I have a couple of Black and Decker Litium-Ion 20v batteries

I got them off Amazon

I need them to power a couple of 12 volt stepper motors and of course a nerdkit.

So what would be the best way to furnish 12 and 5 volts?

How will I know when to recharge the batteries?

They are rated at 20 volt fresh charge and 18 volt under load.

Also how would I measure the voltage? and how to make a voltage indicator? I have a 10 x 15 LED array.

Thanks for the help,

Ralph

Use a switching regulator such as this for 12V.

You could use one more count of the above module to get 5V from 12V as they are variable. Or Use another switching regulator such as this for 5V.

For voltage measurement, get one of these.

If you want to build the regulator circuitry and the voltmeter on your own, then, it is possible. They are interesting projects on their own. But, you may be side tracked to build these (nevertheless good learning exercise), I am not sure what the stepper motors are going to drive. So it depends on you project. And how much time you have on hand.

-Raja

I just bought a few of those meters and 5V supplies. Good links!

I agree, use the switching supplies to cut the 20V to 12 or even 9, then regulate it again for the 5V. These appear to be very versatile units. Now, I am off to locate some AC and DC ammeters too.

Thanks, what about recharging the 20 volt batteries?

What would be the best time/voltage to recharge?

The steppers (at .4 amp) are only used intermittently so they will not be a constant drag on the batteries. The batteries have a 1.5ah rating so they should last a long time with intermittent use.

Apparently I can recharge the batteries at any time they do not have to be completely discharged before recharging so I could do a run time counter in Nerdkit code and just recharge after a certain time elapse but I "think" I would like to do voltage drop. I'd also like to have a led voltage indicator.

Ralph

Hey Raja, on the voltage measurement module what is the White Wire: Measure + for?

I'll find out as I ordered some, thanks!!

Yeah mongo let me know what you find for AC/DC Ammeters.

I actually have some current sense ICs.

They are SMD so I have not gotten around to making up a board to use them.

Ralph

From ebay listing

Wiring: Red Wire: Power Supply + Black Wire: Power Supply -, Measure - White Wire: Measure +

WHITE/BLACK wires are for measuring the voltage of the battery 18 to 20 V. RED/BLACK for power to the voltmeter from your 5 V Nerdkit supply.

-Raja

WHITE/BLACK wires are for measuring the voltage of the battery 18 to 20 V. RED/BLACK for power to the voltmeter from your 5 V Nerdkit supply.

Duh, of course, thank you.

Ralph

Hey Raja, that Voltage meter is so cool!!

Thank you so much for the link.

I really love the size of the whole assemble About 7/8" x 5/8" it can go just about anywhere yet is easily readable and so simple to connect.

Oh I also got the Buck Converter.

I have not played around with them yet but they also look great!!

Now about my 20 volt batteries.

These batteries are from Black and Decker to power lawn care yard work tools.

I have the string trimmer and it is really great, of course I now have 4 batteries so the 15 - 20 minute battery life is not a issue.

Anyway these batteries are considered "discharged" at 17.3 volts.

So in using these batteries to power my two 12 volt motors how will I limit my discharge to ~17 (approximate 17) volts?

I do not want to discharge them further than 17.3 volts for fear of ruining the batteries (Lithium Ion).

I was thinking about putting a Zener Diode in line, Mouser has a 17.3 Volt Zener but I do not know if they would handle the 3 amp start surge current or the 2 amp running current. The datasheet probable has that information but I have not figured out how to read the datasheet yet.

I do not now how practical using a Zener is.

How would you all suggest limiting the discharge or for that matter do I even need to worry about it? Could I run the battery down to the point where the 12 volt motor would no longer run and recharge from there?

Thanks again,

Ralph