Do these batteries look appropriate? Great deal.

[Sunking]

Ignore Karrak, he is a fraud and pretender banned a few times for fake and dangerous advice. Get lost Karrak.

[karrak]

Cool... karrak, can you tell me briefly how a BMS sort of works in regards to maintaining the charge/discharge level for each individual cell? The device you linked has about 10 leads coming out of it. Are each of these designed to be hooked to one individual pack (ie. one pack of 48V, 20Ah or something), so can support only up to 10 packs? Or is it designed for individual cells, ie. 10 cells (and not packs of them)? All of the battery packs I'm looking at say they have a BMS, which I thought meant some complicated circuit hooked up to each individual cell, but haven't done much BMS research yet.

The BMS I linked to hooks up to the individual cells or groups of paralleled cells that are then linked in series. Each block of paralleled cells will look like an individual cell to the BMS. The BMS serves a number of functions

1. Most importantly, makes sure the individual cells or blocks of paralleled cells stay within the safe operating voltage and temperature range. It will do this by disconnecting the battery from the outside world if any of the cells go outside their safe operating range.
2. Try to balance the individual cells so they are all at the same voltage. The BMS I linked to only have a limited capability to do this and will not be able to balance a battery that is badly out of balance.
3. Provide information to the operator or other equipment on the status of the battery and allow configuration of the BMS.
4. Protect the BMS from overload by disconnecting the battery if the charge or discharge current is too high.

Simon
Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
BMS - Homemade Battery logger github.com/simat/BatteryMonitor/wiki
Latronics 4kW Inverter, homemade MPPT controller

[karrak]

Beware of the "BMS trap". A BMS system has limits, and many different possible features. Some work by bleeding high voltage cells down. Some work by disconnecting the charger when the pack reaches a preset max voltage(HVD) . Some provide Low Voltage Disconnect too (LVD) All require interaction with the Charge controller, and you cannot simply disconnect the controller from the battery, without damage to the controller. Sometimes it's desirable to disconnect the solar PV from the controller.

Frankly, for a neophyte, most LFP systems are too risky and complex, unless you spend months learning the lingo before purchasing a thing. Things like, do any of those 10 spaghetti leads need fuses for protection against shorts? Can the wire harness be laid out in a safe manner? Is the BMS well engineered to not be a problem in it's self ?

If Karrak gives incomplete or wrong information, as in his enthusiasm for Lithium, he'll get a couple days in the cooler.

KARRAK - you are on notice, foisting a Li battery onto a neophyte, without a completely compatible BMS, CC & Load control is DANGEROUS. Expecting a neophyte who does not know what questions to ask, is borderline criminal.

Mike, If you had bothered to look at the BMS that I linked to you would have seen that it will disconnect the battery under a fault condition, so it doesn't need to interact with the charge controller or the loads.

As for charge controllers blowing up if you disconnect the battery this might have been true twenty years ago or for badly designed charge controllers but would not be true for modern well built charge controllers.

As for neophytes, all power systems are dangerous. Just because someone is not knowledgeable on a particular subject does not mean they lack intelligence and cannot learn. IMO it is better to give the information with appropriate warnings and let them come to the conclusion as to whether they are capable or not rather than telling a person that they are incapable of doing something and having them head off to Youtube.


Simon
Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
BMS - Homemade Battery logger github.com/simat/BatteryMonitor/wiki
Latronics 4kW Inverter, homemade MPPT controller

[rw3iss]

Thanks karrak, helpful. I'm not dumb, self-taught senior programmer here. Understand where you're coming from, Mike! Get along, guys Hopefully the sentiment of caution is taken seriously and emphasised in future posts as is necessary. Obviously batteries are dangerous, partly why I'm here, and it's nice to see a caliber of respectable professionalism and care carried into this forum.

[Sunking]

, Mike! Get along, guys

No fricking way. Karrak is a Fraud and a Pretender and not welcomed here.

