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Old 06-20-2006, 08:23 AM   #721
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I was under the impression a lot of the saddle pack issue was they just couldnt fit the cells into the configuration and still have all the safety features, etc. Plus they may have been trying to hit a certain price point and having the saddle packs would (I would assume) raise the price.
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Old 06-20-2006, 09:17 AM   #722
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I'm reading how you dont need to peak the packs and that some are running 2 runs before charging. And some charge them a week before use....

Perhaps someone could explain what goes on when these things charge.

For example we peak a 7.2v nihm before a run because they often peak above 9volts and that results in first or second lap boost in performance...

With the lipos do they not peak higher then 7.4volts? Wouldn't a fresh off the charger pack perform better then a pack that was charged and sat for a few yours or days in some cases?

I know that no one is using up the 4800mah in there runs but for most racers especially in stock we care mostly about the first 5 minutes worth of the back not the last 15minutes... So if you can start the 4800mah lipo at 8volts off the charger vs 7.4 after sitting wouldn't that be the best way to go..

Fast forward 2 years and everyone is racing with these batts, do u honestly think you'll want to run back to back runs without peaking or recharging?

ps not flaming just looking for info

Does anyone have a discharge curve that we could use to compare to nihm cells? at 30 amps? peaked vs not peaked?
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Old 06-20-2006, 09:28 AM   #723
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LiPo packs don't "peak" the way NiMH cells do. Which is why you can't use NiMH chargers. The voltage doesn't keep increasing then drop down. Also, NiMH cells have high self-discharge rates, which is why a fresh packs performs better. LiPo is not the same.
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Old 06-20-2006, 09:37 AM   #724
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Quote:
Originally Posted by XrayFK
LiPo packs don't "peak" the way NiMH cells do. Which is why you can't use NiMH chargers. The voltage doesn't keep increasing then drop down. Also, NiMH cells have high self-discharge rates, which is why a fresh packs performs better. LiPo is not the same.
Yes. LiPo is a completely different technology, so we're taking all the "do's-and-dont's" rules we currently use on our batteries and toss them all out the window. Most battery performance and maintenance tricks do not apply to Lipo. (That's how I understand it at least... )
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Old 06-20-2006, 09:39 AM   #725
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ya i realize there is a difference... I understand the nihm side of things but for lipo i dont. Are lipos at 7.4 volts at peak? What voltage are they at when they have dumped? How does a lipo charge detect a fully charged pack?

I guess once the matched lipos come out and CE comes out with a TURBO LIPO charger we can see discharge and charge data.
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Old 06-20-2006, 10:02 AM   #726
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Quote:
Originally Posted by Joel Lagace
ya i realize there is a difference... I understand the nihm side of things but for lipo i dont. Are lipos at 7.4 volts at peak? What voltage are they at when they have dumped? How does a lipo charge detect a fully charged pack?

I guess once the matched lipos come out and CE comes out with a TURBO LIPO charger we can see discharge and charge data.
I probably shouldn't try and answer these questions as I'm still learning about these things as well, but I know almost all your answers are in this thread, as I've seen the answers to your questions. I'd recommend doing a search for Rick Howart's posts. He's been very good at providing information.

I can say that these packs never should be "dumped". As I understand it is dangerous to let them drop below 6v. Things go boom.
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Old 06-20-2006, 10:20 AM   #727
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I wouldn't say to throw eveything about batteries out the windows. LiPo cells are just as easily damaged by heat, overcharging, and too low voltage as the current NiMH cells are. LiPo packs also need to be balanced, like NiMH cells need to be equalized for best charge. Also, I am sure matchers will figure out how to "match" LiPo cells as well.

Joel, you don't want LiPo to go below 2.75-3v/cell. LiPo chargers use a technique called constant current/constant voltage to charge packs. LiPo cells also have a maximum safe voltage, between 4.1-4.2v. CC/CV charge delivers a constant current until the battery reaches a specified voltage (~ 4.1-4.2 v/cell) and then a constant voltage charge until the cell voltage is in equilibrium with the charger output voltage. It's like diode-resistor discharge trays, only with charging. The closer the battery gets to the end, the lower the current. The charger stops charging once the current becomes low. I would guess around .1A is the cutoff.

Hope this helps. If I messed any information up, someone please correct me
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Old 06-20-2006, 10:41 AM   #728
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-Its true that Lipo have to be balance, but its FAR from being "like NiMH cells".

Lipo may need to be balanced once or twice a year IF you use them a lot. Thats a far cry from the 'before every charge' routine we have to follow with NiMH cells.

-Its true that Lipo can be damaged by heat just like NiMH cells, but unlike those cells, the Lipo is not generating its own danger. NiMH get hot...they get hot during charging, they get hot during discharging, they get hot during normal use. With Lipo, the pack get barely above body temp even when used outside in high heat. Which means that the risk of heat damage has to come from somewhere else. Like charging on the wrong setting or leaving it in your car...in the midwest...in August.
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Old 06-20-2006, 11:04 AM   #729
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yes, this is true. I was being to general when I mentioned earlier that we can toss ALL the rules out the window.

Some of the things we'll have to still pay attention to, but alot of the things we do simply to keep from destroying the cells will no longer have to be done.
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Old 06-20-2006, 05:54 PM   #730
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Thanks that was good info, makes alot of sence. So basically lipos are alot more liniar then nihms when it comes to charging. The voltage is much more constant during charging. So "JITTING" them with big amps wont result in exta punch as the nihms give out... At least at this point..

So now how about a discharge curve?
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Old 06-20-2006, 06:00 PM   #731
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7.4 all the way. so using the pack in 1st or 2nd heat running electric stock without repeaking will give you the same output.
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Old 06-26-2006, 02:47 AM   #732
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Default Balancing?

Hello,

I am new to the forum and have a technical question. I hope this is the right place to ask?

Since the Platinum LiPo has a port for balancing but I don't have a balancer I was actually wondering if I could use this balancing-port for charging the cells individually. This should do the same as using a balancer, shouldn't it?

Any help or idea will be appreciated.

Thanks!

P.S.: Great forum with a lot of useful information!
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Old 06-26-2006, 02:58 AM   #733
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Quote:
Originally Posted by naCER
Hello,

I am new to the forum and have a technical question. I hope this is the right place to ask?

Since the Platinum LiPo has a port for balancing but I don't have a balancer I was actually wondering if I could use this balancing-port for charging the cells individually. This should do the same as using a balancer, shouldn't it?

Any help or idea will be appreciated.

Thanks!

P.S.: Great forum with a lot of useful information!
The Orion Lipo pack does not need balancing like normal cells (I have never balanced mine) so I would worry about it too much.
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Old 06-26-2006, 07:19 AM   #734
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Quote:
Originally Posted by naCER
Hello,

I am new to the forum and have a technical question. I hope this is the right place to ask?

Since the Platinum LiPo has a port for balancing but I don't have a balancer I was actually wondering if I could use this balancing-port for charging the cells individually. This should do the same as using a balancer, shouldn't it?

Any help or idea will be appreciated.

Thanks!

P.S.: Great forum with a lot of useful information!
And you can if you would like, look back a few pages and it is explained, but you will need to get a connector to fit in that balancing port...
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Old 06-26-2006, 10:35 AM   #735
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Raced my new Lipo at my local track last weekend for the first time. No othere electrics wanted to run Mod so i asked to run in Nitro Mod instead. Im running a GTB and velociti 5.5. Its also not that large of a track. Any how came second in to of the 5 min qual's then won the 10 min main by more than a lap. After the race i recharged my battery at it took 4300 MaH. Needless to say im not going back to my NiMh packs except for big races.
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