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Greetings. I have this problem. I have a telephone that requires 3 AAA cells. I installed 3 AAA dry cells. it works good. LCD display is very sharp and bright. But then i thought. one day that the dry cells will surely get over and I will have to buy new ones. So instead of replacing new dry cells what if i install rechargeable ones. So i opted to buy 3 AAA NiMH cells.

I had always known that dry cells are rated at 1.5 volts whereas NiMH cells are 1.2 volts. I had understood that it doesn't make much difference.

After installing the NiMH AAA cells the lcd display was about 20% dimmer than previously seen. It clicked me that 3 NiMH cells will lead to a loss of 0.9volts in total. thats like 1 volt drop.

So i have few questions here.

Was my idea bad ? If we compare 6 Dry cells vs 6 NiMH cells then there is a voltage difference of whopping 1.8 volts. dry cells 1.5v x 6 = 9v NiMH cells 1.2v x 6 = 7.2v

Which means we need to consider atleast one more NiMH cell, isnt it. So 7 NiMH cells will be somewhat at par with 6 Dry cells. (there would be still a difference of 0.6 volts.

Am i right with all these ideas?

So how do i solve the dim lcd in my telephone. i am still short of 0.9 volts.

can i simply add one more NiMH cell in series. I would have to engineer a slot for it in the phone.

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  • \$\begingroup\$ NiMH cells are usually not charged when delivered new. You have to charge them first. \$\endgroup\$ – Turbo J Aug 2 '17 at 17:12
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Just let it be dim. The average voltage of an alkaline battery is something like 1.3 Volts during discharge. The range is 1.55 down to maybe 0.9V

The average Voltage of a NiMH battery during discharge is around 1.2V. From like 1.35 down to 0.9.

These are just typical numbers. Some devices may cut off at higher than 0.9V or lower. But the main point is that batteries don't have a single voltage. They have a range as they progress from fully charged to discharged. Comparing NiMH to Alkaline, the top of the range is a bit different. The average is less different. And the end of the range, on the discharge side, is about the same.

So just use your NiMH batteries unless the dimness really bothers you.

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