LTO SCiB battery bank for off-grid

[fisherus]

Do you have a link, member name, or keywords that may help me find a thread on that particular build?

When you say break and rebuild, if I stay in a 12 cell configuration, I can leave the cells in their casing and I'd only need to cut the bars connecting each cell in series?

Hi,
I've been so busy I haven't had the time to get on here. It appears that you are using a 24V system so, because I have a 24V system in place while I am building my 48V system, I can advise you what I did to accommodate the batteries into this system. All you need to do is remove the buss bar connection between the two 12 cell connection in each unit. Then parallel the units together. I used a Square D circuit breaker box and double pole circuit breakers to connect the batteries together. This allows the use of 10ga.stranded copper wire from each battery to the breaker. Thus, 8 batteries, 8 breakers. From the box to my inverter I am using 2 gauge stranded copper wire with a 300 amp fuse between them. I set my nominal at 30V and minimal at 24V. You can play with your settings to find what works best for you but, I don't think you want to be over 30V. I am only using eight 100W Renogy panels for this system
My 48V system under construction I am using 18 360w panels wired in series of 9 panels each, using 10ga. TWNN stranded copper wire to my Sol-Ark 12k, which has 2 built-in chargers, with each string wired to each charger. I have a battery bank of 16 LTO batteries wired to a Square D circuit box using double pole, single switch circuit breakers. I am using 10ga copper stranded wire to connect each battery to its own breaker and 4-0ga stranded copper wire to the Sol-Ark 12k inverter connections. (Little overkill but I like to be safe). I am almost finished building my battery rack out of 1 1/4" square steel tubing. I have ordered Daly BMS's customized for my batteries but really don't know if they are worth the additional expense as LTO cells rarely fail or go outside the perimeters of balance. They are there for monitoring purposes more than balancing. If you have any questions pm me

 

[AmpLee]

Hi,
I've been so busy I haven't had the time to get on here. It appears that you are using a 24V system so, because I have a 24V system in place while I am building my 48V system, I can advise you what I did to accommodate the batteries into this system. All you need to do is remove the buss bar connection between the two 12 cell connection in each unit. Then parallel the units together. I used a Square D circuit breaker box and double pole circuit breakers to connect the batteries together. This allows the use of 10ga.stranded copper wire from each battery to the breaker. Thus, 8 batteries, 8 breakers. From the box to my inverter I am using 2 gauge stranded copper wire with a 300 amp fuse between them. I set my nominal at 30V and minimal at 24V. You can play with your settings to find what works best for you but, I don't think you want to be over 30V. I am only using eight 100W Renogy panels for this system
My 48V system under construction I am using 18 360w panels wired in series of 9 panels each, using 10ga. TWNN stranded copper wire to my Sol-Ark 12k, which has 2 built-in chargers, with each string wired to each charger. I have a battery bank of 16 LTO batteries wired to a Square D circuit box using double pole, single switch circuit breakers. I am using 10ga copper stranded wire to connect each battery to its own breaker and 4-0ga stranded copper wire to the Sol-Ark 12k inverter connections. (Little overkill but I like to be safe). I am almost finished building my battery rack out of 1 1/4" square steel tubing. I have ordered Daly BMS's customized for my batteries but really don't know if they are worth the additional expense as LTO cells rarely fail or go outside the perimeters of balance. They are there for monitoring purposes more than balancing. If you have any questions pm me

Nice! Sounds like we are doing a similar build and should share notes as we go. I might have run into you in the comment section on YouTube. Are you doing a 24s setup? If so are you not worried about your inverter not spanning the voltage of the batteries which would be 36-64.8v. I found the MagnaSine 4000w 48v inverter covers the entire range so I was considering getting 2-4 of them and running them parallel.

 

[fisherus]

Nice! Sounds like we are doing a similar build and should share notes as we go. I might have run into you in the comment section on YouTube. Are you doing a 24s setup? If so are you not worried about your inverter not spanning the voltage of the batteries which would be 36-64.8v. I found the MagnaSine 4000w 48v inverter covers the entire range so I was considering getting 2-4 of them and running them parallel.

