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7.4v Li-ion charging/dis-charging/storing... - 1/16/2013 12:03 AM   
Atlanta 60



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From: Euharlee, GA, USA
Status: offline 		Hi all...

I am new to lithium batteries, most of my previous R/C experience has been with NiCad or NiMh batteries. I now have a few Fromeco 7.4v 2600 Relion Li-ion battery packs in some of my pattern airplanes.

My Questions:
I have three lipo/li-ion capable chargers. I have a Duratrax Onyx 235, Duratrax Ice and a Venom Pro charger. Each of these chargers have a 2 cell Li-Ion setting but the voltage is listed at 7.2v. My understanding is that current Li-Ion technology enables 2cell Li-Ion batteries to be 7.4v (like my Fromeco packs are)

If I switch any of the chargers to the "LiPo" setting I can get (2 cell) 7.4v.

I'm a little lost as what to do...Is it OK to use the LiPo setting to work with my Li-ion batteries?

I've only been using the chargers listed above to discharge the Li-ion packs thusfar, I actually have one other charger specifically made for 7.4v Li-ion packs (made by NMP) and that is what I charge with...


I would also like to know how I should go about handling the batteries for "short term" storage (a week or two). I understand you should discharge the batteries for long term storage (months), but I recently read some folks say not to leave the packs at full charge and always discharge them even short term...

I hope my questions aren't too confusing...

Thanks,

Chuck

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RE: 7.4v Li-ion charging/dis-charging/storing... - 1/16/2013 11:34 PM   
eddieC



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Status: offline 		I always understood Li-Ion cells were 3.6v nominal and Li-Poly were 3.7v, thus 2-cell batteries would be 7.2v and 7.4v respectively. The peak voltages vary accordingly. 
I'd contact the manufacturer and get an explanation. 
I notice my old Triton charger brings my Li-polys to just 4.1v peak. Not a big deal, I take it as a safety measure. 


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RE: 7.4v Li-ion charging/dis-charging/storing... - 1/26/2013 1:29 AM   
CougarRules



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Status: offline 		I would definitely be wary of charging the li-ion using the lipo setting, in fact i personally would not entertain the idea If overheated or overcharged, Li-ion batteries may suffer thermal runaway and cell rupture. In extreme cases this can lead to combustion. Not sure about how long you should leave li ions charged but with lipos 24hrs is the recommended max and some people say less than 12 hours, if you plan to leave them longer they should be discharged to storage voltage.

Like eddieC said i would drop the manufacturer an email and see what they say.

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RE: 7.4v Li-ion charging/dis-charging/storing... - 1/26/2013 3:55 AM   
eddieC



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Status: offline 		Looks like Boeing is caught on the Li-ion learning curve.

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RE: 7.4v Li-ion charging/dis-charging/storing... - 1/26/2013 2:20 PM   
Hoosier06


 

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Status: offline 		I had a friend that bought lithium ions and had this four port charger. When he charged on the lithium ion setting he charged to 7.2 volts as said in an earlier post. He called the place where he bought the Lithium Ions thinking he had a battery problem. The dealer said you can charge the lithium Ion at the lipo setting and get the full 7.4 volt charge. That is exactly what I heard years ago and have charged lithium ions at least 100 times through the years using the lipo setting on my chargers. Several of my flying friends have done the same. We have never had any issues. I cannot give you specific reasons why you can do this. I think the battery chemistry of a lipo and a lithium ion are very similar but will let the experts deal with that explanation. In the end you must choose what makes you comfortable until we hear from an expert on batteries. Just wanted to shre this experience.

On way to know for sure is to call Fromeco who are specialists in selling lithium ions.

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RE: 7.4v Li-ion charging/dis-charging/storing... - 1/31/2013 4:30 AM   
Atlanta 60



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quote:

ORIGINAL: Hoosier06

I had a friend that bought lithium ions and had this four port charger. When he charged on the lithium ion setting he charged to 7.2 volts as said in an earlier post. He called the place where he bought the Lithium Ions thinking he had a battery problem. The dealer said you can charge the lithium Ion at the lipo setting and get the full 7.4 volt charge. That is exactly what I heard years ago and have charged lithium ions at least 100 times through the years using the lipo setting on my chargers. Several of my flying friends have done the same. We have never had any issues. I cannot give you specific reasons why you can do this. I think the battery chemistry of a lipo and a lithium ion are very similar but will let the experts deal with that explanation. In the end you must choose what makes you comfortable until we hear from an expert on batteries. Just wanted to shre this experience.

On way to know for sure is to call Fromeco who are specialists in selling lithium ions.


Thank You!! I did indeed contact Fromeco and that is exactly what they said...Charging on the 7.4v LiPo setting is correct for charging my 2 cell 7.4v li-ion packs...

The 7.2v li-ion setting won't even work with most of my chargers as they detect a "voltage fault" during the "battery check" and won't allow charging to begin...Apparently the 3.6v li-ion cells are older technology, today's li-ion cells are 3.7v per cell....

Most of my chargers have a cut-off feature so when they reach the correct voltage they stop charging. I'm electing to charge at a slower rate than the 1c max.

As far as storage is concerned they told me not to worry too much about dis-charging unless it's going to be a long term storage situation (several months or more)...For dis-charging he recommended a slow 0.5a discharge and not to "hammer them down" at 1.0a...

Thanks to all who responded!!

< Message edited by Atlanta 60 -- 1/31/2013 4:52 AM >

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