Battery help!!

[subyhau]

I got a quick question, can I run me emaxx with this battery? And what battery would you recommend me? Please! Sorry for my english.

http://www.ebay.com/itm/TRAXXAS-2961...#ht_500wt_1219

[M n M]

Yes but you would need to do something different to hold it down to in the battery tray. Maybe velcro straps.

I guess my question is why spend that much money on a NiMH? For that much money I can get a 7600mah LiPo. Do you have a charger that can charge and balance LiPo batteries?

[M n M]

If your going to stay with NiMH look into something like the Traxxas 2960 battery. It's a FLAT 7 cell pack.

http://traxxas.com/products/parts/ba...batteries/nimh

[subyhau]

Ohh ok thankx, well i'm newbie in rc world, could you help me in what batteries should I go?

[subyhau]

Why LiPo? If I buy a LiPo I also need to buy a charger right? How many mah should I go? Is it plug n play?
Thanks and sorry to bother ):

[M n M]

Well first give us a run down on what your already have.

What model E-Maxx do you have?

What modifications or upgrades have you done to it?

Have you changed the motors or ESC?

What brand and model charger do you have? It may already be able to charge LiPo.

Reasons for using LiPo:

a. Longer life expectancy than NiMH
b. Longer run times than NiMH when comparing similar mah rating
c. LiPo deliver more power than NiMH
d. LiPo's deliver consistant levels of power longer and closer to the discharge point. Think of it like a flash light, when the power in the batteries get low the light gets dimmer and dimmer. With LiPo batteries the light would stay bright for the full life of the battery. It would only dim right before the battery is completely drained.
e. When comparing similar mah ratings LiPo are generally smaller and lighter.

Reasons for not using LiPo:
a. Requires special care when charging. They should be monitored when charging. They can be a bit more dangerous than NiMH.
b. You may need a new charger
c. The cost of LiPo are higher than NiMH
d. The rating terminology can be a bit confusing, you really need to do your homework.
e. LiPo's can be ruined if discharged to low
f. And because of the above reason they need to be used with added equipment like a Low Voltage Cutoff (LVC) or Low Voltage Alarm (LVA) or an ESC that has a Low Voltage Device added into the programing.

Here's a good link to start learning about LiPo's
http://robotwars.00server.com/tutorials.html

[subyhau]

M n M thanks for everything, I just call a friend he explained me everything
I'm gonna me using NiMH for a while since mi emaxx can't use LiPo, need to do some modifications and my friend told me that he can get me the batteries I want for 44.95 each one so it's ok.
Thank you so much! You help me a lot

[subyhau]

Do you have any idea how much time does a 5000mAh battery last on the emaxx? And a 7 cell battery fit in the emaxx right?

[M n M]

I don't know what model E Maxx you have but a 7 cell NiMH should fit. Depending on how you run your truck you should get around 30-40 minutes out of a set of 5000mah batteries. As far a life span goes... I've had my NiMHs since October 2011. I cycle them at every 5th charge and they are still delivering great power and give me consistent run times.

[subyhau]

I don't know really what emaxx model I have, since my brother gave it to me he just gave me the emaxx nothing else, I need to buy batteries, charger and controller with green crystal.
How do I know what model I have? I remember when he was unboxing it and I think it was a 3905 but i'm not very sure.

[M n M]

3905 sounds right if you say you have to get a controller with the green crystal.

Does the truck have a long wire for an antenna? If so you have the 3905 model that has the 27mhz receiver.

Before you go spend money on a transmitter for that model look into upgrading to the 2.4ghz system. It includes a new receiver and radio. It's a much better system.

Here is a link to the Traxxas power up option. I have a buddy that did this through our local hobby store (LHS) for about $60.

I did see that this "Power Up" option through Traxxas is only good in the US and you would need to send in the old system.

But this link shows you what the sytem is in case you want to go this route.

http://www.traxxas.com/v2/powerup/part/?id=16

[subyhau]

Yes my truck has the long wire for the antenna.

