Smart Switch V4 "Intelligent low voltage cutoff switch"

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Re: Smart Switch V4 "Intelligent low voltage cutoff switch"

Post by docnjoj » Oct 26, 2011 12:35 pm

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.
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E-bike stable at our house

Steintrike Mad Max full suspension trike rear Cute 100H going on: Whoops, Cute wheel broke but I fixed it.
Sun USX delta trike EbikeKit small geared front wheel sort of front suspension for wife

Agniusm/A123 AMP 20 36 volts on the Steini has been taken off.
2x16000 Multisport from HK now gone as they died after 2 years
New Luna 10S bottle battery 13.6AH now on mine
Relatively New 10S4Px2 for wife's bike giving 20ah @ 40 volts home made Panasonic from Tumich. BMS's rule.

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Re: Smart Switch V4 "Intelligent low voltage cutoff switch"

Post by geoff57 » Oct 26, 2011 1:15 pm

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

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Re: Smart Switch V4 "Intelligent low voltage cutoff switch"

Post by kfong » Oct 26, 2011 2:26 pm

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.

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Re: Smart Switch V4 "Intelligent low voltage cutoff switch"

Post by docnjoj » Oct 26, 2011 2:59 pm

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.
E-bike stable at our house

Steintrike Mad Max full suspension trike rear Cute 100H going on: Whoops, Cute wheel broke but I fixed it.
Sun USX delta trike EbikeKit small geared front wheel sort of front suspension for wife

Agniusm/A123 AMP 20 36 volts on the Steini has been taken off.
2x16000 Multisport from HK now gone as they died after 2 years
New Luna 10S bottle battery 13.6AH now on mine
Relatively New 10S4Px2 for wife's bike giving 20ah @ 40 volts home made Panasonic from Tumich. BMS's rule.

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Re: Smart Switch V4 "Intelligent low voltage cutoff switch"

Post by kfong » Oct 26, 2011 3:16 pm

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.

docnjoj wrote: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.
Last edited by kfong on Oct 26, 2011 3:43 pm, edited 4 times in total.

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Re: Smart Switch V4 "Intelligent low voltage cutoff switch"

Post by docnjoj » Oct 26, 2011 3:21 pm

Thanks Kin! I will get those old alloy squeeze connectors off and solder the connections to the Andersons. I get my serial cable friday so I will play with the program. I found an old Win 98 laptop in the closet so I can go serial to serial instead of attempting to use the USB to serial ports. The thing that I thought was a serial port on my newer computers was actually a 15 pin monitor port. Oh well!
otherDoc
E-bike stable at our house

Steintrike Mad Max full suspension trike rear Cute 100H going on: Whoops, Cute wheel broke but I fixed it.
Sun USX delta trike EbikeKit small geared front wheel sort of front suspension for wife

Agniusm/A123 AMP 20 36 volts on the Steini has been taken off.
2x16000 Multisport from HK now gone as they died after 2 years
New Luna 10S bottle battery 13.6AH now on mine
Relatively New 10S4Px2 for wife's bike giving 20ah @ 40 volts home made Panasonic from Tumich. BMS's rule.

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Re: Smart Switch V4 "Intelligent low voltage cutoff switch"

Post by kfong » Oct 26, 2011 3:28 pm

For now you could just keep turning it on. The wattmeter hasn't lost it's info with the way you have it set up.
docnjoj wrote:Thanks Kin! I will get those old alloy squeeze connectors off and solder the connections to the Andersons. I get my serial cable friday so I will play with the program. I found an old Win 98 laptop in the closet so I can go serial to serial instead of attempting to use the USB to serial ports. The thing that I thought was a serial port on my newer computers was actually a 15 pin monitor port. Oh well!
otherDoc

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Re: Smart Switch V4 "Intelligent low voltage cutoff switch"

Post by docnjoj » Oct 26, 2011 3:42 pm

Will do Kin! It should only be 2 more times unless those Fatpacks become miracles.
otherDoc
E-bike stable at our house

Steintrike Mad Max full suspension trike rear Cute 100H going on: Whoops, Cute wheel broke but I fixed it.
Sun USX delta trike EbikeKit small geared front wheel sort of front suspension for wife

Agniusm/A123 AMP 20 36 volts on the Steini has been taken off.
2x16000 Multisport from HK now gone as they died after 2 years
New Luna 10S bottle battery 13.6AH now on mine
Relatively New 10S4Px2 for wife's bike giving 20ah @ 40 volts home made Panasonic from Tumich. BMS's rule.

