New 16-cell Battery Management System (BMS)

[PJD]

Odd question - is it worth it to patent your board before posting the schematic ?

People seem to be patenting things that could never have been patented before. For example, in my field, someone got patent that covers any concrete that uses recycled old concrete in the mix (unless it is below some unusable compressive strength). The result? The beneficial re-use of old concrete was greatly reduced.

On my e-max's controller, not only are schematics not available, but the numbers were carefully scraped off all IC's used on the board. Fortunately, I also have an older controller where this wasn't done.

[Beagle123]

I, for one, REALLY appreciate Gary and Bob's efforts. I think you guys are filling perhaps our most iportant issue. I have ideas on this myself, and I'm looking forward to seeing how you guys do it. I don't care too much about who comes up with a good solution, or who gets credit. I'd just like to see it get done.

I encountered the problem of one of my cells going bad when my overall voltage was fine. WHen I got home, the bad cell was 0.9v.

I'm going to look to see if you guys have posted the schematic.

I will gladly share any ideas with you guys.

[Dr. Shock]

I used to hear patent lawyers say that a patent is worth what you're willing to spend to defend it. You can end up ruining your enterprise in legal fees, and often the infringer just files for bankruptcy protection if you win.

[GGoodrum]

Yeah, a patent wouldn't be worth the trouble. About all we will do is maybe copyright the documentation, mainly to keep a manufacturer from lifting everything verbatim.

Bob is right, though, we are definitely not going to rich building and selling these. At this point, I'll be happy to break even at some point. If you buy the parts in small quantities, it is going to cost about $80. The boards will cost over $20 in small (<10...) quantities. I can save some by getting higher quantities, on everything, which is what I'm doing. I'm hoping to hold the kit price to just under $100. I think we will also now be able to offer an assembled and tested version, hopefully for not too much extra.

We finally finished up the testing and are now going through verifying the assembly and test procedures. This will be done today, hopefully. Kits should be available in the next day, or so. We will post the schematic here, in a little bit. I just need to clean up a couple of things.

-- Gary

[DeeL2003]

Wooah, I've been out of the loop for a few months now . So what did I miss? j/k Man this is cool. So I can use this BMS with my Mastech PSU to charge my A123 16s5p pack and totally eliminate the Hyperion balancers I've been using ? And I don't have to sit there and make sure the Mastech doesn't overcharge my pack cuz the BMS will cut off the current? Nice. I hated waiting for the Mastech to hit 0.8mA to 1.0A before I can shut off the charge.

Since I also don't have a LVC board to protect my pack during discharge, your BMS will cover that for me too ? Nice. I think I still have some space in my rack bag.

Sorry, just had to make sure I was reading everything correct. This is what I've been waiting for.

[fechter]

There's no doubt that Gary and Bob's circuit will be great. There is also a rapidly growing market for this kind of thing, but nobody wants to sit around assembling these things (at least not anyone I know). Once the design gets ironed out and tested, it would be cool if somebody got a large batch of them built in a factory (by machines). If the quantity was large enough, the price would come down.

Anybody want to make an investment?

Any idea what it would cost to have them completely assembled?
For automated assembly, a surface mount component version would probably be cheaper.
There must be places that speciallize in doing this kind of work, but I don't know any...

[bobmcree]

Wooah, I've been out of the loop for a few months now . So what did I miss? j/k Man this is cool. So I can use this BMS with my Mastech PSU to charge my A123 16s5p pack and totally eliminate the Hyperion balancers I've been using ? And I don't have to sit there and make sure the Mastech doesn't overcharge my pack cuz the BMS will cut off the current? Nice. I hated waiting for the Mastech to hit 0.8mA to 1.0A before I can shut off the charge.

Since I also don't have a LVC board to protect my pack during discharge, your BMS will cover that for me too ? Nice. I think I still have some space in my rack bag.

Sorry, just had to make sure I was reading everything correct. This is what I've been waiting for.

yes, yes,thanks. the cell cutoff for charge can be adjusted from 3-4v with the standard values or by changing a resistor it could be anywhere from 2.5v-7v, and the lvc can be 2.1 or 2.7 or anything over 2.1 by adding a resistor pair to each channel

the mastech is probably the cheapest adjustable power supply around. i have the same one with a different name i use often. it will be necessary to have a variable power supply to test the board and adjust the shunts. i am including a link to a kit for $24 that runs 110v to 0-12v at 2A or a parts list and schematic to make a 0-12v 2A supply out of <$10 in radio shack parts that could be powered by your batteries, to use in adjusting the shunts and testing.

