RCCrawler Forums

Mayze · 05-20-2009, 04:58 PM

Am I going to have any issues running a brushless setup on 7 or 8 cell nimh packs? Can't afford to make the switch to lipo...like I should've gone with in the first place

. Thanks

Duuuuuuuude · 05-20-2009, 05:00 PM

Not at all...unless they are crappy packs. Still, if you are just crawling, you'll be fine.

I went brushless before I went lipo, didn't have a problem.

Mayze · 05-20-2009, 05:03 PM

Great to know. Thanks.

vavaroutsos · 05-21-2009, 12:06 AM

Brushless motors are more efficient. You will probably pick up some wheel speed with the switch to brushless.

~petev

CreepyCrawl · 05-21-2009, 09:46 PM

Many people are under the assumption that if you run a brushless set up, you have to power it with Lipo...I hear this all the time at my local shop.

Brushless motors will provide some additional run time due to their efficiency, and they can be more powerful by comparison to their brushed counterparts, regardless of battery choice.

If you apply the voltage, you're going to have more power...simple as that. 2 cell Lipo is impressive...3 cell is insane with the right kv choice, but don't discount 7, 8 or even 9 cell NiMH...voltage is voltage no matter what type of cells they are.

For crawling applications though, I'm still a firm believer that a nice quaity brushed motor will always out perform a brushless set up.

Duuuuuuuude · 05-21-2009, 10:36 PM

Quote:

Originally Posted by CreepyCrawl

Many people are under the assumption that if you run a brushless set up, you have to power it with Lipo...I hear this all the time at my local shop.

Brushless motors will provide some additional run time due to their efficiency, and they can be more powerful by comparison to their brushed counterparts, regardless of battery choice.

If you apply the voltage, you're going to have more power...simple as that. 2 cell Lipo is impressive...3 cell is insane with the right kv choice, but don't discount 7, 8 or even 9 cell NiMH...voltage is voltage no matter what type of cells they are.

For crawling applications though, I'm still a firm believer that a nice quaity brushed motor will always out perform a brushless set up.

Yup, I run 7 cells and a VXL motor in my Slash. Plenty fast and will still pull wheelies at speed. On a 3s its nearly undrivable.

GSRswapandslow · 05-21-2009, 10:54 PM

haha...i was just about to say..i have an 8cell 5000mah pack for my vxl slash............and i can't imagine what the 8000mah 3s is gonna be like

Duuuuuuuude · 05-21-2009, 11:09 PM

Quote:

Originally Posted by GSRswapandslow

............and i can't imagine what the 8000mah 3s is gonna be like

Its going to be stupid.

I tried a 3s, and decided to stick with 7 cell nimh's. That kind of power is good for showing off, but hard to put down when you really want to.

Mayze · 05-22-2009, 03:39 AM

Isn't there an advantage to the lipo as far as run times, and efficiency/consistency of power delivery? Correct me if I'm wrong, but it seems that an 8 cell Nimh is about the same as a 3s lipo?

Duuuuuuuude · 05-22-2009, 07:14 AM

Quote:

Originally Posted by Mayze

Isn't there an advantage to the lipo as far as run times, and efficiency/consistency of power delivery? Correct me if I'm wrong, but it seems that an 8 cell Nimh is about the same as a 3s lipo?

Lipo power delivery is greater, as well as run time (more efficient delivery, less loss to heat/resistance). Lipo also weighs less comparitively.

CreepyCrawl · 05-24-2009, 08:10 PM

Picture the discharge rate of NiMH and Lipo cells side by side on a graph...

The NiMH cells start to dump (drop curve on the graph) as soon as any draw is put on them.

Lipo cells maintain a more consistant discharge cycle (straight line on the graph) and dump later, so you have much smoother and more efficient power delivery.

Equvilancy depends on charge rates and battery quality, as battery voltages are specified by the actual "dead" voltage of each cell. A 6 cell stick pack is 7.2 but we all know that it will peak out much higher.

A 3s Lipo is 11.1 volts (3.7 per cell) whereas an 8 cell NiMH is 9.6 volts (1.2 per cell) so the closest un-peaked NiMH equivilant to a 3s Lipo would be a 9 cell (10.8 volts)

Lipo should be charged at a 1C rate (1x the mAH) and most chargers will only peak the voltage to a safe level. Example: A 2s (7.2 volt) pack will peak out at 8.4 volts. There are chargers that can be adjusted to higher rates, but caution must be taken...nasty things can happen to an over amped Lipo.

