Batteries Newbie Lipo Questions

[mooserider]

*I apologize if this turns up as a double posted. Lost my connection while writing it and partially recovered what I'd written:
-----

Hey folks, haven't posted in a while, but still puttin' along. Been LOVNG a beast biplane I bought... thing is literally amazing. But I also got back into cars... got a new RC 10 kit (b6), and lipos are one of the things I still don't fully 'get', after coming from nitro and nicads.

So here's the deal... i have a Castle, 5700(kv?) motor and esc combo (making this car for speed). The motor/esc says it's rated for 2 or 3 cell. I've been using my Trex 450 batteries (which are 3 cell, 2200 mha, 30c) for the car too.... hey, I have them, right? The car currently does ~45 mph fyi.

So I start looking at batteries to make it go a little faster (I know - dumb), and start to wonder about these batteries. For my heli, I never questioned it... just use a 3 cell, ~30c. For the car, they use a higher c rating for racing...50 -100c. Fine, I buy a 100c, 4600 mha, 2 cell battery ($70!!!). A shorty from Orion to fit in the car. I have NOT used it yet, because it comes in this weird ass state where it has no battery leads or balancer (thought I think I have that figured out now (http://site.petitrc.com/Tech/Nexus_How2ConnectaBalancingCharger2OrionStyleLipoBatteries/Article.htm).

I'm rambling, sorry.... tangible questions:

1. Is there any way to equate c rating for X num cells vs a diff # cells. Like 2 cell with 100c == 3 cell with 75c?
2. Why is it that I can use the SAME battery to spin up my Trex 450 for ~4+ minutes (albeit, only hovering) at ~60% throttle, but the car's esc gets blazing hot ( motor gets hot, but not as much as the esc ). And I'm running the car on pavement, not dirt/offroad. This sort of blows my mind... the battery doesn't get so hot in the heli either. And it's wound up almost constantly. Maybe the canopy on the car is trapping heat or something, whereas the heli it's not.
3. Why make batteries like this (http://www.teamorion.com/carbon-pro-4500-100c-7.4v-shorty-pack-en-2-3.html?sl=EN)? No leads?
4. I typically charge my batteries on 'lipo charge'. There is also a 'lipo balance'. If I do balance, do I have to charge them afterwards also? Do I have to cycle them?

Anyhow, please let me know if you have any thoughts on all this, or if something stands out that I shouldn't be doing. FYI spur is 78, pinion is 19, 21, 24.

BTW, these little biplanes you can buy for ~$150 wo/tx.... they're so, S0 damn fun if you know how to fly! I highly recommend them!

 

[Smoggie]

1. Is there any way to equate c rating for X num cells vs a diff # cells. Like 2 cell with 100c == 3 cell with 75c?

No, these things are totally independant. If you go from a 3S to a 2S battery then your car will be slower. The number of cells equates to voltage (each cell is nominally 3.7V), the higher the voltage then the faster the motor spins. That's where motor kV comes in:

(oversimplifying) Motor RPM = battery voltage x motor kV..

So using a lower voltage battery will make the motor spin slower and the car go slower.

There is no such thing as a 100c battery, this is just marketing BS to trick you into paying more.. sorry! If you really did run a battery at 100C it would go from fully charged to fully drained in 36 seconds! Dont get me wrong, I'm sure they are good batteries but C rating once it gets much over 40C is just made up numbers.

2. Why is it that I can use the SAME battery to spin up my Trex 450 for ~4+ minutes (albeit, only hovering) at ~60% throttle, but the car's esc gets blazing hot ( motor gets hot, but not as much as the esc ). And I'm running the car on pavement, not dirt/offroad. This sort of blows my mind... the battery doesn't get so hot in the heli either. And it's wound up almost constantly. Maybe the canopy on the car is trapping heat or something, whereas the heli it's not.

The battery is just a 'storage tank' full of energy. Think of it like the gas tank on a car. How fast you use up that energy and also how much heat is produced depends on how powerful the motor is that you are running. The motor on your car is obviously drawing a lot more power from the battery than the heli does, so it drains the battery faster and produces more heat. Add to this that the car doesnt have much in the way of cooling air circulation like a heli does from its rotor.

3. Why make batteries like this (Page Not Found No leads?

The link doesnt work, but some hard case car batteries dont have leads, they have sockets into which you plug the leads.

