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05-13-2014, 09:12 PM   #1
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High Voltage Reading On D-Li90 Battery

When charged fully the voltage has measured between 8.5 and 8.4 volts for the past one & half years on this 3rd Party D-Li90 Battery - have maitained a charge & discharge voltage record for all my batteries.
Today it measured 9.36 volts and this is a cause for concern as it may cause problems with the proper functioning of the camera, even perhaps causing havoc to the mother board.
I have been using the same multi meter for the past 5-years with good 9-volt cells in it. I intend taking the battery to the local Electronics Shop for a double check on the output voltage.
The original Pentax Charger D-BC90 is being used. I do not know if this has malfunctioned, and I need to try it out with the original Pentax supplied battery which is in the camera right now.
Now my question is, can a Li-Ion cell charge to over 9 volts from its maximum fully charged voltage of 8.4 volts - nominal voltage is 7.4 volts as indicated on Li-Ion cells, and will this high voltage - 9.36 - cause damage to the camera?
Regards.

05-14-2014, 11:56 AM   #2
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The absolute maximum voltage for a Li-ion cell is 4.2 V. Since the maximum battery voltage is 8.4 V, there must be two cells in series. Half of 9.36 V is 4.68 V, and that is dangerously high. I wouldn't risk handling such a malfunctioning Li-ion battery; they tend to explode when overcharged.

My advice: safely dispose of the faulty battery, and have the charger tested before using it again.
05-14-2014, 05:21 PM   #3
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Good advice from Jens,


I would say however that my understanding is a battery is a chemical device and can only deliver the voltage that physics determines.


Before throwing the battery, have your meter checked, just in case the meter is the faulty item and gave the wrong reading.


Maybe the battery is in fact ok.
05-14-2014, 09:53 PM   #4
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Thanks Jen & Imageman. You guys are a sport - well informed too.
I went to an Electronics R&D Lab manufacturing Automatic Water Control Switches near my home, with the battery, multi meter and the Pentax charger.
The battery measured 8.36 volts - perfect for a fully charged one.
So I am throwing away the Chinese Multi Meter. Now I carried my older US made Multi Meter too. It also needs to be thrown away as it was worse, measured over 10 volts.
Problem solved and the 3rd Party D-Li90 Battery is good - goes back to my camera bag.

An aside: the Pentax original Charger says the Output voltage is 8.4. But the reading at the Lab showed 0.06 volts only. I also carried my Canon P&S Charger
which gave the same result. Why don't these chargers show the actual Output Voltages?

05-15-2014, 04:58 AM   #5
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Im not an expert, and its a long time since I looked at chargers, and I stand to be corrected here, but as I recall the cheaper chargers have a more constant delivery but more sophisticated chargers have a variable delivery determined by the load and the state of the battery. This to among other things prolong the life of the battery


The reason why they don't quote the actual output voltage is I think because it varies over time according to the state of charge of the attached battery during the charging cycle.


I think the charger reading is consistent with a high quality charger under no load so its good.
05-15-2014, 05:11 AM   #6
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I'm glad the battery is OK.

About the charger output: are you measuring without a battery inserted? If so, I'd imagine it recognises the absence of a battery and switches itself off. Most Li-ion batteries have complex electronics built-in, and many of them take partial or full control of the charging process.
05-15-2014, 07:45 AM   #7
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QuoteOriginally posted by Jens Lyn IV Quote
I'm glad the battery is OK.

About the charger output: are you measuring without a battery inserted? If so, I'd imagine it recognises the absence of a battery and switches itself off. Most Li-ion batteries have complex electronics built-in, and many of them take partial or full control of the charging process.
Yep Jens Sir, open circuit voltage. Good idea, I'll insert the battery and then measure the voltage - but first I need to buy a Multi Meter.
While on batteries, all my 3rd Party ones served me well. For $ 5 to 12 shipped they were great buys. In most cases as good as the Pentax original.

Imageman Sir, I have such a Charger for AA, AAA and 9 v cells, that will first dicharge the battery to a safe level and then begin charging. It will switch off automatically after a full charge. It has some diagnostics too - LEDS - that tell you how good the cells are.

My humble thanks.
Regards.
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