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Re: Smart Switch V4 "Intelligent low voltage cutoff switch"

Post by docnjoj » Oct 27, 2011 2:39 pm

Testing is going fine. First run got 10.5 AH out and 12 in. I am cycling them 2-3 times to wake them up. I still think that Fatpacks are the best way to go for regular folks who don't want the complexity of a BMS. Just Kfongs Smart switch and the regular Bosch charger. I have 2 in parallel for 8 amp charge current. The cutoff is about 41 volts and is extremely repeatable. Good technology from America (Smart switch) and Germany Fatpacks and charger. I was luck and got the Fatpacks for $45 each delivered and $30 for each charger. Not so good prices 2 years later! That sucks!
otherDoc
E-bike stable at our house

Steintrike Mad Max full suspension trike rear Cute 100H going on: Whoops, Cute wheel broke but I fixed it.
Sun USX delta trike EbikeKit small geared front wheel sort of front suspension for wife

Agniusm/A123 AMP 20 36 volts on the Steini has been taken off.
2x16000 Multisport from HK now gone as they died after 2 years
New Luna 10S bottle battery 13.6AH now on mine
Relatively New 10S4Px2 for wife's bike giving 20ah @ 40 volts home made Panasonic from Tumich. BMS's rule.

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Re: Smart Switch V4 "Intelligent low voltage cutoff switch"

Post by kfong » Oct 27, 2011 4:35 pm

I'm glad it's working out for you. Here is my setup for testing light loads. I'm drawing close to 6 amps, but the 2 power transistors used get really hot so I keep the current limit down. The noise in the background is the fan cooling the transistors. I'm currently building a larger 600w load to test my ebike packs.
http://www.youtube.com/watch?v=tThlG3vt ... e=youtu.be

Pics of the setup
battery testing1.jpg
battery testing1.jpg (74.77 KiB) Viewed 1887 times
On the left screen my computer is displaying data from my Smart Switch, the right screen, tablet PC is graphing data taken from the Power Analyzer Watt-meter.
battery testing2.jpg
battery testing2.jpg (70.21 KiB) Viewed 1887 times
Here you can see I have the Smart Switch adjusted so it cuts off the battery just before the drop off point
battery test.jpg
battery test.jpg (84.55 KiB) Viewed 46 times
I've finished the 500 watt load, decided it needed it's own thread. Since I want input on building an even bigger one.
https://endless-sphere.com/forums/vi ... 14&t=33218


Some info on the 4110 FET, with 1 fet at 40 volts and 10 amp draw, the temp was only 80 deg. When pushed to 45volts at 560 watts the fet was 90-100 deg without a heat sink. Looks like you can get away with 1 on a 500 watt setup but should start to think about increasing the number once past 600w, but 3 is the most you need for most setups without needing a heatsink. When you start passing 2000w check the temps to see if you need another or you could use a heatsink instead, but that tends to increase your box dimensions. I'll try to get a larger load going to see how hot I can get the single fet without a heatsink.

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Re: Smart Switch V4 "Intelligent low voltage cutoff switch"

Post by isaac_alaska » Nov 01, 2011 3:43 pm

recieved mine in the mail yesterday, i need to solder the whole thing together. looks nice, and nice packaging!

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Re: Smart Switch V4 "Intelligent low voltage cutoff switch"

Post by jerrysimon » Nov 11, 2011 5:56 am

Hi as I have said these look pretty neat and I have expressed interest in a PM. I just wanted to clarify how this may have prevented my recent loss of two cells.

As explained in my main post in the battery forum I lost two cells one in each of a 2 * 6s1p pack in succession over a three week peiod. The pack was two years old and had done 500 charge cycles.

I am wondering how this unit might have avoided that given that when I measured the pack at rest 11 cells were around 3.2v and one had dropped down to below 1v ?

If it is recommened that the LCV is set to 2.75v/cell i.e. 33v for a 12s1p the pack then the above failure would still have happened as the pack would have been at 37v, or, am I missing the fact that it was at rest when I measured it and when actually using it the voltage sag would take the pack down to less than 33v ?

Ps I just found the real time (during the ride) Cell Log data I took when the pack failed and on the failing 6s1p pack, five of the six cells were at 3.15 when the bad cell went down to 2.0v i.e. this 6s1p pack voltage was 17.75v. If the other 6s1p pack was around 3.15v/cell (the all good cells would probably have been higher) i.e. 18.9v for the pack then the total 12s1p pack would be around 36.65v. So does that mean for 12s1p, A123 packs that the LVC should be set at 36-37v not 33v ?

In my case if it was set at 33v for the whole pack then its unlikely having the the Smart Switch V4 fitted would have prevented me losing the cell.

