# [EVDL] Re gen on DC



## EVDL List (Jul 27, 2007)

Shunt boost chopper DC regen works fine. I built a three in one controller 
in 1971 that was a combined motor controller, boost regen, and battery 
charger all in one electonic package using SCR's and a SEPEX motor. It 
worked great.




On Sat, 17 Nov 2007 07:53:50 -0800 (PST), gottdi wrote
> I have been busy reading on the pitfalls of regen on DC setups. 
> However I did have an idea. It is known that AC is the regen king. 
> But most have DC setups. What about the possibility of adding into 
> the drive line or motor an AC generator. I happen to have a small AC 
> generator with a dead engine but the generator still works fine. It 
> is old and only has two 110 outlets on it. It pumped out power 
> before the engine died. What if you attached something like this to 
> the DC shaft and only set it up to generate when you press the 
> brake. All other times it is just there for the ride. Maybe even 
> have an electronic clutch so the AC is not even attached until the 
> brake is pressed. This could give regen for a DC set up.
> 
> No considering the extra weight and custom fitting and stuff, how 
> easy would it be to build a set of controls for that AC generator to 
> regen for you. It's only purpose is to regen so it would have a 
> seperate system. When you apply the brake your DC is off line anyway 
> so that is no problem.
> 
> What do you think. Could a small AC generator handle that job? I 
> could fabricate a way to install it inline with the drive shaft as 
> well. It is really not that big nor is it that small. I can get 
> sizes. However my gen has no output tags. It is an old military unit 
> and uses an old vibrating htz guage. Pretty cool to watch. Gens at 
> 50 to 60 htz cycles and the guage actually works.
> 
> Or am I just barking up a dead tree?
> -- 
> View this message in context: http://www.nabble.com/Regen-on-DC-
tf4826947s25542.html#a13810367
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> 
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## EVDL List (Jul 27, 2007)

From: gottdi
> I have been busy reading on the pitfalls of regen on DC setups.

The basic problem with DC regen is that you need a motor that is *built* for regen. Most motors aren't.

> I have an idea. It is known that AC is the regen king.

That's because there is no physical difference between an AC motor and an AC generator.

> What about the possibility of adding into the drive line or motor
> an AC generator?

Sure, that is a viable approach. People have been connecting a car's existing alternator to their EV's DC traction motor for years. An alternator is an AC generator with internal rectifiers.

> Not considering the extra weight and custom fitting and stuff,
> how easy would it be to build a set of controls for that AC
> generator to regen for you.

Your small engine-driven generator probably has a governor to hold the engine speed constant; this is how they regulate output voltage and frequency. The generator itself usually has no means to adjust its output. If you tried to use it in your EV, the voltage and frequency it generates would vary with motor speed; 120vac at 3600 rpm, 12vac at 360 rpm, etc. That's not very useful. So you would need some means to adjust the voltage, which adds a lot to the cost and complexity.

An alternator has a wound field. It is the AC equivalent of a DC sepex motor. You adjust the field current to control the output voltage, so you can get any voltage at any rpm.

> Could a small AC generator handle that job?

Well, "the job" isn't well defined. The size of generator you need depends on how much power you want to generate, and for how long. Just a little regen to simulate ICE engine braking, only used for a short time (while you have the brakes on) can be done with quite a small generator.

But if you want large amounts of regen, and will use it for long periods of time (going down a mountain, for example, or a mail truck that makes frequent stops), then the generator needs to be quite large.

At first, people think a separate generator and motor are a bad idea. But when you think more about it, you realise that the motor+generator need to be sized for the total driving+generating load. If your motor is barely big enough to handle normal driving, it will overheat if you also ask it to do regen. By having a separate motor and generator, you can tailor the size of each to suit the actual mission, so they are no larger or heavier than a single combined unit.

"The only thing new is the history you don't know yet." -- Harry Truman

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## EVDL List (Jul 27, 2007)

OK, I am learning. Went to Thunderstruck and read up on Spex

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## EVDL List (Jul 27, 2007)

George,

What is the difference between the Sepex motor vs lets say Netgains 
9in motor? Are the field windings different? Are these durable 
motors? Is there any used ones available and where might I look for 
one. How might I go about building regen into my conversion? I don't 
plan on a super hotrod but a good to and from work car. Peppy, yes 
but no need to be a hotrodder yet.

Where to start to pick your brain on this.

Pete

Sounds promising. Why don't more do this so they can have excellent 
power and regen as well.




> George Swartz wrote:
> 
> > Shunt boost chopper DC regen works fine. I built a three in one
> > controller
> ...


----------



## EVDL List (Jul 27, 2007)

OK, I am learning. I went to Thunderstruck and read up on the D&D 
motors with seperately excited field windings. This as they say is 
why you can do regen. Who besides D & D makes these motors and do 
they make these motors that can handle up to 144volts? I'd also need 
controllers. Would zilla work with these kind of motors?

I don't understand why they are not used more. Must either be 
expense, complexity of installing this function or just these motors 
are not that durable. It is for street use and not race track use.

Pete
Still learning.

Thanks
All your help makes a big difference and helps me ask better questions. 

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## EVDL List (Jul 27, 2007)

From: [email protected]
> OK, I am learning. I went to Thunderstruck and read up on the D&D 
> motors with seperately excited field windings. This as they say is 
> why you can do regen. Who besides D&D makes these motors and do 
>they make these motors that can handle up to 144 volts?

Virtually every large motor manufacturer does or has built sepex motors. 

Voltage is no paticular problem; they just need to know what is needed when they design it. Basically, motors for higher voltages need more commutator bars, because the most you want between two adjacent bars is about 30 volts.

> I'd also need controllers. Would zilla work with these kind of motors?

The Zilla is designed strictly for motoring -- no regen.

DC motor controllers that do regen have been built by Curtis, GE, Sevcon, 4QD, and Zapi (among others). They are less common because they cost more.

> I don't understand why they are not used more. Must either be 
> expense, complexity of installing this function...

Yes; these are the main reasons. Regen adds cost and complexity. Most customers won't pay for it, so most manufacturers either don't offer it, or sell very few systems.

