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Old Apr 30, 2012, 07:17 PM
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The importance of storage charging a LifePo4

I just bought a Zippy 2s/6.6V/8400MAH battery to replace a sealed lead acid 6V/6A batt in a hi powerd search light,this devise is something that sits around quite a while with infrequent use,at storage charge it should be close to 5-6A which is close to the OEM batt fully charged and am thinking of keeping it this way unless the light is going to do heavy work in this case a full balance charge,i am mostly a LiPo guy,but what i've read this chemistry seems to fit the bill of this application better than a PB.What's your opinion gentlemen
P.S i have an I Charger 106 b and a 23A PS.
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Old Apr 30, 2012, 08:44 PM
Southern Pride
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Good luck with that battery as they do not have a great reputation like the real A123 Systems / Racing LiFePO4 cells do.

With the real (original) A123s storage is something few of us fooled with. I keep ones very infrequently yused at storage but others have been fully charged for over 5 years and still perform great.


Charles
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Old Apr 30, 2012, 09:20 PM
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I don't doubt you for a minute knowing it comes from HK,but it's the only batt i could find with the correct dimensions to fit the compartment and decent umph as per MAH.Only EP Buddy had something similar at 4500mah i think for more money so i'll have a go with this as i did'nt want to spend lots on a light that sits most of the time,but it's one nice tool when you need it,thats why i figured the LiFe would be better in holding a charge while sitting around with a longer life span than the OEM, while keeping it at storage level can't hurt can it.That's all provided it's not DOA knowing them i've had a couple.
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Old May 01, 2012, 05:43 AM
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The zippy 2S Life receiver packs from HK work very well. I've had 5 or 6 of them in service for a year amd still going strong.
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Old May 01, 2012, 07:30 AM
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I also note that my I Charger when in storage charge wants to take a LiPo somewhere close to 3.85v give or take a bit or try to be accurate for lack of better words.When storing my only Tx LiFe it's very casual never ending at the same voltage as if it just says lets take some juice out of this sucker and quit while achieving the process fairly quickly.Could it be that the LiFe storage voltage is much wider and easy to achive.
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Old May 01, 2012, 07:55 AM
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Quote:
Originally Posted by The Tug View Post
.Could it be that the LiFe storage voltage is much wider and easy to achive.
It is more likely that the discharge curve of LiFe cells being so flat that the actual capacity remaining is widely variable thus the recovery voltage varies.
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Old May 01, 2012, 10:38 AM
Southern Pride
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Quote:
Originally Posted by seefest View Post
The zippy 2S Life receiver packs from HK work very well. I've had 5 or 6 of them in service for a year amd still going strong.
I have read good reports on those however the simple facts are that a receiver battery does not have a 3C or greater load on it and most charge them more often that once a year.

I have real A123 System / Racing LiFePO4 2300 mAh cells in a Husky spot lite which pulls 6Amps, on high power. The factory 6V 3Ah was always needing a charge and after insatlling the 2S LiFePO4 battery in it it gets charged perhaps once a year (toped off ) or after being used a fair amount. I just checked it and 6.2 volts no load and 5.7 at 6A ,last charged over 6 months ago.

I also have the real A123s in my cordeless drill motor, trim saw ,several flast lights, weed eater, as starting batteries in my 16 HP zero turn law mower part of my alarm system and they give excellent service in all of these applications.

I have a 2S 2300 A123 receier battery I assembled over 4 years ago in my Sig Fazer converted to electric and I have topped it of after setting in my shop for over a years and it only required 20 mAh .

Several here on RC Groups have tried the larger LiFePO4 batteries from HK in applications where they only saw moderate loads and they performed very poorly.


Charles
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Old May 01, 2012, 02:15 PM
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I dont belive in storage charge. I have never heard a good explanation why it should be beneficial.

I use my batteries, both A123 2300 mah and Turnigy 4500 mah as starter batteries for my bikes. Works perfect, and has done for a few years.

One bike was put away in september, and just pulled out of the garage today. Started right up with great power on the battery.
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Old May 01, 2012, 02:21 PM
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The higher the state of charge the higher the state of chemical reactions are in the cells. Lower charge state and cooler and chemical reactions are slowed down.

Only Pb batteries do best when mainted at full stste of charge.

I have A123s which have done well fully charged at room and shop temp. for close to 6 years however the ones at Storage are in better condition and the ones at Storage voltage and stored at 45F except when being flown are in much better condition.

