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Discussion Starter · #1 ·
Hello friends,
i purchased the Chevrolet S-10 EV from bjnkm2: For Sale, 1997 Chevrolet S10Electric, $8K OBO

After the long shipping of the car, the lead acid battery was completely empty and a few cells did not catch up to a good capacity after recharge. We decided to make a conversion to lithium ion batteries and to use 120ah bmw i3 modules for that. They are a good fit and it's easy to work with them.

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-bottom layer of lead acid batteries

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-empty battery case

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-preparing for swap

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-first layer of bmw i3 modules. The red connectors on the right side are from the bms wires. They are only connecting to resistors, to fool the chevrolet bms into thinking everything is alright. We used the simpBMS from tomdebree to monitor the i3 modules and used an additional contactor for safety reasons. We still use the original magna charger. The chevrolet bms still receives the overall voltage of the bmw modules (and also overall voltage divided by 26 for every original lead acid battery)

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-testing before final installation

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-overall voltage divided by 26

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-S-10 put to work

The truck is now 200kg lighter and is doing 100+ miles per charge. Acceleration improved to 7.2s for 0-50mph. If you have any questions i will try my best to answer them!
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Cool! I'm planning on using a similar amount of batteries for a SUV conversion so I would love to know the full range. When you say 100+, what specifically do you mean?
 

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Discussion Starter · #3 ·
Cool! I'm planning on using a similar amount of batteries for a SUV conversion so I would love to know the full range. When you say 100+, what specifically do you mean?
It's not significant more than 100 miles, maybe 110. You might even get less miles if its a big SUV you are converting. Also the the S-10 appears to be power consuming with the electric heater for the battery pack and cabin. It's also not shutting down completely and draining the battery over time. It feels like its a little bit too much energy which is lost during parking.
 

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This is awesome. Thank you for sharing!

I have similar Samsung SDI Modules that I am trying to install in my S10 EV. I am monitoring them with an Orion BMS.

I have some questions regarding the "Sppofing" of the BPCM.

They are only connecting to resistors, to fool the chevrolet bms into thinking everything is alright.
Can you explain this in more detail? I am trying to replicate it myself :)

It is my understanding that the S10 EV BPCM was set up to track 26 batteries (either PbA @ 12v or NiMH
@ 13.2v) and the total voltage (either PbA @ 312 v or NiMh @ 343v). It also included temperature sensors.

Did you use resistors to spoof the temp sensors? If so, which ones?

How did you divide the voltage of the pack by 26?
 

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I have some questions regarding the "Sppofing" of the BPCM.

Can you explain this in more detail? I am trying to replicate it myself :)
My guess is that he is using resistors to decrease the voltage that the BMS receives from the cells to make the cell voltage readings to line up with the original lead-acid cells. It's a clever solution.
 

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My guess is that he is using resistors to decrease the voltage that the BMS receives from the cells to make the cell voltage readings to line up with the original lead-acid cells. It's a clever solution.
Close but not quite.

The total pack voltage is in line with what the BMS is expecting. There were 26 x 12v modules originally. So he divides the total voltage by 26 to feed it to each battery sensor. This can be done with a voltage divider.

He is also sending in a signal to the temperature sensors on the BMS using resistors it sound like.
 

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Discussion Starter · #7 ·
Hi, sorry for the late reply.

Did you use resistors to spoof the temp sensors? If so, which ones?
I made a row of small pcbs with smd resistors and connectors. I think i used 4.7k resistors. You can also use higher resistance values.
Here is a picture of the pcbs.


Next time i would create one small pcb with one suitable connector that can handle the voltage.

He is also sending in a signal to the temperature sensors on the BMS using resistors it sound like.
I did not change the temperature sensors. They were just placed somewhere in the battery box and not fixed to cells or something like this.
 

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It's not significant more than 100 miles, maybe 110. You might even get less miles if its a big SUV you are converting. Also the the S-10 appears to be power consuming with the electric heater for the battery pack and cabin. It's also not shutting down completely and draining the battery over time. It feels like its a little bit too much energy which is lost during parking.
Can you tell us how you dealt with the shunt with respect to the voltage divider? Maybe the shunt sense lines are independent. I was thinking of the way the truck checks the balance of upper and lower battery totals. Thank you very much
 

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I am thrilled to see someone is keeping this truck on the road! I enjoyed working on it for over 10 years. I tried to convert to Lithium but couldn't figure out a BMS that could live with the BPCM. The picture below is what it looked like. I did drive it around the block once but charging was an issue. I think the best improvement I did was the dump bed and the easy access to the battery box. After selling this truck 2 years ago I purchased a 2020 Tesla Model 3 performance. Love it! Good luck with the S10E and if I can help in any way please don't hesitate to get in touch. Just drop the 2 from BJNKM and add at aol. Kevin
 

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I am thrilled to see someone is keeping this truck on the road! I enjoyed working on it for over 10 years. I tried to convert to Lithium but couldn't figure out a BMS that could live with the BPCM. The picture below is what it looked like. I did drive it around the block once but charging was an issue. I think the best improvement I did was the dump bed and the easy access to the battery box. After selling this truck 2 years ago I purchased a 2020 Tesla Model 3 performance. Love it! Good luck with the S10E and if I can help in any way please don't hesitate to get in touch. Just drop the 2 from BJNKM and add at aol. Kevin
Wow, Kevin, thats a nice looking battery box. The resistor string would have worked there too. Big thanks to julwaech for his contribution.

So if you string together 26 4.7k resistors in series like train cars, and you connect each end of the string to B+ and B- on the battery side of the contactors then the 312 v battery will cause .0025 amps to flow through the resistor train. then the battery sense lines can be attached to the connection between each resistor, in order of course from B- to B+. the current flowing through the resistor string will cause 12 volts to be dropped across each resistor. And as the total voltage rises and sags, each sense line will see the same voltage. Now julwaech mentioned that he just spotted the temp thermo resistors throughout the pack as before. Now theres a shunt and a fuse between the upper 13 and lower 13 modules, i'm guessing the sense lines on this shunt stay in place.
Since the BMW i3 modules can handle 4.15V per cell thats 16.6v per original lead module, a voltage that wont surprise the battery pack computer since in leveling this occurs. , so the magnacharger can still be used. So there will always be a 2.5 milliamp draw through the resistor divider all the time . julwaech suggested that higher resistances could be used to minimize this current flow. I dont know if the BMS that he was using is a plug and play with the BMW modules but I'll research it. It looks like BMW i3 battery packs are available on Ebay ranging from 2600 to 3900 dollars. .
 
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