Yet another (?) Smart BMS?

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Yet another (?) Smart BMS?

Post by circuit » Feb 02, 2016 1:37 pm

>> SALES HERE <<

I am actually quite hyped about this. Was waiting for this day for a long time.
You are looking for a perfect BMS, the one you can trust it will not murder your battery, is simple and small enough to use and not outrageously priced? I know the feeling...
So maybe, for some, the wait is over. (No, >16s model is not going to be available for some time)
OK, I know where sell forum is, but this is not for sale, yet.

Image

Now, what this is, is a Smart BMS. It supports 5 to 16 series cells. Features include, but not limited to:

Hardware features
  • Onboard current sensor and switches up to 150A (it goes with aluminum cooling plate)
  • Onboard precharge (for controller capacitors)
  • Optional external industrial current sensor up to 600A; external contactor/relay control
  • Two external and one internal temperature sensor
  • 5V output for bluetooth module supply
  • Universal programmable inputs/outputs (all rated at full battery voltage and 1A):
    • 4x fast digital inputs (for example, to measure RPM/speed)
    • 4x slow digital/analog inputs (for example, to measure voltage of 12V system or additional temperature sensors)
    • 4x fast digital outputs (open drain, for example, contactor, heater, cooler drive)
    • 2x hybrid push-pull outputs in several modes:
      • open drain low side (contactor drive, etc, same as above)
      • open drain high side (for example, controller Vcc drive to avoid contactors and gain unlimited current rating)
      • full push-pull PWM (for example, for 12V contactor drive without 12V system)
      • full switch-mode DAC up to 100mA and full battery voltage range (for example, to charge 12V battery or supply any range of voltages for variable fans or analogue SOC gauges)
  • Onboard status LED and warning/error buzzer
  • Onboard 16 meg FLASH memory (read on)
  • It is just 18650-cell-wide (65mm). Because size matters.
The software
  • Android app, of course (bluetooth)
  • Full flexibility of settings with convenient Windows app (GUI)
  • Open protocol MODBUS communication (for easy integration in to larger systems)
  • Event list with timestamp (charger connected, preheat started, charging started, charging finished, charger disconnected, etc...)
  • Usage statistics (total Ah used, critical disbalance, voltage, current, temperature values, times charged, miles/kilometers driven, etc)
  • Estimation of SoC and remaining charging time or driving distance
  • Bootloader for firmware updates, of course

Current status
It is not quite there yet. But it is just a hair shy of mass production. Final firmware adjustments are being done and hopefully it will be ready soon.
First batch ordered (March 1, 2016)

Why am I posting this?
Well, basically I want to know your opinions about the product and if there are any feature requests. Just please don't say more S, I know this one well. No, it is not stackable at the moment.
Cost. What do you think would be fair enough?
Last edited by circuit on Mar 22, 2016 8:54 am, edited 2 times in total.
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Re: Yet another (?) Smart BMS?

Post by Punx0r » Feb 02, 2016 3:28 pm

Is it a 16S 150A BMS with also a lot of features that you'd normally get on a Cycle Analyst (using phone as display?)? Otherwise, I do not understand what it does :D

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Re: Yet another (?) Smart BMS?

Post by circuit » Feb 03, 2016 12:21 pm

Yes, CA has some of the features.
However, for the price of CA, you can buy this BMS and waterproof android phone and get "free" BMS functionality.
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Re: Yet another (?) Smart BMS?

Post by izeman » Feb 03, 2016 1:10 pm

As you write: for the price of the CA you can.... I would say that's a good range. $100+ is what would be an instant buy for me and i would swap my HCX-D131 for that.

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Re: Yet another (?) Smart BMS?

Post by izeman » Feb 03, 2016 1:12 pm

Being able to ditch the precharge and external shunt would be worth it. I hope the CA can be connected to it and read the shunt value. Unfortunately i see a current sensor that outputs voltage...

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Re: Yet another (?) Smart BMS?

Post by okashira » Feb 03, 2016 1:45 pm

IMHO , most DIY and ebike applications don't need mosfets / isolation.
The controller and charger can handle under voltage and over voltage just fine.
SoC can be determined by voltage, temperature and chemistry, so you can skip the shunt too.
BMS just needs to provide voltage warnings (audible maybe) and perform balancing, smart/adjustable balancing is a must. Not just 4.2V balancing like the crap chinese BMS
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Re: Yet another (?) Smart BMS?

