OSBMS - A scalable, low cost, and full featured BMS

Batteries, Chargers, and Battery Management Systems.
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Alan B
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Re: OSBMS - A scalable, low cost, and full featured BMS

Post by Alan B » May 17, 2017 11:24 am

Maybe not. Here's my old thread which starts out that way, then transitions to the Intersil. I'm not against the many small micro approach at all.

https://endless-sphere.com/forums/viewt ... 14&t=25706

I did go through the datasheet, make a design and fabricate 3 PC boards for the Intersil. Never got to testing one.

The micro approach is interesting but drives the parts count and cost up, however availability is solved.

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methods
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Re: OSBMS - A scalable, low cost, and full featured BMS

Post by methods » May 17, 2017 12:41 pm

Ah man... you beat me to it. :(
I admit that I did not search.

Only read the first page... but as to parts count and power (you may have found this)

The Attiny let you run down to 1.8V and 1Mhz for super low power
Keeping the oscillator internal drops three parts at the cost of some power
I was considering dumping shunt heat across the resistor, regulator, and the chip... by using an IO leg
Interesting that you did a Resistor Zener for the supply. I was just grinding my mind looking for an LDO that would give good Q current, run down below 2V, low dropout...

Ok.
I just took a drive with the ol'lady and was considering parts count and cost... I said on the way back that I may need to pivot.
My parts count is already 10 parts per channel ... x 12 = 120!! parts

Since this has already been done I am going to pivot back to a Linear chip.
I will try to make it lower parts count this time by using resistor, capacitor, and Zener arrays - layout becomes wicked hell... but population goes much faster

Sigh... LTC6802... 6803... 6804... and beyond.
Here we go again.

I lost all my original layout files and source... but luckly I shared the source with a friend in the UK so I think I can at least get my state machine back.
This time around instead of sampling at like... 20ms... I am going to go SUPER SLOW.
BMS is only going to act once every 500mS (it works... do the math...) and get the power way down.

K - thanks for the kick in the butt.

-methods
"One test is worth a thousand opinions"

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Alan B
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Re: OSBMS - A scalable, low cost, and full featured BMS

Post by Alan B » May 17, 2017 2:17 pm

Good luck, these BMS designs always seem to get more complicated and costly than they should.

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methods
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Re: OSBMS - A scalable, low cost, and full featured BMS

Post by methods » May 17, 2017 3:59 pm

Going for it....
https://endless-sphere.com/forums/viewt ... 8#p1288949

Tho I will of course lay the pads for the single pole input filter and DNP (learned that lesson long ago)
I will parallel the resistors with a "shorting pad" and open that aperture up a bit on my VueGraph (solder paste sheet).
Result should be a circuit I can test with 12 less parts to solder.

Respect to Sparkfun for the idea:
battery-jumper.jpg

Be great to use the LPF resistor for heat dissipation... oh well.

The Linear Tech manual on page XX of XXX indicates that one may want to drop the LPF, R, to 10ohms or below as it is in the path of passive balance.
I believe 0ohms is below.... and they have quite a bit of filtering inside.

One test is worth a thousand opinions.

Plan B will involve Resistor and Capacitor arrays, or an all-on-one if I can find it.

-methods
"One test is worth a thousand opinions"

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Re: OSBMS - A scalable, low cost, and full featured BMS

Post by alec » Dec 07, 2017 1:30 pm

methods wrote:
May 17, 2017 3:59 pm
Going for it....
https://endless-sphere.com/forums/viewt ... 8#p1288949

Tho I will of course lay the pads for the single pole input filter and DNP (learned that lesson long ago)
I will parallel the resistors with a "shorting pad" and open that aperture up a bit on my VueGraph (solder paste sheet).
Result should be a circuit I can test with 12 less parts to solder.

Respect to Sparkfun for the idea:
battery-jumper.jpg


Be great to use the LPF resistor for heat dissipation... oh well.

The Linear Tech manual on page XX of XXX indicates that one may want to drop the LPF, R, to 10ohms or below as it is in the path of passive balance.
I believe 0ohms is below.... and they have quite a bit of filtering inside.

One test is worth a thousand opinions.

Plan B will involve Resistor and Capacitor arrays, or an all-on-one if I can find it.

-methods
Any update on your project?
"Black Widow" Greyborg [v.2] | Cromotor [v.3] | Greentime 1440 | 24s EIG cells 12kW peak (thread coming soon)
Project(s) in works: FatCON (& DIY Serial/USB to Bluetooth)

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