🔋 How to charge a LiPo battery with a power supply 

ElectronFun.com I'd never go above 4.250V. And make sure you remember the accuracy of your multimeter when doing the measurement as well as the fact that your PSU voltage may drift over time. Stick to 4.2V.

Afrotechmods Thanks a lot!

Kelvin Lei Yes

+Kelvin Lei 4.20 blaze it!

how can you know the peak voltage for charging?

read a data sheet

5 years ago, wow. glad it's still here.

Lol mee too! May make mine autonomous.. Do you have a remote for yours? I don't...

Actually, the drone failed because the stupid Chinese motors and props didn't work, so i abandoned the idea. May make another soon tho. scoob y

he is short circuiting it

so ive been charging my 3.7v li batteys on a 5v wall charger,, is that bad?

in theory chargin them up to about 70% is supposed to extend they life. Notebooks sometimes have an option on the bios to limit the battery to 70% instead of 100% to extend its life. In this case, though the safety is not really that important here, just limit it to 4,2 or 4,1 depending on the chemistry, it should also help its lifespan.

@Leharl Limiting the voltage to 3,95 V improves life span. The more you reach the 4,2 V, the shorter the life span is. 4,2 V is just a value that is safe, but this doesn't mean that it does not shorten life span. In consumer goods like smartphones they calculate, that the user is buying a new smartphone after 2 years, that's why they go up to 4,2 V. But in cars or military usage, a better life span is more important, that's why they set the limit to 3,95 V there.

OpenGL4ever didnt know cars limited the voltage to 3.95, you sure those arent LiFePo4? As far as keeping sight of the charge, i understand that just looking at the voltage doesnt work, that's why many ICs do coulomb counting to assest the current charge level. Not sure limiting it to 3.95 is a good meassurement for every lipo battery and each different chemistry/enhacement.

Laharl Krichevskoy They don't use LiFePo4 in Teslas. It might be different in other cars.

go directly to the pos and neg of the board where they connect and charge them directly that way , you want to get a proper charger though for sure

because when it reaches a certain voltage the battery starts drawing less than the constant current.

Because it was set to 4.2v and then constant current was turned on, so the power supply limited itself to 4.2v while trying to sustain a constant current.

it doesnt really "switch", it applies both limits, it just happens that when you limit the voltage the battery starts to draw less current

That current will work fine for cells down to 80mAH in size. I do, however, recommend using a diodes in series to prevent backfeeding. When there's no light, the battery could discharge into and damage the solar panel. A diode will prevent this and also add around a 0.7V voltage drop. Which, coincidentally, would result in the 5V becoming around 4.3V. Since the cells are protected, they'l shut off anyway, but extra safety is always a good idea.

@@alfa-psi ah nice thanks for the tip :)

@@alfa-psi ah nice thanks for the tip/correction :)

Yes it is because it's a 3.7V LiPo battery. That's how it is for them. Different battery chemistries would require different charging methods and voltage/current cutoffs.

@@Afrotechmods thank you! Also great information, I’ll try to find out more about different voltages now :)

Lead acid is basically the same, but at only 0.1C charge rate. Max voltage per cell is 2.4V for lead acid. So, to charge a 12V 75AH battery, set your power supply to 14.4V and 7.5A.

Daniel Jones but 14.4V is for liquid cells (which can gas a bit without problems), gell cells should never go above 13.6V. Also 14.4 is for continious use, like in cars. For stand by batteries, 13.6V again is better for extending it's life. Kevin McMillan Also in really hot days, say 30ºC+ you shouldnt charge it above 13.4V. 13.6V is the generic for ~25ºC but lead cells' voltage dependes quite a bit on temperature. If you're really interested you should look for the table that says which voltage is the optimum at which temperature.

