Savage project idea. Please read have many ?'s!

[BL_RV0]

I've decided that I am going to build a Savage on (sort of) a budget, and decided that I would like to try A123 cells in this setup. It will be HV, don't you worry. .... So, my setup idea is a Mega 22/45/2 if I decide to be on a budget, or a 22/50/2 if I wanna spend a lot, or if I decide to go completely all-out, a Lehner 1950/10. Here would be the a123 cell counts.
22/45/2: 33v, 10s A123
22/50/2: 39.6v, 12s A123
1950/10: 33v, 10s A123
for the Mega motors, the controller would be a CC HV85, and for the Lehner it would be a CC HV110. here is some gearing ideas based on those voltages:
22/45/2: 13/49
22/50/2: 12/49
1950/10: 14/49
the gearing choices are based on a 3 speed transmission, the stock Savage X SS kit spur gear, and 7 inch tall tires (Losi claw. (stock tires on the LST1.))
Now, about the batteries. I found these:
http://www.hobbycity.com/hobbycity/s...idProduct=6444
And were wondering if they're any good. I also found these:
http://www.hobbycity.com/hobbycity/s...idProduct=5632
Are those any good? Which of the two I linked would give better performance? Do you build them just like you do a NI-MH pack? If I use one of those two cells, is my Hyperion EOS1210i capable of charging a 10s or 12s pack? Or would I need to build 2 packs and run them in series? Do you need to balance the packs?
As you can see, I have very many questions about A123. If there is a different cell that I should look at please let me know, thank you for reading this, and thanks for your help in advance!

[lutach]

I would choose the Mega 22/50. They have support here in the USA. What about a NEU? The price of the 1521 is pretty good now.

[BL_RV0]

The Neu 1521's seem to have length issues with the FLM conversion, and the 1515 doesn't seem to be powerful enough.

[lutach]

The Neu 1521 is 3.3" long (84mm) and the Mega 22/50 is 3.2" long (82mm) and if the 1521 doesn't fit, I think the 22/50 won't fit as well. I think the 22/45 will do the job well, the same length as the Neu 1515, but the 22/45 is cheaper.

[BL_RV0]

Will the 22/45 be enough?

[jzemaxx]

A 1515 is more then enough. If you have never tried the Neu's, try them. The 4 pole motors make a big difference on the level of torque they make. A 1515 with pleny of voltage will easily power a savage to crazy speeds and do it nice and cool. We have a MGT 4.6 converted to 8XL and 5S that is running 61mph...and that is a crap motor compared to the 1515.

[othello]

A123 would give you better performance and are cheaper to get if you salvage a DC9360 Dewalt pack. Pack building isn't that hard. I built 6pcs of 5 cell packs due to balance issues in my truggy from 3 dewalt packs. I charge 10s1p in series on a hyperion 1210i. Charging time is about 30-35 min due to it's 180Watt power limit. It is also able to recharge 12s A123 (which is the limit). With 10s1p you can expect about 2.5Kw bursts which is more than a 11lbs truggy can handle without wheeling (i do calculate with 250W burst per A123 cell. Peaks of 100-120A is about the limit i recorded with my eagletree). I use a Neu 1515/2Y (1100KV). It sure has more than enough power, to handle a heavier savage, which you would often see converted with a Feigao XL, which normally should be less powerfull due to higher inefficiencies.

Latest video of my truggy with 10s1p A123 and Neu 1515. This is with a center Diff. I guess the 3 speed transmission of a savage has no center Diff. So expect more wheelies depending on gearing.

Edit: Adding balancing wires is not absolutely necessary. My oldest packs are still within balance after 80 cicles(without balancing). I made sure that all cells were fully charged before i built the packs. Checking voltage from time with a voltmeter is all i do from time to time. The easiest way to see if your cells are in balance is when you drive and power suddenly falls within seconds.

[BL_RV0]

Thank you guys for the info. Othello, would you mind taking a picture of your packs you built? Thanks!

[othello]

I found some pictures of my A123 battery packs placed in my truggy and buggy. As i'm at my girlfriends place i can not shoot some pics of those packs themselves.

pic1, pic2, pic3, pic4

For more runtime you may look into a 12s setup. But 10s is convenient as a dewalt pack holds exactly 10 cells. When driving like in my previously posted video runtime goes down to 7-8 minutes with 10s1p A123. When drving more reasonably with not as much high speed passes and less grip i got up to 12 minutes out of my packs. It really depends on a lot of factors (gearing, vehicle wheight, driving style, surface ...). In my lighter buggy (9lbs) i could drive for up to 13 minutes when pushing it hard. So wheight has a lot of influence on how long you will drive.

You might have seen this picture of legobrains FLM Savage which exactly represents how you will get your A123 cells when they are salvaged from a dewalt pack. Don't know if they will fit this easely in your savage. You only would need to solder two cables and shrinkwrap it. I wish it could be as easy for me to build my packs.

