We take care of Intellectually disable people that do not have family or homes, and they do not understand many of the normal energy saving ideas. And by law we have to leave if we loose power for more than a day to a hotel which is extremely tiring, so we are taking steps to keep the power on and save on monthly costs. I need to take a few pictures just removed the ballasts and floruenscents from all the lights and put in led in the basement and kichetchen, laundry areas. Probably will not add to much but everything will help.
Help with 128 batteries each one is 280ah, and want to configure for 48v system.
- Thread starter kromc5
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yabert
Solar Enthusiast
Yes, but with multiple packs, you have to consider the not negligible fact that you will have to balance the batteries before put them back parallel (all batteries at similar voltage, if no there will have big current flow).So you need to cut all charge/discharge twice, it's rather inconvenient. If you have multiple packs you can repair the faulty one while continuing to use the remaining ones
Also, this imply more contactors (or at least kill switchs), more lugs, crimps, wires... so more chance of trouble.
Flexibility have a cost and it's often at the cost of reliability.
I'm a big fan of keep it simple stupid solutions with no extra components, but I understand some people can prefer flexibility... but never from 8 battery+8 bms.
If I have to do a single large (100 kWh and +) battery like that with only 16 large cells (2240Ah) I think it's would not be a crazy idea to have two identical BMS with the master driving the show and the second bms simply waiting to replace the master in case of fail.
true, but you can just wait the right moment to add the repaired pack back. And you have the same problem at the cell level with one big pack anyway.
Actually if each independent pack has the same complexity as the one pack solution (let's say cells + BMS + fuse + disconnect for example) the end result will be more reliable, even if the total number of parts is higher.
Yes, 8 is a bit too much, that's why I was suggesting 4
Why not, it would work, but then you'd better having 2 separate packs instead of one at this point
yabert
Solar Enthusiast
Still it's easier to build, manage and monitor fewer components, contacts and crimps.
To me, in the specific case of 128 cells to build a 48V battery or batteries, my choice is one 16S 8P battery. I can understand to use two 16S 4P batteries, but more batteries, I don't.
Well, the important here is we had explain some reasons to choose how to connect large group of cells with some advantage and disadvantage.
Now kromc5, or others reader, can choose their preferred battery configuration based on those reasons.
Timers on corridors lights, on tv set and all those things, forcing them to get up and "add" some more time to this device that will finally shutdown automatically..? Well, first analysing where the energy is going then actions should be easier.
This is a kind of work that can be hard on nerve, and very exhausting...but I suppose also very rewarding.
Nice job.
Perhaps I'm wrong, but I would say that as soon as your repaired pack is topbalanced, you could put it in parallel, just program the bms for a low discharge rate like 10A.. and the pack should go down to those others pack.
curiouscarbon
Science Penguin
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1 cell fail expected -> 2 packs maybe?
2 cell fail expected -> 3 packs maybe?
my personal preference is for per cell voltage monitor and balance lead, but this result in more BMS/complexity at your large scale.
thank you for trying to address the electricity needs, i am sure your efforts will result in a victory
2 cell fail expected -> 3 packs maybe?
my personal preference is for per cell voltage monitor and balance lead, but this result in more BMS/complexity at your large scale.
thank you for trying to address the electricity needs, i am sure your efforts will result in a victory
Ohms_Cousin
New Member
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So is this the correct answer because it seems to be going back and forth. I would have thought it is the way you state it here...each cell supplying SOME of the load to make the total load up from the pack as a whole.
But others here keep saying ....NO.....each cell will supply 100 amps. So its hard for a new comer to grasp. Which point of view to take as correct ?
Each cell share the total power to be provided. Power is the result of voltage multiplied by Current. In série, current is constant and voltage is spread over all cells, in parallel, voltage is constant and current is spread between all cells.
So the total power is always shared between all cells. It is the type of connection which determine how it is calculated.
Not to be rude, but this is the very minimum you should master before dealing with such kind of battery. Understanding basics such as Power and Ohm law is mandatory if you want to build your own pack.
nickskethisnikske
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The problem with paralleled cells is that if one cel go short circuit all cells in that parallel group are dead or are damaged.
