Battery questions?

[dragr1]

Newb to the RC world and I just bought 2 used Traxxas Emaxx's for me and my son. They are 2 years old, so not the newest version.

They need batteries and I've been looking at the Venom batteries on ebay. The Emaxx's take (2) 6 cell, 7.2V NiMH batteries per car.

What would the run time difference be between 2400 mah and 3000 mah batteries?

How about 4200 mah batteries?

Thanks!

Also, posted in the Traxxas section

[Charlie-III]

NiCD/NiMH can work. Depending on the ESC and your chargers, most of us will say make the jump to LiPO.

Much smaller & lighter for the power.

I still use NiMH in carpet cars, they're fine.

I will say to stay away from the Tamiya connectors (white rectangular plugs) since they WILL be an issue down the road.

Most use Deans connectors, there are other brands as well.

[taco08jk]

I dont know how many minutes difference there is between 2400 to 3000 mah but from what I remember those EMaxx's were power hungry, so I would opt for the 4200.

[dragr1]

So, if it requires a 6 cell, 7.2 V NiMH battery, can I just use a Lipo instead?

Also, these are not brushless rigs

[taco08jk]

You dont have to be brushless to run lipo's, just replace those 6 cells with 2 cell lipo's. You will be so much happier with the lipo's. 2s lipo's and 2 cell lipos are one in the same, that confuses some people who are new to lipo's.

[Rockridge]

I'd first look to make sure your esc is lipo compatible... ie has a low voltage cut off. I'd Also do a google search and do a little background reading on lipos so that u have an idea of how to safely use them.
Second u might want to check and make sure your charger can charge lipos.... If not u will also need to pick one up.

[dragr1]

Originally Posted by taco08jk

You dont have to be brushless to run lipo's, just replace those 6 cells with 2 cell lipo's. You will be so much happier with the lipo's. 2s lipo's and 2 cell lipos are one in the same, that confuses some people who are new to lipo's.

What about the Nimh being 7.2v and the lipo being 7.4v?

[dragr1]

Originally Posted by Rockridge

I'd first look to make sure your esc is lipo compatible... ie has a low voltage cut off. I'd Also do a google search and do a little background reading on lipos so that u have an idea of how to safely use them.
Second u might want to check and make sure your charger can charge lipos.... If not u will also need to pick one up.

Forgive my ignorance, but what is the esc?

[Bowler]

Originally Posted by dragr1

Forgive my ignorance, but what is the esc?

ESC= Electronic Speed Controller

[SwampDawg]

speed controller

[Rockridge]

Ya sorry... Electronic speed control. Depending on what u have for an ESC and charger, it might be Cheeper to stay with NiMH batts for the time being. Long term u may want to research lipo setups and make the conversion a few parts at a time

As for your original question. Mah stands for milli amp hour. So 2600 Mah means that if u draw 2600 milli amps the batt will last for one hour. There for it really depends on what motor and ESC u r using.

[dragr1]

Just looking at pricing and at 3300 mah batteries, it seems that X$'s gets you 4 lipo's or for the same amount 8 nimh batteries.

Long term, I'm going to assume that the lipo's hold up better to repeated charging?

Remember I'm buying batteries for 2 cars and each car has 2 batteries.

[Rockridge]

The advantage to lipos r they r smaller,lighter and deliver a constant power. Where as NiMH power diminishes as use it. ie old cordless drills slow down as the batt dies( NiMH ) where the new drills have full power right until there dead

[taco08jk]

Originally Posted by dragr1

What about the Nimh being 7.2v and the lipo being 7.4v?

Yeah my bad, I just caught that. It shouldn't matter though. But like Rockridge said, check the esc first. And yes, do some reading up on lipo's first. If you dont go to lipo then just get the bigger mah batt for the longer runtime.

[Rockridge]

here is a little bit of a read on lipos.....https://sites.google.com/site/tjingu...po-terminology

[Trubble]

Originally Posted by dragr1

What about the Nimh being 7.2v and the lipo being 7.4v?

Those are just nominal voltages. A fully charged LiPo cell should be no more than 4.2 volts, thus a 2S will be 8.4 volts fully charged. A NiMh cell will be 1.45-1.5 volts when charged, so fully charged 6 cell will be 8.7-9.0 volts.
You should be just fine with the LiPos from a voltage standpoint, but like was mentioned there's no such thing as too much amps for that truck. Get the biggest mAh's and the highest C rating you can afford. (I think C rating is going to be more important than mAh in this truck, personally, but the two do kinda go hand-in-hand) Turn on your LVC (if you have one), or install an LVA so you don't discharge your LiPos too low, and you should be good to go.

[dragr1]

I think for now, I am going to order (4) Nimh 3000 mah batteries to get us going. The cars that I bought should be here late this week and I need to have the batteries when the cars get here. One car will be my 7 year olds birthday present so it needs to run right away. These batteries are only $19 each with free shipping-Venom brand with a multi plug.

After that I'll see if the Lipo's are an option to use on the cars and I'll either go that route or order (4) more Nimh batteries in a higher mah-found some 5000 mah Nimh batteries for $40 each with free shipping or might even just order (4) more in 3000 mah for the price.

[SwampDawg]

i just got myself a 3300 mAh stickpack lastweek but will be going the LiPo route later on. (funds....)
as for the 3300 mAh, i get somewhere around 20minutes or so but this is only with 1 motor (brushless)