Daddy Tanuki
Emperor Of Solar
this is so redneck hold ma beer level of testing... I love it!
Battery Capacity Tester
- Thread starter epc2012
- Start date
BarracudaBob
Harvesting free photons from clean fusion
I've always found very good and accurate ways to do things relatively inexpensive and then my prime directive is not to lose the energy so either shove it back in the main battery pack which is slammed at 100% today why heat the pool
I can always stick an inverter on here or voltage multiplier or add more heaters for 12 volt ones.
I also have a 250 gallon hot tub I could have used to heat the water.
So many choices. By the way I'm burning sensitive documents in the smokeless pit while I'm waiting for my battery to die...
As Aerosmith would say, "going down"
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BarracudaBob
Harvesting free photons from clean fusion
Well I was distracted and didn't get to the computer fast enough. I was able to cycle the power and read the Victron Shunt before it turned back off. It looks like a coulomb counter and not LV cutoff turned off the BMS at 46.46V. My pool is now 5KW warmer (.1F)
Nice! That's not low tech in my book.
With that load and V, there's close to around 15 minutes left at 21A (.2C)...about 5.25Ah left if cells are well balanced. Again, I would love to see cell level data if possisble.
Daddy Tanuki
Emperor Of Solar
I used (past tense) 4 1300 watt hair dryers as a test load allowed me to tailor the load to how I was testing, best thing used units from 2nd hand stores so cheapI've always found very good and accurate ways to do things relatively inexpensive and then my prime directive is not to lose the energy so either shove it back in the main battery pack which is slammed at 100% today why heat the pool
I can always stick an inverter on here or voltage multiplier or add more heaters for 12 volt ones.
I also have a 250 gallon hot tub I could have used to heat the water.
So many choices. By the way I'm burning sensitive documents in the smokeless pit while I'm waiting for my battery to die...
As Aerosmith would say, "going down"
BarracudaBob
Harvesting free photons from clean fusion
I took a snippet and emailed it to myself (different accounts) and turned the computer off to fast so I didn't get it.. So I have it but now charging it back up over night. It was a SOC disconnect and not a LV disconnect. I'll check it in the morning and do it again...
BarracudaBob
Harvesting free photons from clean fusion
I used a 3k 48V inverter in the past but the question was did it turn off before the BMS did. That is why I came up with the water cooled dummy load idea.
Daddy Tanuki
Emperor Of Solar
if it works, it ain't stupid.
Does the bms allow you to disable the use of soc as a reference for cutoff? Can ot be set to V for the reference?
BarracudaBob
Harvesting free photons from clean fusion
Everything is adjustable. you can see "SOC to LOW" in the right Alarm State. Using a dumb resistant load takes any question of is the inverter turning off or the BMS. Besides for experimenting I see no reason to change it as I am not worries about one amp hour. 
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BarracudaBob
Harvesting free photons from clean fusion
I imaging if I set the pack amp hour for 105ah it would run down until a LV cell or pack alarm would occur. I also see if the cycle count go up enough to change the SOH, State of Health, it would also reduce the dischargeable amp hour. I saw this on the LifePower4 V1 batteries.
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I'm not worried about getting the max capacity. More concerned with soc drift and pack shutting down too early based on false SOC readings. Have you tested the pack to see at what current (Amps) level the BMS triggers a valid read?
BarracudaBob
Harvesting free photons from clean fusion
the resistor is constant so only thing that changes is the voltage in this setup. The current shunt on the bms didn't match the Victron Smart Shunt VSS so I tried doing a calibration on the BMS in the 24A range. It helped but they didn't track perfectly together. May just be using a 8 bit A to D and it can only be so accurate. In Will's video he reported a few amps drift between batteries so it is a thing.
I am charging it back up with it set to 105ah so interested if I can squeeze a few extra amps out of the cells & BMS. The LV should kick in before the coulomb meter triggers low SOC
BarracudaBob
Harvesting free photons from clean fusion
Ok, all charged up and put back on the "pool load" 
Look how nicely it balanced out
It is outside on the porch and a cool morning of 68F. Never though of putting a heating pad on it to increase capacity. Normally in a room running 86F. I wish my chargeverter would go higher. I did buy a cheep LPF Golf cart charger but not here yet.
Look how nicely it balanced out
It is outside on the porch and a cool morning of 68F. Never though of putting a heating pad on it to increase capacity. Normally in a room running 86F. I wish my chargeverter would go higher. I did buy a cheep LPF Golf cart charger but not here yet.
