Zero-Draw, Solid State Contactor w/Precharge (Arduino)

[etriker]

I push a little button that charges up the cap. count to ten then turn on the battery switch.

A little button, a resistor and a high amp boat switch.

I really like simple.

 

[grindz145]

I think Methods is really trying to take the user-error out of the equation. From all of my friends blown-up controller/batteries, I have to say that there is a huge need for this. Even holding down a button is too much involvement for many people, trust me... I've seen the KFFs.

 

[etriker]

Right ? Smart enough to not get killed riding an electric bike in traffic but tricked up by 1 extra little button ?

I can believe it !

 

[grindz145]

Absolutely. Bicycle good riders |= good with electronics. Also, it's not just a Precharge switch....

 

[etriker]

And I don't think Vizio is killing peoples tvs with faulty online updates on purpose.

They put too many bells and whistles on the tv and got in over their heads with a product that is too complex to be reliable and still be very thin on the wall ?

The crappy caps take care of the planned obsolescence ?

 

[migueralliart]

I really think all this stuff should be embedded in a controller already. It's time for a new generation controller that handles this.
Most controllers have the on/off switch but this leaves connected the caps to battery voltage. What we want with all this is to have a battery cut off AND precharge. It's 2013 I don't see why we can't have this added to controllers already.

 

[etriker]

My ezip controller does.

Hook up the battery and you can see the current flow on the watts up meter to charge the cap.

Yes in the controller is nice.

My 60 amp controller from TNC scooters will make a big spark and needs the little precharge button to be pressed and count to ten before turning on the battery switch to prevent a spark.

 

[liveforphysics]

Auto-pre-charge is damn nice to have.

Flip the switch, caps charge up, then main power gets connected, then you go ride. At end of ride, flip the same switch to 'off', battery is safely disconnected from any parasitic drain that would kill it if you just let it sit for a month or whatever.

It just seems like the way every ebike should be already, but very few are. Most folks have some order of operations with pre-charge to get right, OR they can't just let the bike sit for an extended period or their battery will slowly be destroyed. I think it's important for ebike's to go mainstream that these things are worked out to a point it's 1 simple switch and you can't do it wrong as a human no matter what combination or timing you flip that switch with, and your pack doesn't drain dead if you just let it sit in your garage for some period of time.

 

[Arlo1]

I am going to build this into my bike with a contactor. I have killed a set of Lipo for this very reason.

 

[isaac_alaska]

on my electric snowmobile (running 250 volts and 250 amps, from an 8kwh pack of turnigy lipo) i have a latch circuit with a three-position automotive key. you turn the key from off to run and it connects all the low voltage stuff (12 volts). then clicking it once to "ignition" and then releasing it back to run toggles a latch. the latch provides power to a relay that connects 100ohms to the cap, precharge finishes in about 1/2 second, and a 1second time delay then closes the main contactors. i think this same idea could be used here, but use fets instead of contactors. having the arduino on board makes it a ton easier. you could use a single fet and resistor for pre-charge, and then the arduino supplies the time delay and sends power to the gates of the main fets. also means you don't have to worry how fast you switch the fets, because the resistor takes care of any pre-charge so there is never a huge current surge.

 

[bigmoose]

Were getting there... the system is starting to evolve.

The main contactor (be it electromechanical or FET) needs to be an integrated module in the battery. That makes it a "smart" battery, and BTW is one ways for it to comply with Test item T5: Short of output terminals of UN/DOT Section 38.3 : “Lithium Battery Testing Requirements” to boot.

 

[megacycle]

Still thinking simple, off the shelf SSR and a potential divider precharge line in parallel with the SSR.
Two precharge resistors and run switch all in series, 1st resistor across the SSR control input, 2nd resistor is with the run switch and sets the voltage drop across the 1st for SSR control.
Obviously all battery voltage dependant, but a lot of SSR's appear to have a 5-32V wide control voltage, would expect the opto control current should be tiny during run.
Halfbakery at moment.
Seems all tricky if you want to comply with ebike standards, more devices, more complexity, more to go wrong, more losses.
Safety often being counter to efficiency.

