Proper Lipo Care?

[mjr_larkin]

I need a lipo care 101. Didn't find a tutorial with a qucik search but probably just didnt search right.

These are the things I've heard about caring for lipos
1) If the pack is new then full charge it and discharge it 50% with a hover. Repeat this a few times to get the pack at full capacity charge
2) Never discharge the battery to lower than 20% capacity
3) Make sure to balance charge

Are these things right? I use a cellpro 4s and when I plug the packs in it typically reads 9% fuel. So am I discharging too far? And what special care should I take with a brand new battery? thanks!

[Pinecone]

Cell Pro fuel reading assumes that 20% is empty. So 9% is really 29% from DEAD.

Also NEVER let a cell go below 3 volts.

Never let your packs run too hot.

[Ultraviolet]

Cell Pro fuel reading assumes that 20% is empty. So 9% is really 29% from DEAD.

Also NEVER let a cell go below 3 volts.

Never let your packs run too hot.

Are you sure about that Pincone ? I always thought that the cellpro displayed absolute pack capacity. So 9% would indicate an overdischarge.

[blueviewlaguna]

I have discovered that the 1C (autodetect) setting slowly increases the charge current, while the manual amp setting goes right to the current selected. While the 1C setting is "autodetecting", it seems that the fuel reading is lower than actual, perhaps due to a certain amount of current needed for their fuel algorithm to be accurate.

[mjr_larkin]

Are you sure about that Pincone ? I always thought that the cellpro displayed absolute pack capacity. So 9% would indicate an overdischarge.
This would be easy to test by looking at the cell voltages. If the "true" pack fuel is 29% then what should the voltage read?

[Pinecone]

Well my two put back in less than 80% when reading near 0% fuel.

If it reads 9% when you plug it in, how much do you put back in when charging? And what size pack?

If it reads absolute, then you should put back in 91% of the pack capacity, and if it reads % over 20%, you would put back in 71%.

[mjr_larkin]

I can confirm that the cellpro reading is most probably the TRUE fule not whatever the reading is + 20%. I have a 600 mAh battery and after flying, I plugged it in to the charger and it read that it is 10% fuel. After 100% fuel it says it has put back in 520 mAh. 10% of 600 is 60 so 520 + 60 is 580 mAh so almost completely full. If the 10% fuel reading was actually 30% then I should only be able to put 420 mAh. Hope this helps.

I've read lots of suggestions about discharging lipos. Some say they discharge almost 100% for hundreds of cycles and nothing went wrong others are more careful. Maybe it depends on the brand.

[Pinecone]

Do realize that the fuel level reading is very approximate.

But I will check mine this weekend. A quick check would be to run your pack (or charge to) 3.8 - 3.85 volts per cell (storage charge on the Cell Pro) and see what it reads. That is a 50% charge.

[int2str]

Pinecone is right.

When I charge my packs they are usually around 3.7V and the charger says "20%" fuel. The "fuel gauge" has a safety margin built in.

[Cryofix]

When storing your batteries make sure they are 50% charge, if its longer than a few weeks also keep them in the coolest place you can find.

A battery stored at full charge in 90 degree heat will loose 30% capacity in about 2 weeks

Most manufacturers are now saying that you can charge packs at 2c, while this may be safe it still is not good for your cycle life of a pack.

If you have to you can charge at 2C but its best to cap it at 1C and extend you packs life.

[int2str]

you can charge packs at 2c, while this may be safe it still is not good for your cycle life of a pack.

This is an urban legend in my opinion.

See here:
http://helifreak.com/showpost.php?p=591341&postcount=6

[arne997]

I am a newbee and I have a question!

My 11,1v 2200mah Lipo was maybee discharged to much because when I charged it, it took 2050mah before charging was compleate. Does this mean that I have destroyed the Lipo? It is only used 5 times.

