What is the max safe temperature for a nimh battery???

[dirt101]

wow 300 beats my record. I heated some 3800 tenergies to 210F a couple of times then I went lipo. lipos havent seen more than 107F the whole time I have had them and its nearly 100 here now.

[What's_nitro?]

Originally Posted by dirt101

Lipos havent seen more than 107F the whole time I have had them and its nearly 100 here now.

Wow! Either you drive your truck like an old woman, or you need a bigger motor!

[dirt101]

I think my 1515 is big enough. I wouldnt say I drive like an old woman, but I would say im not jumpy. I have finally learned to drive smooth.

[What's_nitro?]

Lol... But yes throttle control makes a big difference in battery temps. Especially with Nixx. They'll heat up quickly if they constantly see ~60A sustained loads during acceleration. Most Nixx cells are rated for only ~35A.

Originally Posted by Duster_360

Here's some guidelines -

http://www.rc-monster.com/forum/showthread.php?t=2200

Besides the obvious - you have the body vented I hope, run a fan of some kind. I run a novak setup on esc and a pr of integy fans on the motor heatsinks.

I run 7 cell paks in my "stock" Emaxx, and only the motors get hot - 7 cell Maxamps 4400s. I'm still running brushed motors in it and they get 160-170F. I have to let it cool down between pacs. Batts are warm - a little cooler that when they come off charger. I asked when I got my 4400s if they needed breakin - Jason said no. Yours may be diff, you might want to run them easy for a few cycles. I've always heard temps like 160F is damaging the cells - that damage appears as shorter batt life.

Thanks for the link - that's exactly what I am looking for. Guess my "stock" E-Maxx isn't going to be stock much longer. I need to get a fan or two me thinks... Will adding fans actually draw more current and therefore make the battery temp issue worse though?

I think I will also contact the battery manufacturer, that's a good idea. And I was already thinking I would have to let it cool between runs, so I guess it's a good thing I also have my Revo! It's nitro, so I don't have to worry about recharging it. I'm having a lot of fun with the E-Maxx though, especially for a truck right out of the box.

Someday (in the distant future I am afraid), I'd like to build one (a Revo or E-Maxx) from scratch and do the whole brushless/lipo thing. I don't have the time or moeny to do it now though. Any idea if lipos work in an E-Maxx without replacing motor and ESC?

[tc3_racer_001]

fans draw a few seconds of runtime, if that.... they contain TINY motors (brushless at that) which draw around .05-0.2 A.


a piece of bark will hurt your runtime more than the small fans.

[QUOTE=Motoman;170803]It's funny that I kind-of stumbled upon this thread because I was running my XXX-T MF2 today with a "frankenstein" battery I made out of 5 new cells and 2 old cells(7 cell Ni-Cd 2400). I guess the 2 old cells were bad because I got 1 or both of the old cells to vent. I wasn't even running it hard. I checked the temp on one of the old cells and it was 300+ F. the new cells were only like 130F.

I believe the temp record you made was not real temp of the cell. Since you use a temp gun, it has a larger error in shiny metal material. The reflectiveity is hight for the ir temp gun. Try to avoid to measure cells without any cover and stick.

[Motoman]

Gallagher:
I know what you mean about measuring the temperature of reflective surfaces, but trust me it wasn't as shiny as it looks in the picture after it overheated. It does have a heatshrink covering on the cells but they are not the labeled kind. Also, the error increases as you move further away from the surface, and as you can see in the picture I had the temp gun touching it. My experience with the error in reading reflective surfaces has been that the temp gun actually reads less than the real temperature and not the other way. So, the cell had to be at least 300 maybe even a little more especially because I took that reading after I came inside my house about 3 or 4 minutes after I stopped running the truck.

dirt101:
I also noticed that a properly sized lipo is less susceptible to overheating. I would rather spend a little more for a lipo than buy another NiXX. There's a lot of people that think that NiXX are still cheaper, but if you compare the price of a decent lipo to that of a good NiXX it's really not a big difference.

Does anyone know at what temperature smoke starts to come out of the vents of the cell?? The bottom line here I think is that the capacity of the cells was way too low and therefore the discharge rate was also too low.

Originally Posted by BoilermakerU

...... Any idea if lipos work in an E-Maxx without replacing motor and ESC?

I haven't tried it with my Emaxx. Just concerned about possibly smoking the esc I guess, motors wouldn't worry me at all. In theory, lipos shouldn't be any diff than 7cell pacs and thats all I've ever run in mine.

[Motoman]

You would need to have a separate low-voltage cutoff module, because I don't think the EVX has one.

^^Def, there is no lvc in the evx.

Originally Posted by Duster_360

Besides the obvious - you have the body vented I hope, run a fan of some kind. I run a novak setup on esc and a pr of integy fans on the motor heatsinks.

I have the side windows cut out, but no fans - yet. I guess that's my next step. What's the best way to connect the fans? Solder them to the battery leads on the ESC? I noticed the reciever has a socket that says Batt on it. Is that to plug a battery into or to draw battery power out of? Could that be used?

Off to order a couple of fans!

Yeah.

That's the easiest - just wire them so you have a plug that'll plugin the batt slot in the rx. This drains a little away from the servos, but unless you get a power draining fan, it shouldn't be noticeable.

If you're runnning nitro, its for a batt. If you have a 3rd channels in the rx you could you use that if you were running nitro - all the slots have power.

Originally Posted by Duster_360

...just wire them so you have a plug that'll plugin the batt slot in the rx. This drains a little away from the servos, but unless you get a power draining fan, it shouldn't be noticeable...

Thanks, that helps. I'm getting the Novak fans mentioned, so according to tc3 racer, a piece of bark draws more current!

I'll just wire them all into one plug ans plug it into the reciever. Here's hoping for cooler runs!