Regards

Jerry

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Re: Smart Switch V4 "Intelligent low voltage cutoff switch"

Post by kfong » Nov 11, 2011 9:21 am

For A123's, I usually set it for 2.75 volts per cell, when all cells are healthy you get proper cutoff. All cells decrease at a proportional rate. By not monitoring your packs you end up damaging the first cell or two when going below LVC. Once these are damaged your packs will no longer work as expected. Your 3.2 volts indicate more of a charged state than being empty. Your packs probably became unbalanced from earlier abuse.

Voltage sag plays a role, but you need to know the voltages soon after the sag to get a good indication of the packs resting voltage during use. Constant monitoring of the pack is easily done by the smart switch. it allows for sag so you don't get false readings and when it finally does cut off your packs should end up at 33 volts, with all cells balanced at 2.75 volts. You can tweak the LVC to obtain the final voltage depending on how stiff you battery pack is. In your case, you are running only one string of cells, not a very stiff pack. I would recommend changing the sag delay in the advance menu option to 10 seconds or less. The standard setup has a 20 second sag delay. Using only one string of cells means your capacity will drop very fast when near LVC. You have very little room for error. Perhaps even a 5 second sag delay is safer to begin with.

The whole point of a LVC is to avoid what just happened to your pack. Once your pack becomes unbalanced, the weakened cell has a tough time keeping up with the good ones and should be replaced.
jerrysimon wrote:Hi as I have said these look pretty neat and I have expressed interest in a PM. I just wanted to clarify how this may have prevented my recent loss of two cells.

As explained in my main post in the battery forum I lost two cells one in each of a 2 * 6s1p pack in succession over a three week peiod. The pack was two years old and had done 500 charge cycles.

I am wondering how this unit might have avoided that given that when I measured the pack at rest 11 cells were around 3.2v and one had dropped down to below 1v ?

If it is recommened that the LCV is set to 2.75v/cell i.e. 33v for a 12s1p the pack then the above failure would still have happened as the pack would have been at 37v, or, am I missing the fact that it was at rest when I measured it and when actually using it the voltage sag would take the pack down to less than 33v ?

Ps I just found the real time (during the ride) Cell Log data I took when the pack failed and on the failing 6s1p pack, five of the six cells were at 3.15 when the bad cell went down to 2.0v i.e. this 6s1p pack voltage was 17.75v. If the other 6s1p pack was around 3.15v/cell (the all good cells would probably have been higher) i.e. 18.9v for the pack then the total 12s1p pack would be around 36.65v. So does that mean for 12s1p, A123 packs that the LVC should be set at 36-37v not 33v ?

In my case if it was set at 33v for the whole pack then its unlikely having the the Smart Switch V4 fitted would have prevented me losing the cell.

Regards

Jerry

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Re: Smart Switch V4 "Intelligent low voltage cutoff switch"

Post by jerrysimon » Nov 11, 2011 10:54 am

Thanks for the comprehesive reply Kin, all that makes sense I think :oops:

Are you saying that if I discharge completly with your switch fitted it will power off at the set LVC of 33v and all cells will be balanced with a 2.75v reading ?

Getting 500 charge cycles from my pack is not bad given the abuse I obviously gave it over the two years. Now that I have replaced the two failed cells I wonder how long it will last. I guess I need to weigh up if to manually monitor/balance more, keep a few spare cells or go all out and get your clever little switch :roll:

PS This is how my setup is I wonder if your switch would fit in the pocket of my Brompton bag and replace the existing power switch. That switch must be taking quite a battering with the current surge when I first switch it on. Again something your switch would prevent 8)

Battery in left pocket, controller in right.

Image

Pocket open showing unbilical from from the bike to the bag.

Image

Sorry for all the questions :oops:

Regards

Jerry

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Re: Smart Switch V4 "Intelligent low voltage cutoff switch"

Post by teklektik » Nov 11, 2011 11:08 am

jerrysimon wrote:... Pocket open showing unbilical from from the bike to the bag.
JS- interesting connector pair - can you afford some details?
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Re: Smart Switch V4 "Intelligent low voltage cutoff switch"

Post by jerrysimon » Nov 11, 2011 11:28 am

teklektik wrote:
jerrysimon wrote:... Pocket open showing unbilical from from the bike to the bag.
JS- interesting connector pair - can you afford some details?
Sorry and I don't mean to hijack the thread. Its made by http://www.bulgin.co.uk/Products/GenPur ... ctors.html.

The unbilcal carries all my connections on this eight pole plug including three motor wires (each pin rated to 6 amps), throttle and cutout breaks. Enables me to seperate bike and bag to keep the whole thing portable.

