# Experience with the SIMP BMS (for Tesla modules)



## reiderM (Dec 30, 2020)

Has anyone used the Simp BMS for Tesla modules? It seems like an interesting option since it reuses the individual balance boards on each module, which makes the wiring simpler and makes it cheaper than a full BMS like the Orion.


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## 4Foxtrot (Apr 1, 2019)

YES - I use it and its brilliant ! > Tesla BMS and its maker @Tomdb is on here
The main benefit is it uses the existing Tesla BMS boards and bleed resistors in each module. Which makes more sense to me than ripping them all out and starting again with say an orion.


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## reiderM (Dec 30, 2020)

Nice! I remember your project with the Hyper 9 and Tesla modules --- looks like a sweet ride!

Yes I also like the idea of just keeping the OEM BMS boards that are certainly very well-built.

How difficult was it to set up? 

Orion is definitely pretty easy to use, and that's one thing that makes it nice.


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## 4Foxtrot (Apr 1, 2019)

Dead easy to set up, physically especially IF YOU keep the tesla module data cables. 

I found software setup OK see Manual > Tom-evnut/SimpBMS
You just need Termite 3.4 (by Compuphase) on the PC and a USB link to simpBMS. the manual is OK, but might need to read a few times.


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## reiderM (Dec 30, 2020)

Thank you so much!

How about features? Specifically charge limits and SoC metering. I've seen a small screen that can be bought with the Simp BMS, wondering if you used that.


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## 4Foxtrot (Apr 1, 2019)

reiderM said:


> Thank you so much!
> 
> How about features? Specifically charge limits and SoC metering. I've seen a small screen that can be bought with the Simp BMS, wondering if you used that.


 yes all there, can set charge limits (and all relevant settings) and can see SOC and even individual module details on the optional little touch screen > enjoy a good read > Tom-evnut/SimpBMS


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## justdave2 (Mar 3, 2019)

Another vote for SimpBMS !

Carel Hassink of the team was super helpful, and the product is well designed. Regular updates as well.

I would say the product is not for the non-technical. You do need to read the manual and understand the settings. You will be building wiring harnesses and hooking up contactor relays and building a lot of your solution. The "brains" that take the measurements and open/closes circuits based on BMS logic is what SimpBMS gives you.


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## drdhdmd (Aug 5, 2007)

I use the SimpBMS in TeD, my Tesla battery powered eLectric DeLorean. It seems to work very well and I am using their optional touch screen display. It certainly makes sense to me to use the Tesla BMS.


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## DomT177 (Sep 20, 2020)

Does it calculate maximum charge and discharge rate, so will it limit the current allowed into and out of the battery?


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## Classic Style (Nov 28, 2020)

So, I'm planning to pull the trigger for SimpBMS on Monday, but I'm hoping I can get a few questions answered by those with experience...
1. Is there a US reseller? If so, who?
2. Anyone connect it to StealthEVs 6.6KW charger before? If so, how difficult was setup?
3. How necessary is the touch screen? Is there a USB<>PC configuration interface used instead of the touch screen? I'm comfortable with programming on Teensy boards, just unsure of what the alternate solution is.
4. Same question for the current meter?

I've read through the SimpBMS manual quite a bit, but I'm not sure I understand everything, so I'm assuming I'll need to actually have it in hand and be wiring it up for everything to make sense... Maybe? I'm a learn-by-doing kind of guy, so reading a manual in advance doesn't help me very much.  

For reference, here's my general components in my 944EV:

85 KWH Tesla Model S battery setup
Model S LDU
No VCU or Inverter Board chosen yet
Planning on SimpBMS
Planning on this Stealth EV charger & DC/DC converter

PFA (yes, my workshop is an utter mess)


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## drdhdmd (Aug 5, 2007)

As far as I know, it does not. The only control of charging current is that it can turn on or off the power to the charger based on pack voltage. If you wanted to control the charge or discharge current of the battery you would need some BIG semiconductor in series that could handle the current. Something like 1000 amps max.


Classic Style said:


> So, I'm planning to pull the trigger for SimpBMS on Monday, but I'm hoping I can get a few questions answered by those with experience...
> 1. Is there a US reseller? If so, who?
> 2. Anyone connect it to StealthEVs 6.6KW charger before? If so, how difficult was setup?
> 3. How necessary is the touch screen? Is there a USB<>PC configuration interface used instead of the touch screen? I'm comfortable with programming on Teensy boards, just unsure of what the alternate solution is.
> ...


1. No US reseller that I know of. My order came to New Jersey within a week

3. I find the touch screen very useful for monitoring the system, ie. pack voltage, highest cell, lowest cell, cell temperatures, % Charge, charge / discharge current etc.
(Though I am having difficulty withe the accuracy of the current measurements)

It uses an Arduino type of controller and has a micro USB connector. You interface with it by using a "serial terminal" on your PC, laptop, pad, or phone.

4. The "current meter" uses an "active" current sensor and has two ranges. I am having calibration /stability /accuracy issues.

SimpBMS is based on an open source program so it is customizable by those who have the expertise... not me yet. 

