≤2000w 96V charger ~$5

[Alan B]

Microwave Oven Transformers

Unless you rewind it, a MOT is designed to put out around 2000VAC. Not useful for charging ebike batteries, but it would be a good way to zap yourself.

If you want to make a nicely isolated but very heavy ebike charger then do research on rewinding your transformer for low voltage and use it safely to generate a peak voltage slightly higher than your fully charged pack. Then you could make a safe charger.

 

[Matt Gruber]

i'm not doing anything with the microwave if it is 2-5kv! Have not opened it up. Thought it was step down, not step up! My bad!
i did rewind a transformer once to build a 12v car charger. worked good. NOT going to rewind another.
My question is, how do these accidents you guys warn about, happen with a proper fuse, cb, or other current limiter? Reminds me of the video showing jb weld could NOT make a good electrical connection, where I find it can make an EXCELLENT connection! Have 2 cells in my scooter connected with jbweld, no soldering! Harping on failures is not the path to success!
.
If i need a faster charge, i'll just parallel 2 chargers that i already have. 0 cost, twice as fast.

 

[Punx0r]

Because the current required to cause heart failure is usually much lower than the fuse or circuit breaker rating. An RCD can help prevent fatal shock where your body connects live to ground (but should not be relied upon to do so), but they won't do anything to help you if you insert yourself in the normal live-to-neutral circuit, you're then just part of the normal load.

Microwave ovens also contain a high voltage capacitor that can apparently retain charge for extended periods (you'd think there'd be a drain-down resistor) and are supposed to have killed many an unwary repairman.

micro-wave oven transformers are also built very cheaply and will not withstand long duty cycles or running at less than full load (they will overheat if underloaded).

 

[Matt Gruber]

how does the heart-stopping current get to me sitting in my lazy-boy chair; this is what i don't understand.
please explain!
why are you still talking microwave ovens! they are not good for this as they STEP UP, not step down!

 

[DrkAngel]

WARNING! in case you didn't know Electricity is dangerous! ... to placate the fear mongers ...

Damn ... just pick up a $2 hair blower at the local thrift and use the GFCI built into the cord! ... ?

Last one I picked up was 1850w rated, designed for use in high humidity surrounded by, (possibly standing in?), water.

WARNING! in case you didn't know Electricity is dangerous! ... to placate the fear mongers ...

 

[Alan B]

It only takes a few milliamps to interfere with operation of the heart and other muscles. So fuses and circuit breakers don't protect you there at all.

Ground Fault Circuit Interruptors are generally set to trip at a few mA, but they only protect by detecting mains current imbalance. Once you have charged a capacitor it becomes a new energy source and can provide dangerous current regardless of any GFCI.

GFCI's are very low cost items, and they are not highly reliable. Using one is a good idea, but it is not sufficient. In addition touching the circuit must be completely prevented with insulation.

When you connect a non-isolated charger to your ebike battery which is connected to the controller and motor you are subjecting the whole system to AC line potential. Coming into contact with conductors anywhere in the system puts you at risk. Any failure in any insulation, even the thin enamel in the motor windings, will connect the AC line to the ebike frame. Now the whole ebike is electrified and very dangerous. Even the capacitance of all the items to the frame can provide some current, perhaps not enough to kill, but enough to get a shock. We recently had a shock incident from a BLDC motor, just the capacitance from the windings to the motor case was enough to give a shock touching the ungrounded motor case.

A good practice here would be to put a solid connection from the AC line safety ground wire to the bike frame. That would provide some protection. No part of the bike's electrical system can be connected to the frame with this type of charger, but the frame should be grounded for safety.

Fuses and circuit breakers are both overcurrent protection devices but have different characteristics, each having advantages and disadvantages. Having one or the other is required, and the proper type and size is also quite important. The wrong type can fail in a bad way and not provide the required protection.

If the system is properly protected with GFCI, grounding, insulation, and proper overcurrent protection there are still risks. The shock risks might be during probing/testing, or failure of/inadequate insulation. Of course there are also risks of thermal events with the lithium batteries from overcharging, etc. I would have two distinct overcharging detectors that could shut off the charging via different mechanisms so a failure in one would not affect the operation of the other circuit.

 

[Punx0r]

how does the heart-stopping current get to me sitting in my lazy-boy chair; this is what i don't understand.
please explain!

Apologies, I didn't realise you were constructing and operating this device solely by telekinesis.

why are you still talking microwave ovens! they are not good for this as they STEP UP, not step down!

