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40C vs. 50C+ difference??????

12K views 77 replies 38 participants last post by  OvalTrucker 
#1 ·
apparently nothing.

two 2400 mah cells rated @ 40c packed inside a unit rated at 4900 mah and 50+C, wired in parallel.

Why did I take it apart????

I was testing the packs, pump them up to 4.22 @ 1 amp on T35BL before discharging. First seven times went fine, redid a pack as a control, I fell asleep at the computer. I took it off at 4.55v and puffed......but didn't burn the house down.

Yes, I'm a dumba$$ for that.

But I did always find it weird a 40C and 50C pack from same company tested identical @ 35 amps, now I know why.

XXX784283
3.7V/40C
2400mah
2009.07.07

I'll have pics later, camera is in the garage and it's snowing.
 
#35 ·
guys if you take the time to email danny he will get back with you in a weeks time..many times i have asked him questions via email and i have always gotten responded to..he is one of the nicest guys you will meet..and he should be at the birds
 
#36 ·
the point mr.fish is that the SMC pack the man opened up appears to have been a mislabeled pack or purposely had 40c cells in it to get a quick sell off 50c hype,of course this doesn't suprize me as danny has craped on the rc world be fore . if other people find the same thing then people should ban SMC products.:mad:
 
#39 ·
How about the Benefit of doubt. A lot can play into this, and without actually having the ability to test @ 50c we can't be sure.
Danny has been in a position in the past to help Oval racing, and has done just that.
I know what it's like to have been wronged, so I empathize in regards to your discovery, but for now it's just thoeretic.
I've never had any trouble contacting Danny, and had the opportunity to meet him at the 'birds last year. He seemed to be a stand up guy. Let's give him a chance. I know he's been called out, but I don't think he follows the boards like he used to.
Also let's please keep it positive, or at the very least keep it from getting personal.
 
#40 ·
Here is my dilemma.

Had I not screwed up the pack, I would have never found out. I'm NOT looking for a replacement, the puffed pack was NOT SMC's fault, all mine.

But then again, I didn't get the pack I was sold. Likely the same happened to many folks.

I paid about $70 shipped on 9/14/09 to Superior Hobbies. I also bought a Trinity and SMC 40C from them in the same three day time frame.
 
#41 ·
Once again, you do not know that you did not get what you paid for unless you tested it @ 50C discharge and it did not produce the 4900 on the outside label.

I agree that an explanation would be appropriate and I give you credit for making it clear that the pack failure was your own doing. Lets hope that an email or call from you to the Manufacturer might get an answer of some kind.

Cheers!
 
#43 ·
Just a little thing to put things in perspective.

You have 2 cells, each rated at 40C wired in PARALLEL. Electrically speaking, each cell is capable of putting out 40C at the same time, meaning that the pack has a theoretical maximum output of 80C, based on the cells alone. Now, as a pack, many other things come into play, but it is very possible and plausible that a pack with 2 40C cells wired in parallel can be rated as a whole as 50C.

As for the difference between a 40C pack and a 50C pack, I dont think that our current chargers are adequate to see any difference. At 35 amps, you are discharging a 40C pack at roughly 18% of it's rated max sustained discharge current, while with a 50C you are discharging it at 14%. we would have to go to much higher amp draw to start to see something on our equipment. Something like 150 amps...

This does not mean that there are no difference in track performance from pack A to pack B. Just that C rating, under our racing conditions, doesn't mean any thing.

Martin Paradis
 
#44 · (Edited)
want to know if the overall C rating goes up if you hook up two or more batteries in parallel assuming that the batteries have the same specs or does it stay constant?
That's a good questions.

OK, lets assume we have one 40C 4900mah battery.

Tha maximum safe discharge rate for one cell would be:
40 x 4900mah = 196 amps

So if you have two 40C 4900mah batteries in parallel you could safely discharge:
2 x 196Amps = 392 amps

The capacity of two 40C batteries in parallel would be:
2 x 4900mah= 9.8 amps

If the total capacity of the pack is 9.8 amps and the maximum safe discharge is 392 amps then the C rating for the entire pack would be:

392 amps divided by 9.8 amps = 40C

So the C rating is 40 for the entire pack.

So, to answer your questions. You do not add the C ratings together. The total C rating for batteries in parallel remains the same as each individual cell.



So what about the overall C rating when adding in series?

The capacity of two 40C 4900mah cells in series is:
4900 mah

The maximum safe discharge of the entire pack is:
40x4900mah= 196amps

The total C rating of the entire pack is:
196amps divided by 4900mah= 40C

So we just proved that you don't add the C rating when adding in series either.
 
