my first rechargeables from aw

[foxracer72]

i just ordered some aw rechargeables from aw, 18650s and some r12s along with a pilia charger, i was wondering if there is any sort of break in i should do, and should i charge them when i get them, also would like to know how to get the longest life from my batteries. any help would be much apreaciated

 

[DM51]

They will arrive charged to 4.00V, and you can use them straight away. There's no break-in or conditioning to do with Li-Ions.

If you don't have a DMM (multimeter) you should get one. The great thing about Li-Ions is that you can tell the state of charge by the voltage. Don't let them run down to empty (3.6V) and they will last you a long time. They prefer being topped up after each use than run down to empty.

The Pila charger you have ordered is an excellent choice.

 

[Flashlight Aficionado]

If you don't have a DMM (multimeter) you should get one. The great thing about Li-Ions is that you can tell the state of charge by the voltage. Don't let them run down to empty (3.6V) and they will last you a long time. They prefer being topped up after each use than run down to empty.

Which DMM is recommended? Only to be used for checking cells.

 

[DM51]

Any will do, as long as it is reasonably accurate. Mine is a Fluke, but they are not cheap. There are some perfectly good reasonably-priced ones. It is one item of equipment you might consider buying at a B&M store, where you can try it out and have the functions explained to you by someone with a knowledge of electricity/electronics.

 

[Flashlight Aficionado]

:thanks:

 

[DM51]

Here is a useful table which illustrates what I say in post #1. Bear in mind the figures below are resting voltages, where the Li-Ion cell has been resting (not under load) for ~15 minutes. The figures are approximate, but they are a good guide.

4.2 volts 100%​

4.1 about 90%
4.0 about 80%
3.9 about 60%
3.8 about 40%
3.7 about 20%
3.6 empty for practical purposes
<3.5 = over-discharged

 

[RocketTomato]

Here is a useful table which illustrates what I say in post #1. Bear in mind the figures below are resting voltages, where the Li-Ion cell has been resting (not under load) for ~15 minutes. The figures are approximate, but they are a good guide.

4.2 volts 100%​

4.1 about 90%
4.0 about 80%
3.9 about 60%
3.8 about 40%
3.7 about 20%
3.6 empty for practical purposes
<3.5 = over-discharged

Thanks for the useful info. I am confused though , I thought that Li Ion cells were rated 3.7 V, but apparently they spend most of their life >3.7 V? I am guessing this is a difference due to whether or not it is under load?

 

[DM51]

I thought that Li Ion cells were rated 3.7 V, but apparently they spend most of their life >3.7 V? I am guessing this is a difference due to whether or not it is under load?

Correct. When a cell is under load, i.e. when current is being drawn from it, the voltage "sags", typically 0.5V. The cell is therefore delivering ~3.7V. This is a nominal figure, and it obviously depends on how heavy the load is.

When you take the load off, after a few minutes the cell rebounds back up to a resting voltage.

This resting voltage is the one which is an accurate indicator of how much juice is left in it.

 

[foxracer72]

thanks for the help guys, i have a cheap digital multimeater a cen-teck i got from harbor freight that reads im mA, 4 mA=1.5v so whats full charge 10mA? should i invest is a better multimeter? is there a multimeter that well display in volts? :thinking:

 

[DM51]

LOL, that sounds like a disastrous meter, and you could end up dead-shorting the cell or worse. It should have a scale in VOLTS (DC).

Do not measure milliamps, amps or anything else across a cell like this with no circuit.

I think you definitely need a new meter!

 

[foxracer72]

ok so a new multimeter is in order, lighthound has a zts mbt for $70 is this what i need or can i get one at my local home depot? also i bought a Dereelight DBS V2 w/ 3SD Cree XR-E WC Q5 (SMO) it says it has a safety feature:Shut down at 2.7V to protect lithium battery from over-discharging. isnt that over discharging the battery or is that ok because it is under load?

 

[DM51]

The ZTS battery tester is very good for primary cells and some rechargeable chemistries, but for Li-Ions you really just need a straight voltmeter. Get one at Home Depot or wherever, and it should be OK as long as it isn't a real cheap piece of junk.

The 2.7V shutdown is to stop severe over-discharging. It should rebound from that to >3.0V which is OK, but not as good as >3.5V. You should never rely completely on low-voltage protection.

 

[Mr Happy]

LOL!

There's nothing wrong with the Cen-Tech meter.

The 4.0 mA/1.5 V reading is the battery test setting. It puts small load on the cell and measures the current. A fresh 1.5 V battery will read about 4.0 mA. A fresh 9 V battery will read about 25 mA.

You don't want to use the battery test setting for measuring Li-ion battery voltages. Use the 20 V DC setting (DC V ranges, 10 o'clock on the dial) and read the voltage directly off the display.

 

[precisionworks]

The Fluke 179 is one of their less expensive meters, about $160-$170 new, sometimes half that used on eBay. It's the meter I use in my home shop. My 'work' meter is the 87V, but with a $250+ price tag.

The reason that so many electricians & electronics technicians use Fluke is their toughness + reliability. Probably overkill for home use, but you'll get most of your money back when the time comes to sell it.

 

[Mr Happy]

The thing about the Cen-Tech meters is they are essentially disposable. I bought a bunch of them at $2.95 each. You can put one in the car, one in the kitchen, one in the garage, have one to lend out, and have a few spares too.

I have tested the meters against the readings of more expensive ones and the accuracy is fine for home and hobby use. The readings are consistent between meters and against other references. I see differences of up to 4 in the last digit (it's a 3 1/2 digit meter), and this is within spec.

I wouldn't use it for professional purposes, and not around high voltage or high power equipment, but for measuring low voltages and currents in battery powered equipment it works just as well as meters costing ten times the price.

What would you rather have: a handful of $2.95 meters that you don't obsess over, or a single $250 meter that you are scared of breaking?

 

[Vikas Sontakke]

Where do I buy the Cen-Tech meters from? Do they do 1000mA?

- Vikas

 

[Mr Happy]

The Cen-Tech meters are available from Harbor Freight Tools. The $2.95 price was a special during a sale event. At normal prices they might be as expensive as $4.99. Link to product here.

Similar products are often seen from other suppliers with different branding. Check out especially the various Chinese web sites that specialize in bargain priced offerings.

 

[DM51]

This is off topic from the OP's question. He does not need to be confused right now with current measurements.

foxracer72, to measure the state of charge of your Li-Ion cells, you need the meter set to DC VOLTS. If the meter has that setting, fine - select it. If it doesn't have it, don't use it.

 

[1pt21]

DM51: I just wanted to thank you for this information, very helpful!! I've been looking for this for a while :twothumbs


--Paul

Here is a useful table which illustrates what I say in post #1. Bear in mind the figures below are resting voltages, where the Li-Ion cell has been resting (not under load) for ~15 minutes. The figures are approximate, but they are a good guide.

4.2 volts 100%​

4.1 about 90%
4.0 about 80%
3.9 about 60%
3.8 about 40%
3.7 about 20%
3.6 empty for practical purposes
<3.5 = over-discharged

 

[DM51]

That is a table originally drawn up some time ago by SilverFox, who is the CPF authority on everything to do with batteries - you should thank him!