I'm using a SolArk 12k set at 60V Nominal and 48V Minimal. I might lower my settings to a charge of 56V Nominal and 40V Minimal as demand for power is increased. My SolArk only charges to a 61V maximum so I scaled the batteries to it. Will see how it works for a month or so but the batteries I purchased all seem to handle and retain the 2.5V per cell with little bleeding of loss over a 30 day period. You don't have to span the voltage limits of the battery with an LTO battery. As long as the batteries are brought into balance below the maximum charge setting and above minimum setting of your charger, the charge will stay between those levels. This is the best part of using a lithium type battery because they are not locked in to the perimeters of a lead acid type battery with absolute fixed voltage limits.
By using the lower Nominal charge rate it places the batteries in their comfort zone as they don't like being fully charged. So, from all the information I have found from Toshiba regarding this battery their recommendation is for 2.3V Nominal for longest cycles. This battery was made for a Honda Fit, if you didn't know it.
You ought to look into the SolArk 12k as you can run them in series for your system. When you configure your wire needed and everything else using the Magna Sine compared to the SolArk 12k including the warranty, it will be more efficient and save you money. At least it did for me. You can run 2 strings of up to 10 panels using 10 ga wire to your charge control connector.
Your bank is huge and I don't know what you use so much power for but, that is a huge amount of watt hours. I'm running around 15K watt hours which exceeds my needs plus my 24V system includes wind generation and hydraulic on top of that. I can plug the 24V inverter into the SolArk generator port if I need additional power.

 

[AmpLee]

I'm using a SolArk 12k set at 60V Nominal and 48V Minimal. I might lower my settings to a charge of 56V Nominal and 40V Minimal as demand for power is increased. My SolArk only charges to a 61V maximum so I scaled the batteries to it. Will see how it works for a month or so but the batteries I purchased all seem to handle and retain the 2.5V per cell with little bleeding of loss over a 30 day period. You don't have to span the voltage limits of the battery with an LTO battery. As long as the batteries are brought into balance below the maximum charge setting and above minimum setting of your charger, the charge will stay between those levels. This is the best part of using a lithium type battery because they are not locked in to the perimeters of a lead acid type battery with absolute fixed voltage limits.
By using the lower Nominal charge rate it places the batteries in their comfort zone as they don't like being fully charged. So, from all the information I have found from Toshiba regarding this battery their recommendation is for 2.3V Nominal for longest cycles. This battery was made for a Honda Fit, if you didn't know it.
You ought to look into the SolArk 12k as you can run them in series for your system. When you configure your wire needed and everything else using the Magna Sine compared to the SolArk 12k including the warranty, it will be more efficient and save you money. At least it did for me. You can run 2 strings of up to 10 panels using 10 ga wire to your charge control connector.
Your bank is huge and I don't know what you use so much power for but, that is a huge amount of watt hours. I'm running around 15K watt hours which exceeds my needs plus my 24V system includes wind generation and hydraulic on top of that. I can plug the 24V inverter into the SolArk generator port if I need additional power.

Yeah, it's a big setup, but we use a whole lot of energy running jet pumps, Coolbot/mini-split walk-in cooler, lots of battery tools (string trimmer, mowers, etc.), electric instant hot water heater, and multiple buildings/workshops. I'm also considering getting a cybertruck (I know it looks ridiculous) so am planning on having more than enough electricity. We're always here working growing food and pre-covid ran a bed and breakfast so it makes sense to use as much of the sun's energy as possible and take as much as we can off the grid. Throughout the year we average 45kW per day, but I'm going to do a major energy audit as I install this system and tighten things up as much as possible.

I don't know if you're familiar but the honda insight forum has some really great look into these SCiB batteries as some of those folks have used them in conversions in their vehicles. You are absolutely right that the ideal voltage range is probably between 2.0-2.5v. I think that's about 90 percent of the batteries capacity if I remember correctly.

So, theoretically the Daly BMSes will keep the cells balanced so that when you set your SolArk to 48-60v range each cell will be 2.5v when the inverter cuts out at 60v? That does seem pretty ideal as far as extending the life of the batteries which already boast a lifespan that will likely outlast me. Pretty cool. Can you tell me more about your decision to go with the SolArk 12k? I haven't really dove into every aspect of the solar build I'm conceiving and know very little about inverters.

