Charging LiFePo4 batteries

[brokenenglish]

I have a very simple question for our battery experts.

Both my (excellent) chargers have a LiFe charge/balance function.

The HK web site states that LiFePo4 batteries need a specific LiFePo4 charger.

Can my LiFe charger be used to charge LiFePo4 or not?

As I'm never exactly at the cutting edge of technology, others must have already answered this problem...

[Nigel R]

Cutoff voltage is the important factor here.

The HK website mentions this to prevent (well, you get the idea) accidental use of a LiPo only charger.

If your charger has the right mode for LiFe, then it should work just fine.

[Phil Green]

In the chemistry menu, most chargers state the nominal voltage, for example the universal B6 and its clones state 3.3v against LiFePo4. Thats the setting you need. The terminal voltage is the critical thing, whereas we're all used to 4.2v for lipos, for LiFePo4's the CV voltage should be 3.6 or 3.65 volts. If you charge LiFePo4's to 4.2v they will be damaged but not with the spectacular results of a lipo overcharge.

[Romeo Whisky]

I think the main point you need answering is simply confirmation that LiFe is the common abbreviation for LiFePo4.

It is.

So your LiFe settings on your charger will be specially designed for LiFePO4 batteries.

[Phil Green]

The difference is clear enough in a written context but you must be careful when verbally speaking to someone about lithium-ion and lithium-iron

[brokenenglish]

Posted by Romeo Whisky on 22/10/2019 13:20:56:

I think the main point you need answering is simply confirmation that LiFe is the common abbreviation for LiFePo4.

It is.

So your LiFe settings on your charger will be specially designed for LiFePO4 batteries.

Thanks a lot RW!

If no-one disagrees with you, then you're certainly right in saying that I needed that clarification and it is a total answer to my question.

Thanks to all who answered. I need to get this clear as I have to replace my old IC plane Rx packs. I'm still on Nicads!

Just one point. One does sometimes see other "types" of LiFe. I'm sure I've seen LiFeA123 or something like that.
Is that detail important or not?

Edited By brokenenglish on 22/10/2019 14:11:48

[Nigel R]

The main thing is that they are LiFe chemistry which determines the charging settings needed.

"lithium-ion and lithium-iron"

you be careful with that can of worms there!

[Martin Harris - Moderator]

A123 was a trade name used by the company who supplied some of the big name power tool manufacturers as well as producing power packs for electric vehicles.

[Phil Green]

"A123 Systems" put LiFePo4 on the map over 12 years back. My 12-year-old A123 cells are as good as new!

[Don Fry]

A properly cycled NiCad lasts a very long time. And yours must be cycled, as you still fly them. If they work, they are good. But, if replacing them, LiFe are a good, solid, reliable battery.

NiMh are a useless battery for our uses, made useful by bodges like Sub C cells , if you want power. Hard work to charge reliably, with a frisson of fear you messed up. Lost count of the times I've left a plane behind because the charger has cut out on a false peak. And that requires a brain cell to tell me how much it should need.

I have one NiMh pack, in a plane under repair. It will see out the airframe, it's done as advertised. But if it failed a test, it's gone, and not replaced, like for like.

[brokenenglish]

Thanks everyone!

Don, Yes I agree. When Nicads were "phased out" in Europe, I purchased a stock of Nicad Rx packs from the USA. Unfortunately, we had serious flooding here in June 2018, and my "stock" spent around 30 hours under water.
So the only packs I have left are those that were actually in planes at the time of the flooding (3 packs).

Playing with old spark ignition engines quickly taught me that Nimh are weak and unreliable in high-risk applications (Rx packs), and Lipos are the way to go. So I carried out some interesting experiments with Lipos for receivers, without any voltage regulator, which basically concluded on the need for LiFe.

[Fatscoleymo]

Posted by Don Fry on 22/10/2019 19:38:41:

A properly cycled NiCad lasts a very long time. And yours must be cycled, as you still fly them. If they work, they are good. But, if replacing them, LiFe are a good, solid, reliable battery.

NiMh are a useless battery for our uses, made useful by bodges like Sub C cells , if you want power. Hard work to charge reliably, with a frisson of fear you messed up. Lost count of the times I've left a plane behind because the charger has cut out on a false peak. And that requires a brain cell to tell me how much it should need.

I have one NiMh pack, in a plane under repair. It will see out the airframe, it's done as advertised. But if it failed a test, it's gone, and not replaced, like for like.

b

Beg to disagree Don...NIMH AA are all I use, just use a wall wart charger and never had a problem....all I do is check them the day before I am going to fly and top them up...easy peasey...

[Don Fry]

Lucky boy. Mind a wall wart does not have peak charging.

In a previous life I used wall wart chargers to charge flash gun batteries. A bit faster charge . Didn't last long. Never did a job without a couple of spare packs. Not trusted to do a hundred flashes. Older packs were ni cad, we cycled them, lasted forever. Like packs which had been in continuous use for a decade or so. The wires broke before the pack failed,

Edited By Don Fry on 25/10/2019 20:04:37

[Martin Harris - Moderator]

I've got 2 torches which date back to the late 80s/early 90s with NiCd packs which have built in 12V and 240V chargers in lantern battery sized packages. Both still hold a decent charge and have simply been charged and left until they needed recharging.

I don't reckon on seeing more than 3 years use from NiMH cells and have lost models due to rapid failures.

[leccyflyer]

Makes you wonder how we ever managed to fly using NiMhs after NiCds were phased out. Those GP3300mahs and FAUP 1950s must never have worked and the Sanyo and Eneloop NiMhs receiver packs in so many models must be figments of the imagination of many thousands of users.

The only LiFe packs I've used are for transmitters and found them fine - however I've modified my charging regime to charge at 0/8C rather than 1C, after less than expected LiFe time and replacing a couple of packs. The benefit of getting much longer use of the TX between charges compared to NiMh and NiCd tx packs is worth having. Haven;t tried LiFe for motor power, though they are a better match for some of my older brushed inrunners, with the sweet spot on 8 cells, where 3s1p Lipos are just too hot.

[Peter Christy]

Its a case of horses for courses. Nothing wrong with carefully chosen and maintained NiMhs. As with so many other links in the RC chain, use good quality stuff and you will be rewarded with reliability.

Yes, LiFe cells have advantages, but only if the rest of the system will tolerate the higher voltages. Most of my servos are JRs, which are notoriously intolerant of higher voltages, so most of my models fly on 4-cell NiMhs.

I'm not a fan of voltage regulators. I've seen them cause far too many problems in the past.

For normal models, I find 2000mAH Eneloops just fine, and for bigger ones and spark ignitions, sub-Cs. Again, the ignition system on my big gasser helicopter won't tolerate 5-cell or LiFe voltages - and in any case, I need the nose- weight on that one! Its either big batteries or a large lump of lead!

Peak detect chargers have largely solved the old "black wire" corrosion problem that used to plague NiCad and NiMh cells, and also tend to reveal any issues before they become critical.

My only caveat is to beware of going for cells with the highest capacity for a given size. My experience indicates that the higher the capacity, the higher the internal resistance. This can lead to voltage drops under high load. I stick to 2000mAH for AA cells and 3300 for sub-Cs even though higher capacities are available.

Oh, and stick to a good brand name, like Sanyo or Panasonic.

Just my 2p worth!

--

Pete

[Simon Chaddock]

+1 on using good (probably more expensive) brands.

It is not unknown for brand reject batteries (usually out of spec IR or capacity) to end up re labelled and cheap on Ebay. and I am speaking from experience!