 

[liveforphysics]

Still thinking simple, off the shelf SSR and a potential divider precharge line in parallel with the SSR.
Two precharge resistors and run switch all in series, 1st resistor across the SSR control input, 2nd resistor is with the run switch and sets the voltage drop across the 1st for SSR control.
Obviously all battery voltage dependant, but a lot of SSR's appear to have a 5-32V wide control voltage, would expect the opto control current should be tiny during run.
Halfbakery at moment.
Seems all tricky if you want to comply with ebike standards, more devices, more complexity, more to go wrong, more losses.
Safety often being counter to efficiency.

Just to play devil's advocate (which I think is important in refining an idea), wouldn't an SSR just be a couple source to source FETs so they block current both ways, and an opto to drive the gates on? So if I understand right, it's not going to offer you anything you can't do with a pair of FETs and your own custom drive circuity, except in the case of doing it with discreet components, you can choose ideal FETs and ideal drive circuity with respect to low power consumption for the application. Perhaps a unit exists already that does all this just like we want? I've never seen one that had very impressive specs, but I haven't looked into them for at least 2 years.

 

[megacycle]

Thanks Luke, i did have that in the back of my simple electronics mind, that this is basically what the SSR is, i think they are usually multiple fet chips in the package and a fet option as Methods is proposing for the power side would be a much cheaper and purpose built option, intergrating into a working package does up the work and price a bit though.
I was aiming for a lot simpler more analogue control option, complexity being left to the bms and intergrate
hvc/lvc overide, now, as circuit proposed earlier http://i.imgur.com/rIdNLLi.png, with the 'ignition' switch deleted.

 

[briogio]

Ok I will represent the enthusiastic, but Etech baffled! Relative newbie, been learning from ES and experiences with a front BMC 48 volt complete kit from Ilia in SanFran. I've upgraded my battery to 72 volts, and I never liked the spark that happened when I plugged my battery into the system. What you're talking about is basically a safe switch to replace the plugging the battery? I did buy a 50 amp heavy duty switch but it seems only marginally better. LiveforPhysics I really enjoyed your writings on Electric Bike because you wrote them so any dumbass, (like me), could understand! I'm understanding maybe 5% of this thread, enough to realize that y'all are trying to create something that we could all use. Has anybody got one to sell? or component list and wiring diagram? Don't want to go the major spark route with my 72 volt battery!

 

[megacycle]

Thought i'd put this into use in the intrim.
Left over polarised solar dc breaker+ auxiliary switch.
.
C/B 40A,220V dc, auxiliary is 5A wired inline with the precharge resistor.
The switch is wired N/C to precharge so if i connected to battery with breaker off it will precharge till i switch breaker on.
It still doesnt give full isolation, but at least it's got battery precharge, overload and short circuit protect happening, actually a shunt trip connected could also enable bms to trip C/B.
Not trying to steal thunder, but i'm fairly confident there is a full, simple electromech solution to link to bms for battery protection, another story, another thread though.

 

[methods]

Looks like you guys are having a healthy discussion.

I agree with BigMoose that the switch should be integral to the battery... in my eyes a "battery" has a cell level protection, Fuse, and cutoff built in. Should not matter if you are hooking up to a controller or just shorting the leads together.

As far as some of the other ideas / solutions - the devil is always in the details. Parasitic draw and wiring. There are plenty of parts around that one can poke together to accomplish what we are trying to do - but many of them will also draw 2-3W of power. I am excited by the prospect of drawing microwatts of power so that the solution does not become part of the problem.....

I am also interested in not bringing in power off the main battery. It makes the whole system voltage dependent and very application specific.

new subject:

To get around the gate rise time issue today I am building a representative circuit out of IRFB4115 fets and I am going to switch a worst case load - a low cost 120V 50A power supply (meaning it will overshoot easily) into a super low internal resistance huge dead battery. I will keep slowing down the turn-on time until we get to damaged mosfet territory. I am guessing that I will find that any of these gate drive circuits will work perfectly fine.

Then I will repeat for the much easier test of turning on the controller V-Reg

Then I am gong to build this and move on to the full scale SSR solution.

-methods

 

[methods]

Awesome - you have repeated your simple solution that does not meet the design requirements.

How is that going to stop charge current in an HVC event?
Where is the power going to come from that runs through that switch and energizes the opto?
What kind of BMS has an active high output?
Where does that address PreCharge?

With the number of discrete components you would need to get that working (including the ultra wive voltage regulator you would need that is not shown) it would be more parts and be less useful - i.e. that circuit will only work for that application in that voltage range.

