Cut off voltage lithium battery?

audioguru · May 3, 2016

I am just guessing that "lift the voltage" is a bad translation of something. I am also guessing that the board does not limit overcurrent, it is able to pass 30A which might cause your shorted battery cells or your wiring to catch on fire.
My electric radio controlled model airplanes are powered from a 2-cells Li-Po battery. If I try a take-off from grass but the propeller gets stuck and the motor is stalled then its current goes very high. The protection circuit senses the overcurrent, causes the motor to squeal loudly for a moment to warn me then it shuts off. No fire. It is reset by turning down the throttle then back up.

spec · May 3, 2016

Rorut said:
Looking forward to see what you are working on. I will build both of them

That M1 is still making me confused and I'm worried if I buy a wrong one or one not good enough.

The PMOSFET (Q1) shown in the schematic of post #38 would be a good choice for the PMOSFET M1 in Mike's circuit too:
(1) Available in a reasonably large pack to help soldering (TO-262)
(2) Low RDSS (on resistance)
(3) Low gate drive (voltage to turn them on)
(4) Withstand +-20V VGD (voltage before gate is damaged)
(5) Dirt cheap
**broken link removed**

spec

Rorut · May 4, 2016

audioguru said:
I am just guessing that "lift the voltage" is a bad translation of something. I am also guessing that the board does not limit overcurrent, it is able to pass 30A which might cause your shorted battery cells or your wiring to catch on fire.
My electric radio controlled model airplanes are powered from a 2-cells Li-Po battery. If I try a take-off from grass but the propeller gets stuck and the motor is stalled then its current goes very high. The protection circuit senses the overcurrent, causes the motor to squeal loudly for a moment to warn me then it shuts off. No fire. It is reset by turning down the throttle then back up.

But my 5A fuse will trigger if something goes bad with my load.
Anyone know of a PCB that can be trusted?

spec said:
The PMOSFET (Q1) shown in the schematic of post #38 would be a good choice for the PMOSFET M1 in Mike's circuit too:
(1) Available in a reasonably large pack to help soldering (TO-262)
(2) Low RDSS (on resistance)
(3) Low gate drive (voltage to turn them on)
(4) Withstand +-20V VGD (voltage before gate is damaged)
(5) Dirt cheap
**broken link removed**

spec

Thank you so much!
Are your circuit and choice of components above in earlier post final? Can I start order components?

spec · May 4, 2016

Rorut said:
Thank you so much! Are your circuit and choice of components above in earlier post final? Can I start order components?

No sweat Rorut,

Yes, the circuit and parts list have been updated and are now complete. I have checked the circuit functioning a few times now, in theory that is.
Bear in mind though, that the circuit is a paper design and has not been prototyped, but I am reasonably confident it will work OK- it does not use any techniques that are new to me- famous last words.

spec

Rorut · May 7, 2016

spec said:
2016_05_04 Issue 02.02

Here is the LiIon battery voltage cut off circuit that I mentioned previously:

View attachment 99300

ERRATA
(1) Delete C4
(2) Change C3 to 22uF 25V ceramic type (no leakage current)
(3) Change R4 from 750K to 82K
(4) Change R3 from 1M5 to 2M

NOTES
(1) N1 is a low current (1uA) comparator with a CMOS push pull output
(2) ZD1 is a 2.5V low current (1uA) precision (+-0.2%) Zener diode
(3) R5/R4 provide 100mV hysteresis per battery (3.1V and 3.2V) to take care of battery rebound.
(4) RV1 sets the cut off voltage to 3.1V per cell and can be adjusted to give +-400mV variation in cut off voltage
(5) The circuit layout and routing of lines is important and should be as shown on the schematic to maintain accuracy and reduce the likelihood of frequency instability.
(6) The capacitors are for decoupling to assist frequency stability and have no function in regard to the basic circuit operation. They should be physically as shown on the schematic.
(7) R1 is a gate stopper to prevent the PMOSFET from oscillating at a high frequency (not peculiar to this circuit) and should be mounted on the PMOSFET gate pin. R1 plays no part in the basic circuit function.
(8) The total current drain of the circuit is, 3uA while cut on and 4uA while cut off

PARTS LIST

Hi,
Can not find TLV370P on mouser site?
Same with mikes LM431. Many different things came up on search

Thanks

spec · May 7, 2016

Rorut said:
Hi,
Can not find TLV370P on mouser site?
Same with mikes LM431. Many different things came up on search

Thanks

Hy Rorrut,

Just open the attached pdf file under 'Parts List' in post #38 and click on the links for each component. The links take you to the product listing on the Mouser web site. The trouble is that the manufacturer's have gone mad with their part numbers: endless strings on letters and numbers, with no structure. MOSFETs are some of the worst in this respect and for micrcontrollers you need to write a book to get the right part.

