Lithium battery BMS Question with Flexmax80

[Murby]

OK you still have a lot to learn and I would discourage you from using lithium as they are for advanced users only. Not to mention FLA will last a lot longer and tough as nails. As to your question you cannot disconnect the batteries from the controller because the controller gets all its power from the batteries. You can damage the controller disconnecting the batteries with the panels connected. You have to disconnect the panels, not batteries.

My problem is that I need the pack to be capable of doing nothing for long periods of time without requiring exercise or maintenance. I also want a high cycle count and lithium provides both.. Additionally, the way I'm going about it, its also only about 15% to 20% of the cost of the FLA batteries that would be needed to match the same performance.

In fact, about the only drawback to the Lithium batteries that I can see is that they are known to catch on fire.. and that can be solved easily enough by using an insulated steel container outdoors. Heck, the FLA batteries and all the fumes require nearly the same thing.

Like I said you have a lot to learn. Unless you have a bad cell, all cells charge equally and discharge equally. If they are Balanced from the start, they stay in Balance. You just said the BMS uses Vampire Boards, aka Bleeders. What you do not understand is how a Vampirte Board works. It only turns on when the first cell reaches 4.2 volts, and when it turns on only bypasses 0.9 amps. Problem is you may still be charging at say 50 amps. So when the first Vampire board turns on and bleeds 1 amp bypass leaves 49 amps flowing through your fully charged battery. Oops! Your BMS just destroyed the cell.

Actually, the REC BMS can be programmed to pretty much do whatever I want it to so far as voltages are concerned. Its a lot like the FlexMax controller in that it has settings for almost every parameter and a PC interface to see how each cell is doing.

The way I envision this working is that the PV array will charge the batteries through the Flexmax.. if the BMS detects a problem, it can open the circuit between the charge controller and the PV array while it works to bleed off the rogue cell imbalance.. Of course, this is only in a worst case scenario, as you say, once balanced, they should stay balanced.

Heck, with a little McGuyvering, I should even be able to set up a double throw relay system so the PV power is sent to do something else and doesn't get wasted.. maybe heat some water or something or even charge a back up lithium pack.

Now stop and think. if you Balanced the cells properly initially. and you only charge to 56 volts (4.0 vpc) Your BMS never does anything because no cell ever reaches 4.2 volts now does it?

When everything is operating as it should, then yes.. but we don't design things like this for times when they operate as they should.. If that was the case, we'd never need fuses or breakers.. We design for worst case scenario, and in this instance, that would involve a rogue lithium cell that has, for some reason, lost its capacity and is charging to its max voltage faster than the other cells. In such a case, we need to be able to either slow down the charger or cut it off all together.

The real question is how do you intend to do the Initial Bulk Balance? You cannot do that with a BMS as it is not capable of balancing a battery. Do you have the equipment and knowledge to do the initial balance?

I would think that a BMS would absolutely be capable of balancing the cells if the charge rate was low enough for it to keep up.. so to that end, I could either set the max amps in the FlexMax to a very low rate, or simply use fewer PV panels until all cells are balanced.

I don't think its an issue however as the cells I'm getting are used and already well balanced. They should still have greater than 90% of their life left in them.

Think of this no commercial EV manufacture allows a customer to ever fully charge the battery. I build racing golf carts and help a lot of people build DIY EV conversions. Very few would ever consider using a BMS because the BMS is the number 1 cause of failures. But there is a catch. We know what we are doing.

So until you figure out how to do the initial Balance and have the equipment to do it, you have no biz working with Lithium Batteries.

I was under the impression that every electric car on the road used a BMS on their batteries.

Hey man, I have no biz working on a lot of things.... story of my life. Its always seems to be the first one that requires the most work...

[jflorey2]

My problem is that I need the pack to be capable of doing nothing for long periods of time without requiring exercise or maintenance. I also want a high cycle count and lithium provides both.. Additionally, the way I'm going about it, its also only about 15% to 20% of the cost of the FLA batteries that would be needed to match the same performance. In fact, about the only drawback to the Lithium batteries that I can see is that they are known to catch on fire.. and that can be solved easily enough by using an insulated steel container outdoors. Heck, the FLA batteries and all the fumes require nearly the same thing.

