battery advice please, does internal ohms matter?

Thread Starter

xtal_01

Joined May 1, 2016
114
I recently finished restoring two old magneto phones from the 20's.

The require two 1 1/2 volt #6 batteries in each. I have been using two d cells in each to test but I want authentic looking batteries in each.

I want to make reproductions. You can actually buy these but at $40 each (I need 4) I think I will try this myself. I also want one to start my model airplane engines.

I was lucky enough to find someone who scanned the outside of a battery from 1925.

I have a body that is 2 1/2" dia and fahnestock clips for the top.

The original batteries were a single cell ... a very large single cell (zinc shell and large carbon rod in the center).

The reproductions you can buy have two D cells wired in parallel.

I can do this or I can fit in 6 C cells (all wired in parallel).

Which is better?

From what I can tell, D cells will supply 18000 mAh ... so 36000 mAh total.

C cells will supply 6000 mAh ... so 48000 mAh total.

I thought about sub c cells but I am not sure if the 1.5 volts vs 1.2 volts will make a difference in these phones (3 volts vs 2.4 volts). Plus since these phones will be used just once in a while for demonstration, the shelf life of alkaline batteries are 10 years ... I am guessing rechargeables will need charging every few months.

Anyway, my question is about internal battery resistance.

I don't know what affect the battery resistance has on a circuit?

I could not find a specification for the resistance of a #6 battery.

D cells have an internal resistance of 200 - 400 milliohms ..... so 100 to 200 if two in parallel ?

C cells have an internal resistance of 150 to 300 milliohms ... so 25 to 50 if six in parallel?

Just looking for some guidance.

Thanks .... Mike
 

Attachments

Something to start with: https://www.ebay.com/itm/Exell-Battery-EBR40-Replaces-Energizer-EN6-Evergreen-HR-40-Rayovac-No-6-/392220161009

https://brooklynbatteryworks.com/ebr40-type-r40-1-5v-battery-en6-ho40-906ac-ignitor-free-shipping/

That's 1/2 the cost you found and free shipping to boot.

Datasheet: http://data.energizer.com/pdfs/en6.pdf

OK, back to your questions. The battery resistance is both a quality indicator and how much short circuit current the battery can supply. Think about the car metric of CCA or Cold Cranking Amps. The larger the CCA, supposedly the better the battery.

Increasing the CCA might also involve making the leakage current higher because the plate shave to be closer together for higher CCA.

Considering, I found you a replacement, you don't have to worry about it.

Parallel batteries are not a good thing in general.
 
Last edited:

crutschow

Joined Mar 14, 2008
23,532
Parallel batteries are not a good thing in general.
Perhaps in general, but I see no particular problem here.
I have a battery operated open gear wall clock that uses two 1.5V alkaline D cells in parallel to power the continuous running motor, and it's been running that way for several years without any problem.
The two batteries last well over a year.

Parallel batteries should work fine here as long as they are identical type, condition, and brand.
You could use either C or D alkaline cells, but I think D cells would have sufficient capacity to last a very long time with infrequent use.
And I see no good reason to use rechargeable ones.
 

Yaakov

Joined Jan 27, 2019
1,604
I recently finished restoring two old magneto phones from the 20's.

The require two 1 1/2 volt #6 batteries in each. I have been using two d cells in each to test but I want authentic looking batteries in each.

I want to make reproductions. You can actually buy these but at $40 each (I need 4) I think I will try this myself. I also want one to start my model airplane engines.
Narrowly, on your question of ESR. This will affect the ability of the cell(s) to provide current on demand. It’s is not otherwise a critical parameter in this case. If your choice of replacement cell is able to provide enough current for your application, the ESR can be ignored.

More generally, these days I might be inclined to use 18650 cells and a buck converter, along with a battery management board.
 

Thread Starter

xtal_01

Joined May 1, 2016
114
THANKS!

I love you guys!

Being a mechanical guy who dabbles in electrical projects, you always come to my aid.

By accident, you actually answered a second question. I have build many dune buggies (both street legal and off road ... I am 56 and built my first one when I was 12). I have been toying with the idea of an electric street legal buggy. Since I will need instantaneous power to "get moving", I now realize the battery resistance will be important in this situation.

I also realize, phone my phone it will make no difference at all.

Just FYI .... I know you can get #6 batteries still but I want ones that look as close to the originals as possible. I could just take a cover and wrap it around a new batter but I have actually gone through the trouble of seeing how the fahnestock clips were attached, figuring out how to make the top look potted, how to age the label, ....

Yes, I am a bit of a fanatic ... just ask my wife ... this is why it took me 5 years to build a house.

