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How to recharge a fully flat lipo (lithium polymer) battery



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okay now here's a situation that I sure

most people have found themselves in at

some stage you've got yourself a lipo

battery but you've discharged it too

much and suddenly when you try to charge

it go through lipo battery and lipo

balance here we go we wait and the

charger then says low voltage low

voltage what this is telling us make us

stop speaking what this is telling us is

that the voltage of the battery is too

low to be safely recharged because if

you just sort of poor current into this

thing it could go bang and that's not a

good look because as we know lithium

batteries can be quite pyrotechnic in

nature so what do we do well there is a

way to get around this the first thing

is unplug your balance lead then select

NiCad battery NiCd and make sure you use

the lowest possible current setting it

so it's point 1 amps it's as love as

this charger will go then start the

charge like so and you'll see it was

down to 6 points 3 volts which is way

way too low however if the battery

wasn't left too long in this state you

may be able to recover it it's quite

amazing how resilient sometimes they are

what I'm going to do is charge you this

very low current until the voltage gets

up to around about 10 volts or near

enough to it once we've got over 3 volts

roughly in the peg then we can switch to

the lipo charge but again we need to

charge it very gently just in case there

has been some kind of damage caused by

the over discharge so I'm going to leave

that take an ABC the voltage comes up

pretty quickly don't leave it ticking

over until it reaches say and nine point

nine nine point six volts which is three

point two volts per cell

right now as you can see it's reached

9.6 volts it only took 14 milliamps to

get there and it took about nine and a

half minutes so what you do when you get

to that stage is you stop your charge

you go on to lipo select balanced charge

and make sure that your current is right

down at 1c or even less don't charge any

more than that plug your balance leg

back in and then start your charge and

it should successfully start charging

you go now one thing to watch is just

look at the individual cells make sure

that they're pretty close this isn't too

bad but they're all 3.2 ish yep so that

looks like we haven't lost one

particular cell sometimes you'll lose an

entire cell when you over discharge but

this one but it could call the battery

the Lumineers and so it seems that it

survived this what I'll do now is I will

completely charge it and then we'll see

how many milliamps it took to fill it up

you see the voltage is coming up pretty

quickly now so important though do not

leave this unattended at any stage of

this process because if the battery has

been fatally damaged it could catch on

fire as you all know lipo's go bang

flames come out so do not leave this

unattended make sure you do your

charging on this is a concrete floor so

it's even if it does go up it's not

going to set stuff on fire very

important so we'll come back later when

this battery is fully charged and see

how much of the 13 hundred milliamps

we've been able to put back into it okay

so there we go we've got fall didn't

take the full 1300 milliamps it took

seven four minutes but I think the soul

seemed in here this isn't quite

calibrated Robin there's no obviously no

really weak cells you didn't take too

long to balance the pack itself is a

little bit it's not hard there's a

little bit of puffing in there which is

kind of expected if you run them deep

flat that's really sort of it does cause

damage now this was overnight because I

left it plugged in didn't realize it

came

the morning it was dead flat so and if

you if you do flatten a battery below

the safe charging level then as soon as

the battery is cool if it's warm that's

when you want to stick it on the charger

and bring it up like that don't leave it

every hour you leave it contributes to

the damage that's taking place inside

the battery now this one obviously I

wouldn't be using it for

mission-critical applications it's

probably got high internal resistance

now which means it will get hotter tend

to puff more if you use in a high

current application however it'll

probably work just fine in low current

applications like you if P V goggles or

some other thing that you know doesn't

draw tens of amps this Batchelor

probably continued to provide a good

long service life but do keep an eye on

it never charge it unattended because

once the damage sits them and then it's

far more likely to cause a problem later

on but there you go

so you can rescue a lipo and if you do

it quick enough you may get away without

any damage this is suffered a little bit

of damage but it will still be a useful

lipo although I'm going to mark it with

a big back cross to remind me that I

just take extra care with it if you've

got questions comments on this video

stick them in the place provided by

YouTube sorry about the audio because

I'm just using the built-in camera mic

and it'll be all echoey as hell bye for

now