hi,
I think I'm gonna buy a dagu wild thumper chassis or make something like one... but I was thinking...
the motors are 6.6A max each, there are 6 of it, so you gotta be prepared for 39.6A max just for the motors... and I think I'm gonna do my own H bridge from mosfets... but whatever... I was looking for battery options. I searched on hobby king for lipo batteries, and I found that the 5000 maH are one of the bests, also are like $17 or something, but I just calculated here:
so if they are 5000maH they can do 5 A for 1 hour, so if I use 39.6A + 1 A for the rest of circuitry (basic stuff) it goes 40.6A
40.6/5 = 8.12 -> 60/8.12 = 7.38 minutes
is my math right? I mean, if I buy one of the most powerful lipo batteries available in hobbyking.com, I'll be able to run the robot for about 8 minutes? that's a problem :S
so what I want to know is what you guys found out to be the best options for batteries in cost/benefits... like I heard that NI-MH batteries get bad over time, so is that true that I should avoid them because of this or anything else?
there are chinese selling this NI-MH batteries in packs of 8 or 16 with a charger for $16 or so... they are rated for 2500 mAH, I could put 6 together and get a 7.2V, so I put 2 or 3 of this packs and get like 7.5maH... is that an efficient method? is there anything in all this that I did not think about (like the stall current is 6.6A but most of times they get 2A or so?)
well, I placed this in "Absolute beginners" because it is exactly what I am =)
so I don't know the best robot contruction options available (for batteries, chargers, motors, drivers, etc) so I'm trying to figure out this informations from the guys who know about it... so if I made some "noob question", it's because I'm a noob =)
I appreciate any advice you guys can give me about robot prototyping/construction (let's say that making my own driver out of mosfets is very very bad, and I don't know it... so you guys could tell me the best option) =)
edit: I forgot to ask it... this is just a curious question I had, and I need to ask it to odbot.
So, you the one who designed this chassis, which is one of the best that I have ever seen on the internet (congratulations... I'm your fan :P)... but I think there are some 12v motors with big torque as well that do not go more than 2A stall current... so why you choosed this motors that are 7.2V and go 6.6A? I mean, it is like no battery is gonna run a lot with them, surelly I could buy like 4 packs of lipo or something and have it for a lot of time, but you know, it's still 4 packs of lipos :S... the motors I mentioned do not have a big RPM, they go normally like 60 or 100 rpm max... so the dagu wild thumper is a lot faster than it as it is 350 rpm for the 34:1 gear ration motors version. So was that one of the points?
I'm just curious about it, this is not offensive(my english is not that good, and I don't know when I may be offensive when righting) or something like that... it's just curiosity =)