HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Feb 02, 2013, 11:56 AM
Registered User
Joined Feb 2006
30 Posts
Discussion
Can I use a 2s lipo instead of 7.2v Nicd?

I have lots of lipos and a good benchtop charger for my rc helis, and for simplicity I would like to use them on my new Redcat Volcano EPX (brushed motor).

Is that a bad idea? I am new to rc trucks, and I am surprised you guys even use nicd or nmhd batteries anymore. How come that is? Seems like lipo works as well or better for everything else. (except on a Boeing 787)

Is the charge / discharge times similar?
dma251 is offline Find More Posts by dma251
Reply With Quote
Sign up now
to remove ads between posts
Old Feb 02, 2013, 01:18 PM
Did you check the FAQ already?
SoloProFan's Avatar
The Netherlands
Joined Jul 2010
12,092 Posts
Lipo has some advantages over a 6 cell NiCad or NiMh, no doubt. You can draw more current from the pack while it holds a higher voltage, so acceleration and top speed are enhanced. Lipos are about 40% lighter for the same capacity, so you can drive longer. And you can charge some of these pretty fast, up to 5C, so that means your pack will be full in about 10 to 15 minutes.

But, there are also drawbacks that has some sticking to NiMh for now. Some like to keep an older car fully "vintage" so all equipment used to be from the era the car is from. Lipos also are a greater fire hazard than NiMh or NiCad, both while driving and when stored. You need special warning system to prevent discharging them too low, while on NiMh you can easily notice the pack is starting to dump, and stop before problems arise.

Besides, not everyone is willing to invest money into a lipo compatible charger, or needs the extra speed and power of lipos.

I for example do use lipos on some cars, but I also have a car with brushless system that already screams on NiMh, getting top speeds of over 70 km/h. It's already a handful to drive this way. Imagine putting in a lipo, and getting a 10% or more performance boost in top speed, and even faster acceleration. So I keep using the 2 NiMh packs that came with the car when I bought it second hand, and when these die, perhaps I will get a lipo instead.


Coming back to your car, I think a lipo would do well, it would increase acceleration and top speed, and runtimes. And you already have the charger, so it's not a big investment to start driving with lipos.
SoloProFan is online now Find More Posts by SoloProFan
RCG Plus Member
Old Feb 03, 2013, 11:10 AM
Registered User
wehan's Avatar
Joined Jan 2013
79 Posts
Not sure about that esc but if you run a lipo on a non lipo esc you can easily drain the lipo to the point of no return. Other than that yes. Check to see if your esc has a lipo mode and if so I would but if not id switch esc's or stick to nimh.
wehan is offline Find More Posts by wehan
Reply With Quote
Old Feb 03, 2013, 02:36 PM
Did you check the FAQ already?
SoloProFan's Avatar
The Netherlands
Joined Jul 2010
12,092 Posts
Quote:
Originally Posted by wehan View Post
Not sure about that esc but if you run a lipo on a non lipo esc you can easily drain the lipo to the point of no return. Other than that yes. Check to see if your esc has a lipo mode and if so I would but if not id switch esc's or stick to nimh.
Correct, that is what I meant with "special warning system", which is not present in older brushed ESC. But a seperate Lipo-saver/monitor will fill this gap. I use these in my older cars, that have been upgraded to lipo-power, and it works well for me.


Quote:
Originally Posted by SoloProFan View Post
You need special warning system to prevent discharging them too low, while on NiMh you can easily notice the pack is starting to dump, and stop before problems arise.
SoloProFan is online now Find More Posts by SoloProFan
RCG Plus Member
Old Feb 06, 2013, 11:33 PM
Registered User
Joined Feb 2006
30 Posts
I appreciate the advice. I have a Quanum battery telemetry to watch the voltage.
dma251 is offline Find More Posts by dma251
Reply With Quote
Old Feb 07, 2013, 12:27 AM
Did you check the FAQ already?
SoloProFan's Avatar
The Netherlands
Joined Jul 2010
12,092 Posts
If that system is accurate and has an option for setting the warning level, it could be enough. Still, a seperate lipo-saver/buzzer is only a few bucks from Hobby King for instance, so you could use it as extra security.
SoloProFan is online now Find More Posts by SoloProFan
RCG Plus Member
Old Feb 07, 2013, 08:48 AM
Registered User
Joined Feb 2006
30 Posts
I've got several of the cheap low voltage alarms and dozens of lipo batteries. Thanks for the advice. I just can't see introducing nmhd batteries into my lipo family!
dma251 is offline Find More Posts by dma251
Reply With Quote
Old Feb 17, 2013, 05:50 PM
Registered User
United States, SC, Irmo
Joined Sep 2011
4,544 Posts
I'm glad someone asked this question because I was going to create a thread asking about this. In the process to convert ALL my lipos to XT60 connectors, I have also started using some cheap lipo packs I got from ebay in my brushed cars that do not have LVC. I have just watched the car today and stopped after about 7 minutes and the voltage was 3.8/cell. Way quicker discharge than I expected. This was a 3000mah battery so I exected more than that, I have a 4000 on the way. But the car was also a lot faster! I was amazed. I will also use little lipo alarms, but these are set to 3.3v, and this is a lot lower than I want to go. This is borderline damaging the pack. I don't like to discharge below 3.7. I wonder if I can use a little voltage meter with a readout and watch that while driving?

