Battery life of stick DiddyBorg with motors running

Submitted by lars_the_bear on Fri, 03/11/2016 - 09:04

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Hi

Can anybody give me an estimate of the time that the stock DiddyBorg will run on batteries when in more-or-less constant motion? I appreciate that many factors affect this.

My DB has a custom chassis that is (I would guess) a lot heavier than the stock one (overall weight is about 2.5Kg). I find that I need the motors running at their rated 6V to make much progress, and I'm getting only about 30 minutes of battery life. I was considering using a bigger battery, but that will add to the weight. I don't think that anything is drawing unexpected current -- without the motors running, but with the LED display, ultrasonics, audio amp, and headlights I get about 4-5 hours. With just the Pi it's about 12 hours.

My chassis is made of wood -- it's thin wood, but wood nonetheless. I could rebuild it using perspex -- or just use the stock DB chassis with a couple of extra shelves on top, if I thought it would make a significant difference to the battery life.

Best wishes
Kevin

piborg's picture

piborg

Fri, 03/11/2016 - 11:32

From memory we tend to get between one and two hours of continuous driving from a standard DiddyBorg, depending on how he is driven and what sort of surface he is running on, when using 10x 2700 mAh batteries.

As for weight the standard DiddyBorg complete with a set of batteries weighs 1.5 Kg.
The extra weight will decrease battery life, but I would not expect that the difference in weight is enough to account for the battery life difference.

On a side-note our DiddyBorg Metal Edition is heavier and weighs 2.0 Kg.
For that version we used 12 batteries instead of 10 and saw something like 1 to 1.5 hours of continuous use.
It is not the simplest comparison though because that kit uses the 12V motors we currently have in Red Edition instead of the 6V from the standard DiddyBorg.

When we powered just a Raspberry Pi (B+) from batteries with around 15% load using BattBorg measured the running time as 14.5 hours: https://www.youtube.com/watch?v=6Wj7bu3MkI8
This was done using 8x 2700 mAh batteries (GP 2700), we would expect the 10x AA pack we use with DiddyBorg to last about 25% longer.

What we have noticed is that Bluetooth and WiFi dongles can eat through batteries.
WiFi in particular can be a large drain if it is in heavy use.

I guess the big question is what battery arrangement do you currently have?

cleric boomer

Fri, 03/11/2016 - 12:43

I have not yet managed to run the DiddyBorg for any length of time. Mainly as I completed the build then started to look at moficiations,and the extras I want to add on.

So all I have done is used the webpage UI to make sure it was working correctly.

I used the 10x 2700mAh AA batteries. But I now have the 4S Li-Po battery (14.8v 4250mAh). But I am going to be running the Red Edition with 12v motors, so it will not be a like for like comparison. All I have to do is wire it all up!! I am going to use a switch, and also a shut-down push button.

I was interested to read about the battery drain from Wi-Fi and BT dongles. With my thoughts on repositioning the Pi (I have an extra panel to build a double height DiddyBorg), it maybe that I can store the sensor readings on a USB drive, then connect via an Ethernet cable to download them. Eliminating the Wi-Fi dongle altogether, although the size of battery I have may not be that much of an issue.

Or I can just wire in a 2 line OLED display to show the readings.

"PiBorg" has already responded to a couple of emails, helping me with the concept ideas for the cliff/ledge sensor. I cannot thank the PiBorg team enough.

The only thing that is really slowing me up is my lack of programming knowledge in Python. I know nothing, and I think I need to find a good book or two on learning the nuances of Python programming. I know you know C, and have commented on the use of Python.

Kevin, I like the thought of headlights etc. Making me think..........

Chris

Edited: to "make sense"

lars_the_bear

Mon, 03/14/2016 - 12:23

Thanks. All my testing has been done with WiFi active. I measured the idle current consumption of the unit, and it's about 200mA without Wifi and maybe up to 300 mA with WiFi active. Of course, it's not actually transmitting all the time. I also have the camera module active, which includes a measure of image processing, if only to get JPEGs to a browser. There are two ultrasonic units pinging at ten times per second, and they draw a bit of current as well, I imagine.

I'm using 10 x 2700mA NiMH batteries to a total of 12V or thereabouts.

I suspect that the bulk of the weight of my unit is in the motors, and that's probably true for the stock DiddyBorg as well.

My impression is that it probably won't hugely improve battery life if I rework the chassis. Maybe a little, but not enough to justify the extra effort and expense. The short-ish battery life is less of a hassle now I've bought a charging connection out of the chassis so I can fiddle with the unit whilst it's on charge.

PS. For what it's worth, my headlights are two so-called 1-watt LEDs. I say "so-called" because they actually measure out a 0.25w each. That's still bright enough for the camera to work in the dark. so long as you don't need to see more than a few feet ahead. They're switched by a FET, which is an inexpensive way to do it (pennies).

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