Smart Switch V4 "Intelligent low voltage cutoff switch"

[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 905 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 820 times

Here it is connected to the Smart Switch

DSC00035.JPG (59.72 KiB) Viewed 820 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 820 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 820 times

DSC00053.JPG (41.49 KiB) Viewed 820 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.

[docnjoj]

Hey Kin
Can the switch be reprogrammed off the bike with just the serial cable and laptop or does it need the 5 volts from the bike battery?
otherDoc

[kfong]

Once you plug in your bike battery, you have power for the Smart switch to communicate to your laptop. Just plugging in the laptop alone won't do anything. If you have room on your recombant, you could even monitor the status as you ride or capture the data and look it later.

Hey Kin
Can the switch be reprogrammed off the bike with just the serial cable and laptop or does it need the 5 volts from the bike battery?
otherDoc

[docnjoj]

Thanks Kfong! Looking good!
otherDoc

[kfong]

Here are pics of one of two scooters I build for my nieces, ages 10 and 13. I used the Smart Switch so it would be easy for them to operate it. Without it, I'm pretty sure I would be replacing batteries. I picked up a simple charger for them to just plug in when they need to charge it. Basically it’s maintenance free.

I ended up modifying the scooters as well. I removed and replaced the original controller and throttle. I picked up these scooters used so the batteries were already bad. The throttle was basically an on/off control. They now have a true linear throttle. I kept the voltage near 24volts. I didn’t want it too fast for them. Using A123 cells. The fuel gauge meter actually measures true amp hour usage. I had to keep it simple; a meter similar to a gas gauge was used. When it reaches half way, they know that they need to turn around. This was all done on the Smart Switch. I am currently working with an upgraded processor with more memory so I can offer these features. My sister just picked up a smaller version for my nephew for me to mod. The kids really enjoy riding them.

[docnjoj]

I really like that battery meter! Can it be programmed through the Smart Switch for various voltage levels?
otherDoc

[kfong]

The meter has only 10 positions. It would not be very good for voltage measurements since it's way too coarse. What would you need the voltage levels for?

I really like that battery meter! Can it be programmed through the Smart Switch for various voltage levels?
otherDoc

[docnjoj]

The meter has only 10 positions. It would not be very good for voltage measurements since it's way too coarse. What would you need the voltage levels for?

I really like that battery meter! Can it be programmed through the Smart Switch for various voltage levels?
otherDoc

So my wife doesn't get stranded like she has a few times. The Smart switch arrived safe and sound with instructions. Thanks Kin! Tomorrow I will set it up to do a test of the 6 Fatpacks using the cutoff. I will power the Wattmeter with a 9 volt walwart so it doesn't lose the LVC numbers and use my hotplate as resistance. Thanks again for this wonderful device, kfong!
otherDoc

[kfong]

That was the whole reason I put that meter on the scooters. You really don't need to measure voltages, just amp hour capacity. Once you enter in the actual battery capacity, a current meter counts down the amp hrs left. Same as a wattmeter. I display the ratio, so the meter works exactly like a fuel gauge on your car. If the meter is half way, you have exactly half capacity left. When you are near empty, I have the fuel gauge flashing. You treat it no different than you car's fuel gauge. When you power down it remembers the setting and when you charge it up, it resets it to full. My 10 and 13 year old nieces find this much easier to understand than voltages or watts. I will be offering this as an add on to the Smart Switch maybe sometime this winter when I get more time to work on it. All it requires is a current shunt that plugs into the Smart Switch. It already works, but I have no room on the current micro without getting rid of the menu system. The good news is I have the upgraded micro and it gives me more code space to implement all the cool features I want to add.

I'm glad you got the smart switch. I'll post more info on the advance menu I installed. This is only useful for those doing battery testing on single packs. It is to reduce the sag delay, which is defaulted to 20 seconds. With your bank of 6 cells, the sag delay is fine. If you are only testing a single pack, you would decrease the sag delay or increase the low level cut off. The advance menu isn't really needed until I add more features.

