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Old Dec 09, 2012, 03:34 PM
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Originally Posted by wjs View Post
In any event, charging at above 1C dramaticly reduces your cycle count and IR of the battery and ends up costing you more and increasing failure points in the pack. I suspect, that most lipo explosions/fires are from repeated abuse of the 1C charge rate.
Care to cite sources for this?

There is wealth of data that is growing daily that demonstrates that the above is absolutely false.
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Old Dec 09, 2012, 03:43 PM
wjs
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Originally Posted by mrforsyth View Post
Care to cite sources for this?

There is wealth of data that is growing daily that demonstrates that the above is absolutely false.
I know. Everyone is lying. It is a vast conspiecy against all the 5C'ers out there. Eyes, faces, and fingers don't get cut in props either. To your question, battery university has googles of data, and reams of other sources we can all google. Your milage may vary.
http://batteryuniversity.com/learn/a...ased_batteries
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Old Dec 09, 2012, 03:53 PM
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Thing is, I have searched and nearly all available information is contrary to the assertion that charging a modern lipoly above 1C is dangerous or 'dramatically reduces cycle count'. Hence the request for studies to help us understand the counterpoint.

It's widely known among the battery community that a good amount of information on battery university is antiquated and in need of refresh, especially as it relates to high output lipolys.
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Old Dec 09, 2012, 04:02 PM
wjs
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Originally Posted by mrforsyth View Post
Thing is, I have searched and nearly all available information is contrary to the assertion that charging a modern lipoly above 1C is dangerous or 'dramatically reduces cycle count'. Hence the request for studies to help us understand the counterpoint.

It's widely known among the battery community that a good amount of information on battery university is antiquated and in need of refresh, especially as it relates to high output lipolys.
Please site those sources. Always open to learning. But if not explicity stated on the bat, then <=1C is what I will use. Even if they post 5-10C in marketing hype, are they going to warranty any/all damage?
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Old Dec 09, 2012, 04:51 PM
I meant to do that
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Thanks for the idea. Those are over $200 though and look to be replacement for starter batteries. They state CCA and not sure it's designed for deep discharge?


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I might concider Shorai LiFEPO4 racing batteries then. Around 10 to 16 charges on one of these. Nice 12v format and light (3-4lbs). Use a normal 12v charger to charge them back up. Almost a perfect solution imho. Various sizes depending on need and wallet. Add more in parallel as you wish.
24mAh
http://www.batterymart.com/p-shorai-...n-battery.html
36mAh
http://www.batterymart.com/p-shorai-...n-battery.html
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Old Dec 09, 2012, 05:39 PM
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Please site those sources. Always open to learning. But if not explicity stated on the bat, then <=1C is what I will use.
Here's hard data from a highly respected expert in battery technology: http://www.rcgroups.com/forums/showp...1&postcount=56

There's no shortage of corroborating data right here in the B&C forum if you desire to learn more.

Honestly, if charging at greater than 1C posed any safety or longevity risk to lipolys, it would be widely known in this forum and the experts that reside here would make it their business to warn and educate.

Mark
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Old Dec 10, 2012, 12:02 AM
wjs
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Originally Posted by newTOpro View Post
Thanks for the idea. Those are over $200 though and look to be replacement for starter batteries. They state CCA and not sure it's designed for deep discharge?
Here is a faq on them. CCA is just a rating. The chemistry is still LiFePO4.
http://www.shoraipower.com/s.nl/it.I/id.5/.f

Have some interesting advantages. The primary pro is weight. You can move it around easily if you need. If you don't care about that, then a cheap LA deep cycle with best capacity may be way to go.
• Up to 80% lighter than conventional lead-acid starting battery
• Up to 2000 cycles - up to 8 times longer cycle life
- No lead, no acid, no gasses, and do not sulfate
• No maintenance - store up to 1 year without recharge
• Environmentally safe - no harmful gas or acid leaks and spills
• Typical design life of 5 years
• Recharge using conventional lead-acid battery chargers*
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Old Dec 10, 2012, 10:04 AM
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I know. Everyone is lying. It is a vast conspiecy against all the 5C'ers out there. Eyes, faces, and fingers don't get cut in props either. To your question, battery university has googles of data, and reams of other sources we can all google. Your milage may vary.
http://batteryuniversity.com/learn/a...ased_batteries
Did you read the link you provided?

I found the explanation below on Battery University using the link you provided and found it enlightening.

"The author of this essay does not depend on the manufacturer’s specifications alone but also listens to user comments. BatteryUniversity.comis an excellent sounding board to connect with the public and learn about reality. This approach might be unscientific, but it is genuine. When the critical mass speaks, the manufacturers listen. The voice of the multitude is in some ways stronger than laboratory tests performed in sheltered environments."

