Even Newer 4 to 24-cell Battery Management System (BMS)

[wybornd]

As a replacement part for the 747-IXDF404PI i ordered the 747-IXDF404SI which is the SOIC (surface mount) version. These are still in stock and have the same pin configuration, but different pin spacings and dimensions. It will require a bit of craftiness to get the legs connected to the PDIP (Dual inline package) footprint, but if your good with a soldering iron and a scalpel will be very achievable.
The transistor will have many substitutes to choose from. Just compare its datasheet with the others using the "find similar" button on mouser.

It wont be long before Mouser sells out of other parts on the BOM list due to the enormous demand for these BMS units.
There is going to be long delays for those who get in late....

Hmmm way too scary for me to contemplate surface mount components. Richard, looks like you will be the shining star if you can find an alternative they have in stock.
Cheers Dean

 

[ejonesss]

digikey carries them too

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=IXDI404PI-ND

As a replacement part for the 747-IXDF404PI i ordered the 747-IXDF404SI which is the SOIC (surface mount) version. These are still in stock and have the same pin configuration, but different pin spacings and dimensions. It will require a bit of craftiness to get the legs connected to the PDIP (Dual inline package) footprint, but if your good with a soldering iron and a scalpel will be very achievable.
The transistor will have many substitutes to choose from. Just compare its datasheet with the others using the "find similar" button on mouser.

It wont be long before Mouser sells out of other parts on the BOM list due to the enormous demand for these BMS units.
There is going to be long delays for those who get in late....

Hmmm way too scary for me to contemplate surface mount components. Richard, looks like you will be the shining star if you can find an alternative they have in stock.
Cheers Dean

 

[rkosiorek]

you could use adapters to convert SOIC to DIP components.

View attachment 5ade_1.jpg

they are easy to use. to solder on the component you apply a small spot of crazy glue to the bottom of the ic. align it on the adapter. let the CA dry a few seconds. this is only to make sure that the chip does not move while soldering. be neat about this. make sure the part leads are centered ver the soldring pads. AND make sure you don't smear the glue where you intend to solder.

now you need some pins.



cut them into a couple of 4 pin strips. solder them into the holes. to get this.



or you could just use some of the wire leads trimmed from the other parts like resistors to solder the adapter direclt to the BMS board. just use a small piece of double sided sticky foam between the adapter and the board to hold it in place while soldering. the double sided foam will also space the adapter above the boards and make sure that the traces on the bottom of the adapter won't short against something on the board.

rick

 

[methods]

Mouser is only one chip house
Digikey and Newark are just as big if not bigger
There must be a dozen other smaller places that still carry small stock

Nothing on that board is exotic.
Get the manufactures part number and search with Google.
I have already ordered my board but I am waiting to order parts
Once I do I will share the locations where I source the Lipo parts

May be a bum deal for those who need special shipping out of the USA
I plan to pick and choose from several locations

BTW: No connector on this board. It is pigtail

-methods

 

[GGoodrum]

I read the skimpy specs at: http://soneil.com/Completesets/4808SRF.pdf and it looks like this charger behaves exactly like a CC/CV bench supply except after it hits CV of 59.2 V it then waits for the current to fall to some predetermined value, at which point it lowers the CV setting to 55.2 volts, the “Stage 3 Float Mode”. Sounds like that ought to work, but here’s a potential problem, as I see it. When the BMS starts throttling back the current as the shunts kick in, the charger would run the voltage up to 59.2 right away, because the current can no longer stay at CC. At this point the current may be low enough to cause the charger to switch into its float mode of 55.2 volts and consequently all the cells would not get a full charge. Perhaps a capacitor on across the charger output leads would help ride out the fluctuations as the BMS FET switches on and off, but I still worry that the average current could be low enough to trip the charger into float mode.

I think it will work if you crank the CV voltage high enough to keep all the shunts on. As the cells charge, the shunts will take over and keep the current high enough to keep the soniel from tripping into float mode. The Soniel I have trips at around 100ma. Once all the cells are full and the BMS trips, the current will be near 20ma and the soniel can go to float with no problems.

I have not tried it with a Soniel and this circuit.