[Mike90250]

In today's NASA Tech Briefs, is a multi page article about BMS and their many design problems that have to be overcome.

https://www.techbriefs.com/component/content/article/tb/features/articles/28701

EVERYTHING that applies to cars and their battery BMS, applies to home installs, except weight considerations. Cars use a more active version of battery, than a home use [LFP] application, and aside from voltage setpoints, the best BMS systems are the same.

and for now, KARRAK is banned, unless another moderator or admin likes being able to use him as a bad example of how to simplify a very hazardous battery to a "just trust the BMS I linked to because it's a good one". I'm done with watching over him and trying to figure how someone can shortcut his la-de-da suggestions and end up on fire. The Big Automotive mfg's have not got it figured out yet, every time another EV burns up, we learn something and take and apply it. But flooded lead acid has decades of troubleshooting and failure mitigation and the common gear is all dialed in and works pretty good. Engineering a solution for each LFP install is still in it's infancy - otherwise the NASA article would never need to have been written (unless they are trying to distract us from the still failed SLS issue). As for the disconnecting the battery and munging up the charge controller, I've not seen one major brand that allows that to happen in writing, it might not light into a ball of plasma, but the next morning, or the next when your power goes off, I'm pretty sure you will have to trudge out to the battery shed and manually reboot everything. He didn't tell you about that little issue.

I'm not saying you cant use a LFP battery bank, but at this stage, you don't know the questions to ask and actions to complete, to make a safe install. Within 15 miles of me, are 2 flamed LFP household packs that were "professionally" installed and lasted about 4 months before starting a fire. Both have forklift batteries as replacements. I say be careful and design the system well, Karrak oversimplifys the issues. (not any more)

[SunEagle]

In today's NASA Tech Briefs, is a multi page article about BMS and their many design problems that have to be overcome.

https://www.techbriefs.com/component/content/article/tb/features/articles/28701

EVERYTHING that applies to cars and their battery BMS, applies to home installs, except weight considerations. Cars use a more active version of battery, than a home use [LFP] application, and aside from voltage setpoints, the best BMS systems are the same.

and for now, KARRAK is banned, unless another moderator or admin likes being able to use him as a bad example of how to simplify a very hazardous battery to a "just trust the BMS I linked to because it's a good one". I'm done with watching over him and trying to figure how someone can shortcut his la-de-da suggestions and end up on fire. The Big Automotive mfg's have not got it figured out yet, every time another EV burns up, we learn something and take and apply it. But flooded lead acid has decades of troubleshooting and failure mitigation and the common gear is all dialed in and works pretty good. Engineering a solution for each LFP install is still in it's infancy - otherwise the NASA article would never need to have been written (unless they are trying to distract us from the still failed SLS issue). As for the disconnecting the battery and munging up the charge controller, I've not seen one major brand that allows that to happen in writing, it might not light into a ball of plasma, but the next morning, or the next when your power goes off, I'm pretty sure you will have to trudge out to the battery shed and manually reboot everything. He didn't tell you about that little issue.

I'm not saying you cant use a LFP battery bank, but at this stage, you don't know the questions to ask and actions to complete, to make a safe install. Within 15 miles of me, are 2 flamed LFP household packs that were "professionally" installed and lasted about 4 months before starting a fire. Both have forklift batteries as replacements. I say be careful and design the system well, Karrak oversimplifys the issues. (not any more)

Do you think he will learn a lesson having a year vacation?

[rw3iss]

Alright then, thanks.
Erm, I'll do some more research myself, but am curious... would you guys recommend I stay away from the battery packs with a built-in BMS (ie. designed by someone else/Chinese), be it any kind of Li-Ion (LFP, LMO, NMC, etc)? Or would it make more sense to buy them with the BMS that is designed specifically for those packs?

[Sunking]

You best best is to just stay away from Lithium batteries. Auto manufactures and aerospace can do a few things you cannot. They have thousands of cells to choose from and match them up in capacity and internal resistance. Nasa Satellites do not use BMS systems as they takes up way to much weight and space. They perform a Middle Balance technique adopted by DIY EV makers. They take equal cells in capacity and resistance and Balance in the middle. All the cells charge up to the same level, and all cells discharge to the same level. The only BMS is to not allow them the pack to fully charger or every fully discharge where the batteries become dangerous.

Commercial EV use a similar technique of middle balance and do have cell level boards. Difference is they do not ever Top Balance any cells, When and if a cell becomes out of balance will send power to weaker cells. Like Nasa they never allow any battery to be fully charged or discharged. If they did that EV batteries would be dead in a year or two and more frequent fires.