Lots of info here on charging batteries. batteryuniversity.com/learn/article/charging_the_lead_acid_battery

The power supply will fix the voltage and allow the current to flow up to the designated current output limit. The battery will receive the maximum current allowed (the output limit) since it is drained and really wants to flow due to the battery having a lower voltage (V1) than the power supply output (V2). The allowable voltage difference (V2-V1) is set by the limit of how much current is allowed to flow (I-max). As the battery voltage approaches the power supply output voltage (the battery is charging) the internal resistances becomes more significant as the voltage difference decreases. So up until now the power supply has been told to keep allowing up to 240mA to flow (I-max) by maintaining the voltage difference (V2-V1) that supplies that I-max value. However, the power supply has also been told to only go up to 4.2V maximum, setting a limit on V2. Once that limit has been reached, the V2-V1 voltage difference cannot be maintained for I-max since the battery voltage V1 is still going up but the power supply output limit voltage V2 has reached its limit value at 4.2V. This means now the voltage is the limiting factor on the power supply, and the current more will decrease more and more as the battery voltage V1 increases up to the same value as the power supply output V2.

+Gellert Korpos he charges a LiPO battery in this video not NiMH batterys, they need to be charged diffferently with delta-peak-detection etc...get a seperate charger for them

HIXMF it will discharge at the same rate. sounds like a parallel connection. both connectors can be used to power things up, but obviously, the smaller connector can't deliver as many amps as the bigger one powering your quadcopter

Josh Campbell I think if there is any doubt, keep a close eye on the temperature of the battery. Make sure it never goes above 40ºC.

A lithium ion will blow up.

no, you need the cc. get a cheap ltc3780 from china.

Don't do it. You can limit the voltage but the current will be to high for your battery. The maximum charging current rate is 1c for lithium batteries which is the capacity of your battery.

25C is the maximum discharge rate

Tsnafu Ah, makes sense, thanks :)

Afrotechmods Please recommend a cheaper multimeter!

Thisis Myname check out EEVBlogs multimeter shootouts.

OhNoNotMyPenis I would love to buy a Fluke but I don't use my meter enough to justify it.

ThisIs MyName See his Multimeter Tutorial video. He has a meter he recommends.

Sure

I wouldn't bother with the 1.9V and 0.9V ones, they are dead. Recycle them.

not sure how low but you are suposed to be able to charge them below 3V. The thing s the chemistry doesnt like that and so you have to get it about 3V with a really small charging current(say 0.05C for a long time (a few hours at most depending on the conditions). Once it's above the safe voltage you can continue charging it as normal, though the capacity wont be the same in case it stood to long in that state.

Laharl Krichevskoy some times you can revive a pack by charging it in NiMh mode up to 3volts but not recommended some high end hobby chargers have a Li-po LV recovery mode my Powerlab8 can do this

I picked up a nice Nitecore D2 multi-chemistry from Edisonbright (via amazon) for $15. I had a battery from an old laptop that was dead that I pulled apart, 2 battery pairs were around 3.1V and one was 2.1V. I just put the paired batteries in the slot and they all went to 4.2V and seem fine now.

ZauStuv The 4V would be the "termination" voltage. If you charge to 4V you will only get e.g. 80% capacity. You should still charge at constant current until you reach termination so the battery doesn't overheat.

Afrotechmods All right. Thank you for the help.

look for 3s bms

Yes, but the cells will need to be balanced every five to ten cycles.

you could make yourself a linear regulator with constant voltage and current, though they are quite inefficient (as in medium/big heatsink, something like for the computer at most), better use a 5 or 6V psu for that to lower the losses. a lm317 for the regulation and a few transistors and resistors to regulate the voltage and current should do fine.

I can't tell if you are trolling or not. If you are, well played. If you are serious, please don't ever do that again, you are going to start a fire.

no trolling here, just been charging my e cigg battery with an old cell phone charger,, figureed they were the same, (so i need to add a power limiter to the mix? )

ty for your response too, ill try to remedy this problem today..

another quick question,, should i just find a 3.7v-4.2v charger? or add some kind of power limiter to the one i already have.? (thank you for your time)

okay i found a really cheap charger for like 3$ ( thank you for your information.) prolly saved me alot of trouble when it did decide to finally blow,

it's safer to charge with less current

Keziolio Yes, and it can increase the cell's lifespan.

thra5herxb12s As long as the battery doesn't get too hot, it shouldn't be damaged.

