It's that day again! It's sunday, which means when I got home, there was a load of takeaway menus waiting for me in the post box.
Oh right, the bot, yes!
Today was a day of success, after a few recent tests being let downs. It wasn't without a few issues, which will be revealed later on. However, it was by far the most successful test we've had for a while.
Today, we started by charging both of the batteries up to 16.5v. Whilst that was happening, Colin did a little show & tell and demonstration of the strength of some metals, and how large but compact a Gazebo can be - this is actually not for anything to do with this new machine, but it was a bit of an idea fest for the Northern / Scotland events I'm trying to get up and running. This only took 15-20 minutes, and as we have figured out the safe limits our batteries can charge up to, it's all it took to get the batteries, both of them, up to the charge we were looking for.
Soon enough, the batteries were ready to go, and we put everything in the truck and to the usual test area. Quickly putting up a few boundaries to stop us from going in some very unpleasant pools of disgusting looking stuff.
Battery wise, there were still some concerns however. To begin with, the batteries depleted at even rates. However towards the end, one battery started tailing off a lot quicker than the other. Going from 16.5v each, to one being 13.2v, and the other 14.5v - up until the 15v mark, they were near enough depleting at an equal rate - with us frequently pausing to test the voltage and heat. When we got home, it was discovered that one of the cells in the 13.2v had become quite unbalanced with the rest, whereas the 14.5v battery was still all within 0.02vs of all other cells internally.
However, and - as pictured below, the lower 13.2v cell was quite a mixture. With the cells being 3.18, 3.30, 3.25 & 3.35. However, once charging had started, it only took a few minutes for the charger to balance everything back out before it charges them all up again, still in sync with each other.
This gives me and Colin some concern, as we are unsure as to why the cell are discharging at differing rates, and why the one discharging faster, is also becoming out of sync voltage wise with the independent cells. I therefore hypothesize this is the cause of the previous battery fault, where one discharged beyond its minimum without us noticing, and the other not doing so, resulting in a dead battery, and a bit of an unhappy hot one. It's worth noting here, that the new one is the one that ended up being the most discharged with uneven cell voltages, so it isn't the old one that is damaged here. So if you have any idea why this may be happening, i'd very greatly appreciate any feedback or suggestions. As the batteries were all charged to the same total voltage, and all cells were balance charged - so this all happened during discharge?
Colin notes that the drive is still a little off. Driving in a straight line is still quite hard to achieve. As hes been doing all the driving during the testing phase, I'll leave him to note down the specifics in a post soon after this, and hopefully someone can aid us in that area too.
Here is the video from todays test. Here we are able to demonstrate the speed it can attain when going straight(ish) - and how it manages to always get itself free from any debris its stuck over, including working its way out from awkward wedged positions. Furthermore, Team Death finally manages to beat a wall. Outdoing the infamous Piece de Resistance, now two decades ago.
Overall, the bot is certainly starting to behave in a manner we are aiming for, with a few little niggles - but we are definitely getting there, and the to do list after each test is getting fewer and fewer.
Note: you may wish to turn audio down - the wind was being unhelpful, and my phone has quite a high gain mic on it, so the wind is rather irritatingly loud.
and images
Note: on the cell voltage - the two last cells are non existant, as its a 4S battery, so we haven't lost two cells here! - here demonstrates that faster discharging batteries odd balance after the test (the other was higher overall voltage, and still balanced)
IMG_20180429_144102.jpg
Not content with knocking the wall down, we also managed to push the bricks some distance too. At some point, we may line up some bricks and see how much push we have on them - we also may try to pull or push something like a pallet.
IMG_20180429_141012.jpg
There is however, one downside to Colins modified wheels. The new treads seem to be ripping off slowly over time, this may or may not cause an issue later down the line.
IMG_20180429_150012.jpg
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Originally Posted by Ocracoke
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