By splitting your packs in 2 5s packs or 2 6s packs you would be able to recharge 2 packs in 15 minutes when using a hyperion EOS0610iDUO Balance Charger. It also has 2 integrated balancers. A choice you might consider.

[BL_RV0]

Thanks for the links, Othello. What are the dimensions of a A123 cell?

[othello]

26mm (1.024in) diameter and 65mm (2.559in) length with a wheight of 71gr (0.157lbs/2.50445oz) per cell.

[BL_RV0]

Thanks again, Othello. I had a new idea- a Mega 22/45/3 on 12s A123 with 15/49 gearing. The /3 is 1000kv versus the 1380kv of the /2 wind. One problem though- the /3 wind only pulls 35a maximum versus the /2's pull of 60a maximum. Would this result in less torque? Should I stick with the 22/45/2 and 12s and gear down, since you say that the extra 2s make a large difference in runtime?

[lutach]

Originally Posted by BL_RV0

Thanks again, Othello. I had a new idea- a Mega 22/45/3 on 12s A123 with 15/49 gearing. The /3 is 1000kv versus the 1380kv of the /2 wind. One problem though- the /3 wind only pulls 35a maximum versus the /2's pull of 60a maximum. Would this result in less torque? Should I stick with the 22/45/2 and 12s and gear down, since you say that the extra 2s make a large difference in runtime?

The AMP rating of the Mega are based on continuous (Very conservative) use. It will handle short bursts just like any other motor.

[BL_RV0]

Ok. How does the idea of a 22/45/2, CC HV85, 10s a123, 13/49 gearing, and a 3 speed transmission sound? Also, any guesses how much this thing will weigh?

[othello]

Both motors are able to generate the same amount of torque, but the motor with more winds (ACn22/45/3) will need less Amps to generate the same amount of torque as a ACn22/45/2. Theoratically 1000 vs 1380kv = 38% less Amps. Meaning a ACn22/45/3 drawing 30A at a given voltage would require your ACn22/45/2 to draw 41,4A to generate the same amount of torque. This is how i understood it.

The ACn22/45/2 with 1380kv would be a relative hot motor on 10s1p A123. Under load at full speed voltage of 10s1p A123 will drop to 28-30V. Giving you rpms of around 40000rpm. Seems a bit high for my liking in a heavy truck. I used a Neu 1512/2Y (1400kv) in my 9lbs buggy and saw rpm levels of up to 44000rpm (with 10s1p A123). Which seems alright for a lighter buggy. The same motor in my heavier truggy (11lbs) with the 10s1p A123 reached 36000-38000rpm under load geared for slightly lesser speed than in my buggy.

It really depends on which rpm band suits your gearing options most. Expect 38000rpm with a ACn22/45/2 (1400kv) under load (depending on your gearing) with 10s1p a123, The ACn22/45/3 (1000kv) will more likely be at 28000-30000rpm with 10s1p a123 or 33500-36000 with 12s1p A123.

With 12s A123 you will have 20% more energy in your car. Due to having more wheight in your car this won't translate into 20% more runtime. But having more volts tranlates in lesser Amps to generate the same amount of power. Giving you slightly more efficiency. You might end up driving 10-15% longer with 12s. This is only a guess. I saw a jump in runtime of around 1 minute when driving with 10s1p A123 in comparision to a 9s1p setup.

What you also might consider is running an ESC at its voltage limit is always more risky then using it with a safety margin of 1-2 cells less then its rated max. So look at the specs of the HV85 or HV110 -> 8s lipo is comparable with 10s A123 from a voltage point of view. When coming fresh of a charger a123 cells are at 3.6-3.7v per cell. Droping quickly to 3,3v when used. What you also might consider is flight ESCs have a slower ramp up time when revving your motor up. Investigate on this further or you might end up with a setup which feels a little sluggish when it comes to accelerating.

On a side note the ACn22/45 series is a little heavier than a Neu 1512. Which i would consider beeing on the light side for a heavy truck. The 1512 worked well in my truggy but run hotter then my Neu 1515. More mass means more energy in heat can be stored. That is why a heavier motor is not as critical then a lighter motor. The ACn22/45 will have enough power to push your truck but i would expect it to run a little hot due to it's "small" wheight. If you're not a speed freak this will not be an issue. A heavier motor can be geared higher without breaking a sweat. But those are all estimations. Don't know if someone already tested this motor in a heavy truck.

hope this helps.

EDIT: like lutach stated. Those are continouus ratings. My average amp draw is between 15-21A when looking at a complete run. My Neu 1515/2y is rated at 50A if i'm not mistaken. I reguraly see peaks between 50-100A. But they only last for 1/10 tenth of a second under hard acceleration.