One has to weigh convience with expected overall performance and life.

http://batteryuniversity.com/learn/a...ased_batteries

Charles
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Old May 01, 2012, 02:32 PM
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Originally Posted by everydayflyer View Post
The higher the state of charge the higher the state of chemical reactions are in the cells. Lower charge state and cooler and chemical reactions are slowed down.
Yes i know, but is there a reaction in the batteries that causes them to loose capasity, plate the anode/cathode or similar?

Anyway, as you say it is probably a benefit/convience question.
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Old May 03, 2012, 11:04 AM
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I am in the hope that this battery can deliver 6 amps,as it's a 8,400mah battery rated at 30C,i would be rather dissapointed if it could'nt that rating is alot of bloody amps.
P.S i was quoting Charles.Post#7
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Old May 03, 2012, 06:59 PM
Jack
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You got good and you got cheap. And the two are usually self exclusive.

The Zippy 2S2P pack is
146mm x 35mm x 52mm
2S2P / 6.6 V
219g
8400 mAh

You can buy 8 brand new A123 26650 2300 mAh cells on eBay for about $65 shipped.

If you arranged the 8 2300 mAh cells into a 2S4P it would give you a 9200 mAh pack that weighs about 620 grams or so. With A123 if you want the quality you have to be able to live with the weight and bulk.

You can see what a 2S3P would look like at this link (they don't do 2S4P), just imagine another pair of cells on top:

http://scriptasylum.com/rc_speed/lipo.html

Each 26650 cell is 26mm Dia. and 65mm Long and weighs 76 grams. They could be arranged as below to produce packs that might work for you as far as storage space:

two flat fours

| | | |
| | | |

Approximate size: 130 x 104 x 26

two standing fours

oooo
oooo

Approximate size: 52 x 104 x 65

Add a little to the pack sizes to allow for inter pack wiring and heat shrink covering.

The packs could be charged as four in parallel, I'm a little worrisome about charging so I'd probably put four 2S balancing connectors on the pack so I could monitor/charge every cell individually if I ever had to. For most purposes, I would charged the pack via the battery connector and just check the balance.

The packs could be charged to 3.6-3.85V per cell and would be rested down to about 3.4V per cell soon after charge was finished (within an hour). That would give you a 6.8V pack for a starting voltage and would be usable down to 2.0V or so if you wanted to take it that low.

The A123 pack would certainly be up to the 6A load and long storage/intermittent usage between recharges. It would give you about 84 minutes of continuous light on time with a 6A load

The HK pack is the clear winner on economics, for what that is worth...

Jack
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Old May 04, 2012, 09:37 AM
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Thank you Jack for a very informative reply.It is what it is as it's in the mail if it don't last i shall go for the A123 cells it's quite a nice light,what bit me with this pack is it will fit into the compartment neatly however it is longer,after soldering it up i am going to put some sort of padding for protection and duct tape the sucker up with the charge and balance leads outside,it wont win a beauty contest but it will work.In hindsight i should have come on here first and done that i am quite capable of making up a pack even 6 cells would have put it over the capacity of the 6A lead acid the compartment is 52x52x100 mm i'll bet i could have hacked it to get the door back on .Thanks Peter
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Old May 04, 2012, 12:16 PM
Jack
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You're more than welcome.

Charles is the guy that got me going on these A123 cells and I've never recovered from it and am still using them.

I still fly some 4S A123 packs with the 18650 1100 mAh cells and have some 4S and 5S 2300 mAh packs that have outlived their planes and are waiting for me to build another one. I stocked up on 18650 and 26650 cells when they were cheap (less than $4 a cell) and probably have a lifetime supply now.

Now the 18650's are showing up on eBay cheap ($3 a cell or so) and in big numbers too. So anyone that needs bullet proof 6V or so packs should look into them.

Thanks again Charles!

Jack
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Old May 04, 2012, 12:35 PM
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On a similar note not to start another thread i also have a pair of Bushnell Stableview binocks,the gyroscope uses 2 AA alkaline batts Bushnell did'nt seem to think using Nimh batts were a good idea because of the lower voltage 1.2 v1.5.I'm wondering if a single A123 could work but now i've gone over voltage 3.3v nominal before charge.Has anybody got a brilliant idea this thing can suck some juice and the alkalines are expensive here.
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