bluetooth BMS?

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Fionn   10 mW

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Re: bluetooth BMS?

Post by Fionn » Feb 19 2018 6:13pm

izeman wrote:
Feb 19 2018 6:09pm
.) would it be possible to deactivate the BMS completely by just removing the most positive balance wire? if so this could be done by the switch as well -> no more voltage drain! but first of all i'll keep an eye on the self discharge issue to see if it's really needed.
No, the whole point is that it uses the top balance wire to draw power. If that's disconnected it just uses the next one.
The switch is the best way to shut it off completely.

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ElectricGod   10 MW

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Re: bluetooth BMS?

Post by ElectricGod » Feb 19 2018 7:04pm

Fionn wrote:
Feb 19 2018 5:26pm
I wouldn't pay too much heed to the individual cell voltages unless you've calibrated all cells using a Fluke or other high quality multimeter, same goes for the charging currrent.
Cell voltages are pretty close to accurate...enough so that I don't need a cell log or a DMM. I test software for a living. I spend my days scrutinizing things to see if they do what they say they do. So for me, looking at the displayed voltages and the real voltages is one of those sorts of things. Current draw was a little off. That could have been variation in my watt meter vs the shunts in the BMS or the fact that the atmega 328 has low resolution AD converters and it was doing it's best. Hard to say about that other than it it didn't match my measured results.
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Re: bluetooth BMS?

Post by ElectricGod » Feb 19 2018 7:14pm

izeman wrote:
Feb 19 2018 6:09pm
@electricgod:

.) my phone is brand new. it's a xiaomi mi mix2. with the original firmware it was working fine. rooted it, installed a beta rom from xiaomi to get oreo, and it failed to connect. well, at least i know how to make it work again -> downgrade.

.) it wouldn't suprise me to see a voltage decline in ANY fully charged battery after the first few days. i would monitor your battery drain with the pack at "storage voltage".

.) i can take a closer look to see where K1 is connected to. will do it tomorrow - time for bed now.

.) would it be possible to deactivate the BMS completely by just removing the most positive balance wire? if so this could be done by the switch as well -> no more voltage drain! but first of all i'll keep an eye on the self discharge issue to see if it's really needed.
Your phone is too new for the after market ROMs to catch you yet. Give it a little while. I bet that's your problem. That beta ROM wasn't fleshed out yet.

Fresh off the 66 volt charger, the app displays 65.9 volts and so does my DMM. I'll let the battery sit there for a few days and see what happens. I can later run it down part way and do the same check. Right now it's snowing and I'm not riding anywhere except in a heated car!
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Merlin   1 MW

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Re: bluetooth BMS?

Post by Merlin » Feb 19 2018 8:56pm

14 days later...

battery charged on 06.02.2018 3:50PM
Highest Voltage: 4,199v
Lowest Votlage: 4,193v

Battery State now on 20.02.2018 3:00AM
4,114v on all Cells.

4,199v - 4,114v =
0,085v drop in 14 days
0,170v drop in ~1 Month

Battery in Room Temperature, nothing attached or connected in this 14 days.
Brandnew Nkon Samsung 30Q

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ElectricGod   10 MW

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Re: bluetooth BMS?

Post by ElectricGod » Feb 20 2018 12:04am

so anyway...20S was relatively easy to figure out...totally missed the option in the windows app. why isn't this in the android app too?

I had to undo these solder bridges too.

Image
Last edited by ElectricGod on Feb 20 2018 1:44am, edited 2 times in total.
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Inwo   10 kW

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Re: bluetooth BMS?

Post by Inwo » Feb 20 2018 1:26am

I posted the place to change series string earlier in the thread.
Let me look for it.
Only from sw, not app.

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Re: bluetooth BMS?

Post by Inwo » Feb 20 2018 1:28am

On the first page.
Picture with circle.

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flippy   10 kW

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Re: bluetooth BMS?

Post by flippy » Feb 20 2018 10:05am

ElectricGod wrote:
Feb 19 2018 2:15pm
flippy wrote:
Feb 18 2018 3:27pm
izeman wrote:
Feb 18 2018 11:48am
first to mind would be IRFB4115 capable of 150V, but resistance is very high (~10mOhm)
would the IPP048N12N3G be a better alternative? (4.8mOhm)
https://www.infineon.com/cms/en/product ... 48n12n3-g/

i still plan on putting like a dozen on the board to replace the chinesium mosfets to get decent current capabillty.
Ignore the charge side mosfets. You only care about the discharge side mosfets. I wouldn't bother with mosfets that are rated higher than 100 volts. The BMS can't handle more than that anyway if yours is 20S or less. The IRF4110 or AOT290 will work well for this BMS.
i have a 32S bms and a 115v pack @4.1V.

so yeah, so i do need 120+V rating.
i cant find those AOT mosfets on digikey or mouser. are those the real deal because i only see them on the oriental markets...
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Re: bluetooth BMS?