4. I typically charge my batteries on 'lipo charge'. There is also a 'lipo balance'. If I do balance, do I have to charge them afterwards also? Do I have to cycle them?

What charger?... For all modern chargers 'lipo balance' is a balance charge, so that the charger both balances and charges the battery at the same time. You shouldn't cycle LiPos, they have a limited number of cycles in their life so cycling on a charger just wasts those cycles.


Hope this helps.

 

[murankar]

Smoogi pretty much sums it up. Except one thing. Braking I'm your packs. Some will say it does not matter others say it does. The jury is leaning towards break-in.

For the first 5 cycles you can discharge down to 50% and recharge at about 2c rate. Repeat process for 5 cycles. If you decide on doing this discharge should be done on a charger at about 2c rate or done in the vehicle. When cycling with the vehicle do not beat up the packs to much. Keep the discharge amps low and steady.

 

[Smoggie]

Yeah. 'breaking in' is a controversial subject. Evidence supporting it is purely anecdotal. I'd take the opposite view about the 'jury leaning'. I think what does tell the real story though is in the rapidly growing electric power car market where batteries cost $thousands and use the same Li-Ion chemistry as our RC batteries, they dont tell you to do any 'break-in'. Surely if there was any benefit you would be expected to 'break-in' electric car batteries in a similar way to what you had to do with car engines 'back in the day'?

Personally, based on my own experience of many lipos over the years I concluded a while ago that battery break-in is an 'urban myth'. I've never practiced it and I almost invariable get excellent life from my batteries.

Possibly the way I fly (i.e. not very hard) the packs are effectively in 'break in mode' every flight I do, so it's all a moot point?.. who knows? If you want to fly slightly more gentle than normal for a few flights then fine, it cant do any harm. But wasting good battery cycles on the bench is not for me.

Each to their own though, some absolutely swear by break in and have intricate and long winded break-in rituals that they follow religiously.

 

[RandyDSok]

I may have just missed it since I skimmed this before heading to work...

I didn't see anyone mention the relationships of the C rating.... basically it tells you the approx amperage output a set of batteries should be capable of.... ie a 1500mah 20c battery pack 1500 x 20 = 30,000mA or 30A ( 1000 mA = 1A )


The so called "break in" period... actually was a real thing but it wasn't to lengthen the life of the batteries in the way mentioned... When LiPo's just sit on the shelf, they loose their initial storage charge ( ie the nominal voltage of 3.7v ). Since the batteries may sit on the shelves of the warehouse or hobby shop, the manufacturers would often use a stabilizing chemical in the battery mix to extend how long that storage charge would last. The stabilizer would also limit the initial amps out when the customer would use them ... but after several charge/discharge cycles, that stabilizer would be naturally neutralized. There were a varying number of cycles reported by people, usually between 5-10 cycles to complete the process. Later after some battery chemistry tweaks and such... the practice of adding the stabilitizer was dropped by most if not all companies.

So going through the cycles wouldn't extend the life of the batteries... it allowed them to finally reach their full rated C rating once the stabilizer was neutralized. So it was to extend the warehouse storage time that the batteries had available.

 

[Tony]

When I get some time, I will explain where the "break in" comes from.

 

[RandyDSok]

We also missed going over the "over rated" battery ... ie the C rating being exaggerated by the PR folks and listing only it's peak rating when advertising a battery and not the more important constant rating.

Typically this happens when they are quoting the batteries peak amperage rating instead of the constant rating... It's a PR trick basically. The peak rating is important but it shouldn't ever be used as the batteries primary rating. The peak rating indicates what the battery can put out for a brief few moments ( typically just seconds )... the constant rating is how much amperage they can put out continuously for a long period of time.

 

[Smoggie]

The so called "break in" period... actually was a real thing but it wasn't to lengthen the life of the batteries in the way mentioned... When LiPo's just sit on the shelf, they loose their initial storage charge ( ie the nominal voltage of 3.7v ). Since the batteries may sit on the shelves of the warehouse or hobby shop, the manufacturers would often use a stabilizing chemical in the battery mix to extend how long that storage charge would last. The stabilizer would also limit the initial amps out when the customer would use them ... but after several charge/discharge cycles, that stabilizer would be naturally neutralized. There were a varying number of cycles reported by people, usually between 5-10 cycles to complete the process. Later after some battery chemistry tweaks and such... the practice of adding the stabilitizer was dropped by most if not all companies.