Here is a link for the LM431: https://www2.mouser.com/ProductDeta...LM431ACZ/?qs=sGAEpiMZZMvAvBNgSS9Lqn4E3LoDYvrk
The LM431 comes in three precisions: +-0.2%, +-0.5%, and +-1%.
Always get the +-0.2% version- they are around the same price as the others, besides which all LM431s are dirt cheap and are widely used. The LM431 also comes in various packs- I have linked to the TO92 thru hole version which will be easier to handle.

If you have any further problems just post.

spec

kinarfi · May 7, 2016

I decided to take a look at both circuits to see what the differences I could see, Mine is in the left box, the one Spec mentioned is right box.
As stated before, the switches are for simulation purposes. The main difference I found was that I monitor the voltage after the switching FET and once below cut off, there is nothing to monitor until reset, plus it seems that just turning the battery on does NOT supply the load, it has to be reset. Spec's design monitors the battery and shuts off if the voltage gets below cut off and is held off by the R8 feed back resistor, to reset it, you just turn the battery off and back on. Mine had a battery current draw of 1.27734µA & 143.179mA load when off, Spec's had a battery current draw of 5.46829µA and 407.2µA load when off, I can't figure out how the load current was more than the battery current, must be a Spice issue of some sort.

spec · May 7, 2016

Hy kinarfi,

There seems to be something amiss with the spice simulation- not unusual. You do know that the comparator is rail to rail output and over and under the rails input.

The principle of the circuit in post #38 is that the cut off circuit (COC) is connected to the battery pack all times. When the voltage drops to 12.4V (3.1V per cell) the Schmidt trigger flips and its output goes to the positive supply line. This turns the PMOSFET off so that the load no longer drains any more current from the batteries. This action sets the turn on threshold of the Schmidt trigger to 12.8V (3.2V per cell) to account for any battery rebound (voltage recovery off load) and prevent chattering.

When the battery bank is charged and the the voltage reaches 12.8V the Schmidt trigger flips again and turns the PMOSFET on. There is no need for a manual reset.

As I said before, the current consumption is 3uA on and 4uA off.

spec

bountyhunter · May 7, 2016

Rorut said:
But my 5A fuse will trigger if something goes bad with my load.
Anyone know of a PCB that can be trusted?

I wonder if you could steal one out of an old Sony battery pack like for their camcorders. They had built in over current protection and automatic low voltage cutoff built into the PC inside the pack. Also had overvoltage disconnect so they could not be overcharged.

Rorut · May 7, 2016

bountyhunter said:
I wonder if you could steal one out of an old Sony battery pack like for their camcorders. They had built in over current protection and automatic low voltage cutoff built into the PC inside the pack. Also had overvoltage disconnect so they could not be overcharged.

Good idea! Will try find an old 4s pack somewhere

Rorut · May 8, 2016

spec said:
Hy Rorrut,

Just open the attached pdf file under 'Parts List' in post #38 and click on the links for each component. The links take you to the product listing on the Mouser web site. The trouble is that the manufacturer's have gone mad with their part numbers: endless strings on letters and numbers, with no structure. MOSFETs are some of the worst in this respect and for micrcontrollers you need to write a book to get the right part.

Here is a link for the LM431: https://www2.mouser.com/ProductDeta...LM431ACZ/?qs=sGAEpiMZZMvAvBNgSS9Lqn4E3LoDYvrk
The LM431 comes in three precisions: +-0.2%, +-0.5%, and +-1%.
Always get the +-0.2% version- they are around the same price as the others, besides which all LM431s are dirt cheap and are widely used. The LM431 also comes in various packs- I have linked to the TO92 thru hole version which will be easier to handle.

If you have any further problems just post.

spec

Thanks Spec,
But some links seems to be broken and when I try to copy paste, destinations does not work. Sorry for asking about such elementary questions

spec · May 8, 2016

Rorut said:
Thanks Spec,
But some links seems to be broken and when I try to copy paste, destinations does not work. Sorry for asking about such elementary questions

Hy Rorut,

I will sort out the links.