Thinking about run times again, I did buy the cheapest lipos out there, it's probable that the mah ratings are inflated, that coupled with the increased amperage supplied would make sense with the run time I got. I thought it was a tas light for a 3000mah. I'll bet the 4000 I ordered is more like a 3000. Still, worth the money.
shahram72 is offline Find More Posts by shahram72
Reply With Quote
Old Feb 17, 2013, 07:47 PM
Registered User
Joined Feb 2006
30 Posts
Well, I did attempt to run a 3800mah 2s lipo on my new Redcat Volcano (brushed) and the results were very impressive... ....for a little while.

It ran wicked fast. Seriously fast. But the motor got so hot it melted the plastic fan inside the motor case by the brushes. The fan Bounced around until it broke off the blades and disintegrated. I picked all the pieces out of the motor with tweezers, and now it's running on the original 1800 man nimh.

It still doesn't make a lot of sense to me electrically speaking.

Any good charger will tell you exactly how many may you are putting back into the battery, so that should tell you right there the battery's actual capacity. I have been using lipos for years in my helis, and I routinely run them down to about 3.5v and I have been running a lot of my turnigy packs for literally years.

The best batteries for the money are turnigy nanotechs in m my opinion.
dma251 is offline Find More Posts by dma251
Reply With Quote
Old Feb 18, 2013, 04:21 AM
Did you check the FAQ already?
SoloProFan's Avatar
The Netherlands
Joined Jul 2010
12,092 Posts
If a motor is already running on the edge with NiCad or NiMh, the additional power of lipo can indeed prove to be too much. NiCad and NiMh usually act a little as "current limiter" reducing the current that runs through the motor during acceleration. A lipo can deliver more A, as you can see, usually acceleration gets a bigger boost than pure top speed, when moving to lipo.

Always check temps when trying something new, to make sure all components are still "happy".
SoloProFan is online now Find More Posts by SoloProFan
RCG Plus Member
Old Feb 18, 2013, 01:32 PM
Registered User
United States, SC, Irmo
Joined Sep 2011
4,544 Posts
I have the same truck, just the exceed version, and noticed that the motor was so hot after running, that the leaves stuck under it were burning! So I guess putting the 4000 is not a good idea. I think I just need to keep my run times down and let the motor cool. I already have a hopped pup motor for this car and it should be able to better handle the increased current, but honestly it does not need a hop up now. I have never seen a Mabuchi 540 type motor run so fast. So we need to keep the run times down or risk burning something up. But no big deal, these motors and ESC's are dirt cheap. I DO have a heatsink on my motor and now I think it's really needed!
shahram72 is offline Find More Posts by shahram72
Reply With Quote
Old Feb 18, 2013, 01:58 PM
Did you check the FAQ already?
SoloProFan's Avatar
The Netherlands
Joined Jul 2010
12,092 Posts
Perhaps, since you have increased top speed due to the stronger battery, you could take the pinion 1 tooth or 2 teeth lower, so the motor doesn't have to work so hard.
SoloProFan is online now Find More Posts by SoloProFan
RCG Plus Member
Old Feb 18, 2013, 02:31 PM
Registered User
United States, SC, Irmo
Joined Sep 2011
4,544 Posts
Quote:
Originally Posted by SoloProFan View Post
Perhaps, since you have increased top speed due to the stronger battery, you could take the pinion 1 tooth or 2 teeth lower, so the motor doesn't have to work so hard.

What are you talking about? We finally got the car running how we like it!

But seriously, this is not a bad idea, it would reduce strain on the motor.
shahram72 is offline Find More Posts by shahram72
Reply With Quote
Old Feb 19, 2013, 03:03 AM
Did you check the FAQ already?
SoloProFan's Avatar
The Netherlands
Joined Jul 2010
12,092 Posts
Indeed, if the motor gets strained too much, it will actually perform less than with a lower gearing. As the motor heats up it's performance will suffer, making it work a little less hard could make it perform more steadily, instead if just going fast a few minutes, then requiring a cool down.

Plus, gearing down will usually increase acceleration, and this might make the car feel much faster, even when top speed could be slightly lower then.
SoloProFan is online now Find More Posts by SoloProFan
RCG Plus Member
Old Feb 19, 2013, 03:09 AM
Registered User
United States, SC, Irmo
Joined Sep 2011
4,544 Posts
Yeah, top speed is over rated. The brushed trucks and cars are fast enough for me in my back yard. I have s few brushless models, and I just crash when I go fast. Don't even ask what happened when my nitro buggy went into 2nd gear!!!
shahram72 is offline Find More Posts by shahram72
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Gmade R1 - Lipo instead of Nicd?? Help?? phishintodd Rock Crawlers 3 Jan 14, 2013 11:38 AM
Sold 2s 7.4v 5000 mAh Lipo Battery packs xtremetoyz Cars - Cars and Parts (FS/W) 3 Jan 06, 2013 10:04 PM
Question instead of UBEC, can I use a 2s Lipo to power my Servos? rclab1 Electric Plane Talk 7 Nov 15, 2010 11:38 AM
Question 7.2v NiCd to a lipo help! rokhaul Off-road Cars 1 Nov 09, 2010 05:36 PM
Discussion TT 999 Electric: 7.2v NiCd vs 11.1v LiPo WOW!! tbitz Motorcycles 15 Dec 26, 2006 10:17 PM