cell is the problem cell. In addition, the blockmons have more balance capability when using multiple strings because it's one blockmon per cell rather than one blockmon per 4 cells. But, this configuration is more expensive: more blockmons, battery cables, and fuses. It also means that if you drop a string, there is a bit of a process to add it back so that each string is at same state of charge. You have a similar problem with parallel cells. Bad cell means take apart the battery, reconfigure for 3p, fix problem, get that (or replacement) cell back to same state of charge as others, then reconfigure for 4p. In either situation, the bad cell problem isn't good. But it's really a matter of preference.
I think some of the negativity on parallel strings is when people use multiple bms and contactors. In this situation, strings can become out of sync relative to state of charge when for example a bms drops a string out and the other bms don't and then the bms that dropped randomly onlines the dropped string at a later time. Now you likely have one string that has higher or lower state of charge than the other three.
I would recommend buying an extra blockmon or two. I had either a bad blockmon or a bad blockmon cable. It would intermitently flash 0v or some low voltage during balancing. I suspect heat was involved. It would throw a low cell voltage fault and offline the battery. I initially though connections, but redoing them made no difference. Fortunately I had bought two extra blockmons, so I swapped in a new one and no problems since. I need to buy a couple more to have on hand. On the same note, I wish I had bought a couple extra cells. I probably should do that.
Shawn Hayes
Learning Everyday
Yeah I agree with a lot of that and is why I’ve been internally struggling with which way is best. The only question I can think of, you’re only using one ISOmon cable connected to the Batrium to daisy chain all 64 Blockmons together as one continuous pack? Even though you actually have 4 separate packs? Just verifying...
Thanks for the experience/advice!!
Edit: When I ordered my 64 cells, I ordered 4 extra just in case some got damaged in shipping. I read your earlier post about having a bad Blockmon, so I would definitely order a few extra just in case.
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They are daisy chain along one bank from most negative to most positive, then the cable goes to the most negative on the second bank, and so on. That's how the Batrium docs say to lay it out but I don't see a reason it would matter. I had to lengthen the cables between banks.
@jtvt nice recap earlier on your thought process. Do you have any pics / diagrams of how you built your battery banks?
Shawn Hayes
Learning Everyday
Yeah I’d like to see how you hooked up your inverter to your battery banks so you would NOT combine all 4 banks volts into one, maintaining 48v system.
I'm not sure what you mean. I used to have a 24 volt lead acid system and moved to 48 volt lifepo4. I ended up completely rewiring the dc side and still have to rewire the AC side. It's still in transition. So here are the old 24v inverters with new buses for the newer setup plus batrium. Those two inverter were removed and replaced with a single larger 48v inverter.
Here are the original two strings wired in and then the new cells on the top shelf. At this point, the string on the top shelf back had been top balanced and I wired the other top shelf string in parallel so I can put the power supply on it. I compress the cells, then use a qucc bms and charge controller to charge the strings until the high cell volt cuts out, then I rewire for the power supply with jumpers I made.
And here is where things are right now. Still a remanant of the old 24v inverters on the wall. That gets removed and the breaker box moved. Then also there will be wire cleanup and covers put on the bus bars, plus some supports made for the battery cables. Off to the right are the panels that house the shunt trip breaker and charge controllers
Here are the original two strings wired in and then the new cells on the top shelf. At this point, the string on the top shelf back had been top balanced and I wired the other top shelf string in parallel so I can put the power supply on it. I compress the cells, then use a qucc bms and charge controller to charge the strings until the high cell volt cuts out, then I rewire for the power supply with jumpers I made.
And here is where things are right now. Still a remanant of the old 24v inverters on the wall. That gets removed and the breaker box moved. Then also there will be wire cleanup and covers put on the bus bars, plus some supports made for the battery cables. Off to the right are the panels that house the shunt trip breaker and charge controllers
Sanwizard
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Nice setup. I had put my first two banks in an aluminum toolbox, but i see now that a sturdy shelf system enables much better scalability.
Shawn Hayes
Learning Everyday
See yellow square highlighted area in photo:
This is what I was curious about. How you ran your cables from batteries to connect to your inverter/s?
My assumption is, using “bus blocks or terminal blocks” your voltage is still 48 volts even though all 4 battery banks are landing on the bus/terminal blocks. So your inverter will hookup to the other side/opposite posts from where your negative/positive terminals land on the bus or terminal blocks? Yet still maintaining a48 v system.
Looks great!!! ?
Thanks. That shelf was bottom half of this unit:
Husky 5-Tier Heavy Duty Steel Garage Storage Shelving Unit in Silver (48 in. W x 78 in. H x 24 in. D) MR482478W5 - The Home Depot
You can assemble this heavy-duty steel shelving unit vertically as shelves or horizontally as a workbench. Its neutral color goes with everything in your home. You can adjust this multipurpose unit's shelves in 1.5 in. increments to fit any storage need. It features a rivet lock system that...
www.homedepot.com
Supposed to be rated for 1000lbs per shelf though I can't imagine actually putting 1000lbs on each shelf. Two strings with wire, etc is ~350lbs.
thanks. A cable from the positive battery bus runs to a busbar in the panel that has the shunt trip breaker. This bus bar is on the shut trip output side. A cable from the negative battery bus runs to a string of 3 shunts. One for the batrium and one for each of the midnite classic charge controllers. The schneider electric battery monitor is doubled up on one of the controller shunts.
Sanwizard
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Where did you get the massive busbars? They look commercial, and not DIY. Is there a link?
They have 5/16 and 3/8 so u got to make sure you get the ones u want
Sanwizard
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Awesome! I LOVE Blue Sea Systems products. They also have GREAT support.
Thanks!
Agree. I use the same shelf but I added 3/4" plywood that spans just beyond the side braces for added strength. Makes a word of difference I think.
Bluesea makes great stuff, I was able to get 3 of the powerbars from here at a good price. I orginally had planned to do 8 16s, thought about a 32, but decieded to try the 4p. It this should give problems I can easily converter to the 32, as the bulk of the busbars will fit.
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