It's much easier to detect a faulty cel when they are not in parallel.
These are cells that still need to prove their selves on long term. I even heard stories about Winston's going short after 2-3years....so be careful.
It's much easier to detect a faulty cel when they are not in parallel.
These are cells that still need to prove their selves on long term. I even heard stories about Winston's going short after 2-3years....so be careful.
Can you share where you saw that?
yabert
Solar Enthusiast
Well, it's not exactly true. If a cell in a parallel group go wrong you can also simply have less capacity.
LFP cells are really tough.
Many years ago, after months of travel, I came back home to find a 12 kWh LFP car battery with almost all cells at 0.1V or 0.0V (48S 8P battery). The BMS used the cells energy to warn nobody than the cells are too low and need to be charge.
I dismantled this battery and after few days, many cells came back at around 2V or 3V and some other were simply at 0V. I charge and test capacity of the cells at 2-3V to remark that they had a regular capacity. So I used it to build bike battery, 12v camping car battery, etc and they still work well today.
So imagine if you detect a faulty cell way before it drop to 0.1V like it will be the case with a solar battery.
LFP chemistry is really tough and safe.
Exact. It's how you can easily find a faulty cell in a parallel group. You disconnect the cells in the group.
Ampster
Renewable Energy Hobbyist
I have a vague memory of a similar story with a Smart Car conversion on another forum. Was that you?
yabert
Solar Enthusiast
hehe! Yeap.
To add to my last message, people need to know than all electric car manufacturer design and build battery with cells in parallel.
GM, Tesla, Nissan, Kia, Ford, BMW, all build battery with parallel cells group from 2P, 3P and up to 74P.
Some can arg than it could be different for a solar battery and it's why I wrote it could be a good idea to build 2 battery.
Simple. You identify the faulty 2240Ah cell, after you identify and remove the single 280Ah faulty cells and continue to operate your 48v 1960Ah battery for the time you shout your cell supplier to had sold you crappy cell
After you add a new 280Ah cell and you will be able to operate your 48v 2240Ah battery.
In my case, I have more confident in cells than in electronic BMS. So, to me, less fairly reliable BMS and more ultra reliable busbar is the way to go.
The downside of a single battery is you have to stop your system to play with. If this is really problematic, build two 1120Ah batterie could be a good option.
Ampster
Renewable Energy Hobbyist
I remember that project. After selling my VW conversion I actually leased a couple of Smart EVs. They were great for the small beach town I lived in at that time. I never quite got those kind of wheelies. LOL
Slap a Hayabusa engine in that smart car and you're going to need a lot of tires.
ArthurEld
Solar Wizard
They roll great when you flip them. And keep rolling.
One of those smart cars would fit real nice in my toy hauler trailer. I'm not sure I could stand to be seen in one though.
I actually got to speak with Maxine from Batrium they were very nice and helpful, unfortunately my cell service was awful due to high winds. She suggested building two packs with 64 cells which greatly reduced the cost of the m8's. Also there is a 16s2p which is 32 cells where you need 16 m8's. I would not mind two large packs but I cannot find a diagram for anything over 16s2p. If anyone has diagram for 64 cell version I would be interested to see that one. I like the idea of at least two packs of cells just in case and it greatly reduces costs and m8's.
yabert
Solar Enthusiast
You mean M8 cell monitor right? Please don't spend money for fairly reliable electronic stuff where you don't need it.
If you build two 16S 4P batteries you will simply need two BMS. You have to consider 4 cells in parallel like 1 cell. When you will realize this your life will be simpler.
I suggest you to use a simple 16S bms with a large contactor (gigavac or similar). Zeva sell nice and simple BMS or find other similar unit.
I was considering using the batrium watchmon 4 with m8 cell monitors, one watchmon can handle all 4 or 2 banks.
yabert
Solar Enthusiast
Look like a good choice. A bit high price and too complex to me, but seem like it have all the bling bling you can expect from a modern BMS.
I hope you will find someone with Batrium knowledge.
coolwaterxii
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