Post by Fionn » Feb 20 2018 10:29am

nebulight wrote:
Jan 27 2018 9:00pm
mattjrogers wrote:
Jun 03 2017 6:06am
I have one of these BMS units. Just installed it a week ago and working through its functionality.

I alway hate when a board has conflicting markings - such as a separate place to solder P- and C-, but they tell you to put both wires on the C- tab. Why?
Does anyone know if the P- port works? I'd like to use this for a lifepo4 pack for an offgrid application and want separate load disconnect vs charge disconnect. If the P- for loads doesn't work, then this won't work for me.

Thanks!
Can anyone offer further insight on this?
My BMS is the same as this, with separate tabs and FETs but it is sold as having a common charge and discharge port. The two banks of FETs can definitely be independently controlled.
However the sample layout in the BMS datasheet shows them configured in series. It doesn't seem to make a lot of sense as surely both FET banks would have to be active simultaneously for the pack to be connected with this configuration. Both the FET banks are N channel.
Image
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Fionn   10 mW

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Re: bluetooth BMS?

Post by Fionn » Feb 20 2018 10:51am

Perhaps the pack is connected between the FET banks and the charge and discharge FETs are on either side which would mean the ports truly are separate?

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Re: bluetooth BMS?

Post by izeman » Feb 20 2018 11:01am

to make things clearer to follow it may make sense to post a picture of the BMS everyone is talking about so it's clear.
MY BMS has seperate charge and discharge FET-banks, and they don't share a common dis/charge port.
it also has the K1 connector, which others don't seem to have.
so a picture is much needed i think-

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Re: bluetooth BMS?

Post by Fionn » Feb 20 2018 11:31am

This is the one I'm talking about which is the same as the one you describe - separate charge and discharge FET banks.
Board.jpg
Board.jpg (83.27 KiB) Viewed 780 times
Clearly it doesn't share a common port, however the sellers recommended wiring diagram shows charge and discharge both wired to the same port which doesn't seem correct to me:
Board1.jpg
Board1.jpg (119.64 KiB) Viewed 780 times
I would have thought the pack should be in the centre with discharge and charge either side

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Re: bluetooth BMS?

Post by Fionn » Feb 20 2018 11:50am

I think the issue is that the datasheet shows a P and an N FET and the board has likely been laid out to support this, but has been populated with N FETs only. With how it has been built and wired, I don't see how the FET banks can operate independently.
If the discharge FETs open for example the charge path is also broken. I will need to do some testing this weekend.

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Re: bluetooth BMS?

Post by ElectricGod » Feb 20 2018 2:06pm

flippy wrote:
Feb 20 2018 10:05am
ElectricGod wrote:
Feb 19 2018 2:15pm
flippy wrote:
Feb 18 2018 3:27pm
izeman wrote:
Feb 18 2018 11:48am
first to mind would be IRFB4115 capable of 150V, but resistance is very high (~10mOhm)
would the IPP048N12N3G be a better alternative? (4.8mOhm)
https://www.infineon.com/cms/en/product ... 48n12n3-g/

i still plan on putting like a dozen on the board to replace the chinesium mosfets to get decent current capabillty.
Ignore the charge side mosfets. You only care about the discharge side mosfets. I wouldn't bother with mosfets that are rated higher than 100 volts. The BMS can't handle more than that anyway if yours is 20S or less. The IRF4110 or AOT290 will work well for this BMS.
i have a 32S bms and a 115v pack @4.1V.

so yeah, so i do need 120+V rating.
i cant find those AOT mosfets on digikey or mouser. are those the real deal because i only see them on the oriental markets...
I found them at Arrow/Verical...
https://www.verical.com/pd/alpha-&-omeg ... 0l-1206922

And on digikey...
https://www.digikey.com/products/en?keywords=aot2500

But not at mouser. No surprises there...they never carry AOT parts.

Also, 32S means 131 volts. A 120 volt mosfet will probably burn out at 131 volts. Also, 120 volts is soooo close to your stated 115v pack. The chances that you could exceed the voltage limits of a 120 volt mosfets are high and that means blown parts. You always want a decent safety margin so that stuff lasts long term. People commonly run 100 volt mosfets at 98 volts/24S and they blow up mosfets as a result. With a little safety margin, the mosfets last and last for years. 150 volt mosfets running at 32S or 131 volts gives you a decent safety margin.
Last edited by ElectricGod on Feb 20 2018 2:27pm, edited 2 times in total.
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Re: bluetooth BMS?

