Homemade solar power bank. System Voltage

DIY Passthrough Charging Power Bank from Old Laptop Batteries 18650

In This Video We Will Make a Better Power bank With Recycled Old Laptop Battery. If Want a Perfect Power Bank. Which Have Two USB Ports for Input and Output So you Can Double your charging speed (Current) of your power bank.

With This Dual USB input its possible to charge power bank from two USB chargers at 1.6 amperes, in half an hour from 0% to 100%

Pass through charging let you charge your device connected to power bank while charging the power bank itself. its one of the best diy cell phone charger that you can make.

The lithium cells can be reused from old laptop battery.

Specifications Input : 5v. 1.6 A Output : 5v. 2 A

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Homemade solar power bank

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In this blog article, you will learn how to create homemade EMF protection for your solar power bank or for other devices. Between this blog article and an accompanying YouTube vlog, you should be able to find enough information to get started.

Measurements are always the first step!

Measure your product and always add 1 to 2 inches for extra space. Then, add another 1 inch so you can have a 1/2 inch seam allowance on each side.

For the sake of simplicity in pattern making, the Bluetti solar power bank pattern ended up being a 30×30 bag cut on the fold. To create the base, I simply cut out a 6×6 square on each side of the folded fabric. The removed fabric left me with 18 inches of width for the 17 inch Bluetti base.

Please, do apply the same measurement method to your solar power bank or any other kind of faraday bag make because it will reduce confusion and headaches. Most importantly, consider how the bag will open and close. For myself, I decided to use a zipper for the bag opening. The zipper required me to use extra fabric to create a lapped zipper for extra EMF protection.

How to sew up the homemade EMF protection

To create this homemade EMF protection, start by laying the EMF fabric down. Then, lay the canvas fabric on top with the right side facing upwards toward you. Now, place the YKK zipper down with the right side facing the right side of your canvas fabric. Pin in place. Sew and top sew.

Now, fold up the Nylon webbing 1 inch on each side. Place the folded webbing onto the bottom of your bag and pin it into place. Now, sew the webbing down and secure it with a barn door stitch on the bottom and top. Note: I usually place the barn doors 2 inches below the top of the bag and two inches above the bottom.

homemade, solar, power, bank

Once your nylon webbing is attached, pin the other side of your zipper to the opposite side of the fabric. Sew the zipper down.

You should see the bag taking shape now! Now, sew the corners of your bag closed.

You are now in the home stretch of making this bag. To finish, place the lining and canvas fabric together with right sides facing. Sew up both sides, leaving a big enough hole in the lining to turn this bag to the inside.

Last, you’ll want to turn the bag right side out and sew the hole in the lining closed.


Step 1. Calculate Your Energy Needs

If you need the generator to power your devices and the occasional appliance [2] on your boat or RV, or during a power outage in your home, check out this list of typical power ratings for some of the most common devices:

Step 2. Test the Equipment

First, you need to test the panel and the charge controller.

  • Plug the two pigtails cords coming from the panel in the appropriate and (-) sockets on the charge controller.
  • Now, hook the controller to the battery.
  • When you hook the negative cable, a green light on the controller should light up — showing that the battery is charged.
  • Flip your panel towards the window to make sure it’s picking up sunlight, and another green light on the charge controller should come on — showing that the panel is charging the battery.

Next, you need to test the inverter.

  • Hook up the red and black cable the inverter came with on the inverter terminal, and hook the other end of the cables on the battery.
  • Make sure you connect the positive cable first.
  • To test the inverter, switch it on and plug in a home appliance with a decent load, for example, a fan.

Another component you need to test is the battery maintainer.

  • Disconnect the battery from the controller and hook the maintainer cables to the appropriate poles of the battery.
  • Again, make sure to connect the positive side first.

At the same time, you can test your surface mount contactor.

  • Plug the extension cord from the wall socket.
  • If everything is right, both green and red light on the maintainer should come on.
  • After a few seconds, only the red should remain — showing that it needs charging.

