# Does this Work? 2x female to 1x male to run 2 power sources in parallel?

#### An Aberrant Person

##### n00b
I have 2 backup batteries that can run at various voltages. Assume these 2 scenarios for 12v and 19/20v.

Can I use this cable below to run 2 power sources of equal volts in parallel to double the maximum amp limit and run time? For the 12v option which is the max amps?

Split power cable
https://smile.amazon.com/dp/B07F5VW...olid=2EKNW43BVT70W&psc=1&ref_=lv_ov_lig_dp_it

battery pack 1
https://www.ebay.com/itm/373708300350?nma=true&si=ZR4H9va8v%2Bi%2BEoA0Nc9KopIIwQA%3D&orig_cvip=true&nordt=true&rt=nc&_trksid=p2047675.l2557

battery pack 2
https://smile.amazon.com/dp/B07RNZZ...olid=1Z82TV3H4UG33&psc=1&ref_=lv_ov_lig_dp_it

freezer
https://smile.amazon.com/gp/product/B07MGXQY3V/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Laptop
https://www.newegg.com/black-obsidi...1-887w/p/N82E16834316267?Item=N82E16834316267

I attached a diagram for simplicity.

I appreciate any and all help. Thanks!

#### Attachments

• laptop battery diagram freezer question.png
505.8 KB · Views: 0
• laptop battery diagram laptop question.png
447 KB · Views: 0

#### GotNoRice

##### [H]F Junkie
That splitter would run the two batteries in parallel, so voltage stays the same, amps are doubled. That would work fine if we were talking about bare batteries, but I have no idea how the circuitry in each pack is going to react to being put in parallel with another battery. If you connect something like a phone using USB, it will negotiate with the phone to determine what voltage to use depending on what the phone supports. USB ports will always default to 5V unless your phone supports a compatible quick charging standard, etc. Do the packs have a way to set them manually to always output 12V? Finally, running mismatched packs in parallel can cause some issues. If one pack discharges more quickly, the pack that still has power will basically try to charge / transfer power to the pack that died first. No idea how that would play out using the packs that you have.

#### An Aberrant Person

##### n00b
That splitter would run the two batteries in parallel, so voltage stays the same, amps are doubled. That would work fine if we were talking about bare batteries, but I have no idea how the circuitry in each pack is going to react to being put in parallel with another battery. If you connect something like a phone using USB, it will negotiate with the phone to determine what voltage to use depending on what the phone supports. USB ports will always default to 5V unless your phone supports a compatible quick charging standard, etc. Do the packs have a way to set them manually to always output 12V? Finally, running mismatched packs in parallel can cause some issues. If one pack discharges more quickly, the pack that still has power will basically try to charge / transfer power to the pack that died first. No idea how that would play out using the packs that you have.
a few things.
Do the packs have a way to set them manually to always output 12V?

1) Yes, those laptop battery packs you can set on the pack which voltage you want the packs' voltage range is 5v, 8.4v, 9v, 12v, 16v, 20v (you change voltage by double-tapping power button after it is on). The jumper/battery pack is only 12v 10amp DC.

If one pack discharges more quickly, the pack that still has power will basically try to charge / transfer power to the pack that died first. No idea how that would play out using the packs that you have.

This is patently wrong and would never happen (highlighted yellow) The pack has dedicated outputs and inputs. You are thinking that these packs are mere batteries but that's not true. These have circuitry and that circuitry would never allow that to happen. Now the thing with using 2 different packs. When the first pack runs out of battery it automatically turns off so you would just be running off 1 remaining battery pack which is perfectly fine as long as that pack has sufficient amps to run the device. If it lacked the amp output it would either just keep feeding it the max amps it could or the pack would auto-shutoff to prevent overload.

I appreciate the response.

#### GiGaBiTe

##### 2[H]4U
This is patently wrong and would never happen (highlighted yellow) The pack has dedicated outputs and inputs. You are thinking that these packs are mere batteries but that's not true. These have circuitry and that circuitry would never allow that to happen.

Unless you have the packs in question, and have tested them for backfeed, never say it won't happen. I've seen all sorts of battery banks that claim to have dedicated in and out power feeds, but they were all wired up in such a way you could backfeed power into them from any port, regardless of what the label on the unit says.

Now the thing with using 2 different packs. When the first pack runs out of battery it automatically turns off so you would just be running off 1 remaining battery pack which is perfectly fine as long as that pack has sufficient amps to run the device. If it lacked the amp output it would either just keep feeding it the max amps it could or the pack would auto-shutoff to prevent overload.

No. What's going to happen if you connect the two packs in parallel is that each pack is going to start fighting each other. Power banks are not designed to run in parallel with other power banks, when you connect the outputs together, the load regulation circuitry is going to start going wonky because it detects voltage and load fluctuations on the line. The 2.1mm barrel splitter you linked is not designed to take two power sources and feed it into one, it is designed to power two CCTV cameras from one power source.

If you did cobble together such a setup, what would happen is that the power bank with the higher voltage will drain faster than the power bank with the lower voltage. There is always going to be minute differences in the voltage output between power banks, and that is enough to cause a problem. It's why power supplies that use mosfets in parallel have such complex circuitry, they have to account for variations between them and correct for it so that one mosfet doesn't take the entire load and blow up from an overload. Linear regulators are much the same, but even harder to balance.

Your proposed setup is bad and potentially a fire hazard. I'd recommend abandoning the idea and do something proper, like use a solar panel with a dedicated charge controller+inverter on a battery. A 120-200W solar panel and a good battery bank isn't that much more expensive than your proposed janky setup.

#### An Aberrant Person

##### n00b
Unless you have the packs in question, and have tested them for backfeed, never say it won't happen. I've seen all sorts of battery banks that claim to have dedicated in and out power feeds, but they were all wired up in such a way you could backfeed power into them from any port, regardless of what the label on the unit says.
I'll take your word for it and get back to you if/when I try. I personally have never had that experience with the ones I have. I have tried in the past charging charger with charger and never seen any back feeding.

No. What's going to happen if you connect the two packs in parallel is that each pack is going to start fighting each other. Power banks are not designed to run in parallel with other power banks, when you connect the outputs together, the load regulation circuitry is going to start going wonky because it detects voltage and load fluctuations on the line. The 2.1mm barrel splitter you linked is not designed to take two power sources and feed it into one, it is designed to power two CCTV cameras from one power source.

If you did cobble together such a setup, what would happen is that the power bank with the higher voltage will drain faster than the power bank with the lower voltage. There is always going to be minute differences in the voltage output between power banks, and that is enough to cause a problem. It's why power supplies that use mosfets in parallel have such complex circuitry, they have to account for variations between them and correct for it so that one mosfet doesn't take the entire load and blow up from an overload. Linear regulators are much the same, but even harder to balance.
well, I'll just have to try it and find out. I'll use some disposable things first to see what happens.

Your proposed setup is bad and potentially a fire hazard. I'd recommend abandoning the idea and do something proper, like use a solar panel with a dedicated charge controller+inverter on a battery. A 120-200W solar panel and a good battery bank isn't that much more expensive than your proposed janky setup.
that won't work for me. My planned use for this is space and weight limited so that won't work and larger packs are cost prohibitive, which is why I am looking into a jerry-rigged setups.