Li Ferrous Batteries

[retiredbri]

I've come across Lithium Ferrous Phosphate batteries (a.k.a. LiFe, LFP or LiFePO4) made by the A123 company. Go to
a123systems.com/products and select "Cells: 26650". Also look the "download specs (right hand side).
They appear to be safer than Li Po and can be "fast" recharged in about 15 mins. They are heavier and only 3.3V but can be completely discharged.

The blurb says "just but two, fly with one while the other is charging, then swap over to keep flying all day"
Sounds too good to be true.

Puffin Models in the UK sell them (packaged into 3S, 4S etc) plus the chargers.
www.puffinmodels.com/category.php?dept=165 and look for A123 Battery Packs.

Anyone come across these or used them?

Regards

retiredbri

[flydiver]

They come in 2 sizes - 2200aH, and 1100 (vpx). The 2200 are about the size of C-cells, the 1100 are what known as 18650 designation and about AA size.

Full voltage is 3.6v. They are essentially empty at 2v. Starting at a lower voltage to begin I use a 4s vpx to replace a 3S lipo. Weight wise a 4S vpx is a tad heavier and bulkier than a 2200 lipo. Mostly if your plane is under 3# the 2200 are too big. 1100 are OK for med. sized park fliers. If you wouldn't put a 2200 lipo in it, don't bother.

They will take over charge and over discharge abuse WAY better than lipos. How quickly they charge depends almost entirely on your method and charger. Your charger HAS to be A123 capable or get a special 'balancer' (terminator). There is a very quick method called [zip] charging good for 3S using a car battery, a simple lamp cord, and a terminator or wattmeter. Oh, and initially, nerves of steel I think. I've never done it. I use the Cellpro 4S. That charges at 4A.

I would not completely discharge them. I've done that accidentally to a similar 18650 similar pack using emoli cells and it killed a cell. Anyway, you wouldn't have any control with a dead pack.

Your ESC will need to be configured to work. Usually the easiest method is just make it NiXX and let the LVC cut at 5V or where ever it ends up. Using lipo LVC will result in a premature cut.

If you do use NiXX and fly to LVC when the power dies.....it dies. It may not even start the motor again as you are WAY discharged. I had to ditch in a dirt lot once when I was too far away when LVC hit.

There are long discussions on this in RCGroups.com. The guy in the know there is Charles [everydayflyer]. He knows his stuff.

[retiredbri]

Thanks for the heads up.

I've not moved to LiPos, still using NiMh. 475 flights on the good old Cub.

I'm reading more and more about LiPos wearing out and am suffering the same with my NiMh batteries.

In the future. I'm thinking of getting a Multiplex Mentor and from what I've heard, Li Fe batteries will fit OK.

For a start, before I get the new plane, I though I'd get two of the 3s Li Fe batteries and the charger and adapt my cub to take them. I think the 1100 would be ok.
With the NiMh wearing out and LiPos likely to do the same, the Li Fe seemed a reasonable way to go.

What are your experiences of LiPos after a lot of charges/flights?

Regards

Retiredbri


Forgot to say: I thought the voltage was 3.3V so 3S = 9.9V compared with my 8 cell NiMh = 9.6 volt

[flydiver]

Depends - there are lots of variables, the big ones being quality and knowledge.

Get decent lipos, treat them right > they can last a long time.

Trouble is----
1. Many get ?? quality lipos and being able to tell the difference is NOT easy. Price isn't always a good indicator but is often the only yardstick readily available.
2. Many people have no idea what treating them right even entails, so don't.
3. Some folks don't care....I got them cheap, so I thrash them. Then I get more.

I've had lipos I thought were treated right just up and die on me. Others (also treated right) are doing fine after over a year. I've only been flying lipos a bit over a year so don't have the track record of some folks.

A123 have worked fine but I've only been using them 6 months and the only one ruined was a HORRIBLE crash so can't blame the battery.

If you put an A123 vpx 3S in the stock Cub you won't be happy I think. It'll hit LVC quickly most likely. You would be better with 4S.

[duck9191]

i know a few 3-4 year old lipos still being ran hard. i think he said they are down about 200mah in capacity but still deliver current like it should. its not treated nicely either, its one of his 2200mah 20c edf packs that are pushing 41amps and has 0 air flow so it gets warm.

[ginginho]

Bri,
If you are tempted to go Lipo then I suggest you take a look at www.giantcod.co.uk and what Rob has for sale there. His prices are very competitive, all comments (on various forums) suggest that the LoongMax Lipo's are one of the best budget batteries. I use them, my mates use them, most other flyers I've met at the field have them too! The most recent batch now have silicon wires for the balance leads, overcoming the only issue anyone has had with these.

I'd also recommend the GTA-6 charger, which is a dream to use, very safe and can charge NiMh, LiFe, Lipo etc etc.

I use the 20C 2250mAh 3S's which require a bit of sculpture of the battery box.

[retiredbri]

Thanks all

Still thinking of giving the LiFe cells a bash. The chargers that Puffin Models sell (as well as the A123 batteries) are Lipo and LiFe compatible. www.puffinmodels.com/

At the moment, I'm calibrating my old NiNH batteries and have identified 3 "reversed cells" in 3 out of my 6 battery packs.

I'm getting some time/current/throttle curves to see what I need. Half throttle is about 4.8 amps and the 8 cell pack give that after 15 minutes. The 7 cell gives that for 12 minutes.

Where I'm coming from is that if the NiFe cells can give a good flat voltage discharge curve, I may get away with 9.9 volts (3 cell pack) 2200mAH. This would give me about 20 mins high power flying and 28 mins on circuits.

This LiFe exercise is to see if these cells can be used for the Multiplex Mentor that I might get next. This will be the fast plane that will cope better than the cub with the higher winds and go one stage up on the cub for some aerobatics.

Regards

retiredbri (currently the oldest in the forum )

[duck9191]

the mentor is like the magister i have but with no flaps. its fun, but yet easy to fly. just needs a bit more speed to get it in the air then the cub. i have been flying in about 20mph winds, it takes a bit work but its do-able. i went brushless with mine so its a bit more powerfull then stock, but it still should do ok in the wind