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Two pp3 nimh 8.4v batterys in parallel ok ?

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curry87

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Can two pp3 nimh 8.4v batteries be put in parallel to increase available mah both rated at 220mah,8.4v and the maximum load is to be around 100ma so should get around 4hrs ?
 
Can two pp3 nimh 8.4v batteries be put in parallel to increase available mah both rated at 220mah,8.4v and the maximum load is to be around 100ma so should get around 4hrs ?
You forgot to tell us the manufacturer of your battery so we cannot look at the datasheet. you should look at the datasheet.

An Energizer 9V (actually 8.4V) battery is 175mAh when its current is only 35mA (1/5th its Ah rating) and when its loaded voltage has dropped to 7V.
With more current then it doesn't last as long as the Ah rate times the time.

We don't know how low the battery voltage is allowed to drop when it is powering your circuit.
 
Uniross 220mah 8.4v nimh battery.

Its going though a (low drop out 0.2v) 5v + voltage regulator so as long as its around 5.3v on the input side its fine in my circuit .

Am i right for saying the voltage across this particular battery made up of 7x 1.4v nimh cells should not drop below 1v per cell so anything below 7v would be damaging for the battery ?


If two of these batteries are to be paralleled how do i get both to have a almost equal open circuit voltage ?

Does it matter if say battery 1 is 8.6v and battery 2 is 8.4v if i parallel them together ?
 
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An 8.4V Ni-MH battery has seven 1.2V cells in series. It is from 9.8V to 10.5V when it comes out of the charger.
When the batteries are connected together their voltages must be exactly the same or a very high current will flow as the highest one charges the lowest one which might kill them or cause an explosion. Simply charge both at the same time then connect them in parallel soon.

If they discharge to less than 7V then the weakest cell in a battery might go to zero volts then as the remaining cells continue to discharge the weakest cell will be charged by the others in reverse which is very bad for the cell.
 
My nimh charger is a dumb charger it does not turn off itself when the batteries are done charging, at a charging rate of 18ma-22ma for a pp3 is there any danger that the battery will be overcharged if left for too long in the charger ?

Whats the unloaded terminal voltage of a nimh cell that has been fully discharged ?

How do you gauge what percentage capacity remaining there is left in a semi discharged nimh battery in order to work out how much time and at what charging current is required to fully charge and not cook it?
 
Here is the data sheet for an Ansmann NiMH 250mA PP3. Check it out. Hope this helps.

I use PP3 NiMH fom various manufacturers...all the same result....

Treat them well...they are ALL brilliant.

First thing: Stop Charge @ 10.15 Volts. Nothing over 10.15V.....ever.
Second thing: Never let them discharge below 7.0 Volts. My cut off is 7.5 Volts.
Third thing: Never let the battery get hot. Despite what the Manufacturers claim. Heat WILL kill the battery.

I have a bunch of batteries that appear to want to last for ever. NiMH UNIROSS was the first. In December last year 2010.
The most used and the most charged/discharged battery. Still good to go for another 200 charge/discharge cycles.

And it's already done around 200 cycles.

I kid you not.

Thank you
 

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