For the same number of parts I can create a switch that is good for 0V to 150V, 0A to 50A, requires no connection to VCC, can be hooked up high side or low side, can break charge current, or break controller regulator power, or just work inline with a 4S accessory pack, or - it can work with any DIY guys one-off application. It draws no current form the main stack whether ON or OFF. It has minimal wiring and fuss. It can protect against HVC and LVC with our without an external switch.

Nothing drives me more crazy then folks who ignore the design intent and just post deceptively simple "solutions" that distract from the goal. If that is the solution then please build it, test it, document it, produce it, and make it available for people to purchase it. Lets see if you can sell enough of them to even cover your cost in parts, labor, and customer support. You will find out quickly that your limited solution will not meet the wide range of requirements that the members have.


-methods

draws almost nothing, wayyy less than any contactor or bunch of expensive mosfets (including losses in heat). And really nothing when switched off.

 

[etriker]

On the Currie kit the battery switch is on the back behind the rack.

You have to reach back to turn it on and that is not that easy. Easier to turn on the switch when off the bike.

As soon as you turn it on it starts precharging the cap.

The location of this switch is a simple design delay ? By the time you reach around to the throttle the cap is charged and the controller is ready to go ?

If you hold the throttle open at all and turn on the battery switch on the back of the rack the motor will not turn until you release the throttle.

I like to study others design and see how they solved problems.

The Currie design is somewhat like the old VW bug.

They stuck with it and kept improving an old design.

 

[megacycle]

Yeh sorry there Methods i was getting confused with the hvc duhhh and charge control wasnt considered as thats usually a charger/bms function.

Going off topic, slightly, if your discussing losses and i understand you also mean standby and parasitic losses,
need to look at all losses and not get carried away by tiny losses a switch could delete.

Looking at battery protection a fuse is about 200% as lossy as a molded C/B, normal circuit operation and you can't reset these fuses, painfully have to replace them. Overload condition is within the spec's of a c/b, no stress.
The c/b could be tripped by a N/O shunt trip enabled from a signal from handlebar.
If these battery systems were in industry you would often see an electromech battery protection solution, has much higher reliabilty and neglible losses and talking.handling fault currents of anything up to 1kA, which is hardly ever considered in design, this c/b is 6kA.
The footprint of the setup is not particularly big or heavy in comparison to electronic solutions.

While elegant and comprehensive in operation your fet solutions is on a heatsink for a reason.

Precharge happens usually in part of a sec and precharge resistance values arent crucial.

 

[briogio]

Yeh sorry there Methods i was getting confused with the hvc duhhh and charge control wasnt considered as thats usually a charger/bms function.

Going off topic, slightly, if your discussing losses and i understand you also mean standby and parasitic losses,
need to look at all losses and not get carried away by tiny losses a switch could delete.

Looking at battery protection a fuse is about 200% as lossy as a molded C/B, normal circuit operation and you can't reset these fuses, painfully have to replace them. Overload condition is within the spec's of a c/b, no stress.
The c/b could be tripped by a N/O shunt trip enabled from a signal from handlebar.
If these battery systems were in industry you would often see an electromech battery protection solution, has much higher reliabilty and neglible losses and talking.handling fault currents of anything up to 1kA, which is hardly ever considered in design, this c/b is 6kA.
The footprint of the setup is not particularly big or heavy in comparison to electronic solutions.

While elegant and comprehensive in operation your fet solutions is on a heatsink for a reason.

Precharge happens usually in part of a sec and precharge resistance values arent crucial.

WOW! I don't understand ANY of that!! Are you talking about an on/off switch for the battery? because that's what I need. By the sound of it you haven't nailed down a design yet.

 

[999zip999]

briogio
You need a recharge resistor for your setup. I look and tell you what I have later or you can just look it up I even found the resistor's at radio shack. Precharges at 78v then plug in the main line at 84v no spark.

 

[megacycle]

WOW! I don't understand ANY of that!! Are you talking about an on/off switch for the battery? because that's what I need. By the sound of it you haven't nailed down a design yet.

[/quote]

Basically it is an intelligent battery switch, using simple, off the shelf, standard, electrical protection gear, to make a low loss solution for the battery protection side of things, i'd like to explore the other options that will standardise it for any pack voltage and adjustable overcurrent protect and an optoon for lvc/hvc pack level tripping might be a side line, start a new thread for it.