If you prefer to watch a video, here’s one that shows you how you can test each of your components:

homemade, solar, power, bank

Step 3. Build the Generator

This is where you mount all the equipment and do some of the early wirings of your system.

Mark and Cut the Openings

You can use masking tape to make the initial marks. This way you can adjust them without leaving permanent marks on your case.

Measure the actual size of each hole and trace the lines onto the case. If in doubt, always cut smaller and then file or trim the opening larger if needed.

For straight cuts, use a vibrating multi-tool with a plunge-cutting blade. For the round holes, you can switch between drill bits and hole saws.

To trim and adjust the holes, use a rotary cutting blade with a pneumatic die grinder.

You can check an article comparing Milwaukee and DeWALT power tools on Tool to Action if you need help with choosing the right power tools to use in this step.

If you prefer hand tools, you can achieve the same with a utility knife or a file.

Mount External Components

Once you’ve cut the holes, test the LED floodlight for fit then line the edges with black silicone sealant to keep the box interior waterproof. Once the silicone starts to cure carefully place the light in its slot.

The 120V AC charging port comes with a rubber gasket, so you don’t have to use silicone for that.

Repeat the process for the components on the other side of the hard case.

For the inverter remote control panel, you’ll need some silicone sealant. Secure the panel with self-tapping screws.

Use heavier #10-24 machine bolts to mount the weatherproof cover and GFCI outlet. Don’t bolt them yet, because you need to wire everything first.

If the solar power inverter has the peak capacity above 4000 watts, you need to use 12 gauge wire for the GFCI outlet. Always give yourself 4-5 inches of wire more than you need.

Now you need to mark and cut holes for the solar panel connection and the high-current 350A connector. The 350A quick connector is an optional feature, but it lets you use the battery with jumper cables or to daisy-chain more batteries and increase the generator power.

Finally, you need to mount the second LED floodlight on the lid of the solar generator. Follow the same procedure as used for the first one, but wait until you mount all the internal components first.

Mount the Battery

Since batteries are the heaviest components, put it in the corner closest to the case wheels. You can orient the battery in any direction, but make sure it’s well supported in the directions the case is likely to be used.

Drill two holes for the battery mount bolts as shown in the video below, but don’t fix it in place until all components are ready for mounting.

Mount the Solar Power Inverter

You need to position your AC pure sine wave inverter so that its outlets are near the GFCI weatherproof outlet and its 12V cables within the reach of the battery.

Things To Keep In Mind If You Use A Custom-Built Lithium Battery

If you have enough experience in DIY electronics, you can make a custom lithium battery to use with your system. There are several things to keep in mind:

Low-Temperature Cut-off or Heating System — Lithium batteries can’t be charged under 32°F (0°C) without suffering permanent damage. [3] If you use a lithium battery, find a solar charging controller with low-temperature cut-off.

MPPT Charge Controller Capable of Charge Profile Editing — Each battery needs a different max voltage. Program the MPPT charge profile parameters for the exact type of battery you plan to use.

A DIY solar generator is a self-contained and portable mini-power plant that can allow you to be 100% independent from the grid.

Over-Discharge Protection System — If you over-discharge a lithium battery, you’ll change its chemistry and damage it permanently.

homemade, solar, power, bank

High-Temperature Protection — If you plan to use the battery in a high-temperature environment, you’ll need a battery cooling system.

Cell Balancing — If you regularly charge and discharge from 100% to 0%, your cells will fall out of balance, so you need to use a manual RC battery cell balancer.

Potting batteries — Lithium batteries contract and expand during discharge and charge. So unless you compensate this with a foam pad, you shouldn’t pot them.

Why Build Your Own DIY Solar Generator

Greener Than Fuel Generators

With zero emissions, solar generators are far more environmentally acceptable than those running on fossil fuels. When you are enjoying the great outdoors, the last thing you need is a diesel generator polluting everything around you.

To see a review of a portable solar generator, click here.

Safer Than Gas Generators

Solar generators are much safer to use indoors and outdoors that those running on fossil fuels that may leak or cause a fire.

