Ways to protect MMM when used with subpar batts

[hoovdog]

Originally Posted by bryan

So, who does determine the quality of a battery other than the one setting a high msrp..

That certainly is the tricky question. I'm always searching for the next best bang for the buck combination so I did a little purchasing for a not so experiment, experiment. :) Bought a pair of Turnigy 20C 4S 3600mAh packs ($45 each) and a pair of Hyperion G3 35C 2S 6500mAh pack ($97 each). I believe these to be the opposite ends of the spectrum from my readings. One is continually called cheap and the other the cat's meow. Now, the included "Do the math" sheet would indicate that I take 80% of the rated continuous draw. OK, so my Turnigy packs will yield 115.2A continuous draw which is certainly above the cutoff on that insert. The problem is most people will say these packs are insufficient "cheap" so where exactly is this boundary line crossed? I'm just looking for some kind of conclusion that says any battery (within reason) can be good as long as it's used in the correct setup. Granted, I'm pretty sure I know which will perform better (love my G3's but looking forward to running these new 6500's :) )

I'm going to take a slightly lightened (via aluminum upgrades) ERBE geared for approximately 40mph on 4S which I believe to be fairly modest for the setup being used. Now, does this general setup make my Turnigy batteries insufficient or would it need me to try for a 50mph gearing to be insufficient? It is feasible to think a user couple pick up a pair of cheap batteries and only wish to run 30mph. I would then tend to believe low rated batteries are sufficient yet a lot of people will discredit them instantly without knowing the details. It's then possible to say that cheap batteries of a certain brand will be great at 30mph, ok at 40mph, and not such a good idea at 50mph. Is this a better way of yielding information to new users? I guess my point is doesn't it greatly depend on how far a user is pushing the setup that dictates the battery's usefulness?

I did take notice to what Bernie had mentioned which I believe was somewhat related to my point. "The other issue with cheap batteries is that if they do work without damaging the ESC you will get short cycle life out of them, perhaps 50 - 75 cycles." I completely agree with this statement but does this still mean the "cheap" batteries are not sufficient? They won't last as long but they do work so once again that boundary creeps up.

I also took note of what suicidneil wrote: "Castle doesnt recommend the biggest and baddeest batts to use with the MMM, they just say dont go buying crappy chinese batts or naff ebay items that cost $20 each, yet claim 40c like proper lipos in the ~$200 range can actually manage." Also a statement I agree with but where is the data for the masses to determine which chinese packs are the overrated packs? What's a crappy chinese battery mean or does this mean any chinese battery? Not really looking for a response on this but you can hopefully see what I'm trying to say.

I guess an underlying theme for my post is I fully understand where newcomers have difficulty piecing together a quality setup for their uses. I think it's awesome that some will share their data with everyone to help decision making and weed out the bad products but it's still extremely difficult because everyone's driving style etc. is so different. WOW....I rambled on enough! :)

The original poster of this thread asked about ways to protect MMM when used with sub-par batteries.

Obviously, using good batteries is better, but it doesn't answer his question.

I was thinking something along the way of using extra capacitors and/or TVSes.
Would that help to protect a MMM?

Avner.

[Unsullied_Spy]

High MSRP is not always indicative of a high-quality battery. My pair of Maxamps packs ran me about $500 after buying the warranty, "hard case," shipping, etc. and both of my Monsters that have burned up blew out while running those lipos. On the other hand, I paid $30/ea. for my Turnigy lipos and have never burned up an ESC while running them and they stay balanced better.

Spy,

Not sure how long I was out there, and didn't have a transponder in it either. The pack was warm, but not overly so. I'm not concerned about the batts at all, just don't want to blow out the controller. Bernies seems to be saying that the soft batts can do that, so it appears to be a moot point.

I went looking at the Zippys, but the tray is only 138 x 47. I think their packs were a bit bigger than that. I need to look around for someone else who has this car and see what they're running. Of course, there is AE's new Reedy pack for this car, and it's a real steal at $300.

[RC-Monster Mike]

Determining what batteries have accurate ratings and which ones don't is indeed the real challenge. Better batteries will yield better results(more cycles, more power less problems, etc.), but how does one determine what batteries to use?
Other people's experience is one way - Turnigy/Zippy packs get mixed reviews, for instance. Hyperion G3 packs get glowingly good reviews. Maxamps packs get mixed reviews. ETC. The list goes on and will continue to grow. Over time, the better batteries will show themselves with less overall reported problems.
Reported success and reported failures need to be taken with a grain of salt, though. Some people just can't or don't drive hard enough to maximize the system potential or to realize their battery's downfalls. The Zippy or other low end packs that work great for a casual user that doesn't use brakes a lot, or putts around at low speed is not indicitive of a safe and recommended setup for a skilled and competitive racer, for example. While they may appear to be a good value on the surface, long term results are likely to tell a different story. Over time, the better batteries will show themselves with less overall reported problems. I have seen more reported failures with Zippy packs, yet some people swear by them. No setup is exempt from occasional failure, either. Experienced users with premium equipment can have troubles, though it is going to be far less common.

