Smart Switch V4 "Intelligent low voltage cutoff switch"

[kfong]

It would work but the idea is to have this as you main cut off. I used my dewalt packs for testing, but it has an internal bms already, so it becomes redundant. Also the dewalt bms has a steady drain if left in the on state, so even with their bms it's not as good of a solution as having the smart switch in full control.

Is your fatpacks wired directly to the batteries or are they still factory? If they are still factory, I would set the smart switch to a lower cutoff and let the fatpack bms protect the cells. You still gain auto shut down, no sparks and emegency off switch. You can also set the cutoff higher, but you won't be using the full capacity. Come to think of it if you set it to the same cutoff, as soon as one pack goes down. Smart switch will do a complete shut down anyways. So the answer is Yes.

No problem building one. I'll set one aside for you.

Hey Kenny
Could I use this switch for my 36 volt Konion setup with 6P Fatpacks? I think it is genius and I want one. I would prefer that you built it since my eyes are getting bad!
otherDoc

[Alan B]

Nice project. I've been thinking about making a similar unit myself with a keyswitch.

A question. It looks like you may be using a latching relay. It is my understanding that physical shock can cause a latching relay to switch. Is that a potential problem here? Hitting a pothole on a bike might turn the power on or off if the board was mounted firmly to the frame in any way?

[kfong]

I trail ride, it has not been a problem, and I've mounted it directly to the frame, which had only front shocks and have been put in scooters with no suspension. If it can take the abuse I put it through I'm sure you won't make it fail. These have low mass and I suspect spring leaf tensioned. They are not the big relays you might be thinking of. The smart switch has been working for over a year on my cyclone build. I just needed more for other projects. Lots of uses for this switch. Just recently picked up a dc/dc supply Ypedal, pointed out. Will be hooking it up to my car battery and Hyperion charger to charge my spare pack while I trail ride, but I don't want to over discharge the car battery in case it's low. Smart switch to the rescue, same with my RC stuff.

Nice project. I've been thinking about making a similar unit myself with a keyswitch.

A question. It looks like you may be using a latching relay. It is my understanding that physical shock can cause a latching relay to switch. Is that a potential problem here? Hitting a pothole on a bike might turn the power on or off if the board was mounted firmly to the frame in any way?

[Alan B]

Good to hear that you've tested it and there is no problem.

I trail ride, it has not been a problem, and I've mounted it directly to the frame, which had only front shocks and have been put in scooters with no suspension. If it can take the abuse I put it through I'm sure you won't make it fail. These have low mass and I suspect spring leaf tensioned. They are not the big relays you might be thinking of. The smart switch has been working for over a year on my cyclone build. I just needed more for other projects. Lots of uses for this switch. Just recently picked up a dc/dc supply Ypedal, pointed out. Will be hooking it up to my car battery and Hyperion charger to charge my spare pack while I trail ride, but I don't want to over discharge the car battery in case it's low. Smart switch to the rescue, same with my RC stuff.

Nice project. I've been thinking about making a similar unit myself with a keyswitch.

A question. It looks like you may be using a latching relay. It is my understanding that physical shock can cause a latching relay to switch. Is that a potential problem here? Hitting a pothole on a bike might turn the power on or off if the board was mounted firmly to the frame in any way?

[K-ray]

I too am intrigued by this simple solution cuz I liike to play with different cell counts
So what would you recommend for cut-off (voltage per cell) for both Lipo and LiFePo4 to keep in the "safe" range?
Thanks
And nice work

[kfong]

For Lipo's I've been using 3.5volts, for Konions 3.3volt and for LifePo4 2.85volts

I too am intrigued by this simple solution cuz I liike to play with different cell counts
So what would you recommend for cut-off (voltage per cell) for both Lipo and LiFePo4 to keep in the "safe" range?
Thanks
And nice work

[docnjoj]

Hey Kenny
Thanks for the response. My Fatpacks have the BMS removed and it is permenently attached to the charger so I charge with the Bosch charger to 6P at about 41volts and about 4 amps. It takes a while to charge but my main problem is the LVC and your switch seems to solve that. When you post programming details that should do it for me in understanding how it works.
otherDoc

[o00scorpion00o]

Hi kfong,

So basically this is like controller lvc, it will switch off or throttle the power based on pack voltage rather than individual cell voltage ?

Can the throttle on off switch be used to switch power on and off to the controller ? that would be very useful.

Motor temp monitoring would be very very convenient , when the new chips become available would we be able to just replace the old one for the new features ?

Also, would you be able to install them in some kind of enclosure ? it would be handy for protecting it when throwing it in a battery bag!


