What The FX Pocket Chrono Should Have Been - Rechargable

[Privateer]

Since I'm waiting for the new tags to arrive for the Caddy, I figured out how to remove the wires from the JST Female parts.
I'll need to swap the wires to keep proper colors where they belong once I solder the power connector in place.
Then also when I start the serial port investigation.

 

[txcomp]

I’ve got another power supply update coming as soon as I get a chance to work on it. After our ice storm over the weekend, I’m forced to become a heater repairman since one of my heaters decided it was time to quit. I can answer almost any question you have about Nordyne gas heaters now (I think).

I have a surplus of 18v drill batteries so I’m going to make an adapter to use one of those batteries. This is not because I need that much battery but because I can with the buck in the circuit. My guess given the draw of the Chrony, I’ll only need to charge like once a year.

 

[UCChris]

After about a month of having the Pocket Chrony converted to LiPo...I hate it. It was a fun project and I learned some stuff, but I found that a LiPo battery was not the right choice, since storing a LiPo battery at full charge is terribly hard on the battery. The Pocket Chrony doesn't work at 3.8v, which is the storage voltage for LiPo, so I have to use a fully charged 1s battery to run the chronograph. Since I generally use the chronograph in short increments/sporadically, as I don't tune all my guns at once, this means I'm never draining the battery down storage voltage by using the chronograph. This leads to a "workflow" such as:

Need to use the chronograph -> plug LiPo into charger -> wait for 30-45 min for battery to charge -> use chronograph for 10-15 minutes -> plug battery back into charger to run a discharge cycle down to 3.8v

Other than just being an asinine amount of stuff to do just to use the chronograph for 10-15 minutes, this has raised two problems.

1) Every time I want to use the chronograph I am using a charge cycle on the battery pack, which LiPo's have a finite amount of.

2) I have inevitably gotten lazy, which means that I have one LiPo that I've designated the chronograph LiPo and it's just left fully charged and plugged into the chrony so I can use it at a moment's notice. While more user friendly, I hate that I'm ruining a LiPo pack, even if it's just a $6 1s pack.

So what now? Does anyone know if there's a battery chemistry that does well/okay at being left fully charged besides the AA's that the chrony originally used? The other option is to do as others have in this thread and build something to modulate the voltage down from a higher voltage pack. I'll have to see if there's any micro sized gadgets that will modulate a 2s pack down so I don't lose the portability of the system.

Anywho, end of my rambling for the moment.

Edit: Nevermind, more rambling. It appears there are small voltage step down boards that are used for drones. Now I gotta decide if I trust a little piece of hardware to not fail and let the higher voltage of a 2s pack through to fry my chronograph.

 

[nervoustrig]

A small fuse and a zener diode across the output would protect it if the regulator were to fail.

 

[SkeeterHawk]

It appears there are small voltage step down boards

That's the same thing @txcomp used in his design so he could use drill batteries or whatever. The FX Chronograph really needs a regulated voltage source since it is so finicky. Even the Alkaline aren't ideal, but at least they decay through the working range longer than the Li-Ion as you have found. You could also look for a "boost" regulator that will just step up the voltage to stay at 4.1V or whatever until the regulator drops out. You will probably get more run-time from a "buck" converter as you were referring to.

As @nervoustrig mentioned, that circuit will protect your Chronograph. You could also use a "Positive Temperature Coefficient" (or self-resetting) fuse.

Something to keep in mind too is that some switching regulators have a minimum current required to regulate, and some if this is not supplied, have the ability to run away. I'm saying this because you may not be able to just put a DVM on the output of the regulator and get the right voltage. It may be reading what your battery is putting out, and still be working correctly. You just need to draw a few mA for it to regulate properly.

Good luck, and thanks for sharing your findings.

 

[UCChris]

A small fuse and a zener diode across the output would protect it if the regulator were to fail.

That's the same thing @txcomp used in his design so he could use drill batteries or whatever. The FX Chronograph really needs a regulated voltage source since it is so finicky. Even the Alkaline aren't ideal, but at least they decay through the working range longer than the Li-Ion as you have found. You could also look for a "boost" regulator that will just step up the voltage to stay at 4.1V or whatever until the regulator drops out. You will probably get more run-time from a "buck" converter as you were referring to.

As @nervoustrig mentioned, that circuit will protect your Chronograph. You could also use a "Positive Temperature Coefficient" (or self-resetting) fuse.

Something to keep in mind too is that some switching regulators have a minimum current required to regulate, and some if this is not supplied, have the ability to run away. I'm saying this because you may not be able to just put a DVM on the output of the regulator and get the right voltage. It may be reading what your battery is putting out, and still be working correctly. You just need to draw a few mA for it to regulate properly.

Good luck, and thanks for sharing your findings.

Thank you both for your advice. I will do some research as I'm unavailable with some concepts here

 

[Bobbybeef]

i have had the same batteries in my fx chrno for 3 years

 

[SilentSquirrel]

i have had the same batteries in my fx chrno for 3 years

Dead or alive?

 

[SkeeterHawk]

Dead or alive?

That was my thought. I go through (like) three sets of batteries every time I do just about anything with my FX Chronograph...and that is only a few hour session.

Looking back at my previous post in this thread where I tested the current draw, the Chronograph pulls over 60mA in normal operation. An AAA battery has a total capacity of around 860mAH. We know these can't be drawn down to zero volts, but if it was possible, the batteries could only last under 13 hours. Reality is, you only get like 20% of the useable current, so that is only about 2 1/2 hours...and that is about right.

 

[Str8tshooter]

I recently picked up a FX Chrony, I did not read through all the posts, but has anyone tried rechargeables such as the Eneloops?

 

[SkeeterHawk]

I recently picked up a FX Chrony, I did not read through all the posts, but has anyone tried rechargeables such as the Eneloops?

From my testing, the Chronograph stops working below 3.75V. Those batteries only supply 1.2V a piece, so that is 3.6V total. They wouldn't even turn the FX Chronograph on.

 

[Bobbybeef]

Dead or alive?

alive

 

[whyzee]

While I cannot take credit for the design idea here, I can take credit for the execution.
Plenty of juice for the radar AND cellphone, simultaneously!!

 

[TDK]

I recently picked up a FX Chrony, I did not read through all the posts, but has anyone tried rechargeables such as the Eneloops?

4x Eneloops works perfectly.

If you open up the Chrony, you'll see a spot on the side if the circuit board which is an obvious location intended to mount an external power jack. This spot corresponds to a hole in the case. You could get fancy and try to find a jack that will mount there, or you could do what I did and take a USB cable that is sized appropriately for that hole in the case, cut one end off and solder directly to the circuit board. Now you have a USB pigtail that you can connect to either:

a 4xAA battery holder (ONLY use NiMH batteries since total voltage will be close to 5V!)
a USB power bank (USB output is 5V and the power bank handles the voltage regulation)

You can still used the internal battery slots, however, you need to make sure you don't connect both power sources at the same time. If you don't want to do any mods like above, I think the best option is to run 3x Energizer AAA Lithium disposable batteries in the internal slots. These have a higher voltage than alkalines and last longer. I had good luck with these before I did the external power mod, and they do keep you from having to swap out batteries as often.

 

[heavy-impact]

... or you could do what's in the original post for less than $20 and 1 hour of your time with a battery that will likely last the rest of your life so you never have to think about it again.
Do whatever makes you happy but I'd keep it simple.