A few issues here:

- The destructive power of fumes vs the destructive power of LiCo batteries are quite different. (i.e. one means you need to buy new jeans; the other means you need to buy a new house.)

- If you want long cycle life you are looking at LiFePO4 which are not as cheap as LiCo (or one of the other standard 3.6V formulations.)

- If you want long battery life overall you do NOT want to float them at high voltages (or even moderate charge voltages) for long. If it's a requirement that your batteries remain charged and then do nothing for long periods of time, a lead acid chemistry is going to be much better for you than a LiCo. Floating is very good for lead acid.

Heck, with a little McGuyvering, I should even be able to set up a double throw relay system so the PV power is sent to do something else and doesn't get wasted.. maybe heat some water or something or even charge a back up lithium pack.

MacGuyvering and lithium ion really don't mix.

The real question is how do you intend to do the Initial Bulk Balance? You cannot do that with a BMS as it is not capable of balancing a battery. Do you have the equipment and knowledge to do the initial balance?

I would think that a BMS would absolutely be capable of balancing the cells if the charge rate was low enough for it to keep up.. so to that end, I could either set the max amps in the FlexMax to a very low rate, or simply use fewer PV panels until all cells are balanced.

That's not a bulk balance.

I don't think its an issue however as the cells I'm getting are used and already well balanced. They should still have greater than 90% of their life left in them.

Putting the terms "used" and "well balanced" together is a huge red flag. Used cells in large lots, by definition, will not balance well together; they will come from smaller lots that have seen very different working environments. In fact, most such systems rely on using large quantities of mixed cells so the dramatic differences between them are averaged out.

Hey man, I have no biz working on a lot of things.... story of my life. Its always seems to be the first one that requires the most work...

Exactly. So perhaps it might be a good idea to make that "first one" safer and cheaper until you learn a little more.

[Murby]

A few issues here:

- The destructive power of fumes vs the destructive power of LiCo batteries are quite different. (i.e. one means you need to buy new jeans; the other means you need to buy a new house.)

LOL.. ya, I've seen the testing done.. its pretty awesome.

- If you want long cycle life you are looking at LiFePO4 which are not as cheap as LiCo (or one of the other standard 3.6V formulations.)

- If you want long battery life overall you do NOT want to float them at high voltages (or even moderate charge voltages) for long. If it's a requirement that your batteries remain charged and then do nothing for long periods of time, a lead acid chemistry is going to be much better for you than a LiCo. Floating is very good for lead acid.

I plan to park the batteries at around 1/2 charge as I do not need them to be full and ready to go. I am aware that lithium batteries do not store well when fully charged but are perfectly happy when left at something like 30% to 50% SOC.

MacGuyvering and lithium ion really don't mix.

Seems that a lot of folks would disagree as the internet is filled with people playing with these things.

Putting the terms "used" and "well balanced" together is a huge red flag. Used cells in large lots, by definition, will not balance well together; they will come from smaller lots that have seen very different working environments. In fact, most such systems rely on using large quantities of mixed cells so the dramatic differences between them are averaged out.

Exactly. So perhaps it might be a good idea to make that "first one" safer and cheaper until you learn a little more.

The battery I'm buying is one big pack with a bunch of individual cells. They're all one big happy family.

Thanks for for taking the time to reply, the more help the better!

[jflorey2]

I plan to park the batteries at around 1/2 charge as I do not need them to be full and ready to go. I am aware that lithium batteries do not store well when fully charged but are perfectly happy when left at something like 30% to 50% SOC.

Yes. Which means for backup applications you are going to have to buy 2x the battery you need. Again, if you are going to store them for a long time, lead acids are the way to go - cheaper and better suited to that task.

For most designs you start with the application - backup, off grid or peak shaving. Then you figure out loads, days of autonomy, other types of backups and temperature ranges. Then you figure out what energy sources you have available (i.e. hours of sunlight, average wind.) THEN you design the system, choose components or battery types.