AC motors naturally allow regen, and AC controllers pretty much all include regen. It's sort of like buying a luxury car; you get power seats whether you them or not (it's buried in the price).

> or just these motors are not that durable.

Whether a system is durable or not depends on how well it was designed, and whether you are using it within its design ratings. Frankly, many EV builders use parts that weren't designed for the application, and push them beyond their ratings (usinga 48v rated motor at 120v, etc.) Strangely enough, they aren't as reliable when you do this!

--
"Excellence does not require perfection." -- Henry James
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart-at-earthlink.net

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## EVDL List (Jul 27, 2007)

From: [email protected]
> What is the difference between the Sepex motor vs. let's say
> Netgain's 9 inch motor? Are the field windings different?
> Are these durable motors?

"Sepex" is short for "separately excited". It is a type of motor, not a brand name. A sepex motor is designed so you can connect *two* power controllers; armature and field. The armature controller does 98% of the work. The field controller is very small, and only supplies 2% or so of the power. But you need two controllers (which costs more).

A normal series motor has its field and armature wired in series, and is driven by one big controller. Series motors are the cheapest kind of motor, and so widely used in EVs.

A normal shunt motor has its field and armature wired in parallel, again driven by one big controller. Shunt motors are designed for constant speed, and so rarely seen in EVs.

Every motor company can make series, shunt or sepex motors; it just depends on what field winding the customer wants.

But, the customer who wants sepex probably does so because he wants to do regen, direct drive (no transmission), and/or electrical forward/reverse. These are harder on the motor. So, the manufacturer shouldn't just replace the series field with a sepex field; that will work short-term, but will have reliability problems (excessive brush arcing, for example).

When a DC motor has to operate over a wide range, the preferred solution is to add interpoles or other compensating windings. These extend the range of operation, so the motor can run at a wider range of voltages, currents, forward/reverse, and motor/regen without damage. Interpoles are common on all large, heavy-duty motors where reliability counts (series, shunt, and sepex).

So, to properly do regen on a DC motor, you need a) a sepex field, b) interpoles, and c) a second small controller to run the sepex field. The sepex field itself adds almost no cost; but the interpoles and extra controller do!

> How might I go about building regen into my conversion?

The simplest way is to add a separate small generator, connected to the main traction motor. Enable this generator with the brake pedal, or whenever you want regen.

Or, buy a motor and controller that include regen. This will either be an AC system, or a high-end DC system.

Or, you can cobble together a system that uses an existing series motor and controller to do regen; but it won't work very well or be particularly reliable. Maybe good enough for you needs, though.


--
"Excellence does not require perfection." -- Henry James
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart-at-earthlink.net

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## EVDL List (Jul 27, 2007)

Pete, I think Lee Hart has already described the basic caveats pretty 
well. We took a 120vdc series motor with interpoles and changed it to a 
separately excited by having the field rewound for 30vdc. This allowed field 
forcing, easy reverse, and most importantly at the time, allowed for the 
simplest topology since we were using early thyristor technology. Only one 
SCR chopper circuit was used and only one high current SPST contactor other 
than the safety main contactor was used to get both shunt regen and drive 
functions. Nowadays, since silicon is cheap and easy, two IGBT choppers 
would be used, one for drive, and one for shunt regen. 




On Sat, 17 Nov 2007 08:56:30 -0800, gottdi wrote
> George,
> 
> What is the difference between the Sepex motor vs lets say Netgains 
> 9in motor? Are the field windings different? Are these durable 
> motors? Is there any used ones available and where might I look for 
> one. How might I go about building regen into my conversion? I don't 
> plan on a super hotrod but a good to and from work car. Peppy, yes 
> but no need to be a hotrodder yet.
> 
> Where to start to pick your brain on this.
> 
> Pete
> 
> Sounds promising. Why don't more do this so they can have excellent 
> power and regen as well.
> 
>


> George Swartz wrote:
> >
> > > Shunt boost chopper DC regen works fine. I built a three in one
> > > controller
> ...


----------



## EVDL List (Jul 27, 2007)

Thank you all for your input on my questions. I now need to take some time
and soak up all this info I am gathering and reading. I will so some soaking
while I remove my ICE from the 510. 

Thanks a whole bunch

Pete
-- 
View this message in context: http://www.nabble.com/Regen-on-DC-tf4826947s25542.html#a13817197
Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com.

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## EVDL List (Jul 27, 2007)

> gottdi wrote:
> >
> > I have been busy reading on the pitfalls of regen on DC setups. However I
> > did have an idea. It is known that AC is the regen king. But most have DC
> ...


----------



## EVDL List (Jul 27, 2007)

> Christen Johansen wrote:
> >
> >
> >
> ...


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## EVDL List (Jul 27, 2007)

> gottdi wrote:
> >
> > I have been busy reading on the pitfalls of regen on DC setups. However I
> > did have an idea. It is known that AC is the regen king. But most have DC
> ...


----------



## EVDL List (Jul 27, 2007)

>What are the other downsides that people have been refering to?

One downside for a DC system would be that the failure mode for a DC 
Controller is "Full Power, Mr Sulu!", IINM. Obviously, you can get 
around this by using an "Oh shit handle" like in White Zombie (ICE's 
use the ignition). It'd need to be close-to-hand for use in the 
unlikely EVent of such an emergency. An AC systems failure mode is 
"They're dead, Jim", and EVerything stops.

It's for this reason that GM, Ford, Toyota etc will all use AC 
systems. The potential for legal action in our EVer-more litigious 
world is just too high for any other option. 

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## EVDL List (Jul 27, 2007)

>> What are the other downsides that people have been refering to?



> Dominant wrote:
> > One downside for a DC system would be that the failure mode for a DC
> > Controller is "Full Power, Mr Sulu!", IINM.
> 
> ...


----------



## EVDL List (Jul 27, 2007)

-------------- Original message from "George Swartz" <[email protected]xxx.xxx>: -------------- 


> 
> Shunt boost chopper DC regen works fine. I built a three in one controller 
> in 1971 that was a combined motor controller, boost regen, and battery 
> charger all in one electonic package using SCR's and a SEPEX motor. It 
> worked great. 

