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

[dnmun]

i think shenzen could build their power supply and sell it here for $56 if they made tons of them. there is no need for most of the features of an advanced charger, just step down current when shunts active, and they already build 10A supplies, very high quality power supplies, not cheap chargers, 48V for $36. so $56 or even $98 for 12A is easy for them.

 

[rf]

broken link

The Elite TSL60-15 ($239) looks like it might be okay for my 20s4p pack. Assuming 15-amps isn't too much for the BMS or the A123 cells. That appears to be the lowest power 72+volt charger they have. (A half-hour charge time would be pretty cool.)

http://tinyurl.com/3upqrm

Sorry about the link. Tinyurl seems to be broken lately.

http://elitepowersolutions.com/products/product_info.php?cPath=9&products_id=63&osCsid=c117873d20da25897786e7a0da425318

Richard

 

[rf]

a 72V battery is a 24 cell pack, and it actually needs 90V DC to charge [...]

My 20-cell pack charges to about 76-volts and needs a nominal 72+ volt supply to charge it. I'm using a charger designed to charge six 12-volt batteries in series, which yields 72+volts.

My controller is rated at 36 to 72 volts. If I connect your `72 volt' battery to it -- it will smoke.

Your 24-cell pack is more safely called 84-volts -- which would tend to keep you out of trouble with chargers and controllers, etc.

Richard

 

[ZapPat]

I have a couple very high quality vicor DC power supplies here that might interest someone here for a charging solution (this is what I'm using with a balancing BMS). I can set the output between 36V and about ~80V, and the output is 6.5A. These are CC/CV, and very precise. I'll post some details in the "for sale" forum if you ask (PM me). These are new, I just have two or three extras colecting dust. Or even better some kinda trade with a used hub motor involved?...

 

[ejonesss]

i was wondering if the bms has any current any voltage regulation for the charger?

because i found a way to get a 48 volt power supply.

i pulled the transformer from an old ups that runs on 24 volts and with the following doubler circuit

(i have not done tests yet) but in theory it should give me the 48 volts to charge the batteries.


and judging by the size of the wires that go to the inverter circuit it probably can handle 30 to 50 amps.

the ups has 2 30 amp fuses paralleled making 60 amp.

i was wondering if i can home brew my own power supply for charging? seeing that a 48v sla charger on on http://www.electricrider.com/chargers/index.htm starts at $80 for a generic and goes all the way up to $210 for a soneil charger.

 

[fechter]

i was wondering if the bms has any current any voltage regulation for the charger?

because i found a way to get a 48 volt power supply.

i pulled the transformer from an old ups that runs on 24 volts and with the following doubler circuit

.....

(i have not done tests yet) but in theory it should give me the 48 volts to charge the batteries.


and judging by the size of the wires that go to the inverter circuit it probably can handle 30 to 50 amps.

the ups has 2 30 amp fuses paralleled making 60 amp.

i was wondering if i can home brew my own power supply for charging? seeing that a 48v sla charger on on http://www.electricrider.com/chargers/index.htm starts at $80 for a generic and goes all the way up to $210 for a soneil charger.

The BMS requires that the charging supply be current limited. The voltage, however, does not need to be regulated. In actual practice, depending on your cells, the initial charging current with a 'raw supply' like the one shown may be within the allowable range. The size of the capacitors may limit the current also.

You could also put a large AC capacitor in series with the AC line to limit the current. This would need to be something that resembles a motor starting capacitor. I've never tried this, so I'm not sure how well it would work.

If you could find a load that pulls the voltage down to what a fully discharged pack would be, then measure the current, you could determine the maximum current. If the charge current is too high, the cells will puff out and rupture.

I was looking at some of the switching mode power supplies on ebay that might do the job. While more expensive, these would have current limiting and would be much smaller and lighter (easier to take with you).

 

[ejonesss]

i will be charging 48 volts of a123 cells pulled from 2 28 volt dewalt packs.

i want to start off small to get my feet wet in the lifepo4 scene to see if lifepo4 will be what i will need and if it works ok for me i will either save up and add more a123's or save up and get a ping battery on ebay witch comes with a charger and use the new bms instead of the ping bms.

looking at the image

q2 is controlling the power to the negative side of the battery so wouldnt the extra current just cause q2 to get hot or even blow?

so adding a large heatsink and fan to q2 and/or even substituting q2 for a higher current handling one work?

i was wondering if the bms has any current any voltage regulation for the charger?

because i found a way to get a 48 volt power supply.

i pulled the transformer from an old ups that runs on 24 volts and with the following doubler circuit

.....

