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Comments by Jan

  • Understanding battery capacity: Ah is not A

    Understanding battery capacity: Ah is not A

    - 28 June 2019

    Hi, Jimmy.

    I think that depends too much on the details of the particular batteries and what exactly they've been through. Age-wise, those 4 months don't seem like too much of a difference, and 65 cycles also doesn't seem like that much, so my guess is you'll get more life out of the 2.0 Ah battery.

    - Jan

  • Understanding battery capacity: Ah is not A

    Understanding battery capacity: Ah is not A

    - 26 June 2019

    Hi, Maxwell.

    Since we are talking about batteries and DC power, a transformer (which is for AC power) is not quite the right term; something like DC-to-DC converter is more appropriate. In your case, we are talking about just reducing the input voltage, so you could use a switching step-down regulator that can be around 90% efficient. Having double the voltage with the same amp-hour capacity means double your energy, so as long as your conversion to the lower voltage is more than 50% efficient, you will get more run time with the higher voltage. However, your battery will be twice as large, so you could probably just get a 11.1V battery with 12000mAh in the same size as the 22.2V 6000mAh one, and then you don't have to bother with the voltage conversion at all and get double your run time.


    - Jan

  • Understanding battery capacity: Ah is not A

    Understanding battery capacity: Ah is not A

    - 29 April 2019

    Mark,

    I expect the maximum allowed current to remain the same whether you have multiple batteries in series or not. One battery cannot tell if there is another battery somewhere else in the circuit; all it has is the voltage across it, which would still be 6V, and the current flowing out of it (or in, if you're charging it).

    - Jan

  • Understanding battery capacity: Ah is not A

    Understanding battery capacity: Ah is not A

    - 14 March 2019

    Hello.

    The "225 AMPS" might be sloppy labeling, but it might also be the maximum recommended current the battery can supply, or even an outright scam, so I would not go with that option if that is really what it says. C/100 vs C/20 is probably about discharging in 100 hours vs 20 hours, so using the 20 hour value is probably a better estimate for you. Given all of your confusion, I would be worried about your 588 Ah requirement calculation, but if it's correct, three of the 190 Ah batteries would almost cover you, so 4 might be enough. Going to 6 because of your 50% discharge guideline would give you more room for error, though that 50% rule might also vary with battery type. This is again assuming you need 588 Ah at 6V, in which case you'd put all the 6V batteries in parallel.

    I don't know your time and cost constraints, but you could start with a smaller quantity and just test it. And if you need more run time, add some more batteries.

    - Jan

  • Understanding battery capacity: Ah is not A

    Understanding battery capacity: Ah is not A

    - 1 March 2019

    Hi, Keiran.

    No, you cannot trade off the voltage for current in your jack. That 1A rating is going to come from things like how much the contacts or some other parts the current goes through heats up, so if you put 3x more current through, it's going to heat up possibly 9x faster (for a fixed resistance, power goes with current squared). 1A sounds low for a power jack, by the way, so it's possible it's a really cheap unit or they're being really conservative with the rating.

    Separately, you should also not connect the AC adapter straight to your battery and expect it to act as a charger. Best case, nothing will happen (i.e. you also won't charge your battery); quite possibly, you'll also break something.

    - Jan

  • Understanding battery capacity: Ah is not A

    Understanding battery capacity: Ah is not A

    - 19 February 2019

    Hi.

    The 12V to 5V conversion should get you longer battery life as long as your converter is not really inefficient. With a 100% efficient conversion, you would get 12/5 times that seven hours, or 16.8 hours. Getting at least 85% efficiency should not be too difficult, and that's what you need to multiply your final answer by, so 14 hours should not be too difficult. Getting 15 hours would require 90% efficiency, and that is still pretty realistic.

    - Jan

  • New products: 16-channel QTR MD reflectance sensor arrays

    New products: 16-channel QTR MD reflectance sensor arrays

    - 31 December 2018

    Thanks for the feedback! Making a version of these with a microcontroller on board has been on the to-do list for a while, and I hope to get to it next year (I'm writing this on December 31).

    - Jan

  • Electrical characteristics of servos and introduction to the servo control interface

    Electrical characteristics of servos and introduction to the servo control interface

    - 27 December 2018

    Hello.

    This is not something to calculate (if you trusted your battery capacity, you could do some calculations based on how long it lasts, but you could only do that for lighter loads since forcing your servo to some max load scenario for a prolonged period would likely destroy it). So, you should just put a current meter in line with your servo and see how much it draws. That would typically show you average current over maybe a tenth of a second or however fast your meter updates. If you want to see the faster peaks, you would need to use an oscilloscope.

    - Jan

  • Continuous-rotation servos and multi-turn servos

    Continuous-rotation servos and multi-turn servos

    - 23 November 2018

    Hi, Gordon.

    I have not heard of such a servo. I don't know if you need the actual feedback and the higher torque you get from typical hobby servos, but perhaps you should look at stepper motors, too (along with our Tic stepper motor controllers: https://www.pololu.com/tic ).

    Please share if you do find anything.

    - Jan

  • Servo control interface in detail

    Servo control interface in detail

    - 20 August 2018

    Peter,

    Yes, there is a control board in the servo that takes the signal you send it, compares it to the position feedback on the servo, and drives the motor appropriately. You can look at our Jrk motor controllers to get more of an idea of what could be going on inside the servo:

    https://www.pololu.com/product/3142

    The Jrk controllers have a lot more interfaces and features than what you would find in typical hobby servos, but the basic idea is the same.

    - Jan

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