[Solved]Measure a battery amps

4.4 would be a problem.

CrossRoads:
4.4 would be a problem.

Understood, thank you and thank you all.
Have a nice day guys

tsunamy_boy:
Understood, thank you and thank you all.
Have a nice day guys

What I'm going to write here may seem a little terse and rude, but I'm trying to get your ATTENTION! Please don't take it personally but this is your life and/or your family's life were talking about.

No, not 'understood' at all. I don't know if realise the implications of '4.4 - would be a problem.' A lipo burns a 2000F and shoots flames up to 6'. Anything within reach that is potentially combustable instantly combusts. That includes your face.

Back in the day lipos got a very bad reputation for causing fires, generally caused by crappy chargers. Lately, most fires are caused by overcharging, or trying to keep using damaged batteries.

How can i get to know the maximum amps of a battery?

The mere fact that you ask question says that you are not an engineer, and are therefore not qualified to 'know' (measure) the A of a battery.

The mAh of a battery is a shell game. It is essentially determined by how many potential -cycles- a battery will have.

The cycles are determined partly by how hard you draw the current, and how far down you run the voltage.

A lipo is fully charged at 4.2V. Notice though that when you buy one brand new it's at 3.65-3.75V. That's the nominal voltage, the 3.7 that's printed on the label. That's what the factory charges the battery to to give the longest life when sitting on a retail store shelf for a year or two.

When they say that 4.2 is the maximum, they mean that anything beyond that risks fire/explosion. (OK 4.25 or whatever but who wants to risk it.)

Beyond 4.2 the battery doesn't necessarily immediately go 'poof.' It starts to get warm, probably it puffs, the chemicals degrade, it gets hotter, there's a thermal runaway and -then- it goes poof. The only lipo fire I ever saw personally was a 'moderate impact' helicopter crash. walking over to it, and then looking for a bit, it had to be somewhere between 1 and 2 minutes before it actually caught fire, 3' flames. A multicell battery fire can -appear- to go out, then catch fire a minute later as another cell catches.

These numbers aren't cast in stone either. Manufacturers vary, chemistries vary, production processes vary. Stay on the safe side of all the numbers and you'll have the best chance of not suffering a disaster. But the reason I'm being LOUD about all this is that so far you're playing on ALL the UNSAFE sides of the numbers.

The point being that once you go past 4.2x, or give it a severe shock/impact, you're holding a grenade in your hand, the pin is pulled, you just haven't released the yet. But the the detonator is not under your -control-, it's a chemical reaction that will light up sooner or later.

...i just discharged a Lipo Battery completely (0v now)

BTW you just destroyed the lipo. Yes there're potentially ways to 'revive' them but it is severly damage, will have a drastically shortened lifespan, and every time you charge it you're playing 'pull the pin on the grenade and see if it lights up this time.'

Ok, so after a lipo battery charging, if the battery is low than 4.2V, this means that the battery is not fully charged right? So in other words, it will not overcharge if i keep charge it the same way over and over?

Not necessarily, and probably not, because you haven't mentioned what you're charging it with, also given some of the treatment you give them such as discharging down to 0V. A damaged battery -may- not have the ability to be fully recharged to 4.2. The fact that it won't go to 4.2 -may- be a sign of damage. A reputable charger, first, won't let a battery charge past 4.2, and if it doesn't reach 4.2 won't let it charge past a certain time limit.

The C rating of a battery is not cut and dried. Again, it is a shell game number picked by the manufacturer to get an 'OK' number of cycles from the battery by the average consumer. 100 cycles is generally assumed to the target cycles. (As was mentioned, manufacturers don't publish -real- specs.) You can, for instance, discharge a 10C battery at 20/30/40/whatever rate you want, but it may work only 20 or 5 times, or only once. OTOH I've heard of rare instances of mocel aircraft catching fire in flight because they pushed a battery too hard.

Battery usage isn't supposed to be measured by mA, it's supposed to be measured by V. The 'ABSOLUTE maximum discharge' is -generally- touted at 80% or about 3.4V. But, that will give you the fewest usable cycles. One fellow I read about, whose -job- it is to manage battery systems, said he got -600- cycles by dischargong to the nominal 3.7 / 50%.

Regardless the topic really was about charging. You didn't mention what size batteries you're using. Common consumer toys come with a charger, and shouldn't be messed with by either using a different charger or using the charger on other batteris unless you KNOW what you're doing. Here's a good reference about overcharging and the 4056. RC Groups - View Single Post - Syma S107 battery upgrade

One more BTW. NEVER leave a charger unattended. There was a story this past Xmas about a new toy, got used a few times in the morning, and was left on the charger while the family went out. They came home and the house was burned down. It was -probably- a 10-15 minute charger, that -probably- had a warning label on it that said 'do NOT leave on charge for more than one hour.' Misuse = 'poof.' Junky charger = 'poof'

I ended up building my own lithium ion charger circuit using simply 5v, arduino powered.

I think there was a misunderstanding and the OP connected his meter set on Amps directly across the battery.

jbarchuk:
The point being that once you go past 4.2x, or give it a severe shock/impact, you're holding a grenade in your hand, the pin is pulled, you just haven't released the yet. But the the detonator is not under your -control-, it's a chemical reaction that will light up sooner or later.

