Computers & Electronics

Replacing 4 x D cell with 2 x 18650 rechargeable cells

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  • Jul 11th, 2020 5:38 pm
[OP]
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Jul 26, 2008
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Montreal

Replacing 4 x D cell with 2 x 18650 rechargeable cells

I recently got an old style radio that uses 4 x D cells. My original D cells ran out after 4 months of usage so was looking on ebay to find some gizmo adapters.

finally I ended up making something myself.

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Thread rod, with bolts ans washers, 18650 protected cell so cuts of after volt drops at cutoff inserted in PVC pipe.

All I need now is just a bit of foam to keep the 18650 battery centered in PVC pipe.

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Measure voltage is 8 volts, I am 2 volts above original original D cell voltage. Side of radio has DC power plug that read 7 Volts I guess I am only 1 volt above operating spec will this damage the radio long term ? time will tell, its running fine now. and I don't have to reorder D cells.
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Jan 21, 2018
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Most electronic components in that sort of consumer device would be rated at 5v nominal operating voltage, but with a fairly wide margin. Lithium ion cells are rated at 3.6v nominal voltage, so you're actually probably running at about 7v. I don't think you're in any danger of problems.
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OP you’re a genius.
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cool!

Panasonic makes C & D adapter for their AA eneloop batteries (comes in the battery kits - see pic below) - but yours is cooler since you are using 18650 batteries!

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See if that radio has a DC Adapter input then it should be ok with a higher voltage, as those things have a 1/2 volts of variance at times. Most likely then there would be a Mosfet to do the power conversion and provide stable voltage internally.

But if not, then it may be too much. Many electrical components such as capacitors come with voltage limits. 6.3v is particularly common.

I would suggest adding a step down converter. They are very cheap and very efficient. Like these - https://www.amazon.ca/LM2596-Step-down- ... B008RE3YOA - just the first that I found. Probably cheaper ones avail too

Bonus points: Get a 18650 battery holder - https://www.amazon.ca/Battery-Holder-2x ... B00H8UWGIO - for those batteries and wire em up properly along with a small Li-On charging board.
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ji2o0k wrote: cool!

Panasonic makes C & D adapter for their AA eneloop batteries (comes in the battery kits - see pic below) - but yours is cooler since you are using 18650 batteries!

Image

Image
C and D cells are such failures, the AA have far higher capacity at smaller size.
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Nov 17, 2004
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kramer1 wrote: See if that radio has a DC Adapter input then it should be ok with a higher voltage, as those things have a 1/2 volts of variance at times. Most likely then there would be a Mosfet to do the power conversion and provide stable voltage internally.

But if not, then it may be too much. Many electrical components such as capacitors come with voltage limits. 6.3v is particularly common.

I would suggest adding a step down converter. They are very cheap and very efficient. Like these - https://www.amazon.ca/LM2596-Step-down- ... B008RE3YOA - just the first that I found. Probably cheaper ones avail too

Bonus points: Get a 18650 battery holder - https://www.amazon.ca/Battery-Holder-2x ... B00H8UWGIO - for those batteries and wire em up properly along with a small Li-On charging board.
Typically, capacitors are chosen to be ~2x the nominal voltage. So if the input is expected to be about 6v then a 16v cap is likely used. Of all the common electrical components capacitors are the least reliable so usually they are over speced. Even new capacitors are +/- 30% of it's rated spec.
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Are those Japanese made batteries? This was an eye opener for me:

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Oct 1, 2009
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divx wrote: C and D cells are such failures, the AA have far higher capacity at smaller size.
Such failures?

Sorry (or not sorry) but this post show the lack of clear understanding about batteries and possibly it's history.
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Darn hard to find ANY Japanese made batteries in town here. All the ones so far I have found are made in China, even the Duracells. Used to be we had the ones made in Mexico or Singapore but not anymore. The Eneloops that are made in Japan are good but so are a bunch that I can only assume are available in the U.S. and not Canada. According to these informal tests, the Japanese made ones hold the charge better even after a year of use or storage. Brand names don't mean anything anymore, you need to know where the battery is manufactured and by whom...
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DougO wrote: Darn hard to find ANY Japanese made batteries in town here. All the ones so far I have found are made in China, even the Duracells. Used to be we had the ones made in Mexico or Singapore but not anymore. The Eneloops that are made in Japan are good but so are a bunch that I can only assume are available in the U.S. and not Canada. According to these informal tests, the Japanese made ones hold the charge better even after a year of use or storage. Brand names don't mean anything anymore, you need to know where the battery is manufactured and by whom...
True, and that's not the only problem. Well-known brands like Duracell and Energizer are frequently counterfeited by the usual culprits, so you could be getting cheap junk with a fake label. Check the packaging carefully for known counterfeit indicators if the batteries you just bought seem to be much worse than normal.
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DougO wrote: Darn hard to find ANY Japanese made batteries in town here. All the ones so far I have found are made in China, even the Duracells. Used to be we had the ones made in Mexico or Singapore but not anymore. The Eneloops that are made in Japan are good but so are a bunch that I can only assume are available in the U.S. and not Canada. According to these informal tests, the Japanese made ones hold the charge better even after a year of use or storage. Brand names don't mean anything anymore, you need to know where the battery is manufactured and by whom...
I have 10 year old MIJ Eneloops and Duraloops that are still pulling 1900-2100mAh granted they haven't been abused. My Worse case usage is 8-9A draw on them in a Mag85.
All of my Chinaloops, Duracell 2600mAh Hi-cap(very poor durability), Amazon Basic (PRC & terrible) have all gone to the big battery recycler in the Sky.
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Power Plus Energizer with the bunny on them are made in Japan cells. Every other one so far I've found from Duracell, Rayovac, nonames are all made in China. 18650 ones at Can. Tire are made in China. Energizer batteries and charger that cost $40, both the batteries and charger are made in China. The $25 Energizer batteries and charger combo, the charger is made in China but the batteries are made in Japan. Panasonic AA batteries at Dollarama are made in China. Underpowered also at only 1100mah. Compare that to Duracell AAA rechargeable batteries also made in China, that are rated at 900 mah. Almost as much power with batteries 1/2 the size of an AA. Someone is skimping on chemicals...

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