Post by circuit » Feb 03, 2016 1:50 pm

okashira wrote:IMHO , most DIY and ebike applications don't need mosfets / isolation.
The controller and charger can handle under voltage and over voltage just fine.
SoC can be determined by voltage, temperature and chemistry, so you can skip the shunt too.
BMS just needs to provide voltage warnings (audible maybe) and perform balancing, smart/adjustable balancing is a must. Not just 4.2V balancing like the crap chinese BMS
Everyone is allowed to have an opinion. There are many cheap buzzing solutions available. May annual fires as well..
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Re: Yet another (?) Smart BMS?

Post by okashira » Feb 03, 2016 2:08 pm

circuit wrote:
okashira wrote:IMHO , most DIY and ebike applications don't need mosfets / isolation.
The controller and charger can handle under voltage and over voltage just fine.
SoC can be determined by voltage, temperature and chemistry, so you can skip the shunt too.
BMS just needs to provide voltage warnings (audible maybe) and perform balancing, smart/adjustable balancing is a must. Not just 4.2V balancing like the crap chinese BMS
Everyone is allowed to have an opinion. There are many cheap buzzing solutions available. May annual fires as well..
I think you will find a direct correlation with # of fires vs # of cells in pack used from Hobby King.

If you are in a situation where you need to use the BMS mosfet isolation, you did something seriously wrong to begin with.
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Re: Yet another (?) Smart BMS?

Post by okashira » Feb 03, 2016 2:09 pm

I don't see a balance circuit. Are you using an IC with internal balancing circuit?
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Re: Yet another (?) Smart BMS?

Post by circuit » Feb 03, 2016 2:13 pm

Balancing circuit in on bottom side of PCB. 6.2Ω/cell. Which is much more powerful than needed for quality cells.
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Re: Yet another (?) Smart BMS?

Post by agniusm » Feb 03, 2016 2:21 pm

okashira wrote: SoC can be determined by voltage, temperature and chemistry, so you can skip the shunt too.
BMS just needs to provide voltage warnings (audible maybe) and perform balancing, smart/adjustable balancing is a must. Not just 4.2V balancing like the crap chinese BMS
Oh boy, that was plain dumb.
How can you determine accurate SOC other then coulomb method on Li?
I guess he's another cell-log fan.

If it has adjustable LVC, HVC, can be programmed for LiPO or LiFE it should be tits.
Dedicated LCD screen output (whatever protocol) for on-board instruments would be good.

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Re: Yet another (?) Smart BMS?

Post by okashira » Feb 03, 2016 2:22 pm

circuit wrote:Balancing circuit in on bottom side of PCB. 6.2Ω/cell. Which is much more powerful than needed for quality cells.
Yep, even 20 Ohm is plenty if the BMS is smart enough to perform balancing at time other then 4.2V only.
My other problem with MOSFETs is they can fail closed. And they are fragile. And they add resistance. I'd rather just use a fuse.
If you're relying on the MOSFETs turning off in a short circuit condition, the inductance and current can actually cause the mosfets to fail and continue to short. Oftentimes the battery circuit is pretty high inductance
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Re: Yet another (?) Smart BMS?

Post by okashira » Feb 03, 2016 2:25 pm

agniusm wrote:
okashira wrote: SoC can be determined by voltage, temperature and chemistry, so you can skip the shunt too.
BMS just needs to provide voltage warnings (audible maybe) and perform balancing, smart/adjustable balancing is a must. Not just 4.2V balancing like the crap chinese BMS
Oh boy, that was plain dumb.
How can you determine accurate SOC other then coulomb method on Li?
I guess he's another cell-log fan.

If it has adjustable LVC, HVC, can be programmed for LiPO or LiFE it should be tits.
Dedicated LCD screen output (whatever protocol) for on-board instruments would be good.
It's true you need columb counting for LiFePO4. But LiFePO4 is being phased out... slowly.
But you don't need a shunt. Hall effect is fine
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Re: Yet another (?) Smart BMS?

