Doctorbass
100 GW
Hello guys.. Long time no post for me.. I was quite busy these months.
I have found some aspect of the UL2271 certifications that seem to not be properly adressed and i would like to get your opinion about that if you have valuable info.
Adressing CELL SPACING!
With all these fires from ebike battery we see from cheap and badly constructed ebike battery, the thermal runaway as well as the thermal PROPAGATION are very important aspect to adress. Thermal runaway start usually with one cell being abused or having a problem itself while thermal propagation is related to the spread of this first cell thermal energy to the rest of the cells surounding it. Cheap battery often have from 0 to 0.5mm spacing between them, many have 1 to 1.25mm up to 2mm in rare cases.
Few research papers are talking about AT LEAST 2mm and some large battery company are mentionned by some "battery specialist" usually take 3mm spacing which I have never observed personally.
I have read many papers from NASA and JPL regarding tests and cell spacing in relationship beetwen cell spacing and the thermal propagation intensity&spread and it seem that 2mm seem a minimum. But ok.. Yes.. space suit and ebike are not the same environment I know!
Adressing Maximum ebike battery VOLTAGE!
The ebike industry began two decades ago with 24V battery on lead acid and some 36V nimh and nicad.. then 48V came to the market with lithium ion chemistry. but.. Why 48V maximum? Some DC safe voltages are mentionned as no more than 60Vdc..
Which voltage are we talking about??
Is it a NOMINAL voltage or a MAXIMUM voltage?..
I have found absolutely NO mention about that in any UL2271 or UL2849 and many other Canadian and UL document.
Because a 48V lithium-ion battery is working from 32.5Vdc to 54.6Vdc usually..
However.. Lead acid battery in 48V (usually 4 x 12V battery) configuration will recharge at 15V per 6s(12V) battery when they are cold! and 4 x 15V is 60VDC !
So.. why not having a Lithium ion battery above 48V.. nominal ( 54.6Vdc ful charge) then?
It seem to me that there is still room for one more group in serie for 14s at 51.8Vnom and 58.8V full charge? I even say two UL certified battery with 52V label on them! Adding one P in a 13s group require adding 13 cells which make battery cell qty multiple a big jump!.. But adding 1s will require only 3, 4 or 5s
Also BMs chip are already offered in 14s config for ESS battery...
Electrical components ( not cell) spacing and the max voltage are two criteria that are in relationship together when designing a UL compliant or certified .
The voltages mentioned in some tables like the 13.1(electrical spacing) are not specified as a value of Nominal voltages or maximum voltages.
The table 13.1 of the UL2271 has one range from 0 to 50Vdc and one from 51 to 130Vdc. But none of them indicate what voltage type it is.
If taking the NOMINAL voltage of a 48 V ebike battery, the spacing would need to be in the 0-50Vdc row.. But if we take that 48 V battery as a FULL charged voltage at 54.6Vdc.. Then we need to take the number of the second row of 51 to 130Vdc.
Doc
I have found some aspect of the UL2271 certifications that seem to not be properly adressed and i would like to get your opinion about that if you have valuable info.
Adressing CELL SPACING!
With all these fires from ebike battery we see from cheap and badly constructed ebike battery, the thermal runaway as well as the thermal PROPAGATION are very important aspect to adress. Thermal runaway start usually with one cell being abused or having a problem itself while thermal propagation is related to the spread of this first cell thermal energy to the rest of the cells surounding it. Cheap battery often have from 0 to 0.5mm spacing between them, many have 1 to 1.25mm up to 2mm in rare cases.
Few research papers are talking about AT LEAST 2mm and some large battery company are mentionned by some "battery specialist" usually take 3mm spacing which I have never observed personally.
I have read many papers from NASA and JPL regarding tests and cell spacing in relationship beetwen cell spacing and the thermal propagation intensity&spread and it seem that 2mm seem a minimum. But ok.. Yes.. space suit and ebike are not the same environment I know!
Adressing Maximum ebike battery VOLTAGE!
The ebike industry began two decades ago with 24V battery on lead acid and some 36V nimh and nicad.. then 48V came to the market with lithium ion chemistry. but.. Why 48V maximum? Some DC safe voltages are mentionned as no more than 60Vdc..
But I see two confusions here:
Which voltage are we talking about??
Is it a NOMINAL voltage or a MAXIMUM voltage?..
I have found absolutely NO mention about that in any UL2271 or UL2849 and many other Canadian and UL document.
Because a 48V lithium-ion battery is working from 32.5Vdc to 54.6Vdc usually..
However.. Lead acid battery in 48V (usually 4 x 12V battery) configuration will recharge at 15V per 6s(12V) battery when they are cold! and 4 x 15V is 60VDC !
So.. why not having a Lithium ion battery above 48V.. nominal ( 54.6Vdc ful charge) then?
It seem to me that there is still room for one more group in serie for 14s at 51.8Vnom and 58.8V full charge? I even say two UL certified battery with 52V label on them! Adding one P in a 13s group require adding 13 cells which make battery cell qty multiple a big jump!.. But adding 1s will require only 3, 4 or 5s
Also BMs chip are already offered in 14s config for ESS battery...
Electrical components ( not cell) spacing and the max voltage are two criteria that are in relationship together when designing a UL compliant or certified .
The voltages mentioned in some tables like the 13.1(electrical spacing) are not specified as a value of Nominal voltages or maximum voltages.
The table 13.1 of the UL2271 has one range from 0 to 50Vdc and one from 51 to 130Vdc. But none of them indicate what voltage type it is.
If taking the NOMINAL voltage of a 48 V ebike battery, the spacing would need to be in the 0-50Vdc row.. But if we take that 48 V battery as a FULL charged voltage at 54.6Vdc.. Then we need to take the number of the second row of 51 to 130Vdc.
Doc