Considering you nearly connected up a MOT thinking the secondary was harmless, I thought it prudent to also warn you of the even more dangerous capacitor inside. For all I know you have the microwave sat there, case off, plugged in and exercising your curiosity by poking at it with a carbon fibre fishing pole from the comfort of your La-Z-Boy.

 

[Arlo1]

Ultimate lightweight charger! ... ?
Experimental!! ... hypothetical!

120V AC power outlet, power cord and a bridge rectifier will output "slightly rough*", up to 20A of 108V DC.
(108V DC output based on 120V APC brand UPS protected-regulated 120V)
This is optimal for charging 26s (96.2V) LiCo (4.15V per cell) or 30s (96V) LiFe (3.60V per cell).

120V AC >>> 108V DC observed through multiple sizes and types of bridge rectifiers , (1A - 30A.)
But some alternate samples might vary, test to confirm!

15A AC outlet provides ≤1500w charger at ~≥90% efficiency.
20A AC outlet provides ≤2000w charger at ~≥90% efficiency.

Requires AC power cord and ≥20A bridge rectifier (Available for ≥$2)
Current regulation regulated by breaker, batteries charge C capacity, BMS or other?
Gauge and length of AC wire could "trim" current?

All charge voltages are based on 120V.
115 or 110V might necessitate alternate cell count. eg. s26-29 AC rectified charger + 1s-4s charger

30A bridge rectifier


* Do not add capacitor to smooth DC current!
Might produce an initial, damaging, surge of ~170V !!!
I've been building DC led lighting using rectified AC >>> DC through LEDs in series.

See also - 500w bulk charger
MeanWell S-150-(12-24) + any generic S-350-48 MeanWell clone

Maybe I should mention I actually did this two years ago.... I blew the diodes instantly and killed the breaker and blew up my stereo that was plugged into the same outlet so.... Yes please get video

 

[megacycle]

Fuses for experimenting, open you up to a world of liability, for a few dollars for the closer protection offered by a circuit breaker, I can't understand anyone using fuses for this job, when connected to a wall outlet, or for that matter a large fault current capable, battery pack, when 1S could easily deliver 300A, then you have them paralleled, like 3P, with this juicy bulk charging set up and it could deliver close to 1000A into a short circuit and you just got badly burnt, because there was no fuse or it was automotive or not closely rated so as to allow your wheel spins up the hills.
Senario, your correct sized fuse just blew, for whatever reason, during experimenting, you check the circuit, no obvious signs, so you replace the fuse and pop it again, with a breaker, it won't turn on to the fault, the switch will drop back, as soon as you try to latch onto a fault.

Did a video of a close rated dc breaker on a battery pack, recently.
The same amount of damage limitation could be as well given on a domestic a.c. wall outlet, with a close rated breaker, 6 or 10A, with a tight curve, like a 'B' or 'C'.
https://www.google.com.au/url?sa=t&source=web&rct=j&ei=6gY3VKD9A9XgoASqkYCYDg&url=http://www.youtube.com/watch%3Fv%3DOnOsSmbXCoQ&ved=0CC8QuAIwAg&usg=AFQjCNFEoI0okgAj-Yh2GmgVVv3yRwyW9g&sig2=JkZg8TFx2CuJCGN4PvppVQ

 

[Matt Gruber]

i find most CB's don't trip fast enough. just look at the data sheet! a 1 amp fast blow glass fuse is hard to beat for a quick test, if you happen to have a box of them.
i have conducted this experiment entirely by chat! no electrons were harmed! scr dimmer still in the bag. hard to get shocked by chat
no way ebikes will ever catch on, far too dangerous!

 

[megacycle]

i find most CB's don't trip fast enough. just look at the data sheet! a 1 amp fast blow glass fuse is hard to beat for a quick test, if you happen to have a box of them.

Don't trip fast enough for what? The 2 or 3mS short circuit operation time.
Did'nt you watch the video?, did'nt you notice, that I could hardly tell the short circuit had actually occured.
What are you using that can't handle the trip fault short circuit or overcurrent, that would be delivered by a , 240V, 10A CB or 110V, 20A equivalent, for this 2000W circuit.
Your 1A is useless, for almost any testing of a 2000W circuit, you'd be just wasting time and money looking for one type of fault, a dead short circuit, with no load connected, with this fuse.
What I'm suggesting, is trying to make safer, fault conditions, when experimenting with these circuits, it won't make it completely safe, as nothing will, except having a proper functioning circuit, as component failure can still be catastrophic and you have to protect yourself against that and electric shock

 

[DrkAngel]

WARNING! in case you didn't know Electricity is dangerous! ... to placate the fear mongers ...

