Thread: Team Death - New Heavyweight

Another Sunday has past us by, which means another update!

It's been a day of ups and downs, however we learnt from the experience - and that is what counts!

Before I arrived, Colin had setup the wiring ready for a test. So before we went anywhere specific to test, we plugged everything up, at this point only the batteries were needed, and ran an off-ground test just to ensure nothing silly would happen. It wouldn't try running away when the link was plugged in, unfortunately this did lead to one problem being spotted immediately. The motors had been wired in correctly, leaving one going forward whilst the other reversed. This is due to a simple forgetful mistake, in that in the past the motors were mislabelled red/black, however that was accounted for at some point in the past and fixed - but had forgot we did that so the motor was purposefully wired wrong under the assumption that was to do still.
Not to worry, the Cytron ESC is very quick to do a rewire and it was fixed within a few minutes.
Another issue shot up when we got it on the floor, now we were happy it'd maneouvre as anticipated motor wise.
The castors springs needed a little adjustment, as it ran one side of the bot tended to be on the ground a little firmer than the other, causing some one sided wheelspin. So a little tinkering was made there, to balance out the weight distribution a bit more.

After this, it was time to do a proper test for the first time, we packed up the bot and some tools, and headed for a secluded section of tarmaced area near the workshop. After noting the batteries at this point where about 60-70% charged, and we managed to get a good few minutes of usage out of it. Certainly more than the typical battle would last. We found out quite quickly that control was a little sketchy - unless you had perfectly positioned the controllers stick, there was a noticeable difference in output in the two motors, and driving was a little harder than we'd like. There was also a few further issues with the weight distribution, we'll try to see if we can correct this with more tweaking to the springs as we were still wheel spinning a bit on one side more than the other, although this may be related to the control issue. After a while, unfortunately but obviously, the batteries became a little drained to keep things moving along at a pace of value. We went to check up the bot - the batteries were both very warm, overly so. thinking nothing of it, we tried to have one last run straight line run to gather some speed up, however it just sat and didn't move. So we packed up and headed back to the shop.
Upon arrival, we decided to try to get around some control issues, by setting up a 'tank' style driving. Lifting the bots wheels off the floor, the batteries still had enough power to run the wheels, so we could test this new control method, and it seems to work. However, that is indeed all she wrote. With the batteries at this point being unable to spin the wheels, even off the ground.

We got out the charger, and set to work charging the now drained batteries for a later date. However, it's at this point we unfortunately found out that one of the batteries had been killed, my best guess is by the heat. It was so broken that the charger wasn't even able to detect it was a four cell battery, and only gave a total voltage (of 5 volts, on a 14.8v nominal LiPo!) and was unable to display individual cell data. We double checked and connected up to the other battery, and sure enough this one was seemingly in working order, with the charger correctly giving data for all four of the individual cells, and happily charging upwards. Whereas on the other, the charger just flat out refused to charge it due to a voltage discrepency.

I am thinking that the current battery holders are simply not getting any airflow, allowing the heat generated during discharge of the batteries to build up to damaging levels. I've included a picture of our battery holders below, so if anyone has an idea about this, and can confirm my suspicions, i'd be grateful. As if it wasn't damaged due to the heat, it may be a more severe problem than originally thought with the wiring or some other electrical part of the bot. We have a few ideas for alternative battery holders with much more airflow potential up our sleeves, if the heat and no airflow is the problem.

So all in all, today was certainly interesting. But we learnt from the experience, made some fixes already, the rest we will tackle on further sundays, here we don't hide the stumbling blocks. We share the entire experience for sure!

Some images, and some video taken during the test run. We managed to get up some good speed in parts, and we also know it spins well, so that's something.

I've cut down the video so the first minute is the most relevant to capabilities, and after that its mostly farcical stuff and spinning. Whether out of control, or intended - i don't know! It does however look like it spins with enough force to be somewhat damaging just from that!


All wired up and ready to go
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All packed up for its first time leaving the workshop - note that we decided to put the lid on top of the ESC box for this drive out, incase things got a little bumpy as the ESC is loose in the box currently although the sides and bottom of the case inside have been isolated with non conductive tape, just incase. We took a brush and a shovel so we could clear debris from the area, to help traction and make sure we didn't run into anything too nasty.
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These are the battery compartments. I suspect these are the cause of the overheating and battery failures, as there's very little airflow, especially to cool down the cells in the centre of the pack. Especially as the battery is 45C at 4500mAh so should be capable of over 200A sustained flow, and we shouldn't be touching even 100 of that.
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The first battle damage! - It was also running on the bar on top, based upon the scratch marks. So we're not sure if it was just bouncing upon it occasionally, or actually dragging it across the floor all the time.
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