So does Battery University actually conduct any of their own independent testing or do they just use the unscientific data they collect from user comments?
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Old Dec 10, 2012, 11:49 AM
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Battery University is a good general info source site and I have posted links to it numerious times. Thier LiPoly data is aimed at consumer electronics not RC applications and thus much of it does not apply. Our LiPolys do not have fuel gagues built in which requires the LiPoly to be discharged to empty so the gage can reset and be accurate. Our aircraft do not have the LiP9lys build in with on board battery management devices and our chargers are a bit more complicated than a simple 5V DC power supply such a used in most Li powered consumer devices.

BU is a sounding forum for Camdex which makes chargers / test equipment for batteries of commerical flavor

http://www.cadex.com/prod_test/overv...paign=BatteryU

Charles
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Old Dec 10, 2012, 12:25 PM
wjs
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Did you read the link you provided?

I found the explanation below on Battery University using the link you provided and found it enlightening.

"The author of this essay does not depend on the manufacturer’s specifications alone but also listens to user comments. BatteryUniversity.comis an excellent sounding board to connect with the public and learn about reality. This approach might be unscientific, but it is genuine. When the critical mass speaks, the manufacturers listen. The voice of the multitude is in some ways stronger than laboratory tests performed in sheltered environments."

So does Battery University actually conduct any of their own independent testing or do they just use the unscientific data they collect from user comments?
I have heard some mfgs don't even conduct their own testing in terms of C rating or is sort of a sketchy process. They may have different or special ways they magically create a C rating. A lower C from one could match a higher C from another depending on internal calcs.
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Old Jan 12, 2013, 08:28 AM
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Hopefully this wasn't already covered (I didn't read through every post) but a question regarding deep cycle batteries. I've been using a 110AH deep cycle battery that I bought about 5 years ago. I'm currently building a model that will use a 6S 5000mah pack and I also have a Swift helicopter using a 6S 4000mah pack

Charging both 6S packs plus my other smaller packs several times at the field will seriously over tax my deep cycle battery so I'm planning on using 2 batteries in parallel. Can I connect my old battery to a brand new battery or should I just get 2 new ones so they're matched?



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Old Jan 12, 2013, 12:20 PM
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Originally Posted by MikeCr View Post
Hopefully this wasn't already covered (I didn't read through every post) but a question regarding deep cycle batteries. I've been using a 110AH deep cycle battery that I bought about 5 years ago. I'm currently building a model that will use a 6S 5000mah pack and I also have a Swift helicopter using a 6S 4000mah pack

Charging both 6S packs plus my other smaller packs several times at the field will seriously over tax my deep cycle battery so I'm planning on using 2 batteries in parallel. Can I connect my old battery to a brand new battery or should I just get 2 new ones so they're matched?



Mike
Since you are charging 6S packs, have you thought about going 24V on your charger? I think that if you wire them in series, there will be less problems with miss matched batteries. Ideally you probably want them matched anyway.
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Old Jan 12, 2013, 12:33 PM
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Since you are charging 6S packs, have you thought about going 24V on your charger? I think that if you wire them in series, there will be less problems with miss matched batteries. Ideally you probably want them matched anyway.
I can never keep this straight. I agree going to 24v on the charger would be more ideal. But isn't putting them in parallel going to keep them both at the same voltage and avoid over discharging one of them which would happen if they were in series?
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Old Jan 12, 2013, 01:17 PM
wjs
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I can never keep this straight. I agree going to 24v on the charger would be more ideal. But isn't putting them in parallel going to keep them both at the same voltage and avoid over discharging one of them which would happen if they were in series?
Parallel will give you capacity of both at 12v. Series will give capacity of one, but at 24v. Unless you really need it, I will stay with 12v. The best way would be to charge both seperately when they need charging. You could overcharge one if you try to charge in parallel. As long as they stay ~close, you should not have too much issue running one down too much as long as both same capicity. Leave input cutoff V a bit higher on lipo charger to account for error and not drain one too much.
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Old Jan 12, 2013, 01:18 PM
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Since you are charging 6S packs, have you thought about going 24V on your charger? I think that if you wire them in series, there will be less problems with miss matched batteries. Ideally you probably want them matched anyway.
I suppose I could go 24V to the charger. My current chargers won't handle it but I plan on buying some new ones. A PowerLab PL6 and another as yet to be decided for the smaller packs. My current chargers, with the exception of a PZ one that came with my Extra 300, are not balance chargers and are very old technology anyway. If I go with a 24V setup I'd need to connect the PZ charger directly to one of the 12V batteries. In order to get the max capabilities out of the PL6 I'd have to feed it with more than 12V but I don't see needing to push it that far at present.

I'm an electronics technician so my understanding about such things is certainly better than most but my concern is with regard to either series or parallel connecting 2 batteries that have different characteristics. A new battery and an old battery, batteries or different capacities, internal resistances, etc. If I went with 2 identical new batteries I'm sure it would work either way.


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