No Running Costs

Once you invest in components and tools, your spending is done. Their components typically have warranties that go over 20 years. [4]

There are a lot of benefits of electrical energy storage. It allows consumers to use power when they want to use it. It increases the amount of energy that we can use from wind and solar, which are good low-carbon sources.

Charles Barnhart, Postdoctoral Fellow at Stanford University Global Climate and Energy Project

You Can Repair Them Easily

Unlike fossil fuel generators that use complicated internal combustion engines, solar generators are easy to repair as they are to build.

Powerful Than Ready-Made Ones

Not all ready-made generators are powerful like the Kodiak Solar Generator. If you need more energy than an average RV owner, then building your own generators is the way to go.

DIY Gives You Pride Of Accomplishment

While building your solar generator, not only can you learn a lot about technology, but also gain a sense of personal accomplishment. You can include your spouse and kids and make it a family project.

Less Expensive Than Ready-Made Ones

If you purchase them individually, components recommended here will cost you much less than a complete ready-made generator system like this one.

See reviews of ready-made solar generators:

Connecting Batteries in Parallel vs in Series

Now that you know the voltage of your installation and the battery capacity you need, it’s almost time to start looking at batteries! In your battery system, there are two ways to connect multiple batteries together – in parallel or in series:

  • In Parallel: Connecting batteries in parallel simply means that each battery’s positive terminal is connected to the next battery’s positive terminal (and each negative terminal is connected to the next negative terminal). Batteries that are connected in parallel add up all their amp-hours together, allowing you to increase the total capacity of your battery bank.
  • In Series: Connecting batteries in series means connecting the positive terminal of the first battery to the negative terminal of the next, and so on. When connecting in series, amp-hours don’t increase, but voltage adds up amongst all the batteries. It’s also possible to create a system where batteries are connected both in parallel and in series to both increase voltage and amp-hours!

We need 768 amp-hours for our 12 volt solar installation. If we connect in parallel, we could have two 12-volt 400 amp-hour batteries, giving us 800 amp-hours but keeping our 12 volt system. If we connect in series, we could have 2 6-volt 800 amp-hour, giving us a 12 volt battery system with 800 amp-hour capacity. Whether to connect in series or in parallel is a matter of what batteries are available and the structure of your solar and storage installation.

All this can be confusing, but just remember: connecting in parallel adds amp-hours; connecting in series adds voltage! Knowing what options are available to you will help you build the most cost-effective installation that suits your needs.

Size Your Inverter

Inverters are an integral part of any solar and storage installation, as they convert the direct current (DC) electricity produced by your solar panels and housed in the batteries to alternating current (AC) required by all our electronic devices.

Inverters convert electricity from DC to AC in real time. Inverters have no storage capacity – as your devices use electricity, that electricity flows from the batteries through the inverter to the device. Because of this, your inverter needs to be large enough to handle the biggest load you’ll put on it at any single instance.

homemade, solar, power, bank

The easiest way to calculate this is to add up the wattage of all your devices that could be operating at the same time.

Let’s say we’re very busy in our cabin, so it’s possible that all our electrical devices could be going at the same time. As you can see from the table above, the total wattage for all my devices is 2,312 watts. So I need an inverter that can continuously handle at least 2,312 watts.

There’s one more critical step though to sizing your inverter. Some electric devices, especially motor-driven devices like refrigerators, power tools, and air conditioners, draw 2 to 8 times the amount of power they typically use just to turn on! This huge power draw is known as the surge load and you need to account for this when choosing an inverter.

Unlike a device’s typical wattage, which is printed on the back of a device, manufacturers don’t publish the surge load of their devices, so you either need to contact them directly or measure the electrical pull yourself for your motor-driven devices.

Fortunately for us, inverter manufacturers these days account for surge loads and most inverters can handle high spikes of electricity in short bursts. When choosing an inverter, be sure that they can handle the surge load for any of the electrical equipment you use.

We know that we need an inverter that can continuously handle at least 2,312 watts, but let’s say our clothes washer uses 3x the amount of power just to turn on, so our surge load is 3,512 watts. We could simply buy an inverter that can handle 4000 watts – but that’s expensive and unnecessary. It just so happens that there’s a 2500 watt inverter that can handle a surge load of 5000 watts – more than enough for our needs!