Post by ElectricGod » Feb 20 2018 2:09pm

Fionn wrote:
Feb 20 2018 10:29am
nebulight wrote:
Jan 27 2018 9:00pm
mattjrogers wrote:
Jun 03 2017 6:06am
I have one of these BMS units. Just installed it a week ago and working through its functionality.

I alway hate when a board has conflicting markings - such as a separate place to solder P- and C-, but they tell you to put both wires on the C- tab. Why?
Does anyone know if the P- port works? I'd like to use this for a lifepo4 pack for an offgrid application and want separate load disconnect vs charge disconnect. If the P- for loads doesn't work, then this won't work for me.

Thanks!
Can anyone offer further insight on this?
My BMS is the same as this, with separate tabs and FETs but it is sold as having a common charge and discharge port. The two banks of FETs can definitely be independently controlled.
However the sample layout in the BMS datasheet shows them configured in series. It doesn't seem to make a lot of sense as surely both FET banks would have to be active simultaneously for the pack to be connected with this configuration. Both the FET banks are N channel.
Image
datasheets and reality can be different. I never use the charge mosfets, just the discharge mosfets. Connect B- to the battery - and P- to your EV. That will eliminate the charge mosfets (C-) and use only the discharge mosfets.
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Re: bluetooth BMS?

Post by ElectricGod » Feb 20 2018 2:17pm

Fionn wrote:
Feb 20 2018 11:31am
This is the one I'm talking about which is the same as the one you describe - separate charge and discharge FET banks.
Board.jpg

Clearly it doesn't share a common port, however the sellers recommended wiring diagram shows charge and discharge both wired to the same port which doesn't seem correct to me:

Board1.jpg

I would have thought the pack should be in the centre with discharge and charge either side
see those 2 solder holes at the middle, right hand edge of the board? That's P-. Connect your EV here. If you care about having mosfets that control charge then run your charging port to C-. I'm never concerned with charge current. AT it's best, it's maybe 50% of discharge current so I never use C-. Charging and discharging for me always go through P-. Also, if you use regen, that happens through P-...that's just a form of charging. If that's safe through P- and it is, so is regular charging through P-. For the super safety conscious types, C- might have a place in an EV, but more most people it's completely extraneous. Never power your EV through C-. It can be done, but you double the mosfets in series and the related losses. What's the point in doing that? Why they show powering the EV from C- is a mystery to me. I sure wouldn't do that! I'd prefer to have all those wasted C- mosfets on the P- side where they actually matter.

Of course I've connected up BMS wrong before too. This is a couple of 16S 50 amp BMS that are currently in use and connected via the C- port, not P- (center solder hole)...DOPE! It works, just not optimal.

Image
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Re: bluetooth BMS?

Post by izeman » Feb 20 2018 4:06pm

i measured current flow at cell#15 in stanby and with active BT connection.
w/o BT connection it's hardly measureable. 1mA blinking every now and then, and then showing 0mA again.
when active i see 13mA.
the question now is: how ACCURATE is my fluke at such low current flows? but still it proves the fact that it goes to standby mode where voltage drain is massively reduced.
with 1mA draw my 30,000mAh pack could last a LONG TIME before it's empty.
i still got the BMS connected for the next week or two to see how the voltage drops ...

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Re: bluetooth BMS?

Post by amberwolf » Feb 20 2018 4:30pm

ElectricGod wrote:
Feb 19 2018 1:11pm
These 3 CZT5551 NPN transistors and 3 more on the other side of the board all look like they are in parallel. Perhaps they make up the power component for a regulator somehow?
If they are depletion-mode FETs, then they can be used as a regulator the same way the Cycle Analyst from Grin Tech does it, which doesn't require switching or inductors.

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Re: bluetooth BMS?

Post by ElectricGod » Feb 20 2018 6:48pm

amberwolf wrote:
Feb 20 2018 4:30pm
ElectricGod wrote:
Feb 19 2018 1:11pm
These 3 CZT5551 NPN transistors and 3 more on the other side of the board all look like they are in parallel. Perhaps they make up the power component for a regulator somehow?
If they are depletion-mode FETs, then they can be used as a regulator the same way the Cycle Analyst from Grin Tech does it, which doesn't require switching or inductors.
Except they are NPN transistors, not mosfets.

Infineon did a PDF on depletion mode mosfet uses. And an example of using one as a voltage regulator. Based on this schematic, using an NPN in this configuration would not turn on the transistor since they need to be conducting already to bias their own base in this fashion...like a depletion mode mosfet does to its gate. Bipolar transistors don't work this way. So if those 6 NPN's are in fact some portion of a voltage regulator, then they are operating some other way to be used in a linear regulator.

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Re: bluetooth BMS?