No need for apology- Swedish people are obviously very polite.

spec

spec · May 8, 2016

Hi again Rorut,

Every component link in the attached pdf file work fine this end.

If you are using a Microsoft Windows computer, you may have to open your browser on the home page first, in my case Firefox browser and Google home page. Then open the pdf in Adobe Reader and for each link hold down the Ctrl key and click and release the left mouse button with the cursor on the link in the pdf document. Your browser should display the Mouser page for each related component. You may have to minimize your pdf reader each time to see your browser window.

If you still can't get the links to work, don't worry just tell me about your machine, operating system, browser, home page, and pdf reader and I'm sure we can work something out. May be your computer's security is blocking access.

spec

kinarfi · May 8, 2016

kinarfi said:
View attachment 99397
I decided to take a look at both circuits to see what the differences I could see, Mine is in the left box, the one Spec mentioned is right box.
As stated before, the switches are for simulation purposes. The main difference I found was that I monitor the voltage after the switching FET and once below cut off, there is nothing to monitor until reset, plus it seems that just turning the battery on does NOT supply the load, it has to be reset. Spec's design monitors the battery and shuts off if the voltage gets below cut off and is held off by the R8 feed back resistor, to reset it, you just turn the battery off and back on. Mine had a battery current draw of 1.27734µA & 143.179mA load when off, Spec's had a battery current draw of 5.46829µA and 407.2µA load when off, I can't figure out how the load current was more than the battery current, must be a Spice issue of some sort.

spec said:
Hy kinarfi,
There seems to be something amiss with the spice simulation- not unusual. You do know that the comparator is rail to rail output and over and under the rails input.
When the battery bank is charged and the the voltage reaches 12.8V the Schmidt trigger flips again and turns the PMOSFET on. There is no need for a manual reset.

As I said before, the current consumption is 3uA on and 4uA off.

spec

One important difference between our designs is the battery we are protecting, you are protecting four Panasonic NCR3400 batteries, I am protecting a truck battery with 850 Cold Cranking Amps, so I'm not so concerned with current draw.
I do like the Schmidt trigger approach and will use it on my next battery protection project, the last one was removed when I sold the camper because I didn't think the new owner wanted to have to open the hood and push a tiny tactile button to listen to the radio (on occasion).
Sorry that the Spice file didn't work, I do have a tendency to modify .asy and .sub files to suit my needs, hope you were able insert items to make the .asc file work. If you would like, I would be glad to make sure my Battery Voltage Dropout 14v #2 .asc file has 'universal' components and re post it.
Thanks for your information,
Jeff

spec · May 8, 2016

kinarfi said:
One important difference between our designs is the battery we are protecting, you are protecting four Panasonic NCR3400 batteries, I am protecting a truck battery with 850 Cold Cranking Amps, so I'm not so concerned with current draw.
I do like the Schmidt trigger approach and will use it on my next battery protection project, the last one was removed when I sold the camper because I didn't think the new owner wanted to have to open the hood and push a tiny tactile button to listen to the radio (on occasion).
Sorry that the Spice file didn't work, I do have a tendency to modify .asy and .sub files to suit my needs, hope you were able insert items to make the .asc file work. If you would like, I would be glad to make sure my Battery Voltage Dropout 14v #2 .asc file has 'universal' components and re post it.
Thanks for your information,
Jeff

Hy Jeff,

Yes, we have designed for two different requirements. Now that you have explained your design objectives I can better understand your circuit. Afraid I rarely use simulations except for logic arrays and RF work where the component models are more accurate. I must down load LTSPICE some time and learn how to use it. By the way, Mike's TL431 circuit also has hysteresis and is much simpler if you are not too worried about extremly low current drain.

The OP is planning on building both circuits so it will be interesting to see how they turn out.

Thanks for your info too- as i have said many times before, I always learn something new from other designers.

Chuck

Rorut · May 8, 2016

spec said:
Hi again Rorut,

Every component link in the attached pdf file work fine this end.

If you are using a Microsoft Windows computer, you may have to open your browser on the home page first, in my case Firefox browser and Google home page. Then open the pdf in Adobe Reader and for each link hold down the Ctrl key and click and release the left mouse button with the cursor on the link in the pdf document. Your browser should display the Mouser page for each related component. You may have to minimize your pdf reader each time to see your browser window.

