grid charger/balancer

[retepsnikrep]

Originally Posted by Artric

As I found out before though, the BCM must be started BEFORE you start a charger, or it will not count the charge. Any easy way to delay the charger(s) for a few seconds? I think I might just need to install a separate switch for the RS-25-12 from the rest of the charger.

Thanks again!

As mentioned previously this is because the BCM calibrates it's very accurate current sensor to what it believes to be zero amps every time it turns on. If charger is on first then BCM sets sensor to zero when in fact current is already flowing. So current flow is ignored. In fact if you then turned charger off and left BCM on it would register a negative current drain and soc would slowly fall even though no current is flowing.

[insight1]

Since the Radioshack resistors out of the question. Which is a good site to buy the resistor you recommend 6.8 Ohm - 5W?
Thank you

[Mike Dabrowski 2000]

No I guess I lost you. Sorry

The radio shack resistor of 8 ohms and 10 watts is fine, as long as you use a 160 ohm resistor in series with the LED instead of the 47 ohm.

The series resistor can actually be any resistance between 120 and 200 ohms, with 160 producing 10 ma LED current

[insight1]

Originally Posted by Mike Dabrowski 2000

Ohms law
Volts = Amps x Ohms
Amps = Volts / Ohms
Ohms = Volts / Amps

Watts = (Amps X Amps) X Ohms

The charger puts out CC 350ma, so with a 6.8 ohm, the resistor will have


volts = amps x ohms
2.38 = .350 x 6.8

watts = (amps x amps) x ohms
.833 = (.350 x .350) x 6.8

2.38 - 1.2 = 1.18 excess

ohms = volts / amps
118 = 1.18 / .01

watts
.012 = (.01 x .01) x 118

lets run the numbers for the 8 ohm.

volts = amps x ohms
2.8 = .350 x 8

watts = (amps x amps) x ohms
.98 (.350 x .350) x 8

1.6 = 2.8 - 1.2

ohms = volts / amps
160 = 1.6 / .01

watts
.016 = (.01 x .01) x 160

Now this is mine calculation based on the above information:


I have 5 ohm resistor and Red LED 1.7V and 20mA

volts = amps x ohms
1.75 = .350 x 5

watts = (amps x amps) x ohm
0.613 = (.350 x .350) x 5

1.75 - 1.7 = 0.05 excess volts

ohms = volts / amps
2.5 = 0.05 / .02


Is this a good solution or am I wrong?

[Mike Dabrowski 2000]

Good in theory, except for the pulse of higher current when the unit is first turned on under load, which would pop the LED just like it did the 1 Watt LED.
Say the current pulse hits 1 A during startup, your 5 ohm resistor would have 3 times the 1.7V across it,or 5.1V and so would the LED, which would probably pop the first time.
The resistor in the LED circuit would allow the 10ma nominal to reach 30ma during the pulse, which the LED can safely take for the short pulse with no issues.
No LED resistor, the LED sees 1A pulse. Possibily Magic smoke?
With resistor, the LED sees 30ma pulse. No Magic smoke.
Leds current does not change linearly with increased voltage like a resistor, they act more like zener diodes. As the voltage across the 5 ohm resistor rises, the led current will shoot up very quickly absorbing all the energy over the 1.7V

[Mr. Mik]

Hi Mike,

how is the grid charger coming along?

The Prius NHW10 crowd has a few Techno S2000 scanners and an (incomplete) English translation for it available now. That'll go a long way to help fixing them and keeping them healthy, but we still need a grid charger....

Thanks for your efforts, Mik

[Mike Dabrowski 2000]

Among the many other things I am doing, progress is being made on the charger every day.
I have the software pretty much finished, except for the serial I/O, the final hardware design prototype is 90% finished, the internal harness for the Insight and Civics have been prototyped, and I hope to get the chassis design and drawings to several sheet metal fab places for quotation next week.
The control panel design is also nearing the quote stage.
The circuit boards will be ordered after the first of the year.
Once I have those quotes I will be able to firm up my cost for parts.
When the chassis and PC boards arrive, I will build several units of each type to see what the labor cost will be, and then I will be ready to start selling them, but not until I come up with a solid liability waver, and do some very comprehensive install instructions, after doing several installs.
Sorry this is taking so long, but I had a lot of distractions, and had to learn the C language.
The NHW10 prius with the >300V charger requirement will still need an external voltage booster.
The devils in the details, and I am being very careful to not forget any.

[3-Wheeler]

Mike,

Any word on when you expect the parts for the DIY MIMA kits?

I contacted you mid-November and you were anticipating mid-December.

Thanks, Jim.

[darwin9x]

As I was getting same education (Grid Charging/Battery Cell Balancing) I found this great whitepaper on the subject:

http://focus.ti.com/download/trng/do...0and%20How.pdf

[Mike Dabrowski 2000]

Jim,
Your question comes at a perfect time.
I have spent a good part of last week building up plug in adapter boards, joysticks, displays, and testing only to end up with the last 6 MIMA systems that are ready to ship.

If I add up the hours invested, and the cost of the parts, as I stated before, I could make more money working at Burgerking.

I don't think I will try to use up the remaining boards by building more MIMA plug in systems, as it will simply take too much of my time.
So the PLUG in MIMA system as it presently exist will end when the last 6 are sold.
The DIY kit will continue to be available while I have boards, but will not include the parts.
Sorry.