LiFe PO4 Packs

Have started using LiFe PO4 2 cell packs (6.6v) in my newer planes with HV servos rather then rely on BEC output, regulators or heavier Nimh packs. When fully charged they only show 85% charge at the end of the charging period. This is because LiFe and Life PO4 have different characteristics. Both my mulitchargers only suit LiPo, LiFe and LiLo but not PO4 chemistry.

I have been pondering this problem for hours and cannot seem to come up with a good answer even for myself. How can I be sure they are fully charged?

Hi Phil,

What is showing you they are only 85% charged, your charger or a cell checker? If a cell checker is it set to the right chemistry?

As a side note, I like the way the NanoTech RX batteries say 'High Discharge Battery' in big friendly letters. You'd have to have some serious servos to need the 20C rating

Chris - These TX/Rx packs come with standard "servo" leads which saves a lot of socket changing. It's not so much the "high discharge" but the fact that you can charge them real quick if you forget to recharge or had a lot of flights. The battery checker only covers Lipo, LiFe and Nicad, Nimh. Switch to Life and get 85% charge. Switch to Lipo and it says 2%! These new versions of LiFe aka PO4 chemistry are safer apparently being nearer NiMh in voltages and can be left in the plane whilst charging. A two cell = 6.6v nominal is relatively small and light weight.

I have a three cell LiFe in my TX too at present. Fully charged shows on the screen as 10.2 volts but settles down to in the range of 9.9 to 9.7 depending on use. Either I need to find a quick tester for these packs or a dedicated charger, the latter means more equipment and expense.

Footnote: This new chemistry is used in cars, buggies and power cycles

The commonly used checkers do not appear to give accurate results when on LiFe settings. I just charge using settings as per either of my chargers, as I use reasonable capacity packs I believe I have plenty of spare power.

Stuart

Like Stuart says, you cannot use a voltage checker to tell you the remaining capacity of a LiFe battery. Those claiming that you can do not understand how to interpret a discharge curve!

LiFe and LiFePO4 are one and the same. There is no such thing as "new versions of LiFe aka PO4 chemistry"

You say that a good feature is that you can charge them real quick...A 20C LiPo can be charged at 2C and a 40C at 4C. I wouldn't do it every time, but no harm will come from the occasional fast top up.

Thanks Guys for your input. Have done some research and created an article in Reviews on these batteries for information to those interested. wimbornemac.org/articles/reviews/179-lifepo4-batteries

I agree Stuart with your idea and will set up on two of my user programmable chargers a user set-up for these packs. I will use the details from the linked article. After a set time of use will recharge to see mh being put back in which will hopefully give me a guide to number of flights/uses before recharge.

Hello Phil, I've been using LiFePO4 batteries for about two years without any "incidents". Like you, I couldn't get to find out just what the true capacity of the battery was after charging. Last year I changed my old charger for an IMAX 6, this gave encouraging numbers while charging, and has lots of facilities for maintaining all sorts of battery types. I was using Eneloop NiMH 2000 mAh four cell packs, I found that I kept getting the occasional "Brown Out" when using Spektrum receivers, strangely never had the same problem with either Orange or LemonRX receivers. All the glitching stopped when I changed over to LiFePO4 packs. The only problem I've had so far was caused by inadvertently leaving a couple of models switched on for about a week. The batteries couldn't be charged as the smart circuitry of the charger wouldn't allow a charge to start due to the low voltage. The other worrying thing was that the battery packs had puffed up. I put both batteries in a safe place outside and left them for a week. Nothing had changed re the puffing so I tried to revive the packs by setting the charger to the NiMH mode and charging gently at 100 mA rate. Once the battery voltage had gone over 2.5V/Cell, I switched over to the standard LiFePO4 program on the charger, both packs accepted a charge, but because they were still puffed, I stored them outside. After a week or so, I cycled both packs three times, the nominal capacity of the packs was 1100mAh, the final capacities shown on the charger were 1039mAh for one and 1065mAh for the other. Strangely, the puffing is decreasing with time, and now both packs are more or less back to their original shape. I expect that charging a pack using the wrong program is not to be recommended, but it was done in a safe area and was constantly supervised, very boring but was a good excuse to drink tea and eat chocolate digestives. Both packs have been tested under load, neither has failed, they re-charged with no problems and are still fully charged after a couple of weeks.

Hi Brian. I have used a similar method to get a few Lipos going again. I charged them on i306B at Pb settings for about 5 mins outside too! Then placed them on normal balance charge and they came up again. They have lost some of their umpf a bit maybe but still useable.

I have switched to LiFe on some of my models so the packs can be left in safely and for onboard charging. However, I have found that a LiPo with the same capacity and in conjunction with a regulator (set at 6.0v) uses less milliamps than a LiFe set up or appears to be.

Virtually all my models run either on Life (directly wired) or Lipo where I have used HV servos. This cuts out the need for regulators.