LifePO4 @ 0V, one recovery, one failure
- Thread starter methods
- Start date
Bbbbrass
1 W
Gulp, hopeful before you ordered you saw in the other thread where I posted pictures of the Mosfets!
DogDipstick
100 kW
john61ct said:
I have used most of those in applications. What doyou want to know?
Would you like to know more?
methods said:
That is your SC Current testing machine?
Gee i just use a K-Welder machine on the calibrate setting. Tells me the milliseconds and teh amps up to 2000A. Good voltage ranges for my stuff. Frank said it is a direct measurement of peak SCC and time.
Further calculation is available if you have these informations.
....are you sure your testing machine is " fast enuf'.... ? What about a much more powerful cell that might act differently ( time to make full SCC)..
.... Are you testing the output of the cell... or are you just testing the response time of the BMS? I dont get it. Why not use an oscilliscope for the BMS test. I like to use the SSC test to determine the maximum current the cell will push ( helpful when designing Zipper fuses).
I hear they are fast and accurate. Nowadays. In the measurement of time. Current. Voltage. Such as the like. I mean,, can you not capture and record a short event easily with a scope? Digitally referenced?
If I could afford 800$ of Mosfets i would own the DSO first. Certainly you are skilled with the recording of current and voltage wave forms. With the education you have.
My Tektronik is from 1963. I wish I could afford a real scope.
methods
1 GW
From Road
BMS landed from battery space. There was perfect tracking with GPS and they landed right on time. The box was completely taped over for rain. It was very professionally packed tight.
Each BMS was new in a bag. They look very nice!
I was able to look up that MOSFETs and I have the data sheets. I was able to confirm the TVS diodes were on the board, and it is an advanced design.
Everything about it was an order of magnitude higher quality and more professional than the last BMS I reviewed! All of the parts are on the top of the board, The board is conformal coated, The thermal transfer material is sticky, it only has four fasteners, definitely machine assembled, ...
... These things are not jankum
There's eight MOSFET slots per bank with five populated on each.
... Me and the wife are sick but I'll wake up early and document it all tomorrow. It's looking like I got hooked up phat
-methods
BMS landed from battery space. There was perfect tracking with GPS and they landed right on time. The box was completely taped over for rain. It was very professionally packed tight.
Each BMS was new in a bag. They look very nice!
I was able to look up that MOSFETs and I have the data sheets. I was able to confirm the TVS diodes were on the board, and it is an advanced design.
Everything about it was an order of magnitude higher quality and more professional than the last BMS I reviewed! All of the parts are on the top of the board, The board is conformal coated, The thermal transfer material is sticky, it only has four fasteners, definitely machine assembled, ...
... These things are not jankum
There's eight MOSFET slots per bank with five populated on each.
... Me and the wife are sick but I'll wake up early and document it all tomorrow. It's looking like I got hooked up phat
-methods
yes if you could "review" some of the various units and sources of the many made by JBD/LLT that would be a tremendous service to the communityDogDipstick said:
deserving of its own thread if detailed enough IMO.
Even vague generalities are helpful though, the only BMS reco's given with confidence and certitude are for ones costing hundreds
the cheaper ones seem to always be a roll of the dice.
The "smart" ones reporting per-cell/group voltages, showing balancing progress would to me be essential whether via BT or not
but not at the expense of accuracy nor longevity / reliability
methods
1 GW
Vpeak = <60V
Vdd = 85V
25V of Margin
Backed by protection Diodes Populated
Rdson = 5.5mOhms
5 in parallel for 1.1mohms per bank
Common Port Design, so 2.2mOhms + shunts in series
Since we generally deal in banks and not totals, 1.1mOhms is quite good.
30A * 30A * 1.1mOhms = 0.99W
(which is no accident)
Calculated 1mohms ON
Calculated 1W Waste at Max
Those are Engineers Numbers, they could have populated 8 and did not
-methods
Vdd = 85V
25V of Margin
Backed by protection Diodes Populated
Rdson = 5.5mOhms
5 in parallel for 1.1mohms per bank
Common Port Design, so 2.2mOhms + shunts in series
Since we generally deal in banks and not totals, 1.1mOhms is quite good.
30A * 30A * 1.1mOhms = 0.99W
(which is no accident)
Calculated 1mohms ON
Calculated 1W Waste at Max
Those are Engineers Numbers, they could have populated 8 and did not
-methods
Attachments
methods
1 GW
Without scrolling back?