Mark

[kfong]

Yes, it's like the controllers LVC setting. It measures pack voltage and cuts off based on the voltage you determine. But unlike the motor controller, the Smart Switch is a complete power off. No standby current or small battery drain to worry about. It basically protects your battery from ever going too low. Whereas a BMS can still damage a pack due to the constant battery drain even when off, especially if the pack is depleted and sitting around for a while. SImiliar problem if you forget to shut off your ebike. The standby current can take out a drained pack in a few days or less.

The power off switch is just a logic level pin shorted to ground. You would need to see how the throttle on off switch functions to see if it uses similar actions. If it is similiar then they can be paralleled, but this is more for those who are comfortable around electronics.

It will be a while for the new chip to be on line. Apparently my development tools are not up to speed. I have the new chip to play with, but it's useless to me till I find a way to program it. Looking into other compilers at the moment. It would be just replacing the old chip with the new one for the upgraded features. Lack of code space is the only reason I can't offer these features at the moment. I would have to throw out the user interface and have the chip customized to your system to add stuff. For now I think the standard setup has a lot going for it.

There are 4 mounting holes on the board to mount on standoffs. I still have to post more details such as dimension and parts list. Just been busy lately. I might offer a custom CNC enclosure, I need to make one for myself. Really any enclosure would work since the power leads and switches are brought out.

Hi kfong,

So basically this is like controller lvc, it will switch off or throttle the power based on pack voltage rather than individual cell voltage ?

Can the throttle on off switch be used to switch power on and off to the controller ? that would be very useful.

Motor temp monitoring would be very very continent, when the new chips become available would we be able to just replace the old one for the new features ?

Also, would you be able to install them in some kind of enclosure ? it would be handy for protecting it when throwing it in a battery bag!


Mark

[o00scorpion00o]

Hi kfong,

Thank's for the reply, yeah that's all my switch does is short the two pins so that should work fine, it would be cool to have an on off switch without having to pull apart the andersons every time!

If you could build them and install then in an enclosure and have all relevant wires coming out of the box, I think that would be cool!

The motor temp monitoring would get a real interest I'm sure, it would help save a lot of motors from death!

The only problems would be installing the wires through the axle.

Mark

[kfong]

I finally updated the parts list and what is needed from Digikey. I had to increase the price of a built board to $135. I'll try to get post of a build with pictures when time allows. For now the standard version of the Smart Switch is what I will be selling. I am currently playing with the new chip, but really don't have much time to add more functions till later this fall when weather gets too cold to ride.

[kfong]

I had time to install the new board on my cyclone build. It’s nice having the ability to use different cell chemistry. Here is pics of my old setup using Konions 10S 8P 12ahr at 40volts on the bottom picture and the new pack 12S 2P 10ahrs lipo’s at 50volts above. I really like the Cyclone at 50 volts. I have a smart switch for each pack. That way I don’t have to worry about the batteries. I’m only using a cheap bike computer to get me an idea on how far I can go. I’ve setup the new board with only 3 Fets. I’ve been riding it hard and have not had any problems. This is in a closed plastic box without vents. When I get a chance, I’m going to try it with one Fet and maybe a small heat sink or a metal box.

Packs.jpg (95.04 KiB) Viewed 926 times

I’ve setup 2 friends with the same rack system. When they borrow my packs with the smart switch, I’m no longer concerned that they will damage them. Even though one of them has a Cycle Analyst, his pack is a 10S setup. I know he will end up forgetting to change his low voltage setting and burn up my pack if I didn’t have the smart switch installed.

Here is how I have it on my bike, I use velcro on the bottom of the box to attach it to the rack. Holds up pretty good even in the trails since it's rather light.

setup on bike.jpg (108.27 KiB) Viewed 926 times

bike with pack.jpg (136.92 KiB) Viewed 926 times

[docnjoj]

Hey Kin I need to ask a few dumb questions. Is there a cable needed to plug that DB9 into my laptop? Also the screen capture is really to small to read for me . Is there any way a list of steps could be made to set up the switch? Finally which port do I plug the interface into on my laptop? Thanks for being understanding regarding my ignorance.
otherDoc
Edit: What is the "scale factor" used for?

[docnjoj]

I just blew up the video to 400% and could see most of the changes but unfortunately I have Windows 7 and it is different than the video shows. Will the programming work with the newer Windows? I did a search for Hyperterminal and go no results.
otherDoc

[Alan B]

Nice setup. Keeping the LVC with the pack works out well.

[kfong]

I tend to forget that a lot of newer computers are doing away with all the different ports and going with USB. You would need a USB to Serial adaptor. A search on Google shows it can be found even at Wal-Mart.
http://www.google.com/products/catalog? ... UBEPMCMAI#
Older laptops and computers have this port and all you will need is just a standard serial cable.