With the 3610SRF, which is basically the same charger, internally, I was able to crank the voltage up enough that the float mode value was around 44.5V. What happened was that the charger went over that, by about 1.5V, which is fine, and then it resets and goes into the float mode which was set for 44.5V, or 3.7V per cell.

-- Gary

 

[GGoodrum]

It's amazing that everyone has already caused Mouser to run low and out of some of the parts.
and that the first batch of boards were sold out in less than an hour last saturday.
I'm surprised that there are so many people who have lifepo batts and need a BMS.
It also says a lot that it was a good solution for everyone especially the break-away board scheme.
I'm curious, Gary, if you dont mind, roughly how many have you been selling? Has it been distributed all over geographically, or just in the U.S. and Canada?
It looks like theres a big market for Batterys and BMS stuff or lack of companies that provide a good/inexpensive solution.
I guess it tells a lot about the lack of decent BMS's and the demand for raw cells on the market

The first day was nuts. I had no idea the demand would be so high. I know I'd need more, even before I enabled the first batch for sale, so I ordered more. The second batch should be here befoe the end of the week, so they will get shipped out by Friday. The second run sold out as well, so I rdered a third batch, which should be here early next week. These will ship whenever I get them. I think the supply is catching up to the demand now, because it is down to a couple orders a day now.

Orders have been from all over, but most of the foreign ones have come from Australia, the UK and from Europe. I don't really count Canada as foreign, but lots from there as well.

-- Gary

 

[rkosiorek]

i have gone through a couple of cycles on an 8S1P pack of Lifebatt cells using a Soneil 2409SR (no "F") charger inside ther is a pot you can use to tril the voltage up. i reset it to be 29.6V instead of the standard 29.2V

this seems to work okay. the pack will balace before going into float mode.

i just got one of the new Soneil 2410S-04 lithium chargers. This is one of the ones that comes from the factory preset for lithium batteries. I'll probably start using it near the end of the week when i finish building another pack.

rick

 

[velias]

I bet your glad, Gary, that you didnt sell a completed unit or kit/sell the parts.
I like this solution cause its simple, does what it needs to do and no software/programming is necessary.
It seems like these chinese BMS's that come with some packs are overly complicated and have processors that prematurely cut off/mess with the current.
I had a chinese one that when it first cut out had to hooked up to a charger for a second to reset it. I couldnt just plug/unplug it from the pack. Some times it would cut out for no reason on a fresh charge after a block or two. With the new BMS I can understand what it does, its not just a black box.

Eventually in a year or two I bet someone will offer a ebike BMS based on those new Linear Tech 6802 /Maxim 11068 chips but from what I heard they are unavailable becuase of great demand as well and they require a microcontroller and software so its a big job to design with and hard to customize it to what people want.

 

[Icewrench]

Thanks for all the effort and brainpower put into this project by all contributors. Just received a board in the mail. Soon the fun will begin. Thanks again. Al

 

[jwpower]

I read the skimpy specs at: http://soneil.com/Completesets/4808SRF.pdf and it looks like this charger behaves exactly like a CC/CV bench supply except after it hits CV of 59.2 V it then waits for the current to fall to some predetermined value, at which point it lowers the CV setting to 55.2 volts, the “Stage 3 Float Mode”. Sounds like that ought to work, but here’s a potential problem, as I see it. When the BMS starts throttling back the current as the shunts kick in, the charger would run the voltage up to 59.2 right away, because the current can no longer stay at CC. At this point the current may be low enough to cause the charger to switch into its float mode of 55.2 volts and consequently all the cells would not get a full charge. Perhaps a capacitor on across the charger output leads would help ride out the fluctuations as the BMS FET switches on and off, but I still worry that the average current could be low enough to trip the charger into float mode.

I think it will work if you crank the CV voltage high enough to keep all the shunts on. As the cells charge, the shunts will take over and keep the current high enough to keep the soniel from tripping into float mode. The Soniel I have trips at around 100ma. Once all the cells are full and the BMS trips, the current will be near 20ma and the soniel can go to float with no problems.

I have not tried it with a Soniel and this circuit.