Deep cycle battery life and capacity are affected by temperature. Unlike PV modules, batteries perform best in moderate temperatures. In fact, the temperature standard for most battery ratings is 77° F. Cold temperatures tend to reduce battery capacity while high temperatures tend to shorten battery life. For this reason, people in colder climates will often find a place to keep their batteries indoors rather then leaving them subject to outside temperatures. FLA batteries can be destroyed in freezing temperatures. While sealed deep cycle batteries can operate in sub-freezing temperatures, their reserve capacities will be reduced substantially. Identify the lowest temperatures that the batteries will be exposed to and factor this into the calculation using the temperature table (below).

By this point, you will have identified your system voltage. This is typically 12V, 24V, or 48V.


Once you’ve pinpointed all these variables, it’s time to calculate the size of your battery bank! Let’s go through the steps below, using the following example system:

  • A system load of 6,000 Watt-hours per day
  • Three days of autonomy (backup) needed
  • Planned depth of discharge (DoD): 40%
  • Battery bank ambient average low temperature 60°F
  • A 48V system

Selecting Deep Cycle Batteries to Meet the Amp-Hour Capacity

Now that you know the Amp-hour (Ah) capacity that will give you the storage you need, you may need a little guidance in selecting specific deep cycle batteries. Keep in mind that it’s best to keep the number of parallel strings of batteries to three or fewer. If you parallel more than three strings of batteries, you risk shortening battery life due to uneven charging 1. The ideal deep cycle battery bank has no parallel connections but is comprised of one or more series-connected batteries. Though parallel connections are not to be avoided at all cost, fewer such connections tends to reduce the chance of charging problems over time.

When batteries are cabled together in series, the voltage is additive. For example, you can put two 12V, 100 Ah batteries in series for a 24V bank. The capacity of that bank would still be 100 Ah. When batteries are connected in parallel, the voltage remains constant and the Ah capacity is additive. In our example with the 12V, 100 Ah batteries, connecting them in parallel would result in a 12V system with a capacity of 200 Ah.

The deep cycle batteries you select must meet both your system voltage requirements AND the Ah capacity you calculated. In our example of the 48V system, we calculated that we needed 1,040 Ah to produce 6,000 Wh per day with 3 days of storage. than one configuration of batteries can meet this need. For example, you could have four 12V batteries in series, each with a capacity of 1,040 Ah or more. Or you could use eight 12V batteries wired in two parallel strings where each battery had a 520 Ah capacity. Or you could use twelve 2V batteries in series, again with appropriate Ah capacities. In any given case, there may be multiple solutions. Your choices will be limited by battery availability and budget.

Building the Battery Bank: Amps, Then Volts

To build your bank, try first to select a deep cycle battery that is rated close to the Ah capacity you calculated in Step 5 above. Ignore voltage for a moment. If you can’t find one that’s very close, look for one that has a capacity either one-half or one-third your needed Ah figure. These fractions represent the number of series strings of such batteries you would need, in parallel, to complete your bank (1/2 = 2 strings, 1/3 = 3 strings). Once you find a candidate battery, divide your system voltage by the battery’s voltage. This will give you the number of such batteries you would need in each series string.

The total number of individual batteries you will need to complete your battery bank will be the product of the number of strings needed to meet your Ah requirement and the number of batteries per string needed to meet your system voltage requirement.

Total # batteries in bank = (# series strings) X (# batteries per string)

You can then compare your candidate battery banks against price, size and availability. You may want to talk with people who have used these batteries and learn what their experiences have been, compare warranties and advertised features, and finally buy the batteries you feel are best for you.

In any battery-based RE system, deep cycle batteries are a major component investment — second in cost only to the PV modules in most cases — and they are a critical part of the system. Careful planning and deep cycle battery selection is vital to ensure that your battery bank meets your needs and provides many hundreds or thousands of charge cycles. Take your time, run the numbers more than once, and you’ll avoid the worst pitfalls of RE system design.

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