# My Programable BMS with LCD



## frodus (Apr 12, 2008)

Link would be awesome


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## sunworksco (Sep 8, 2008)

Very impressive!
Can you build a voltage monitor that WiFis to an iPad?
There is a need for EV dashboards.


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## electrodacus (Mar 29, 2014)

frodus said:


> Link would be awesome


Here is the link to kickstarter there are the most info at the moment 
https://www.kickstarter.com/projects/electrodacus/open-source-programmable-solar-bms-development-boa


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## electrodacus (Mar 29, 2014)

sunworksco said:


> Very impressive!
> Can you build a voltage monitor that WiFis to an iPad?
> There is a need for EV dashboards.


Thanks, I can do bluetooth. There is a serial port where that can be easily be connected. I will prefer not to use WiFi since it uses way more power and I tri to keep this ultra efficient so it can stay on all the time.
I know in EV this is not so important with huge battery bank and usually power off when not in use. But in solar applications it will be on all the time.


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## sunworksco (Sep 8, 2008)

Thanks!
Bluetooth is fine.
I am in no way an electronics engineer. How would I install this to use the iPad dashboard?
Can I mount your unit next to my battery pack?
I will stay in touch.


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## Zak650 (Sep 20, 2008)

This needs to be able to do 16 cells or be able to stack 2 in series.


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## electrodacus (Mar 29, 2014)

Zak650 said:


> This needs to be able to do 16 cells or be able to stack 2 in series.


The IC that I used can handle 8 cells it was what I needed but it has an option to stack two of them for max 16 cells.
I have the intention in the near future to build a low speed vehicle but it will use hub motors and will run at 24V so personaly I do not need 16 cells but I know a lot of people need 16 or more cells in series. I think anting over 16 cells will do better with individual BMS on each cell that communicate in a one wire or two wire serial interface.
This was designed specifically to replace the very common 12 and 24V Lead Acid solar chargers for those that want to use lithium.
Most do not realise that Lithium batteries are less expensive than Lead for energy storage.


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## major (Apr 4, 2008)

electrodacus said:


> The IC that I used can handle 8 cells it was what I needed but it has an option to stack two of them for max 16 cells.
> I have the intention in the near future to build a low speed vehicle but it will use hub motors and will run at 24V so personaly I do not need 16 cells but I know a lot of people need 16 or more cells in series. I think anting over 16 cells will do better with individual BMS on each cell that communicate in a one wire or two wire serial interface.
> This was designed specifically to replace the very common 12 and 24V Lead Acid solar chargers for those that want to use lithium.
> Most do not realise that Lithium batteries are less expensive than Lead for energy storage.


There is a huge market for 48V batteries or modules. A BMS that can't handle 12 or 14S is missing a big opportunity. Like those EnerDel 12S modules which come with the cell voltage sense/balance distribution and thermistor harness. Take a look at telecom, standy-by power, UPS and even utility scale modules. All 48V. Most OEM EV batteries are comprised of 48V modules. Few have cell level BMS. 

I wonder why solar hasn't gone to 48


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## electrodacus (Mar 29, 2014)

major said:


> There is a huge market for 48V batteries or modules. A BMS that can't handle 12 or 14S is missing a big opportunity. Like those EnerDel 12S modules which come with the cell voltage sense/balance distribution and thermistor harness. Take a look at telecom, standy-by power, UPS and even utility scale modules. All 48V. Most OEM EV batteries are comprised of 48V modules. Few have cell level BMS.
> 
> I wonder why solar hasn't gone to 48


It depends on the power requirement there are 48V solar setups and even larger.
But for small solar setups up to about 2000 to 3000W load, 12V and 24V is more convenient since there are a lot of devices that work directly at 12 or 24V but less that work on 48V.
It will not be that hard to modify this for 48V maybe around two months to change the PCB's and adjust the software but it will get more expensive since it needs larger PCB's higher voltage mosfet's and an additional BMS IC it will not be double but at least 50% more.
Also for 48V compatibility with Lead Acid you will only need 14 LiCoO2 cells for LiFePO4 you will need 16 cells.


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## PStechPaul (May 1, 2012)

I know this is an old thread but I saw your posts in the bottom/top balancing thread and then found this one. I am also interested in developing a BMS and my latest concept uses an analog MUX like a DG408 which has a maximum voltage of 44V. This should be fine for 8 lithium cells and the design can accommodate multiple modules in series and not all 8 switches need to be used. A DG409 has 4 two-channel differential switches that might be useful. 

