INR 18650 - 25R without BMS ??

Cherry67

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Hi to all,
Yesterday i obtained two powertool Blocks, one from Bosch, the other one obviously the same construction.

One is 36 V, 10s2p, 36 V.

The other one is labeled 72 V, but contains two electrially isolated strings of 10s1p. (of 36 V)
Cell Type is as said: INR 18650-25R.

And the surprise of the day - no BMS in either of the two. Yes, there are fuses per string, but NO BMS.

Any idea if that is a major failure of professional production, or do i overlook something ?

I assume the latter. But what ?
 

jdeadman

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BMS might be in the Charger and come simple cutoff in the tool
 

Cherry67

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Uhm, sorry, i was inaccurate.

NO Balancing. Nothing. Nada.
 

Korishan

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Bosch has been putting the BMS inside the powertool itself, not the battery pack. I suppose this drastically reduces the cost of manufacturing of the battery pack.

How many connectors make contact inside the powertool? If there are 4 or more contacts, then I'd guess that's where the bms is.
 

Cherry67

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Korishan said:
Bosch has been putting the BMS inside the powertool itself, not the battery pack. I suppose this drastically reduces the cost of manufacturing of the battery pack.

How many connectors make contact inside the powertool? If there are 4 or more contacts, then I'd guess that's where the bms is.
Tscha, you dont believe me.
That answers half of my question.
For the other half, i have to make you believe.

Here we go:


image_oermkx.jpg


One side of the Board in the block.


image_pychzf.jpg


The other side.


image_pijnrf.jpg


THis is the "Middle" of the final block, opened.


image_qpmcbi.jpg


One end of the Block.


image_xzqyft.jpg


The other end.

Where are the wires to all the stages of the 10 s? There are two separate 10s1p strings, makes 18 necessary wires.

If there are no such wires, then there is no balancing of the cells, whereverer the BMS should be installed.



Bosch does only check total voltage and current. No balancing.

What do you say now ? :D
 

Korishan

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I didn't say I didn't believe you. Just because the "pack" doesn't have the balancing hardware doesn't mean there isn't any. When you said no bms in the pack, I was thinking that there were at least some extra wires but no circuitry.

However, in this case, the only "smarts" the unit has is over-current protection. That's what the two large current shunts are for.

This pack "almost" looks like a knockoff and not a legit pack. But, the cells make a counter to that thinking. Definitely an oddity. Unless Bosch has come the thinking that if they select the right cell chemistry/manufacturer that they don't need a balancer anymore.

What's the numbers on the IC? That should lead us to what kind of circuitry this is and what they were thinking (maybe) about the design
 

Cherry67

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Korishan said:
I didn't say I didn't believe you. Just because the "pack" doesn't have the balancing hardware doesn't mean there isn't any. When you said no bms in the pack, I was thinking that there were at least some extra wires but no circuitry.

However, in this case, the only "smarts" the unit has is over-current protection. That's what the two large current shunts are for.

This pack "almost" looks like a knockoff and not a legit pack. But, the cells make a counter to that thinking. Definitely an oddity. Unless Bosch has come the thinking that if they select the right cell chemistry/manufacturer that they don't need a balancer anymore.

What's the numbers on the IC? That should lead us to what kind of circuitry this is and what they were thinking (maybe) about the design
Ah, you shouldhave known i am able to recognize data communication and serial lines (Chuckle). Dont worry.
The large shunts are fuses. Melting fuses.

Sure it is original.

I look for the IC, but its circuitry for the Filling led of the pack, i guess.

I would fully agree, an oddity.
I was afraid i did overlook something. like a protection iside of the cell or such.
 

Cherry67

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Sorry i couldnt itentify the IC, it was covered with adhesive wich fills the laser marking. But i am sure its the LED control, especially because it is close to the LEDs, and its the one and only IC on the whol board.

So as Korishan mentions i have to assume that Bosch has found a method (or believes they have found a method) of operating this kind of cell or this case of usage without balancing circuit and without cell-level OVP/UVP check.

I have seen thunderharts checks, he mentiones the INR as a high current cell. The datasheelt gives values for high currents correlated to less than 200 Cycles... perhaps this cell is different somehow.

Since i have a second Block with 36 V and original charger, i will setup a few tests how it behaves on cell losses and SOC difference of cells.
 
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