Lastly, what did you use to balance charge your cells when you first got them and did you come across any bad cells? I'm looking to buy a pl8 by cellpro which the guys over at the Honda Insight forum have worked with and set up profiles.

 

[fisherus]

The SolArk 12K is the most efficient system on the market and when you add up everything you will need to purchase to get close to what it does, you will find your costs will be significantly higher going with anything else for a system the size of yours. check it out at : www.solark.com
They have many videos on YouTube out going completely through everything. Make sure you check the 12K, not the 8K as the 12K is the only one you can run multiple units in series. The SolArk is a complete all-in-one unit which has dual 9K chargers built into it along with port for AC in (which on-grid you can use AC power to charge batteries or a generator on AC. It even has a built-in starting control for your generator if additional charge is needed for your battery bank or you need more power than panels are producing in inclement weather. The only problem I had was with the initial sales person who was educated into using the cobalt batteries they sale which use parameters of lead acid batteries. I finally requested to talk to one of their engineers and fortunately got the one that designed it.
I learned about these batteries through "Insight" which pointed me to Toshiba filing materials of which I was able to glean the practicality of using for a battery bank. Just wish I had waited a little longer as the price dropped dramatically from what I paid on Ebay. My current setting gets me a minimum of 960 Watt Hours per battery or .96K, just short of 1K for a total of 19.2K. Because of the extremely fast recharge rate of LTO batteries, if I run one well pump and fill a 2500ga tank as well as my 5hp compressor and 175 amp Mig welder during high time charge hours, my batteries are always full by days end. Pretty amazing.

 

[fisherus]

Yeah, it's a big setup, but we use a whole lot of energy running jet pumps, Coolbot/mini-split walk-in cooler, lots of battery tools (string trimmer, mowers, etc.), electric instant hot water heater, and multiple buildings/workshops. I'm also considering getting a cybertruck (I know it looks ridiculous) so am planning on having more than enough electricity. We're always here working growing food and pre-covid ran a bed and breakfast so it makes sense to use as much of the sun's energy as possible and take as much as we can off the grid. Throughout the year we average 45kW per day, but I'm going to do a major energy audit as I install this system and tighten things up as much as possible.

I don't know if you're familiar but the honda insight forum has some really great look into these SCiB batteries as some of those folks have used them in conversions in their vehicles. You are absolutely right that the ideal voltage range is probably between 2.0-2.5v. I think that's about 90 percent of the batteries capacity if I remember correctly.

So, theoretically the Daly BMSes will keep the cells balanced so that when you set your SolArk to 48-60v range each cell will be 2.5v when the inverter cuts out at 60v? That does seem pretty ideal as far as extending the life of the batteries which already boast a lifespan that will likely outlast me. Pretty cool. Can you tell me more about your decision to go with the SolArk 12k? I haven't really dove into every aspect of the solar build I'm conceiving and know very little about inverters.

Lastly, what did you use to balance charge your cells when you first got them and did you come across any bad cells? I'm looking to buy a pl8 by cellpro which the guys over at the Honda Insight forum have worked with and set up profiles.

I received a notification from the Insight forum and read your inquiry, giving you a reply before I realized the date you made it, so disregard it. I had Daly make my BMS's set at 2.5V 40amp 24s.
I used a couple of small DROK buck converters to balance my cells but there was only a few milliamps of variance between one or two on a few batteries even though they were from 3 different lots. I removed all of the factory BMS boards before doing this. I used the same screws to attach the BMS leads which made it simple, then routed the leads back through the nipples that originally contained the wires to the original board. I might place the Daly's. under one of the covers during final installation but, I am going to be hauling my system from my home in Southern Idaho to my farm in Northern Idaho, 473 miles. This will allow me to secure them in a box for transport.
You might want to use the same system I did to parallel your batteries together by using double pole single switch breakers in a Square D breaker box. They will accommodate 20 batteries each so 2 tied together on a common buss bar should do the trick. I also wired a 300amp fuse in my box. This makes for a very clean look. When I get my battery rack finished I can send you some pictures as well as information on where to find everything I used. I am thinking about purchasing another SolArk and if you find they will meet your needs, we might get together and see if we can get a discount on the price.
I know how intimidating this is as I was in your shoes about a year ago and I have never wanted to do anything with electricity or wiring diagrams. Terminology was a big challenge for me to learn but what you will know a year from now will be mind blowing. At least it has been for me as I reflect back on some of the questions I previously asked others.