Hi George
I read your reply and was wondering if I could get any informaton on the three in 
one controller you described. Is it possible to buy schematic and part list. I am in
process of building a street bike EV and space is limited.
Thanks 
Rick Prentiss
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## EVDL List (Jul 27, 2007)

Rich, Sorry, that was done years ago using a SCR chopper circuit. You 
wouldn't want to duplicate this antique design. The key to making it work 
was the separately excited motor field that was reversed for regen braking. 
Braking was set up on both the accel pedal and the brake pedal so that when 
coming off the accelerator, the car went into the equivalent of compression 
braking and was set up for further regen on the brake pedal. The chopper 
was reconfigured using only one contactor plus the main line safety 
contactor. The regen was boost so that regen was strong all the way down to 
3mph or so and maximum energy was returned to the battery. I do have some 
recommendations: These days, silicon is cheaper and easier to use. You can 
design a low cost and compact bike controller using a separate FET choppers 
for drive and regen. If you use a permag motor, the boost regen is 
straightforward, since, unless you have a transmission, and downshift at 
high speed, the motor back emf will always be less than the battery voltage.

Of course, you can rewind the fields of a series motor to make it separately 
excited, but it will be a more fragile motor with potential brush arcing 
problems, etc. Should not be too much of a problem if your nominal battery 
voltage is low to start with.

Regarding the third charger function on my controller, I was attempting to 
do non-line isolated high rate charging on lead acid batteries. I don't 
remember getting it to work well. I don't recommend this for you at all. 
You should look for a good commercial charger or build one, with isolation, 
that specifically matches your batteries. 

If you were really ambitious, you would design a brushless wheel motor using 
rare earth magnets and a controller to go along with it. Regen is free. 
Good luck.












On Sat, 24 Nov 2007 18:43:00 +0000, evpage wrote
> -------------- Original message from "George Swartz" 
<[email protected]>: --------------
> 
> > 
> > Shunt boost chopper DC regen works fine. I built a three in one 
controller 
> > in 1971 that was a combined motor controller, boost regen, and battery 
> > charger all in one electonic package using SCR's and a SEPEX motor. It 
> > worked great.
> 
> Hi George
> I read your reply and was wondering if I could get any informaton 
> on the three in one controller you described. Is it possible to buy 
> schematic and part list. I am in process of building a street bike 
> EV and space is limited. Thanks Rick Prentiss 
_______________________________________________
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> http://lists.sjsu.edu/mailman/listinfo/ev

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## EVDL List (Jul 27, 2007)

From: George Swartz (on a combined controller/regen/charger):
> Rich, Sorry, that was done years ago using a SCR chopper circuit.
> You wouldn't want to duplicate this antique design. The key to
> making it work was the separately excited motor field that was
> reversed for regen braking... Recommendations: These days, silicon
> is cheaper and easier to use.

SCRs *are* silicon devices. 

It is useful to look at the *topology* of older circuits (the basic functionality; not the specific parts used). While you wouldn't use the same parts today, you may very well use the same basic concepts. For example, replace the SCRs with IGBTs (and change the gate driving circuits accordingly).

A sepex motor with interpoles is ideal for use as both a motor and generator. The seperately excited field makes it easy to control motoring and regeneration current, and the interpoles take care of the shift in brush timing.

If a controller can do regen, it is automatically a battery charger. The only difference is that the source of charging power needs to be switched from the motor to the rectified AC line.

> You can design a low cost and compact bike controller using a
> separate FET choppers for drive and regen. If you use a permag
> motor, the boost regen is straightforward, since, unless you have
> a transmission, and downshift at high speed, the motor back emf
> will always be less than the battery voltage.

The basic topology doesn't require separate controllers. Basically, you need two switches, an inductor, and a capacitor like this (view with a fixed width font):
___________________
| | |___
| | Q1 |_| _|_ D1 bridge
| | -||_ /_\ rectifier
| capacitor_|_ | |___| _ _ _ _____
| ___ |_______| | | |_________________|+ AC|__hot
| | | inductor | safety/ | |
| | |___ \ charging | |
__|__+ | |_| _|_ D2 _|_ contactor | |
___ battery | -||_ /_\ PM / \ | |
| - | Q2 | |___| motor \___/ | |
|___________|_______|_________________|_____________|- AC|__neutral
|_____|

Q1 and D1 are the high side switch. Q2 and D2 are likewise the low side switch. They can be SCRs, darlingtons, MOSFETs, IGBTs, etc. D1 and D2 are either actual parts, or the internal diode you get (whether you like it or not) in a MOSFET or IGBT.

The capacitor is needed because the battery current is pulsating. Without it, battery capacity is less.

The inductor is needed because PM motors have low inductance. If you try to use a PM motor's inductance you either get an excessive ripple current, or are forced to use such a high switching frequency that switching losses are high.

For motoring, you PWM Q1 and let D2 serve as the freewheel diode. The circuit operates as a buck converter, which steps battery voltage down. With a 100v battery for example, motor voltage can be 0-100 volts.

For regen, you PWM Q2 and let D1 serve as the rectifier for a boost converter. Q2 shorts the generator through the inductor, so current builds up in the inductor. When Q2 turns off, the inductor current is forced to flow through D1 and charges the battery. Once the inductor has fallen low enough, Q2 turns on again and the cycle repeats.

To use this topology as a battery charger, open the safety/charging contactor to disconnect the motor. Connect the DC output of a bridge rectifier in place of the motor. Connect the AC power line to the AC input of the bridge. Because it's a boost converter, the pack voltage has to be higher than the peak of the AC charging voltage (170v peak for the 120vac line). If your pack voltage is less, use a step down transformer or autotransformer. If you properly control the PWM of Q2, it can do power factor correction as well.

> Of course, you can rewind the fields of a series motor to make it
> separately excited, but it will be a more fragile motor with
> potential brush arcing problems, etc.

Yes. If your motor doesn't have interpoles, then the optimal brush position changes depending on direction of rotation and current flow.