(i have not done tests yet) but in theory it should give me the 48 volts to charge the batteries.


and judging by the size of the wires that go to the inverter circuit it probably can handle 30 to 50 amps.

the ups has 2 30 amp fuses paralleled making 60 amp.

i was wondering if i can home brew my own power supply for charging? seeing that a 48v sla charger on on http://www.electricrider.com/chargers/index.htm starts at $80 for a generic and goes all the way up to $210 for a soneil charger.

The BMS requires that the charging supply be current limited. The voltage, however, does not need to be regulated. In actual practice, depending on your cells, the initial charging current with a 'raw supply' like the one shown may be within the allowable range. The size of the capacitors may limit the current also.

You could also put a large AC capacitor in series with the AC line to limit the current. This would need to be something that resembles a motor starting capacitor. I've never tried this, so I'm not sure how well it would work.

If you could find a load that pulls the voltage down to what a fully discharged pack would be, then measure the current, you could determine the maximum current. If the charge current is too high, the cells will puff out and rupture.

I was looking at some of the switching mode power supplies on ebay that might do the job. While more expensive, these would have current limiting and would be much smaller and lighter (easier to take with you).

 

[GGoodrum]

RE: 72V charger....

http://elitepowersolutions.com/products/product_info.php?cPath=9&products_id=60&osCsid=c117873d20da25897786e7a0da425318

A bit expensive and out of stock, but at least there is something out there on the market....


.

Yeah, but that's not bad for a 72V/20A charger. The 15A model is only $288, which is quite a good deal. It's out-of-stock as well, but it doesn't look like it will be that long.

 

[GGoodrum]

i will be charging 48 volts of a123 cells pulled from 2 28 volt dewalt packs.

i want to start off small to get my feet wet in the lifepo4 scene to see if lifepo4 will be what i will need and if it works ok for me i will either save up and add more a123's or save up and get a ping battery on ebay witch comes with a charger and use the new bms instead of the ping bms.

looking at the image

q2 is controlling the power to the negative side of the battery so wouldnt the extra current just cause q2 to get hot or even blow?

so adding a large heatsink and fan to q2 and/or even substituting q2 for a higher current handling one work?

First of all, that is an older schematic, and in that version Q2 was being used as part of a 12V regulator, to supply power for the charger control circuit. It doesn't get hot and doesn't draw but a few milliamps of current. The FET doesn't get hot because it is not being used in a linear mode. I've yet to see one of these get more than a few degrees above room temperature. What is the "extra current" you are talking about?

Secondly, I'm not sure how many a123 cells the smaller Dewalt packs have, but you will need 16 of them for a 48V setup. You will only have 2.3Ah of capacity, however, which is not much at all.

 

[ejonesss]

i was referring to the mosfet that is closest to the charger not the ksc1009 transistor.

after looking at that schematic i see both are named q2 (possible typo?).


here is a modified copy to show what i am talking about (you will need to right click and open image in new window to see all of it due to a bug in the style sheets of the board

also do you have the latest schematic posted anywhere?

28 volt batteries have 8 cells and 36 volt batteries have 10 cells.

2 28 volt batteries make the 16 cells.

a nice feature for a future bms would be to have 16 separate charging channels so each cell is charged independently so thereby a standard automotive charger can be used.

from what i do know about electronics it would need 16 separate dc to dc converters that generate both a + and - output and will have to be inductor based or rapidly charge up a capacitor and then discharge it into the cell.

of course i dont know everything there is to need to know about electronics but i can experiment with junk and assemble kits and use a multi meter.

i will be charging 48 volts of a123 cells pulled from 2 28 volt dewalt packs.

i want to start off small to get my feet wet in the lifepo4 scene to see if lifepo4 will be what i will need and if it works ok for me i will either save up and add more a123's or save up and get a ping battery on ebay witch comes with a charger and use the new bms instead of the ping bms.

looking at the image

q2 is controlling the power to the negative side of the battery so wouldnt the extra current just cause q2 to get hot or even blow?

so adding a large heatsink and fan to q2 and/or even substituting q2 for a higher current handling one work?