So going through the cycles wouldn't extend the life of the batteries... it allowed them to finally reach their full rated C rating once the stabilizer was neutralized. So it was to extend the warehouse storage time that the batteries had available.

yeah, i've heard the 'stabilizer' explanation before but there again I've also read that it's also just an urban myth. It's hard to get a real definitative authoratative source on batteries but batteryuniversity.com is about as good a resource as there is because it's written by genuine professionals in the battery industry. They dont mention it (nor do they mention 'break-in').
From my own testing I've never noticed any decrease in internal resistance over the first few cycles like some claim to see.

 

[murankar]

ProgressiveRC (I forgot his name, David???) Has made mention a few yeas ago that break-in does work. The effect is a decrease (in most cases) in IR which in turn effects the C rating over all. I have also been following the RCHN Battery charts. Most folks who have posted pre and post break-in info are also showing positive effect.

Finally are LiPo and Lith-Ion really an apples to apples comparison? I would not think so because they are different chemistries.

 

[Smoggie]

Finally are LiPo and Lith-Ion really an apples to apples comparison? I would not think so because they are different chemistries.

LiPo and Li-Ion are the same chemistry. The 'Po' in LiPo (at least the LiPos we use) refers to the polymer pouch which is the only real difference (Li-Ion being supplied in metal tubular cases).

Lithium polymer battery - Wikipedia, the free encyclopedia

The second meaning appeared after some manufacturers applied the "polymer" designation to lithium-ion cells contained in a non-rigid pouch format. This is currently the most popular use, in which "polymer" refers more to a "polymer casing" (that is, the soft, external container) rather than a "polymer electrolyte". While the design is usually flat, and lightweight, it is not truly a polymer cell, since the electrolyte is still in liquid form, although it may be "plasticized" or "gelled" through a polymer additive.[6] These cells are sometimes designated as "LiPo"; however, from a technological point of view, they are the same as the ones marketed simply as "Li-ion", since the underlying electrochemistry is the same.[6]

Yes, there are many RC hobby end users who claim that break-in works, but like I said, their evidence is purely anecdotal and not supported by even the most rudimentary objective testing (which would have to use a 'non broken in' set of batteries as a control group), nor by my own personal experience.

There again i cant categorically prove it doesnt work, all I can say for 100% sure is i get excellent life from my batteries without doing it.

 

[murankar]

Break in is not about life span. It's about reducing the IR prior to heavy use. In turn gaining a better C rating. Life span comes from the care of the packs. While cycles do contribute, care and maintenance will also play a role.

 

[Tony]

I would like to see charts of the exact same batteries, from the exact same batch tested. One set on the 'break in' and the other set just put in and flown.

All of this is coming from the old timers out there (like me) that used to have to break in packs to get the best performance out of them.

 

[murankar]

let me see if I can access to the data.

 

[mooserider]

Hey you guys, this is great stuff! Thanks for all the replies... interesting too about the break-in. It's kind of ironic... going to electric from nitro, you still might need a break-in ; ) Sorry for the sporatic replies... been working on a bathroom remodel in the house.

Sorry for the bad link (I think the ')?' at the end of the sentence screwed it up. Here's a different one: Team Orion 2S "Carbon Pro" 100C LiPo Shorty Pack Battery w/4mm Tubes (7.4V/4500mAh) [ORI14066] | Cars & Trucks - AMain Performance Hobbies

I could see it from a brand that's not well known, but even Reedy has one: Reedy Zappers HV 2S Hard Case Li-Po 100C Competition Battery Pack (7.6V/8000mAh) [ASC27302] | Cars & Trucks - AMain Performance Hobbies

But then again, working in the computer industry, I'm well aware of the way advertising twists things around to make them sound better than they are.

I've been doing some reading and I think I get the C rating thing a little more. To me it seemed like if you had a high enough C rating for a 2 cell, it could equate to a lower C rating in a 3 cell. But from what I read, the C rating is basically 'per-cell'? So the overall voltage on a 3 cell is always going to be higher?

I still don't fully get why the heli motor and esc doesn't get as hot on the heli though. Even with the cooling from the rotors... it's constantly cranking at full speed. Those blades are going around at ~6 times a second! The car is just speeding up here and there. Guess I'm gonna have to get a little fan for the car.