[bobmcree]

There's no doubt that Gary and Bob's circuit will be great. There is also a rapidly growing market for this kind of thing, but nobody wants to sit around assembling these things (at least not anyone I know). Once the design gets ironed out and tested, it would be cool if somebody got a large batch of them built in a factory (by machines). If the quantity was large enough, the price would come down.

Anybody want to make an investment?

Any idea what it would cost to have them completely assembled?
For automated assembly, a surface mount component version would probably be cheaper.
There must be places that speciallize in doing this kind of work, but I don't know any...

i believe these boards will take a trained assembler about 2 hours. i will try to keep the labor on assembled units at $30. we intend to go to smt after we get some feedback and make sure it does everything most people want. once it is smt the labor cost will go way down and we could have a batch made. this is all gary's area, i am only doing the design work. anybody wanting to invest in the bms can talk with him. if you want raw cells, i will sell them for $40 plus shipping in any quantity. i was previously not lowering the price to $40 unless people bought 16 cells. btw my cost is $35 + shipping to me, so i am basically giving them away to build a market and hoping the price will come down when more people start buying them.

[GGoodrum]

Wooah, I've been out of the loop for a few months now . So what did I miss? j/k Man this is cool. So I can use this BMS with my Mastech PSU to charge my A123 16s5p pack and totally eliminate the Hyperion balancers I've been using ? And I don't have to sit there and make sure the Mastech doesn't overcharge my pack cuz the BMS will cut off the current? Nice. I hated waiting for the Mastech to hit 0.8mA to 1.0A before I can shut off the charge.

Since I also don't have a LVC board to protect my pack during discharge, your BMS will cover that for me too ? Nice. I think I still have some space in my rack bag.

Sorry, just had to make sure I was reading everything correct. This is what I've been waiting for.

If the Mastech will go up to about 16 x 3.65V + about .5V, then yes, this will work fine. The BMS does include the LVC function, and has two 4110 FETs to do active cutoff of the negative power lead if triggered.

-- Gary

[GGoodrum]

As Bob says, we can do an SMT version, but we'll wait a bit and see if there really is a demand. This would get the cost down.

For now, for those wanting fully assembled and tested versions, Bob will do them. If the demand gets too high, we'll look for some other intermediate options. We have looked into having htem assembled in Mexico, for instance, using the existing layout.This could save a decent amount of cost, as a lot of the parts are made down there now anyway.

-- Gary

[DeeL2003]

Count me in on one of the pre-assembled and tested BMS. I'm too solder and electronically-challenged. I hope you'll offer them soon after your kits are released. BTW, how do I go about connecting the BMS to my existing pack. Pics can be found here: http://endless-sphere.com/forums/viewtopic.php?f=14&t=2317. Do I have to take it all apart or can I use my existing Hyperion and powerpole connectors?

About the Mastech, I have the 5020 model so I had to charge each 8s5p separately. So does that mean I need two BMS's since I can't charge a whole 16s together?

Thanks for the quick reply guys.

[GGoodrum]

Count me in on one of the pre-assembled and tested BMS. I'm too solder and electronically-challenged. I hope you'll offer them soon after your kits are released. BTW, how do I go about connecting the BMS to my existing pack. Pics can be found here: http://endless-sphere.com/forums/viewtopic.php?f=14&t=2317. Do I have to take it all apart or can I use my existing Hyperion and powerpole connectors?

About the Mastech, I have the 5020 model so I had to charge each 8s5p separately. So does that mean I need two BMS's since I can't charge a whole 16s together?

Thanks for the quick reply guys.

Yes, I remember this. You can definitely use the existing Hyperion connectors. You just need to have matching plugs that can attach to the BMS board(s). You need to either break the main power lead connections, and insert the board in between, or just add Powerpoles to the BMS input wires, and plug into the ones coming from the pack. The board has separate output connections so you can simply run wires from these with two more Powerpole connectors. There are also two separate charger + and charger - connections, so a separate set of charger wires are used.

Although with a different supply only one board would be required, you could do this with two boards, each populated with half the channels, and charge each half separately, like you are doing now.

-- Gary

[bobmcree]

Count me in on one of the pre-assembled and tested BMS. I'm too solder and electronically-challenged. I hope you'll offer them soon after your kits are released. BTW, how do I go about connecting the BMS to my existing pack. Pics can be found here: http://endless-sphere.com/forums/viewtopic.php?f=14&t=2317. Do I have to take it all apart or can I use my existing Hyperion and powerpole connectors?