I even went through the work of finding the correctly marked receiver and magneto to make the phone as original as possible.

Thanks again so much for all the help!!!!!!!!!!!!

Mike
 

debe

Joined Sep 21, 2010
1,142
Those phones used 2 x 1.5V batterys in series. I used 2 x D cells in series & they last for a year but it does depend on how frequently you intend to use them.
 

Thread Starter

xtal_01

Joined May 1, 2016
114
I completely agree .... I have had two D cells in each (series) for a few months now while rebuilding and testing them ... they still seem fine.

I just want to make a good looking reproduction battery.

With two d cells in each (some decent ones), I am figuring a year or two.

The phones only get used when people come over ... every one wants to try them.

Thanks again !

Mike
 

Audioguru

Joined Dec 20, 2007
11,251
I used #6 dry cells for starting the engines in my control line model airplanes 50 years ago. The Eveready (called Energizer now) cells were American, popular and fresh.
The American Alkaline C and D cells are fairly fresh but are guaranteed for 10 years.

The Chinese #6 cells use old carbon-zinc that might last 2 years and are so rarely perchased that they might already be 5 or 10 years old.
 

Thread Starter

xtal_01

Joined May 1, 2016
114
I also want to make a "spare" battery to put with my model airplane collection (late 60's - early 70's).

I was cleaning out my mom's place last fall and found about 5 cox 049 engines. I got rebuild kits for them.

If I ever get some free time, I would love to try my hand at u-control again!

I found a can of Cox glow fuel (empty ... just to use for display). It would be great to have an original looking battery to go with it.

Thanks !
 

Audioguru

Joined Dec 20, 2007
11,251
I have a few Cox 049's, one 020 and a tiny 010. I also have an Enya .35.
I began RC airplanes about 10 years ago when I was recovering from a heart attack and then 2 stents opening my blocked heart arteries, soon I was fine.
All my RC airplanes are electric Li-PO battery powered.
 

Thread Starter

xtal_01

Joined May 1, 2016
114
Sorry to hear about your health problems but WOW on the planes!

Never got that big ... had an Enya .15 .... not that small either but I always thought they were awesome! Testor made a play in the 049 market at the same time ... had one of their planes and a dune buggy.

I keep looking at electric RC planes.

We have been building a house for 5 years now ... almost done .... I keep telling myself I want to get one to celebrate (thinking I will finally have time to play a bit). I live in VT .... no hobby shops near here (heck, our largest city only had 42,000 people). I have a lot to learn before investing a few $'s.

Mike
 

Audioguru

Joined Dec 20, 2007
11,251
When I was young, radio control was heavy and expensive so I built a few "free flight" airplanes powered with Cox 049 engines.
One airplane flew far into a forest. I had my name and phone number printed on it and it was found 2 years later, the airplane was destroyed by weather but the engine survived. Another airplane flew higher and higher until I couldn't see it anymore but I still heard the scream from its engine that stopped when it ran out of gas. A farmer 40 miles away phoned me to come and get it.

I built an airplane with a pendulum controlling its "angle of attack" like the Boeing 737MAX airplanes. When its nose rose to climb, the elevator went down to level it out. When the nose went down to dive then the elevator went up to level it out. It was fun to try catching it.

Boeing made such a huge error that I THINK THEY ARE FINISHED AS A COMPANY.
 

Thread Starter

xtal_01

Joined May 1, 2016
114
It will be interesting to see if they can survive this. If it can be proven that they were negligent in either the design or in the training they there will be hundreds of law suites.

.... when safety systems become deadly ....
 

Thread Starter

xtal_01

Joined May 1, 2016
114
Funny, I heard that also. I didn't get the complete story whether the system on the plane now was optional or that there was an upgrade that was optional.

It will be interesting when all is said and done to see the autopsy of just who did what.

My understanding is the "fix" is to put in a second sensor and monitor both. If they don't agree, warn the pilot to shut down the system.

We did this all the time in the nuclear industry. If a process was critical, we put in a "safety PLC". Literally, two independent PLC's both getting the same input data and both "should" have the same output data. A third PLC monitored the first two to make sure they agree. The sales engineer said that they even had two independent groups develop the PLC's so they were not identical.

Not sure how much of that is true but that was the sales pitch we got when I worked at Westinghouse Nuclear.
 

Thread Starter

xtal_01

Joined May 1, 2016
114
Thanks!

PS ..... Love your ID "keep it simple stupid"

I drive a 33 year old wreck of a truck for that exact reason ... no computer, everything manual ... I can keep it running.
 
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