Teardown: LithiumPros LithiumPowerPack 12v and 36v

[amberwolf]

I won't get to the actual teardown for at least a few days, but Cvin dropped off these failed units for experimentation. The 12v is more swollen than the 36v, but the 36v is actually broken across the bottom of the case (probably from an impact rather than the swelling, can't tell till I get into it).

I think she said they're from around 2018. My guess is that some or all of the cells have swollen up and failed, I doubt there is compression structure in there to minimize this issue; if there is it apparently didn't work. Probably LiFePO4.

If there is a BMS it might still be good, and useful, as might any interconnects.

The casing for the 12v unit might be useful to seal up a different pack in (like for my newer trike); I think some of my EIG cells would fit inside, possibly even an entire 14s2p 52v 40Ah pack. Would be nice for the environnmental sealing. The 36v casing (cracked) might be repairable; I have a heat-tool that's designed for this kind of work to melt plastics back together (it's probably a PE type of plastic, and thus ungluable).

Photodump below:

 

[amberwolf]

Had to be outside waiting on something to finish anyway, so I popped open the dead 12v pack. (which reads 0v at the terminals; I think the 36v unit reads 39v).

The body shell was cracked along one corner from the extreme swelling, pulling at the corner by tension when it wasn't designed for that. So I went ahead and just pried the top off; this broke several pieces off the top's edges, but it is still intact enough to reseal to the casing if I should decide to use it for a different battery.

It had originally been built with a foam rubber gasket between the lid and the body shell, and a clear glue that had hardened into an inflexible beaded layer had been applied to the outer face of the gray body shell where it would be overlapped by the white lid. This glue was not evenly applied, but it was present all along the entire seam gap.

The BMS is in the lid, secured there by the spray foam they filled the top of the casing with. The spray foam doesn't appear to extend all the way down all sides of the body shell and cell block inside, but I haven't attempted to extract the cell block yet (prefer not to damage it further, so considering ways to do it without cutting the body shell apart).

There is no cell block compression mechanism, it simply has two wraps of brown plastic packing tape midway from each end to the center of the length of the cell block. This tape has stretched so much that there are clear bands in the brown. For an $1800.00 (yes, one thousand eight hundred dollar) battery, I'd expected to find good mechanical design....

There is obvious cell swelling in cells 3, 7, and 14,

and cell 14 is very obviously ruptured in the middle of the edge visible once the BMS / lid was moved away.


The groups from most negative to most positive read
2.24
3.29
3.129
0.677 (with the ruptured cell)

The BMS is quite complex, and is probably a good design; haven't seen one like it before.

I haven't been able to locate a manufacturer or datasheet yet. One label says SB-78v6-12v-110 or 11(ohmsymbol); can't tell which, and A001 PH00 (or PHCA) 007. Another label has some chinese characters I have not been able to translate yet, then 2017/03/19, then 20171122-R12. Attempted translation has come up wiht "software" or "stylistic" or "+". Best guess is that it is the firmware revision onboard.

It appears to have individual shunts on each FET (guessing the ones on the short edge are for charge, long edge for discharge, but haven't traced anything out yet; it's a common port BMS), so it could then monitor each individual FET and actually tell if any have failed open or shorted, if so.

It also has two thermal sensors (probably tyupical thermistors) connecte dto it (one's wire tore during pack opening), but the sensors themselves were both placed within an inch of each ohter inside the sprayfoam close to the outer gray shell, nearly a centimeter from the cells, at the end of the pack opposite all the cell interconnects. Seems pretty dumb, but I don't know what they were using them for (if just for external temperature detection, that would be ok, but I'd've put one each on opposite ends, if so).



It appears to be an 8S BMS (there are 8 sets of 3 parallel balance shunt resistors, and the balance/sense connector is 9 pins; it only uses six of them, two of which are connected to the same cell junction, as is common with multi-cell-configuration-compatible BMSes). The balance connector also appears to have contact oxidation or corrosion but I see no sign of water intrusion, so my guess is reaction from whatever offgassed from the sprayfoam.

 

[BatteryMooch]

Thank you for posting that teardown!
Considering the price, that pack would technically be called A Piece Of Junk.
The cell handling/mounting is almost criminally negligent.