Post by circuit » Feb 03, 2016 2:30 pm

okashira wrote:
circuit wrote:Balancing circuit in on bottom side of PCB. 6.2Ω/cell. Which is much more powerful than needed for quality cells.
Yep, even 20 Ohm is plenty if the BMS is smart enough to perform balancing at time other then 4.2V only.
The level of "early balancing" is adjustable. I usually set it on 3.5V for both LiFePO4 and Li-ion
okashira wrote:My other problem with MOSFETs is they can fail closed. And they are fragile. And they add resistance. I'd rather just use a fuse.
It is not mandatory to use mosfets. I myself don't use them. I connect controller directly to battery and use "logic supply switch" of the BMS to cut the controller (via second thinner supply wire). I get unlimited current and no heat in this way. But some still prefer mosfets.
okashira wrote:If you're relying on the MOSFETs turning off in a short circuit condition, the inductance and current can actually cause the mosfets to fail and continue to short. Oftentimes the battery circuit is pretty high inductance
Numerous tests were carried out and it does work well in short circuit conditions, with low and high inductance loads.
okashira wrote:But you don't need a shunt. Hall effect is fine
There are tradeoffs. Hall effect sensor consumes a lot of energy, and that is not a good thing in storage. But it generates less heat.
This BMS also comes in 30A version with shunt.
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Re: Yet another (?) Smart BMS?

Post by Punx0r » Feb 03, 2016 2:43 pm

It'd be nice just to have a high-powered, adjustable balance voltage, high-quality BMS that can be trusted not to murder your battery.

I must admit, I'd much rather have an (optional) simple external display that could take the place of a CA or wattmeter. Phone via Bluetooth might be great for those who love using their phone for everything, but they're big, need charging and are theft/crash-damage magnets.

I'd buy one right now that could be a BMS and wattmeter/cycle computer. The other features would be gravy, perhaps that I might never use.

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Re: Yet another (?) Smart BMS?

Post by circuit » Feb 03, 2016 3:23 pm

Phone solution is OK for occasional drivers. Also phone solution is very much OK as a standalone device. It is easy to integrate (non-removable), can run navigation and various other fancy things. I hate using navigation when cycling, experience is just awful. But if you take a cheap android phone, enclose it in theft-proof package and mount permanently... It's an entirely different thing.
I also went similar way with my car navigation: I bough "android mirror". Can't get enough of it now. Also takes calls, records road, shows rear parking camera..

This BMS actually supports CA v3 protocol. So any type of display or phone app will work, if it is compatible with CA. There were at least 4 of them available here on ES.
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Re: Yet another (?) Smart BMS?

Post by Syonyk » Feb 03, 2016 7:02 pm

Posting to follow. I've been looking into designing something similar, but I think this would handle everything I want.

Question: Can the BMS prevent charging for a period of time while the charger is plugged in (for example, running a heater until the pack has reached a certain temperature)? I'm sure I could do it with a set of small relays if needed.

I think this is easily a $150 BMS, perhaps more. I wouldn't hesitate to pay that much for it on a pack.

I'm planning to build a ~1.5kWh 16S pack in about two months to replace my 36v pack (I'll have a need for higher speed running), and I'd love to develop my pack around this if it was available, either in a test form or a production form.

It's wonderfully overkill, but I'm fine with that.

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Re: Yet another (?) Smart BMS?

Post by circuit » Feb 04, 2016 5:08 am

This BMS has a configurable value "Low temperature charging disable". When cell temperature is below set value, charging will not be enabled, until it warms up. Also, if connected, heater is enabled. Up to 1A if directly through BMS, or more with external relay.
2 months looks realistic.

Conformal coating is possible and probably will be done. Just note that connectors are not water proof, so it would add a layer of protection, but not 100%.
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Yet another (?) Smart BMS?

Post by izeman » Feb 04, 2016 8:03 am

Imho a BMS is there to be a last wall of defense to safe the battery. A controller's LVC or a charger's HVC does NOT replace a BMS. BMS' low/high voltage are there to safeguard the battery and avoid damage being done.
Balancing is important and for me 'smart BMS' is not feature wise smart, but allows distribution of charging current between low and high cells making balanced charging much faster and more efficient.

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Re: Yet another (?) Smart BMS?

Post by okashira » Feb 04, 2016 12:57 pm

circuit wrote:This BMS has a configurable value "Low temperature charging disable". When cell temperature is below set value, charging will not be enabled, until it warms up. Also, if connected, heater is enabled. Up to 1A if directly through BMS, or more with external relay.
2 months looks realistic.

