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

[velias]

Can we still use higher value shunt resistors and not have to have the fan?
I've had good luck with the previous BMS and my batts. after 200+ cycles everything for me still balances within a minute or two with the larger value 15 ohm resistors.
Whats the pot adjust on top of the board?
Whats the shunt on top for?
What do the 2 tricolor LEDs on top control board signal?
I like how your going vertical with the plug in channel boards, the last one was getting pretty long and awkward.
Whats the estimate on the pricing for the bare boards and approx cost on the parts?

 

[mwkeefer]

Gary,

Awesome looking proto! Love the stacker style - I think you will see marked improvement in thermal dissapation when you enclose the unit and direct the airflow around the shunts.

Cant wait!

-Mike

 

[GGoodrum]

Can we still use higher value shunt resistors and not have to have the fan?
I've had good luck with the previous BMS and my batts. after 200+ cycles everything for me still balances within a minute or two with the larger value 15 ohm resistors.

Yes, you can certainly use smaller shunt resistors, and not have the heat issues, but one of the points of doing this upgrade was to be able to support larger pack setups, and higher shunt currents. BTW, today I added a second fan, on the right side, and now all the shunt resistors are barely over 100F, and that is with 1.06A of shunt current.

Whats the pot adjust on top of the board?
Whats the shunt on top for?

These are part of the new end-of-charge detection logic. The shunt is used to monitor the charge current. The pot is used to set a threshold/trip point for the current. When the current gets down to what the shunts can consume by themselves, the charge current is cutoff, or if the balancing mode is enabled, a timer is started, allowing additional time for all the cells to get fully charged. The pot is used to set the shunt current value. This is an easy, ten second adjustment that you only need to do once. All you do is hook the charger up, without the cells connected, and adjust the pot until the circuit trips. Since the only current flowing will be through the shunts.

What do the 2 tricolor LEDs on top control board signal?

The one on the left is just like the one on the v2.x boards, it starts out red, during the initial constant current (CC) charge phase. As the cells get full, and the shunts become active, the "throttling" starts which basically uses a PWM circuit to keeps any cell from going over the HVC point (about 4.17-4.18V...), by adjusting the duty cycle of the PWM circuit to cut the current back just enough to keep the voltage down. The green portion of the LED is tied to the duty cycle. As the "on" time decreases, the LED transitions from red to green.

The other LED is tied in with the current monitoring circuit. As long as the current is above the shunt value, the LED is red. As it gets down close to the trip point the green portion will start flashing on an off at a fast rate, and as it gets closer, the red portion goes all the way off. When the circuit finally trips, the red is off, and the green portion flashes at a slow (1Hz...) rate. Unless the balance mode is active the control circuit will shut down the charge process after about 10 seconds.

I like how your going vertical with the plug in channel boards, the last one was getting pretty long and awkward.
Whats the estimate on the pricing for the bare boards and approx cost on the parts?

I'm not sure, as I haven't figured out the costs yet, but it shouldn't be too far off what it was before. Many of the parts are the same. There's actually fewer parts in each channel circuit now, as we simplified this by combining the LVC and HVC functions to share an opto output. The control section is a bit more complex, but again there are many parts that are the same as what was used before.

You'll also be able to now simply order the control section, however many of cell section boards that are needed. Those that have existing v2.x units can also just order the control section, and upgrade the charge control function of their existing setup.

-- Gary

 

[alangsam1@me.com]

do these come built or is it a bag of parts that you have to solder up yourself - I would like a prebuilt and tested version?

 

[jorhyne1]

You will most likely be able to buy a completed version (once the updated BMS is released) from rechargeablelithiumpower.com , they sell the most recent version completed from $120-$220 depending on how many cells you need to manage.

 

[alangsam1@me.com]

thanks - that is FANTASTIC. that is a good deal IMO.
I need help in coming up with how many cells i am asking for and how i am going to connect the balance taps.

I have 4 x 6S 5800 Lipos in what i am calling 2S2P configuration? its a pair of the packs in parallel and then the two pair in series. I get about 50.4v at full charge with all cells at 4.20v.

As far at the balance taps - each pack has a balance tap with 7 wires to a typical balance connector. 6 black and one red? I see that the BMS has a connector with what looks like all black and one red?

 

[GGoodrum]

thanks - that is FANTASTIC. that is a good deal IMO.
I need help in coming up with how many cells i am asking for and how i am going to connect the balance taps.