I would like to be able to display temperatures in Fahrenheit. Change some of the outputs to turn on I icator lights for say, low voltage limit, high voltage limit, etc.


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## Classic Style (Nov 28, 2020)

drdhdmd said:


> As far as I know, it does not. The only control of charging current is that it can turn on or off the power to the charger based on pack voltage. If you wanted to control the charge or discharge current of the battery you would need some BIG semiconductor in series that could handle the current. Something like 1000 amps max.
> 
> 1. No US reseller that I know of. My order came to New Jersey within a week
> 
> ...


This has been helpful, thank you! Would you say the value price of the unit has outweighed any difficulties you've had with it compared to something like Orion? Also I'm a little confused by what you're answering in your opening statement... Is that regarding the current sensor or the charger from StealthEV?


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## Swing (Apr 25, 2021)

I am not sure what he means by that. But as you can see in the menu, it can control the big relays for charging/discharging and precharge with a configurable timer.

And you can do the configuration via terminal over the USB connection.


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## Classic Style (Nov 28, 2020)

Swing said:


> I am not sure what he means by that. But as you can see in the menu, it can control the big relays for charging/discharging and precharge with a configurable timer.
> 
> And you can do the configuration via terminal over the USB connection.


Thank you for the info. I was hoping what you said was the case. 

In looking at the overview doc for Simp, it looks like they're suggesting a huge contactor for the precharge resistor. Does it need anything that significant, or can any low-current/HV relay work? I imagine the resistor isn't that crazy for it's current need but I haven't measured it's resistance to figure it out yet.


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## Swing (Apr 25, 2021)

I don't remember the documentation and don't want to look it up now, but I think the best choice for these projects are reused EV relays.
I am using one from a Mitsubishi Outlander PHEV.
They are typically rated to 400V and enough amps, and are operated with 12v by the SimpBMS. And they are available seperately, or 3 combined in one, giving you also a precharge route if you want it (which you want in an EV, in my offgrid install I am not using it)


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## alexbeatle (Jul 28, 2020)

In the manual, it says that Tesla slave boards are baud rate programmable!?!? How do you set the slave boards to talk on desired rate? Can it run at 250k baud rate? 

SimpBMS has only one CAN interface and all of other components I've selected have only 250k as common rate.


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## reiderM (Dec 30, 2020)

alexbeatle said:


> In the manual, it says that Tesla slave boards are baud rate programmable!?!? How do you set the slave boards to talk on desired rate? Can it run at 250k baud rate?
> 
> SimpBMS has only one CAN interface and all of other components I've selected have only 250k as common rate.


I believe the Tesla slave boards run on an entirely separate CAN network than the accessory CAN network. 

When it says the Tesla slave boards can communicate on a programmable baud rate, I believe this means that the boards will work at any baud rate. All you need to do is change the baud rate in the configuration settings for the SimpBMS.


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## alexbeatle (Jul 28, 2020)

reiderM said:


> I believe the Tesla slave boards run on an entirely separate CAN network than the accessory CAN network.
> 
> When it says the Tesla slave boards can communicate on a programmable baud rate, I believe this means that the boards will work at any baud rate. All you need to do is change the baud rate in the configuration settings for the SimpBMS.


I see. But simpbms has only one CAN interface, how do you interface it with the slave modules and the other accessories then?


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## Classic Style (Nov 28, 2020)

alexbeatle said:


> I see. But simpbms has only one CAN interface, how do you interface it with the slave modules and the other accessories then?


SimpBMS has a can interface on the BMS plug, and it has a can interface on the main (I think it's J4?) plug. The wiring diagram in the manual shows it.


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## reiderM (Dec 30, 2020)

Also a CAN interface for CAN-enabled current sensors! CANbus everywhere!


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## Foxe Electric Mustang (9 mo ago)

drdhdmd said:


> As far as I know, it does not. The only control of charging current is that it can turn on or off the power to the charger based on pack voltage. If you wanted to control the charge or discharge current of the battery you would need some BIG semiconductor in series that could handle the current. Something like 1000 amps max.
> 
> 1. No US reseller that I know of. My order came to New Jersey within a week
> 
> ...


I see you mentioned you are in New Jersey and so am I. I am currently working on an electric car conversion. Would you be available for a phone call? I have a few questions and hoping you may be able to help!
Send me an email if you don't mind [email protected]


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## rawsuber (6 mo ago)

Thank you for all of the info folks. Very helpful. Does anyone know how to access the source code? I would like to flip the display so the cord is on the right side when the screen is displayed. If that makes sense. It will fit in a cutout on the dash where the old quarts digital clock was displayed, which would be pretty clean.... I tried the github link but it appears to be broken.


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## reiderM (Dec 30, 2020)

Try this one:









GitHub - Tom-evnut/SimpDisplay: A Nextion Display to work with the SimpBMS


A Nextion Display to work with the SimpBMS. Contribute to Tom-evnut/SimpDisplay development by creating an account on GitHub.




github.com





There a rotated .TFT file that you can try.


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## rawsuber (6 mo ago)

reiderM said:


> Try this one:
> 
> 
> 
> ...


Perfect. Thank you!


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