#47 ·
Seems you've got a typo in your explanation, but I think your conclusion is indeed correct.

You stated that two 4.9 Ah cells rated at 40C in parallel would be able to put out 392 amps safely, yet then stated 196 / 9.8 = 40C , that would actually be 20C, I believe you meant that 392 /9.8 = 40C


want to know if the overall C rating goes up if you hook up two or more batteries in parallel assuming that the batteries have the same specs or does it stay constant?
That's a good questions.

OK, lets assume we have one 40C 4900mah battery.

Tha maximum safe discharge rate for one cell would be:
40 x 4900mah = 196 amps

So if you have two 40C 4900mah batteries in parallel you could safely discharge:
2 x 196Amps = 392 amps

The capacity of two 40C batteries in parallel would be:
2 x 4900mah= 9.8 amps

If the total capacity of the pack is 9.8 amps and the maximum safe discharge is 196 amps then the C rating for the entire pack would be:

196 amps divided by 9.8 amps = 40C

So the C rating is 40 for the entire pack.

So, to answer your questions. You do not add the C ratings together. The total C rating for batteries in parallel remains the same as each individual cell.



So what about the overall C rating when adding in series?

The capacity of two 40C 4900mah cells in series is:
4900 mah

The maximum safe discharge of the entire pack is:
40x4900mah= 196amps

The total C rating of the entire pack is:
196amps divided by 4900mah= 40C

So we just proved that you don't add the C rating when adding in series either.
 
#45 ·
Question...

Does anyone know if SMC gets the soft side Li-Po's from China and put them in the hard shell? ...OR are they fully assembled and labeled in China and SMC just distributes them?

One way SMC knows what is in the pack other way SMC relies on China to get it right...
 
#61 ·
how much to ship one pack? and what recourse do you have if it is bad when you get it?
how much per hour does the japanese worker get?
does he have good benefits?
holidays off?

everything costs money..the consumer must off-set these costs
Same company made both packs, just cut out a few of the middle people. Shipping one pack isn't that much more, just slower.

I'm willing to bet there is only 1-2 companies making all 1s packs, just different labels on the cases.
 
#63 ·
Same company made both packs, just cut out a few of the middle people. Shipping one pack isn't that much more, just slower.

I'm willing to bet there is only 1-2 companies making all 1s packs, just different labels on the cases.
Shipping might not be that much but when importing batteries there is duty and fees involved. We bring in fairly big shipments and we have 8 to 10% in shipping and duty. On a few packs this will be much higher.



I can name you more than 1 or 2 companies than make Lipos for RC.
 
#56 ·
Hi Guys first of all I would like to wish you guys a Happy New Year. Now on to the matter at hand. For those of you who have read what I have said in the past you know we use an exclusive source for our Lipos. This is why the stamping on the cells has SMC on it as they only do these cells for SMC. As new materials and building techniques become available were able to release new packs. This is what happened to the single cell pack.

We were the first company to offer a single cell hardcase pack to the RC market. Our goal was to make this pack the same price as a sub-c pack so we settled on a 4000/25C to keep the price in check. We had left room inside the case to make higher mAh cells when the need occured. Some of our competitors noticed that they could make higher mAh cells and higher C rate so they came out with there own single cell packs. We then worked on a higher mAh and C rate pack and that was the 4900/40C but we only got in a few shipments of these. Then our supplier told me they can now do 50C so we switched to 50C as we had to submit these packs to ROAR and get UN certification done to be able to sell to Horizon and Great Planes. It has become fairly expensive to release new models now with UN certification.

The first sample pack of 50C that I got from our supplier had the same stamp as the 40C packs so I'm not sure if the cell factory didn't think of changing the stamp on the first batch and to be honest I'm not sure if the current batches of 50C have 50C stamped on them as the packs come to us assembled. I will ask these questions to our supplier and figure this out. It's possible some cells got mixed up and if this is the case we need to make sure they pay more attention. Mistakes can happen as 1 month ago we got in 150 packs that had 40C labels on the packs and the barcode was the 50C barcode. We know these packs were 50C as we no longer offer 40C. The only thing we can do is ask our supplier to double check and make sure there is no mistakes on there end.


For those of you who have packs you think you have the wrong packs feel free to test them at 50C to see if they can handle it. You will need to get the proper equipment and use bigger wires to handle the higher amp rates but you will see that our packs can handle 50C.