About the Mastech, I have the 5020 model so I had to charge each 8s5p separately. So does that mean I need two BMS's since I can't charge a whole 16s together?

Thanks for the quick reply guys.

if your supply is 50v 20A it probably goes to 51-52v so you need another 8v or so. i have some 3.3v 20A switching modules that are isolated and can thus be put in series with your supply output to raise it up by 4.5v each so two of those would get you up to 59-60v and they would also be powered by your mastech supply, so you could still easily provide the 8A charge current limit of the bms. these supplies are about 1" x 2" x 1/4" each rated 66w. they list in digikey for $169 but you can get them new for $10 at http://tinyurl.com/2b7ayo the supplies have trim and sense inputs that can be used to limit current and raise voltage to at least 4.5v. they are also good as single cell chargers where one 48v system can power each to exactly 3.65v and thus safely charge at up to 20A. i have used 16 of them powered by a 1200w 48v supply and i can charge my lifebatt pack in 1/2 hour. Two of these in series with your supply output will get your supply up to 60v. there are no connectors supplied but if we are building it for you we could do a custom version for a few bucks extra with the proper connectors.

[DeeL2003]

Count me in on one of the pre-assembled and tested BMS. I'm too solder and electronically-challenged. I hope you'll offer them soon after your kits are released. BTW, how do I go about connecting the BMS to my existing pack. Pics can be found here: http://endless-sphere.com/forums/viewtopic.php?f=14&t=2317. Do I have to take it all apart or can I use my existing Hyperion and powerpole connectors?

About the Mastech, I have the 5020 model so I had to charge each 8s5p separately. So does that mean I need two BMS's since I can't charge a whole 16s together?

Thanks for the quick reply guys.

Yes, I remember this. You can definitely use the existing Hyperion connectors. You just need to have matching plugs that can attach to the BMS board(s). You need to either break the main power lead connections, and insert the board in between, or just add Powerpoles to the BMS input wires, and plug into the ones coming from the pack. The board has separate output connections so you can simply run wires from these with two more Powerpole connectors. There are also two separate charger + and charger - connections, so a separate set of charger wires are used.

Although with a different supply only one board would be required, you could do this with two boards, each populated with half the channels, and charge each half separately, like you are doing now.

-- Gary

Yeah I tried getting Mike to find me a set of matching 7 pin Hyperion connectors a while back, but it proved more difficult than expected. The only matching set came from the Hyperion balancer itself and it's already pre-installed. Can't find them loose. I hope there's a simple way around this.

About the BMS, I think getting 2 would be too much cost-wise. Is there any way to just have one 8s pack connected to the BMS,then to the PSU and charge separately? And when it's time to ride, connect both packs to the BMS? If not, I'll go with Bob's idea.

[DeeL2003]

Count me in on one of the pre-assembled and tested BMS. I'm too solder and electronically-challenged. I hope you'll offer them soon after your kits are released. BTW, how do I go about connecting the BMS to my existing pack. Pics can be found here: http://endless-sphere.com/forums/viewtopic.php?f=14&t=2317. Do I have to take it all apart or can I use my existing Hyperion and powerpole connectors?

About the Mastech, I have the 5020 model so I had to charge each 8s5p separately. So does that mean I need two BMS's since I can't charge a whole 16s together?

Thanks for the quick reply guys.

if your supply is 50v 20A it probably goes to 51-52v so you need another 8v or so. i have some 3.3v 20A switching modules that are isolated and can thus be put in series with your supply output to raise it up by 4.5v each so two of those would get you up to 59-60v and they would also be powered by your mastech supply, so you could still easily provide the 8A charge current limit of the bms. these supplies are about 1" x 2" x 1/4" each rated 66w. they list in digikey for $169 but you can get them new for $10 at http://tinyurl.com/2b7ayo the supplies have trim and sense inputs that can be used to limit current and raise voltage to at least 4.5v. they are also good as single cell chargers where one 48v system can power each to exactly 3.65v and thus safely charge at up to 20A. i have used 16 of them powered by a 1200w 48v supply and i can charge my lifebatt pack in 1/2 hour. Two of these in series with your supply output will get your supply up to 60v. there are no connectors supplied but if we are building it for you we could do a custom version for a few bucks extra with the proper connectors.

Email sent