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Old Mar 24, 2012, 08:27 PM
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Bradenton, Florida
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Discharging packs to storage voltage

First let me say this is not an original idea. I got it from RarR but think it should be shared.

I'm sure all of us have at one time or another charged a bunch of packs and had weather or some other force stop us frim discharging them in our models. Most of us know that leaving a pack fully charged for a long period of time is as bad for them as leaving them fully discharged and really shortens the life span.
Those that have used a charger to discharge packs know how long that can take with the 1 amp load that most chargers will put on a battery.
I've had the stuff to build this for a while now courtesy of Chris (osprey21) who works at an electrical supply company. That's where the 100 watt 24v dc bulbs and fixtures came from. Since the weather tomorrow is looking kinda "iffy" and I have enough packs charged for several boats a couple of heats each decided it was time to put it together "just in case".

Pretty simple project really. All I did was mount the fixtures on a piece of scrap ply and hook them up in parallel. That in turn hooks to a watt meter and the pack to be discharged.
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Old Mar 24, 2012, 09:17 PM
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Canada, ON, Whitby
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I've got something similar from my truck racing days, it's made using 12v car bulbs in parallel (10 of them). Definitely works well. Back then it was all nicad packs, so I just left the packs plugged in until the lights were almost right out, but the wattmeter definitely makes it much safe with lipo packs.
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Old Mar 24, 2012, 11:06 PM
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Wow...................9.9 amps! Even my biggest chargers only discharge at like 1.5 amps.............. That would drag em down pretty quick i would think. Great idea.
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Old Mar 25, 2012, 04:06 AM
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Good to see you got it assembled. Did you get the watt meter off eBay?
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Old Mar 25, 2012, 05:43 AM
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What is the best storage voltage? Sorry, too lazy to search it
I currently charge my packs to between 4.08 and 4.10 volts. Its almost full but its better than leaving them at 100% capacity.
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Old Mar 25, 2012, 06:06 AM
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Bradenton, Florida
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Quote:
Originally Posted by osprey21 View Post
Good to see you got it assembled. Did you get the watt meter off eBay?
That meter is one that I've had for years. It's part of an old Medusa power analyzer set that I bought in the FSW area here on RCG. It hasn't seen a lot of use since getting more involved in boats than planes. Now I have a boating related use for it.
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Old Mar 25, 2012, 06:08 AM
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Bradenton, Florida
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Quote:
Originally Posted by SARCFAN View Post
What is the best storage voltage? Sorry, too lazy to search it
I currently charge my packs to between 4.08 and 4.10 volts. Its almost full but its better than leaving them at 100% capacity.
Around 3.80 - 3.85v per cell is considered ideal.
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Old Mar 25, 2012, 06:56 AM
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I must write this down, seems a mental note just don't work with me.
Thank you.
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Old Mar 26, 2012, 05:54 AM
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Bradenton, Florida
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Quote:
Originally Posted by scorpion1 View Post
Wow...................9.9 amps! Even my biggest chargers only discharge at like 1.5 amps.............. That would drag em down pretty quick i would think. Great idea.
I used it on a couple of packs I didn't run yesterday. With only 2 bulbs in it will pull a fully charged 5000 ma pack down to storage level in about 15 mnutes.
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Old Mar 26, 2012, 05:17 PM
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Palma Sola,Fla.
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Quote:
Originally Posted by bill34207 View Post
I used it on a couple of packs I didn't run yesterday. With only 2 bulbs in it will pull a fully charged 5000 ma pack down to storage level in about 15 minutes.
15 minutes!

I need to get busy and put one together, I mean it's not like I don't have the materials.
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Old Mar 26, 2012, 05:36 PM
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how long can you leave them fully charged for without damage ?
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Old Mar 26, 2012, 06:12 PM
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Bradenton, Florida
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Quote:
Originally Posted by osprey21 View Post
15 minutes!

I need to get busy and put one together, I mean it's not like I don't have the materials.
The 24 volt bulbs survived the 6s packs. It usually takes about 2 hours + to pull one of them down with my accucel 8.
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Old Mar 26, 2012, 06:14 PM
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Quote:
Originally Posted by madphil View Post
how long can you leave them fully charged for without damage ?
I usually put mine into storage mode at the end of a days running. I know of at least one person who had some nano techs puff after being left fully charged for only 3 days.
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Old Mar 26, 2012, 06:39 PM
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Palma Sola,Fla.
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Quote:
Originally Posted by bill34207 View Post
The 24 volt bulbs survived the 6s packs.
I recall you expressing some concern yesterday, so that's good to know.
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Old Mar 27, 2012, 02:53 AM
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United States, FL
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Quote:
Originally Posted by bill34207 View Post
The 24 volt bulbs survived the 6s packs. It usually takes about 2 hours + to pull one of them down with my accucel 8.
Excellent! I was afraid to try that one!
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