Short Circuit Tester?
What is mine made of?
Well YEA I have a scope on it (Fluke Scope Meter, Isolated) but the scope measurements (Across a 100A shunt) are of little value. These are transient numbers and not something to throw around. Far more useful is a PRACTICAL MEASURE of performance under representative load.
I have a very big and complicated one. Depends on whether I am trying to get a crowbar short or representative. For Crowbar I use Golf Cart Cables into a Shunt and that usually results in batteries puffing and getting very dangerous very quickly. For representative failure I use
* Anodized Aluminum
* Bald 12AWG copper wire
* Slap them together
That presents a most realistic short. To self Extinguish I have 4 layers of protection
* 500V DC Breaker that terminates OPEN within 5mS (I short that out when I need different tests)
* Golf Cart 48V Heavy Relay hooked to ESTOP that never opens under load
* Golf Cart 48V Heavy Relay hooked to ESTOP that fires the test when not in slap-mode
* 12V Starting Breaker in series, 150A (garbage welded short)
* 12V Starting Breaker in series, 300A (garbage)
So Basically I have a bunch of redundant breakers and contactors in series to allow me to terminate discharge in the event that it gets away from me. No fuse.
I started out by triggering tests with the ESTOP but it was too harsh. It was borking packs. I later settled on manual sparking. If the BMS is a failure, it welds. If the BMS is a success, it sparks the first time but not subsequent times. There is then some hysteresis and repeat.
This is ultimate Self Protection Mode required for any BMS claiming to protect from Charge/Discharge. Without it, you cant tell if you are already in failure mode.
-methods
Short Circuit Tester?
What is mine made of?
Well YEA I have a scope on it (Fluke Scope Meter, Isolated) but the scope measurements (Across a 100A shunt) are of little value. These are transient numbers and not something to throw around. Far more useful is a PRACTICAL MEASURE of performance under representative load.
I have a very big and complicated one. Depends on whether I am trying to get a crowbar short or representative. For Crowbar I use Golf Cart Cables into a Shunt and that usually results in batteries puffing and getting very dangerous very quickly. For representative failure I use
* Anodized Aluminum
* Bald 12AWG copper wire
* Slap them together
That presents a most realistic short. To self Extinguish I have 4 layers of protection
* 500V DC Breaker that terminates OPEN within 5mS (I short that out when I need different tests)
* Golf Cart 48V Heavy Relay hooked to ESTOP that never opens under load
* Golf Cart 48V Heavy Relay hooked to ESTOP that fires the test when not in slap-mode
* 12V Starting Breaker in series, 150A (garbage welded short)
* 12V Starting Breaker in series, 300A (garbage)
So Basically I have a bunch of redundant breakers and contactors in series to allow me to terminate discharge in the event that it gets away from me. No fuse.
I started out by triggering tests with the ESTOP but it was too harsh. It was borking packs. I later settled on manual sparking. If the BMS is a failure, it welds. If the BMS is a success, it sparks the first time but not subsequent times. There is then some hysteresis and repeat.
This is ultimate Self Protection Mode required for any BMS claiming to protect from Charge/Discharge. Without it, you cant tell if you are already in failure mode.
-methods
methods
1 GW
Half Way thru wiring up the Balance Taps
* PVC has a much lower melting temperature than silicone. I much prefer silly-wire balance taps, even if they abrade easy.
* Whips are pin incompatible and easy to read, plenty long. You need 17, so 8 top, 8 bottom, and an extra on the bottom to catch GND
* Taps are just like any other in this awful industry, someone ran a bead along the bottom. My guess is that the taps came off of (enter website here) and they are not OEM. OEM is probably a part of a pack someplace and I bet those do not have a bead of RTV.
Maybe they do tho
So I got GND and cells 1-8 wired
They rested for a month and landed like this
3.1
0.1
3.2
3.2
0.2
3.2
3.2
3.2
3.2
3.2
3.2
3.2
3.2
3.2
3.2
3.2
So we have two cells out of 16 which we will use to evaluate the safety and efficacy of this BMS both on LVC and HVC. If you think YOUR PACK does not have a couple soft cells like this, then you need to
* Peel back the Duct Tape
* Actually buy a Volt Meter
* Measure your frigging cells
Anybody not measuring cells (all of them) at this point is just trying to have a fire at their house. A nice, warm, fire.