That BMS has a huge number of passives. It would be great to see the other side if not too inconvenient.
Interesting ”daughter board” bodge they got there too! Just the opto and some passives?

 

[amberwolf]

Thank you for posting that teardown!

I haven't seen a teardown of any of these commercially available marine / starter / etc batteries, so when the chance came to get a couple dead ones I wouldn't feel bad about destroying if it came to that....

Considering the price, that pack would technically be called A Piece Of Junk.
The cell handling/mounting is almost criminally negligent.

I think it would technically be called theft (of the buyer's presumably hard-earned cash) :lol:
But apparently these things are commonly used in all sorts of boating / etc applications successfully. I didn't search hard but I didn't find a fire involving one yet.

Hopefully they make them better now (this one's BMS is from 2017 and the pack is supposedly from about 2018 or so, so they have had plenty of time to learn and make their stuff better...though since money talks louder than engineers I wouldn't bet on it.

That BMS has a huge number of passives.

The ones that are along the edge of the board appear to be shunts (R003) for each charge/discharge FET, from the very little looking I did at it while taking the pics. The BMS is supposed to be good for 1,500Amps MCA*** (30seconds), and 100A continuous, so these must be pretty good FETs. There are 12 along each edge where the long gold traces are with screws in them, for a total of 24. Dunno which FET is used yet.

The 220 (or 022) ones in the 3x8 array appear to be the balancers, setup as 3 in parallel for each channel. I don't know offhand how much balance current that would allow, but I suspect it's not much, even for such a huge BMS.

***from a websearch: "The marine cranking ampere (MCA) rating of a battery is very similar to the CCA rating; the only difference is that while the CCA is measured at a temperature of 0°F, the MCA is measured at 0°C. All other requirements are the same — the ampere draw is for 30 seconds and the end of discharge voltage in both cases is 1.20 volts per cell. or 7.2 volts for the whole battery."

It would be great to see the other side if not too inconvenient.
Interesting ”daughter board” bodge they got there too! Just the opto and some passives?

There will be much more detail as I have time and energy to poke at it. (in the meantime the cells are out in the far shed in a metal cabinet, just in case. ).

I don't know what hte opto might be for...been trying to think what might have to be isolated but still read by the BMS (id on't know if it's an analog or digital signal or what it's connected to).

The BMS is on the workbench, but since it is probably perfectly functional, I only want to work on it when I'm not exhausted (a rare condition) and likely to break something on it. That way I can use it on new cells (well, used EV cells from greentecauto probably, once I find a useful deal I can afford) whenever I get some, or on the remaining non-failed cells in this pack (if there are any--I suspect they'll all poof right up as soon as I get the block out of the shell).

I bet that this is a programmable BMS, but that's not useful info without being able to get the programming software. There's a pad marked SENS-UART at one corner of the board. and at another spot on the other end of it too, along with EN-UART and some others I can't quite make out over by the main B- terminal.

There are ohter pics I couldn't fit in the post above that are dumped in this post below. One is a red wire going to the screw post that's over by what is probably a regulator. I bet that this red wire is the positive for the first cell block, and that's what killed it--powering the BMS only from taht group drained it dead just sitting around not being charged for who knows how long. (no info about it's former life, usage, or abuse is available). I forgot to measure the voltage on that wire relative to other wires.

 

[BatteryMooch]

Thank you @amberwolf for the extra photos. That’s a burly-looking BMS…wow.
For the resistors you noted, I agree. I’m amazed though by the number of passives in the central portion of the board. But perhaps that’s due to its age, before the high level of integration (into single chips or low chip count boards) we have now.

 

[amberwolf]

I’m amazed though by the number of passives in the central portion of the board. But perhaps that’s due to its age, before the high level of integration (into single chips or low chip count boards) we have now.

Oh, sorry, I didn't realize you were talking about the general design with all the discrete components (vs ICs).

I don't know the specific reason they did it this way, but it could've been that the functions they wanted didn't exist in available ICs yet, or maybe they needed something that wasn't possible with an IC, or whatever. Or maybe they just wanted all those nicely-labelled test points out in the open. I doubt I would be able to reverse engineer the board even if I had time to trace it all out and draw it up....

