Experience with a Zapi controller

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PeterS
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Experience with a Zapi controller

Post by PeterS » Sat, 17 Jul 2010, 13:28

There has been discussion in recent posts about regenerative braking and Zapi controllers. Earlier this year I fitted a Zapi H3D controller to my Holden Combo EV and I would like to pass on my experience after 2500kms of driving with it.

I purchased my Zapi from a UK company called Electrofit Zapi. The US distributors of Zapi were not interested in supplying Australia. Electrofit Zapi are good to deal with, but as their controllers are made to order, there was a 6 week delivery time. Zapi is an Italian designer/manufacturer which also makes Zivan chargers. The manual which comes with the controller is comprehensive and has excellent wiring diagrams but is written in Italianised English, so it is a bit hard to follow in places.

I bought the H3D model with regen. You have to specify at time of order if you want regen so it can be programmed into the microprocessor at the factory. This feature then becomes fixed; if you ask for regen then that's what you get every time you back off the throttle when driving (but see my later comments about switching). It is possible to use the deadband in the throttle movement to coast without regen, but this requires a level of concentration which is not usually possible when driving in traffic.

The H3D controller is rated at 120V input voltage so it cannot be used with higher voltage battery packs. Its over-voltage tolerance is 30% but this is possible to reach with a nominal 120V battery pack during charging, particularly when equalising. To prevent damage, Electrofit Zapi recommends relay interlocking so the battery charger will not operate if the Zapi is connected to the battery through the main contactor or pre-charge resistor.   

The H3D's maximum output current is 800amps, although this can be reduced by user programming in 10 steps down to 600A. I have mine programmed to 750A and the start-off torque is now such that I can complete all trips in 3rd gear, even starting on hills. I could not do that with my former controller, a Curtis 1231C. Note that my Combo has LA batteries so it is a bit heavy at 1580kgs. The motor is a 9" ADC.

User programming is achieved with a Zapi hand held programmer. This plugs into the controller, and by menu selection a lot of parameters can be adjusted in 10 steps, but in reality only a few parameters are relevant to EV use. I only adjusted throttle dead-band, acceleration rate, max current and the two stages of regen current (see later).

The H3D is a large controller, about 3 times the size of a Curtis.   It weighs 12kgs and if you bolt it to the huge heatsink recommended by Electrofit Zapi, the combined weight is 19kgs. A Curtis controller weighs 9kgs. There are also three external Albright contactors which switch the motor between motoring and regen modes, and also offer reversing of the motor instead of using reverse gear. These contactors are special as they have 120V coils. They should be ordered from Electrofit Zapi at time of ordering the controller. Although the contactors switch every time regen is used, the microprocessor reduces current momentarily each time before switching, so contact life should be long.

The Zapi is very much a controller for industrial electric vehicles rather than road-going EVs. This becomes obvious when studying the multitude of I/O connections available. Things such as a seat switch, or separate forward and reverse throttle pedals, or speed limit switches are relevant only to electric forklifts and the like. The clunking of the contactors every time the driver starts off, backs off, or switches into reverse is also reminiscent of warehouse EVs. An unfortunate side effect of the industrial background is that the plastic case of the H3D is only rated to IP32 which means it should not be mounted in the engine bay unless adequate protection against wet-road spray is fitted around it.

Electrofit Zapi was most insistant that if I was to purchase their controller I must have a fixed gear ratio between the motor and the wheels; ie, no gearchanging. Apparently there have been failures of the output MOSFETS caused by regen switching on when the throttle is released during gearchanging when the gearbox passes through neutral on its way to causing a sudden change in motor speed. I took a chance that with the Zapi I would no longer need to change gear and this has been the case.

On the road, the Zapi performs well and I enjoy driving my Combo more than when I had a Curtis fitted because the Zapi has more grunt. Another good feature is that it runs at 18kHz so it doesn't emit an audible whine like a Curtis.

The regen comes on in two fixed stages. The first stage ('release braking') occurs when the throttle is backed off. I have the regen current programmed to the lowest level which gives me 20-30 amps, depending on the speed of the motor. Depressing the brake pedal ('pedal braking') to the point where the brake lights come on, but not the wheel brakes, gives another 20-30amps. So it is possible for me to see up to 60A being returned to the battery at 60kph. The regen current reduces with speed but is present right down to crawl speed.

