How to make a simple power bank with 8 D batteries and an inverter ?

[GKL]

I ordered a battery holder for 8 D cell batteries to make 12vdc and was wondering if an inverter like they make for cars would work with that to make 110vac for temporary use with various devices, LED lamps, ect. either outside or during a power outage. I was thinking maybe a 200watt inverter like they make to plug into cars to convert DC to 110vac. Can it be that simple or am I missing something ?

 

[gophert]

You are missing the fact 5hat your 12volts worth of batteries has to supply slightly more wattage than you expect to get out of the inverter.
If you need 200w, that means you expect the 12VDC power bank to supply 16 amps. A D-cell alkaline is not intended to supply more than 2amps.

if you limit output to 24W, then it will work but only for 15 minutes to 1 hour (if at all). A load that big drops output voltage to about 11v immediately, and output voltage will drop to 10v in the first 15 minutes and down to 8v by 1hour. Many inverters will kick off if supply voltage sags to 10v.

 

[GKL]

You are missing the fact 5hat your 12volts worth of batteries has to supply slightly more wattage than you expect to get out of the inverter.
If you need 200w, that means you expect the 12VDC power bank to supply 16 amps. A D-cell alkaline is not intended to supply more than 2amps.

if you limit output to 24W, then it will work but only for 15 minutes to 1 hour (if at all). A load that big drops output voltage to about 11v immediately, and output voltage will drop to 10v in the first 15 minutes and down to 8v by 1hour. Many inverters will kick off if supply voltage sags to 10v.

Okay thanks for the reply, it is appreciated, maybe I am misunderstanding the calculator I found on this page: https://www.donrowe.com/power-inverter-faq-a/258.htm#how_long

As that calculator seems to show that 8 D batteries hooked to an inverter could power a 100watt device for 10 hours, or a 7watt LED for over 142 hours. I said a 200watt inverter as a possible choice not that I might really have to have 200 watts. Anyhow, I need to figure if I am understanding that calculator correctly or not.

 

[gophert]

Okay thanks for the reply, it is appreciated, maybe I am misunderstanding the calculator I found on this page: https://www.donrowe.com/power-inverter-faq-a/258.htm#how_long

As that calculator seems to show that 8 D batteries hooked to an inverter could power a 100watt device for 10 hours, or a 7watt LED for over 142 hours. I said a 200watt inverter as a possible choice not that I might really have to have 200 watts. Anyhow, I need to figure if I am understanding that calculator correctly or not.

a D-cell battery has about 12 to 15 amp-hours of capacity. It is commonly called a flashlight battery. Connecting them in series gives 12VDC at (still) 12 to 15 Amp-Hours.

https://d2ei442zrkqy2u.cloudfront.net/wp-content/uploads/2016/03/MN1300_US_CT1.pdf

The online calculator you referenced is an 8D battery, (not 8 D cells). An 8D battery is a big car battery with 160 to 200 A-hours of reserve capacity at 12 volts. Google 8D battery.

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[GKL]

a D-cell battery has about 12 to 15 amp-hours of capacity. It is commonly called a flashlight battery. Connecting them in series gives 12VDC at (still) 12 to 15 Amp-Hours.

https://d2ei442zrkqy2u.cloudfront.net/wp-content/uploads/2016/03/MN1300_US_CT1.pdf

The online calculator you referenced is an 8D battery, (not 8 D cells). An 8D battery is a big car battery with 160 to 200 A-hours of reserve capacity at 12 volts. Google 8D battery.

Duralast Gold Battery H8-DLG Group Size 49 900 CCA

Shop for Duralast Gold Battery H8-DLG Group Size 49 900 CCA with confidence at AutoZone.com. Parts are just part of what we do. Get yours online today and pick up in store.

www.autozone.com

Wow, that explains it, thanks !

When I was doing an online search for ideas about using 8 D cells as a power bank with an inverter I didn't expect there to be a car battery called 8D that would come up in the results so you can see how I misunderstood.

No problem though, I can always use the 12vdc from the 8 D cell battery holder with 12v devices and 12v LED lamps.

(I used to work in electronics in the Navy in the early 1970's, guess I've been away from it so long I got a little rusty )

 

[gophert]

Wow, that explains it, thanks !

When I was doing an online search for ideas about using 8 D cells as a power bank with an inverter I didn't expect there to be a car battery called 8D that would come up in the results so you can see how I misunderstood.

No problem though, I can always use the 12vdc from the 8 D cell battery holder with 12v devices and 12v LED lamps.

(I used to work in electronics in the Navy in the early 1970's, guess I've been away from it so long I got a little rusty )

Welcome to the site - there are some other Navy Electronics vets here from your era. Stick around, buy some parts, melt some parts or let the magic smoke out of them and ask plenty of questions. We're here to laugh with you and answer questions.

 

[GKL]

Welcome to the site - there are some other Navy Electronics vets here from your era. Stick around, buy some parts, melt some parts or let the magic smoke out of them and ask plenty of questions. We're here to laugh with you and answer questions.

Thanks, I should check back occasionally for info and with questions, I've always been an electronic gadget person, though my wife might tend to jokingly refer them as my toys

 

[audioguru]

Power banks and car starters use a modern rechargeable lithium battery, not a bunch of old D cells.
Do Tesla cars run on old D cells?
Does anybody sell old D cells any more?
Does anybody sell the old incandescent bulbs that were used in old flashlights?

 

[GKL]

Power banks and car starters use a modern rechargeable lithium battery, not a bunch of old D cells.
Do Tesla cars run on old D cells?
Does anybody sell old D cells any more?
Does anybody sell the old incandescent bulbs that were used in old flashlights?

I understand your point, I wasn't really looking for a super duper power pack, just something to run some low power devices and/or LED lamps either for outside use or for inside when there might be a power outage.

They do sell D cell batteries, and holders too, the holder I ordered that holds 8 D cells to make a 12vdc power supply I guess I'll use as is without an inverter, and use to power 12vdc devices and/or dc LED lamps during a power outage or outside.

For example, one outside use is when I want to use a 12vdc tire inflator to add air to the tires on my lawn tractor, it would be much easier to run it off a D cell power bank than trying to drive the lawn tractor close enough to my car, have to turn on the car, plug in the inflator and try to reach all the tires, and that is just one example.

 

[Visitor]

Does anybody sell old D cells any more?

Does anybody sell the old incandescent bulbs that were used in old flashlights?

No, I doubt anybody sells old D cells. But anywhere that sells batteries sells new D cells.

Same with incandescent flash light bulbs. New bulbs are still for sale. Probably at Canadian Tire.

 

[GKL]

No, I doubt anybody sells old D cells. But anywhere that sells batteries sells new D cells.

Same with incandescent flash light bulbs. New bulbs are still for sale. Probably at Canadian Tire.

I actually have some old flashlights laying around that use the old bulbs but I haven't used them in a good while since LED flashlight have gotten more affordable.