Looks like ...

AC >>> GFCI >>> restricted range SCR >>> bridge rectifier >>> inductor >>> V-A-Ah-W meter >>> battery + axillary DC device ... NO CAPS!

Will be my next trial (Still waiting on SCRs delivery)
GFCI cord pulled from $2 hair dryer
Axillary device should prevent the voltage "creep" as target voltage is neared.
Not knowing the proper value-size inductor necessary, I reason that as target voltage is neared, and amps reduced, any size inductor will become more effective.
I ordered up 3 and 6A 100uH Toroid inductors, and can pull some larger ones from old computer power supplies.

GFCI = not necessary, but might as well play it safe ...
V-A etc. meter not necessary for function but necessary for proper regulation and monitoring. Plus, I like to know exactly what is happening.

I also test conversion efficiency.
I had small APC UPS die on me, so I pulled the battery, bypassed some circuits and installed an AC Volt - Amp - Ah - watt - kWh meter to measure 3 of the outlets.

I can directly compare to the DC meter

WARNING! in case you didn't know Electricity is dangerous! ... to placate the fear mongers ...

 

[DrkAngel]

WARNING! in case you didn't know Electricity is dangerous! ... to placate the fear mongers ...

2000w SCR is a Silicone Controlled Rectifier
Extremely simple and inexpensive! < $5

They provide effective voltage regulation.
In series with a bridge rectifier they also can supply adjustable "rough" DC current.

My first mod will be to trim for 110V USA voltage.

Present adjustment is a 500k dial pot in parallel with a 1M(?) multi-turn pot, (220V model).
Replacing 500k with 200k should make much more 110V friendly.

LED testbed
Then further "adjust" for lower voltage use.
Such as 27- 35V high output LED modules.
(I charge at ~29V and ~36V - 7s and 9s packs)
To test, I will mount a 30w 34V DC LED chip on a good heatsink
Adjust voltage to rated 34V
Confirm a match to the rated ~900mAh 30w DC input.
Compare to my AC metered supply, to confirm Watt and determine rectifier efficiency %.

And run continuously, looking for:
LED, mAh, watt, lux output deterioration.
To determine LED durability when subjected to rough DC.

Yes, and of course, I will test, document and report on battery charging feasibility.
Will run initial battery charge circuit through a 100w light bulb, as safety-fuse-current regulation.
Next stage will be a minimal voltage differential with a low amp fuse as safety.
I will begin with SCR set to minimal voltage , then adjust up, monitoring volt-amp-watt level.
Bridge rectifier will prevent circuit voltage backwash.

At minimum, this device should provide adjustable voltage and current for charging, though you might need to manually restrict current by reducing initial charge voltage.

There is still the bleed through of rectified voltage peaks to consider.
A minimal drain device in parallel with battery might regulate this effectively?

Received replacements:
Replaced 500k pot with 200k and was able to use on board 1m multi-turn pot to adjust as low as 10V.
Tested low voltage as high as 75V - low adjustment. (75V - 118.9V full dial travel)
Placing a 3rd pot, or proper value resister in series with main adjustment pot should allow restricting voltage range rather tightly.
As long as there was a few watt drain, voltage maintained nicely ... 100w light bulb @ 10V.

There is an audible hum from SCR and light bulb at minimal voltage.
Removed drain and voltage metered at a full 118.9V AC. (important to maintain low watt secondary drain ≥10w)

Did a quick test with LEDs through a bridge rectifier, adjusted nicely from 75V - 108VDC.
Waiting on inductors for further DC tests.

Oh ... also got the "220V" only version and works identical to the more expensive 110 - 220V version.
Worse ... did not need to swap the 500k pot for 200k, oem 500k adjusted to ~10V, no problem.

WARNING! in case you didn't know Electricity is dangerous! ... to placate the fear mongers ...

 

[DrkAngel]

WARNING! in case you didn't know Electricity is dangerous! - to placate the fear mongers ...

So far ...
SCR AC speed control - dimmer ... is a PWM (Pulse Width Modulation), same process as motor "controller", current control which emulates voltage reduction-limiting in many ways.
Bridge rectifier turns this regulated AC current into a "rough" DC current.
This rough DC has 2 "forms" , off ... and varied, between ~65V-165V averaging ~105V DC.
Running this rough DC through an inductor, reputedly, can smooth this rough DC current to a relatively stable-smooth DC current at lower voltage.

