Building small stereo speaker w/ dual LM386 amp

audioguru · Aug 30, 2009

jivix said:
Audioguru, how does the AC adapter magically route power away from the batteries? If I wire the adapter parallel to the batteries, won't some current be routed through the batteries, dangerously? I will remind you that I have not constructed this yet. It is not a prebuilt stereo that automatically switches between batteries and adapter. I need help making a circuit that will switch between batteries and a DC adapter. Or, I suppose, I could just make a manual switch so I can use either. But automatic would be much neater.

Like I said earlier in this thread, "Most products that are powered from a battery and an AC adapter use a jack with a built-in switch to disconnect the battery when the adapter is plugged in." The switched jack makes it automatic. You can make the AC adapter a battery charger if you want.

Also, I have no idea what you guys are talking about fake "D" cells for... I buy Duracell D's and they are extremely heavy for their size. They are no doubt different from C cells. I have measured the cells with a multimeter and they do output at different current levels. I do not know about other brands, however. Can anyone help me make this thing?

We were talking about Energizer Ni-MH rechargeable D zize cells that have a little AA cell inside. I don't think Duracell sells C and D Ni-MH cells.

For your little amplifier you need six AA Ni-MH rechargeable cells and a charger for them.

bountyhunter · Aug 30, 2009

Radio Shack and many others sold fake D and C cells with smaller batteries inside them. The clue is to look at the mA-hr capacity printed on them and notice they are the same: they used to have sub-C cells in there that were only good for about 1500 mA-Hrs. I believe a full D cell in Ni-CD is more like 4000 - 5000 mA-hrs, and a full C cell NI-CD is about 2000 - 2500 mA-hr.

audioguru · Aug 31, 2009

Energizer and other battery manufacturers do not sell Ni-Cad cells anymore. They sell Ni-MH cells now that have a capacity that is 5 times more than Ni-Cads.

An AA size Ni-MH cell is 2450 to 2800mAh.

bountyhunter · Aug 31, 2009

audioguru said:
Energizer and other battery manufacturers do not sell Ni-Cad cells anymore. They sell Ni-MH cells now that have a capacity that is 5 times more than Ni-Cads.

An AA size Ni-MH cell is 2450 to 2800mAh.

Those must be new technology, the AA NI-MH that came with my camera (and the replacements I bought when they pooped out) were all rated 2000 mA-hr.

bountyhunter · Aug 31, 2009

audioguru said:
Energizer and other battery manufacturers do not sell Ni-Cad cells anymore.

Then who is making all the NI-CDs? Everybody still sells them and I even see them in packs at FRY's. Somebody is making them, maybe not in the USA because of environmental laws, but they are cranking them out someplace. This place sells a lot of ni-cads:

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=47440

Here are some typical AA NI-MH, notice they are rated 2000 mA-hr:

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=90148

There are probably better ones available, these are generic.

This plac has tons of new NI-CADs:

http://shopbatteryhouse.com/nickelcadmium-2.aspx

audioguru · Aug 31, 2009

Sanyo still makes old Ni-cad cells.
Harbour freight sell stuff that they guess on their ratings.

My cheapest Chinese solar garden light has a Ni-Cad cell that is only 380mAh. I have never seen one rated so low.

Building small stereo speaker w/ dual LM386 amp

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Building small stereo speaker w/ dual LM386 amp

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