 

[amberwolf]

Photodump of the other side, under the heatsink. The sprayfoam was on there good, so you can't see everything, but some of it's pretty clear after peeling off what I could without risk of component damage.

There is a second connector next to the balance connector, same type, but vertical and filled with foam. Havne't traced anything out, so don't know if this is a second set of channels for the second set of resistors on this side, or if it's for something else and the ones on this side are paralleed with the ones on the other side. If it is sparate, it means this is actually a 16-channel (16s) BMS.

Therea re two major IC chips, one of which is obsucred by the foam residiue but the other/s markings are clear, shoudl be in the pics below (haven't looked at the pics yet, just dumping them here as I'm too tired to do much else). There are some other less complex chips that should also be readable-markings; they're over by the balance shunt resistors.

There's more FET-monitoring resistors on this side, AFAISC are wired in parallel with the others.

Had some ohter thoughts while the pics uploaded but dozed off and dont' recall them now.

 

[BatteryMooch]

Thanks for posting those!
I can see the Microchip MCU and some latches, perhaps to hold the balancing channel on/off states. Can’t read any other chip numbers but no worries as I’m not going to dive into the design any further. Always really enjoy seeing how a commercial BMS is designed and laid out though!

 

[amberwolf]

The SB-78 v6 on this side of the board led me to the image and website below, which has some specs on it, so it is actually an 8S capable unit being used as 4s (wiring diagram at the end). All the images below are clickable thumbnails.

One feature noted in the diagram is that it has balancing LEDs, next to the vertical connector of the same type as the balance connector, and an RS232 port next to that at the edge of the board around the corner, and an I2C port on teh oppoosing edge fo the board..

www.soontop.com.tw

The one that appears to match the one I have here is this:

::::: 春豆科技股份有限公司 SOONTOP TECHNOLOGY CO., LTD.:::::

春豆科技股份有限公司 SOONTOP TECHNOLOGY CO., LTD

www.soontop.com.tw

Copy/paste of the whole page below, with inline translations as available:

1. 首頁
2. 產品與服務
3. 汽車啟動電池保護板BMS
4. 24V 8S 鋰鐵啟動電池BMS
5. SB-78o-F-24-110 8S鋰鐵啟動電池BMS

SB-78o-F-24-110 8S鋰鐵啟動電池BMS​

SB-78o-F-24-110 8S Lithium Iron Starter Battery BMS​

分類：​

24V 8S 鋰鐵啟動電池BMS

描述：​

專門為鋰鐵汽車啟動電池設計的保護板BMS

Classification:​

24V 8S LiFePO4 Starter Battery BMS

describe:​

BMS protection board specially designed for lithium iron car starting battery

Specification​

特點:
1. 額定持續放電電流：110A，瞬間最大2000A <10mS
2. 分梯電流管理(Gradient Current Management)：依抽取電流大小進行放電保護時程控制。
3. 大電流耐受能力：負載短路保護電流在2000A，延遲≦10m S。
4 浮動分流電壓平衡: 浮動分流平衡，分流值以電芯差壓大小自動調整，平衡能力300m A (參考規格)。
5. 自動休眠與喚醒功能(Shutdown-Sleep &Wake up by Self-Recognition) : 自動計時進入休眠，此時零功耗
(1)空載. 以充電或加輕載即可喚醒 (2)低電流寄生負載,Vcell>3.1. 按一次觸彈開關即可喚醒。
6.低壓啟動保留電能模式(LVSER, Low Voltage Start-up Energy Reserve)觸發和解除:
消耗電流(<8A),致電壓低於3.1V時，進入省電休眠;以按壓喚醒開關並在300秒內啟動或充電達>3.1V來喚醒。
7. 休眠Sleep-Mode或LVSER Self-disable) 自動解除: 任何>2.4V且電流消耗大於 >10A。休眠或LVSER 自動解除.
8. 反電動勢電路裝置(對BMS 的保護)。