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BarracudaBob
Harvesting free photons from clean fusion
Still going but just about dead. So the coulomb counter plays a very active role with smart BMS's... So is it safe to say that it messes with the SOC and delivered Ah a little but may help the SOH over the long run? Seems like the dumb voltage BMS's will always outperform on the VSS unless you change the settings. I'll go back to factory but this question has been answered and my pool is ever so slightly warmer
Still going but just about dead. So the coulomb counter plays a very active role with smart BMS's... So is it safe to say that it messes with the SOC and delivered Ah a little but may help the SOH over the long run? Seems like the dumb voltage BMS's will always outperform on the VSS unless you change the settings. I'll go back to factory but this question has been answered and my pool is ever so slightly warmer
View attachment 280081
View attachment 280080
There's more potential (opportunities) for the BMS to initiate LVC at both cell and pack levels using soc vs using V, indepedent of what the inverter settings are unless the inverter overides the bms's operation mode. If LVC at cell level is say 2.50V, and there are still components on the board that is drawing power = runs into potential of complete shutdown.
If current was consistent and high enough intraday, SOC could be more accurate (but not by much) vs V, and easier to use for the average person, but I don't think it is a good idea to protect packs using SOC.
BarracudaBob
Harvesting free photons from clean fusion
I agree with you as long as everything's within safe voltage readings let it do what it does and get to work. Does seem to overcomplicate things greatly.
Something I picked up and will reiterated on his second Eco worthy video.
The smarter the BMS the lower your amp hour test may be
robby
Electronic Engineer
- Joined
- May 1, 2021
- Messages
- 5,301
So Bob what is your overall Impression so far?I agree with you as long as everything's within safe voltage readings let it do what it does and get to work. Does seem to overcomplicate things greatly.
Something I picked up and will reiterated on his second Eco worthy video.
The smarter the BMS the lower your amp hour test may be
BMS, Cell Balance and Ah?
BarracudaBob
Harvesting free photons from clean fusion
So the hypothesis was the cells have more capacity than the intelligent BMS will let it give. The BMS interacts not only by voltage but measured capacity. If that capacity isn't set accurately taking consideration the accuracy of the current shunt in the BMS then it's not going to deliver the rated 100 amp hours as advertised.
One of my batteries I tested was set for 102 amp hours and came out at 100 perfectly every time like it was pre tested where all the other ones were set for a hundred and gave her own 98 to 99.
So this was more about proving how much these smart BMS interact with output. For what I can tell from the settings is anything more than an 80% discharge it will start ticking back the state of health SOH, and other factors that'll pissed off to be a mess it'll negatively affect the SOH. I have an image I'll share later where I actually got a percent of SOH taken away from me and my test.
So as far as this battery and price no complaints had a lot of fun with it, price was right, and Will's video summed it up.
Every new battery I test will go through a balancing act deep discharge charge it won't go into production until I'm very happy with the results. Once it goes in the production in the main battery pack and it won't be touched for a very long time unless something happens...
Enjoy the absolutely beautiful South Florida weather, water dumping all these kilowatts into my pool, charging everything up from the main inverters, and cooking a really big thick chuck roast like a brisket on the Ninja wood fire grill runin' off PV & LPF. A little mesquite and hickory kiss
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robby
Electronic Engineer
- Joined
- May 1, 2021
- Messages
- 5,301
Sounds good to me as I don't go below 20% SOC on my batteries.So the hypothesis was the cells have more capacity than the intelligent BMS will let it give. The BMS interacts not only by voltage but measured capacity. If that capacity isn't set accurately taking consideration the accuracy of the current shunt in the BMS then it's not going to deliver the rated 100 amp hours as advertised.
One of my batteries I tested was set for 102 amp hours and came out at 100 perfectly every time like it was pre tested where all the other ones were set for a hundred and gave her own 98 to 99.
So this was more about proving how much these smart BMS interact with output. For what I can tell from the settings is anything more than an 80% discharge it will start ticking back the state of health SOH, and other factors that'll pissed off to be a mess it'll negatively affect the SOH. I have an image I'll share later where I actually got a percent of SOH taken away from me and my test.
So as far as this battery and price no complaints had a lot of fun with it, price was right, and Will's video summed it up.
Every new battery I test will go through a balancing act deep discharge charge it won't go into production until I'm very happy with the results. Once it goes in the production in the main battery pack and it won't be touched for a very long time unless something happens...