It would be good to have a single BMS module that could handle 4 12V lead-acid batteries, nominally 48V, and maximum 60V. I intend to build a small electric tractor which may run on two, three, or four deep cycle or SLA batteries, where this would be useful. I'll have to look a bit more at your design and see if I can learn anything more to incorporate in what I'm doing. This is a somewhat low priority for me ATM and my main effort will probably be on a modular charger design, but a BMS would be a necessary part of the overall system.


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## electrodacus (Mar 29, 2014)

PStechPaul said:


> I know this is an old thread but I saw your posts in the bottom/top balancing thread and then found this one. I am also interested in developing a BMS and my latest concept uses an analog MUX like a DG408 which has a maximum voltage of 44V. This should be fine for 8 lithium cells and the design can accommodate multiple modules in series and not all 8 switches need to be used. A DG409 has 4 two-channel differential switches that might be useful.
> 
> It would be good to have a single BMS module that could handle 4 12V lead-acid batteries, nominally 48V, and maximum 60V. I intend to build a small electric tractor which may run on two, three, or four deep cycle or SLA batteries, where this would be useful. I'll have to look a bit more at your design and see if I can learn anything more to incorporate in what I'm doing. This is a somewhat low priority for me ATM and my main effort will probably be on a modular charger design, but a BMS would be a necessary part of the overall system.


An electric tractor will be cool. I was looking in to those things and will build a sort of an electric tractor when I will get the time but it will be smaller with remote control I do not want to sit on to a tractor and break my back 
In fact mine will be more like a skid steer loader but electric and able to take different attachments.
Anyway I do not think Lead Acid will benefit from a BMS in the same way as Lithium so if you are going to use Lead Acid then I do not see why will you invest the time and effort in to a BMS.
For a tractor weight is not a problem it can be a good thing so the aditional weight of Lead battery is not a problem and since it will not be used that much maybe the life cycle is also not a problem.
The Lead Acid batteries will auto-balance when you go to equalization phase.
With 12V batteries you have 6 cells of 2V already in a box with no access to individual cells so it will be like trying to have a BMS for Lithium that only checked the voltage only on groups of 4 cells in series and that will not protect in any way Lithium.
I'm guessing you just want to monitor batteries since they will be under high discharge rate and see if none will go to low you probably can't do anything else.
You also do not need high resolution voltage measurement so a small microcontroller with a 10 or 12bit ADC can measure directly just using some voltage dividers the voltage on the 4 individual batteries.
The ISL94203 that I use will be a total overkill for your project and is not easy to use as a one time project DIY soldering since is a 0.4mm pin pitch QFN package.


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## PStechPaul (May 1, 2012)

The tractor(s) are mostly demonstration projects, although I do hope to get some use out of them to haul firewood and mow the lawn. I'd also like to add a FEL, and the larger tractor (a 1967 vintage Simplicity Broadmoor) also has a dozing plow, which may be handy. They will use lead-acid, because of the lower initial cost, low cycle requirements, and beneficial weight.

I figure I might as well design the BMS and charger so that it can work for that application as well as lithium cells. I am also replacing the NiCad batteries in a Ryobi drill with some (6) 18650 LiFePO4 cells, and the BMS will be needed for that. 

For EVs in general, my ultimate concept is a modular system with self-contained cells (48 volts or less), a DC-DC converter to obtain 120-150, 240-300, or 360-450 VDC to supply the DC link bus of a VFD. The outputs can be connected in series or parallel for greater capacity, and they would be in the order of 2-5 kWh each. This provides redundancy as well as an easy upgrade path to add more capacity.

The modules would incorporate protective circuitry and interlocks so that the high voltage output would not be present unless an external signal were applied, and the 48V DC would be the maximum present in the vehicle in case of accident, reducing the risk of high voltage from series of cells up to 300 VDC or more. The 48 VDC maximum in the modules (or provided by external connection) can be handled with smaller contactors and less expensive fuses.


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## electrodacus (Mar 29, 2014)

PStechPaul said:


> The tractor(s) are mostly demonstration projects, although I do hope to get some use out of them to haul firewood and mow the lawn. I'd also like to add a FEL, and the larger tractor (a 1967 vintage Simplicity Broadmoor) also has a dozing plow, which may be handy. They will use lead-acid, because of the lower initial cost, low cycle requirements, and beneficial weight.
> 
> I figure I might as well design the BMS and charger so that it can work for that application as well as lithium cells. I am also replacing the NiCad batteries in a Ryobi drill with some (6) 18650 LiFePO4 cells, and the BMS will be needed for that.
> 
> ...


You can buy 1.2kWh 48V LiFePO4 modules from Sony http://download.solarshop.net/english/uploads/FS-UK-Sony-Storage-system-data-sheet-10-08-2012.pdf
Is quite close to what you want.
Maybe you seen the link to this on my website not sure. They are a bit expensive but for sure high quality cells.


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