Specification​

Features:
1. Rated continuous discharge current: 110A, instantaneous maximum 2000A <10mS
2. Gradient Current Management: Control the discharge protection time according to the size of the extracted current.
3. High current tolerance: load short-circuit protection current is 2000A, delay ≤ 10ms.
4Floating shunt voltage balance: Floating shunt balance, the shunt value is automatically adjusted according to the cell differential pressure, and the balancing capacity is 300mA ( reference specification).
5. Automatic sleep and wake-up function (Shutdown-Sleep & Wake up by Self-Recognition): Automatically enter sleep mode with zero power consumption
(1) No load. It can be awakened by charging or adding light load. (2) Low current parasitic load, Vcell>3.1. It can be awakened by pressing the trigger switch once.
6. Triggering and releasing the low voltage start-up energy reserve mode (LVSER, Low Voltage Start-up Energy Reserve):
When the current consumption is less than 8A and the voltage is lower than 3.1V, it enters power saving sleep mode. It can be awakened by pressing the wake-up switch and starting within 300 seconds or charging to >3.1V.
7. Sleep-Mode or LVSER Self-disable) automatically released: Any >2.4V and current consumption greater than >10A. Sleep or LVSER automatically released.
8. Back electromotive force circuit device (for BMS protection) .


規格:
Specification:

產品圖:

尺寸圖:

配線圖:

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[amberwolf]

It shows they have an english version of the site but everything I click there shows page not found. Eventually I looked at the source of hte page in the browser and followed every link in the page and that led me to the *actual* pages, you have to click the 1 in a circle before it gives you valid links.

So here's the english version of the page above, as their site has it (no translation).

::::: 春豆科技股份有限公司 SOONTOP TECHNOLOGY CO., LTD.:::::

春豆科技股份有限公司 SOONTOP TECHNOLOGY CO., LTD

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3. Car Cranking Battery BMS
4. 24V 8S LiFePO4 Engine Starter Battery BMS

24V 8S LiFePO4 Engine Starter Battery BMS​

1. 8S 24V LiFePO4 BMS.
2. Max continuous discharge current up to 110A, and available for those higher than 110A.
3. Gradient Current Management Method manages current drains.
4. High current durability with short-circuit protection greater than 2000A .
5. Floating shunt current mode shunts cell input current by different scales.
6. Mosfet grouped for managing in current surges.
7. Low Voltage Start Energy Reserve (LVSER): LVSER mode acts at cell volt dropping down to 2.90V, to break off lower current drains and slow down capacity loss, which is not involved with driving or igniting. The LVSER Mode is energy-saving mode to maintain margin capacity to start up the car again at its low voltage, LVSER Volt will keep dropping from 2.90V until 2.4V with load, or stay at 2.9V,while via an external switch.
8. No load Sleep Mode starts with no current consumption.

SB-78-24-110 24V110A Car Starter BMS​

Read More

SB78o-F-24-110 24V110A Car Starter BMS​

SB-78-24-110 24V110A Car Starter BMS​

Category：​

24V 8S LiFePO4 Engine Starter Battery BMS

Description：​

Specification​

Feature:

1. Continuous discharge current specifically designed for a car alternator use: 110A
2. Max discharge current: Peak current 900A, with delay time for 10Ms.
3. Floating Battery Balancer: smart cell balancer starts at/ over 3.50V, but it acts only on cells with volt variances, higher by 40mV than the lowest one. The bleeding current dissipates by from 40mA to 300mA,
4. Mosfet Management: Sense circuit designed for a purpose to keeping Mosfets from all being burnt down..
5. Sleep Mode with no current consumption: System shuts, showing 0 volt measured at terminals in 2 onditions, as follows: (1).When a status of no load lasts for 5~22(in default) days and, (2).when it is in UVP status.
6. Low Voltage Start Energy Reserve (LVSER): LVSER Mode acts at cell volt dropping down to 2.90V, to break off lower current drains and slow down storage loss, which is not involved with driving or igniting.The LVSER Mode maintains margin storage to start car engine again at its low voltage. LVSER Volt will keep dropping, with parasitic load in car, from 2.90V till 2.4V, or to the volts when it goes to sleep mode, whichever first.
7. LVSER Disable: LVSER function will self-disable once when car alternator fails to supply power to battery.
8. BEMF protection: The BMS has protection for itself conducting back electromotive forces from the car.

Key Specification:

Physical Structure:

Dimension:

Wiring diagram:

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