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

[JB_EB]

Gary - I would like to order one (1), 8-channel kit with 15 Ohm/2W shunts.

Thanks,
JohnB

 

[Deepkimchi]

Hello Gary,

Don't forget me.

Will be back from vacation in 1 week.

DK

 

[i8angus]

Hi Gary,

Put me down for (5) kits with 6.8 ohm/5W

Thanks!

 

[chessir]

hi Gary:

Put me down for (1) 16 channel 6.8 ohm/5w kit

thanx

 

[Ypedal]

I need at least 6 of them !! :lol: .. and also 6 x lvc boards.. gulp..$$$$

 

[BigR]

yep,

I also need 2X 16 channel 6.8 ohm/5W kits
and also 4X 8 channel 6.8 ohm/5W kits if possible

 

[PJD]

ypedal,

Curious, why do you need the separate LVC boards?

 

[julesa]

I need at least 6 of them !! :lol: .. and also 6 x lvc boards.. gulp..$$$$

The new BMS has an LVC circuit built in, doesn't it?

 

[fechter]

I need at least 6 of them !! :lol: .. and also 6 x lvc boards.. gulp..$$$$

The new BMS has an LVC circuit built in, doesn't it?

Yes, it does. If you are using individual cell chargers and don't need the charge control circuitry, you can use the LVC part only. I think Gary made some boards that do this.

 

[Ypedal]

ypedal,

Curious, why do you need the separate LVC boards?

Alot of bikes.. and alot of batteries :lol:

My current LiFe 12ah cells have no bms, and are charged with single cell chargers( i have 18 of them VP units now ) so i need LVC boards for those.

but my new, yet to arrive, not yet built PSI 10ah cell packs will have the full BMS !

I have a stockpile of Makita/Konion LiMn cells that also need LVC boards.

 

[Tom_D]

Question for Gary or fechter:
After the BMS master LED comes on, indicating all cells are fully charged, would a supplying Soneil charger also turn to a green LED light to indicate end-of-charge and shut down? In other words, could the charging operation be set-it-and-forget-it ? or would you have to manually turn off the Soneil charger once you saw the BMS master LED come on (to avoid continuous bypass heating on the BMS board)?

Thanks,
--Tom_D

 

[lazarus2405]

I've missed a lot of discussion! Well, let me jump right in. I've got several newbie questions here (well, newbie with respect to this).

These boards are for LiFePO4 cells, with a LVC of 2.1v and a charge termination of 3.65v, correct? What is necessary to change this to be more agreeable to LiMn, with a LVC closer to 3.0v and a charge termination of 4.15v?

What determines the required charger input voltage? Will any DC power supply do?

What governs the charging current, and how can it be changed to suit different sized packs?

Can only a fraction of the 16 channels be populated? That is, can you sell a 8 or 12 channel kit using the same PCB and an appropriately smaller bag of goodies at an appropriate discount? Or might you still have a 8-cell test board? My current 21-cell setup doesn't fit nicely into multiples of 16. :|

Thanks for the most excellent work you've done on our behalf.

 

[PJD]

Lazarus,

I think all of these answers were answered either in this forum or the older "16 cell battery management system" forum, It may take some digging. I'll save you some time on some questions.

The LVC uses the TC54 component which is available to schmucks like us only at 2.1 volt and 2.7 volt values. Gary can furnish either - e-mail him when you order. If you want another higher voltage value, you will need to take add a voltage-divider resistor pair to the TC54 input. According to a Bob Mcree (wonder how he is doing?) the total resistance of the voltage divider should be no more than 30K ohms to maintain an accurate voltage measurement, as the TC54 requires about microamp for the measurement.

Likewise, a higher charging voltage value for the cells can be had by using different values for the voltage divider resistors R1 and R2 for the LM431 - contact Gary when you order.

Any charger or DC power supply that furnishes (3.7 * no cells) plus a half volt or so should work.

The use of less or more than 16 cells was already answered in this forum, a few pages back.

- Paul D.