Were working on a new website which should have allot of valuable info about C rate and how we test our C rate and show the testing results. C rate has gotten out of hand as there is no official standard for C rate or mAh.


Awhile ago we did test a 5000/40C pack from another manufacturer using the same method we test for our C rate and there pack could only do 25C based on our testing method. This company doesn't have the C rate stamped on there cells so I guess they will not get the kind of grief were getting on this site. Guess we need to learn a lesson from this company and no longer stamp or cells.
 
#64 ·
First of all, let me be clear, I'm one of the people who discovered this and if you read my one and only post you will see that I in no way was bashing SMC or making any accusations. The one thing that I wanted was an explanation of what could be the reason for this. As a businessman myself I find it somewhat disconcerting that SMC seems to be focusing their anger at their customers. We are not responsible for the mislabeling.
If you purchased an item with an expectation of a specified value and then discovered that may not be the case. Would you be satisfied? I think not. Granted some people have chosen to pile-on, but this does not change the original problem.
Your solution to have the customer test the packs to determine if they are indeed 50-c is I think somewhat misguided. Why should I have to verify the capacity if their is some doubt. From a customer service standpoint wouldn't it make more sense to replace the item in question and retain a customer or create more ill will. I have not heard this solution as an option.
I will not be commenting anymore about this, but I do hope that whatever the reason was for the problem, customer satisfaction should be the first priority.

Greg Nephew
 
#66 ·
First of all, let me be clear, I'm one of the people who discovered this and if you read my one and only post you will see that I in no way was bashing SMC or making any accusations. The one thing that I wanted was an explanation of what could be the reason for this. As a businessman myself I find it somewhat disconcerting that SMC seems to be focusing their anger at their customers. We are not responsible for the mislabeling.
If you purchased an item with an expectation of a specified value and then discovered that may not be the case. Would you be satisfied? I think not. Granted some people have chosen to pile-on, but this does not change the original problem.
Your solution to have the customer test the packs to determine if they are indeed 50-c is I think somewhat misguided. Why should I have to verify the capacity if their is some doubt. From a customer service standpoint wouldn't it make more sense to replace the item in question and retain a customer or create more ill will. I have not heard this solution as an option.
I will not be commenting anymore about this, but I do hope that whatever the reason was for the problem, customer satisfaction should be the first priority.

Greg Nephew
No one is questioning if you were justified in feeling duped. What I find troubling is that instead of someone contacting us to get answers, they chose to air it out on a public forum. As a businessman, I'm sure you can understand the negative ramifications that can result from this. I don't see how anyone can even debate this point.
This is a hobby to most everyone on this forum. For some reason, many people feel justified in bashing SMC or taking satisfaction when something negative happens. This is not a hobby to us. We take what we do very seriously. I'm sure if a similar situation would arise that shed negative light on your job or something you feel strongly about, you would feel the same way. Of course, nobody thinks of this when they start piling on.
Love us or hate us, we are still here doing what we have been doing for years.
 
#65 ·
Danny IMHO hasn't focused and angry at the customers that I've seen. In fact is seems he is just as bewildered as the final customer. He bought a product to resale and he is a victim just as well. Only he has a name/reputation to protect. How he wants top handle it will greatly reflect on him.

AFAIK NO customer has the capabilty to test at the packs rated C. What if I was to have tested the 40c pack at 50c and it burst into flames assuming nothing else melted, like the wire or Dean's connector. Not safe for the end user to be trying this.

If a batch could be isolated and tracked by serial numbers, then maybe a recall of sorts. But with ability to track by serial number you open a new can of worms. Everyone would be ripping open their packs to check them, also dangerous.

There is not an easy fix that I can think of. I have an idea but it would also info Danny getting cut a break from his supplier because of their mix up if what he has said it true.

But, I have a SMC hard case with a Power Push label covering the molded in lettering. That is a touchy subject for a business person to talk about. I will say this....that pack is my best pack! 5300+ mah @ 35 amp.

Which came first, the chicken or the egg?
 
#68 ·
What am I argueing? Who am I belittling? I admitted that I would be upset if this happened to me. If you are going to attempt to accuse me of something, try to make it legitimate. I have never seen anyone bypass the customer service counter and announce to the store with a bullhorn that a product sucks. Get your analogies straight.
 