NiMH can be charged at higher amp rates within reason, so more voltage can be gained, but this can also diminish run time, as well as cell life.

All in all they both work, and it really boils down to personal preference as much as the actual numbers.

05-20-2009, 04:58 PM	#1
Mayze Quarry Creeper Join Date: Jan 2009 Location: Langley, BC, Canada Posts: 297	Brushless on Nimh Am I going to have any issues running a brushless setup on 7 or 8 cell nimh packs? Can't afford to make the switch to lipo...like I should've gone with in the first place. Thanks

05-20-2009, 05:00 PM	#2
Duuuuuuuude Suck it up! Join Date: Mar 2008 Location: Arkansas Posts: 11,652	Not at all...unless they are crappy packs. Still, if you are just crawling, you'll be fine. I went brushless before I went lipo, didn't have a problem.

05-20-2009, 05:03 PM	#3
Mayze Quarry Creeper Join Date: Jan 2009 Location: Langley, BC, Canada Posts: 297	Great to know. Thanks.

05-21-2009, 12:06 AM	#4
vavaroutsos Rock Stacker Join Date: Apr 2009 Location: San Jose Posts: 59	Brushless motors are more efficient. You will probably pick up some wheel speed with the switch to brushless. ~petev

05-21-2009, 09:46 PM	#5
CreepyCrawl I wanna be Dave Join Date: Oct 2006 Location: Centered Posts: 2,082	Many people are under the assumption that if you run a brushless set up, you have to power it with Lipo...I hear this all the time at my local shop. Brushless motors will provide some additional run time due to their efficiency, and they can be more powerful by comparison to their brushed counterparts, regardless of battery choice. If you apply the voltage, you're going to have more power...simple as that. 2 cell Lipo is impressive...3 cell is insane with the right kv choice, but don't discount 7, 8 or even 9 cell NiMH...voltage is voltage no matter what type of cells they are. For crawling applications though, I'm still a firm believer that a nice quaity brushed motor will always out perform a brushless set up.

05-21-2009, 10:54 PM	#7
GSRswapandslow Quarry Creeper Join Date: May 2006 Location: Taylorsville Posts: 348	haha...i was just about to say..i have an 8cell 5000mah pack for my vxl slash............and i can't imagine what the 8000mah 3s is gonna be like

05-22-2009, 03:39 AM	#9
Mayze Quarry Creeper Join Date: Jan 2009 Location: Langley, BC, Canada Posts: 297	Isn't there an advantage to the lipo as far as run times, and efficiency/consistency of power delivery? Correct me if I'm wrong, but it seems that an 8 cell Nimh is about the same as a 3s lipo?

05-24-2009, 08:10 PM	#11
CreepyCrawl I wanna be Dave Join Date: Oct 2006 Location: Centered Posts: 2,082	Picture the discharge rate of NiMH and Lipo cells side by side on a graph... The NiMH cells start to dump (drop curve on the graph) as soon as any draw is put on them. Lipo cells maintain a more consistant discharge cycle (straight line on the graph) and dump later, so you have much smoother and more efficient power delivery. Equvilancy depends on charge rates and battery quality, as battery voltages are specified by the actual "dead" voltage of each cell. A 6 cell stick pack is 7.2 but we all know that it will peak out much higher. A 3s Lipo is 11.1 volts (3.7 per cell) whereas an 8 cell NiMH is 9.6 volts (1.2 per cell) so the closest un-peaked NiMH equivilant to a 3s Lipo would be a 9 cell (10.8 volts) Lipo should be charged at a 1C rate (1x the mAH) and most chargers will only peak the voltage to a safe level. Example: A 2s (7.2 volt) pack will peak out at 8.4 volts. There are chargers that can be adjusted to higher rates, but caution must be taken...nasty things can happen to an over amped Lipo. NiMH can be charged at higher amp rates within reason, so more voltage can be gained, but this can also diminish run time, as well as cell life. All in all they both work, and it really boils down to personal preference as much as the actual numbers.

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