 

[AmpLee]

I received a notification from the Insight forum and read your inquiry, giving you a reply before I realized the date you made it, so disregard it. I had Daly make my BMS's set at 2.5V 40amp 24s.
I used a couple of small DROK buck converters to balance my cells but there was only a few milliamps of variance between one or two on a few batteries even though they were from 3 different lots. I removed all of the factory BMS boards before doing this. I used the same screws to attach the BMS leads which made it simple, then routed the leads back through the nipples that originally contained the wires to the original board. I might place the Daly's. under one of the covers during final installation but, I am going to be hauling my system from my home in Southern Idaho to my farm in Northern Idaho, 473 miles. This will allow me to secure them in a box for transport.
You might want to use the same system I did to parallel your batteries together by using double pole single switch breakers in a Square D breaker box. They will accommodate 20 batteries each so 2 tied together on a common buss bar should do the trick. I also wired a 300amp fuse in my box. This makes for a very clean look. When I get my battery rack finished I can send you some pictures as well as information on where to find everything I used. I am thinking about purchasing another SolArk and if you find they will meet your needs, we might get together and see if we can get a discount on the price.
I know how intimidating this is as I was in your shoes about a year ago and I have never wanted to do anything with electricity or wiring diagrams. Terminology was a big challenge for me to learn but what you will know a year from now will be mind blowing. At least it has been for me as I reflect back on some of the questions I previously asked others.

Right on. Yeah, you sold me on the SolArk. For some reason I was under the impression that the inverter needed to cover the entire battery voltage, so thanks for helping me understand it better. I think you saved me a loooooot of headache since the SolArk seems to be as plug and play as it gets.

Yeah, I think I saw you comment on Ben's youtube video regarding the QO D Breaker box. Looks like I'll need two but I'm unsure how to connect to a common busbar (still so much to learn). I'm glad to hear that you were in the same position and now seem to have a good understanding of things.

 

[fisherus]

Right on. Yeah, you sold me on the SolArk. For some reason I was under the impression that the inverter needed to cover the entire battery voltage, so thanks for helping me understand it better. I think you saved me a loooooot of headache since the SolArk seems to be as plug and play as it gets.

Yeah, I think I saw you comment on Ben's youtube video regarding the QO D Breaker box. Looks like I'll need two but I'm unsure how to connect to a common busbar (still so much to learn). I'm glad to hear that you were in the same position and now seem to have a good understanding of things.

What I would do is watch some of "Dave Poz" videos as he is a friend of Ben. He is one of the best DIY YouTube experts I've found. If you watch his video regarding his "Tower of Power " it will be easier to get the idea on making a large bus bar from copper and a piece of nylon cutting board you can get at a dollar store. He uses copper pipe he scraped but I purchased a piece of 1/4" copper plate 2" x 6" that I used from Ebay (which is a little overkill. ) All you need on the Sol-Ark 12k is a cut-off switch on your exterior of your system to cut power from your panels. You will probably need two as I think that will give you all the power you can use and still keep your batteries in a healthy state of charge.
I am amazed that most people piss away money on controllers and inverters without looking into the Sol-Ark as you have realized, not only is it plug and play but cheaper overall to install. And with a warranty that is unheard of in solar equipment as most fail within the first 5-8 years.
I am in Idaho.

 

[AmpLee]

The one thing that worries me about the SolArk is that the Daly BMS won't top balance unless it reaches a certain volatage. If I'm reading my spec sheet correctly on my BMS, balance won't occur until the cells reach 2.7 volts which would mean that I'd need an inverter that could reach 64.8v. Am I thinking about this correctly?

 

[fisherus]

The one thing that worries me about the SolArk is that the Daly BMS won't top balance unless it reaches a certain volatage. If I'm reading my spec sheet correctly on my BMS, balance won't occur until the cells reach 2.7 volts which would mean that I'd need an inverter that could reach 64.8v. Am I thinking about this correctly?