With the 3610SRF, which is basically the same charger, internally, I was able to crank the voltage up enough that the float mode value was around 44.5V. What happened was that the charger went over that, by about 1.5V, which is fine, and then it resets and goes into the float mode which was set for 44.5V, or 3.7V per cell.

-- Gary

Now that’s a good idea I hadn’t thought of! Thanks. You crank the CV value up high enough that even if/when the charger goes into float mode, the float voltage will still be 3.7*number_of_cells or higher. I assume there is no way to adjust the float voltage and that it’s just a percentage of the main CV setting. Hopefully the 4808 will allow a high enough setting for this to work.

From reading the Soneil specs it looks like both the 3610SRF and 4808SRF switch into float mode when the current falls to 0.5 A, which is what the BMS will be trying to maintain while the shunts are active. If it won’t stay out of float and keep the voltage high enough, I had thought of another work-around. I could tap off of the ANY_SHUNT_ACTIVE signal and trip a circuit that would add an additional load in parallel with the entire battery stack such that there would be sufficient drain on the charger to keep it out of float until the BMS goes ALL_SHUNTS_ACTIVE and disconnects. I’d rather not have to do that because it adds complexity to your elegant design, plus additional heat to get rid of, but at least it’s an option.

I’m going to go ahead and order the 4808SRF and somewhere down the road I’ll post how it works out. I like the size and high power to weight ratio of this charger because I want to carry it with me for taking advantage of ‘free’ power whenever I find it. Btw- The best deal I’ve found is at BatteryStuff.com for $159 plus $8 shipping to Arizona.

-James

 

[fechter]

Hmmm way too scary for me to contemplate surface mount components. Richard, looks like you will be the shining star if you can find an alternative they have in stock.
Cheers Dean

Direct drop-in substitute for the IDXF404: TC428CPA or TC428EPA (Stock: 499 Can Ship Immediately)

Alternates for the KSA931:
KSA928
KSA916
KSA1281
KSA1013

Yes! don't forget DigiKey, Allied, Arrow and Newark as alternate sources for parts

 

[ejonesss]

i just got the board today and i am waiting for the mouser parts.

i only got enough parts to fill 16 channels as i am running a 48 volt system.

do i need to snap off the unused section of the board?

and if i decide later to fill the unused section of the board will that affect the other channels even if i dont add any more cells to the newly populated section of the board?

or should i leave the unused section blank until i am ready to add more cells?

and in the future if there is a need for more than 72 volts 24 cells are there plans for making and selling additional 4 channel/cell boards?.

To do 22 cells, you could do two boards of 11 channels, and then only populate the FET stuff on the first board.

-- Gary

You could also populate all the channels on the second board and only hook up the ones you need. The unused ones won't interfere with the active ones. This way you could change the number of cells anytime without having to reconfigure the BMS (up to capacity).

 

[GGoodrum]

I apologize for not getting the instructions done yet. I will try and get them finished tonight and then I will post them.

To cut off the unused portion, the easiest way is to use a large pair of shop scissors/tin snips. You just cut along the holes. It takes about 10 seconds.

Save the unused portions. I'm thinking of doing anothe board that just has the charger control logic, and either 4 or 8 channels. This could be used with the cutoff portion of a board, in order to do another independent pack. These will be a lot less expensive than the full 24-channel version.

Regarding the Soneil SRF chargers, I'm pretty sure you can dial up the "float" voltage so that it is about 3.7V per cell, which is perfect for the BMS. What happens is the main CV trip point will be about 1 to 1.5V higher, which is fine. When the pack reaches that point, the charger shuts off momentarily, and the float mode starts, with the current limited to about 1/2A. Again, this will be fine for the BMS, as it won't need to throttle the current as much.

-- Gary

 

[fechter]

i just got the board today and i am waiting for the mouser parts.

i only got enough parts to fill 16 channels as i am running a 48 volt system.

do i need to snap off the unused section of the board?

and if i decide later to fill the unused section of the board will that affect the other channels even if i dont add any more cells to the newly populated section of the board?

or should i leave the unused section blank until i am ready to add more cells?

