RC-Monster Forums - RCM Lipo impressions

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Quote:

Originally Posted by BrianG (Post 237810)

I picked up a couple of Mike's new lipos (5s2p 5Ah 25c) and ran them around a little. I don't have an eagletree and the outside temps are a bit nippy, but they ran great!

After having problems with my GTP and MBX5/CORR conversion (blew ESCs), I decided to discharge the lipos for storage along with my 4s2p 5Ah Maxamps pack. But I figured I would do a little testing at the same time so I charged everything up fresh.

I use a custom CC discharge circuit (darlington transistors and power resistor setup) that will draw 10A from batteries ~10v up around 5s (the transistor and resistor setup gets quite hot even with a fan at 5s - but that's 185w too). I hook up a balancer and use a voltmeter to monitor cell voltage to get to my desired 3.5v/cell storage level.

With the MA 4s 5Ah pack hooked up, that 10A load dropped the voltage by 0.48v. When it hit my 3.5v/cell threshold, it had taken out about 2300mAh. Various cell LEDS on the balancer (LBA10) would flicker on and off during this time. Removing the load brought the no load voltage up to 3.73v/cell.

With Mike's 5s 5Ah packs hooked up, the same 10A load dropped the voltage by around 0.08v (fluctuated between 0.07 and 0.08v). When my 3.5v/cell threshold was reached, it had taken 4.36Ah out of the cell. Cell 3 on the same balancer flickered for about 30 seconds once. Removing the load brought the no-load voltage up to 3.67v.

Cell resistance is not linear so you can't really say how much voltage will drop at the rated C value simply by using the 10A load and voltage drop figures. Yeah, it's not the best test, but it certainly hints at a lot as far as performance goes.

Hi Brian,

If you're looking for a large controllable load to discharge with, I have a few ideas.

How about taking a Monster Mamba, put it in brushed mode. Very Controllable with a servo tester.

Then for a load, how about a regular space heater? Inductive coils that get glowing red hot, but are "cooled" by the fan which circulates the heat.

Just hook your monitoring equipment up between the ESC and the Batteries being tested.

This should be good for 100 amps + like you're looking for.

If you desire 200 amps+, I'm sure there is a way to parrallel a couple of "brushed" mode ESC's since this type of operation doesn't require any type of EMF for timing or switching.

On the load, to raise it's Wattage output capability, I would think increasing airflow should raise the limitation before the coils melt down.

Just a few thoughts. :yes:

do we know who makes these packs? or what other companies sell relabeled ones? just trying to see if I can find other reviews for the same pack.

@sikes: Hmm, I guess I missed your post. Using a high current ESC to provide some adjustability sounds like a great idea. As for the heating coil idea; I dunno. Ideally, this system should be usable to test 2s packs up to 5s packs (maybe even 6s), but the resistance needed to generate enough current at 2s is quite low and not sure if a heating coil is made for such low voltage. I'll have to dig around. I guess light bulbs would work too, but then up against the wide voltage range issue again.

@gixxer: I've heard speculation that they were "chargery" cells, but when I look at their site, I don't see any 25C 2.5Ah cells (only 20C), which is the packs I have are made from. I think only Mike knows...

Has anyone ran the 5200mah 2s packs yet?

i think its time mike should put out some erevo lipo combos, when he gets his next shipment in... i know that his 3s2p 5000s fit and also the 2s3p 7500 version (there are 6 total cells in each pack x2 for either a 6s 5000 or a 4s 7500 setup) i think theyll sell good especially with the 2s3p 7500s to use with the new brushless edition revo to be out mid january (same time mike will have more lipos in)

Quote:

Originally Posted by rootar (Post 243363)

If he did the 7500 2s, i'd be looking hard at them for replacement of my 8000 maxamps for my T4, I plan to run Pro truck in RC pro this year

If I could get a 25c 2s 7500 that would fit in my e-revo, I would get at least 4 of them. Sounds like mike has found a great battery for us! BrianG, thanks for the review

Quote:

Originally Posted by BrianG (Post 242415)

@gixxer: I've heard speculation that they were "chargery" cells, but when I look at their site, I don't see any 25C 2.5Ah cells (only 20C), which is the packs I have are made from. I think only Mike knows...

I picked up some chargery lipos. They are different from Mikes. also, mike confirmed that he is not using chargery lipos.

Quote:

Originally Posted by brushlessboy16 (Post 242931)

Has anyone ran the 5200mah 2s packs yet?

I ran them 9 minutes then my shocktower broke. Next day go bashing again and run them about 11 minutes and this time my rear shocks head come out. all that only one charge. Now my charger read my lipo voltage 3.72v. So I think will give you about 25-30 minutes

I can told you they run cool and hold the voltage.

what type of balancer connector does it use?

The ones I have use Thunderpower balance plugs.

I have run about 7 or 8 cycles through my packs, they are rediculously powerful compared to zippies... 2 of them paired with the MMM combo is pure win... full review will come later on...

Oh Man, I'd definitely suck up some 7500 2S packs for sure.....

Quote:

Originally Posted by brushlessboy16 (Post 250485)

I have run about 7 or 8 cycles through my packs, they are rediculously powerful compared to zippies...

Sssshhh, it's ridiculous, unless Websters have sunk to a[nother] new low :wink: :rofl:

has anyone tried the 6s 2500's? i think they would work great in my rc8, but would the "c" rating be enough on 6s? runnin a 1512 3d @15/46 and am looking to upgrade from my MA 4000 pack i run right now. i know the recomended min. is 75A for the mmm but these packs are looking better each time i drool over them. any thoughts? runtime is not really an issue on the track 10-15 mins would be plenty.

They can handle that setup. I tested the cells on 5s in a truggy with a 1515/1y geared for 50+mph. They held better voltage under the same amp draw as my MA 5000mah pack, so if you are using a MA 4000mah pack, these will have a bit more snap.