O N W A R D
-methods
* PVC has a much lower melting temperature than silicone. I much prefer silly-wire balance taps, even if they abrade easy.
* Whips are pin incompatible and easy to read, plenty long. You need 17, so 8 top, 8 bottom, and an extra on the bottom to catch GND
* Taps are just like any other in this awful industry, someone ran a bead along the bottom. My guess is that the taps came off of (enter website here) and they are not OEM. OEM is probably a part of a pack someplace and I bet those do not have a bead of RTV.
Maybe they do tho
So I got GND and cells 1-8 wired
They rested for a month and landed like this
3.1
0.1
3.2
3.2
0.2
3.2
3.2
3.2
3.2
3.2
3.2
3.2
3.2
3.2
3.2
3.2
So we have two cells out of 16 which we will use to evaluate the safety and efficacy of this BMS both on LVC and HVC. If you think YOUR PACK does not have a couple soft cells like this, then you need to
* Peel back the Duct Tape
* Actually buy a Volt Meter
* Measure your frigging cells
Anybody not measuring cells (all of them) at this point is just trying to have a fire at their house. A nice, warm, fire.
O N W A R D
-methods
methods
1 GW
(these are the raw notes, if the build actually works and passes testing I will write up the BMS's with all the fancy pictures collected along the way)
methods
1 GW
First test
* Blocks charge
* Unblocks charge at exactly 1.3 volts
So it will not charge a pack of any cell is below 1.3 volts. Good to know if you have a healthy self-discharge. To overcome this you may consider a higher pack level LVC to get you through the night.
* Pretty LEDs
I saw them sparkle when I first plugged it in
-methods
* Blocks charge
* Unblocks charge at exactly 1.3 volts
So it will not charge a pack of any cell is below 1.3 volts. Good to know if you have a healthy self-discharge. To overcome this you may consider a higher pack level LVC to get you through the night.
* Pretty LEDs
I saw them sparkle when I first plugged it in
-methods
methods
1 GW
" it has an unpopulated external temperature probe
(A second, The primary is populated)
-methods
(A second, The primary is populated)
-methods
methods
1 GW
Overheating the external probe causes it to shut down. It will not turn back on unless you remove the load!
* About 10 seconds of hysteresis
* Requires the load to stop
The load was tiny, just leakage into this crappy RC meter.
* Applying charge cleared the fault
... Overheating the external propagand this time while charging
* Self-clear is in about 10 seconds
So if you overheat at idle it's going to lock up on you until your next charge cycle. That works for me.
-methods
* About 10 seconds of hysteresis
* Requires the load to stop
The load was tiny, just leakage into this crappy RC meter.
* Applying charge cleared the fault
... Overheating the external propagand this time while charging
* Self-clear is in about 10 seconds
So if you overheat at idle it's going to lock up on you until your next charge cycle. That works for me.
-methods
methods
1 GW
Heating the plate to over 100 seed is not cause the unit to stop discharging. The back is still cool while the front cannot be touched.
* Blowing hot air across the PCB board
The plastic backing material warped and sorted melting pretty quickly it's actually quite stiff after it melts. It may or may not be a nema rated plastic.
Overheating the primary PCV board did cause it to shut down! It remains shut down until I cycled the load. It would not self-clear from charging.
* Attaching charger
* Overheating PCB
It definitely terminates a charge if you overheat the PCB. It does not self correct... Which is good, at the design phase.
Boy I really pissed it off Good here! It's got a pretty big thermal mass so once it gets hot it stays hot.
Took like a minute of cycling the connector. I need to make sure that's not just hysteresis.
* Applying charge
* Overheating
* Force cooling
Okay correction it will self correct if the PCB board overheats.
So far so good
-methods
-methods
* Blowing hot air across the PCB board
The plastic backing material warped and sorted melting pretty quickly it's actually quite stiff after it melts. It may or may not be a nema rated plastic.
Overheating the primary PCV board did cause it to shut down! It remains shut down until I cycled the load. It would not self-clear from charging.
* Attaching charger
* Overheating PCB
It definitely terminates a charge if you overheat the PCB. It does not self correct... Which is good, at the design phase.
Boy I really pissed it off Good here! It's got a pretty big thermal mass so once it gets hot it stays hot.
Took like a minute of cycling the connector. I need to make sure that's not just hysteresis.
* Applying charge
* Overheating
* Force cooling
Okay correction it will self correct if the PCB board overheats.