You can leave the board intact and just not use the cells you don't need. It won't affect the active channels. You can even populate the unused part of the board and it won't interfere.

If you cut off a part and want to add it later, you need to connect 4 small wires between the parts.

Over 72v could possibly run into limitations with the onboard voltage regulator. If you use a small separate 12v supply when charging, the only limitation will be the voltage rating of the FET, which needs to handle the voltage difference between a depleted pack and the charger output.

 

[ejonesss]

the float voltage is that what happens when the charger is not connected to a battery? (charger is NOT an anti spark charger ( anti spark chargers is like the deka agm charger where if you short the leads nothing happens no sparks it requires a voltage to be applied to the output to turn it on)).

i was thinking maybe the next version of the bms could have the control part be a separate snap off section. or can the control section be eliminated by having the each channel's balancer powered off of the cells so each cell powers it's own balancer.

when i got the soniel charger i turned it up to 59.1 i did not change the current setting because i dont know how to measure the current in that way.

the way that you normally measure current is to use the multi meter's amp setting to measure how much the load draws by using the meter in series.

i am not sure if i can use the amp setting in parallel by shorting the charger through the meter basically using the meter as a load?

i know the output is current limited by default to less than 5 a because .

1. there is a 5 a fuse on the output.

2. i have shorted the output leads and held it like that and no blowing of the fuse in fact i think the led just flickered as the electronics detected a short and cycled off and on and that is how i know it is NOT an anti sparker.

I apologize for not getting the instructions done yet. I will try and get them finished tonight and then I will post them.

To cut off the unused portion, the easiest way is to use a large pair of shop scissors/tin snips. You just cut along the holes. It takes about 10 seconds.

Save the unused portions. I'm thinking of doing anothe board that just has the charger control logic, and either 4 or 8 channels. This could be used with the cutoff portion of a board, in order to do another independent pack. These will be a lot less expensive than the full 24-channel version.

Regarding the Soneil SRF chargers, I'm pretty sure you can dial up the "float" voltage so that it is about 3.7V per cell, which is perfect for the BMS. What happens is the main CV trip point will be about 1 to 1.5V higher, which is fine. When the pack reaches that point, the charger shuts off momentarily, and the float mode starts, with the current limited to about 1/2A. Again, this will be fine for the BMS, as it won't need to throttle the current as much.

-- Gary

 

[ejonesss]

i have been thinking and looking at the schematics and depending on the setup it may not be a good thing to connect to the brake.

i think it may be safer to have a relay wired such that when the lvc kicks in it simply cuts off the power.

if you are using the dynamic/regen braking and the lvc kicks in it could be a big surprise and cause loss of control.

 

[methods]

Thats the first thing you have said that I agree with

I didn't think about that. . . When my regen kicks in it is stiff, especially at lower pack voltages. If it turned on when I was not anticipating it, going full throttle, it would go ass over tea kettle FOR SURE. I set my regen to 100% because I found that fooling with variable regen was not practical.

Hmmm.... Yep, that would not be desirable. Regen braking at the worst possible time =) Weight forward, anticipating acceleration in the opposite direction. . . Especially for people with big torque setups like a 5305 on 100V.

Well. . . Using the brake line to open a relay is also better because it *would* save the batteries in the situation where the bike is left on for a week.

I am going to put something together like that some time in the next couple of weeks.

-Patrick

 

[fechter]

Regen won't be going through the control circuit, so the BMS won't affect regen operation.

Also, the LVC won't be tripping when you are charging during regen. The shunt circuits will still work even though the control circuit is off. This means the shunts will come on if any cell get up to the set point, but the cell voltage could possibly go over the set point since there is no control. I think it would be extremely rare when this would become an issue, such as being fully charged and using regen on a long downhill.

 

[methods]

Regen won't be going through the control circuit, so the BMS won't affect regen operation.

Also, the LVC won't be tripping when you are charging during regen. The shunt circuits will still work even though the control circuit is off. This means the shunts will come on if any cell get up to the set point, but the cell voltage could possibly go over the set point since there is no control. I think it would be extremely rare when this would become an issue, such as being fully charged and using regen on a long downhill.

