First draft of external ML battery power -

Max Iso wrote:

techjedi wrote:

Max Iso wrote:

Thx for the suggestion jedi. Incidentally i also have an old Panasonic camcorder battery, but only 2800mAh at 7.2v so not really worth using but the thought did cross my mind as i have seen people using those sleds in other discussions.

But my techy skills don't quite reach that far yet so i hadn't looked much further. Electrical stuff always confused me for some reason and only recently have i decided to learn more about it, voltage/amps/polarity and such. I will definitely keep it in mind as i may not end up with just one solution.

You can do it. Its actually pretty easy. While undervolting wont damage a device, negative voltage will, but its really easy to just get a volt meter and you can test the polarity before trying.

If just soldering a single battery, its as simple as matching up the red/black to pos/neg as with the old battery. Use the voltmeter in DC volts mode to check the old reference dummy battery terminals. Then connect new battery and check again. If you see negative voltage, you have the polarity wrong, if its positive, you are good to go.

Regarding multiple batteries, its like this:

• wired in series doubles voltage at the same amount of available current.
• wired in parallel keeps the voltage the same, but doubles the available current (or current hours (aH)) for this application.
• Parallel is the easiest to wire, you just connect all the reds together and all the blacks together and its done.
• Series wiring goes from battery to battery across the terminals and then back to source. (search for a diagram as a better example).

At the end of the day, again, you can prototype your configuration, then use a volt meter to check it with little worry of damaging anything. As long as the voltage registers correctly on the volt meter, the device will only draw the current it wants up to the battery limit, the battery wont deliver too much current.

Batteries do have a voltage curve where, at full charge, they are about 10-15% over the stated voltage when tested without load. Once under load, the voltage drops to about 5-10% over stated voltage and slowly drains to 5-10% below the stated voltage before failing to power the device with current.

For example a device that says it needs 1.5V will work when the battery is at up to around 1.8 V fully charged and then down to around 1.2 V. Some low-current devices might even still be able to use the battery down to 1.1 V.

This is also what i've read many times about voltage change with charge. The claim is that for NiMH (all of my AAs) they are consistent in voltage, but others like alkaline and L-ion they indeed change over the charge life.

Also, i could be wrong but i thought i read the series was one after another, meaning they each drain the capacity one after another and keep voltage the same, where parallel multiplies the voltage but keeps capacity the same since they all drain simultaneously. I think you had it backwards, if not im happy to be corrected.

You have it half right. Series is one after another, but that is what doubles the voltage and keeps the same current, but honestly some of the wiring diagrams don't make the distinction obvious, so I think its a common confusion. Parallel is what keeps the voltage the same, Series is what multiples the voltage.

For example, some of these devices (e.g led panels) that operate with these 7-9V Sony NPF batteries also accept 6 AA batteries where is 1.5V * 6 = 9V and they have a internal voltage regulator stepping that down if needed. If you look in the battery compartment, the batteries are usually butted up against each other in a series. In parallel would mean there was just a bar connecting across all the top terminals and another bar flat across the bottom terminals, etc, but then it would only be 1.5V for the device, etc.

Here is a simple explanation with diagrams:

https://www.batterysystems.net/series-vs-parallel/