I agree with Bernie(and posted a similar analogy some time ago) - if you want Ferarri performance, you can't buy Yugo batteries and expect good results for any length of time. If you run cheap batteries, I suggest leaving yourself some head room in the setup - gear conservative, minimize hard braking, etc. Most importantly...take your licks like a man(or woman) if things go sideways - all the money you saved on batteries can go towards a replacement controller. :)

[BrianG]

Like you said Mike, I think the usage plays a HUGE role in determining what works and what doesn't. Someone who is looking for long runtimes just playing around in the yard is probably geared low with settings to maximize runtime. Sure is different than a hardcore racer (where weight to power ratio matters) or the guy trying to break speed records with a MT.

My personal experience with Turnigy has been mixed as well. Eagletree tests show very good voltage under load and they are barely warm after a run. However, out of 5 packs I had/have, one had a defective cell (wouldn't hold charge but returned that to the LHS for an exchange), and one cell on another one needed some TLC (needed to charge it individually) but now stays balanced all the time. The other 3 have been flawless. Seems like if they run right and stay balanced for the first 4-5 cycles, then you are good to go. Far outperforms certain other overpriced packs, but then again, warranty for Turnigy is not exactly ideal. Basically, you're gambling with them. You could hit the jackpot with all good packs, break out even (or maybe a little better) with a few bad packs, or take a hit if QC was asleep that day. As far as cycle life, time will tell.

[hoovdog]

Mike and BrianG....In your own words I believe you are reiterating exactly what I was trying to say so thanks for your replies. I get so frustrated when I read these one liners around certain packs being cheap junk without qualifying the statement. As we all know, not all people can afford to buy the known powerhouse packs so I'm always looking to find fellow locals a less expensive alternative WITH setup limits. I believe that to be the real help.

I'm hoping an EagleTree logger is in my B-Day gifts (thanks dear! :) ) so I plan on doing as much testing and data sharing as possible.

[RC-Monster Mike]

I think BrianG touched on a HUGE factor to consider with the lower priced packs - CONSISTENCY. I don't doubt that some folks have gotten Turnigy/Zippy packs that perform great, but others have issues. The Hyperion G3, conversely, are consistently great performers. BrianG has the knowledge and ability(and willingness) to test his batteries and determine their worthiness - most users don't share these qualities. The low end packs require the user to assume more risk, as there is a greater chance of lower quality. Not all brand x packs are bad, but without the equipment, knowledge and ability to test the individual packs, the chances of getting a problem pack is significantly higher with the "low-end" packs.

[BrianG]

Thanks Mike.

It's just hard for people (me included) when they see that they can buy 3 Turnigy packs for the approximate price of 1 Hyperion or other good lipo. You know the Hyperion is better, no doubt there, but that pricetag sure is appealing. You take a chance and hope that at least two packs will last, and if one goes bad, oh well, you are still ahead. And if you don't use your vehicles all that ofen (I probably have only 75 cycles on my oldest lipo) cycle life isn't that important because by the time it becomes an issue, the current market offerings are better, smaller, lighter, cheaper.

You're definitely right though, the knowledge on how far to use any cell is vital - especially so with the lesser products. If I buy cheap, I expect cheap and use it in a setup that is not demanding. If it holds up extremely well, I may then step it up a notch. But I definitely do not slap any old battery in my heaviest vehicle, gear for world record speed runs, and then act surprised when my car is engulfed in flames.

[hoovdog]

I'm glad the discussion expanded on this topic. Personally, unless I'm playing around in the yard I'm running my Hyperions but I do want to find an operating space for the Turnigys. I have created a log for the new batteries I just purchased. Every charge and discharge is going to be recorded for the first 30 cycles to see what can be determined...if anything. I may expand that if it's deemed useful.

We'll be watching you Traxxas mod

[hoovdog]

Originally Posted by Freezebyte

We'll be watching you Traxxas mod

That's awfully nice of you but it's not polite to stare. Guess it's better than your original reply though. :)

This is all really interesting reading and certainly as a newb to the BL/Lipo world then by far the most difficult choice for me has been with batteries....it is a minefield....maybe literally in some cases!!!

I ended up just saying sod it, get a Hyperion 4S 6500mah....this has cost me a lot but everyone with far greater knowledge than me seems to rate them, good enough for me.

However, I am also going to look out for some good cheaper/secondhand packs or similar for just bashing and things where runtime is not so important. The Hyperion was mainly for the big mah to try to get a racing 20 minute final achieved on one battery.

But, when I buy cheap, I do it with the acceptance of risk and some personal responsibility. Not to say that if I get a cheaper pack from a store and it's crud that I won't expect a refund/exchange.....but that I do it knowing I might have some of that pain to go through....

OK, so the G3 VX 5000 is too big for the tray. Do I go with the CX 5000 or VX 4200?

[hoovdog]

Originally Posted by elcheapo

OK, so the G3 VX 5000 is too big for the tray. Do I go with the CX 5000 or VX 4200?

If ratings are true to spec then I'd take the VX 4200's as long as you feel you'll get the runtime you need. Prices seem to be really close to each other for that extra 22 amp buffer with the VX 4200. I only own VX packs but have been really interested to know if the CX packs will be sufficient for my uses. Anyone have any input as to how true to spec these packs are? It would be great to hear the CX packs are underrated!