What the Chi-Coms and Karrak does is treat LFP cells like Lead Acid batteries forcing every cell to full capacity. They do so with what is called Bleeder Boards aka Vampire Board. So with your 10 amp charger, when a cell reaches full charge it bypasses a few milli-amps up to an amp around a fully charged cell to charge a lower cell. Sounds good in theory but if you have a 10 amp charger, and the Bleeder Board only bypasses 1 amp means you still have 9 amps of over charge into full cell getting hot and risking thermal runaway, It is a very dangerous algorithm to mimic lead acid batteries to self equalize. Gets more dangerous on the Discharge side when a weak cell fails and goes into polarity reversal which is instant destruction of a cell and serious heating.

Lithium is just not ready for homes. PB is still less expensive, longer life, and much safer. PB batteries are still allowed to be shipped on planes. Lithium are not. Now Karrak got what he has asked for, a long vacation .

[Sunking]

Do you think he will learn a lesson having a year vacation?

Most certainly he will. and never come back. Just look out for him to surface with a different username. JohnP had many names.

[rw3iss]

Very informative, thank you Sunking. Chi-Coms... lol, man...
Battery technology is really intriguing and I hope to get more into it from here on out. Bleh, now I'm torn. Need to find a solution within a month or so. I will have to do some more research. I feel like there's a lot of new breakthroughs with both technologies lately (Li-Ion and FLA-types), from what I've been seeing, and probably will be worth a better look in a few years, but for now, not sure what makes more sense. I get your points with FLA, but the more than double energy density of Li-Ion is very attractive. Money is not a terrible issue here, but I don't plan to pay more than hopefully $4k for 10kwh. Are their any Li-Ion setups that you guys would recommend that are safe? LFP with a good BMS? Something else like NMC? Don't want to beat a dead horse, but also don't want to kill my Li-Ion dreams. There's gotta be something, one would think...

[nebster]

You probably should do some more reading and studying, including branching out to many forums -- and, yes, even YouTube -- so you get a broader cross-section of opinions and perspective. Note that the YT examples you'll find, particularly in mobile applications, are in many cases pushing the risk envelope quite harder than most would find prudent.

LFP with a reasonable BMS and modern, name-brand charging hardware is about as safe as you can get with lithium in the name somewhere. But it does require care and a good, solid understanding of the fundamentals. You pretty much either need to spend quite some time gaining mastery of the subject or commit to buying an engineered system, if safety is a high priority. Frankly, a good chunk of the exposure is just because you have a low-impedance, high density energy source sitting there, and not so much "because lithium."

I don't think you can achieve 10kWh today for $4k, unless your time is worth $0 and you don't buy any other supporting hardware (wires, fuses, controllers, BMSes, interconnects... they add up!), or unless you salvage cheap vehicle cells. The latter will likely not be LFP and will come with a whole host of additional risks that make them undesirable in many/most scenarios.

[rw3iss]

Alright nebster, thank you. Yeah I figured just 4k for the battery itself, maybe the BMS. I will gas up the research train!

[nebster]

You can definitely get 10kWh of brand new LFP for about $4k, modulo shipping. You'll be purchasing from Chinese manufacturers if you are buying prismatic, bare cells. (Most of the engineered LFP packs designed for mobile applications are using the same cells inside, too.)

I may have been lucky, but my order of roughly $14k of cells came in with two damaged cells (out of 112) and the rest measuring very tight and consistently with respect to each other. I did order extra, anticipating some losses.

You might look at one of the cheaper engineered ESS packs if you're in a stationary setting, at least as a point of comparison. LG Resu is pretty attractive. Not LFP, and also higher quality pouch cells, but fairly aggressive on pricing for an integrated design.

If this is just a low-discharge supplemental residential storage application, though, you could also just use lead acid and save a bunch of hassle and money.

[rw3iss]

K, will consider FLA. Essentially it is for an RV that I'll be travelling in a while. Only real power-hungry stuff I do is listen to music on a decent set of speakers! Might boil a tub of water with a 1kw heater now and then, so that will be my max power usage I think (1kw). Cooking, heat, all gas + wood. Eventually I think I will be stationary and will expand on the system... Do people mix FLA and Li-Ion? Suppose it could be useful to have both, as backups and such, but need totally independent systems I'm assuming. Might consider a more invested Li-Ion system when the technologies improve, perhaps.