Ok, I figured out the last problem; I had to bump up the voltage a tad. Now the issue has changed yet again The motor still makes the humming noise when it is put into the drive rig. Its that kind of stalling screech you get when you don't have enough power. I am thinking that bumping the voltage up again (to the max. of 12V) should do the trick. Does anyone have any other suggestions?
I dont think it should be screeching under any voltage. Did you drop some oil in the bushings? If not put some oil at the bushing on each end of the armature and try again. I thought motors can run at a lower voltage, it would just run faster with higher voltages.
I'll try that. I should also mention that it it often will turn fine one way but it seems to "catch" going the other way. However if I build up momentum going the first way then switch it, it carries over fine.
Hmmm, so the motors, they wouldn't happen to be 12V that you are running on less than 12v would they?
No, they are supposed to run anywhere between 3V and 12V according to allelectronics. http://www.allelectronics.com/make-a-store/item/DCM-229/3-12-VDC-MOTOR/-/1.html
Based on the symptoms given, it sure sounds like lack of voltage. Some of that could easily be the batteries not able to supply the amps those hungry monsters desire though. They would require SLA's (swagging for 5AH or above), or high discharge rated NiCD or NIMH's (qty 2 or 3 10C rated 3AH 7.2v packs in parallel). What batteries are being applied to these critters?
Right now they have 6 AA batteries, I'm bumping that up to 8 AA's. I was running one off a nine volt once and it ran so hot it melted the plastic connector. Hence the multi-battery packs
OK, that explains it. Are they NIMH or NiCD? AA's in any form are insufficient to drive these monsters for very long. Since you just said AA, I'm going to jump to a conclusion that they're std consumer akaline cells. Akaline cells are only decent for very low discharge applications (think pagers, remote controls and such). Interesting thing on akalines. The more current you draw, the internal resistance increases, this in turn causes more current draw, increasing internal resistance further, and voila. If you are going to use AA NIMH (which I don't recommend) you need to purchase 500TB's or similar that stall out at 1amp and only consumes a fraction of an amp under normal load. Cheers Jeff
Getting back to a couple of posts ago, please get a 6V Sealed Lead Acid with 5AH or more for your bench testing. It's cheaper in the long run, or even short run. They can be gotten typically for $10 or so, or you can get a 6v 12ah for shipboard usage can be had for around $19-$20. Cheers Jeff
That would be great, I'll go get one! I'm using rechargeable right now for testing, however my boat looks like it would need 20 AA's to run, so the packs sound great
Keep in mind, garden variety NIMH AA's are only capable of 0.5C discharge, so a 2000mah cell, can only reliably discharge 1000ma (1A). That should be enough to run the electronics/servos of the ship, but leaves no reserve to operate the motors. For a NIMH pack, here is a good one as an example for what is needed to handle high loads: http://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=1778 Cheers Jeff
"C?" What unit is that? Columb? I am now trying to decide if it is a better decision to switch the motors to something less power hungry, use "real" hobby batteries instead of rechargeable AA's or both. I am looking at batteries, any motor suggestions would be good.
I don't know for sure what unit a "C" is, but it is used as a proportional measure of a battery's charge/discharge capacity. A battery with a rating of 1C is capable of completely discharging itself in one hour. For example, a 1000mAh battery rated at 1C could discharge itself at 1000 mA for an hour, without damaging itself, and a 12 Ah battery rated at 1C could discharge itself at 12 A for an hour without damaging itself. However, if either of those batteries were to discharge faster than that, they would get damaged and not hold as much of a charge the next time you recharge them. A battery rated at 2C could completely discharge itself in half an hour, and a battery rated at 1/2C could completely discharge itself in two hours. Basically, to figure out the max current you can safely draw from the battery, drop the "h" from the "Ah" or "mAh" and multiply by the "C" rating.
C is the charge/discharge rating of the Battery versus it's capacity. A std consumer 2000mah AA is normally rated for .5C discharge, which would mean don't pull more than an amp sustained load on it without risking permanent degradation of the battery. Compare that to high discharge hobby packs for electric cars with a capacity between 3000-4500mah and rated at 10C, which means you can pull 30-45A off of them. Big difference. The SLA's are comfortably 10C (actually higher but I don't see that referenced much on the SLA's we get), which means you can easily pull 30A off of a 3.3AH SLA. The motors you are running have a high stall current as I recall.
So if I'm looking at batteries like these: http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=141 How do I find out what "C" value they have?
Try here Visit this site They have very good prices. Go for at least a subC cell. The smaller cells are really not rated to run motors. The blue 3800 mAh can handle 35 amps, the 4500 mAh red cells will do 42 amps. Both are 10C. Look down at the bottom of the page, they have a deal with 2 battery packs, with a charger.
The link you posted has a link of its own, upper-left, that says, "how To Choose Battery". It refers to: * Before order battery pack, you must pay attention on battery pack#65533;#65533;s Max. discharging rating on the specification or description. Please don#65533;#65533;t think any battery can take any current drain. & * The battery pack#65533;#65533;s Max. discharging rate of the chosen Battery must be higher than that device requires. It's a shame that their own product listings don't include information referred to in their "How To" page. I'd suggest looking elsewhere. JM
I'm on a bit of a budget, I'm liking this one: http://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=1695 What do you all think for my application? I also have no charger (might as well hold up large sign that says NEWBIE) so would something like this work? http://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=1351