First of all, that is an older schematic, and in that version Q2 was being used as part of a 12V regulator, to supply power for the charger control circuit. It doesn't get hot and doesn't draw but a few milliamps of current. The FET doesn't get hot because it is not being used in a linear mode. I've yet to see one of these get more than a few degrees above room temperature. What is the "extra current" you are talking about?

Secondly, I'm not sure how many a123 cells the smaller Dewalt packs have, but you will need 16 of them for a 48V setup. You will only have 2.3Ah of capacity, however, which is not much at all.

 

[methods]

...

:?

 

[fechter]

Well, to have separate cell chargers is a whole different approach. It works well but is expensive.

Q2 is our favorite IRFB4110, which is likely overkill. It is either full on or full off, so as Gary points out, it does not dissipate much heat even when it is throttling. With an adequate heat sink, it is rated for 70 amps. I estimate it can do 20 amps with no heat sink. 70 amps is likely more than your cells can take, so that is why the charging supply needs to be current limited.

 

[ejonesss]

however the IRFB4110 can be pulsed causing it to vary the charging by pulse width modulation the same thing used in the speed control for brushed motors.

then it is cheaper to charge the entire pack and control the charge the other cells to balance them?

Well, to have separate cell chargers is a whole different approach. It works well but is expensive.

Q2 is our favorite IRFB4110, which is likely overkill. It is either full on or full off, so as Gary points out, it does not dissipate much heat even when it is throttling. With an adequate heat sink, it is rated for 70 amps. I estimate it can do 20 amps with no heat sink. 70 amps is likely more than your cells can take, so that is why the charging supply needs to be current limited.

 

[GGoodrum]

<heavy sigh...>

 

[rf]

however the IRFB4110 can be pulsed causing it to vary the charging by pulse width modulation the same thing used in the speed control for brushed motors.

then it is cheaper to charge the entire pack and control the charge the other cells to balance them?

How many parts per cell are you envisioning?

Sounds complex.

 

[fechter]

however the IRFB4110 can be pulsed causing it to vary the charging by pulse width modulation the same thing used in the speed control for brushed motors.

then it is cheaper to charge the entire pack and control the charge the other cells to balance them?

Yes, that's exactly what our circuit does. The FET operates like a PWM to vary the current.
It is cheaper this way. If the cells are reasonably well matched, very little balancing need to take place on each charge cycle.

 

[ejonesss]

post updated:

content removed as it turned out to be off topic

 

[GGoodrum]

I think you need to start a new thread for this, as it has nothing to do with the BMS.

 

[ejonesss]

I think you need to start a new thread for this, as it has nothing to do with the BMS.

sorry for getting off topic.

please check your pm box i sent you a carefully written pm

 

[methods]

<heavy sigh...>

followed by hyperventilation

 

[wybornd]

and just a slight hint of fustration ...

 

[methods]

Since I imagine people are going to start building up their balancing cables in anticipation of the board, here is a source for balance taps.
I believe GGoodRum uses TP type of balance tap (good tap to use if you are not already tied into another type)
I use the JST XH type which are very common and found on many Chinese packs. Almost 100 spacing so blinky etc. will plug right in.

Since I use 6S packs I am always looking for 6S JST XH pigtails.
I found some 12 inchers at Radical RC.

12" 6S pigtail: SKU Number:C6SBAL
12" 6S extender: SKU Number:C6SBAL12EXTKOK

http://www.radicalrc.com/shop/index.php?rec=24&shop=1&cart=2046944&cat=157&keywords=&match_criteria=&searchCat=

Similar parts can be found on Hobby City but they are only 2-3".

Does anybody want to show a picture of how they balance wired up one of the 16 channel boards?

-methods

EDIT: I ordered the pigtails and received them. They are out of the extenders for now. I told them I wanted 20 or so. This is a mom-n-pop type business so dont expect overnight shipping. They are friendly and responsive though. Good business.

 

[Patriot]

The only questions I'll have when the boards are ready, is...

1. How much for/where to order all the parts?

2. And, how to wire it to the battery.


Other than that. I'll be good to go.

Laaa-Deee-Daaa-Daaa-Daaa... New battery, on the way soon.

 

[fechter]

Does anybody want to show a picture of how they balance wired up one of the 16 channel boards?

-methods

Here's mine:
It uses the 18 pin Molex connector.
The new boards are intended to be connected with pigtails, that is the connectors are not attached to the board.

 

[methods]

... Here's mine: ...

Very cool. I love pictures like that.
Pigtails are great fore me. One less place for a bad connection.

-Patrick