#69 ·
ok jack, danny, maybe people could have a little more nice about asking why there packs have the (WRONG C RATING) printed on them.danny if you noticed that the packs where labeled wrong why didnt you fix from the start? jack dont people have a right to get a little angry when they feel duped,you always get angry when someone questions the SMC product,if you wanted to fix the whole deal just replace the packs in question and be done with it.:cool:
 
#71 ·
ok lemme tell you a story...kinda long but if you "read" the entire story when you come to the end you may "get" the moral of the story..

cruise ship carnival legend: went on myhoneymoon on this ship in april..perfect cruise,it couldn't of gotten any better unless the chicks were naked and the jack daniels was free..

same ship 2 weeks later: cruise reviews.....ships water turns orange (no showers) due to swine flu cozumel is out...due to a uproar in isla roatan that island is out..."some" guests go crazy mad trying to fight the captain and the crew...now they call the coast guard to remove a few of the rowdy people..cruise ships floats off the coast of tampa (where it left from) for two days...the worst cruise in history i think..just horrible..2000 passengers and 1000 of them all in the lobby demanding free stuff (cruises included)

those 1000 guests who got up in arms and acted like little kids got nothing from carnival..good bye go away may we never see you back on carnival cruise lines...

1000 of them bit the bullet..went home and contacted carnival corprate...

they all got a 500.00 refund back in cash and a free 7 day cruise on any carnival owned ship in the future....


now i'm not going to say what you guys should have done...but i know what you guys could have done.......

and....i did the same thing you guys did on the novak thread..called them out without a phone call or email......i'm still learning BUT even after i ranted and raved they still took all my novak motors and replaced them all with fresh new motors..i olny had issue with one motor they sent me 5 back.......

now point me to dominos pizza message board so i can attack them for changing there pizza to garbage....
 
#72 ·
...what did my grandma say?..."you can attract more bees with honey than vinagar!" or something like that.

Its very simple. SMC's phone works just fine. If you had a question or an issue, you should have called and i'm sure that the result would have been simular to Bill's cruise story.

I hope that in the future we can avoid all these negative threads. Maybe Hank can intervene and prohibit such threads if there seams that some of the facts are lacking or unclear. It's a real shame to let people rant on and damage the reputations of others without giving the benifit of doubt.

Unfortunately, this forum used to be much more positive and informative in the past. It would be nice to see more threads about helping others than destroying.

Antonio De Nino
 
#73 ·
mr de nino hows it going?

you read my lil story and figured it out! lol

the real problem is most of us never get to meet the guy behind the business..talk with danny for 15 seconds and you know he is a goodfella....

now jack....well the jury is still out on him ahahahahahhahahah
 
#75 ·
As I sit here reading this I had a random thought as to an easy way to possibly calm everybody down, so consider it food for thought.......not fuel for the fire. :p

It sounds like the only reason the "customer" is feeling duped is because his 50c lipo cycles out the same as his 40c lipo does on something like a GFX machine a hobbyist might own.
Since no hobbyist owns equipment to actually test a pack at 50c (Like has been suggested) they use what they have available to them. But (from what I have seen) it is yet to be proven that you can actually measure a difference between a 40c and a 50c pack on the limited loads a GFX or equivalent can put on a pack. Or has it? :confused:

I don't think anyone would really care just how mislabeled their 50c pack is inside if they were somehow reassured they actually received what they thought they had purchased. (I know........it's something that Mr. Obvious would say but bear with me).

So the real question is how can SMC reassure the now gun shy customers that they did get what they ordered?

Would it be as simple as having someone trusted (like Danny @ SMC who actually owns equipment that can test a pack at 40-50c) test both a 40c and a 50c pack on this equipment at say a 40c load and post the numbers to see the differences between the packs. Then cycle the same 2 packs on a GFX (or Equivalent machine that a hobbyist might own) at an equal load like 35 amps and post those numbers.

Then if there was an avg. voltage difference between the packs at 40c discharge but not when using the lighter load of a GFX it could be concluded that the GFX is not enough load to make a call on whether the packs were mislabeled or not. The customer would just have to accept that the pack might actually be a mislabeled 50c pack as they have no way of proving it isn't, and their at home GFX testing does not have any credibility on the issue.

But if there was a measurable avg. voltage difference of these same packs at both 40c and 35 amps then the packs were not mislabeled on the inside but rather on the outside. Thus the customer might be justified in requesting a replacement pack or some sort of future purchase discount agreement from SMC as their at-home GFX testing results actually have some merit.

Does this concept have any believability in helping to discover what was actually sold to the customer or at least create some ideas to help the parties involved come to a common ground? I don't know but it is something to think about. :wave:
 
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