Also, the charger I have is this one: http://hitecrcd.com/products/charge...f-80-watt-multi-function-acdc-charger/product
It has Lipo Charge, Lipo Balance, and Lipo Discharge features. So far, I only use Lipo Charge.

Thanks again all!

 

[Smoggie]

Break in is not about life span. It's about reducing the IR prior to heavy use. In turn gaining a better C rating.

Well it depends who you listen to, some certainly claim that it extends life.

As for reducing I.R. like Tony said, where is the test data to support that claim? If I.R. does actually reduce over the first few cycles (which personally I've never observed) then where is the evidence to show that following a 'break-in' process makes it reduce more than just using the batteries normally? There simply is no evidence.
And again if it works to improve battery performance in any way why aren't non-RC users of identical chemistry batteries recommending it? Why do genuine battery professionals such as those behind batteryuniversity.com not even mention it in their guidance about caring for Li-Ion / LiPo batteries?

 

[RandyDSok]

Well it depends who you listen to, some certainly claim that it extends life.

As for reducing I.R. like Tony said, where is the test data to support that claim? If I.R. does actually reduce over the first few cycles (which personally I've never observed) then where is the evidence to show that following a 'break-in' process makes it reduce more than just using the batteries normally? There simply is no evidence.
And again if it works to improve battery performance in any way why aren't non-RC users of identical chemistry batteries recommending it? Why do genuine battery professionals such as those behind batteryuniversity.com not even mention it in their guidance about caring for Li-Ion / LiPo batteries?

You can't ask someone for evidence to prove something... stating that it isn't true... without also requiring the same in return of what you are claiming. When no tests are known to prove or disprove a theory... then each side of an argument must accept that either answer is possible until that evidence and testing is done.

The RC industry is only one of a handful of areas that really stress a battery system ( of any chemistry type )... most do not have the amperage demands that are asked of an RC craft... Full sized electric cars would be another possible area to look at, I'm certain there are others if we'd only think it through.

 

[Smoggie]

I didn't actually say that it wasn't true. What i said was there is no evidence to support it, and in my own experience over the years i've not observed it. I agree, I cant 'prove' it doesnt work. But there again i cant prove that throwing salt over your shoulder to bring good luck is nonsense, or any other superstition isnt true.

It's a accepted principle of science and law that the person who comes up with a theory or claim or accusation has the burden of proof to support it. The burden does not fall on others to prove the propsition wrong: The reversed responsibility response – switching the burden of proof | Science or not?

End of the day it really doesnt matter. if you think that 'break-in' is a good idea do it, they are your batteries.

 

[RandyDSok]

Yeah.. you didn't say it wasn't true... just adamant that you didn't believe it... which is close to the same thing. It was you constantly saying for others to "prove it with evidence" that brought the point I was trying to make out. At some point you must show others respect for their ideas if you expect the same in return. To me constantly asking for that proof meant you didn't show the respect to the other peoples opinions when you also were unable to provide any proof yourself.

I'm also not offended by any of this.... just making a point is all...

 

[mooserider]

Hey you guys, I just went out and flew my biplane again tonight. The little 2 cells that go in are starting to get noticeably 'weaker'. I'm wondering still, should I be charging these on 'lipo balance' instead of 'lipo charge'? Or do you think they're just naturally losing full potential? I've probably used each of these little batteries like 30 times now. Also curious for the rest of my batteries... the larger ones for the car and heli. Sorry to ask again, just not sure.

Thanks!

 

[RandyDSok]

Hey you guys, I just went out and flew my biplane again tonight. The little 2 cells that go in are starting to get noticeably 'weaker'. I'm wondering still, should I be charging these on 'lipo balance' instead of 'lipo charge'? Or do you think they're just naturally losing full potential? I've probably used each of these little batteries like 30 times now. Also curious for the rest of my batteries... the larger ones for the car and heli. Sorry to ask again, just not sure.

Thanks!

Just guessing here... ( not about your question really )...

It may not be that the batteries are getting weaker. I suspect you are probably getting more confident in your flying... and are probably flying a little bit harder than you were at first... and using them up faster since you may be on the throttle a little more than previously.


Now more towards your question...

I do like to keep my batteries balanced... but I don't believe that if they are within a few of tenth's of a volt difference between the cells, that it's going to make a big deal.