--
"Excellence does not require perfection." -- Henry James
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart-at-earthlink.net

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## EVDL List (Jul 27, 2007)

> --- George Swartz <[email protected]> wrote:
> 
> > Rich, Sorry, that was done years ago using a SCR
> > chopper circuit. You
> ...


----------



## EVDL List (Jul 27, 2007)

Jeff, I am not mistaken, no offense taken. I am the original designer of 
this particular early SCR full boost regen EV controller. I could be 
getting a little forgetful in my old age, but here goes, I will try to 
explain: 

In 1971, SCR's were new to EV propulsion and high power FET's and IGBT's 
didn't exist yet. (I helped build some 1000amp bipolar transistors at 
Boeing Space Center in the mid 1960's but all of them became desk weights!) 
SCR choppers had to have an expensive and difficult to design commutation 
circuit that stopped current through the SCR for a sufficient time to turn 
it off. One missed commutation and there was a blown fuse plus several feet 
of smoking tire rubber. Therefore I did everything possible to use only one 
chopper as reliable as I could make it, yet obtain boost regen and battery 
charging as well as motor control. The first engineer I know of to come up 
with concept of a "3 in 1 EV controller" was Wally Rippel from Caltech (now 
at Tesla) so I don't take credit for this idea, just the hardware. 

High voltage contactors are likewise expensive and use of them should be 
minimized. I achieved the 3 in 1 controller by the addition of one SPST 
contactor, one diode, and the SEPEX motor. The main (safety) contactor 
remains closed during braking. The SEPEX motor field is reversed, while the 
freewheel diode path around the motor armature is opened and the brake diode 
steers the motor current back to the battery. I guarantee that it worked 
well. There are a lot of boundary conditions to observe for the motor. 
Reversing the field quickly is difficult even with 4:1 forcing which I had 
with a 120vdc battery and a 30v field. I went to a lot of trouble to blend 
the braking into both the accel and the brake pedals. With the advent of 
IGBT's and FET's, no one in their right mind would design a new controller 
in this fashion. It is positively easier to add a separate boost chopper, 
which becomes schematically one pole or one third of a three phase full wave 
bridge. You are correct in saying that the field is not reversed if you 
meant this to apply to new designs.

I don't know how to do short hand schematics on the EV list, but if you take 
a pencil and paper with the components I described, like a puzzle, you will 
come up with the topography quickly. 






On Tue, 27 Nov 2007 13:37:53 -0800 (PST), Jeff Major wrote


> > --- George Swartz <[email protected]> wrote:
> >
> > > Rich, Sorry, that was done years ago using a SCR
> > > chopper circuit. You
> ...


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## EVDL List (Jul 27, 2007)

I designed many sepex controls for golf carts, greens
mowers and utility vehicles while working at GE from
1993 to 1996. All of these designs were MOSFET
controls and boosted the sepex field to get regen. I
also designed series controls at Caterpillar and GE
and they reversed the field for plug braking (applying
very low duty cycle to the armature while reversing
the field with contactors). Maybe it was plug braking
on your control?
Rod
W8RNH
www.qsl.net/w8rnh



> --- George Swartz <[email protected]> wrote:
> 
> > Jeff, I am not mistaken, no offense taken. I am
> > the original designer of
> ...


----------



## EVDL List (Jul 27, 2007)

Rod,
Now I am getting really frustrated. You guys are piling on. No, it was not 
plug braking! Please, if you are a designer, take a few minutes and analyze 
the design. The following are the basic power circuit components: Battery, 
chopper (on/off switch), motor armature, free wheel diode, brake steering 
diode, main contactor, and brake contactor. (Not counting the field 
controller) Start with a simple drive only chopper/motor circuit with the 
chopper on the positive feed from the battery. Add a brake SPST contactor 
between the FWD anode and the lower armature connection (closed for drive, 
open for brake) and lastly, add a diode from the lower armature connection 
to the input of the chopper. (Note that the brake contactor breaks the 
freewheel path)

Now, reverse the field, so the lower armature connection is positive, and 
the brake contactor is open. Note that current now can flow from the motor 
armature through the chopper without reconfiguration of the chopper. During 
the off period of the chopper, current is boosted by the armature plus 
series inductor and flows into the battery. Of course, field control regen 
can be used up to motor base speed. I'll say it again. It worked well in 
its time, but no one would design it this way today. I wish we had power 
FET's in 1971. At that time, you were lucky to have silicon rather than 
germanium in your audio amp.

Just for historical interest, I designed my first SCR chopper in 1968 and 
demonstrated it to Victor Wouk, one of the early EV pioneers. It was 
planned for the Caltech/MIT electric car race, but a contactor controller 
was chosen for the race because of reliability concerns. In 1977, I 
designed a trolley bus controller that handled 475amps at 750vdc and was the 
first solid state controller used in production trolley buses in North 
America. These were as near zero maintenance as you can get and ran for 
over 20 years. The Randtronics Propulsion System is still in service in new 
bus bodies in Seattle, with a new IGBT chopper, but much of the original 
hardware. 



On Tue, 27 Nov 2007 17:52:38 -0800 (PST), Rod Hower wrote
> I designed many sepex controls for golf carts, greens
> mowers and utility vehicles while working at GE from
> 1993 to 1996. All of these designs were MOSFET
> controls and boosted the sepex field to get regen. I
> also designed series controls at Caterpillar and GE
> and they reversed the field for plug braking (applying
> very low duty cycle to the armature while reversing
> the field with contactors). Maybe it was plug braking
> on your control?
> Rod
> W8RNH
> www.qsl.net/w8rnh
> 


> > --- George Swartz <[email protected]> wrote:
> >
> > > Jeff, I am not mistaken, no offense taken. I am
> > > the original designer of
> ...


