On Going Deals on Batteries.

20 hours ago, dochubert said:

I definitely want 16 of the lcd version for lifepo4 as soon as they are available.  I have some heatsinks already that should work, and will probably use more than one fan.  Also thinking of removing the heatsinks and fans from the soon to arrive byd modules as my existing byd's don't have heatsinks and don't even get warm.  Once I double the bank size current draw per module should be too low to produce any significant battery heat.  One or two of those heatsinks would probably do it for 16 balancer modules with one or two fans per heatsink. 

Can I order the balancers now?

Umm.......waiting a smidge for a bit of income so I can order them 😉........THEN we can sell them.  A batch order is in the PCB manufacturer's shopping cart right now.

Ok.  Ready when you are. Thanks.

Oy, I've been a busy boy.  I just made a Raspberry Pie 400 use a usb audio device, then got it to start talking.  took me 5 hours to learn how to use SSH and to find all the info to get audio to work since stupid hdmi audio stinks.  Now off learning python and I got a set of servos coming and a bread board, as well as some relay to fool around with.  Going to learn to controlle things with programming now 😛

Anyhow, Hey sid, those balancer that got the ports on them, are the cam based or what?  What do I need to study up on so when I get them I ahead of the game.

18 hours ago, The Blind Wolf said:

Anyhow, Hey sid, those balancer that got the ports on them, are the cam based or what?  What do I need to study up on so when I get them I ahead of the game.

RS-232 (i.e. UART)...only TX output (no bidirectional communication).  I don't have any particular standard in mind, unless someone wants to suggest something??

Currently, the plan is that each unit will append it's data (cell voltage, current status) to the end of the string it receives (as well as an updated checksum).  This makes battery string size a completely irrelevant statistic--doesn't matter what size battery bank you have.

So all I need to worry about is a tx wire pulling the info off of the balancer?  Sounds simple being one wire. well, unless I need to provide a negative wire.  Will look up the specs on that connetor.  Still fooling around with my rp, got the servos in today and the controller, looking up what pin is for what and all the fun stuff.

Hi Sid,

Sean's videos suggested battery type was selected by a solder pad.  True?

Also wondering if the activation voltage (when it starts bleeding power) was adjustable.

Thanks

Far as I remeber no, the voltage is set to either 3.55 or 4.15 I think for either battery.

Yes.  Solder jumper.

Technically no...though if you fancy SMD rework, you can adjust the voltage divider yourself.  The circuit is not capable of functioning below 3.0vDC (so no LTO batteries)...though I probably will look into making a slightly revised version for LTO (likely without the little MCU, and definitely without the LCD--as it won't function below 3v).

It's currently set to 3.55v / 4.15v...I didn't set it to 3.6 / 4.2v, because of 2 reasons:

• maintaining a 100% SOC reportedly degrades battery life a lot faster than a slightly lower SOC
• if you're running 5A balance current, there's going to be more than 0.05v drop in the wires between the batteries and the balancers--so the cells will go into overvoltage anyway.

It's easy to see you put a lot of thought into these things, Sid.

I'm betting you won't recommend this, but what would happen if I leave either a bms or an active balancer also connected in parallel with your balancers.  Extra protection?  Or will they fight each other?  Or maybe no difference?

I'm interested to hear your thoughts.

On the original topic, Battery clearing house is now showing sold out on the BYD modules I just purchased (linked above)

1 hour ago, dochubert said:

It's easy to see you put a lot of thought into these things, Sid.

I'm betting you won't recommend this, but what would happen if I leave either a bms or an active balancer also connected in parallel with your balancers.  Extra protection?  Or will they fight each other?  Or maybe no difference?

I'm interested to hear your thoughts.

Actually that's not a bad idea.  The GS balance shunts will only activate if the cell voltage exceeds the setpoint--below that, an "energy distributing" active balancer can still function as it was designed to.

Alternatively, you could consider using one of the chintzy 30mA Chinese BMS units for monitoring/disconnect, and the GS balance shunts do the heavy lifting.

Hey!  I got one right!  That's actually where my thoughts were going.

On 3/23/2021 at 6:41 PM, Sid Genetry Solar said:

RS-232 (i.e. UART)...only TX output (no bidirectional communication).  I don't have any particular standard in mind, unless someone wants to suggest something??

Currently, the plan is that each unit will append it's data (cell voltage, current status) to the end of the string it receives (as well as an updated checksum).  This makes battery string size a completely irrelevant statistic--doesn't matter what size battery bank you have.

If you can, consider sending single line JSON objects. It makes it much easier to consume.

Didn't think of that...but it would definitely make a huge increase in the data transmission.

Each balancer will have the following info available:

• firmware version
• ID number (1 = top of string)
• battery voltage
• shunt state
  • on
  • off
  • MAYBE a crude "throttle"
  • balancer fail?
• thermal protection state (good/trip)
• local temp (MAYBE)

If you stringify all of that with JSON, I'll casually estimate over 100 bytes of data per balancer (as a result of adding all the JSON support stuff).  If we support up to 200 cells in series, that becomes 20,000 bytes of data to transmit...and if we're doing a 5 second "update" interval, that requires a MINIMUM baud rate of 57,600. 

Possible?  Well, the little PICs would have to bump out of 32KHz power save mode to 8MHz to meet the UART requirements--bumping static current consumption from <0.5mA to ~5mA each.

Worth it?  I wonder...'cause parsing a bazillion bytes with a casual Arduino project turns into quite the challenge.  Now, if it's connected to a Raspberry Pi (or other embedded processor) with 512MB of RAM and a 1GHz processor, JSON is child's play.

If it's transmitted in direct byte format, we save a considerable amount of data:

1. "header" byte (0xFF)? --might be able to indicate firmware version on low nibble?
2. cell ID byte (1 = positive end of the string)
3. battery voltage HI [may be able to pack a couple of bitflags on the MSB here]
4. battery voltage LO
5. shunt state bits (7: "fail", 6-0: "throttle" [if possible])
6. local temperature (MAYBE...definitely low resolution at best)
7. status bitflags (incl. thermal protection state)
8. checksum

8 bytes * 200 balancers = 1,600 bytes / 5 second update interval = 320 bytes/second = 4,800 baud is more than adequate.  9,600 is very common, and can easily be handled with the processors running at 0.5MHz internal oscillator.

Thoughts?

What ever is easier.  😛  I have Raspberry pie, and tomorrow will have a 3d printer 😛 and a bunch of stuff for my RP to play with the gpio stuff.

Hey sid, is there a place on the balancer that act like a switch by chance?  so I can place a relay on it to actvate a fan when the balaner kicks on?  Going to fool around but, once I get a balancer going to 3d print a houseing with theheat sink and a fan shroud directed onto the heat sink.