Ok, i'm scared now!!
So by this, tell me what's the best way to charge a lipo battery.
I've followed this topic: Battery charger - General Electronics - Arduino Forum
Do you think i'm ok with that?

cjdelphi:
I ended up building my own lithium ion charger circuit using simply 5v, arduino powered.

It looks scary for me :stuck_out_tongue: do you have a schematic and the source that you can share with this community?
It would be awesome.
Also tell me, can you charge any kind of lipo battery (i have an idea that each mA need a different situation)?

polymorph:
I think there was a misunderstanding and the OP connected his meter set on Amps directly across the battery.

Well, yeh :astonished:

tsunamy_boy:
So by this, tell me what's the best way to charge a lipo battery.

The way the -battery- -manufacturer- says to, for the part number printed on the battery. Wikipedia lists 24 different 'lithium' chemistries. Lithium is the family name -lithium ion and lithium polymer are not necessarily synonyms. Voltages and charge/discharge characteristics vary DRASTICALLY.

I've followed this topic: Battery charger - General Electronics - Arduino Forum
Do you think i'm ok with that?

That looks like the straight dope.

MAX1811 is easy to use for a LiPo.
Here I used one to charge a 1000mAH LiPo in my RF remote control.
I used 3AA battery pack for development, then connected the LiPo when I get the other parts in.
Has been running since ~Jan 2011.

jbarchuk:

I've followed this topic: Battery charger - General Electronics - Arduino Forum
Do you think i'm ok with that?

That looks like the straight dope.

Why :cold_sweat:

CrossRoads:
MAX1811 is easy to use for a LiPo.
Here I used one to charge a 1000mAH LiPo in my RF remote control.
I used 3AA battery pack for development, then connected the LiPo when I get the other parts in.
Has been running since ~Jan 2011.

Do you have the need to setup resistors based on the amps that your batteries have?

No. Lower left resistor is there to set Enable High or Low depending on whether external power is available. Upper right resistor is there to limit current to the charge indicator LED for brightness control.
Pins 1 & 2 determine whether it charges to 4.1V or 4.2V, and at 100mA rate or 500mA rate.

CrossRoads:
Pins 1 & 2 determine whether it charges to 4.1V or 4.2V, and at 100mA rate or 500mA rate.

The IC does that automatically?

CrossRoads:
(...) at 100mA rate or 500mA rate.

This means that i can't charge a battery bellow 100mA or above 500mA?

tsunamy_boy:

CrossRoads:
Pins 1 & 2 determine whether it charges to 4.1V or 4.2V, and at 100mA rate or 500mA rate.

The IC does that automatically?

CrossRoads:
(...) at 100mA rate or 500mA rate.

This means that i can't charge a battery bellow 100mA or above 500mA?

Yes, and yes.

Yes, the chip controls the level.
100 & 500mA are the rates supported by this chip. USB as the current source.
I suppose if the source can't supply that much, it will use whatever is available.

retrolefty:
Yes, and yes.

Thank you :slight_smile:

CrossRoads:
Yes, the chip controls the level.
100 & 500mA are the rates supported by this chip. USB as the current source.
I suppose if the source can't supply that much, it will use whatever is available.

Thank you, is there any other chip like that that can handle until 1Amp?

Don't know. Search "battery management" at www.maxim-ic.com
or www.maximintegrated.com
My chrome is having a hard time connecting to maxim right now for some reason.

This will do 1A, need to have the exposed pad connected for cooling.

CrossRoads:
This will do 1A, need to have the exposed pad connected for cooling.
http://www.digikey.com/product-detail/en/BQ24090DGQT/296-25863-1-ND/2237301

If i understood it charges batteries at 10mA min and 1000mA max right?

What does this means: "Pin Selectable USB 100mA and 500mA" cuz i'm confused about this

Read the Pin Functions on page 7:

ISET2, pin 7:
Programming the Input/Output Current Limit for the USB or Adaptor source:
High = 500mAmax,
Low = ISET, (another pin, see below)
FLOAT = 100mA max.

ISET, pin 6:
Programs the Fast-charge current setting. External resistor from ISET to VSS defines fast charge current value. Range is 10.8k (50mA) to 540 ? (1000mA).

Also read more about these 2 pins on pages 18, 19.

CrossRoads:
Read the Pin Functions on page 7:

ISET2, pin 7:
Programming the Input/Output Current Limit for the USB or Adaptor source:
High = 500mAmax,
Low = ISET, (another pin, see below)
FLOAT = 100mA max.

ISET, pin 6:
Programs the Fast-charge current setting. External resistor from ISET to VSS defines fast charge current value. Range is 10.8k (50mA) to 540 ? (1000mA).

Also read more about these 2 pins on pages 18, 19.

And i have to calculate a resistor to different battery amps right?

tsunamy_boy:

CrossRoads:
Read the Pin Functions on page 7:

ISET2, pin 7:
Programming the Input/Output Current Limit for the USB or Adaptor source:
High = 500mAmax,
Low = ISET, (another pin, see below)
FLOAT = 100mA max.

ISET, pin 6:
Programs the Fast-charge current setting. External resistor from ISET to VSS defines fast charge current value. Range is 10.8k (50mA) to 540 ? (1000mA).

Also read more about these 2 pins on pages 18, 19.

And i have to calculate a resistor to different battery amps right?

Yes