I have 4 x 6S 5800 Lipos in what i am calling 2S2P configuration? its a pair of the packs in parallel and then the two pair in series. I get about 50.4v at full charge with all cells at 4.20v.

As far at the balance taps - each pack has a balance tap with 7 wires to a typical balance connector. 6 black and one red? I see that the BMS has a connector with what looks like all black and one red?

Yes, what you need is an adapter that connects the balance plugs from each of the two paralleled packs, and then has one output plug. I have adapters like that on my site here, but I'm going to do a new one to use with this new BMS. The reason is that with the higher shunt currents, and/or with distances between the packs and where the BMS mounts longer than 6-8", it is better to use larger gauge wires and a bit heftier connectors. I have new adapters that will have multiple JST-XH connectors for the plugs from each pack, and then pads for a larger connector type, a 7-pin Molex 3mm Micro-Fit connector.

-- Gary

 

[alangsam1@me.com]

ok i will wait for your new BMC to get the new adapters. Also what or how do i describe the BMS configuration i am asking for based on the pack configuration i have listed?

 

[GGoodrum]

ok i will wait for your new BMC to get the new adapters. Also what or how do i describe the BMS configuration i am asking for based on the pack configuration i have listed?

You need one 6-channel board for each 6s pack in series, plus one control board, so your configuration will be identical to the unit shown above. I've been testing this unit with 12s3p packs, which have three 6s-5000 packs in parallel, and two of these groups in series. Your configuration will be similar, except each of your two 6s groups have two 6s-5000 packs instead of three. Your pack configuration will be 12s2p.

-- Gary

 

[alangsam1@me.com]

can i order my BMS now to be first in line?

 

[AndyH]

do these come built or is it a bag of parts that you have to solder up yourself - I would like a prebuilt and tested version?

I just received my 'beta test' boards this afternoon. After I learn how to build them, and the Brains (Gary and Richard) get the configuration locked-down, I'll switch my BMS products from the V2.6c boards to this new version.

I have a place-holder in the store now (under development) but will move the boards and configuration options into the store once they're all defined.

Fun days begin with good coffee and a package from Gary and Mouser.

Andy
(gack...gonna need more solder...)

Rechargeable Lithium Power

 

[ejonesss]

the boards say lipo is that mean that they will not work on lifepo4 or did you decide/discover that we can treat lifepo4 the same as lipo and run them to a hvc of 4.12 and lvc of 2.5 or 2.0?

They will be available one week after I finish testing, and get a quantity of boards ordered. I hope to finish testing in the next two days. Right now I'm doing thermal tests with and without fans. With 1A shunts, there needs to be some sort of active cooling. Yesterday I tried a single fan, mounted on the left, as shown below. The fan actually moves quite a bit of air, but in this "open" configuration, the air is going to find the path of least resistance, so most of the air is flowing towards the bottom right, in front of the shunt resistors.

image clipped


This is causing the shunt resistors on the far right to get pretty hot, pretty quick, like around 250F. The first shunt resistors, closest to the fan, ran cool, like around 103-104F. The ones in between got progressively warmer. I simulated an air dam, of sorts, using my fingers, to try and vector the airflow over the shunt resistors, and that did help. The temps dropped on the end resistors. So, if a single fan is used, some sort of deflectors are going to be required in order to make sure the air is forced over the shunt resistors.

What I'm trying today is two fans. I mounted a second one on the right side, also oriented to blow air inwards, and wired it in series with the first fan. I also changed the resistor to 200 ohms.

We are also thinking adding 1 or 2 thermostatic switches to the input of the 12V regulator, which can be mounted at the hot spots, so that the control section will shut down if there's a fan failure.

-- Gary

 

[GGoodrum]

The layout is identical, for both versions, but the resistor labels on this one are for LiPo. The "production" version will have both, or neither.

I'm still chasing a couple last control section gremlins, which I literally hope to finish today. It means, however, one more layout iteration, which I can't submit until tomorrow, at the earliest. Bottomline is it will mean at least one more week before I can make them available.

-- Gary

 

[alangsam1@me.com]

your hard work will pay off. looks like a number of us are ready to order as soon as you have them ready to go!

 

[GGoodrum]

Okay, it looks like all Gremlins are back in their boxes, and it seems to be working fine now.

I will submit the new/updated layout tomorrow.

-- Gary

 

[rechargeourfuture]

"Lurking for hours trying to get caught up"

Can't wait to hear the "all clear" from you Gary! I will be ordering the v4.0 for myself asap.

I've sent you a message via the RLP website AndyH.