Conformal coating is possible and probably will be done. Just note that connectors are not water proof, so it would add a layer of protection, but not 100%.
Are you planning on selling this?
My suggestion would be to make the isolation board separate. This way the user can choose, and it allows for more flexibility on power capability of the board (make it big enough to accept 8 to-220 FET's). It also gives you something else to sell that's meant to plug in right to your main board.
It's also nice to keep the high power mosfet's, etc separate from the delicate BMS brain board.
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Re: Yet another (?) Smart BMS?

Post by circuit » Feb 04, 2016 1:03 pm

It has several programmable signals for external switches, either contactors, third party mosfet boards or anything else you like.

Yes, this is going to be for sale soon.
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Re: Yet another (?) Smart BMS?

Post by ScooterMan101 » Feb 04, 2016 1:55 pm

Yes + 1,

Problems with using cell phone, even cheep android one, is that the battery drains too fast,
also
You must also take off the phone from the bike when ever you park the bike in public, otherwise someone will steal it,
no such thing as a theft proof iPhone/Android Phone case,
also
Many of us use the Phone mounted on the bike for other uses ( Compass, Map , running APP for video camera that is recording the bad car drivers that almost run into you ! )
The Battery of the Phone is used up too fast already.

A small , but big enough to read , Display, that can be seen in bright daylight, is a must .


Punx0r wrote:
I must admit, I'd much rather have an (optional) simple external display that could take the place of a CA or wattmeter. Phone via Bluetooth might be great for those who love using their phone for everything, but they're big, need charging and are theft/crash-damage magnets.

I'd buy one right now that could be a BMS and wattmeter/cycle computer. The other features would be gravy, perhaps that I might never use.

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Re: Yet another (?) Smart BMS?

Post by Syonyk » Feb 04, 2016 2:01 pm

circuit wrote:This BMS has a configurable value "Low temperature charging disable". When cell temperature is below set value, charging will not be enabled, until it warms up. Also, if connected, heater is enabled. Up to 1A if directly through BMS, or more with external relay.
2 months looks realistic.
Excellent! That will work perfectly for what I want.
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Re: Yet another (?) Smart BMS?

Post by Diesel Dave » Feb 05, 2016 11:06 am

Just about perfect for my 14s pack - so waiting eagerly for production to start.

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Re: Yet another (?) Smart BMS?

Post by ElectricGod » Feb 05, 2016 5:49 pm

I wish it supported more cells. hahaahaha! But seriously...a version that does 20 cells and then increment by 8 cells for the next version and so on.

I have looked for a BMS that handled more than just mosfet temps and they pretty much don't exist so my option was to use several op-amps on the temp input so I could measure more than one temperature via several sensors.

This BMS has a lot of cool features that I wanted a year ago. The programmable start/stop charge voltages is a great idea. The hall/current sensor will hopefully allow you to set the maximum discharge rate so you don't discharge faster than your batteries can handle. I have that feature in my kelly controller, but its really a BMS function IMHO. My Kelly has a low voltage shut-off, but that's just an aggregate pack voltage. It does nothing to protect individual cells and not all cells discharge at the same rate. A BMS can protect the pack by shutting it off once any cell reaches a low voltage set point. The alarm function I assume works similarly to how most R/C pack monitors work. IE: It starts making noise when pack voltage reaches a threshold. It would be better if it would alarm when any cell voltage reached like 10% over the set minimum voltage and then shut off at the minimum per cell voltage. I like the idea of an APK running on a phone and communicating via blue tooth. A programmable password for blue tooth access would be good. The last thing I would want is some random person getting into my BMS and changing the settings because the blue tooth password was 0000! I also like the idea of a dedicated LCD with a few control buttons. Yes your phone can get stolen or broken, but that can happen with you carrying it in your pocket too so I "meh" to that concern. Most phones now days have secure/waterproof holders for them so that's not a big deal to me. It's probably already there, but a switch controlled enable/disable feature would be great. IE: The BMS delivers a programmable amount of current while its disabled to keep the speed controller caps charged, but not enough to actually run anything. I have a key switch on my EV and it disables my Kelly, but the batteries are always live and I really dislike contactors (huge switches) and that's all a loop key is. A built in soft start function would be good too. All of us love the giant spark when we plug in our speed controller after it's been sitting unplugged for a while. I have a second power cable with a 3K resistor in parallel with my main power connection to limit inrush current.

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