My Cycle Analyst trip computer has shown up to 5% recovery of energy on my 35km commute to work if I use regen at every slowing opportunity; but mostly the figure is 2-3% when regen is used on long descents only. Release braking is about equal to backing off in a 4-cylinder car in 4th gear, and adding pedal braking is like backing off in 3rd gear. I am happy with this amount of regen because I only wanted to take the load off the wheel brakes when descending long hills. I did not expect to extend my range with regen. I have not seen any evidence of commutator wear but I have noticed the motor gets hotter because it is now doing double duty.

Regen is switched on by the throttle microswitch when the throttle is released. I wired a toggle switch across the microswitch so that I can switch out regen when I don’t want it; eg, when my batteries are fully charged, or when driving in stop/start traffic. The only hassle is that on power up, the controller needs the foot-off-throttle signal for it to boot up. Regen needs to be briefly switched in while turning on the ignition switch. I also mounted a second toggle switch so I can choose whether to have brake pedal regen active or not.     

The all up cost of my Zapi H3D with the heatsink, contactors, programmer and delivery costs was 1850 Pounds.

I would not recommend a Zapi controller to new EV converters because of the extra work in mounting it, the complexity of the I/O wiring, and because of its cost. New converters should keep things simple and use a Curtis or similar controller. However, for experienced EVers who want to upgrade their car, the Zapi has a lot going for it. I am very happy with mine.


     









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Post by a4x4kiwi » Sat, 17 Jul 2010, 14:24

Thanks Peter. Good write-up.

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Post by procrastination inc » Sat, 17 Jul 2010, 22:58

"Regen is switched on by the throttle microswitch when the throttle is released. I wired a toggle switch across the microswitch so that I can switch out regen when I don’t want it; eg, when my batteries are fully charged, or when driving in stop/start traffic. The only hassle is that on power up, the controller needs the foot-off-throttle signal for it to boot up. Regen needs to be briefly switched in while turning on the ignition switch."

could you by pass the toggle with the key START position?

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Post by PeterS » Sat, 17 Jul 2010, 23:17

That's an interesting thought but it wouldn't work because the switching has to be done in the right sequence. The foot-off-throttle signal has to be present when the main contactor puts power on the Zapi. Doing it the way you suggest would apply the throttle signal after the contactor closed. The Zapi would be well into its boot-up by then.

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Post by EV2Go » Sun, 18 Jul 2010, 03:55

Slightly confused... previous controller was a Curtis 1231C which is a Series DC controller not a Sepex controller, so how is Zapi controller doing regen if motor is Series DC?

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Post by coulomb » Sun, 18 Jul 2010, 05:09

EV2Go wrote: Slightly confused... previous controller was a Curtis 1231C which is a Series DC controller not a Sepex controller, so how is Zapi controller doing regen if motor is Series DC?

Well, that's the clever thing. It's also the reason for the external contactors, and the necessity of not changing gears while powered.

The contactors are for reversing the field with respect to the armature; in effect the motor is switched into reverse to enable regen. So this won't be as smooth as regen on an AC controller, or on a sepex DC controller. However, it allows far more commonly available motors to be used. Despite this, I'd only use a regen controller like this on a motor with interpoles. These are probably still more commonly available than sepex motors, I would guess.

See for example http://convert.jerryrig.com/step13.html where a Zapi H3 and a series motor are mentioned.

A dozen or so cars on evalbum have Zapi series DC controllers with regen, but I could not find a convincing example where the owner claims that it works well. One noted that they had to set the regen to a maximum of 100 A or it would fry the brushgear.
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Post by EV2Go » Sun, 18 Jul 2010, 06:00

Is there any way I could do that?

The Kostov motor I plan to use has interpoles, I have decided I will be using direct drive, and more than likely will be using reversing connector for reverse.

I don't believe the Solition1 controller was designed for regen but it would be extremely handy on the trike to help cut brake wear.

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Post by Electrocycle » Sun, 18 Jul 2010, 06:21

you could probably do it, but it will most likely be a bit messy and unrefined.
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Post by PeterS » Sun, 18 Jul 2010, 18:21

Some answers to the issues raised above:

A DC motor does not have its field or armature reversed to become a generator. A motor will become a generator if its back EMF exceeds the supply voltage. The current simply reverses direction in the armature and flows out of the motor into the battery. To get a higher voltage on the armature a motor has to have its no-load speed increased, or its field strength increased.

