True RC pack info

[Topspeedtimmy]

I know quite a few people have been running True RC packs in their Revos and such, and I was wondering if the 10 and 15C packs hold true to their discharge rating. I gotta know because they are ominously cheap. Unlike the last packs I had , I want to know that these will last more than 70 cycles if they are run within spec. No one seems to mention how many cycles any of these low-price packs last.

[jhautz]

I have a almost 2 year old set of 5s 8000mah TrueRC 10C packs that have easlilly 250-300 cycles on them and they are still going strong. IMO TrueRC are good packs that do what they say. Better cells than many overrated 20c packs I've seen.

[jnev]

I have been running my 4s 8000mAH pack in my 1/8 buggy and in my Revo, and it is still going strong. I don't think I have ran 70 cycles through it, but I am expecting it to last well over 100 cycles.

[Patrick]

A couple of cells in my 5s2p 8000mah 10C set (2s2p and 3s2p connected in series) puffed up a bit after 5 or 6 months, and another cell only goes to about 1.5v even when the puffy cells are ~3.9v.
I ran it till it hit the LVC on my quark twice and they took 7400mahs. A little while later I did 26 minutes of a 30 minute race when the lvc kicked in, they only took 6400mah after that. Gradually they started getting worse until they only had about 5000mahs, then I noticed the 1.5v cell when I put it on the balancer.
I don't know how many cycles they did, but the had a fair bit of runtime on them, because they were the only set of batteries I used in that 6 months. I'd do a 5 minute race and use 1250-1600mah's, let it cool for a while, and then put it on charge it between races at 6 amps usually. I usually charged at less than 1C, especially at home.
I pretty much always used a balancer and they usually took a fair while to balance properly.
Set up is an neu 1515 2.5D (1700kv) with quark 125, in an e-maxx, then the last couple of months in a truggy. Geared for ~35mph for racing, and low to mid 40's sometimes for bashing. They never really seemed to get too warm, so I don't know if it's something I did wrong or what.
At the moment they're sitting in a lipo sack in a clay terracotta plant, in the garage with a foot or so of empty space around them, since I haven't decided what to do yet, or if it's worth asking true rc about them.
They seemed pretty good, especially for the price...until they went bad, but that doesn't seem to be normal.

[Topspeedtimmy]

These packs look nice because of the cheap price and high capacities, but I haven't seen anyone running the slightly more expensive and lighter 15C 6400mAh (96A) 2p packs over the 10C 8000mAh (80A) 2p ones. 6400 seems to be plenty of runtime, so lighter weight and more amps is worth the 1600mAh. A 4s2p 6400 mAh pack is $160 bucks. The Flightpower lite 5350mAh (91A) 4s1p can be purchased for around $185. So the question is, can I spare the 1Ah of capacity and pay the $25 premium just for a pack that might last longer than the TrueRC one?

Originally Posted by Topspeedtimmy

These packs look nice because of the cheap price and high capacities, but I haven't seen anyone running the slightly more expensive and lighter 15C 6400mAh (96A) 2p packs over the 10C 8000mAh (80A) 2p ones. 6400 seems to be plenty of runtime, so lighter weight and more amps is worth the 1600mAh. A 4s2p 6400 mAh pack is $160 bucks. The Flightpower lite 5350mAh (91A) 4s1p can be purchased for around $185. So the question is, can I spare the 1Ah of capacity and pay the $25 premium just for a pack that might last longer than the TrueRC one?

for $65 more you get this pack, which you would be much happier with


http://www.rc-monster.com/proddetail...=PQXP4s500025c

[lincpimp]

What motor/esc/gearing are you trying to run. The min for a 4s setup in a revo would be a 4900 25c pack, like a pair of trakpower lipos, or a 4900 4s flightpower.

i run twin 2s 15c's in my revo, from true rc, these packs run forever, i got the 8000's for 243 shipped these cells are awesome, with 240 amps constant, im not even touching half of that

[lincpimp]

How do you figure 240 amps constant?

Do you run the packs in series for 4s total? If so then you have 120 amps constant.

yea 4s and each pack is 120 amps constant so 240

[Sammus]

I got it backwards big greg. when they're in series you still only get 120A, the point is you have 120A at 14.8V, whereas parallel (2s config) would give you 240A at 7.4V - same power, just got in different ways.

i dont see how it doubles the volts but nothing else? so im only getting 8000 mah also, instead of 16000?

[Sammus]

Well thats just how electronics works. In series you will double the voltage, in parallel you will double the capacity. However you choose to combine the two packs, you will double the total power (power = voltage * current) a single pack is capable of.

well i know how electronics work, but this just confuses me, why double just one part of the pack? seems like they should just find a way to double mah and out put to, hmmm still sounds dumb to me lol

[Sammus]

Consider this:

Each pack is 7.4V with a capacity of 8000mAh, which means it can supply 8000mA at this voltage for one hour, or 8A for one hour, or 80A for 1/10th of an hour, or 120A for 1/15th of an hour = 4min = 240s. Now 120A @ 7.4V = 888W. Thats how much power the pack can supply, end of story. Power is energy per unit time, this means that the total energy the pack will give you is 888W * 240s = about 213kJ.

Now assume that we have it your way, and you combine the two packs and double both the capacity and the voltage output, then the pack has a capacity of 16,000mAh, and a voltage of 14.8V. This means, at this voltage, it will deliver 16A for an hour, 160A for 1/10th of an hour, or 240A for 1/15th of an hour = 4min = 240s. You would be supplying 240A @ 14.8V = 3552W over this time, which is a total energy output of of 240*3552 J = about 852 kJ - four times the energy of a single pack!

Now we just violated the first law of thermodynamics, no energy for free!

Or more generally, as far as we're concerned, energy is directly proportional to a product of the voltage, current and capacity. So if you double the number of packs, you can only double the total energy. Since voltage and current are already tied together with resistance (ohms law) the only options we have are to double the voltage or capacity of the pack. We achieve this by connection them in series or parallel respectively. To double the mah and the voltage, you would need 4 packs, and to connect them in a 2s2p configuration.