You sound like you are going about this backwards. You've decided you want lithium ion and are trying to come up with specs to support that decision. Why not start with the basics?

Seems that a lot of folks would disagree as the internet is filled with people playing with these things.

The internet is filled with people drag racing in the snow and drinking a lot to impress women, too. That doesn't mean any of those things are a good idea.

In general, "there's a video of it on the Internet" is the worst possible rationalization for something being safe.

The battery I'm buying is one big pack with a bunch of individual cells. They're all one big happy family.

Sounds like someone came up with a great line to sell you used cells.

[Sunking]

My problem is that I need the pack to be capable of doing nothing for long periods of time without requiring exercise or maintenance. I also want a high cycle count and lithium provides both.. Additionally, the way I'm going about it, its also only about 15% to 20% of the cost of the FLA batteries that would be needed to match the same performance.

Wrong on all accounts As for size it takes a 65 AH lithium battery to equal a 100 AH Pb battery. Lithium operates from 10 to 90% SOC (50 Ah usable), FLA operates at 50 to 100% SOC.

As for cycle life, no lithium last longer than a good FLA. As for cost you are completely fooling yourself, a LiFeP04 is th eonly type you want to use and will cost you 400% more than fo reach usable AH and not last as long. Quit lieing to yourself or you wil make a decision based on lies and hype.

In fact, about the only drawback to the Lithium batteries that I can see is that they are known to catch on fire.. and that can be solved easily enough by using an insulated steel container outdoors. Heck, the FLA batteries and all the fumes require nearly the same thing.

You cannot put out a lithium fire.

I would think that a BMS would absolutely be capable of balancing the cells if the charge rate was low enough for it to keep up.. so to that end, I could either set the max amps in the FlexMax to a very low rate, or simply use fewer PV panels until all cells are balanced.

Quit making things up, you have no clue what you are talking about.

Sorry I cannot help you, your mind is already made up to fail.

[Murby]

Wrong on all accounts As for size it takes a 65 AH lithium battery to equal a 100 AH Pb battery. Lithium operates from 10 to 90% SOC (50 Ah usable), FLA operates at 50 to 100% SOC.

As for cycle life, no lithium last longer than a good FLA. As for cost you are completely fooling yourself, a LiFeP04 is th eonly type you want to use and will cost you 400% more than fo reach usable AH and not last as long. Quit lieing to yourself or you wil make a decision based on lies and hype.

I'm finding good salvaged Nissan Leaf batteries, as well as a few other brands, for around $2500 and they come from vehicles with 20k miles or so on them. The Nissan Leaf is just short of 24kw in capacity which gives me a conservative (being gentle with it), 18kw to 20kw of available power.

How much money would it cost to get that much power from a Rolls or other FLA battery with a similar life expectancy?

I'm not purchasing crappy Chinese batteries and then trying to compare them to the most expensive Rolls FLA battery.. I'm comparing capacity, cost, longevity, etc.

If you can show me where I can get the same thing a Nissan Leaf battery provides, at the same cost, in an FLA, I'm all ears.

You cannot put out a lithium fire.

Who cares? That's what outdoor steel boxes are made for.. like a "Job Box"

Quit making things up, you have no clue what you are talking about.
Sorry I cannot help you, your mind is already made up to fail.

I think I see what's going on now.. You use these salvaged lithium EV batteries in your go-cart toys you build, and the more people who purchase them from salvage yards, the harder it is for you to find them.. So to that end, you just tell everyone FLA is the way to go because its better than Lithium. That was you who said you use them right?

Interestingly, you're the ONLY one I've seen who's saying this, everyone else usually proclaims they'd love to have Lithium if it wasn't so expensive.

And the only thing I've failed at in the past 50 years is keeping my bad cholesterol down.. my doctor is not happy.

[Sunking]

I think I see what's going on now.. You use these salvaged lithium EV batteries in your go-cart toys you build, and the more people who purchase them from salvage yards, the harder it is for you to find them.. So to that end, you just tell everyone FLA is the way to go because its better than Lithium. That was you who said you use them right?

