Portable Solar Power Unit: Automatic Battery Charge! ;)
My starting point was to see if we can make portable solar power unit:
- different voltage outputs (including 220V AC)
- capable of storing energy
- capable to charge lead acid battery
Answer: Yes we can! 😉
If we well balance size and capacity of the unit, it will be much more useful.
When I search on web, found aluminum “suitcases” which can provide 220V AC output. They are usually very heavy due to lead acid batteries inside and not suitable to carry easily.
Another option was foldable panels fitted to fabric bases. Some of them has voltage regulators for DC output but only 2-3 different DC voltage levels…
Step 1: Main Parts Required
When I found “Seifert Magnus Midi 63” toolcase in local Bauhaus, very delighted:) Eureka!
it was perfectly matching size and specifications in my mind… Made of uv stable polypropylene and black in color. Dimensions 40.0×30.0x6.5cm and around 670 grams. Size well suited for two 10 Watts solar panels, has “ribs” on edges to protect switches and other equipments perfectly. Has handle and locks.
If I design a case for only this purpose, it would be very similar to this 🙂
Also we need 12V DC to 220V AC inverter. Found this 100 Watts unit on the web.
Sanyo 4S lithium ion batteries with over / under voltage protecting and over temperature protecting circuits.
Two 10W solar panels.
5A Lead acid battery charge controller
Digital voltmeter from Dealextreme
Aluminum composite panels to hold solar panels
Diodes to reduce li-ion battery voltage to start inverter (later you can disable them to save power)
Switches, power outlets, screws etc.
Step 2: Preparing Parts 1
Started to remove aluminum frames around solar panels. You should be very careful to not to break tempered glass on it.
Also removed big connector terminals and make them smaller.
Then fix them to aluminum composite frames by Sika WT40 PU adhesive and test them how to fit inside of the box.
When closed, panels perfectly protected during transportation and storage…
Added two parallel set of three diodes (in series) to reduce top voltage of li-ion pack when required. As they gets hot, prepared cooling fins by aluminum “U” profile. These parts located on left side of the box, well protected 😉
Also bend a small aluminum sheet to hold voltmeter.
Step 3: Preparing Parts 2
Also prepared paper labels for more professional look ;).
I’m printing them to photo paper by laser printer, then cut required size and use transparent tape for surface protecting.
Back side, using double sided tape and 0.4mm grey pet film for digital screen.
Then removed all “outer shell” of inverter to make it smaller…
Step 4: Installation
Here you can find schematics of solar power unit. It is Turkish, but added english explanations on it.
You can direct power to li-ion batteries or 12V external lead acid battery charging port.
Measure both batteries status whenever you want.
All connections completed based on this schematic and looks like spagetti 🙂
Actually you do need to open inside in normal operation, so it prepared as little bit tight. Also we have enough space for more li-ion battery packs (for more capacity) and cables etc. inside…
Step 5: Finished! 🙂
Here you can see control panel of unit.
Everything on same (protected) surface and easily accessible.
Here are main specifications:
- Very compact and lightweight, 300x400x65mm outer dimensions, 3.74kg
- Solar power, 20 Watts, max. charge power 1.1A
- Internal Li-ion capacity 40Wh (Sanyo batteries, over voltage, power, charge, temperature and discharge protected)
- Nominal charging time 3-4 hours
- Outputs: 220V AC, 12.6V DC, 5V DC (by using mobile cigarette lighter adapter)
- 220V output power is 100 Watts
- External fully automatic car battery charging port
- All outputs also available by external car battery
- All batteries are fused
- Digital voltmeter and charge status table
- All controls and outputs are on same side and protected…
I’ m planning to add led surface lights on empty surface for an improvement.
Cost is around 220 USD (including some mistakes) but value of the success is priceless :))