Kin's switch would finish the whole project off perfectly :P

Regards

Jerry

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Re: Smart Switch V4 "Intelligent low voltage cutoff switch"

Post by kfong » Nov 11, 2011 11:46 am

The cycle life on the a123 is so high, I have yet to see one go bad on mine or my friends unless it's been abused. I've even used them on RC setups where we really task them. Seems like you have plenty of room for it. Not having a break down if it's your commute seems reason enough for me. At the very least you should install a LV alarm. Once your pack hits that point, being a single series pack, you have pretty much used up the capacity and need to disconnect since it's only 2 ahrs in useful capacity with very a small buffer left, even riding less than a block can push past whatever is left and cause damage.

Another solution is to add more capacity so you always have plenty left over before the next charge cycle.

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Re: Smart Switch V4 "Intelligent low voltage cutoff switch"

Post by jerrysimon » Nov 11, 2011 11:51 am

Many thanks Kin for the info and advice. Fitting a couple of LVAs is an option but its a hassle if I have to keep remembering to connect/disconnect them. As I said your solution is very neat and is fit and forget :D

I will mull it over and get back to you if I decide to go for one of your smart switches.

Regards

Jerry

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Re: Smart Switch V4 "Intelligent low voltage cutoff switch"

Post by lock22 » Nov 16, 2011 9:39 am

Hi kfong

been catching up on lots of threads, and your switch looks like the business for everyday use. I currently have a 48v lifepo4 system on a cyclone kit, as you, and am using the goodrum/fechter bmc, am happy with this apart from 2 areas, size and battery deconnexion. Your design answers both these questions but I do have a 3rd; being a mac user, the windows prog is going to cause a bit of bother. Any simple solution you may have is welcome, or I suppose I can borrow a pc if necessary?
and are your boards still available?

best wishes

Charlie

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Re: Smart Switch V4 "Intelligent low voltage cutoff switch"

Post by kfong » Nov 16, 2011 10:10 am

Hi Charlie,

Yes the boards are available.

The communication is just standard serial 9600 baud (8,n,1,z). Any terminal program with serial port access will work. I'm sure Mac has several freeware stuff you can look for. You might need a USB to serial port converter if your Mac does not have a serial port. If you just plan to use it on one setup, I can preprogram it for you.

I'm finding a lot of uses for this switch. I'm currently building a 12volt car starter out of A123's for the winter, incase of a breakdown. Since there are so many things I have around the house that run off of 12volts. I can leave them plugged in to it unattended and not worry about damaging the cells. This makes the 12v car starter a lot more useful.

lock22 wrote:Hi kfong

been catching up on lots of threads, and your switch looks like the business for everyday use. I currently have a 48v lifepo4 system on a cyclone kit, as you, and am using the goodrum/fechter bmc, am happy with this apart from 2 areas, size and battery deconnexion. Your design answers both these questions but I do have a 3rd; being a mac user, the windows prog is going to cause a bit of bother. Any simple solution you may have is welcome, or I suppose I can borrow a pc if necessary?
and are your boards still available?

best wishes

Charlie

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Re: Smart Switch V4 "Intelligent low voltage cutoff switch"

Post by Diamondback » Dec 27, 2012 5:54 am

PM sent :)

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Re: Smart Switch V4 "Intelligent low voltage cutoff switch"

Post by docnjoj » Jan 02, 2013 11:59 am

I've been using Kin's switch on my A123 pack and it helped me determine one cell was bad. It cut off early a few times and made me check voltages under load with a Cellog. Sure enough one cell was going down way faster than the other 11. Changed out that cell and am getting full range (> 20 miles) from the battery before cutoff. I'm using 2.75 for my LVC.
otherDoc
E-bike stable at our house

Steintrike Mad Max full suspension trike rear Cute 100H going on: Whoops, Cute wheel broke but I fixed it.
Sun USX delta trike EbikeKit small geared front wheel sort of front suspension for wife

Agniusm/A123 AMP 20 36 volts on the Steini has been taken off.
2x16000 Multisport from HK now gone as they died after 2 years
New Luna 10S bottle battery 13.6AH now on mine
Relatively New 10S4Px2 for wife's bike giving 20ah @ 40 volts home made Panasonic from Tumich. BMS's rule.

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Re: Smart Switch V4 "Intelligent low voltage cutoff switch"

Post by Kin » Feb 25, 2013 1:26 am

I am both happy this exists, and totally frustrated that it happens to be exactly what I was planning for a couple months to do myself. :p
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Re: Smart Switch V4 "Intelligent low voltage cutoff switch"

Post by Diamondback » Feb 25, 2013 7:31 am

received my smart switch a few days ago. (thanks Kfong :D )

mounted it in a nice box, soldered on the input and output wires and plugs for my application.
i am yet to install it on the trike though. will try to get that done this coming weekend.

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Re: Smart Switch V4 "Intelligent low voltage cutoff switch"

Post by migueralliart » Feb 25, 2013 10:35 am

I wanted to purchase this a while ago but I thought it was not sold as a ready unit. Does this still apply?

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