So far so good
-methods
-methods
methods
1 GW
* starting in 19 amp charge with the unit just coming out of overheat
This is exactly a thousand watt charge. The MOSFET should be putting about two watts into the assembly. It's free air at an angle.
* Does it overheat
* Does it stabilize
* Does it cool down
-methods
This is exactly a thousand watt charge. The MOSFET should be putting about two watts into the assembly. It's free air at an angle.
* Does it overheat
* Does it stabilize
* Does it cool down
-methods
methods
1 GW
The unit was steadily cooling down at a 20 amp charge so we are golden to move forward with testing. All of that was just with the meanwhile power supply.
* Now we need to load cycle
We use the BMS killer
* SPF 5000 ES
This thing dominates
-methods
* Now we need to load cycle
We use the BMS killer
* SPF 5000 ES
This thing dominates
-methods
methods
1 GW
2.3V LVC
2.5V return
The battery is now as flat as it's going to get. Going to charge it all the way up using the SPF 5000 ES. We expect balancing to be aggressive with one cell very low and all the rest full.
* This is the most common case
* One or two cells are weak
* All the rest are strong
Never let the weak hold back the strong. Feed the weak to the Lions and move on.
-methods
2.5V return
The battery is now as flat as it's going to get. Going to charge it all the way up using the SPF 5000 ES. We expect balancing to be aggressive with one cell very low and all the rest full.
* This is the most common case
* One or two cells are weak
* All the rest are strong
Never let the weak hold back the strong. Feed the weak to the Lions and move on.
-methods
methods
1 GW
Overheated the external sensor while it was under a 20 amp charge. It terminated charge and then recovered.
* This is the action that was destroying the DALY BMS
* After one hit the MOSFETs would be done
This BMS is a bit more fussy... But fussy is a good thing. You should never be banging off of LVC on the BMS.
* You should never bang off of cell level LVC
* You should never bang off of thermal limit external
* You should never bang off of thermal limit internal
* HVC is a different story
Leaving amp hour in the pack and never hit LVC is my advice. Now let's trigger that again
* 20 amp charge session
* Heated up the external thermistor
* The BMS terminated charge
The BMS then self-recovered without any interaction against the SPF 5000 ES
(I've got the signature solar version, not the UK version)
Remember that I just plug it into the wall 120 to use as a battery charger. ***
PASS
So far this BMS is better in every way than the DALLY. It runs ice cold. Pretty soon going to be able to say I got hooked up.
-methods
* This is the action that was destroying the DALY BMS
* After one hit the MOSFETs would be done
This BMS is a bit more fussy... But fussy is a good thing. You should never be banging off of LVC on the BMS.
* You should never bang off of cell level LVC
* You should never bang off of thermal limit external
* You should never bang off of thermal limit internal
* HVC is a different story
Leaving amp hour in the pack and never hit LVC is my advice. Now let's trigger that again
* 20 amp charge session
* Heated up the external thermistor
* The BMS terminated charge
The BMS then self-recovered without any interaction against the SPF 5000 ES
(I've got the signature solar version, not the UK version)
Remember that I just plug it into the wall 120 to use as a battery charger. ***
PASS
So far this BMS is better in every way than the DALLY. It runs ice cold. Pretty soon going to be able to say I got hooked up.
-methods
methods
1 GW
After 10 amp hours the BMS is not producing enough heat to overheat. If there is any convection, any thermal path, it is going to work.
-methods
-methods
methods
1 GW
I'm still testing the battery hookup BMSs. I've got them on a solar rig that pounds them every single day.
I think I've got five packs running all in parallel. So far I can tell you only this.
* It doesn't seem like anything has locked up
* It doesn't seem like anything has smoked
Remember I've got them up against a really mean charger/discharger, the 5000ES. It's about time to go pull them from the field and repeat our incoming inspection.
If it passes I will build up the remaining 20 BMSs. I think I build up six or seven so far. It's a lot of work.
-methods
I think I've got five packs running all in parallel. So far I can tell you only this.
* It doesn't seem like anything has locked up
* It doesn't seem like anything has smoked
Remember I've got them up against a really mean charger/discharger, the 5000ES. It's about time to go pull them from the field and repeat our incoming inspection.
If it passes I will build up the remaining 20 BMSs. I think I build up six or seven so far. It's a lot of work.
-methods
Then we just have to hope the company making those has kept making them the same way with the same parts so the next batch(es) still work like these. 
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