The closer to full voltage (~105VDC) will "smooth" much easier.
I will need to experiment with differing currents and values of inductors.
Method will be to add a DC cap to the "smoothed" DC, while current is being used. A comparison of voltage without cap in circuit to cap in circuit should determine effectiveness. ... cap will indicate peak voltage spike?
Of course, as in battery charging, voltage should become smoother as current reduces when target charge voltage is neared.
There is the problem of the SCR bleeding through full-peak voltage at minimal current! This seemed to be handled nicely by the addition of a minimal secondary-parallel draw, ~10w inductive drain via light bulb.

SCR can be adjusted via on board multi turn pot to set minimum "voltage range" through large dial pot.
The addition of a 3rd pot or resister in series with dial pot should limit high voltage range.
Purpose of which is to allow more precise output "voltage" adjustment.

While more difficult and less ideal, I will attempt a ~24V-<40V range for my preliminary tests.
Not ideal because DC current will be much "rougher", and will require greater "induction", the lower from "full" ~105VDC.
But I only use 7s - 9s battery packs and my LED experiments use 27-38V modules.

Oh!
~$2.49 - SCR
~$2.00 - 30A Bridge rectifier
<$0.50 - inductor
=
< $5

Probably requires larger, more expensive, inductor(s) tho ...
Hopefully, multiple inductors will be more effective, got lots of 10 ... (advice on in series or parallel being preferable - more effective?)

WARNING! in case you didn't know Electricity is dangerous! - to placate the fear mongers ...

Seriously tho ... use care and safety protocols whenever using electricity.
Rubber gloves?
Safety glasses when near components (caps especially! ... hearing protection? Caps be as loud as a gun shot, if they "go off".)

 

[DrkAngel]

AC >>> GFCI >>> restricted range SCR >>> bridge rectifier >>> inductor >>> V-A-Ah-W meter >>> battery + axillary DC device ... NO CAPS!

Primary goal is a cheap, reasonably safe, high output charger.
Appears to be practical, though ...
SCR, monitored by volt-amp meter, must be set at reduced voltage to restrain amperage to reasonable < 20A current.
(Less than 10A recommended to prevent blowing fuse to pop machine and angering store owner!)
Constantly monitored and adjusted to maintain desired charge rate.

With sufficient inductor and a minimal parallel secondary current drain, setting desired voltage looks, preliminarily, to be reasonably attainable and safe.

OOPS! Almost forgot:
WARNING! in case you didn't know Electricity is dangerous! ... to placate the fear mongers ...

 

[Punx0r]

Primary goal is a cheap, reasonably safe, high output charger.

I was trying to stay away from this thread as I don't want to appear overly negative or condescending. I also only have a rudimentary understanding of electrical theory. However, I have to take exception with your quote, above, as you have failed from the outset if you take the average person's expectation of "reasonably safe".

Unless you have adequate isolation between the charger output and the mains, you will never have anything like a safe product. Such isolation has been a requirement in electrical safety for a very long time, and isolation failures do result in fatal electrocutions (shoddy Chinese SMPS products being a popular source).

I also can't shake the feeling that you are merely guessing when it comes to selecting components, their values, or the nature of the charger output waveform.

 

[DrkAngel]

WARNING! in case you didn't know Electricity is dangerous! ... to placate the fear mongers ...

Primary goal is a cheap, reasonably safe, high output charger.

I was trying to stay away from this thread as I don't want to appear overly negative or condescending. I also only have a rudimentary understanding of electrical theory. However, I have to take exception with your quote, above, as you have failed from the outset if you take the average person's expectation of "reasonably safe".

Unless you have adequate isolation between the charger output and the mains, you will never have anything like a safe product. Such isolation has been a requirement in electrical safety for a very long time, and isolation failures do result in fatal electrocutions (shoddy Chinese SMPS products being a popular source).

I also can't shake the feeling that you are merely guessing when it comes to selecting components, their values, or the nature of the charger output waveform.

Well ... "the average person" ... who knows what GFCIs, SCRs and inductors are ... should have some basic understanding of electrically "reasonably safe" ... ?

Project is listed as a "goal" ... not solution!
A work in progress ...

I will post a big sign when and if positive and final results are achieved!!!

So far:
AC through SCR through bridge rectifier tested to provide regulated DC for light bulb, motor and LED use.

GFCI ... without any caps, is about as safe as possible! (but will test GFCI with inductor in circuit to confirm effectiveness)

"Waveform variable" is to be regulated and determined, by stated process(es).
Helpful, is that, even a small inductor becomes very effective as target voltage is neared! (minimal current and minimal voltage differential)

WARNING! in case you didn't know Electricity is dangerous! ... to placate the fear mongers ...