----------



## EVDL List (Jul 27, 2007)

George,
Sorry to 'Pile it on', but I didn't really give any
thought about how your control worked (and maybe it
does, I need to think it through which would be easier
with simple diagrams for busy engineers (maybe lazy)
like myself). I was just describing how I performed
this task with newer MOSFET controls while working at
GE. The Dodge TEVan not only boosted the field
winding but did something else with the armature, but
I'm not sure exactly what was done to get low speed
regen. I didn't design that control, but I drove one
for about 30,000 miles. The design work was done by a
fellow engineer and neighbor, Joe Lambert (who
designed most of the profitable controls for GE
forklifts in the 80's and 90's). Just one praise to
Joe, he was basically a technician that rose to
engineer status and made the entire division
profitable during those years. I've never seen a
harder working engineer than Joe, he would wake up at
3AM and work on the TEVan software because he didn't
have time during the day because he was designing
forklift controls for the core business.
Rod


> --- George Swartz <[email protected]> wrote:
> 
> > Rod,
> > Now I am getting really frustrated. You guys are
> ...


----------



## EVDL List (Jul 27, 2007)

Hi George,

No offense was intended. Just that a lot of folks
wrongly think regeneration is accomplished by
reversing the field, with sep-ex motors. Even some
engineers in the business. I had to run a test to
prove it to one such individual.

I see from your posts and replies to Rod that you were
able to do what you said. Thanks for explaining that.
Nice to learn something, even if I'll never do it
that way. But from what I gather, you reverse both
the field and armature, so the Eg adds to the inductor
voltage to exceed the battery voltage. Right? I
assume it was done in this way to avoid the addition
of another SCR.

Thanks for including the little history lesson also.

Regards,

Jeff M





> --- George Swartz <[email protected]> wrote:
> 
> > Jeff, I am not mistaken, no offense taken. I am
> > the original designer of
> ...


----------



## EVDL List (Jul 27, 2007)

Jeff, I will send you a private email with a sketch of the schematic. I 
don't think I can attach it to the EVDL.




On Wed, 28 Nov 2007 08:38:08 -0800 (PST), Jeff Major wrote
> Hi George,
> 
> No offense was intended. Just that a lot of folks
> wrongly think regeneration is accomplished by
> reversing the field, with sep-ex motors. Even some
> engineers in the business. I had to run a test to
> prove it to one such individual.
> 
> I see from your posts and replies to Rod that you were
> able to do what you said. Thanks for explaining that.
> Nice to learn something, even if I'll never do it
> that way. But from what I gather, you reverse both
> the field and armature, so the Eg adds to the inductor
> voltage to exceed the battery voltage. Right? I
> assume it was done in this way to avoid the addition
> of another SCR.
> 
> Thanks for including the little history lesson also.
> 
> Regards,
> 
> Jeff M
> 


> > --- George Swartz <[email protected]> wrote:
> >
> > > Jeff, I am not mistaken, no offense taken. I am
> > > the original designer of
> ...


----------



## EVDL List (Jul 27, 2007)

Hi,
I have been following this exchange with some interest. Is there some way you could post a sketch someplace where everyone could see it? I've done a lot of work on the old GE EV-1 controllers on forklifts and was wondering how you could do regen with SCR controllers.

Mike

>Date: Wed, 28 Nov 2007 09:09:12 -0800
>From: "George Swartz" <[email protected]>
>Subject: Re: [EVDL] Re gen on DC
>To: Electric Vehicle Discussion List <[email protected]>
>Message-ID: <[email protected]>
>Content-Type: text/plain;	charset=iso-8859-1

>Jeff, I will send you a private email with a sketch of the
>schematic. I
>don't think I can attach it to the EVDL.

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## EVDL List (Jul 27, 2007)

Hi Mike,

It is George's property. He was kind enough to send
it to me. I wouldn't post it publicly without his
permission. Not sure I know how to do that anyway. 
Be advised that it is for sep-ex and the GE EV1 SCR
controllers were for series motors. Cableform made
regen series SRC controllers way back when. I have
one on my electric delivery Jeep. Never did work
reliably. Have it defeated now. You might be able to
run across a Cableform schematic somewhere.

Regards,

Jeff M



> --- Mike Cook <[email protected]> wrote:
> 
> > Hi,
> > I have been following this exchange with some
> ...


----------



## EVDL List (Jul 27, 2007)

Jeff, My schematic is provided for the public domain. David says he will 
post it somewhere on EVDL. There are several other features that I recall: 
The brake contactor adds a galvanic open circuit in the motor drive loop 
when coasting, braking or idle stop. This improves safety a little by 
reducing fault paths of the motor full-on type that might launch an EV. The 
charger used the chopper as a series switch and also used the motor 
inductor. It could be used single phase or three phase. I used an 
isolation transformer, but it was large and it was floor mounted and not on 
the car. I will try to remember the specific charge circuit. I know that I 
was super concerned not to have any motor fault paths that might provide 
torque, etc. I also had a bypass contactor not shown on the simplified 
schematic. There were a lot of interlock circuits, I remember, and they 
always worked well. 



On Wed, 28 Nov 2007 11:52:50 -0800 (PST), Jeff Major wrote
> Hi Mike,
> 
> It is George's property. He was kind enough to send
> it to me. I wouldn't post it publicly without his
> permission. Not sure I know how to do that anyway. 
> Be advised that it is for sep-ex and the GE EV1 SCR
> controllers were for series motors. Cableform made
> regen series SRC controllers way back when. I have
> one on my electric delivery Jeep. Never did work
> reliably. Have it defeated now. You might be able to
> run across a Cableform schematic somewhere.
> 
> Regards,
> 
> Jeff M
> 


> > --- Mike Cook <[email protected]> wrote:
> >
> > > Hi,
> > > I have been following this exchange with some
> ...


----------



## EVDL List (Jul 27, 2007)

The old-school Chloride controller in my G-van uses a T-bridge configuration 
with a Sepex motor. There are basically 2 transistor switches; Battery to 
motor and motor to motor (short). For drive, they PWM only the Battery to 
motor transistor, and for regen the momentarily short the motor and then 
remove the short. The resulting high-voltage pulse conducts back through a 
diode into the pack. By modulating the duty cycle of the regen (motor 
shorting) pulses, they can control the strength of the regen. They do not 
reverse the field during regen, nor do any contactors have to change 
position.

