lipo trouble

[Thorsteenster]

Originally Posted by Espeefan

I've always feared the LiPo packs myself, even though they are pretty safe. Something about the need to store them in a fireproof container or sack, and charge them in one as well freaks me out. Chances are it will rarely burst and start a fire, if you treat them well, and LiPo packs can be found everywhere in your house already. Cameras, cell phones, your electric shaver, ect. But I have been looking at the LiFe cells, which are supposed to be as safe as NiMh cells, have a longer life with more charge cycles, and they also can handle some serious discharge currents. Even better then LiPo packs, plus you can recharge them faster. The only downside is they are really pricey!

Same here on the LiPo's. After getting back into RC a few years back LiPo's were pretty much just coming into the scene. I tried it and wow, it really is some battery. I had Scorpion batteries and charger, I still have a battery and the charger.
I've since gone to A123 LiFe batteries, they are much less hassle, no worries about over discharging, LiPo fires etc etc. Although each cell is only rated at 3.3v nominal vs LiPo 3.6v.
As far as safety goes, this are a much better battery type, I would recomend them to anyone looking to go to lithium type batteries or tired of LiPo's.
The LiFe's are getting more popular with Max Amps now offering LiFe packes in flat cells. Mine are round cells and a little bigger than a sub C cell. I got mine from a DeWalt battery pack from Ebay for under $100. I want to say it had 10 cells but don't remember exactly. Nice thing is they are easy to solder because they have tabs spot welded on for soldering, so no worries of damaging the cells.
Any who, sorry to get off topic.

Yeah, now that Willy mentions it I remember reading somewhere the MAH rating needs to be high enough, easily figured out with some magical formula I have no comrehension of.....
lol
That's interesting on the LiIons, I'll have to see if my charger handles them and check them out. It would be nice to have a cheaper alternative for RC's not needing high C rated batteries.

[ihbuilder]

I run Li-ions in my few trucks , they are actually the milwaukee m12 . you pop the black handle piece off and you can slide it in a 2"dia tank . I get about 2hrs running time ,(have to clock it some time ) . what I like about them ,is they are duel purpose ,for play and for building and last a long time .

[doodlebug]

Originally Posted by ihbuilder

I run Li-ions in my few trucks , they are actually the milwaukee m12 . you pop the black handle piece off and you can slide it in a 2"dia tank . I get about 2hrs running time ,(have to clock it some time ) . what I like about them ,is they are duel purpose ,for play and for building and last a long time .

Hey Steve, are the M-12 batteries working out for the rc stuff? Still happy?
I did have one new battery that was bad, warranty replaced it. I have the greasegun, borescope, and a compact driver.
Thank's, Neil#2 aka doodlebug.

[Espeefan]

One other thing I wanted to point out is if one compares a typical 6.6 volt, two cell LiFe pack to a standard 7.2 volt, six cell NiMh pack, the LiFe pack looks a little weak. What is important to remember though is that we run our packs under a load. Sometimes a severe load, and under a load like that, nonimal voltage ratings drop off a lot with NiMh packs. Not so much with a LiFe pack, or LiPo pack. Your 7.2 volt NiMh pack might be capable of maintaining a 6 volt or less rating underload, especially as it reaches the point where it has given up half it's capacity already. At it's very near discharged state, a good NiMh pack might only be providing 5.4 volts or less. A LiFe cell will maintain it's 6.6 volt rating right up to the end of it's capacity. So even if you are worried about the LiFe pack looking like it has less voltage, it's more capable of maintaining that voltage, even under load. It really doesn't give any performance away to a NiMh pack like you could think. Don't just look at the nominal voltage ratings, in other words.

Now let's switch subjects. The forumla for figuring out a LiPo pack's max continous current rating is to multiply the pack capacity by the C rating.

Pack capacity is the mili-amp rating. The C rating is the discharge capacity, or how fast you can discharge the pack. To figure out the maximum continous discharge rating you have to multiply the C rating by the battery capacity. Example - a 2200 mili-amp pack that has a C rating of 10C.

Convert the 2200 mili-amp rating to full amps. One mili amp is .001, so we multiply 2200 by .001 to get 2.2 amps. Simple, right? Now take 2.2 amps and multiply that by the C rating, which is 10. That would be 22 amps, and this is the continous discharge rating for your pack.

Hope this will help.

[ddc333]

There was a really informative thread about lipo's on the garden forum any chance any one still has some of that info ??

[tc1cat]

That thread was written by Paul- Tamiya Cowboy. Hopefully he still has all of the info.