 

[lazarus2405]

Thanks for the reply. These 15-page 2-part threads really become a soup when you don't read them for months. x.x So much useful and possibly relevant information... To be fair, there are worse problems to have

Thanks for pointing me in the right direction for the non-multiple-of-16 answer. Found at http://endless-sphere.com/forums/viewtopic.php?f=14&t=5416&&start=150

For the power supply, you mean that it needs to at minimum provide the CV voltage * number of cells, plus about half a volt more to drive the BMS? Or do you mean the nominal voltage? And what sort of maximum voltage is suitable? As long as the supply voltage is below the FET's limit (Gary's using IRFB4110s, correct?), by how much can it safely exceed the pack voltage?

 

[fechter]

If the charging supply exactly matches the string voltage at max, then the shunts will be just on the verge of operation. You need a little more voltage to make sure all the cells reach the shunt voltage. It could be a lot more and it would still work.

With something like a Soniel charger, if the voltage was set so the total string current drops to under 100ma when everything is charged up, the charger light would go green and drop the voltage output causing the cells to stop charging. I'm not sure if you would really want this. The actual string voltage may be somewhat temperature sensitive.

 

[PJD]

Gary,

Get any kits out?

Maybe you should consider "outsourcing" the assembly and shipping of the kits. I'm sure there are some people in this forum who would do it at no cost for labor - including me.

 

[Tom_D]

With something like a Soniel charger, if the voltage was set so the total string current drops to under 100ma when everything is charged up, the charger light would go green and drop the voltage output causing the cells to stop charging.

To fechter:
Have you actually tried this? I know Gary has a Soneil, so I'm wondering if he has tried this as well? I need to let the the Soneil and the new BMS run to completion, with the BMS's master and Soneil's LED both green. Anything else won't work with my planned battery box, which will include batteries, BMS, controller and charger + temp controlled exhaust fan.

Also to Gary or fechter:
Can you give us curious and faithful followers a response as to WHEN the BMS will be offered again for sale? respecfully.

--Tom_D

 

[fechter]

No, I haven't tried this, but I know the Soniel will change modes when the charging current gets down to about 100ma. The Soniel (at least the one I have) also has a voltage adjustment trim pot inside that can be adjusted. If the adjustment goes far enough, it should be possible to tweak it so the charger drops into float somewhere around end of charge. This would effectively terminate the charge since the float voltage is lower.

I don't know how far the adjustment on the Soniel will really go.

I think it would work OK if the voltage on the Soniel was just cranked up as high as it can go and never let it go into float mode. The shunts would draw enough current to keep it out of float.

 

[PJD]

Can you give us curious and faithful followers a response as to WHEN the BMS will be offered again for sale? respecfully.

--Tom_D

I hope this isn't a repeat of the last time. Time to look into alternate ways of getting this built?

 

[Tom_D]

No, I haven't tried this, but I know the Soniel will change modes when the charging current gets down to about 100ma. The Soniel (at least the one I have) also has a voltage adjustment trim pot inside that can be adjusted. If the adjustment goes far enough, it should be possible to tweak it so the charger drops into float somewhere around end of charge. This would effectively terminate the charge since the float voltage is lower.

Fechter, thanks for your response. Yes, I am aware how to adjust the Soneil to set the max voltage before it goes into float (green LED indicator). For anyone else interested, see the attached instructions (BELOW).
>>> Gary, if you're out there........ If you know, will the BMS fully complete before the adjusted Soneil charger goes into float??
In other words, will all the cells get fully charged and all individual BMS LEDs go on BEFORE the Soneil goes into float??

I don't know how far the adjustment on the Soniel will really go.

There are limits according to the instructions below. I got my 4808 to go higher to 58.4v. May go a tad higher if needed.

I think it would work OK if the voltage on the Soniel was just cranked up as high as it can go and never let it go into float mode. The shunts would draw enough current to keep it out of float.

OK, this is obviously an alternative charging scenario to the above. If I understand you correctly, with the "voltage on the Soneil cranked up as high as it can go" the BMS would go to completion, charging all cells, turning all the individual LEDs a different color and turning the master LED a different color (green? i think). My concern here is that by the "shunts drawing enough current to keep it (the Soneil) out of float" the BMS would continue to generate enough heat to turn my battery box into an oven, while I was away, like on an overnight charge.

I have planned a thermostat-controlled exhaust fan in the battery box for the TEMPORARY charging heat generated, but I do NOT want a scenario where I have to deal with continuous bypass heat when there is no means of automated cut-off and the charging is left unattended.