HUGE thanks to Gary and Richard for devoting themselves to this! I am so fortunate to be involved during such a large improvement in EV tech.

Brandon

 

[ejonesss]

i am watching both here and tppacks.com/products.asp?cat=26 closely now in hopes that the new board comes out.

 

[GGoodrum]

We're getting close. I just got some new boards in this afternoon. I think the 6s cell boards are done, but I need at least one more iteration on the control circuit boards. Richard had a couple more changes, and we found a couple of minor trace errors. We added a small cap across the bottom divider resistor on the cell circuits, to help in suppressing RFI, which could be an issue with longer cable runs between the BMS and the cell junctions. I also made the boards slightly narrower, from 3" to 75mm, so that the boards will fit the rails in the medium-sized Hammond extruded aluminum boxes.

-- Gary

 

[alangsam1@me.com]

do these come with the alumiunum boxes or do we need to get one?

 

[ejonesss]

looking at the dimensions of the enclosure i think you may be able to fit the board inside the cyclone battery tube boxes

http://www.cyclone-tw.com/0bike.htm

you can see it mounted on the back of the bike

each tube is 3 by 3 by 14 inches.

you can get them at http://www.cyclone-usa.com/ you need to contact jim olsen.

i am not sure how much the single tube kit goes for but the double tube is $35

We're getting close. I just got some new boards in this afternoon. I think the 6s cell boards are done, but I need at least one more iteration on the control circuit boards. Richard had a couple more changes, and we found a couple of minor trace errors. We added a small cap across the bottom divider resistor on the cell circuits, to help in suppressing RFI, which could be an issue with longer cable runs between the BMS and the cell junctions. I also made the boards slightly narrower, from 3" to 75mm, so that the boards will fit the rails in the medium-sized Hammond extruded aluminum boxes.

-- Gary

 

[alangsam1@me.com]

those boxes are HUGE? i hope that these boards in a 12s2p dont require something that humongous?

 

[alangsam1@me.com]

We're getting close. I just got some new boards in this afternoon. I think the 6s cell boards are done, but I need at least one more iteration on the control circuit boards. Richard had a couple more changes, and we found a couple of minor trace errors. We added a small cap across the bottom divider resistor on the cell circuits, to help in suppressing RFI, which could be an issue with longer cable runs between the BMS and the cell junctions. I also made the boards slightly narrower, from 3" to 75mm, so that the boards will fit the rails in the medium-sized Hammond extruded aluminum boxes.

-- Gary

looks like digi key carries them for $19 dollars and change

 

[GGoodrum]

those boxes are HUGE? i hope that these boards in a 12s2p dont require something that humongous?

Huge? :? Maybe you are looking at the wrong units? The one I think I linked to is about 3" wide, 4.7" long and 1.7" high. That is about the footprint of the stacked boards by themselves. There's just enough room inside for the three boards, plus two 30 x 30mm small fans, which can mount to one of the end plates. When I do the "production" boards, I was thinking of doing new end plates, one with mounts and air holes for two of these fans, plus connectors. The other new end plate will have holes for the LEDs.

-- Gary

 

[alangsam1@me.com]

i was talking about the cyclone ones not the ones you linked to they looked great. I was asking if you are including the case with the purchase of the BMS?

 

[methods]

I have been thinking...

Instead of using 5W resistors that are bulky and expensive, why not use a pair of 2W resistors that are less than half the price (especially in quantity), take up less area, cool more efficiently, and have a 30% lower profile?

Example:
5W 4.7ohm resistor ~ $0.70 each
2W 10ohm resistor ~ $0.14 * 2 = $0.28 each pair

5W 4.7ohm resistor ~28mm long and 9mm tall/wide, ~250 square mm
2W 10ohm resistor ~18mm long and 6mm wide/tall, ~216 square mm (for two)

5W 4.7ohm resistor 9mm tall
2W 10ohm resistor 6mm tall

(yes I realize this is not an apples for apples comparison but the principle holds - the smaller more common resistors are much cheaper. The honking 5W resistors are one-offs)

The price and area comes down even further if you want to run 3 or 4 in parallel.
There efficiency goes up since you now have more surface area as well.
This is what you see in most commercial balancers - especially those that are doing surface mount.

The only down side is assembly time / or Pick-n-place cost.

This is the direction that I would go. You can no doubt still do this with the current design by just running the pair through the over-sized holes - no need to spin the boards.
With fan cooling - 4W will be way more than enough. The power rating of the resistors is based on radiant cooling.

-methods