-Phil
----- Original Message ----- 
From: "Rod Hower" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Tuesday, November 27, 2007 7:06 PM
Subject: Re: [EVDL] Re gen on DC


> George,
> Sorry to 'Pile it on', but I didn't really give any
> thought about how your control worked (and maybe it
> does, I need to think it through which would be easier
> with simple diagrams for busy engineers (maybe lazy)
> like myself). I was just describing how I performed
> this task with newer MOSFET controls while working at
> GE. The Dodge TEVan not only boosted the field
> winding but did something else with the armature, but
> I'm not sure exactly what was done to get low speed
> regen. I didn't design that control, but I drove one
> for about 30,000 miles. The design work was done by a
> fellow engineer and neighbor, Joe Lambert (who
> designed most of the profitable controls for GE
> forklifts in the 80's and 90's). Just one praise to
> Joe, he was basically a technician that rose to
> engineer status and made the entire division
> profitable during those years. I've never seen a
> harder working engineer than Joe, he would wake up at
> 3AM and work on the TEVan software because he didn't
> have time during the day because he was designing
> forklift controls for the core business.
> Rod


> > --- George Swartz <[email protected]> wrote:
> >
> >> Rod,
> >> Now I am getting really frustrated. You guys are
> ...


----------



## EVDL List (Jul 27, 2007)

How well does this work?

-----Original Message-----
The old-school Chloride controller in my G-van uses a T-bridge configuration

with a Sepex motor. There are basically 2 transistor switches; Battery to 
motor and motor to motor (short). For drive, they PWM only the Battery to 
motor transistor, and for regen the momentarily short the motor and then 
remove the short. The resulting high-voltage pulse conducts back through a 
diode into the pack. By modulating the duty cycle of the regen (motor 
shorting) pulses, they can control the strength of the regen. They do not 
reverse the field during regen, nor do any contactors have to change 
position.


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## EVDL List (Jul 27, 2007)

It works very well. It will routinely generate over 150 amps of regen 
current. When you release the accelerator pedal, they start with a small 
fixed amount of regen which is designed to simulate compression braking in 
an ICE. Then there is a pot on the brake pedal that increases the level of 
regen as you start to move the pedal, but before the pads are engaged.

Most of the time I can come to almost a dead stop in the 7000lb van using 
only regen. As soon as the motor stops turning, the regen drops out and the 
field current is cut. The van will then start rolling again if I'm on a 
hill and I have to apply the service brakes. (accomplished by pressing 
harder on the brake pedal)

http://www.austinev.org/evalbum/1413

-Phil
----- Original Message ----- 
From: <[email protected]>
To: "'Electric Vehicle Discussion List'" <[email protected]>
Sent: Wednesday, November 28, 2007 9:09 PM
Subject: Re: [EVDL] Re gen on DC


> How well does this work?
>
> -----Original Message-----
> The old-school Chloride controller in my G-van uses a T-bridge 
> configuration
>
> with a Sepex motor. There are basically 2 transistor switches; Battery to
> motor and motor to motor (short). For drive, they PWM only the Battery to
> motor transistor, and for regen the momentarily short the motor and then
> remove the short. The resulting high-voltage pulse conducts back through 
> a
> diode into the pack. By modulating the duty cycle of the regen (motor
> shorting) pulses, they can control the strength of the regen. They do not
> reverse the field during regen, nor do any contactors have to change
> position.
>
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
> 

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## EVDL List (Jul 27, 2007)

Then what's the catch? Why wouldn't this approach be more common today?

-----Original Message-----
It works very well.

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## EVDL List (Jul 27, 2007)

What, common in the EV market? There just isn't yet enough of an EV market 
for people to make the wide range of components that we need.

All practical applications that could use sepex are instead likely to use AC 
now. The enabling tech is that 3-phase inverters and motors are probably 
cheaper to manufacture than a sepex and it's controller. AC also needs no 
brush maintenance and usually has a smaller, lighter rotational mass than 
it's equivalent in sepex, and thus can run at a wider speed range.

-Phil
----- Original Message ----- 
From: <[email protected]>
To: "'Electric Vehicle Discussion List'" <[email protected]>
Sent: Wednesday, November 28, 2007 9:41 PM
Subject: Re: [EVDL] Re gen on DC


> Then what's the catch? Why wouldn't this approach be more common today?
>
> -----Original Message-----
> It works very well.
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
> 

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## EVDL List (Jul 27, 2007)

From: <[email protected]>
>> Re: [EVDL] Re gen on DC: Then what's the catch? Why wouldn't this
>> approach be more common today? It works very well.

(-Phil-) wrote:
> What, common in the EV market? There just isn't yet enough of an EV
> market for people to make the wide range of components that we need.

The on-road EV market is trivial. There are very few purpose-built 
motors and controllers for on-road EVs. The ones that do exist are built 
in very small numbers, so they are expensive and somewhat experimental 
(I wonder if this approach works? Let's try it and see...)

So, most on-road EVs are using motors and controllers designed for some 
other market, like fork lifts or golf carts. These markets have 
different requirements and customer expectations, so the solutions they 
use may not be ideal for an on-road EV; but they are available.

> All practical applications that could use sepex are instead likely
> to use AC now.

Well... I find that designers follow fashion trends, much like clothes 
or car styling. At the moment, AC induction drives are fashionable. They 
are new, exciting, and cool. They are sufficiently unknown to be 
interesting (maybe it can do this?) but not too risky or edgy. So, any 
young new company is automatically going to use it.

The DC sepex system is old, boring, and uncool. It's been around for so 
long that there are millions of applications in use. Designers know all 
about its strengths and weaknesses.

> The enabling tech is that 3-phase inverters and motors are probably
> cheaper to manufacture than a sepex and its controller.

Maybe someday. But to date, all AC systems have cost *more* than DC 
systems. Notice that the big users of EV parts (fork lifts and golf 
carts) are overwhelmingly DC. In fact, many golf carts use sepex DC 
motors and controllers.

> AC also needs no brush maintenance

True; although brush maintenance is a small problem. Every motor in 
every car has brushes (except for the traction motor in the hybrids). 
Even alternators have brushes. When was the last time you ever heard of 
anyone doing any brush maintenance on any of them?

> and usually has a smaller, lighter rotational mass than its
> equivalent in sepex, and thus can run at a wider speed range.