[Cryofix]

all this means is you over dishchared your lipo, a general rule of thumb on lipos is only discharge to 20% capacity

Your battery is 2200 mah and 20% of 2200 is 440 mah so minus the 440 from 2200 and you get 1760 Mah

The most you ever want to see yourself putting back in your pack is 1760 mAh

Your battery should be ok, in an over discharge like this the best thing to do is drop the amp you charge at, so if you normally charge at 1C (2.2 amps) then drop that to 1.1 amps and slowly charge and balance the battery to full

make sure you number your packs, and next time you fly, fly for 3 minutes, then charge, make note of the mAh going back in to the battery if you put back 1000 mAh you know you have 760 mAh to go before your 20% so next flight fly for 4 minutes and see what your mAh is when you recharge this should be a good gauge as to how long you can run for without over discharging, then get a timer or use the one in your radio if you have one.

Hope this helps

[mjr_larkin]

Pinecone is right.

When I charge my packs they are usually around 3.7V and the charger says "20%" fuel. The "fuel gauge" has a safety margin built in.
I don't think I understand the safety aspect of this. If a battery is over discharged, reporting a higher than actual fuel value is not going to help anything. Maybe if you were watching this fuel reading during flight but of course that's not the purpose of it. If anything it is maximum of 5% off from the actual level so I think it's pretty reliable.

[Pinecone]

If you overdischarge the pack, you have shortened the life. How much? No way to really tell, but don't do it again. The mor eyou do it the shorter the life of the pack.

IMO, if you overdischarge a pack, just go and use it. No need to do anything special.

As for the Cell Pro, it should read - if you over discharge. But maybe the pack is under rated. Do a discharge test to check capacity. Discharge with a wattmeter and check voltage versus mAH.

[trickybit]

I read propositions here that the "Fuel %" is relative to a 20% safety margin, and also relative to 0% margin.

I revisited their site and manual and couldn't find direct information. I guess I could write them, but I'd rather add to the conversation here...

I'd like to compare (more) careful measurements to see if we can reverse engineer it to everybody's satisfaction, and leave some useful lore behind. Capacity can be considered in mAh or voltage. mAh would be nicer metric, because we would expect it to be more linear, and convertible to power, flight time, etc.

But in their manual, when talk about storage mode, they say, describing storage mode:
In STORE LiPo @ 50% Mode, LiPo/Li-Ion cells are individually charged to 3.842V or
50% capacity. This is a good charge level for long term storage or shipping by mail.This suggests a calculation in voltage. Here are two possible formulations. I'm sorry that I'm not 100% sure of my calculations. Putting the thing into a spreadsheet would probably be overkill, but I'd like to collect data, compare notes, and confirm or refute & improve the thing.

My calculation based on remembered numbers during a recharge says the safety margin is 10%, and "Fuel %" remaining is relative to that.

proposal:
fuel = % of useful capacity in mAh (above a 10% safety margin) remaining

battery -
capacity: 2200 mAh
10% safety margin: 220mAh
useful capacity range = 2200 - 220 = 1980 (= 90% of 2200)

recharge -
declared Fuel %: 9% remaining
mAh added in charge: 1800 (approx)
mAh remaining before charge: 2200 - 1800 = 400
mAh over charge safe margin: 400 - 220 = 180
percentage of useful capacity that had remained: 180 / 1980 = 9%

---
another calculation, based on volts:
from the manual, describing 'storage' mode:
50% = 3.842 V
(100% = 4.20 V)
50% to 100% = 4.20 - 3.842 = 0.358
therefore, 0% = 3.482 - .358 = 3.12 V
So the safety margin in volts would be at 3.12; I don't know if that's supposed to be an official line or not.

Anyway, maybe this is on the mark, maybe not. I should probably just write them. I am actually curious about this, since I'm trying to get in a lot of stick time, but I don't want to push it too far.

Jim

[Pinecone]

Well yesterday I threw some packs on the Cell Pros (to go fly not to test).

The one pack I remember read 11.35 volts and 35% Fuel. 11.35 volts equates to 3.783 volts per cell. Definately above 35%, since 3.84 is 50%, but should be less than 50%.

I don't normally look at the Fuel, I look at mAH back into the pack after the charge is finished. Estimating fuel % by voltage is a WAG, close but not that accurate, IMO.