Clock battery using "in stock stuff"

[tq60]

We have an electric clock from 1901 to 1905.

It is a self winding type, runs on a pair of 1.5 volt ignition batteries, is hard to find, and is expensive.

Given that we are cheap, we had to be made with what we had handy.

We had a brand new battery for a communications radio that the charging circuit failed, got a warranty replacement, and did not need to send it in, so we opened it up.

Inside were 2 flat-pac Lithium batteries, 3.7 volts @ 3400 mA, modified the combiner board to make them parallel instead of series, so 3.7 volts @ almost 7 amp hr

The clock has a switch that grounds the internal solenoid that winds the clock. This switch is on a shaft, so we want to reduce the chance of sparks.

Plus, the original was 3 volts or a little less, 3.7 with high current needs control.

Using a modified trick we learned years ago, we made a current control system that removes the spark on the make contact and controls the current.

From the battery, we added a 10 K resistor.

From the clock side, we connected a 50 K pot.

We had some PNP TO3 cased Germanium transistors, the emitter to battery, collector to clock, and pot wiper to base.

The switch closes connecting the 10 k resistor buffered battery to coil.

Voltage drop across the 10 k turns on the transistor.

The pot varies the drive, so current is controlled.

The transistor bypasses the 10 k resistor supplying controlled current to clock.

The current is normal 0.5 amps, set to 0.45 amps to reduce stresses.

Estimate it should last 6 to 7 years on a charge.

The pot was locking type, bonus.

The loop is to measure current.

Added a charge port, found a wall wart style Lithium charger to charge the batteries.


The small wood box required some layout to make it all fit, took a few tries on paper, the fuse holder is just a bit too long, cut the recess just a bit too deep, a washer fixed that.

The parts are designed for panel mount, wood was 0.3 thick, nothing would work, so counter-bored everything to fit flush.

All but fuse holder.

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[Dhal22]

Way over my head, I’ll just stick to plumbing.

 

[tq60]

Forgot the schematic, but it does not have the charger, this is just the active part.

Real simple circuit.

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[woodchucker]

We have an electric clock from 1901 to 1905.

It is a self winding type, runs on a pair of 1.5 volt ignition batteries, is hard to find, and is expensive.

Given that we are cheap, we had to be made with what we had handy.

We had a brand new battery for a communications radio that the charging circuit failed, got a warranty replacement, and did not need to send it in, so we opened it up.

Inside were 2 flat-pac Lithium batteries, 3.7 volts @ 3400 mA, modified the combiner board to make them parallel instead of series, so 3.7 volts @ almost 7 amp hr

The clock has a switch that grounds the internal solenoid that winds the clock. This switch is on a shaft, so we want to reduce the chance of sparks.

Plus, the original was 3 volts or a little less, 3.7 with high current needs control.

Using a modified trick we learned years ago, we made a current control system that removes the spark on the make contact and controls the current.

From the battery, we added a 10 K resistor.

From the clock side, we connected a 50 K pot.

We had some PNP TO3 cased Germanium transistors, the emitter to battery, collector to clock, and pot wiper to base.

The switch closes connecting the 10 k resistor buffered battery to coil.

Voltage drop across the 10 k turns on the transistor.

The pot varies the drive, so current is controlled.

The transistor bypasses the 10 k resistor supplying controlled current to clock.

The current is normal 0.5 amps, set to 0.45 amps to reduce stresses.

Estimate it should last 6 to 7 years on a charge.

The pot was locking type, bonus.

The loop is to measure current.

Added a charge port, a 1 k resistor limits charge to 10 mA with a 12 volt adaptor, and should be safe for a Lithium battery.

Should take a couple weeks to charge from dead, can charge while running.

The small wood box required some layout to make it all fit, took a few tries on paper, the fuse holder is just a bit too long, cut the recess just a bit too deep, a washer fixed that.

The parts are designed for panel mount, wood was 0.3 thick, nothing would work so counter-bored everything to fit flush.

All but fuse holder.

Sent from my SM-G781V using Tapatalk

Oh, LIPO batteries.. woah.. charging those is not for a simple charger.. AND never let the cells go below 3.2.. you need to balance those cells while charging as well. Those have tremendous power in them and can do some real damage if not properly handled..
Be sure, be safe.