If you get hold of a small permanent magnet DC motor and connect it to a rechargeable battery with no load it will run as a motor at a speed determined by the battery voltage. If you then arrange to drive the motor at higher revs without changing the wiring connections it will operate as a generator. The current in the armature will have reversed as a result of the brush voltage being higher than the battery voltage. The field polarity remains the same. The connections remain the same. The torque on the motor shaft has reversed though, and the motor is now absorbing torque and becomes a regenerative brake.   

G. L. Jackson in the US wrote a booklet about how to force a series motor into regen for EVs ("Regenerative Braking with DC Motors" obtainable from KTA). His method increases the field current to several hundred amps to increase field strength at no load. This raises the armature voltage above battery voltage, again causing a reversal of brush voltage polarity and regen back into the battery. The motor also has to run at higher speed by the driver down-shifting a gear. It's a crude set up which I don't recommend.

The Zapi wiring diagram clearly shows that the field of the motor is not reversed. There is a reversing contactor across the armature but it's there for another reason. In both motoring and regen modes, current flowing through the armature goes through the controller before going to the field, for monitoring and control purposes. In regen, the current out of the armature reverses. It is reversed again by the DPDT contactor so it still flows through the controller in the same direction. An internal diode sends the regen current out through the positive connection of the controller, to the battery.    Another SPDT contactor on the other brush of the motor switches from battery positive when motoring to battery negative when in regen, to put the motor into a sort of sep-ex mode.

The requirement of external contactors on the Zapi somewhat detract from its finesse, but the combination works well. The clever bit is how Zapi get increased voltage in the armature for regen at low motor speeds. I read somewhere that a buck/boost converter cicuit is used inside the controller to raise armature voltage, with the motor windings employed as the inductor. I'd like to know more about it but I doubt whether Zapi would give out the details.   

I agree that a series motor with interpoles would probably work better with the Zapi than my ADC motor running at the neutral point. I would like to upgrade my EV to a Kostov interpole motor, but for the moment I can't find one which is a direct replacement for my 120V FB1-4001. I'm limited to 9" diameter.


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Post by EV2Go » Sun, 18 Jul 2010, 21:36

Ok after reading that several times I am reasonably certain I degested that correctly...

Because the Kostov motor I plan to use has series / parallel switching options within the same motor, could I under deceleration / no load switch from series to parrallel to increase the feild strength (roughly equivilant to your Zapi controller field power increase without the buck/boost circuit)?

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Post by coulomb » Sun, 18 Jul 2010, 21:53

PeterS wrote: A DC motor does not have its field or armature reversed to become a generator.

Right, but the connections to the field must be connected in reverse. The problem is that when the armature current reverses, the field (which usually has the exact same current as the armature, since they are in series) tries to reverse, and this would be bad (it would reverse the polarity of the back EMF in the armature). So you have to reverse the field connections to "re-reverse" or "right way round" the field current. You could also reverse the armature instead of reversing the field; the effect would be the same.

You are right in that I should not have claimed that the motor is "effectively in reverse for regen". The connections are the same as for reverse, but the armature voltage does not reverse, nor does the direction of the field magnetisation. (Or if you reverse the armature instead of the field, they both reverse, but the doubly reversed armature voltage becomes the right polarity to charge the battery.)

Since the field does not require as much power as the armature, it would seem sensible to use a separate chopper circuit for the field, effectively making it separately excited, but using a commonly available motor designed for series connection. Then you could simply put more current into the field to get regeneration without contactors. But of course, the field needs the same magnitude of current as the armature, and current costs more than voltage in a controller, so it doesn't work out economically (it would cost almost as much as two non-regen controllers). What you really want is a high resistance (higher voltage, lower current) field, and of course that's exactly what a separately excited motor is. Unfortunately, they are much less common.
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Post by EV2Go » Sun, 18 Jul 2010, 22:15

Is there any way that you could take two lots of cables off the cotroller and feed the power to the armature and field seprately but have a reversing contactor on the field to achieve this?

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Post by PeterS » Mon, 19 Jul 2010, 02:38

Sorry Coulomb, I stand by my assertion that neither the field nor the armature of a DC motor has to be reverse connected for regen to occur.

