Working on an external battery pack...

[Patrick(MI)]

Working on an external battery pack for my ForsCoRe. Decided I need more run time on the unit and am using 4 of the 18650 Lithium-ion 3.7v 5800 mAh batteries. I installed a voltage regulator to reduce the 16.64v to 6.01. It will give me 23,200 mAh. I know, I know some of you are thinking that's over kill. LOL Yeh it is but that's how I roll. LOL Was looking for a box to put it all in and found an old external modem in my junk and decided it would fit the bill. I seem to always have more time than money so I'm mostly just using stuff around the house that I can find. I orded the voltage regulator on ebay for $4 w/free shipping. I still need to order some more two wire digital meters though. I want to install a momentary switch under the existing button and put the meter right behind the colored glass. I have an idea for mounting the whole thing without damaging the detector and when I get that going I will take more pics and post them.
Just one crazy old man with too much time on his hands. LOL

 

[Patrick(MI)]

Well I got the mounting setup attached. I found some heavy plastic that I formed with my heat gun. It hooks in the lip on the bottom and is held in place by the two thumb nuts for the arm cuff. The power feed wire just goes in a corner of the battery door and clips onto the + & - battery contacts. Man I love doing mods. LOL Once upon a time I used to do model mockups and prototype work when I worked in the tool shop but this is way more fun. Can't wait to see how long I can go before I need a charge.
I still need to order a digital meter and momentary switch for it and will add those pics as the project develops. Cedarswamp suggested that I put in a timer so that I can get a more accurate idea of how long between charges.
Anybody know of a small one and where I can find it?

 

[cedarswamp]

Run all summer on one charge ? SAVE$$,,,,,CEDAR

 

[BeyWolf]

Hi Patrick

Good project.
Could you share the information about the voltage regulator that you're using?
Name and Model number? Where it can be ordered?
I'm not sure if connecting 4 batteries in series will give you 4 times the mAh that you're hoping to get.
Maybe one of the electronic guru member's could inform us.

Thank you,
BeyWolf

 

[Patrick(MI)]

Mini DC-DC Buck Converter Step Down Module Power Supply For Aeromodelling (got it on ebay)

Product Features：
Size: 20*20*5mm
Input voltage: 4.75V-24V
Output voltage: 0.92V-15V
Output Current: 2A (maximum)
Voltage Regulation: ± 2.5%
Load Regulation: ± 0.5%
Load Regulation: ± 0.5%
Output ripple: 30mV (max)
Switching frequency: 1.2MHz
Operating Temperature: -40℃ to +85 ℃
Conversion efficiency: 95% (the highest)
Module Properties: non-isolated step-down (BUCK)
Rectification: non-synchronous rectification

 

[Patrick(MI)]

Oh man that'l be a disappointment. LOL Oh well that's what I get for tinkering around. Yeh 23,000+ mAh did seem like a lot. LOL
Still lots of fun making this stuff.

 

[cosmic]

Set up that way you increase the voltage only.. The capacity is still the same 5800 mah.. If you go two in series to increase the voltage to 7.4 and then parallel the other you will increase the capacity to 11600 mah..

 

[Patrick(MI)]

Oh Oh Oh!!! You have to send me a simple sketch to know how to do that. Please.

 

[Patrick(MI)]

Do you mean like this?

 

[cosmic]

Yes I think you have it..

 

[BeyWolf]

Thanks for the information on the voltage regulator module.
I did some research. Even though the module has a regulated output,
it seems to be more of a high efficiency power converter.

I think you can leave the 4 batteries connected in series
giving you 14.8 volts input to the regulator. With the input voltage twice as high
as the output voltage, I think the input current draw from the batteries
will be half as much as the output current going to your detector.

In other words it will seem like you have a 10,000 mAh or higher battery pack.

I hope somebody will check this and let me know if I'm wrong.

 

[cosmic]

Cell Connection Basics

There are two ways that the cells can be connected together. “In Series” is where the positive terminal of one cell is wired to the negative terminal of another cell. With this method, the total voltage of the pack is the sum of the individual cell voltages. For example, a 6-cell NiCd or NiMH pack is made up of cells rated at a nominal 1.2 volts each. When wired in series the total nominal voltage of the pack is the number of cells in the pack (6) multiplied by the voltage of each cell (1.2V in this case) to get the total pack nominal voltage (7.2 volts for this example). This is the most common cell connection method found in the RC hobby.

The second is called “Parallel” where you connect the positive terminal of one cell to the positive terminal of another, and negative terminal of one cell to the negative of another. Wiring cells in Parallel increases the total capacity of the pack but the nominal voltage remains that of a single cell. To figure out the actual end result capacity add the mAh rating (milli-amp hour) of the cells. If you put 2 cells in parallel that are each 2100mAh (commonly referred to as “2P”), multiply 2100 by 2 for a total capacity of 4200mAh.

 

[Patrick(MI)]

Thank you for all the great input. So just to make sure we're on the same page. Is this then the way it should be connceted?

 

[BeyWolf]

Do NOT connect the batteries the way you show in your last diagram.
You can leave them the way they are or you can try this.

 

[cosmic]

BeyWolf has it !!

 

[Patrick(MI)]

Okay cool that is how I changed it. I got confused with the pics cosmic posted so I thought I better ask the pro's.
Thank you for all the great info you guys I truly do appreciate it.

 

[Patrick(MI)]

I forgot to add. I get confused easy. Ask cedarswamp. LOL

 

[Patrick(MI)]

Okay I have rewired the two battery sleds inside as directed. Momentary switches and digital displays arrived today so I installed both. Here's the final two pics.

 

[BeyWolf]

That's a nice looking well done project.
Is that the no-load battery voltage being displayed?

Some batteries continuously drop in voltage while they are used and
some batteries maintain their rated voltage until the end of their discharge period.
I don't know how your batteries will behave.

If they stay above 7 volts until the end of their discharge period,
your new battery pack will do what you wanted.

If the voltage on your batteries drops continuously and gets down to 7V or lower,
the regulator might not work correctly and then your detector might not work correctly.
You might have to connect all four batteries back to their original end to end
series connection to get the maximum battery life.

Keep an eye on the voltage when you start using it and you'll figure it out.
Good luck.

 

[Patrick(MI)]

By no load I'm guessing you mean the voltage before it goes through the regulator. Then yes. I wanted to keep track of the batteries so they didn't go too low. Cedarswamp told me not to let them go down by too much of a percentage. Not sure what that percentage is. LOL
But thank you for the compliment. Being just a tinkerer I love to do little electronic projects. When I was growing up my neighbor next door was an electronics wiz. My mom always had me take the kitchen radio over to him whenever it was giving her trouble. I always thought that with his ability he would be an electrical engineer. Turns out he does food catering. Who'd a thought. LOL
I am noticing that the batteries are losing voltage just sitting inside the pack. So I think I will change it back to the way I first had it.
Now my other external battery pack for my Explorer isn't losing any voltage. I check it every day and it's still at 12.0 volts since my last use. Which by the way when I did use it for about 2.5 hours the voltage dropped from 12.1 to 12.0. That's with 3 batteries end to end.
I'm working on converting my White's 49er batter packs over to these new Li's. I will post pics when I finish.
I just love re-engineering things. LOL