Quote:
Originally Posted by lincpimp
Ok, I understand we are talking about braking. It was my understanding that the voltage spikes that are produced during braking need to be absorbed by the battery. A battery with a high IR will not be able to absorb the voltage spikes as well, and that can lead to damage to the TVS and eventually cause the MMM to fail. I do agree that CC need to spec specific brand batteries, as that will likely be the only true cure. But the customer needs to be informend, and I always see that as the responsibility of the customer. If you do research before you buy something no one calls out the mfg for that... This is a hobby, and it is generally understood that if you want to participate you need some sort of intelligence. So expecting everything to be written down might be a bit much.
I cannot believe the heat issues that would be had using nimhs with the stock gearing on a flux, but they still say it can be done... Not the best idea if you ask me...
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Well I see it a little different I guess. I see it as the manufacturer you have to make your device idiot proof. I know what you are going to say "The world will always make a better idiot", but with that in mind. Castle should have known there are several brands out there that are not up to the task and explained how the system worked in brake mode and that if the batteries of poor quality then it could damage the ESC. There is no mention of that in the docs I have.
To me there should be a clipper circuit or something else to handle the spike created during this time, and have it built into the system, sure it adds weight and size, but do you want your system to have a bad rap? It matters not if this is a hobby, the manufacturer needs to make an effort to educate the masses buying their product. And they do but on this board not their website or documentation
Besides I have been researching the larger ESC's for some time now, since before the MMM came out. I called Castle and asked a bunch of questions but was never given a direct answer for current handling until recently by Patrick himself on this board.
You shouldn't have to search for a forum to find the answers you are looking for you should be able to get it straight from the manufacturer. The book is (was, haven't downloaded a new manual) seriously lacking on the technical side, and for something this technical it needs more meat, period. Having everything written down a little much? Well ok some things you have to save for yourself, but if batteries were this big of an issue it should have been in bold print on the front page of the pamphlet.
As far as having some intelligence, just look at my sig that I got from a milling machine we bought (condensed for space constraints). It’s all relative, if I would have just bought a MMM I would have set down and read the instructions (just like I did with my MM) and been off. Who is going to know about back EMF except someone who has an electronic background? This isn’t something that is commonsense. It is a flaw IMO.
Case in point, as I am sure you have read at least once we manufacture a small conveyor (among other things). It uses a stepper motor with integrated encoder and amplifier (read ESC), it also has digital and serial I/O. Basically we send it a position command (infinite in our case), Speed and Acceleration. Over the years we have had a few come back with the board damaged. About a year ago the manufacturer made a board revision that put a fuse in line with incoming power. On the output of the fuse is a Zener diode so if the voltage rises above a certain point it conducts and blows the fuse (there is also a TVS in there as well). Well I got in 4 units that had the fuse blown and the Zener shorted. On 3 of them I was able to replace the SMT fuse and everything was OK. The fourth though had a FET shorted as well. After speaking with their tech support I was told that a brand new motor only 17 days old (including shipping from Canada 2 Houston then to Ohio) would not be covered since the Zener was bad as well. I asked him why and what would cause this, he told me it happens during Regen. Basically the conveyor has solid SST rollers weighing about 12 pounds. We have a maximum Accel/Decel rate of 25 rps/s, which is quite slow. But if the conveyor gets jammed and then let go, it will speed up over our maximum speed and try to “catch up” with the position it’s supposed to be in. So basically it runs real fast then wham almost comes to a stop as it gets to position. As you can already tell the amount of force required to stop 12 pounds of weight almost instantly creates a large overvoltage and can take out the FET’s before the fuse can even react (besides fuses are S L O W, even fast acting ones). I asked what the fix was (besides their new motor we are working on the algorithm for), and was told I should need a “slave board” that has this protection built in. We never needed it in the past, since we run at a constant rate it hasn’t been an issue and we have used this motor for nearly 6 years. And you know what it’s in their book. The motor that we use is more suited for pick and place than the application we have it in now (we need something a little dumber).
Jeff