how long does the charge last in A123 cells if not used ?  
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All Forums >> Radios, Batteries, Clubhouse and more >> Batteries & Chargers >> A123Racing Support >> how long does the charge last in A123 cells if not used ?
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how long does the charge last in A123 cells if not used ? - 1/2/2008 5:05:03 AM   
747



Posts: 252
Joined: 9/14/2003
From: Downingtown, PA, USA
Status: offline 		I made my own 5 cell A123 pack from Devalt. Its been 2 months since I made it but still shows 16.4 v total since it hasnt been used.

My question is how long does the charge last in A123 cells if not discharged / used up? Whats the safest lower voltage per cell below which it needs a recharge?

Also where can I get a big enough heat shrink for that, can I use a hair dryer to shrink it? I dont have a heat gun

Thanks
747.

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RE: how long does the charge last in A123 cells if not... - 1/2/2008 3:50:11 PM   
everydayflyer



Posts: 893
Joined: 8/21/2005
From: Buchanan, GA, USA
Status: offline 		Charged to 3.6 per cell they settle down to approx. 3.45 per cell fairly quickly and then self discharge much slower. I have had them still above 3.40 after setting for a couple of months or more but I tend to charge mine to around 3.8 per cell.

A123 Racing recommends 2.0 as min. volts per cell LVC . In that all DeWalt / A123 Racing / B&D VPX cells seem to be charged to 3.3 volts per cell at the time of manufacturing I would assume that this is an ideal storage voltage.


Heat shrink size would depend on pack configuration of which there are many possible combinations.


105 mm will fit.

00
00


and a good hair dryer should work OK.


I purchase my pack building supplies from

Cheap Battery Packs . Com

Charles

< Message edited by everydayflyer -- 1/2/2008 3:51:33 PM >

(in reply to 747)
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RE: how long does the charge last in A123 cells if not... - 1/3/2008 1:41:36 AM   
747



Posts: 252
Joined: 9/14/2003
From: Downingtown, PA, USA
Status: offline 		Thanks ! Do I have to balance the 5S pack ? Some say:" it is not necessary[ for A123] to get a balancer, just get the charger". Do you balance your pack?

Also once I wrap it , can I stuff the gaps to fit the pack securely with foam in the plane. My worry is what if it heats up will it be hot enough for it to melt the foam pads?



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RE: how long does the charge last in A123 cells if not... - 1/3/2008 1:57:11 AM   
everydayflyer



Posts: 893
Joined: 8/21/2005
From: Buchanan, GA, USA
Status: offline 		I balance or at least check balance often. It gives me peace of mind and I have had non balanced packs to hit LVC a lot earlier than normal.

Most secure batteries with velcro and a velcro strap. Depending on temperature often ventilation / cooling is needed. I do not fly when it is below 25F so have little advise for snow bitrds.

Charles

(in reply to 747)
       Post #: 4

RE: how long does the charge last in A123 cells if not... - 1/3/2008 2:08:47 AM   
747



Posts: 252
Joined: 9/14/2003
From: Downingtown, PA, USA
Status: offline 		Has your a123 pack been heated up or just warm to touch(ever) even when flying in full power for long?

Also, I can understand velcro use at the fuselage floor , but how do people use velcro straps or releasable ties? Do they drill 2 holes in the bottom to secure the pack - coz it needs something to go around right?

Do you keep your a123 always in the plane or take it out - I plan to keep it in the plane itself , is it ok?!

tks...

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RE: how long does the charge last in A123 cells if not... - 1/3/2008 2:58:00 AM   
everydayflyer



Posts: 893
Joined: 8/21/2005
From: Buchanan, GA, USA
Status: offline 		Firt off I do not fly wide open for long. Most of my aircraft have between 200 and 300 watts per pound.
Yes it is normal for the battery to reach 30 F more than ambient temp. even with good ventilation.

Velcro on the battery and battery support with a velcro strap around the support and battery.

Battery stays in my MUS Mini Ultra Stick but they come out of all the rest.

Charles

(in reply to 747)
       Post #: 6

RE: how long does the charge last in A123 cells if not... - 1/24/2008 2:51:11 AM   
cwharper


 

Posts: 219
Joined: 2/18/2007
From: Ocilla, GA, USA
Status: offline 		Back to the original question, my two 12s1p packs sat for three months fully charged. I checked on them a couple of weeks ago and only put in 10mah each to top off for flight.

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(in reply to everydayflyer)
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RE: how long does the charge last in A123 cells if not... - 1/24/2008 9:51:47 PM   
everydayflyer



Posts: 893
Joined: 8/21/2005
From: Buchanan, GA, USA
Status: offline 		Along the same line I have read reports that some seem to think that the DeWalt pack may discharge some cells if left setting long enough. I have a DeWalt pack( unopened) which was 33 volts when I received it two months ago and it still reads 33 volts. I have flown packs which have set for well over a month and have noticed no difference in their performance.

Charles

< Message edited by everydayflyer -- 1/24/2008 9:52:16 PM >

(in reply to cwharper)
       Post #: 8

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All Forums >> Radios, Batteries, Clubhouse and more >> Batteries & Chargers >> A123Racing Support >> how long does the charge last in A123 cells if not used ?
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