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1/8 battery recommendation

1/8 battery recommendation

Old 11-01-2012, 06:01 AM
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Default 1/8 battery recommendation

Thinking of getting back into the hobby (w/ my 12yo son) after 22 years being away from RC Racing.

We are looking at the ebuggy class racing

For my son I was thinking of using a 1400kv motor.

What would be the best battery set up for that 1400kv motor with a novice at the controls?

also

Can a person get by with just one battery?

As you can tell, I know very little about these new lipo batteries,

Thanks!
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Old 11-07-2012, 06:55 AM
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Does anybody run 5s with a lower kv motor?
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Old 11-07-2012, 08:52 AM
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4s is all u need. I'd get at least a 30-40c battery
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Old 11-07-2012, 09:58 AM
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Originally Posted by Tran901 View Post
4s is all u need. I'd get at least a 30-40c battery
For racing more the better. 60C if you can swing it, depending on the manufacturer it can be only a few dollars more, in which case I find it to have value.

Check with the local club, some places have it at 4S max (and for the track, this is often all you need). The 1900-2000 neighboorhood on 4S is very quick with a lot of snot too.

For racing, I think you will want two batteries a piece, but you could possibly get away with one depending on your track if you charge asap when you get off the track. With the Team Associated's rtr modest electronics (plus my own servo) I get about 30 minutes of track time on a 5200mAh battery (it is tigher than most 1/8 scale tracks). How many heats and qualifiers do they run before the main? Are there a lot of classes?

I have a second battery that I use for the main because we are a smaller group and there isn't a whole lot of time to charge in between. Charging time also depends on charger and power supply you use to charge while at the track.
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Old 11-07-2012, 11:06 AM
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Thanks Devin... After a 5 min heat race, Would the lipo batteries need to cool before you recharge?
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Old 11-07-2012, 02:33 PM
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For 8th scale eBuggy, here's a few things for your average eBuggy race setup.
1900-2050 kv motor (such as the Tekin T8)
4S (most common and required for roar races)
Servo that puts out at least 250 for torque (more is better, especially if you tend to land with just 1 wheel down as air control is being developed)

As for how you can mess with this a bit.
A 1400-1500kv motor on 4s would be slower, which might be good for a novice that has trouble directing the car, but it should also come off just barely warm and allow for continual running without any issue. Should you just be club racing, bumping to a 5s pack could make this motor then perform about like the others...however unless you already have a 5s pack, a new motor is probably about the same a decent 5s pack.

For a 1900kv on 4s, the pack should be in the 40+ range for C rating at about 5000mah. If you go down in capacity (lower mah), then you will want a slightly higher C rating in order to pull the same burst current out of the pack. 2 very reasonable budget 4S packs are the Gens Ace (hobbypartz.com) 5000/40c and the GForce (valluehobbies.com) 5200/60c, both coming in the $60-70 range most of the time.

As for the 1 battery thing. You can easily do it, especially with something like a 5000+ mah pack, when you're only doing 5 minute races. Even if you don't have a high output charger that can charge at the full 5 amps on 4s (most are 50 watt output and top out at about 3 amps when charging 4s), you'll still be able to alternate which battery of yours or his you top up a bit. For most eBuggy's, a 5000mah pack on 4s will get you a good 15+ minutes of runtime, with the first 10 min or so being about the same performance. In case you end up in practice days, or heats coming more quickly, I'd at least get 1 more battery that can be charging while you're both running, or ideally have 2 batteries each and a charger port for each of you. In general, the pack may be a tiny bit warm, but should never heat up a lot, as eBuggy tends to use throttle in short bursts, rather than sustaining high load. If it is hot when it comes off, let it sit before charging it, but it generally should be fine to just start charging within a minute or so of coming off the track.

Also note: With reasonable gearing, a 1900 kv motor on 4s in most buggies will also be able to run at a sustained temp and just keep going pack after pack, though it'll run warm and need decent cooling to do so. I do this with my Tekin T8 1900kv in my Tekno EB48 eBuggy and come off around 140 on the motor after a couple packs, 150 on a warm day.
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Old 11-07-2012, 02:51 PM
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justpoet..Thanks for taking the time...and... thanks for the informative post,

That helps alot
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Old 11-07-2012, 02:56 PM
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One more question...

Will a power supply rated at 12-15 volts dc & 35amps be enough to run a dual dc charger, charging 2 ea. 4s lipo's simultaneously ??
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Old 11-07-2012, 03:13 PM
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All we need to do is compare wattage of the output and desired charge rates.
Volts * Amps = Watts

15v * 35a = 525w max output or 420w max output at 12v

There will be some loss in the charger, but for the moment let's skip that step and jump to actual charge requirement.

Assuming 5amp (5000 mah pack and 1C charge rating), * 4s voltage (16.8) = 84 watt (per pack)

So, 170w will roughly cover the charging, and bumping to 200w should likely cover charger overhead, leaving plenty leftover for pit lights, another charger, etc.


On a completely different side note, that capacity will take aprox 40-45 minutes to fully balance charge at 1C (if run close to cut off). Most will say balance charge every other or every 10th charge, but with multiple cell packs it is more important, so worth just always balance charging, even though it takes a very slight bit longer to charge that way.
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