You can have Daly make them to any setting you want for the same cost. I had mine made for 60V 2.5V 40A and they top and bottom balance. If you contact Daly and tell them you want 2.5V they can get them made in 3 days and ship.
Dongguan Daly Electroniccs Co.,Ltd
Wechat:+8616620740463
Tel :+8616620740463
E-mail:Ruby.zhang@dalyelec.com
Ruby Zhang is the contact person so email what I told you: LTO 24S 60V 2.5V Top Balance per cell along with your email address and cell phone number. They bill through PayPal only so you will have to set up a PayPal account if you don't have one.

 

[AmpLee]

You can have Daly make them to any setting you want for the same cost. I had mine made for 60V 2.5V 40A and they top and bottom balance. If you contact Daly and tell them you want 2.5V they can get them made in 3 days and ship.
Dongguan Daly Electroniccs Co.,Ltd
Wechat:+8616620740463
Tel :+8616620740463
E-mail:Ruby.zhang@dalyelec.com
Ruby Zhang is the contact person so email what I told you: LTO 24S 60V 2.5V Top Balance per cell along with your email address and cell phone number. They bill through PayPal only so you will have to set up a PayPal account if you don't have one.

Thanks. I already put in an order thinking that the voltage for the LTO would already be ideal (since it's based on the chemistry) but it looks like the top balance of 2.7 would not work with the SolArk, which I would prefer to use. Plus, I don't want have to charge the batteries to 2.7 just to balance. Looks like I just wasted money not doing enough research before I bought.

So your bms balance at both 2.5v and 1.9v? Is it necessary to have the bottom balance too, or is that just in case you want to alter the inverter to a different range (say 1.9 - 2.4)? What are your voltage cut-off parameters (if I ask for 2.5v balance, should the voltage cut-off exceed that to 2.7 since the inverter will cut out at 2.5 regardless)?

 

[fisherus]

I know what it's like to put the cart before the horse in solar expenditures for sure as I have a bunch of stuff I bought because I didn't research with due diligence.
Actually, LTO batteries only need to be top balanced by a BMS as they rarely get out of balance on the bottom if they are balanced on the top. The major problem you will have trying to get to the 64.8V maximum voltage is they won't hold the charge at that state of charge because they are used. They will hold between 2.5-2.6V, however, so regardless of what voltage maximum charge rate a solar charger can reach, you won't be able to keep them at that level. These are sold as 60V batteries even though they originally were 64.8V so you need to keep your charge rate at 60V Nominal and at least 40V minimal to achieve the maximum holding capacity of your batteries for many years of use. Trying to charge above the 60V rate will eventually destroy your charger because it will never top off the batteries and shut off in my opinion. These batteries will no longer work for their intended use because they won't hold the voltage they were designed for. But, they can now be used for solar purposes because they won't go below the 2.5V level until they are completely destroyed.
Your 2.7V won't work for these batteries regardless of what charger you use because they won't hold a full charge anymore above 2.5V. Hope this helps make a little more sense to you?

 

[AmpLee]

I know what it's like to put the cart before the horse in solar expenditures for sure as I have a bunch of stuff I bought because I didn't research with due diligence.
Actually, LTO batteries only need to be top balanced by a BMS as they rarely get out of balance on the bottom if they are balanced on the top. The major problem you will have trying to get to the 64.8V maximum voltage is they won't hold the charge at that state of charge because they are used. They will hold between 2.5-2.6V, however, so regardless of what voltage maximum charge rate a solar charger can reach, you won't be able to keep them at that level. These are sold as 60V batteries even though they originally were 64.8V so you need to keep your charge rate at 60V Nominal and at least 40V minimal to achieve the maximum holding capacity of your batteries for many years of use. Trying to charge above the 60V rate will eventually destroy your charger because it will never top off the batteries and shut off in my opinion. These batteries will no longer work for their intended use because they won't hold the voltage they were designed for. But, they can now be used for solar purposes because they won't go below the 2.5V level until they are completely destroyed.
Your 2.7V won't work for these batteries regardless of what charger you use because they won't hold a full charge anymore above 2.5V. Hope this helps make a little more sense to you?

