PB 145B/170: Battery does not fully charge

[nvdeynde]

I noticed that my Powerbooks 145B and 170 aren't fully charging their main battery anymore.

The Main batteries are in good condition ( rebuild ), all powerbooks also have a new Pram battery.

The version of Mac OS apparently makes no difference: I get the same results with 7.01, 7.1 and 7.5.3

Charging in sleep mode, powered on or shutdown makes no difference too.

With a drained battery, the powerbook starts charging but already stops after 30 minutes or less with a battery full indicator.

Of course it's not full as the powerbook nearly runs 20 minutes on battery power.

I thought it could be the memory effect of the battery so I repeated the charge and drain cycle several times to no avail.

Leaving it plugged in longer doesn't help either as I have measured the current between the PSU and the DC socket of the powerbook and it no longer charges (<100 ma).

Charging the same battery in an external PB100 charger or in my powerbook 165c takes over 3,5 hours until it's full. Battery capacity is 4200 Mah.

Resetting the Pram settings doesn't solve this issue.

Anyone else with this problem or better with a solution ?

Nico

 

[techknight]

Is the battery capacity the same mAH as the original? this is critical in older systems because they do NOT have "smart chargers" just timed chargers based on the 1/C algorithm.

 

[nvdeynde]

The battery has a much higher capacity than the original. It's made of Panasonic AA Nimh Cells with total capacity of 4000 Mah.

I use the same cells for all my powerbooks and the battery charges fine in other one's. It's definately not the battery.

I excluded the termal sensor in the battery compartment. The battery even doesn't get warm at all when it stops charging after less than 30 minutes.

Also the voltage is on the lower side with 6.2 volts.

When I use the external powerbook 100 charger the voltage goes to 7 volts (= 1.4 volt per cell ), what it's supposed to be. Then I can use my powerbook for about 4.5 hours with all power savings disabled.

 

[techknight]

You didnt specify what other powerbooks.

so therefore, my theory still stands. hasnt been blown away yet... lol.

if the charging circuitry is set to 1/C its not going to fully charge. ever.

 

[nvdeynde]

You didnt specify what other powerbooks.

Same battery used in my Powerbooks 140, 150, 160, 165c and 180c. They all charge the battery fully as far as I can tell.

If a powerbook 165c with 3A PSU takes about 3.5 hours to charge a drained 4000 Mah battery, I assume it will be very close to full.

I think the charging circuit charges the battery to a predetermined upper voltage limit ( About 7 Volts ), that's how classic chargers work.

If the charging circuitry takes a wrong reading of the battery voltage ( on the high side ), then it never gets charged fully.

Anyway, even the original powerbook battery with I agree a lower capacity can't be fully charged within less than 30 minutes.

So the charging circuitry must be faulty. I don't have much hope this can be repaired.

 

[techknight]

hm.. that is strange. Almost like there isnt enough load to determine the proper charge level of the battery? that is odd.