Enjoy the absolutely beautiful South Florida water dumping all these kilowatts into my pool. Cooking a really big thick chuck roast like a brisket on the Ninja wood fire grill runoff solar. A little musky and hickory smoke
Certain people on here keep saying it's fine to discharge down to 10% or even 0% and yet here we are three years later and the battery companies are still pegging their Warranty to that 20% level. I suspect they know a lot more than our experts.
BTW did you ask them about the Gender confused Positive Terminal Cap? It would be nice if it was Red and not Purple lol.
BarracudaBob
Harvesting free photons from clean fusion
I had an engineer stop by today and he basically said two things really simple don't do it
If you go below the 2.5 volts the carbon structure that captures the lithium ion falls apart. You're putting yourself at risk Don't do it
The second part is don't keep the batteries slammed at the top voltage for similar degradation reasons.
Keep them cool use them
He absolutely fell in love with my water cooled dummy load
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BarracudaBob
Harvesting free photons from clean fusion
FYI the DC house has been slowly chugging along I'll move that over to a different thread..
The 12 volts only pull 6 amps with my current load setup. This is its first discharge so the SOCs whacked but it's a simple BMS operated by voltage.
The 12 volts only pull 6 amps with my current load setup. This is its first discharge so the SOCs whacked but it's a simple BMS operated by voltage.
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BarracudaBob
Harvesting free photons from clean fusion
Don't be bad 
Triggered negative SOH
Triggered negative SOH
Yeah, that BMS takes the user input rated capacity (rc) and compares with its own soc calc to determine soh.
If you put in 200Ah rc, it'll calc soh at ~50%.
Do you have an idea the sampling rate it is using to calc soc integration? IS there a spec sheet for the bms?
Maybe I have to start reading the 100+ pages of your thread...
BarracudaBob
Harvesting free photons from clean fusion
It charged up all night so I'll post that once I get some Java in me.. want to finish this up in the curiosity program real world numbers and not be afraid to watch the SOH diminish as the cells truly age and degradation shows up. That degradation could even be over the rated capacity of the battery it would be true measured values.
Rated capacity is the absolute top max number
Full capacities what you were able to get the cells to within the parameters programmed into the BMS like overvoltage coulon counter, etc.. The difference between rated and full capacity is your state of health.
Remaining capacity is how much you have left the pull out of the cells.
If these aren't all set up in the beginning properly that will affect the capacity test.
So if you get everything you can out of the battery and set these numbers up as the battery ages you'll watch the SOH come down in real world values and you shouldn't be scared because if the battery was putting out more than it's rated current but then slowly starts diminishing it's real world numbers.
A BMS "rated capacity" refers to the manufacturer's specified capacity of a battery, which is the expected maximum amount of energy it can store under standard conditions when new, while "full capacity" usually refers to the absolute maximum amount of energy a battery can store, including a small portion that may not be accessible due to safety limitations imposed by the BMS, meaning the rated capacity is always slightly less than the full capacity.
Rated capacity:
This is the capacity listed on the battery specifications, considered the reliable and safe amount of energy you can expect to draw from the battery under standard conditions.
Full capacity:
This represents the theoretical maximum amount of energy a battery can hold, but may not be fully usable due to safety measures implemented by the BMS to prevent damage.
Rated capacity is the absolute top max number
Full capacities what you were able to get the cells to within the parameters programmed into the BMS like overvoltage coulon counter, etc.. The difference between rated and full capacity is your state of health.
Remaining capacity is how much you have left the pull out of the cells.
If these aren't all set up in the beginning properly that will affect the capacity test.
So if you get everything you can out of the battery and set these numbers up as the battery ages you'll watch the SOH come down in real world values and you shouldn't be scared because if the battery was putting out more than it's rated current but then slowly starts diminishing it's real world numbers.
A BMS "rated capacity" refers to the manufacturer's specified capacity of a battery, which is the expected maximum amount of energy it can store under standard conditions when new, while "full capacity" usually refers to the absolute maximum amount of energy a battery can store, including a small portion that may not be accessible due to safety limitations imposed by the BMS, meaning the rated capacity is always slightly less than the full capacity.
Rated capacity:
This is the capacity listed on the battery specifications, considered the reliable and safe amount of energy you can expect to draw from the battery under standard conditions.
Full capacity:
This represents the theoretical maximum amount of energy a battery can hold, but may not be fully usable due to safety measures implemented by the BMS to prevent damage.
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