Xtar BC8 AA / AAA ( Li-ion charger )

[old4570]

Also , Li-ion AA and AAA …. Should be interesting !
Only came yesterday , only started charging batteries today .
As can be seen in the picture I am starting with AAA . I really want to see if the BC8 pushes the AAA too hard , ( 0.5A constant current ) .

Oh , those Li-ion (?) As they came , they were all 1.5v ( measured ) .
I am currently discharging one of the AA in a flashlight , then I will charge it and do a discharge for capacity . I think the label says 3300mWh

How much is mWh in mAh?
Most people are used to seeing mAh ratings , they see the "2800" and go "wow, look at the capacity". The way they get the mWh rating is by multiplying the 3.7V nominal lithium cell voltage by it's actual mAh rating. So if we reverse this, 2800mWh/3.7V = 756mAh. Or in this case 3300mWh/3.7V = 892mAh …

Just how interesting will these Li-ion batteries be ?

 

[hamhanded]

Are those be standard 3.7v Li-ion cells with built-in buck circuits that output 1.5v?

 

[fivemega]

Or in this case 3300mWh/3.7V = 892mAh …

In fact, you suppose to get 1.5V out so:
3300/1.5=2200 mAh or 2.2Ah

If you test it with 1A discharge, you should get:
2.2/1=2.2 hours
2.2x60=132 minutes

Keep in mind 3300 or 1.5 is manufacturing claim and you may / may not get same result.

 

[old4570]

Ok ..........
But that's a variable . To many factors ...
But for the Li-ion battery that's inside ..
Also , a 1A discharge , oh the voltage sag = Not a true result for capacity .

I did a discharge test : To test voltage sag under load .
I tried to video the entire experiment , unfortunately my cheap action cams dont handle the light variables to well .
Doing the 1A discharge , I moved the camera to try and see what was what ( past exp with these cams ) .
So , very unfortunately this is as good as it gets .. I must compare to a NIMH ...

 

[old4570]

Where are we ...
Had some really warm weather .. So just waiting for cooler days . ( Summer )

The charger works well with AA and AAA batteries ( NIMH ) , I have had no issues with the termination voltage and the always good part is that the NIMH are not being cooked by the charger ( getting hot ) . This used to be a thing with some AA chargers , they would literally cook the batteries they were charging . In fact a lot of chargers used to do that .
Even my AAA were staying around the low to mid 30 Celsius range while charging . The AA were at least 5 deg Celsius cooler if not more depending on their discharge state ( Voltage ) . I did find some dead AA in my collection and a few that were down to 0.8v ... The 0.8v batteries were charged and the dead ones went to battery heaven . Some of my NIMH are doing really well and others are failing . The dead ones ? ( Turnigy from Hobbyking ) .. Every year I find one or two that have given up on living . I probably had two dozen Turnigy on account they were so budget .
Back to the Xtar BC8 .. So a 8 bay charger that takes AA and AAA NIMH as well as Li-ion AA / AAA ..
In regards to charging those Li-ion , there is no heat in the batteries during the charge cycle . Cool as can be .
I had to check the VOLTAGE when Li-ion are charged ... Almost 5v
So when the Li-ion AA / AAA are being charged , the BC8 is acting like a Li-ion charger .
Soooooooooo ? Does that mean ? WARNING - Xtar does warn against charging other Li-ion batteries ...
But ? Does the charger behave like a true Li-ion charger ?
Can you charge ( in theory ) a 14500 Li-ion battery ? ( Against Xtars recommendation )
Interesting ..

In anyways , for NIMH charging the BC8 works perfectly fine . For the Xtar Li-ion AA and AAA batteries , they are also charged just fine .
So far there have been no issues aside from the McNasty weather we have had .
I am currently ( Right Now ) discharging a Xtar Li-ion AA for capacity @ 0.2A ...

I did discharge one AA Li-ion @ 0.1A to see how it behaved under load ( light load ) .. I ran the discharge for a little over 10 hours or a little over 1000mAh .. Voltage was usually around 1.43 to 1.42 volts , but periodically the battery voltage would sag .. Early on it would drop to around 1.3 something volts and them climb back up . Towards the 1000mAh discharge the voltage was dipping as low as 1.22 volts and then climbing back up .

Currently doing a 0.2A discharge the battery voltage ( different battery ) has been relatively steady , but slowly decreasing ..
It started at around 1.26v ... Currently we are at 628mAh discharged and the voltage is holding at 1.2 volts even .

 

[old4570]

I was just moments ago trying to work out how to monitor the AA Li-ion charge ..
And I have an idea that will work , I hope ..
I just hope that any extra resistance wont stop the charge cycle ...

 

[old4570]

A) This charger is NOT suitable for recharging li-ion

Let me explain .. The charge current for the li-ion AA from Xtar starts @ 4.2v 0.5A and the voltage slowly climbs higher ..
This would make it unsuitable for charging Li-ion or Lipo batteries .

Oh , and I discharged that AA li-ion @ 0.2A for a 1915mAh result
o.2A discharge
1081mAh / 1.14 volts
1359mAh / 1.17 volts
1477mAh / 1.23 volts
1485mAh / 1.3 volts
1514mAh / 1.32 volts
1604mAh / 1.32 volts
1745mAh / 1.32 volts
1814mAh / 1.32 volts

At first the voltage went down slowly , then began to rise to 1.32 volts and held 1.32 to the end .

 

[old4570]

BC8 Charger charging a AA Li-ion from Xtar ..
Charger starts at 4.2v 0.5A on the depleted battery .. And then the voltage climbs to 4.8 volts and then the current begins to drop and the voltage peaks at some 5 volts .