If you still can't get the links to work, don't worry just tell me about your machine, operating system, browser, home page, and pdf reader and I'm sure we can work something out. May be your computer's security is blocking access.

spec

Hi again and thank you very much!
I´m using both PC and Mac. Links worked if I downloaded the file. Went wrong in browser mode. Don´t know why.
I saved my shopping carts and here is the links. Before I buy. Do I now have the correct components?
https://www.mouser.se/ProjectManager/ProjectDetail.aspx?AccessID=8146b75e8d

And do I have correct components for MikeMls circuit:
https://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=4fe5926fed

spec · May 8, 2016

Hy Rorut,

This is getting exciting- actually ordering components.

My Circuit

(1) The PMOSFET should be this one (on the parts list I had written DMP4051 instead of DMP4015, but the link was correct):
https://www.mouser.co.uk/ProductDetail/Diodes-Incorporated/DMP4015SK3Q-13/?qs=sGAEpiMZZMshyDBzk1/Wi%2bpE1VGhjkFSh2niAR9qOtRSgJOsvgBhLA==

(2) The specified 22uf is out of stock and a new component but you can substitute this one which is currently in stock:
https://www.mouser.co.uk/ProductDetail/TDK/FK22X7R1E226M/?qs=sGAEpiMZZMt3KoXD5rJ2N48tYEMqcp4x2%2bhIxnyZw%2bU=

Mike's Circuit

(1) The 1K trim pot is OK electrically, but it would probably be easier to adjust if it was vertical like the 1M trimpot specified for my circuit, so I would recommend this:
https://www.mouser.co.uk/ProductDetail/Bourns/3296W-1-102LF/?qs=sGAEpiMZZMvygUB3GLcD7sSg8po3Zpo3LIzcbYgTi3o=

(2) PMOSFET as for item #1 above for my circuit

Otherwise both Mouser shopping lists look OK

spec

Rorut · May 8, 2016

spec said:
Hy Rorut,

This is getting exciting- actually ordering components.

My Circuit

(1) The PMOSFET should be this one (on the parts list I had written DMP4051 instead of DMP4015, but the link was correct):
https://www.mouser.co.uk/ProductDetail/Diodes-Incorporated/DMP4015SK3Q-13/?qs=sGAEpiMZZMshyDBzk1/Wi%2bpE1VGhjkFSh2niAR9qOtRSgJOsvgBhLA==

(2) The specified 22uf is out of stock and a new component but you can substitute this one which is currently in stock:
https://www.mouser.co.uk/ProductDetail/TDK/FK22X7R1E226M/?qs=sGAEpiMZZMt3KoXD5rJ2N48tYEMqcp4x2%2bhIxnyZw%2bU=

Mike's Circuit

(1) The 1K trim pot is OK electrically, but it would probably be easier to adjust if it was vertical like the 1M trimpot specified for my circuit, so I would recommend this:
https://www.mouser.co.uk/ProductDetail/Bourns/3296W-1-102LF/?qs=sGAEpiMZZMvygUB3GLcD7sSg8po3Zpo3LIzcbYgTi3o=

(2) PMOSFET as for item #1 above for my circuit

Otherwise both Mouser shopping lists look OK

spec

Of course
Really fun doing this!

Updated baskets.
I think I need replacements for 3 resistors on backorder?
Any suggestion?
Specs:
https://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=81726e2750

Did components for Mikes circuit look ok?
Mikes:
https://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=4fe5926fed

spec · May 8, 2016

Yeah, Mikes circuit parts list did look OK, except for comments. See post #57

Here is a link for a replacement 10M resistor that is in stock: https://www.mouser.co.uk/ProductDetail/Vishay/HVR3700001005FR500/?qs=sGAEpiMZZMukHu%2bjC5l7YVAlsJphHgNpW1YXoSkoLRM=

Both revised lists look OK now

spec

Rorut · May 9, 2016

Everything with order is perfect now except that delivery costs 25£ and components around 12£.
I'm not stingy or so but that's ridiculous. Small parts like that can fit in an envelope.

Normally I order from this site https://www.electrokit.com/en/ here in Sweden but they dont have all of that parts from the list. Comparator, mosfet, diode...

I guess I'm out of options and have to proceed with mouser anyway, but it hurts

Cut off voltage lithium battery?

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