 

[Dhal22]

Although I use Li ion batteries most of us rc airplane guys are Lipo users and are maniacs with charging and monitoring.

 

[markba633csi]

Probably just a single diode in the + lead would have cancelled out the excess 0.7 volt, but hey you needed a project right?

 

[homebrewed]

We have an electric clock from 1901 to 1905.

It is a self winding type, runs on a pair of 1.5 volt ignition batteries, is hard to find, and is expensive.

Given that we are cheap, we had to be made with what we had handy.

We had a brand new battery for a communications radio that the charging circuit failed, got a warranty replacement, and did not need to send it in, so we opened it up.

Inside were 2 flat-pac Lithium batteries, 3.7 volts @ 3400 mA, modified the combiner board to make them parallel instead of series, so 3.7 volts @ almost 7 amp hr

The clock has a switch that grounds the internal solenoid that winds the clock. This switch is on a shaft, so we want to reduce the chance of sparks.

Plus, the original was 3 volts or a little less, 3.7 with high current needs control.

Using a modified trick we learned years ago, we made a current control system that removes the spark on the make contact and controls the current.

From the battery, we added a 10 K resistor.

From the clock side, we connected a 50 K pot.

We had some PNP TO3 cased Germanium transistors, the emitter to battery, collector to clock, and pot wiper to base.

The switch closes connecting the 10 k resistor buffered battery to coil.

Voltage drop across the 10 k turns on the transistor.

The pot varies the drive, so current is controlled.

The transistor bypasses the 10 k resistor supplying controlled current to clock.

The current is normal 0.5 amps, set to 0.45 amps to reduce stresses.

Estimate it should last 6 to 7 years on a charge.

The pot was locking type, bonus.

The loop is to measure current.

Added a charge port, a 1 k resistor limits charge to 10 mA with a 12 volt adaptor, and should be safe for a Lithium battery.

Should take a couple weeks to charge from dead, can charge while running.

The small wood box required some layout to make it all fit, took a few tries on paper, the fuse holder is just a bit too long, cut the recess just a bit too deep, a washer fixed that.

The parts are designed for panel mount, wood was 0.3 thick, nothing would work so counter-bored everything to fit flush.

All but fuse holder.

Sent from my SM-G781V using Tapatalk

All the electronic nerds here are jumping out of the woodwork (I count myself among them . I think your circuit is overkill. If the clock rewind system uses a motor originally driven by a 3V battery, bumping the source voltage up to 3.7V isn't going to be much of a problem. The clock was built in the early 20th century, no super-sensitive electronics were in sight. If the rewind motor spins a tiny bit faster, is that really going to be a problem?

Also, the original battery for the clock had no current limit, other than the battery's internal resistance. So the current limit feature probably is overkill as well. If there is concern about 3.0 vs. 3.7V, the suggestion made by @markba633csi should do the trick.

 

[tq60]

Of course, it is overkill!

A diode would have worked fine, but what is the fun in that?

If something shorts out, it does not matter. Only 500 mA of current.

The active circuit only has 3 parts, not much complexity.

Clock uses a pair of coils in series to act as a solenoid to pull a lever that launches the weights up.

Had it running on a 5 volt wall wart for testing, did not care for the usual pair of D cell fixes that are common with these.

Why? Because we could...

It was something to do just for fun, as an experiment, and it works better than we thought for a stupid simple circuit.


We limit the charging current to 10 mA, should be safe at that level, no hurry.


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[silence dogood]

Throw in a 2.4-volt zener diode . Now you got overkill.

 

[tq60]

Using a zener diode of that voltage to limit the voltage would be the crowbar effect. the battery would die fast.

We did that once back in the CB days.

Held the voltage fine, but the power supply did not like it.

One could use it in bias to the transistor to set the voltage, but now it gets complicated and has idle current.

Our circuit draws no current when idle, reduces the contact current to less than 1 mA, then provides the correct current AFTER the switch has made contact.

It also limits the current to a similar amount to protect from shorting wires or coils.

And only 3 active parts.

We added accessory items such as a set of banana plugs in series with the battery to allow easy current measurement.

We could have just got some battery holders and used D batteries like most, but they did not have them.

One coukd claim over-kill, considering only 3 parts and the function it seems otherwise.

Using a PLU to same would be that.

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