Powering multiple small battery devices from one battery

Thread Starter

Alex Champ

Joined Feb 28, 2019
3
Hi guys, any help would be welcomed on this matter.

I have multiple battery powered small electrical components (onboard guitar preamps and pickups) and would love to combine them to one power source, making my life easier having to recharge just on bigger battery.

All devices are made to run on standard AA 1.5 or 9V batteries.

Here are the batteries I'm trying to substitute

3x 9V
1x 1.5V

1) How would I be able to give a different Voltage to my 1.5V device?
2) What kind of battery can I use get the same life spend as all my batteries combined?

Thanks for any input!
 

crutschow

Joined Mar 14, 2008
27,734
1) How would I be able to give a different Voltage to my 1.5V device?
If you want to run everything off the 9V battery, you could use a voltage regulator (e.g. LM317) to drop the 9V to 1.5V, but if the 1.5V devices draw much current, that would be inefficient.
2) What kind of battery can I use get the same life spend as all my batteries combined?
As is often said, it depends.
Depends upon how much current all the devices draw, and how long you want to go before recharging the battery.
How long do the devices run with the AA and 9V batteries?
 

ElectricSpidey

Joined Dec 2, 2017
1,806
One 12 volt SLA battery

One 12 volt SLA battery charger

2 DC to DC adjustable or fixed buck modules

Various hardware…switches, wire…etc.
 
Last edited:

Yaakov

Joined Jan 27, 2019
3,507
Hi guys, any help would be welcomed on this matter.

I have multiple battery powered small electrical components (onboard guitar preamps and pickups) and would love to combine them to one power source, making my life easier having to recharge just on bigger battery.

All devices are made to run on standard AA 1.5 or 9V batteries.

Here are the batteries I'm trying to substitute

3x 9V
1x 1.5V

1) How would I be able to give a different Voltage to my 1.5V device?
2) What kind of battery can I use get the same life spend as all my batteries combined?

Thanks for any input!
My first impulse would be to work with 18650 Lithium cells. They are readily available, can be expensive, are easy changed if they have problems, and have high capacity. You’d need at least three, in series since they produce about 3.6V (3.6*3=10.8V). The first problem with that is voltage regulators needing at least ~2V more than the voltage they pass. This can be overcome by using an LDO (Low Dropout regulator) which can have its input and output closer. So, for the 9V outputs you’d need that. For the 1.5V outputs, you’d want to use a buck converter which more efficiently reduces the voltage.

All of the charging management stuff can be purchased off the shelf, and protected cells make it easy.

To start to design it, you need to know how much current each thing requires, so you can choose LDO(s) and buck converters that will handle the current. I doubt they need much. This should allow a modest 18650 pack to run for a long time powering everything.

The parts are cheap, you just need to be systematic about designing it, it should work well.

EDIT: I said “expensive” which is the opposite of what I intended, read it as “inexpensive”.
 
Last edited:

djsfantasi

Joined Apr 11, 2010
7,830
You did say 3 x 9V batteries. Is that for three separate devices?

A 9V battery is rated for 550mAH. So to use a single battery, you need one rated at 1650mAH. More to also replace the AA battery.

Do you know how much current each devices draw? Or can you measure the current draw? You’ll need a DMM to measure the current on its mA setting. You’ll also need to interrupt the power line, because the meter must be in series to measure current.

I’ve used a pair of 9V battery clips to measure current draw from a 9V battery. Connect one red on one clip to the black on the other clip. Then, attach the meter between the remaining two wires. Use this device between the battery and device to measure the current.

Another device can be used to measure the current draw from the AA cell. Use a scrap of double sided PCB board that fits between the sides of the battery holder. Solder two wires to either side of the PCB. Then, slide this device between the battery and the battery holder contacts.

Once you know the current draws, add them up for the total draw. This may help you more accurately calculate battery life.
 

Thread Starter

Alex Champ

Joined Feb 28, 2019
3
If you want to run everything off the 9V battery, you could use a voltage regulator (e.g. LM317) to drop the 9V to 1.5V, but if the 1.5V devices draw much current, that would be inefficient.
As is often said, it depends.
Depends upon how much current all the devices draw, and how long you want to go before recharging the battery.
How long do the devices run with the AA and 9V batteries?
Thanks for the reply. It's very hard to measure as all electronics are inside the guitar. I know the two 9V Pickups last at least 30 to 50 hours on full charge and I've been using 8.4V 200mAh rechargeable batteries.

I've found the specs for the other condenser mic (the 1.4V) looks like it runs at 0.4mA for around 1200 hours

Scan.jpeg
 

Yaakov

Joined Jan 27, 2019
3,507
Thanks for the reply. It's very hard to measure as all electronics are inside the guitar. I know the two 9V Pickups last at least 30 to 50 hours on full charge and I've been using 8.4V 200mAh rechargeable batteries.

I've found the specs for the other condenser mic (the 1.4V) looks like it runs at 0.4mA for around 1200 hours
Obviously, in the case of this mic, you’d want to use phantom power which means you’d have to build in the connectors to allow the mic to pass through your power box.
 

Thread Starter

Alex Champ

Joined Feb 28, 2019
3
Obviously, in the case of this mic, you’d want to use phantom power which means you’d have to build in the connectors to allow the mic to pass through your power box.
I'm combing all those outputs into one signal and sending that through to the rest of my rig using a wireless system, phantom power is not an option unfortunately. :(
 

Yaakov

Joined Jan 27, 2019
3,507
I'm combing all those outputs into one signal and sending that through to the rest of my rig using a wireless system, phantom power is not an option unfortunately. :(
It is, if you pass the mic signal through your power box. You'd just inject the power and pass it on to the wireless.
 
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