True; but again, this is not really much of an advantage. AC induction 
motors have low torque, so designers make up for it with high rpm. This 
increases the effective rotational mass, slowing acceleration. It also 
requires special gear reducers to deal with the high RPM.

I think there is a whole spectrum of options for EV drive systems. At 
the risk of oversimplifying, I'd rank them like this:

The low cost, low tech, low featured, and low risk end:
- series DC motor and contactor controller
- series DC motor and PWM controller
- series DC motor and regen controller
- sepex DC motor and regen controller
- PM DC motor and regen controller
- AC wound rotor motor and simple inverter
- AC induction and simple inverter
- AC induction motor and regen inverter
- PM AC and regen inverter
- "brushless DC" and special inverter
- switched reluctance motor and special controller
The high cost, high tech, high featured, and high risk end:

The AC induction motor is about in the middle. To a big corporation, 
cost and risk dominate management's thinking, so they wanted something 
at the low end. But their engineers were begging for something at the 
high end. They worked out a compromise, leading to induction motors in 
the recent GM and Ford produced EVs. Honda and Toyota, who are more 
confident and less risk-adverse, used PM AC motors in their hybrids.
--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net

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## EVDL List (Jul 27, 2007)

----- Original Message ----- 
From: "Lee Hart" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Thursday, November 29, 2007 8:56 AM
Subject: Re: [EVDL] Re gen on DC

{snip}

> (-Phil-) wrote:
>> All practical applications that could use sepex are instead likely
>> to use AC now.

{snip}

> Lee wrote:
> Maybe someday. But to date, all AC systems have cost *more* than DC
> systems. Notice that the big users of EV parts (fork lifts and golf
> carts) are overwhelmingly DC. In fact, many golf carts use sepex DC
> motors and controllers.

FYI, this is changing right under our noses, Every new Yale forklift is now 
AC. Look:
http://www.northamerica.yale.com/yna_product_details.asp?product=ERP-DH&page=yna_electric_rider_trucks.asp

Yale is one of the industry leaders, but all other major players seem to be 
going this way.

I just recently saw an AC powered manlift. Neat!

I'm all for this, as it will soon put cheap AC drive components in our 
hands.

-Phil 

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## EVDL List (Jul 27, 2007)

Why do you put BLDC and switched reluctance as more complicated than AC? I thought AC had to do high speed switching to pwm shape the waveforms, and BLDC and SR can do step control. It seems step control is simpler.

----- Original Message ----
From: Lee Hart <[email protected]>
To: Electric Vehicle Discussion List <[email protected]>
Sent: Thursday, November 29, 2007 9:56:34 AM
Subject: Re: [EVDL] Re gen on DC
...
I think there is a whole spectrum of options for EV drive systems. At 
the risk of oversimplifying, I'd rank them like this:

The low cost, low tech, low featured, and low risk end:
- series DC motor and contactor controller
- series DC motor and PWM controller
- series DC motor and regen controller
- sepex DC motor and regen controller
- PM DC motor and regen controller
- AC wound rotor motor and simple inverter
- AC induction and simple inverter
- AC induction motor and regen inverter
- PM AC and regen inverter
- "brushless DC" and special inverter
- switched reluctance motor and special controller
The high cost, high tech, high featured, and high risk end:

The AC induction motor is about in the middle. To a big corporation, 
cost and risk dominate management's thinking, so they wanted something 
at the low end. But their engineers were begging for something at the 
high end. They worked out a compromise, leading to induction motors in 
the recent GM and Ford produced EVs. Honda and Toyota, who are more 
confident and less risk-adverse, used PM AC motors in their hybrids.

...




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## EVDL List (Jul 27, 2007)

> Lee Hart <[email protected]> wrote:
> 
> > True; although brush maintenance is a small problem. Every motor in
> > every car has brushes (except for the traction motor in the hybrids).
> ...


----------



## EVDL List (Jul 27, 2007)

Hello George,

In a private email to you I called your circuit
clever. After some thought, I think elegant may be a
better descriptor.

The basic Jones chopper used as DC motor controllers
can be referred to as a quarter bridge, a switch and a
diode. When going to a separately excited motor
control, one uses a half bridge (two switches) on the
armature and a full (or H) bridge on the field (2 half
bridges). This makes sense when designing from
scratch. Gives you regen, field weakening and
contactorless reversing.

However, if one would want to do a sep-ex motor
control using an existing high current controller
designed for series motors, like the Zilla, then your
circuit might be the key. The 2000 amp Zilla isn't
cheap, and to make a full bridge version would likely
double the cost. So your approach, needing only an
additional diode and contactor, would be attractive.

Add in the fact that your circuit could be used as a
battery charger, and it becomes more attractive. How
many have contemplated a 2000 amp charger? 

Just some food for thought. Again, I thank you for
sharing this with us. I read hundreds and hundreds of
posts which are mundane and boring. It is a real
pleasure to come across a truly interesting idea.

I had said earlier that your circuit worked, but I
would not do it that way. Well, I am rethinking the
second part of that remark.

Regards,

Jeff M



> --- George Swartz <[email protected]> wrote:
> 
> > Jeff, My schematic is provided for the public
> > domain. David says he will
> ...


----------



## EVDL List (Jul 27, 2007)

Jeff Major wrote
>> Hi George,
>> 
>> No offense was intended... I see from your posts and replies to Rod
>> that you were able to do what you said. Thanks for explaining that.

You have my thanks as well, George. It's a clever system!

You have to understand that the EV list is huge, and some people's 
writing style can be less than polite. But at the heart of it, I think 
there is a genuine interest in understanding what you have done. People 
also make side comments that may seem critical, but are really just side 
trips on the topic to describe similar things that they have done or seen.



> George Swartz wrote:
> > Jeff, I will send you a private email with a sketch of the
> > schematic. I don't think I can attach it to the EVDL.
> 
> ...


----------



## EVDL List (Jul 27, 2007)

I did some looking but was unable to find any PM DC motors powerful enough for EV use although they are very popular with Ebikes. These would be ideal I would think because they would not require a DC->AC inverter, correct?