I disagree. Please correct me if I am wrong:

Say my pack is near empty
I apply full throttle and start accelerating
At some point during that acceleration one cell in my pack drops below 2.7V
That cell dropping causes the BMS to trigger the ebrake line
On a Kelly Controller the ebrake line enables regen
My regen is set to 100% on ebrake input
This would cause the bike to go from full forward acceleration to full backward acceleration

Was there a different situation that you were envisioning?

-methods

 

[dnmun]

i liked the idea of using the microwave on the lipo. if the pouch is not mylar, they should penetrate a short distance, it would be interesting to see if the shock would restore some of the capacity, not more than a few seconds and the lowest power, but do it scientifically, establish the capacity by discharging through a load and keep track of the current and voltage with justin's CA, but nuke it in the parking lot since it may explode and catch fire, but not certain of that, but then retest it afterwards to see if any of the capacity returns, just curious.

i liked the ADHD hat though, it would not protect from the microwaves if he is sitting on it, but if you see a guy sitting on a smoking microwave in the parking lot with an aluminum foil hat, you will certainly have something to talk about.

 

[fechter]

Regen won't be going through the control circuit, so the BMS won't affect regen operation.

Also, the LVC won't be tripping when you are charging during regen. The shunt circuits will still work even though the control circuit is off. This means the shunts will come on if any cell get up to the set point, but the cell voltage could possibly go over the set point since there is no control. I think it would be extremely rare when this would become an issue, such as being fully charged and using regen on a long downhill.

I disagree. Please correct me if I am wrong:

Say my pack is near empty
I apply full throttle and start accelerating
At some point during that acceleration one cell in my pack drops below 2.7V
That cell dropping causes the BMS to trigger the ebrake line
On a Kelly Controller the ebrake line enables regen
My regen is set to 100% on ebrake input
This would cause the bike to go from full forward acceleration to full backward acceleration

Was there a different situation that you were envisioning?

-methods

I see. Yes, that could be bad.

In that case you would want to tie the LVC into the throttle line instead of the brake line so the regen brakes don't come on but the throttle is killed. You could use the same circuit that Justin posted for tying in the CA.

 

[methods]

Man, you are a smart cookie. . .

I always forget about using a strong pull-down to override a signal.
Good Idea! Thats exactly what I will do.

-methods

 

[michaelplogue]

In that case you would want to tie the LVC into the throttle line instead of the brake line so the regen brakes don't come on but the throttle is killed. You could use the same circuit that Justin posted for tying in the CA.

Which circuit would that be? I did some searching, but I'm not all sure what I should be looking for. I'll be using these boards with a Kelly also, so I guess I'll need to implement this as well.

 

[michaelplogue]

One other thing: I tried wading through the earlier posts of this thread, but it got to technical for me and had to throw in the towel. However, earlier on you mentioned using a loopback setup added to the charger plug as shown in your illustration (below). Is this still necessary with the current version of the board?

 

[methods]

In that case you would want to tie the LVC into the throttle line instead of the brake line so the regen brakes don't come on but the throttle is killed. You could use the same circuit that Justin posted for tying in the CA.

Which circuit would that be? I did some searching, but I'm not all sure what I should be looking for. I'll be using these boards with a Kelly also, so I guess I'll need to implement this as well.

On your controller this would be the Analog Throttle Input.
His advice applies to Xlyte controllers to. Really any controller.
I think it is actually a better solution.

The general idea goes like this:

Attach the BMS output to the throttle signal line.
There are 3 throttle wires: +5V, Signal, and Ground
The idea is that when the BMS senses a low cell it will yank the Throttle Signal line all the way down to ground.
Basically it is just shorting it out.

-methods

EDIT: Remember to put a standard diode (really any diode) in line between the BMS line and the Throttle line. You will point the arrow of the diode from the Throttle to the BMS. This means that you are hooking the anode to the throttle and the cathode to the BMS. This will stop any positive voltage from leaving the BMS and entering your throttle while at the same time allowing the BMS to "Sink" all the current from your throttle rendering it useless. Look up the CA instructions for another description. The Cathode is the end of the diode with the stripe.