So on the spec sheet of the BMSs that I ordered the over charge is 2.85v and over discharge is at 1.7v. Did you specify with Daly the parameters you'd like for these charge and discharge cut-offs so that they'd match the range you're shooting for (say 48v-60v (2.0v-2.5v per cell)), or is it better to have the over charge and over discharge to be outside of those ranges? I'm not sure if my question makes sense.

The other thing I'm concerned about is the balance current which is set at 20mA. Is this sufficient for your setup, or did you specify a number that makes more sense?

 

[fisherus]

I had Daly set my BMS to 2.7V after I found out that they are to protect overcharging the batteries it would be fine to set them at that limit for a top cut off. In your case, at a 2.85V top, because it is 0.15V over, it seems that you won't have overcharging protection on your batteries. I'm more concerned about top balance (including overcharging) than bottom because the settings in my Sol-Ark 12k allow for disconnect of battery bank from the inverter at a minimum setting and as I stated previously, most tests I have seen on LTO batteries show little, if any, value to bottom balance if you bottom balance manually before installing (I took each battery down to 1.5V per cell and charged them up to 2.5V before I paralleled all of them.
If you are using two Sol-Ark 12k then you can set each group of 20 to each one separately without a bus bar connection and wire your AC circuits to proper demand accordingly.
Initially I purchased a couple of the BMS'S in two different configurations before deciding to order the rest of them. I was advised to do this and I wish I could have caught you earlier about it. If I were you find out if Daly can reconfigure the ones you have. You'll only be out the freight charge.
I found out that they misconfigured one I ordered for the 2.5V top to a 2.5V bottom which they are giving me credit for. If you want to wait until I get the 15 I ordered, I will send you a copy of the configuration report when I get it.

 

[Craig]

I had Daly set my BMS to 2.7V after I found out that they are to protect overcharging the batteries it would be fine to set them at that limit for a top cut off. In your case, at a 2.85V top, because it is 0.15V over, it seems that you won't have overcharging protection on your batteries. I'm more concerned about top balance (including overcharging) than bottom because the settings in my Sol-Ark 12k allow for disconnect of battery bank from the inverter at a minimum setting and as I stated previously, most tests I have seen on LTO batteries show little, if any, value to bottom balance if you bottom balance manually before installing (I took each battery down to 1.5V per cell and charged them up to 2.5V before I paralleled all of them.
If you are using two Sol-Ark 12k then you can set each group of 20 to each one separately without a bus bar connection and wire your AC circuits to proper demand accordingly.
Initially I purchased a couple of the BMS'S in two different configurations before deciding to order the rest of them. I was advised to do this and I wish I could have caught you earlier about it. If I were you find out if Daly can reconfigure the ones you have. You'll only be out the freight charge.
I found out that they misconfigured one I ordered for the 2.5V top to a 2.5V bottom which they are giving me credit for. If you want to wait until I get the 15 I ordered, I will send you a copy of the configuration report when I get it.

So on the spec sheet of the BMSs that I ordered the over charge is 2.85v and over discharge is at 1.7v. Did you specify with Daly the parameters you'd like for these charge and discharge cut-offs so that they'd match the range you're shooting for (say 48v-60v (2.0v-2.5v per cell)), or is it better to have the over charge and over discharge to be outside of those ranges? I'm not sure if my question makes sense.

The other thing I'm concerned about is the balance current which is set at 20mA. Is this sufficient for your setup, or did you specify a number that makes more sense?

View attachment 15527

I would not be too concerned about the 2.85 cut off. They will balance sooner or later if they are not balanced when you set them up. The number 1 thing to worry about with LTO is not overcharging any 1 cell. If the BMS cuts off at 2.85 that solves that problem. What will happen is the BMS will stop charging and as Fisherus said they will drop rapidly and start self balancing the lower ones will not drop in voltage as much if at all.. There is so little energy above 2.4 volts less than 4% that it will not matter if you stop charging the batteries at a cumulative total that fits your devices parameters. I love my LTO cells and wish that I had a SOL-ARK so do not feel like you did the wrong thing at all. 90% of the energy in these things is between 2.38 and 1.94 volts per cell or 57 and 47 volts. if your inverter and charger can work with that then you will be fine.