----- Original Message ----
- PM DC motor and regen controller



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## EVDL List (Jul 27, 2007)

> Lee wrote:
> >> To date, all AC systems have cost *more* than DC systems. Notice
> >> that the big users of EV parts (fork lifts and golf carts) are
> >> overwhelmingly DC. In fact, many golf carts use sepex DC motors and
> ...


----------



## EVDL List (Jul 27, 2007)

> David Dymaxion wrote:
> > Why do you put BLDC and switched reluctance as more complicated than
> > AC? I thought AC had to do high speed switching to pwm shape the
> > waveforms, and BLDC and SR can do step control. It seems step control
> ...


----------



## EVDL List (Jul 27, 2007)

> Glenn Saunders <[email protected]> wrote:
> > I did some looking but was unable to find any PM DC motors powerful enough for EV use although they are very popular with Ebikes. These would be ideal I would think because they would not require a DC->AC inverter, correct?
> 
> Nope, they're brushed DC motors, so their brushes act as a mechanical inverter.
> ...


----------



## EVDL List (Jul 27, 2007)

Jeff, Thanks, I feel better now. We charged the flooded lead batteries at 
about 200amps current limit for about 45 minutes which would be about a 70% 
or 80% recharge. Of course, the taper charge is 4 to 6 hours after that if 
you have the time and patience. I will try to reconstruct the charge 
circuit diagram.

As I remember, the field transition time was about 200 msec, so this could 
be an objectionable delay in traffic. There was an armature interlock that 
prevented field transition unless armature current was zero amps. 



On Thu, 29 Nov 2007 10:30:06 -0800 (PST), Jeff Major wrote
> Hello George,
> 
> In a private email to you I called your circuit
> clever. After some thought, I think elegant may be a
> better descriptor.
> 
> The basic Jones chopper used as DC motor controllers
> can be referred to as a quarter bridge, a switch and a
> diode. When going to a separately excited motor
> control, one uses a half bridge (two switches) on the
> armature and a full (or H) bridge on the field (2 half
> bridges). This makes sense when designing from
> scratch. Gives you regen, field weakening and
> contactorless reversing.
> 
> However, if one would want to do a sep-ex motor
> control using an existing high current controller
> designed for series motors, like the Zilla, then your
> circuit might be the key. The 2000 amp Zilla isn't
> cheap, and to make a full bridge version would likely
> double the cost. So your approach, needing only an
> additional diode and contactor, would be attractive.
> 
> Add in the fact that your circuit could be used as a
> battery charger, and it becomes more attractive. How
> many have contemplated a 2000 amp charger? 
> 
> Just some food for thought. Again, I thank you for
> sharing this with us. I read hundreds and hundreds of
> posts which are mundane and boring. It is a real
> pleasure to come across a truly interesting idea.
> 
> I had said earlier that your circuit worked, but I
> would not do it that way. Well, I am rethinking the
> second part of that remark.
> 
> Regards,
> 
> Jeff M
> 


> > --- George Swartz <[email protected]> wrote:
> >
> > > Jeff, My schematic is provided for the public
> > > domain. David says he will
> ...


----------



## EVDL List (Jul 27, 2007)

Hi George,

Sorry to keep bothering you. But I was wondering last
night, did you have a problem with the motor brushes
during charging? Seems like passing current with a
stationary comm might be detrimental. Or were you
using only the inductor and by-passing the motor
during charge?

I was kidding about a 2000 amp charge . But 200
amps is pretty impressive.

And noticed that I said full bridge and meant half
bridge when speaking of using the Zilla.

Regards,

Jeff



> --- George Swartz <[email protected]> wrote:
> 
> >
> > Jeff, Thanks, I feel better now. We charged the
> ...


----------



## EVDL List (Jul 27, 2007)

Jeff, You are right. Passing high current through a stationary motor for a 
long time will burn the brushes and commutator leading to subsequent rapid 
brush wear and there is also a safety issue of developing motor torque from 
residual magnetism or field controller fault. The armature is a poor 
inductor compared to the external smoothing inductor anyway.

I think if you move the smoothing inductor to the top side of the motor, 
then add a power diode from the motor/inductor junction back to battery 
positive, the charge circuit will work. Main and brake contactors remain 
open during charging. I just don't remember the details such as the 
precharge circuit which must be active for both initial drive and charge set 
up because of the large electrolytic cap bank on the chopper input.

I don't think there will be any circulating current thru the motor. 
However, the brake diode can be changed to an SCR and switched on only for 
the brake mode. 

Adding the charge function to achieve a 3 in 1 controller means that the 
chopper must have a higher voltage rating. This system can be operated off 
line with no isolation transformer, however there are safety problems to be 
looked at. Higher voltage is less of a problem than reliable commutation at 
low voltage. Another detail is that if the chopper SCR commutation energy 
goes through the load, there will be a minimum charge current. There are 
some com circuits where com current does not flow through the load or where 
com energy is from an outside source (class D) so that the chopper can work 
reliably down to low voltages. This is all antique stuff at this point in 
time.

A single Zilla would work in this circuit. No commutation to have problems 
with. Note that some charger logic already exists in the controller 
because of the regen function that must be restrained from overcharging a 
fully charged battery: for example, if you live at the top of a mountain. 

One thing I didn't mention before is that the boost regen becomes dynamic 
braking at low speeds when the chopper boost efficiency is low, and most 
electrical brake energy is absorbed by resistance losses in the motor and 
controller rather than being returned to the battery. None the less, 
electrical braking is strong down to 3mph.




On Fri, 30 Nov 2007 07:04:09 -0800 (PST), Jeff Major wrote
> Hi George,
> 
> Sorry to keep bothering you. But I was wondering last
> night, did you have a problem with the motor brushes
> during charging? Seems like passing current with a
> stationary comm might be detrimental. Or were you
> using only the inductor and by-passing the motor
> during charge?
> 
> I was kidding about a 2000 amp charge . But 200
> amps is pretty impressive.
> 
> And noticed that I said full bridge and meant half
> bridge when speaking of using the Zilla.
> 
> Regards,
> 
> Jeff
> 


> > --- George Swartz <[email protected]> wrote:
> >
> > >
> > > Jeff, Thanks, I feel better now. We charged the
> ...


----------