Post by shorza » Feb 21 2018 2:23am

Fionn wrote:
Feb 19 2018 4:28pm
ElectricGod wrote:
Feb 19 2018 4:16pm
Just replace the little BT board on the back plane. If it costs you $10, I'll be surprised.
I don't need to, they just plug in on my board. I only mentioned it since someone mentioned not being able to connect via Bluetooth. I was offering the possibility of a faulty BT module as a possible explanation.
Thanks Fionn,

I'll wait for the seller to come back on line and hopefully they can send another BT module.
On the module that doesn't work, are you able to see it but not connect to it? Or not see it at all?

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Re: bluetooth BMS?

Post by Fionn » Feb 21 2018 3:47am

shorza wrote:
Feb 21 2018 2:23am
On the module that doesn't work, are you able to see it but not connect to it? Or not see it at all?
I can't see it at all.

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Re: bluetooth BMS?

Post by Coltheplumber » Feb 21 2018 7:26am

Regarding the Bluetooth-
On initial powering up of my BMS, the Bluetooth module had a solid blue light, neither my phone or tablet would pick up the device.
After much messing around the solution was to unplug the balance cable, disconnect the Bluetooth module, reconnect the balance cable and THEN reconnect the Bluetooth module.
Open up your app and it will now let you connect
Once paired the solid blue light will come on 😁

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Re: bluetooth BMS?

Post by Fionn » Feb 21 2018 7:56am

ElectricGod wrote:
Feb 20 2018 2:17pm
see those 2 solder holes at the middle, right hand edge of the board? That's P-. Connect your EV here. If you care about having mosfets that control charge then run your charging port to C-. I'm never concerned with charge current. AT it's best, it's maybe 50% of discharge current so I never use C-. Charging and discharging for me always go through P-. Also, if you use regen, that happens through P-...that's just a form of charging. If that's safe through P- and it is, so is regular charging through P-. For the super safety conscious types, C- might have a place in an EV, but more most people it's completely extraneous. Never power your EV through C-. It can be done, but you double the mosfets in series and the related losses. What's the point in doing that? Why they show powering the EV from C- is a mystery to me. I sure wouldn't do that! I'd prefer to have all those wasted C- mosfets on the P- side where they actually matter.

Of course I've connected up BMS wrong before too. This is a couple of 16S 50 amp BMS that are currently in use and connected via the C- port, not P- (center solder hole)...DOPE! It works, just not optimal.
I'm interested in using the charge termination to limit charging to lower than the standard charger output (or above what it's set to as an additional safety net).
I also have an interest (like one or two other posters here) in using these with lithium based renewable energy systems where having separate load and charge disconnects is very useful.
I hope to try and trace out a partial schematic for this board over the weekend to make sense of the implementation.

As you say, they seem to be recommending running power through both FET banks, which is not an optimal solution.
Also, it seems strange that both FET banks drains are connected together while the load current is expected to pass through them in series.
Does this not mean the charge FETs are reverse biased?
N channel fets.jpg
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Re: bluetooth BMS?

Post by ElectricGod » Feb 21 2018 11:52am

shorza wrote:
Feb 21 2018 2:23am
Fionn wrote:
Feb 19 2018 4:28pm
ElectricGod wrote:
Feb 19 2018 4:16pm
Just replace the little BT board on the back plane. If it costs you $10, I'll be surprised.
I don't need to, they just plug in on my board. I only mentioned it since someone mentioned not being able to connect via Bluetooth. I was offering the possibility of a faulty BT module as a possible explanation.
Thanks Fionn,

I'll wait for the seller to come back on line and hopefully they can send another BT module.
On the module that doesn't work, are you able to see it but not connect to it? Or not see it at all?
you don't really think you will get customer service from a Chinese seller do you? They work 100% on bare minimum margins. Warranty replacement for this component is unlikely IMHO.

I suspect that you will get on ebay and find that BT board yourself in 1/10th the time it takes to get a replacement after much arguing with the seller.
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Re: bluetooth BMS?

Post by Fionn » Feb 21 2018 12:07pm

ElectricGod wrote:
Feb 21 2018 11:52am
you don't really think you will get customer service from a Chinese seller do you? They work 100% on bare minimum margins. Warranty replacement for this component is unlikely IMHO.
I've gotten the best customer service I've ever received from AliExpress sellers where I lodged claims on, or shortly after receipt of the goods.
Only last week I received a board with some defects due to shipping damage (and poor packaging), a pot was snapped off and an electrolytic was badly dented. After sending some photos I received a full refund for the price of the item and shipping and wasn't under any obligation to return the goods.
My previous order was for 5 items, one of which was defective. The seller immediately shipped 2 replacements at no cost.

The way their marketplace works I believe is that the seller doesn't get paid by AliExpress until the customer confirms satisfactory receipt of the goods.

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