Checking LiFe packs, can you settle this for me.

[trillian]

I had read some time ago that with LiFe packs you cannot accurately check the remaining charge using one of these little battery checkers. I was told this is because the voltage does not steadily drop like it does with a LiPo, so a device that looks at the cell voltages doesn't really tell you anything useful (unless it's really really, unflyably low or something). That has been my understanding.

So, yesterday at the club I was in a discussion about RX packs. On my gasser I use the 2s LiFe packs for simplicity and they have been working very well, but I don't try to check them at the field, I simply charge them fully and then I know from experience I can get three or four flights with plenty of safety margin.

In the conversation I mentioned that one thing I do like about LiPos is that you can easily check the remaining charge. The guys there are all like "oh you can check LiFe's as well" and someone had one of these battery checkers and it has an LiFe setting. I was trying to explain that although it may very well show you the voltage, knowing that doesn't really mean anything, but all I got was a blank stare and "well this battery checker CAN check an LiFe". So I just didn't argue the point any further.

Sooooooo, am I wrong about this? Is there a battery checker that can give you a meaningful view of the remaining charge in an LiFe pack?

[Planehazza]

I had read some time ago that with LiFe packs you cannot accurately check the remaining charge using one of these little battery checkers. I was told this is because the voltage does not steadily drop like it does with a LiPo, so a device that looks at the cell voltages doesn't really tell you anything useful (unless it's really really, unflyably low or something). That has been my understanding.

So, yesterday at the club I was in a discussion about RX packs. On my gasser I use the 2s LiFe packs for simplicity and they have been working very well, but I don't try to check them at the field, I simply charge them fully and then I know from experience I can get three or four flights with plenty of safety margin.

In the conversation I mentioned that one thing I do like about LiPos is that you can easily check the remaining charge. The guys there are all like "oh you can check LiFe's as well" and someone had one of these battery checkers and it has an LiFe setting. I was trying to explain that although it may very well show you the voltage, knowing that doesn't really mean anything, but all I got was a blank stare and "well this battery checker CAN check an LiFe". So I just didn't argue the point any further.

Sooooooo, am I wrong about this? Is there a battery checker that can give you a meaningful view of the remaining charge in an LiFe pack?

Nope, I agree with you Cheryl. As far as I understand it, LiFe do not discharge linearly (if that's the right word) like a LiPo. LiFe will drop from 100% and stay 3.3v per cell for a considerable portion of the discharge, which is why you cannot calculate remaining fuel as per Lipo. Now, if the battery checker was onboard and monitoring mAh used, you could easily work out ToF left by working out mAh used vs total mAh as a percentage. With Life, it will just suddenly leave 3.3v and start hitting low voltage, so as you say, the only real safe way of monitoring pack level is by carefully guestimating it byt working out what an average flight uses + a safe margin and dividing the total capacity by that to ascertain flights per pack.

No disrespect to your friend, but it suggest to me he doesn't properly understand LiFe chemistry. Unless of course I'm wrong and he in fact understands it better than I thought I did!

[trillian]

Thanks, that is my understanding as well. I think with the guys at the club, because the little battery checker has an 'LiFe' setting and shows a percentage charge, they're just assuming that it can actually be relied on just like with a LiPo.

No disrespect to your friend, but it suggest to me he doesn't properly understand LiFe chemistry. Unless of course I'm wrong and he in fact understands it better than I thought I did!

[Planehazza]

Thanks, that is my understanding as well. I think with the guys at the club, because the little battery checker has an 'LiFe' setting and shows a percentage charge, they're just assuming that it can actually be relied on just like with a LiPo.

Yeah, it will do, and it will only be good if the battery is at, or very near to, 100%. It'll just have different calibrations applied to assign 100% to n*3.3v instead of the LiPo Voltage. I don't know any checker to guage the fuel of a LiFe pack, but I'm no expert. Maybe Angelos, Mr Spartan himself, may know better?