 

[circuit]

Awesome - you have repeated your simple solution that does not meet the design requirements.

Yes, because, it seems, not everyone is getting it.

How is that going to stop charge current in an HVC event?

You should use a BMS to control your charging and discharging. Charger is connected through the BMS, which has a mosfet or two for the job.

Where is the power going to come from that runs through that switch and energizes the opto?

Each BMS has discharge line mosfets. Take a signal from discharge mosfet's gate and source.

What kind of BMS has an active high output?

All of them control their mosfets with high level.

Where does that address PreCharge?

You don't need it, since you hook this up once (use a resistor for that) and forget it. Of cause some of you, bms haters, are messing daily with series/parrallel reconnection. This is not for you. Or maybe for you, after you start a fire and rethink stuff.

With the number of discrete components you would need to get that working (including the ultra wive voltage regulator you would need that is not shown) it would be more parts and be less useful - i.e. that circuit will only work for that application in that voltage range.

Both statements wrong. You don't need a regulator, since you take control signal from your existing BMS (small and cheap one, rated for any current you want, say 20A). Fuses you must have in your system anyway. This leaves us with 4 parts: PNP BJT transistor, two resistors and optocoupler. Total cost under $1. Total weight under 0.5gram. Total size around 10x10x4mm. Compare it to what you are offering. A bulky hot brick.
And my solution works with any voltage and any current. And no heat, no power dissipation. Does not require any additional supply. Is completelly dead when switched off.

Nothing drives me more crazy then folks who ignore the design intent and just post deceptively simple "solutions" that distract from the goal. If that is the solution then please build it, test it, document it, produce it, and make it available for people to purchase it. Lets see if you can sell enough of them to even cover your cost in parts, labor, and customer support. You will find out quickly that your limited solution will not meet the wide range of requirements that the members have.

Double that! You did not give a second to think how my solution works. I did look at yours and, sorry to say this, it stinks. It is nothing more than bunch of mosfets already being used in BMS'es.
And I did build it and made it public back in 2010. Too bad you did not give a ***t.

draws almost nothing, wayyy less than any contactor or bunch of expensive mosfets (including losses in heat). And really nothing when switched off.

you can't reset these fuses, painfully have to replace them

In correctly designed system fuses do not go with no real reason. And when they go, they do it only to protect you from fire. Usually there are a lot more of things to fix if fuse blows. Especially in these high power systems.

If these battery systems were in industry you would often see an electromech battery protection solution, has much higher reliabilty and neglible losses and talking.handling fault currents of anything up to 1kA, which is hardly ever considered in design, this c/b is 6kA.
The footprint of the setup is not particularly big or heavy in comparison to electronic solutions.

While elegant and comprehensive in operation your fet solutions is on a heatsink for a reason.

True. I've mentioned this before, but in industry, semiconductors are not allowed for battery switching. That must be done by a heavily oversized contactor to withstand fault current, which can be higher in few magnitudes. Usually contactors can withstand short term overcurrent without welding together, but this must be designed well to withstand the melting time of the fuse. Usually fuse is the last one to blow.
Contactor/switch/whatever short usually is bad not because something will blow (fuse blows and disconnects the system anyway), but because of false safety feeling during maintenance.

 

[megacycle]

What i meant by industry is battery systems we use say in substations at 2kA, not far off were we are at.
The Isc could be up to 1kA, depending on your battery setup, that's significantly more than your car battery cranking amps.

A c/b quite often has a trip time as fast as or faster than a fuse depending on the device, the one ive got is a trip C curve, which i think is similar to a hrc fuse trip time, some guys using automotives, designed for less than 32V, not all, i think 'Ice' puts in a good inline, they could be in for a nasty suprise at 100V+ when they accidently short the +&-, good luck breaking that circuit, the arc could well try to sustain itself external to fuse, once it's disintegrated and blown it's guts out because it wasn't meant for 1kA.

You also have to remember, as i forgot and had to be reminded ,considering the setup, it is a battery isolator switch for turning the power off, it can also be used to switch the battery off under any fault condition, from the external gear as an in smoke coming out of controller etc.Your option, doesnt isolate the battery, it deals with hvc/lvc which is complementary and initially different from my basic setup.