 

[Punx0r]

I count seven possible statements in your last post. I cannot determine a coherent message from any of them.

 

[DrkAngel]

WARNING! in case you didn't know Electricity is dangerous! ... to placate the fear mongers ...

I count seven possible statements in your last post. I cannot determine a coherent message from any of them.

Apparently you require certainties.
For the scientific mind, there is no such thing as "certainty".
The "scientific method" requires a nearly absolute abstinence from "certainty"!
Possibility - probability is the essential form and mindset for any type of scientific enterprise or investigation!

Otherwise ... we'd still be stuck on a flat Earth ...

WARNING! in case you didn't know Electricity is dangerous! ... to placate the fear mongers ...

 

[Punx0r]

I give up.

 

[Alan B]

You have left out overcurrent protection devices. Two are required, one on the input and one on the battery (each power source). Fuses or circuit breakers rated for the proper service are needed.

Just to deflect a common misunderstanding, a GFCI is NOT an overcurrent protection device. It trips on current imbalance (leakage) and does not care about the amount of current in the circuit.

You should make a list of failure modes and analyze each to make sure that appropriate results occur. For example the SCR shorts, or the diode bridge shorts, then what happens next determines how safe the design is. If no part of the circuit can be touched (shock hazard), and the frame of the bike is grounded, and the power sources are protected by overcurrent devices, and no failure mode causes the battery to see excess current or voltage (or provide a path for a user shock) then it might be safe.

Circuits that don't have isolation are generally required to be "double insulated" which basically means that insulation is designed to prevent ANY failure from causing a user shock. More here: http://www.double-insulated.com/

I would also recommend computing the value of inductor that you require. The equations are simple. Trial by fire is not advisable, necessary or efficient.

Another good technique is to build and test a spice model of your design. You can learn a lot more without burning up parts. LTSpice is free software.

 

[spisska]

You have left out overcurrent protection devices. [...]

The people driving this thread have already made it clear that they want to explore all the ways a person can hurt him or herself in playing with electricity, and that anyone who calls into question their lack of respect for the fatal energy in electricity is nothing more than a "nervous Nancy".

So, as I said before, let's just let this thread run until it inevitably becomes an account of a near-fatal shock, or an electrical fire that destroys the whole project.

The thing about wheels is that they already exist and don't need to be reinvented.

For the scientific mind, there is no such thing as "certainty".
The "scientific method" requires a nearly absolute abstinence from "certainty"!

Quite the contrary, science is about building certainty upon certainty. Water boils at 100C. Do you really still need to test that? Is it not already certain?

To put it another way: Gravity is just a theory, right? If I throw myself from my roof, I might not fall to my death, because I can choose not to fall, right?

But by all means, keep playing with lethal amounts of electricity with little in the way of safeguards. Your results will certainly provide valuable data for those who survive you.

And by all means, keep leaving here detailed instructions for inexperienced people to kill themselves with electricity. Since humans are no longer threatened (by and large) by big cats or wild dogs, we need other mechanisms to carry on natural selection.

Do you ride a proper motorcycle? I hope you don't wear a helmet, because people on the internet have proven it's more dangerous to wear a helmet than not to.

Best of luck! Make sure you the floor of your workshop is nice and wet while you're carrying out your high-voltage experiments.

 

[megacycle]

Like all 'badboy' threads, the thread needs an intro and disclaimer.
This is what many do when they start a thread that is potentially hazoudous.
Anyone can open up 110/240 or even 415V, with various even higher voltages available inside mains operated devices and go poking around inside them.
All you can do is warn, by the standard safety procedures a technician might use when prototype testing, carrying out a repair etc.
It's not up to individual's on technology threads to be 100% responsible for individuals who do not go by warnings and go using incorrect protective devices and lack personal protective equipment, if you put your hand in the fire....But you could if you had asbestos gloves on.
If there's good modelling available on spice, etc that would be good.
I've found I was getting some success with the triac but need better trigger circuitry which I've been looking for.
As this project is still underway it's irrelevant to talk about class of insulation for finished device, it could be I, II, it depends on the finished item.

 

[Matt Gruber]

when you don't read the posts, you appear clueless.
he already tested it SHORTED and not only was he not killed, his house did NOT burn down!
how do you guys explain that?
he said it smoked and was ruined. had to order more. this dimmer is no bad boy!

 

[DrkAngel]

Proper warning?
WARNING! - DANGER!

There seems to be a cadre of ES member who feel most eBikers are totally ignorant of electricity and its dangers.
Unless you understand electricity, its theory and dangers ... do not read this thread!