[PKNEC]

I had read some time ago that with LiFe packs you cannot accurately check the remaining charge using one of these little battery checkers. I was told this is because the voltage does not steadily drop like it does with a LiPo, so a device that looks at the cell voltages doesn't really tell you anything useful (unless it's really really, unflyably low or something). That has been my understanding.

So, yesterday at the club I was in a discussion about RX packs. On my gasser I use the 2s LiFe packs for simplicity and they have been working very well, but I don't try to check them at the field, I simply charge them fully and then I know from experience I can get three or four flights with plenty of safety margin.

In the conversation I mentioned that one thing I do like about LiPos is that you can easily check the remaining charge. The guys there are all like "oh you can check LiFe's as well" and someone had one of these battery checkers and it has an LiFe setting. I was trying to explain that although it may very well show you the voltage, knowing that doesn't really mean anything, but all I got was a blank stare and "well this battery checker CAN check an LiFe". So I just didn't argue the point any further.

Sooooooo, am I wrong about this? Is there a battery checker that can give you a meaningful view of the remaining charge in an LiFe pack?

That's my understanding too.
I just fully charge my Life packs due to the rapid voltage drop towards the end.

[Varelco]

I have never owned a LiFe but I think if I did I would figure out what the demand is from the heli. So fully charge the LiFe pack, do a flight, recharge it and see how many mAhs are put back into the pack. Use that figure as an average to determine how many flights you can safely get out of a pack, much like calculating how much fuel you would need for a journey.

[trillian]

Yeah that's what I do. I already know how many flights I can get and still have a good margin for error. They charge very fast so it's easy to charge a few packs and go. I only use them on the gasser and the other options would be to go all HV servos and use a 2s LiPo or use a Lipo with a regulator but as the servos I have now are fine at 6 volts the LiFe packs are an easy option and keep it as simple as possible.

I have never owned a LiFe but I think if I did I would figure out what the demand is from the heli. So fully charge the LiFe pack, do a flight, recharge it and see how many mAhs are put back into the pack. Use that figure as an average to determine how many flights you can safely get out of a pack, much like calculating how much fuel you would need for a journey.

[hedge]

I mainly agree with whats posted. What I don't understand is how my Spektrum DX9 does it - https://www.horizonhobby.co.uk/Spekt...FVcW0wodHMAE2w

Counts down quite nicely, no sudden jump?

[Mark_T]

I mainly agree with whats posted. What I don't understand is how my Spektrum DX9 does it - https://www.horizonhobby.co.uk/Spekt...FVcW0wodHMAE2w

Counts down quite nicely, no sudden jump?

That isn't a LiFe pack...

[PKNEC]

That isn't a LiFe pack...

Yeah that's what I thought the ones I'm using are lithium ion phosphate A123 cells. LiFe po4

[hedge]

That isn't a LiFe pack...

Oh, I thought Life an Li ion where the same?

Just to add...
https://en.wikipedia.org/wiki/Lithiu...sphate_battery

[Mark_T]

Oh, I thought Life an Li ion where the same?

All LiFe packs are Li Ion, not all Li Ion packs are LiFE...

A good clue is to check the nominal voltage, LiFE will usually be 3.2V or 3.3V where as LiPo will be 3.7V

[antsis]

Most common are LiFePo4 or Lithium Ion Phosphate.

A fully charged LiFe pack will generally show as 80% on the small checkers. As mentioned, it is difficult to accurately measure the pack capacity. You will also notice that as the pack comes off charge, it will measure over 7V, but this will drop quite quickly to 6.6V. Totally normal. I use these packs on all my models that do not have HV servos as well as my heli starter and the 12V compressor for my jet. They are pretty strong compared to Lipo's and can handle being stored at full charge. However, they will drop off really quickly if used a lot. The best way to check them is to record how much current the charger puts in after a day's flying.

[Guest]

I've used life packs as well before HV servos work well just charge it up a lot they fall off the cliff when they run down. After a few flights you can gauge it on useage as others have said.

MJ