So if I wanna upgrade I need to buy new receiver and the controller? Cause the controller that I saw just cost 30 and has green crystal

[M n M]

You can get a 27mhz radio and match the crystals. I'm just saying that the newer technology is the 2.4ghz system. The 2.4ghz system would require a radio, receiver and antenna.

[subyhau]

I think I'm gonna get the deal that I got, Im gonna stick with the old system.
Thank you M n M!

[M n M]

Your welcome.

[zigro_20]

What is the max number of cells or voltage u can run with a stock Emaxx 3905? Could i run 3 or 4 cells lipos, without upgrading ESC and motor?

[M n M]

What is the max number of cells or voltage u can run with a stock Emaxx 3905? Could i run 3 or 4 cells lipos, without upgrading ESC and motor?

I'm still a LiPo Noob but here is what I've been able to come up with in my research.

The Stock EVX-2 ESC is rated to operate between 7.2 and 16.8 volts. So in theory yes you could run a 3s or 4s LiPo on a stock EVX-2. Just one though, not two, just one battery because you don’t want to go over the rated voltage of the ESC. 3s = 11.1 volts and 4s = 14.8 volts.

Here are reasons why I went with 2 each 2s LiPo’s

1. 14.8 volt total (still within ESC rating)

2. They can be found that fit the chassis tray with no modification. If you go 3s or 4s the physical dimensions of the battery can be different than what the tray will allow. You would have to strap them in or some other method to keep them in place.

3. Direct connect / plug in. The power system on the E-Maxx is a parallel system, meaning that both batteries are drawn down somewhat equally (the side that powers the servos and receiver draw a little more but that’s another discussion). If you run one battery like a 3s or 4s then you have to fool the system in thinking it has 2 batteries connected. It’s done by adding a “Jumper”.

4. Weight distribution is still maintained with 2each 2s LiPo. This may not be a huge deal to some but I didn’t want to through the balance off what is already a beefy truck. I have thought that if one were to go with a 3s or 4s LiPo they could add something to match the weight to the other battery tray. Say maybe another 3s or 4s LiPo?

No of the reason listed above are hard to overcome. In fact there several great ideas on this site that will show and explain just how to do them. I just chose the easier, less evasive route when it came to picking out which LiPo to use.

[trax de max]

2 x 2s lipos is the easiest option

But you would need to buy a Low Voltage Alarm

[zigro_20]

I want 2 3s 11.1v for more power and speed. If im going to spend money I want a big change. Even though the EVX-2 is not meant to run 2 3s, would it still operate but maybe fry the ESC or motor later? Could anything else get damaged as well? If so I might do that, because I plan on upgrading to brushless sometime.

Also do all Low voltage alarms or Low voltage cut-offs have to be soldered in? Is there any that just plug into the battery?

[LD]

2 3s will fry everything real fast . It would be a big change but not one you'd like. Don't do it!!!

2 2s lipos will work great and you'll be ready when you step up to BL power .

[canavin77]

you would need to buy a Low Voltage Alarm

[trax de max]

you could use 3s+2s combo with the 2s on the bec side. but this comes at the expense of burning out the motors pretty quick. Since the titans aren't rebuildable it will be an expensive few runs.
You could swap out the titans for a single dewalt. With this you could buy new brushes off the internet very cheap and would be better with the 3s+2s combo.

[M n M]

Most Low Voltage Cutoffs have to be wired in (soldered or crimped). Most Low Voltage Alarms just plug into the balance port of the LiPo battery.

Pushing anything higher than 16.8 volts through that EVX-2 and you will burn something up. ESC or the motors, possibly both at once. It may not happen the first few time you run it but it will happen.

[PowerToTheMaxx]

Ya, dont overvolt the EVX-2, it might or might not work, but you probally will fry it and it dosn't give you much advantage

[goalieman3037]

I was wondering if anyone that has done the dewalt conversion, using the evx-2 ever ran 2 x 4s lipos in parallel, I now I need a lvc, on the bec side of the esc, I was just wondering if the lvc ( novak for 4s is what im looking at) will work ok if its on parallel batteries?