Yes I do use them on my third set in 6 years. Count them 1, 2 and 3 sets in 6 years. You can justify the cost of Lithium in an EV because it is impossible to get any range from FLA due to weight and volume. If weight were not the issue, no EV manufacture would use them and could save the customer a ton of cash. . Weight and volume are not an issue with RE storage. Long term cost effectiveness are the drivers for RE something you have dismissed. I am not the only one telling you do not have a clue. Make that 3 engineers with over 100 years experience combined to your 1 hour reading and no experience.

[Murby]

Yes I do use them on my third set in 6 years. Count them 1, 2 and 3 sets in 6 years. You can justify the cost of Lithium in an EV because it is impossible to get any range from FLA due to weight and volume. If weight were not the issue, no EV manufacture would use them and could save the customer a ton of cash. . Weight and volume are not an issue with RE storage. Long term cost effectiveness are the drivers for RE something you have dismissed. I am not the only one telling you do not have a clue. Make that 3 engineers with over 100 years experience combined to your 1 hour reading and no experience.

The problem I have with FLA is that even if you don't use them, they are on a self destruct timer. Here are my requirements:

I currently have a solar array big enough to handle all my power needs (and then some) so that's not a problem. We waste electricity around here like most people waste water. I can't even begin to describe how much I love that PV array.

I don't care if the batteries are fully charged when I need them, the emergency is not that urgent, just so long as they work when the panels can charge them.

I need about 20 kW of usable power when I do use them. It would be really nice to have more, but I can settle on 20 kW.

The batteries will not be put in use until they are needed, at which time, they will be needed every day.

I need the longest storage time possible. I had called Rolls about this and their technician said that even if I bought dry batteries, they would degrade over long storage times.

I talked to a guy who builds electric race boats here in Michigan, and he said he has Nissan Leaf batteries from 2012 that have been sitting on a shelf and they still have full capacity.. He said he's never charged them or touched them until he wanted to sell the extra packs. I made it clear to him from the beginning that I wasn't interested in purchasing his 4 cell packs and that I needed an entire battery.
Nissan themselves warrantied those batteries for 10 years under normal use, and I think its fair to say that normal use for a car is far more aggressive than for solar storage.. maybe not on a cloudy or snow day, but when the sun is shining, the batteries will see very little discharge.

As I've stated in other posts, I am a prepper. Its why I installed my original grid tied solar system, its why I have another 6000 watts of the same panels sitting in a Faraday cage along with a Radian 8048, Flexmax charger, Mate3, and various other hardware that will allow me to reconfigure my entire array to off grid use.

I need something I can put into storage and forget about.. Not something I have to perform maintenance on.

My original plan was to purchase some dry FLA batteries and store them in Mylar bags with oxygen absorbers to prevent any degradation.. Actually, just storing the batteries was the original plan, the whole mylar + oxygen absorber thing was an attempt to solve the degradation issue. Rolls said it wouldn't work.. although I'll admit that I still don't quite understand why, (No oxygen = no oxidation) I'm taking the word of the guy(s) at Rolls.. and yes, I said guys (plural) because I called twice over a two month period and got two different techs who told me the same exact thing..

Any chemists here want to take a shot at explaining how a dry battery, stored in an oxygen depleted environment, can degrade??? Could it be that there's no such thing as a true dry battery because they are all tested at the factory?

Then there's the cost issue you mentioned. Tell me how I can achieve my requirements with an FLA battery for near the same cost as good used Nissan Leaf (or other car) battery with low mileage.. And I should note, my cost analysis includes the extra cost of purchasing a $600 to $700 BMS system for the lithium pack.

Hey man, I'm not here to be right or wrong and I couldn't care less if you prove me wrong. I'm here to achieve a goal and I don't care how I achieve it. I even looked into purchasing a Flow Battery but the technology isn't available yet.

[Sunking]

The problem I have with FLA is that even if you don't use them, they are on a self destruct timer.

So are lithium batteries. I could care less what you do. You have made up your mind based on fantasy. I wil not help you anymore, your head is to thick to absorb facts. At 20 Kwh per day usage is insane off grid and will cost you 20 times more than buying from POCO with Lithium and 5 times more with Pb. Going off-grid is nucking futs regardless of what battery type you use if grid is available. Between the two poor choices, you choose the worse and most expensive of the two.

