Rechargeable battery voltage

[basb]

Hi all,

I plan on building a quicky preamp and I'd prefer to use rechargeable batteries.
However, rechargeable batteries are lower voltage and this will result in 2.4v instead of 3v for the filament supply, and 33.6v instead of 36v for the PS.
I was wondering if there will be any adverse effects, either for sound or tubes, by using lower voltage.
Has anyone compared? And what about adding 2 D-cells for 3.6v filament and 34.8v PS voltage?

Bas

 

[Grainger49]

Here is some information:

http://www.bottlehead.com/smf/index.php/topic,890.msg0.html

http://www.bottlehead.com/smf/index.php/topic,166.0.html

Both have information about the batteries, life and rechargeable batteries.  PJ's suggestion for raising the plate voltage is interesting.

I think you need the full voltage on your heaters.  PJ also mentions somewhere that most D cell NiMH batteries are not real D cells (a different amp-hour rating).

 

[Paul Joppa]

The filament supply is dual, independent 1.5v supplies, not a single 3v supply. Just FYI.

1.2 volts is perfectly fine for 1.5-v battery tubes like these. They were designed to work with carbon-zinc batteries, which would produce 1.5v when completely new and fresh, and would drop linearly as they discharge down to (I believe) 0.9v when the manufacturers said they were dead by definition. Alkaline cells work the same, the difference being they have a longer shelf life and last longer. Notice that the average is exactly 1.2 volts! NiCd and NiMH cells have a very flat discharge, maintaining 1.2 volts for almost the full discharge time - so they should work well and much more consistently that primary batteries.

 

[paulw]

As has been mentioned 'D' cellsare really only AA's in a big tube.  True 'D' cell rechargeable

 

[basb]

Thanks for the replies! I didn't notice a lot of D cells are actually big AA's
Will proceed with ordering some 'true' D's, 9V's and ofcourse the quickie!

Bas

 

[Paul Joppa]

Here's a quick calculation:

A pair of full-size NiMH D cells is about $35, and the 2-amp or greater "pro" charger mentioned above is around $110, total $145. Alkaline D cells cost about $1 each, in 12-packs at Costco for example. So that's about a gross of alkaline cells for the cost of one set of rechargeable cells. That's 72 replacement sets, at 200 hours life, i.e. 14,400 hours. If you use your quickie for more than 14,400 hours then the NiMH will pay off. That's not quite two years continuous operation; 5 years at 8 hours per day, every day.

9v NiMH are $15 each, with a $35 charger the total is $95 for a set of 4. 9v alkalines are $14 for 8, so you can get not quite 14 replacements - the break-even point is 2700 hours, 1/5 of the D-cell break even point.