Diy Brushless Spindle

[vtcnc]

That battery is rated for 60A constant, or 90A for 10 seconds which is plenty. Since my PSU has variable voltage output and current limiting I can set it to just below the fully charged voltage of the battery (i.e. <22.2*4.2) and it will never overcharge the battery, which is very important since overcharging a lipo battery is a good way to start a fire. So whatever PSU you get if you decide to use in combination with a battery will need to have good stable voltage regulation below 25.2V. Two computer ATX PSUs in series is nice and cheap and will give very close to 24V, however it is CRITICAL to ensure they are electrically isolated before putting them in series. The battery would never fully charge, but that's a good thing if anything as it increases it's life expectancy. You could get the battery first, use it to power the motor to measure the current then buy a PSU to suit.

Thanks Jonathan for this very helpful information. I hadn't realized that it was possible to connect ATX PSUs together in series to increase voltage -- just assumed they were regulated in a way that would prevent this. Makes sense really, when I think about it. Battery cells have nominal voltages and can be series connected into a battery of higher voltage. Somehow I got hung up on the regulated part of it.

Anyway, I've gone ahead and ordered two ATX supplies with 12V 30A outputs, and looking forward to making a 24V supply with them for a spindle PS. I will isolate the negative buss from the case, and I know about setting up the switch line and adding a starting load resistor on the 5V lines to keep the supplies running.

I build and fly R/C planes, so I'm familiar with the rest of the motor side components. I have two 5055 1500W rated motors -- one 400 kV and one 540 (I believe) -- both have 8mm shaft dia. I have an 8mm ER-11 collet spindle, and collets.

ps. I also wanted to post a possible correction to the above -- I think the bolded text above should read "(i.e. <6*4.2)"

Thanks for your PSU info!