What is the lipoly charging forumula?

[DebianDog]

I thought saw it here but can't seem to find it :(

Lets say I have a 1000 Mah pack and drain it to the 80% rule. So I have to put 800 Mah back in the pack. How long will it take charging at 1C (1 amp) to recharge the pack to 100%?

[Skiddz]

About 48 mins.

If you charge at 1C, it'll take about 60 mins to "feed" the battery 1000mah. That's about 16.7mah/min. 800mah / 16.7mah per min = 47.9 mins.

[z11355]

in theory.

but, most chargers seem to determine their own charge rate (not exceeding what you've input)
so in reality, it's going to take longer. this is also a function of the software algorithm the
charger designer is using.

[Pinecone]

Actually it takes about a hour no matter what. This is because lipo charge constant current/constant voltage. The 1C time is the constant current time, and lasts until the charging voltage gets to 4.2 per cell, then it holds that voltage until the current drops to some low value.

The time to charge during the 1C portion depends on how low the pack is. The time to get from there to charger cutoff stays the same for a given pack.

[DebianDog]

Actually it takes about a hour no matter what.

Yep after reading and searching around, 1 hour is almost by definition 1C.

What is C-rate?

The charge and discharge current of a battery is measured in C-rate. Most portable batteries are rated at 1C. This means that a 1000mAh battery would provide 1000mA for one hour if discharged at 1C rate. The same battery discharged at 0.5C would provide 500mA for two hours. At 2C, the 1000mAh battery would deliver 2000mA for 30 minutes. 1C is often referred to as a one-hour discharge; a 0.5C would be a two-hour, and a 0.1C a 10-hour discharge.

[Pinecone]

Actually from fully discharged it will take over an hour, because it doesn't charge at 1C for the entire charge.

I find my packs take about 65 - 75 minues to charge at 1 C, whether they are lightly dischared or the full 80% limit I use.

[DebianDog]

Yeah but you only discharge to 80% so... I said "almost "

[Skiddz]

I wonder what would happen if I discharged to 20%.. Would the charger's software make it take an hour to get the pack back to full charge???

[Pinecone]

No, the way it works is the charger starts off by charging at the amperage you set. 2.1 amps for a 1C charge of a 2100 pack. At first it may only take 11 volts to push 2.1 amps into the pack.

As the pack becomes charged, it will take a higher and higher voltage to continue to put 2.1 amps into the pack. At some point that voltage will hit 12.6 volts (for a 3S pack). And since we know that more than 12.6 volts for a 3S pack is bad, the charger will hold that 12.6 volts and accept whatever charge rate (amps) that it gets. So the amps number will start dropping. Adn at some point the charge rate will go low enough that the charger will say, Enough, I am done. On my Triton that is at 0.1 amps. On my TP 1010C with a 2100 pack that number is about 0.2 amps.

The initial charge is the contant current section. And that will vary depending on how much the pack is discharged. The second part is the constant voltage part and that will take about the same amount of time everytime you charge.

NiMH and NiCd can take higher voltages, so they can charge at a given amp rating for much more of the charge cycle.

[DebianDog]

So a 95% charge is the charge point it hits the big AMP drop right?

[WillJames]

The 1010 will already be stepping down the charge by the time it gets to 95% most likely. I will have to pay more attention next time, but at 95% you will hear the beeps and the status light will glow solid on the balancer. From my best recollection the charger would have stepped well down from teh 1C I charge at by the time the pack is 95% charged. Probably from 4A down to about 1.5 or 2 by 95%

[Skiddz]

My 1010c/210 starts beeping with about 5 mins to go.. I figure it's just everything equalizing out as the battery peaks. I need to teach the kids to ignore those beeps 'cuz they always call out "Dad!!! it's done!" when they hear the 1st tones.. :)