[Murby]

So are lithium batteries. I could care less what you do. You have made up your mind based on fantasy. I wil not help you anymore, your head is to thick to absorb facts.

"To absorb facts?" LOL.. you're killing me! That was funny as hell...

At 20 Kwh per day usage is insane off grid and will cost you 20 times more than buying from POCO with Lithium and 5 times more with Pb. Going off-grid is nucking futs regardless of what battery type you use if grid is available. Between the two poor choices, you choose the worse and most expensive of the two.

You obviously missed the "put in storage" and "I'm a prepper" part eh? That's a bit worrisome coming from someone who claims to be an engineer.

Ok.. Don't help me anymore.. You're not even capable of reading a requirements statements so I'm doubting you're going to be much help anyhow.. Plus a serious conflict of interest.

Have a great day, I wish you well with your projects.

[Mike90250]

Li batteries have the same shelf life problems as lead acid, with the added feature of being able to light themselves on fire.

"Dry charge" lead batteries slowly develop lead dioxide on the plates, ruining them. When you add acid, they start degrading. When you use them, they degrade faster.
The warranty label will tell you how long to expect them to last. "Marine & golf cart batteries", 2-3 years. Premium automotive batteries, 5 years (in a car), Solar deep cycle batteries 5-10 years. Premium Solar deep cycle batteries 8-20 years (look at the HUP brand of batteries) You will have paperwork to do monthly to keep the warranty in effect.

Now look at Li batteries and their warranty. I've not seen a warranty longer then 5 years. Most are 1-2 years. Not the claimed life time of the battery, the amount of time the mfg warrantys the battery for. Fine one longer than 2 years, and start reading the fine print.

The warrantys are indicative of the chemistry and construction limits of the battery. Sales droids and dreamers always talk about battery "Lifetime" because it means nothing.

You also seem to be conflating self-discharge (quite low in a Li battery) with battery life. 2 years on a shelf, and a lead acid battery has lost it's charge completely and is ready for recycle. Li batteries would only loose a couple % of their charge and only their calendar life is affected. So you could take a preppers gamble and stock up on used (abused?) car batteries with no warranty whatsoever and do completely manual balance, or try to have a BMS designed, or look into a HUP battery with a known and respected 20ish year warranty, that would need monthly top off charge
http://www.hupsolar.com/ that is compatiable with 99% of larger charge controllers.

I'd suggest a forklift battery, but they have a rather higher self-discharge, and would need weekly top-off charges, which may be unfeasible in your case.

[jflorey2]

The problem I have with FLA is that even if you don't use them, they are on a self destruct timer.

So are lithiums.

I need the longest storage time possible. I had called Rolls about this and their technician said that even if I bought dry batteries, they would degrade over long storage times.

So do lithiums.

I talked to a guy who builds electric race boats here in Michigan, and he said he has Nissan Leaf batteries from 2012 that have been sitting on a shelf and they still have full capacity.

He is lying to you. 2011-2012 were disastrous years for the Leaf battery; they degraded at a much higher rate than expected.

Nissan themselves warrantied those batteries for 10 years under normal use

Yep. And they are still trying to get out of all the lawsuits as a result of that mistake.

As I've stated in other posts, I am a prepper. Its why I installed my original grid tied solar system, its why I have another 6000 watts of the same panels sitting in a Faraday cage along with a Radian 8048, Flexmax charger, Mate3, and various other hardware that will allow me to reconfigure my entire array to off grid use.

Then get an FLA battery pack and replace it regularly. Heck, don't even do it yourself - pay someone to come out and replace it every 10 years. You'll still be spending less money. And you want FLA _especially_ if you are a prepper - you want something that just plain works, not something you have to tweak and fix every few months.

Then there's the cost issue you mentioned. Tell me how I can achieve my requirements with an FLA battery for near the same cost as good used Nissan Leaf (or other car) battery with low mileage..

So you have two possible cases. An FLA battery that will work, and a Nissan Leaf system that won't. Which will be better for you when the world ends?