Fechter, under this scenario, can you or Gary confirm (yes or no) that the BMS bypass heat will continue to be generated after all cells are fully charged, only stopped when the charger is manually turned off or removed :|

 

[fechter]

Yes, if the charger voltage is high enough, the shunts will stay at their maximum current and dissipate a crapload of heat. If you get the charger voltage tweaked so the current drops to under 100ma (or whatever the trip point for the soniel is), then it will shut off at end of charge. There is a chance the cells may be not fully charged at this point (although they would have to be close) and there is a chance that temperature changes could affect the set points enough to be an issue.

 

[Tom_D]

Yes, if the charger voltage is high enough, the shunts will stay at their maximum current and dissipate a crapload of heat. If you get the charger voltage tweaked so the current drops to under 100ma (or whatever the trip point for the soniel is), then it will shut off at end of charge. There is a chance the cells may be not fully charged at this point (although they would have to be close) and there is a chance that temperature changes could affect the set points enough to be an issue.

Fechter, thanks for confirming my understanding. I'm still shooting for the total enclosed batt/BMS/controller/charger box solution.

BTW---Any idea when when we can get commerce going again ?? Are there any issues other than Gary's new job demands or any technical issues being a factor?

--Tom_D

 

[PJD]

Tom,

"Commerce" in these boards never started. As far as I know, no one has recieved their kits yet. Mine are for vehicles that are used for virtually all my transportation, so maybe i'm a bit more impatient than others.

 

[fechter]

Fechter, thanks for confirming my understanding. I'm still shooting for the total enclosed batt/BMS/controller/charger box solution.

BTW---Any idea when when we can get commerce going again ?? Are there any issues other than Gary's new job demands or any technical issues being a factor?

--Tom_D

I'm not aware of any technical issues.

For a totally enclosed solution, the heat has to still go somewhere. You may be better off using a lower shunt current (10 or 15 ohm resistors) to limit the heating.

I had an idea for those that plan to bury the board deep inside a vehicle somewhere. It may be possible to use optical fibers attached to the LEDs to bring the visual indication outside somewhere. Optical fibers are nice and waterproof too. I used to have some very cheap plastic optical fibers lying around somewhere. If a tiny hole was drilled into the end of the LED lens, the fiber could be glued in. There may be a simpler way to attach them like heat shrink or something.

 

[Tom_D]

I'm not aware of any technical issues.

For a totally enclosed solution, the heat has to still go somewhere. You may be better off using a lower shunt current (10 or 15 ohm resistors) to limit the heating.

I plan on ordering the 15 ohm shunt BMS version to try to hold down the heat for my application. For the box,this is the dual fan I will use: http://www.outletpc.com/c1950.html . I like it because it is 80CFM, uses only .26A and will use 2 fans to draw hot air from all the top of the batt box. The air inlets will be on the bottom of the box, for appearance. I will tap the 12v from the batts and have 2 normally open 105F degree thermostats in parallel, positioned at the BMS and also the controller, so that when either gets to the temperature trip, the fan will turn on and cycle until the temp goes down to 90F. These are the thermostats: http://www.airpaxcorp.com/site/utilities/eliterature/pdfs/Airpax_SCSF_5003_0607.pdf
****All this assumes I will have success in getting the Soneil charger voltage output so that it will shut off when the BMS is about done.***

I had an idea for those that plan to bury the board deep inside a vehicle somewhere. It may be possible to use optical fibers attached to the LEDs to bring the visual indication outside somewhere. Optical fibers are nice and waterproof too. I used to have some very cheap plastic optical fibers lying around somewhere. If a tiny hole was drilled into the end of the LED lens, the fiber could be glued in. There may be a simpler way to attach them like heat shrink or something.

Fetcher, thanks for the fiber optics tip. I was going to do something similar like using the plastic LED extensions I salvaged from a JUNK Dewalt charger. They are clear, about 3/16"dia, 2" long, with a slight dome top. I will cut to length as needed.
----------------------------------------------------------------------------------------------------------------------
NOW, back to the main topic for this thread..........>>> Where is the

" Even Newer 16-cell Battery Management System (BMS) ?" :lol:

Fechter >>>>> Can you please give Gary a call and ask him to update the group? Thanks,
--Tom_D