I'll keep an eye on it. Cheers.

thra5herxb12s Afro suggested 40ºC as the maximum temperature.

I'll make a proper charging station with a usb type cooling fan. I'll post up a vid of it.

If you want safe batterie life, then don't charge it up to 4,2 V. Instead use 3.95 V as upper limit.

arthurthegreat Yes. Easily.

***** Actually that's not quite correct as well. If you see the battery as an ideal voltage source with a resistor in series to it (that's a common model) you can see that the current directly depends on the voltage difference between the charging voltage and the battery voltage (if you disconnected it): I_charge = (U_charge - U_battery) / R_battery. Where R_battery is the internal resistance of the LiPo. As an example for a rather low capacity LiPo R_battery could be around 0.1Ohm (that's the point where you shouldn't quote me ;) ) which is discharged to 2.8V you would get (4.2V - 2.8V)/ 0.1Ohm = 14A.

***** No not infinity, but a very large current. Only limited by the cells resistance, and the chemical reaction which takes place, when charging the cell. This is a 25C cell, so i suspect the charge current without a current limit will be likely in that region or more. Which will heat up the cell very fast, thus destroying it, leading to bloating (H Gas will be created inside the cell) and eventually rupturing and igniting the venting H gas.

***** lipo batteries have a low ESR, so they will take a lot of current in one go if you dont limit them, most probably more than your psu can take and hence burning it. Also, with current comes heat, and lipo and lithum batteries in general arent really fond of temperatures above 40ºC. Lithium is quiet a reactive metal, dont heat it, and dont expose it to air. The same reason goes as to why you shouldnt short circuit lithium batteries. even small cells like that one can deliver a lot of amps in short circuit easily causing a fire, add to the fact that these cells dont like heat, and you have a thermal runaway the palm of your hand. (btw see the battery says 25C, that means it can deliver 6A (0.240x25) under normal load (keeping its voltage), many more in short circuit. Afro forgot to say that if it says 25C you can also charge it at 2C instead of 1, though it depends on the quality of the cell, but usually. 2 or 3C for 25 50C cells tends to work fine though you need to be careful about heat as i said)

If you want to charge a battery very fast, than buy a Lithium Titanate battery They take very rapid charging rates with high amps easily.

You'd want 8.4V max voltage for 2 cells.

Thanks! +afrotechmods

tu peux connecter les 2 cell en paralle . apres tu les charge avec 4.20V . parce que les Lipos ne doivent pas se charger en série

If you had 2 cells in parallel, could you charge it safely with 2C at 4.2v?

DaffyDaffyDaffy33322 Yes

Your LiPo should never have been allowed to drop below 3.0V in the first place. Dropping significantly below that can permanently destroy its capacity. Don't try to charge it or use it in any way - it is dead and needs to be safely recycled.

Afrotechmods if I shorted by mistake the battery pins when trying to measure the voltage it could explain the voltage drop so low?

Irvin Yip yes, easily with a 4.2 voltage regulator (not sure if it exists), filters and a small resistor in series to limit the current

D probably means data. Cameras sometimes have little communications systems with battery packs to verify you are using a "genuine" battery pack.

That was my guess also. It seems to be a 'no go' on finding a video, (or any forum) I've tried so far that will give me the answer.

10C is not uncommon. it's just a safe figure

Double check what your battery can safely be charged at. I showed 1C in this video so it would be safe for everyone to try.

Just because speed chargers do that, doesn't mean it's a good idea. 1C is the safe bet that all Lipos should be able to take. If you want to use higher C rates check the datasheet of your exact battery. If you haven't got one, like with most cheap batteries, stick with 1C.

superdau Hmm yeah, I only see people speed charging branded Li-Pos, not unbranded ones..

The higher the charge current, the lower the charging efficiency. A battery which is charged with 10C gets really hot during charging. Not the best thing for a long battery life

Yes. Max 1.5A, minimum can be anything lesser than that

11.1v is the nominal voltage. the cells charge to 4.2v each. you have 3 cells. 4.2x3