Quote:
Originally Posted by AAngel
I've seen quite a few posts lately by newer guys asking questions about motor and battery choices. They are asking a lot of pertinent questions, but are passing over what has already been tried and proven.
I am far from being the resident pro on brushless conversions, but I have built about 8 of them so far, and have learned a few things from others and through trial and error.
I don't think that anyone would disagree with me when I say that there is sort of a formula for a successful truck conversion. 30,000 rpms is a good target to aim for with your motor and battery combo. There are also other considerations to keep in mind, like weight. Adding voltage is usually a good thing, but not at the expense of adding significant weight to your vehicle. A monster truck that handles like a boat is no fun to drive.
A couple of combos that come to mind that make winning setups in trucks are:
1. a Neu 1515/1y on 14.8v works very well and stays cool
2. a Neu 1515/2.5d on 14.8 or 18.5v also works very well and is very flexible
As for the A123 cells, I like them, but they do have their drawbacks. They are large and heavy and are limited in the amount of current that they can deliver in 1P configuration. I tried a pack of 5S1P A123 and although it ran OK, it really lacked the punch that I was hoping to get. For 5S, I think that a 2P configuration would really be needed. What I don't know is how much voltage you would have to run before the current demands are such that a 1P configuration would suffice.
You also have to keep in mind that the benefits of the added voltage will also diminish as more cells are added due to weight. The A123s weigh 70 grams each and are the size of a C cell battery.
If you just want to stick with A123s, I'd look into going with either a 5S2P or maybe even a 6S2P setup and get a motor that will get you around 30K rpms on your voltage.
Just keep in mind too that whatever voltage you do get, you'll need to charge it.
What I've said above is just my general opinion for off road trucks for extended running. Setups for specific purposes would probably deviate. I'm getting ready to start running a 1515/1.5d on 5S lipo for drag racing. Not very practical for off roading or extended running, but it's gonna haul butt.
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AAngel, couldn't agree more, it takes too much time and too much money to reinvent the wheel :-) :-) I guess I could have simply expanded on Serums details from the "Brushless General" notes from the top of the forum and been at a decent starting point.
I've always liked, not loved, my Maxxs running HVs and stepped into an initial Savage running an 8XL on 14.8v but it got so blasted hot that I wanted to flip to something lighter and more "controllable" when it came to temps and cooling off. Running my Revo also on the 8XL with a Quark has proven to be lots of fun, but I miss my Savage :-( Not seeing tons of info in the Savage forum and having it weigh CONSIDERABLY more than my Revo, I "lost my way" in planning.
That said, I should have been more clear on my A123 situation, lol, all my packs will be XS2P (X being number of cells) realizing that they pull down about 60\70 amps in 1P config scared me when I started looking at the weight of my Savage and the Savage lends itself nicely to dual packs, one on each side and also allows you to tend them to the front of rear for weight transfer if need be, which I like. My Revo ran all 12 cells down one side, which didn't bother me greatly, but it did make for one large pack vs the weight and balance of the motor, esc and electronics on the other side, lol...
For charging I'll be hitting these with the TC1010 from Thunder Power, I LOVE the charger and it has always treated me good in return :-) Question though, the 2.5d on 14.8 seems a bit "low" for RPM vs the weight of a larger MT? Pushing it to 18.5 takes it right to the sweet spot, but I was always under the impression and I know we're splitting hairs here, that you wanted to see about 35k rpm out of the motor and with the Neus maybe just a hair more?
Hum, considering your thoughts, and my trucks weight, maybe the "perfect" setup for my Savage would be:
Dual 6S1P A123s
Neu 1515 2.5d - 37k (ish) @ peak charge
MGM 16018
My only concern again is weight; believe me I've even thought of dropping to a 1500 kv motor or going to a 1521 and taking the cell count up and going with the 16024... Ohhhh what to do, lol
What I want is a truck that runs well, stays cool and doesn't handle like a boat
GREATLY appreciate everyones input, if I didn't have total faith in you guys I wouldn't have asked.
Thanks again,
purp