To be absoultely sure of what I'm saying I just now constructed a simple test bed using a small permanent magnet hobby motor. Using Meccano parts I put a 1/2" pulley on the motor and a 3-1/2" pulley on another shaft fitted with a crank handle. A belt passed around the two pulleys.

I wired the 12V motor to a 3V battery through my multimeter, set to measure current. The motor started and turned the crank handle at a slow speed. I then grabbed the crank handle and turned it much faster. The current reduced to zero, and as I cranked faster, it went negative. I was now putting current back into the battery (regeneration) without having changed any connections to the motor. The field maintained its same magnetic polarity throughout because it is a pair of permanent magnets.   

My test simulated the operation of a sep-ex motor. The Zapi controller switches the series motor into sep-ex mode for regen. Gary Jackson's regen circuit (referred to in my earlier post) keeps the motor connected in series during regen. It does not electrically switch either the field or the armature into reverse. It doesn't need to.

To EV2Go: I strongly recommend you do not attempt to design your own regen circuit. You will almost certainly damage your motor's windings and blow up your controller. If you want to have regen with a DC motor then purchase a Zapi controller or a Kelly. The latter requires two controllers for regen, according to Kelly, which makes it expensive. Alternatively go for an AC motor and controller in your EV and get regen as a built-in function.
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Post by antiscab » Mon, 19 Jul 2010, 03:45

It would be interesting to see how the zapi works.

boosting voltage reuires a (not small) inductor.
you can use the field windings in the motor as that inductor, and use a controller that has a half bridge with switching devices top and bottom.

your garden variety series dc controller has one set of switching devices and a set of diodes for freewheeling.

a series DC motor directly connected to a battery has no rpm at which it will become a generator.

the armature back emf is proportional to field current, which is determined by the difference between the battery voltage and back emf.

to get it to regen, the field current has to be increased for armature back emf to exceed battery voltage.

the boost conversion is necessary to keep regenerating when the rpm is too low to get enough back emf to exceed battery voltage.

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Post by coulomb » Mon, 19 Jul 2010, 05:13

PeterS wrote: I just now constructed a simple test bed using a small permanent magnet hobby motor.
Yes, but I thought we were discussing a series DC motor.
... as I cranked faster, it went negative. I was now putting current back into the battery (regeneration)
Yes, and if it was a series motor the reversal of armature current would have reversed the field direction, which would have reversed the back EMF, and bad things would have happened.
The Zapi controller switches the series motor into sep-ex mode for regen. Gary Jackson's regen circuit (referred to in my earlier post) keeps the motor connected in series during regen. It does not electrically switch either the field or the armature into reverse. It doesn't need to.
Ah, my misunderstanding. It must have two choppers then, one for the field and one for the armature, which would be rather expensive I imagine. You state that the Zapi controller has 3 (!) contactors that "switch the motor between motoring and regen modes". What are these doing if not reversing the field? Mind you, you can reverse the field with just one contactor (double pole of course). But maybe they do it with three single pole contactors somehow.

I thought one pair of contactors would reverse the field, and another would somehow increase the field strength (perhaps switching out a resistor that is normally in parallel with the field). If you drive the field with a second chopper, you don't need contactors at all except for electrical reversing.

Maybe one of those contactors is the main contactor; it seems to be the fashion these days for the controller to be turned on with a DC signal, and it does its own precharge, and turns on the main contactor for you when it's safe.
To EV2Go: I strongly recommend you do not attempt to design your own regen circuit. You will almost certainly damage your motor's windings and blow up your controller.
Seconded! This stuff is for the highly experienced. Just look through the EV album to find conversions, even using the Zapi controller, that have fried brushgear or blown up the controller. There is a reason that very few vehicles with series DC motors have regen. At minimum, you need cooperation from the controller. If you reverse or even reduce to zero the field at the wrong instant, you could blow up the controller from overcurrent or reverse voltage, or overspeed the motor.
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Post by coulomb » Mon, 19 Jul 2010, 05:39

This seems to be the "three contactor" circuit:

Image

Actually two contactors work in tandem to reverse the armature. It's unclear to me whether this would be for electrical reverse gear only; if you say they don't reverse the armature for regen then I'll believe you.
The other contactor changes the other side of the armature to be B- instead of B+! I guess that way, the buck circuit turns into a boost circuit. If that's what they are doing, then it's pretty clever. They must duplicate the armature chopper for the field. My mistake; I assumed that this would be too expensive to be practical. The wording on the page I referenced in my first post this topic misled me.