The meter has only 10 positions. It would not be very good for voltage measurements since it's way too coarse. What would you need the voltage levels for?

I really like that battery meter! Can it be programmed through the Smart Switch for various voltage levels?
otherDoc

So my wife doesn't get stranded like she has a few times. The Smart switch arrived safe and sound with instructions. Thanks Kin! Tomorrow I will set it up to do a test of the 6 Fatpacks using the cutoff. I will power the Wattmeter with a 9 volt walwart so it doesn't lose the LVC numbers and use my hotplate as resistance. Thanks again for this wonderful device, kfong!
otherDoc

[docnjoj]

That "sag delay" is really "smart". Her Ping maybe has 3-5 seconds before the BMS shuts down and needs to be reset! Very kool!
otherDoc

[kfong]

Thanks, that was one of the things that really frustrated me about a direct cut off when I knew the battery was fine but just needed some recovery time, due to extreme acceleration or hill climb. It allows you to end up very close to your low level cut off setting. Without allowing you to go too crazy. It resets when the voltage recovers, and waits for another low voltage to trip it. If you just climbed a hill, you might not hit that point for another mile or more. You can set this value to you personal preference. I will post info on it soon, but I find 20 seconds to be fine. Too long of a delay and you risk going past your low voltage cutoff when it totally shuts off.

That "sag delay" is really "smart". Her Ping maybe has 3-5 seconds before the BMS shuts down and needs to be reset! Very kool!
otherDoc

[docnjoj]

And here it is in action! Set up for testing the capacity of the 6 Fatpacks in //. Should be about 10-12 AH. We will see as the pull down current from the hotplate is only 4 amps. Oh yeah that is IC57's harnass! Works like a charm! Duh! I just realized I coulda put the meter in series with the batts and they would have powered it. Oh well I am used to this setup and it works fine.
otherDoc

IMG_0286.JPG (104.93 KiB) Viewed 926 times

[geoff57]

Hi
Good test setup doc, I use a bank of 55W car head lights instead of a hotplate 8 lights configured 2P4S it's good for up to 12S LiPos changing to 1P 8S should be good for 24S LiPos, in it's present configuration it pulls just over 9 amps it's very bright but good for testing batteries with which is the reason I built it.
Kfong iliac your switch just think it is overkill for me as I use the LVC boards I make , it's good to see more gizmos appearing on ES keep your ideas coming.
Geoff

[kfong]

Nice setup David, I recognize those inline tube connectors. Didn't think I would ever come across those ever. As I recall, they use aluminum as the center contacts as you compress them. I would recommend getting rid of them and switching to all Andersons. Because they are aluminum they make terrible contacts and introduced high contact resistance, this can cause hotspots in those connectors. If you have a second hotplate you could increase your current drain by paralleling them. I've been working on my own battery load from a portable electric heater. I'll post pictures of my setup when I get it finished.

[docnjoj]

Hi Kin
It looks like the "Auto off" went off in an hour even though the batteries still read 38 volts. Is this something I need to reset since when I hit the start button again it started up with 38 amps?
otherDoc.

[kfong]

I just realized your bench test does not simulate actual ebiking. With a stiff battery pack the voltage stays constant. Smart Switch thinks the bike is just parked. All it needs is a little fluctuation in the voltage to reset the turn off delay. If you had the serial port hooked up you will see it telling you standby is in effect. The time out I entered was 1 hour. You can increase the timeout to a much larger value so it won't interfere with your battery testing. If you used a smaller capacity pack, it will see the voltage actually change during that hour. You can just turn it back on to continue testing, but if there is a lot of capacity left and the voltage does not change in an hour then auto shut off will take over. Your 4 amp load doesn't tax the batteries like your bike motor would.

I originally had it monitoring the current, but since the standard setup does not have current monitoring available, I had to use voltage as my only indicator to know if the bike is parked. During normal use, the voltages fluctuate quite a bit due to acceleration and hill climbing.

Hi Kin
It looks like the "Auto off" went off in an hour even though the batteries still read 38 volts. Is this something I need to reset since when I hit the start button again it started up with 38 amps?
otherDoc.