[Mike90250]

....
So you have two possible cases. An FLA battery that will work, and a Nissan Leaf system that won't. Which will be better for you when the world ends?

Be sure to include blackout curtains in your plan, or all the "moths" will be drawn to your night lights

[Murby]

Li batteries have the same shelf life problems as lead acid, with the added feature of being able to light themselves on fire.

"Dry charge" lead batteries slowly develop lead dioxide on the plates, ruining them.

Can you explain how Lead Dioxide (or any other degradation process) would form on a dry battery that is stored in an oxygen depleted environment? I would really prefer to store the FLA batteries over the lithium and thought that purchasing a dry battery and storing it in a Mylar bag with oxygen absorbers would solve the oxidation problem as it does with food.

Rolls said it wouldn't work but I want to know why. I've heard the Lead Dioxide answer before but how does Lead Dioxide form without oxygen? Where's a battery chemist when you need one?

When you add acid, they start degrading. When you use them, they degrade faster.
The warranty label will tell you how long to expect them to last. "Marine & golf cart batteries", 2-3 years. Premium automotive batteries, 5 years (in a car), Solar deep cycle batteries 5-10 years. Premium Solar deep cycle batteries 8-20 years (look at the HUP brand of batteries) You will have paperwork to do monthly to keep the warranty in effect.

Next time you recommend a HUP battery, tell the person to sit down before going to their website... Those are some expensive batteries.

You also seem to be conflating self-discharge (quite low in a Li battery) with battery life. 2 years on a shelf, and a lead acid battery has lost it's charge completely and is ready for recycle. Li batteries would only loose a couple % of their charge and only their calendar life is affected.

When you say "only their calendar life is affected", are you saying that putting them on the storage shelf with only a partial charge will basically put them in stasis? In other words, Lithium batteries don't wear out or go bad if properly stored and not used?

So you could take a preppers gamble and stock up on used (abused?) car batteries with no warranty whatsoever and do completely manual balance, or try to have a BMS designed, or look into a HUP battery with a known and respected 20ish year warranty, that would need monthly top off charge
http://www.hupsolar.com/ that is compatiable with 99% of larger charge controllers.

HUP Batteries only have a 10 year warranty.. 120 Months as stated on their website. (unless I missed something or their definition of a month is different than mine)
Nissan Leaf has a 96 Month warranty.
Simpliphi has a 10 year or 10,000 cycle warranty as well.

Of course, after a certain time, I think all the warranties are prorated...

Warranties to a prepper don't mean much as there would be no way to get them honored. That, and I doubt a used battery from an electric vehicle like a Leaf with under 10,000 miles is going to have any abuse.
For the amount of money I'd have to spend on HUP batteries, I could purchase four or five used Leaf Batteries.. or two brand new ones WITH a warranty.

Those HUP batteries look really nice but they are also really expensive.

I'd suggest a forklift battery, but they have a rather higher self-discharge, and would need weekly top-off charges, which may be unfeasible in your case.

That's actually been a consideration. Its too bad my old shop is so far away or I could just go pull a couple of 48 volt batteries off the fork trucks if something happened..


You guys keep telling me that Lithium batteries are not as good as the FLA.. and yet, everywhere else I'm reading says the opposite and that the only drawbacks to the Lithium are price and the fire hazard.
Something doesn't add up.

If Lithium isn't as good as FLA, whey are people buying them for Solar storage? Why would companies like Simpliphi even exist Heck, even Tesla's powerwall comes with a 10 year warranty on their Lithium battery system. And that's 14.4 kWh with a built in inverter and BMS. I tried purchasing one but they're not available.


I sure wish I could figure out the whole Lead Dioxide thing...

[Murby]

Be sure to include blackout curtains in your plan, or all the "moths" will be drawn to your night lights

I'm a prepper, not some crazy conspiracy theorist who thinks zombies will roam the land.. The stupid television shows really give "actual preppers" a bad image.. and then of course there's the nut bags on youtube who don't help either. Its almost like the old days where anyone with a solar panel or fuel efficient vehicle was considered a crazy tree hugger.