I guess that this controller would also give you a little more speed than a standard controller, since the voltage drop across the field is no longer in series with the armature.

Thanks for the info, PeterS, most interesting!
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Post by EV2Go » Mon, 19 Jul 2010, 07:51

I was only looking for an easy way to get some regen braking, and since I dont want to blow up nearly $4000 worth of controller maybe I should give it a miss.

What about a big alternator (12v 100+ Amp) that charges only under deceleration? Would be nice to have something to assist pulling up a 450kg trike.

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Post by Electrocycle » Mon, 19 Jul 2010, 13:46

I'm assuming you'll be going super overkill on the brakes, like the rest of the components - so I wouldn't expect brake wear to be an issue :P

The aerodynamics of a trike will be really bad too, so you're not going to get much regen out of it apart from very low speed or down a really steep hill - which probably won't work very well with the DC motor or alternator setups anyway.
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Post by EV2Go » Mon, 19 Jul 2010, 19:13

Uncharactristically no I haven't... I'm running 200sx rear discs and only a single disc up front. I am pushing the weight limit so I need to cut all superfluous weighty parts.

Problem is I typically like to front brake only and 450kgs and a single front rotor is going to chew expensive pads and rotors at an alarming rate, even twin front brakes would consume parts at a much higher rate than a bike.

If I rear brake only I have concerns about the tail wagging under hard braking, I generally like to rely heavily on the gearbox to provide engine braking. Regen would have been handy but really seems too hard to implement.

Edit:
Things have changed since July. I couldn't help myself trike is now getting twin Wilwood calipers up front and rear, but I would still like regen.
Last edited by EV2Go on Wed, 27 Oct 2010, 11:02, edited 1 time in total.

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Post by polo-ev » Tue, 24 Aug 2010, 14:20

I have come across a couple of examples of people using alternators for regenerative braking & I am considering doing it myself.
One person had rewired the alternator to output 160V & it fed juice into the battery back.
Another person simply used a standard alternator to feed juice into the aux battery under braking.
The alternator can be turned on & off by using a car air conditioning clutch which is switched on by the brake light switch.
The clutch was mounted on the rear end of the motor which meant the alternator was not spinning most of the time.

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Post by antiscab » Wed, 25 Aug 2010, 23:24

alternators are generally behind a rectifier bridge.

weaken the field and it drops out.
no clutch necessary.

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Post by EV2Go » Wed, 27 Oct 2010, 22:16

Two different ways to achieve same result but I guess the difference would be belt drag.

Peter any updates on how this turned out? Did you get the results you expected?

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Post by PeterS » Thu, 28 Oct 2010, 13:40

As regards how things have worked out; I've now driven 5000kms with the Zapi and the more I use it, the more I like it. I experimented with the max current limit and found that as I increased the max, the start-off current increased also. I now have the limit set to 750A (previously 600A), although I never use more than about 500A when driving. This change has made my car much more pleasant to drive; it's almost as though I've fitted a bigger motor without having done so. I can now drive my 1600kg EV everywhere in 3rd gear, even starting on steep hills.

The regen current increased in proportion too. I still have the two stages of regen set to low levels as I don't want to damage my motor, particularly its commutator. The effect with the first stage of regen (backed-off accelerator) is similar to a 4cyl engine car backed off in 4th gear. When I apply the second stage (brake pedal slightly depressed), the combined effect is similar to backing off a 4cyl engine in 3rd gear.

First stage gives 20-30A depending on motor speed and second stage adds another 20-30A. So 40-60A in total. I have seen 80A returned to the battery when I had both stages working at 60kph in second gear.

Regen takes some of the load off the wheel brakes, particularly when travelling down long hills and when slowing for red lights in the distance.

As for range increase, I haven't done any tests, but I also haven't noticed any increase. My feeling is any increase would be minimal. I fitted a Cycle Analyst trip computer which shows percentage regen based on amp-hours. I have to use regen a lot to achieve 5-6% recovery over the course of a trip. In hilly country I have seen 8-10%, but this soon reduces with flat road running.

To sum up: regen with a Zapi controller makes the EV more interesting to drive and provides mild braking which takes some of the load off the wheel brakes. It does not give much increase in range. Under power, the Zapi can output a lot of current to the motor giving a noticeable increase in the car's performance.
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