grid charger/balancer

[rayholan]

Originally Posted by buzzkill

i need to go back to school for eletrical engineering so i can understand more of this talk thats going on. im just lurking back in the shadows waiting for the final product so that i can buy one of these.

Yep, me too on both counts.

[Mike Dabrowski 2000]

The grid chargers are actively being worked on, and the code development is started, but new projects keep coming up.

I got a call from the WWU x-prize team last night, and they want to drive the complete x-prize car, trailer and crew out here to get the intermittent IMA problems sorted out.
They will spend several days if required.
http://www.progressiveautoxprize.org...ton-university

How can I refuse a real consulting job on a state of the art scratch built car.
The car has a big lithium pack, and an additional electric motor after the clutch for pure EV mode operation, along with a full Insight drive system.
Until then, I will see how far I can get with the grid charger design and fabrication.
Thanks for being patient.

[crx_rogus]

Originally Posted by buzzkill

i need to go back to school for eletrical engineering so i can understand more of this talk thats going on. ...

That's basically what I'm doing in October, part of transitioning from an obsolete newsprint-related career... I have a little electronics workshop at the end of my bed, and allelectronics.com has been a good parts source. My well-yellowed Forrest E. Mims III workbooks have been most handy, plus an old Heathkit vacuum tube o'scope and a low-cost Hz/duty cycle/VOM.

LM34s + op-amps = interesting... Eventually doing away with the rude, crude attic fan t'stats for fan and charger control, already made a very simple differential t'stat for a window fan at least, another version would probably work great for limiting battery pack temperature rise during charging.

[Mr. Mik]

Originally Posted by Mike Dabrowski 2000

MR MIK
This document:
http://www.national.com/ds/LM/LM124.pdf
Page 9 Power Amplifier: shows how to use an NPN power transistor to drive high side big loads with an op amp.
Lamp driver page 10 shows a low side switch


Also you want to put a diode across the relay coil to prevent the inductive flyback pulse from blowing the transistor or op amp.
have fun, it is a very versatile circuit.

I sheared enough chassis to make 5 of the 350ma universal chargers, and 7 of the overnight chargers.
Also started setting up the microcontroller.

Thanks again, Mike, I did indeed forget the diode...should have known that! But the LM324 seems to be fairly resilient, I must have turned the relay off hundreds of times (without a diode) while playing around with the hysteresis part of the circuit and experimenting.
Here is a schematic of how I plan to integrate it into the Special Freddy NHW10 EQ charger:

The trimpot R5 will probably be replaced with a fixed resistor in the final product.

More details here: https://www.endless-sphere.com/forum...284578#p284578

Mik

[TRI]

I'm not a frequent reader I'm afraid. Sorry if doublepost.

If my battery goes below half I plug it into the gridcharger for some hours. I don't always top it off.
The next drive it takes very, very long sometimes (up to 20 minutes) until the BCM recognises the different battery charge level than before. How to short this period? Top it off?
In this scenario I'm also afraid of overcharging my battery as the BCM is still charging as it thinks the battery needs it. True or not? Danger or not?

[Mr. Mik]

Originally Posted by Mike Dabrowski 2000

...
...
Get some LM324's and play with them. There are tons of circuits available online that show the many possibilities that op amps bring.
New schematic with hysteresis and explanation.
http://99mpg.com/Data/resources/down...gersafety2.pdf
Data sheet with example circuits for the LM 124,224,324 op amps:
http://www.national.com/ds/LM/LM124.pdf

Have fun

I did have lots of fun indeed - until the hysteresis problem was suddenly back when I thought I had it all together in the charger!

Bugger! I thought it was all finished!

When the 6V DC supply is also powering the cooling impeller motor, then the voltage fluctuations introduced by the motor are so great that the LM324 output at pin 14 oscillates wildly around the switch-over point.

Have you tried your setup with the cooling fan running yet? Or do you not plan to power the fan from the same 12V supply as everything else?

A solution to the problem might be a much lower value resistor for the hysteresis between Pin 14 and pin 12.

Maybe 1kOhm instead of 4.7MOhm, or something like it. Unfortunately it's not easy to attach a resistor wheel to the pins 14 and 12 in my charger. I'll have to take it apart again to experimentally determine the best hysteresis resistor value. Calculating it is beyond my capabilities at this stage!

[Mike Dabrowski 2000]

You don't want to lower the resistor or your hysteresis will be huge.
A much better solution is to low pass filter the 12V power supply for the comparator with a big capacitor 500-1000Uf. That will stabilize the voltage so the fan noise on the 12V supply cannot get to the comparator.

100 uf across the PTC, another on each of the setpoint potentiometers center tap should filter those signals further reducing the noise.

[Mr. Mik]

Originally Posted by Mike Dabrowski 2000

You don't want to lower the resistor or your hysteresis will be huge.

I have not really understood the whole hysteresis concept/principle, yet. So I may well misunderstand what "huge" hysteresis means in practical terms.

I have spent the last few hours with a resistor wheel attached in parallel with the 4.7MOhm hysteresis resistor.

I ended up soldering a 20kOhm resistor in parallel with the 4.7Mohm resistor, just because it is to hard to get the 4.7MOhm resistor out!

The effects of changing the hysteresis have been varied and somewhat unpredictable (for me, anyway)! The cut-in and cut-out point get further and further removed from each other the lower the resistance of the hysteresis resistor gets. Below 33KOhm I get pretty good suppression of the on-off-on-off behaviour.
For the "Special Freddy" charger it is extremely important to avoid rapid switching off and on, because sooner or later the sine wave on the motor-run capacitor will be "opposite" to the voltage when it was switched off last time - that creates an excessive voltage across the capacitor, up to 576V. Not good!

A much better solution is to low pass filter the 12V power supply for the comparator with a big capacitor 500-1000Uf. That will stabilize the voltage so the fan noise on the 12V supply cannot get to the comparator.

100 uf across the PTC, another on each of the setpoint potentiometers center tap should filter those signals further reducing the noise.

I was pondering these options, without knowing what exact capacitor values to choose - I was hoping you might mention them! Thanks!

But I broke my own rule 1 for prototyping: USE A BIGGER BOX!

And now I have very little, if any, space left in the box.

Quite apart from all this, the charger is not working at all. I think it might be due to the solid state relay having been damaged due to reverse polarity on it's "coil" terminals. But that needs more testing, tomorrow. I've had enough of it for today!
This is what I am trying to put together:

But often a good nights sleep solves the trickiest problems......

Thanks again for your help!

[Mike Dabrowski 2000]

MR Mik,
I can see by your questions that you need some lessons in basic electronics, and this is not the purpose of this thread. Get a good basic electronics book, and experiment with what you learn, and eventually it will all become clear.
It all gets down to ohms law.
Fully understand that formula and how op amps work, and you will understand how the value of the 4.7 M resistor will effect things.
No shortcut to understanding.

[Rush]

Mike,

I got your balancer built and started to try it on a 2nd pack that I just got. Then thought better of it, cause I want to see what the individual sticks are like, so I took it apart and will start using a MRC Brain 989 that I got for that very purpose. I'll put the balancer on it when I run the sticks thru some cycles.

The LED that I got (3 wts, 450ma) came only as an LED, no leads to hook it up with. Is there a 'carrier' with hookup leads that I can get for it?

Thanks