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LiFe A123

Info on voltages

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Gary Murphy 121/09/2019 23:17:04
378 forum posts
14 photos

There as been some posts recently on A123 LiFe cells.

I tried these a while ago for RX packs, 2 cell was ideal size and weight. I gave up because of the variation in voltages.

The cell says 3.7v, My multi chem charger will charge to 3.6v. A dedicated charger just for the A123 cell will charge to 4.1v. So what should the cell be charged to?

Then discharge, I read the cells can not be damaged by over discharge and will suddenly drop to 2v with little warning.

They are great in my cordless drills BUT was to wary for model use.

This was a few years back.

Martin Harris22/09/2019 00:52:13
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8793 forum posts
215 photos

A123s are nominally 3.3V (no idea where 3.7V comes from) but are fully charged at 3.6V I've not come across any recommendation to charge higher but I have on occasions charged mine on a LiPo charge (one of my chargers defaults to LiPo after any interruption) with no apparent harm although I've discharged them to 3.6V immediately on realising.

On discharge they will quickly drop to a little over 3.3V and decline linearly to a little less until at around 5% capacity the rapid decline starts...

I'm not giving exact voltages as they depend on the load taken but we don't normally push any batteries to 95% discharge do we?

I'm much happier using LiFe cells than either horrible NiMHs or regulated LiPos. NiMHs can and do fail with little warning and running regulated supplies is even more likely to result in a sudden loss of supply if the battery capacity is pushed too far, in addition to the additional fault potential of additional components, wiring and connections.

SIMON CRAGG22/09/2019 02:54:19
431 forum posts
14 photos

I started using Lifepo4 rx / tx packs about three years ago. Absolutely superb!. Most of my models run on 1100mah packs.

Bill Reed03/10/2019 15:29:05
80 forum posts
2 photos

So I have just been into a E-cig shop which sells A123 18650 cells and chargers. The cells look quality by the way.

The dedicated charger they sell charges to 4.2v ,my LiPo charger set to A123 will charge to 3.65v.

So whats correct? will the 4.2v drop pretty soon after the charge? if not its a big difference.

Steve J03/10/2019 16:01:37
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1436 forum posts
44 photos

If they are charging to 4.2V/cell, they are not LiFePO4.

What did it say on the side of the cells?

john s03/10/2019 17:28:34
61 forum posts
2 photos

18650 e-cig batteries are Lithium Ion I think.

Martin is correct my Life po4 receiver packs come of the charger at 3.6v a cell 7.2 v total.

When I first started using Life packs I was a little cautious but now think they are brilliant , I particularly like that you can leave them for a few weeks and they still have enough charge to go flying.

SIMON CRAGG03/10/2019 18:55:54
431 forum posts
14 photos

When I first started using LifePo4 rx packs, I kept a record of how many milliamps a ten minute flight used. It was never over 100mah (3D aerobatic), to 40mah for a 3 channel vintage model. So I have always used lightweight / cheap 110mah 2 cell packs.

Martin Harris04/10/2019 01:26:39
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8793 forum posts
215 photos
Posted by Bill Reed on 03/10/2019 15:29:05:

So I have just been into a E-cig shop which sells A123 18650 cells and chargers. The cells look quality by the way.

The dedicated charger they sell charges to 4.2v ,my LiPo charger set to A123 will charge to 3.65v.

So whats correct? will the 4.2v drop pretty soon after the charge? if not its a big difference.

I've done a little research and A123s can be charged to a maximum of 4.2V but A123 Systems state that they recommend a maximum of either 3.6 or 3.8V depending on charge strategy.

chris larkins05/10/2019 23:07:15
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191 forum posts
124 photos

I throw my hat into the 'Pro Life' ring, I have 5 models that use these as the RX power source and have never had any issues, even after months of storage they are still full and once in use the RX/Servo's seem to drain them far less than when they were NiMh powered........ probably due to the higher voltage.

On the first few models I used a 6A diode to drop the voltage down to approx. 6 volts but the last 2 models I haven't bothered and the servo's haven't suffered any ill effects, if you are using HV servos then there is nothing to worry about anyway.

I have made up a charge lead using a multiplex connector which enables me to balance charge them whilst they are still fitted into the model..... unlike LiPo's they are not volatile and there is no need to remove them during charge.

These are the batteries that I am using

Link 1

Link 2

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