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Old 06-09-2019, 08:57 PM
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Quote:
Originally Posted by BarracudaHockey View Post
I use CellPro's to charge all my A123/LiFe packs, they balance charge pretty quickly.
FMA was the first charger to be capable of charging the A123 chemistry battery packs and they are still the best charger for A123's. Hitec chargers have always had issues charging A123's and some other brands do not play well with that chemistry.

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Originally Posted by AHicks View Post
Just my own take, but I've found that when 2 A123 cells don't want to balance normally, one of them is about to take a dump. Watch for a difference in cell voltage. If they no longer match, I would have cause for concern. That pack will not have near the capacity of one that balances easily.
This is not true. The packs get out of balance as we do not use them like they would be used in a cordless power tool where they get run down until the tool quits. The way we use them just doesn't work 'em hard enough so they have to be cycled when the cells get out of balance. I use and old Triton charger for discharge duties, set on the NiCD chemistry, you can pull the packs down to a specified voltage and it will shut off so you do not have to tend the thing. I put the packs on a 3 amp load (that's all the Triton will do) and pull 'em down to 2.5 volts per cell. When the load comes off, they'll bounce back to about 3.0 volts. Recharge and note how many mah's are put in and the cell balance. If the number of mah's put in are looking okay but the balance is still off, discharge them again only this time go down to 2.0 volts per cell, note the total mah's you got out of them. Charge again noting the same figures. If the battery won't come up to at least 80% of capacity, that's when I get rid of them. If the cells are still not balanced, I do that discharge to 2.0 volts per cell a couple of more times. If that does not bring them back into a voltage that is not more than a couple of hundredth's of a volt, that low cell is on it's way out.


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Originally Posted by The Hodge View Post
Off topic, But does the Li-ion cells
work much like the Li-fe / A123
Do not confuse the battery types. While the A123 and the LiFe's share the same chemistry, the LiFe's are NOT the same as A123's. Nor are Li-Ion cells similar to either of the first two, primarily the voltage is higher. Li-Ion's and LiFe's have a self discharge rate that is similar. The A123 can be left fully charged for a year and take less than 100 mah's to top it off. The same cannot be said of the Li-ions or LiFe's.
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Old 06-09-2019, 09:09 PM
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Thanks Zeeb, Yep im aware they are are different make up and different voltages,
what i was getting at is that can we leave them fully charged for long period like Li-Fe with no ill effects.

Sorry should have asked more what i was after.

So Li-ions could be left for a long time fully charged but will self discharged at a fast rate? Or will this cause cell degradation like a lipo?
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Old 06-09-2019, 09:26 PM
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Thanks Zeeb, Yep im aware they are are different make up and different voltages,
what i was getting at is that can we leave them fully charged for long period like Li-Fe with no ill effects.

Sorry should have asked more what i was after.

So Li-ions could be left for a long time fully charged but will self discharged at a fast rate? Or will this cause cell degradation like a lipo?
I would not leave anything but a genuine A123 fully charged for any length of time. LiFe's are more forgiving that Li-Ions, but you have the same issue on the self discharge. On LiPo's, the higher the C rating, the faster the self discharge and the more chance of damage if not left at a "storage" voltage. Li-Ions do not have anywhere near the discharge capabilities of the other two batteries so their self discharge rate is much lower, but it does happen.
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Old 06-09-2019, 09:40 PM
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Thanks for that, Im looking to get some 7.4V Ions for a 35% Model, So i could leave then at any charge capacity for a few weeks or so, If longer ie more than a month then storage charge?
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Old 06-09-2019, 10:26 PM
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Thanks for that, Im looking to get some 7.4V Ions for a 35% Model, So i could leave then at any charge capacity for a few weeks or so, If longer ie more than a month then storage charge?
The battery technology has changed significantly since the Li-Ion chemistry came out. You had your choice of NiCD which could put out a ton of power but the self discharge rate was really something. The environmentalists also hated NiCD batteries so the NiMH came out. Initially, a really good battery but enter the environmentalists again and the chemistry got changed again. That change threw all the peak detecting chargers for a loop. Try to fast charge and they'd false peak leaving you thinking you had a charged battery when they were not fully charged.

LiPo wasn't really an option at that time as they just didn't have enough capacity or discharge capability to make them worth the effort to run voltages that virtually no electronic stuff would tolerate. Li-Ion on the other hand was really safe, could put out quite a bit of power if you got them big enough. It was not unusal to see 5400 mah packs, but it took that much to get the required current. That also had to be run through resistors which were all linear, so the electronics could survive.

Those resistors get hot, as the current flow increased they got hotter and the resistance increased cutting the current flow. Nobody really noticed until Spektrum hit the market. Those battery systems simply could not handle the required current so as the current flow went up, the resistors got hot, the voltage dropped and presto! An rx shut down which while it did happen with 72MHz stuff, they rebooted so fast everyone thought they'd been "hit" buy another flyer.

To make a long story a bit shorter; I used to not really worry too much about my Li-Ion batteries and storing them. I'd just leave them where ever they were at the end of the day and charge them again the night before going flying, they don't like a high charge rate. If I was going to put the models up for the winter or something, Duralite actually produced a small discharger for the purpose of getting to a "storage" charge.
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Old 06-10-2019, 01:09 AM
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Your not wrong it really has changed alot in 15 years of so.

Thank you for your informative write up zeeb
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Old 06-10-2019, 11:35 AM
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Regarding storage of A123 batteries, the mfgr. spec sheets clearly state those batteries can be stored at any state of charge short of full discharge. I have never seen any literature that states how the poly LiFe batteries should be stored. I guess the companies that make those batteries just leave it up to the end-user to decide what’s best. Most of the Li-ion batteries sold by RC vendors are those cells produced for the tool industry and other heavy users. Again like A123 batteries the mfgr. spec sheets state the batteries can be stored in any charge condition short of full discharge. When it comes to batteries, I tend to believe the companies that actually produce the batteries more than what a group of RC users / vendors make up and determine is the best.
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Old 06-10-2019, 12:08 PM
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Yeah I think that is their great advantage, especially for the tool industry, along with low self discharge, good stability/safety, and energy density.

For us, being able to run 2S without regulators or high voltage servos is imho the other big plus.
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