 

[fisherus]

Here's a copy of the email Daly sent me.
BATTERIES

Hello Mr. Craig，

Double checke with our engineer, we can set up the charge voltage cut off: 2.5V , the discharge voltage cut off:1.5V.

For your mentioned " BMS plays is twofold -- it Top and Bottom balances the cells of the battery between a high charge (Top) voltage" , I need to highlight it to you, our BMS its balance current is very low ( 35+/-5mA）， so it need your battery material with good cosistancy.

 

[AmpLee]

Here's a copy of the email Daly sent me.
BATTERIES

Hello Mr. Craig，

Double checke with our engineer, we can set up the charge voltage cut off: 2.5V , the discharge voltage cut off:1.5V.

For your mentioned " BMS plays is twofold -- it Top and Bottom balances the cells of the battery between a high charge (Top) voltage" , I need to highlight it to you, our BMS its balance current is very low ( 35+/-5mA）， so it need your battery material with good cosistancy.

Interesting. The gal I've been in communication with says that they cannot go above 20mA +/-5mA for charge current. This presents a bit of a problem for my setup as under ideal conditions with 12kw of panels, I would be well above 20mA. Although, I'm not sure ideal conditions would ever be a reality, especially with east facing panels, but still a bit concerning as I would like some headroom.

 

[fisherus]

Interesting. The gal I've been in communication with says that they cannot go above 20mA +/-5mA for charge current. This presents a bit of a problem for my setup as under ideal conditions with 12kw of panels, I would be well above 20mA. Although, I'm not sure ideal conditions would ever be a reality, especially with east facing panels, but still a bit concerning as I would like some headroom.

I wanted you to see this because I was amazed by how low the balance voltage was on your BMS. It will probably work but I have pause due to the extremely fast recharging rate of these batteries. If the batteries are fully charged and stay at that level they might be OK but,I feel they need to be what I requested at the 35+/-5A level. I have a resourceful friend who knows the inside out of lithium titanate batteries and I will check with him if you want.
This is why I bought 2 different set-ups of the Daly BMS'S, to try before I ordered the rest. I have bought too many unnecessary components in the past. Figured I would save money by testing a couple first, per advice of my acquaintance. Expensive learning experience but, I am finally getting there and so will you. Guarantee you that you can't go wrong with the SolArk 12k, as I don't think it presently has a close second.

 

[AmpLee]

I wanted you to see this because I was amazed by how low the balance voltage was on your BMS. It will probably work but I have pause due to the extremely fast recharging rate of these batteries. If the batteries are fully charged and stay at that level they might be OK but,I feel they need to be what I requested at the 35+/-5A level. I have a resourceful friend who knows the inside out of lithium titanate batteries and I will check with him if you want.
This is why I bought 2 different set-ups of the Daly BMS'S, to try before I ordered the rest. I have bought too many unnecessary components in the past. Figured I would save money by testing a couple first, per advice of my acquaintance. Expensive learning experience but, I am finally getting there and so will you. Guarantee you that you can't go wrong with the SolArk 12k, as I don't think it presently has a close second.

Right on. Thanks for the advice. I'm not putting another BMS order in until I'm sure of the specs.

In the message you posted above from Daly, I'm curious why you want the charge voltage cut-off at 2.5 instead of something higher like 2.7. Wouldn't having your charge voltage cut-off and balancing voltage both at 2.5 potentially mess with the BMS ability to balance. For example, say a cell reaches 2.5 while the rest of the cells are under and the BMS cuts off before it can balance. I was thinking of asking Daly to do the balance of 2.5 like you have, but the cut-off at 2.7 (which would be the natural high-point for the tech).

 

[fisherus]

The reason for the 2.5V is because I originally requested that they make them at a 2.5V level. I did this knowing my SolArk would never be able to exceed that amount of charge and thought it would serve as as additional safety mechanism. But, I am having them made to the 2.7V top and 1.5V bottom.
After all the research I have done on these batteries, I really think a BMS is pretty worthless as LTO batteries drift into balance continuously. I just wanted a way to check them annually for balance and after exploring what was available, this appeared to be the easiest. Necessary, probably not.