If you plan to keep only one configuration. I can preset the parameters for you and you won't need to bother with a serial cable or interface board. Then it would just be plug and play. All I would need is what voltage cutoff you want, the pack size and chemistry so I can double check your choice and how long before you want the auto off feature to shut down the bike. I recommend 60 mins.

The scale factor is used to calibrate the A/D more precisely. But it is mainly needed due to the voltage range. Here is a simple spreadsheet to tweak RH and RL values for those who have a better understanding of analog to digital conversion.

AtoD Calculator.xls

(9.5 KiB) Downloaded 30 times

But it is easier to just stick with the two ranges I’ve given.

If your pack is between 12 - 55 volts your scale factor will be .0537
If your pack is between 56-105 volts your scale factor will be .1027

Actually I’m glad you brought up the scale factor. I’m revising the parts list to make it easier, and just have 2 default ranges. For those who know how to use the spreadsheet and have accurate meters. They can modify RH and RL values.

I will try to get better documentation as I get more questions. This is usually the part that I tend to get lax on till someone brings up a detail that I’ve left out.

Hey Kin I need to ask a few dumb questions. Is there a cable needed to plug that DB9 into my laptop? Also the screen capture is really to small to read for me . Is there any way a list of steps could be made to set up the switch? Finally which port do I plug the interface into on my laptop? Thanks for being understanding regarding my ignorance.
otherDoc
Edit: What is the "scale factor" used for?

[kfong]

Looks like Hyperterminal is not provided with newer operating systems. You can copy it from older systems if you have it. Any simple terminal program should work. I did a search and found a program called putty.
http://www.chiark.greenend.org.uk/~sgta ... nload.html
Just download the program putty.exe and run it.
Here is how to set it up.
http://www.youtube.com/watch?v=YCNh1ByYzw4

Here is what the setup menu looks like in Hyperterminal, it will look similar in any other terminal program.

Setup menu.jpeg (46.04 KiB) Viewed 902 times

I just blew up the video to 400% and could see most of the changes but unfortunately I have Windows 7 and it is different than the video shows. Will the programming work with the newer Windows? I did a search for Hyperterminal and go no results.
otherDoc

[docnjoj]

That does it! I'll paypal my money for the works if you give me a total with the box and the buttons and the serial adaptor. Ill send a PM. Thanks for all the necessary info!
otherDoc

[docnjoj]

Hi Kin
I've been trying Putty but I can't see the screens again. I think it says Com1, speed 3600, Default settings on the first screen but when I try to load it says "Can't find host". Do I need to have the switch hooked up before I try to set up Putty?
Thanks
David

[kfong]

You might try a different com port. I think they can go up to 4 ports. Your hardware setup page in windows would give you a clue on the ports, but it's just as easy to try all 4 ports. You don't need anything connected for the port to operate.
Com1-Com4

[chroot]

kfong- Do you still have these left over? I might need 2 of these for my ebike and cargo bike.

[kfong]

Yes, just pm me on what you require.

kfong- Do you still have these left over? I might need 2 of these for my ebike and cargo bike.

[docnjoj]

You might try a different com port. I think they can go up to 4 ports. Your hardware setup page in windows would give you a clue on the ports, but it's just as easy to try all 4 ports. You don't need anything connected for the port to operate.
Com1-Com4

Thanks Kin. I'll play with it a bit.
otherDoc

[kfong]

Here are build pics of the Smart Switch. I took a bunch of pics as during one of the builds.

To make things easier during the build. Install the socket and IC's first since you can lay them flat.

[kfong]

Docnjoj, asked for a complete plug and play setup. I incorporated the serial board with the Smart Switch. Since the serial port actually requires only 5volts to operate. I removed the original 5volts voltage regulator and tapped into the 5volt supply from the Smart Switch using the current connector labeled AMPS. The pins are marked as + and -, for the +5volts and Ground. Instead of using connectors, I find soldering more reliable. Here are pics of the custom CNC box I built using black ABS plastic.

DSC00030.JPG (37.26 KiB) Viewed 817 times

Here it is connected to the Smart Switch

DSC00035.JPG (59.72 KiB) Viewed 817 times

Installed in the custom CNC box I built using black ABS plastic. Serial board is mounted using locking nuts to prevent loosening.

DSC00039.JPG (58.98 KiB) Viewed 817 times

Black switch for ON, Red switch for OFF. Battery goes to the red and black Andersons, Controller to the white and blue.

DSC00046.JPG (37.9 KiB) Viewed 817 times

DSC00053.JPG (41.49 KiB) Viewed 817 times

The serial port will allow for easy parameter changes as well instant data monitoring. I plan to use this data port as a way to connect to an LCD display in the future.