I have just ordered a 25 Watt Sunlinq PV solar panel and I am now looking for a solar battery charger device to store the electrons generated by the PV panel. Found this one but its limited for what it can do for the price.

http://www.brunton.com/product.php?id=604



So I'm thinking of designing my own to the following spec to give maxiumum flexibility, with the design being compact and portable and which can be used around the home together with the motor car in mind as well as for general field use.

Any other thoughts as to what might be useful. I would expect the design to weigh less than 1.5 to 2 Kg and be about the same dimensional size as a 0.8 to 1 litre circular cooking pot.



Specifications for a Portable Solar Battery Charger.

Features:

Input Voltages DC source; 4 - 30 Volts DC

Input Voltages AC source; 110-250V AC (Mains@ 50Hz or 60Hz) input.

Output Voltages DC; Continuous 0-24V DC output in 0.1 Volt Steps (quick menu programmable with standard voltages including 1.5V (for external charging of NiMh and NiCd cells) 3.0V, 4.5V, 5.0V, 6.0V, 9.0V, 12.0V,14.4V (for external charging of Deep Cycle Lead Gel Cells) 18V, 22V and 24.0V; Maximum DC power output typically limited to 40 Watts @ 12 V

Output Voltages DC; Double Standard +5V USB (500mA each) output connections.

Output Voltages AC; 200 Watts Mains Inverter (from external DC source) to both UK European (220/240V AC @ 50Hz) and US (100/127 V AC @ 60Hz) with 40 Watts (maximum) when run directly from the 12 Lithium 16850 Cell Array. Output AC (mains) being selected from the microprocessor control software operational interface.

Microprocessor controlled with 3 button Keypad and 2x8 character Alphanumeric back lit capable LCD display for Voltage and Current Monitoring of the Lithium Cell array together with discharge times and charging times and control of the various output Voltage and Current operational modes described below.

Lithium Ion rechargeable Cell Array 12 18650 3.7V 2200 mAhr Cells giving approximately 98 Whrs. Each Lithium Cell is individually replaceable with easy access within the device.

0.5 Watt PV Solar Cell to provide trickle charge to the cell array when no other DC or AC sources available. (possibly an optional within the design as this would be dependent of the form factor)

Operational Modes:

Lighting Mode - incorporating a lighting circuit with 2 heat sinked SSC P7 LEDS with variable microprocessor controlled output. (Light output for a combined output of 10W would be around 800 Lumen with around 9 hrs use – 2 Watts 150Lumen for 45 hrs use. Turbo Mode lighting would generate up to 1600 Lumen for 3-4 hrs)

Direct AC/DC Supply conversion Mode - to allow the 110-250V (Mains @ 50,60Hz) to be converted to the programmable output voltages (Typical 40W maximum @ 12Volts) allowing the device to operate as an accurate programmable DC PSU.

Direct DC/DC Supply conversion Mode – to allow the input DC voltage (4-30V) to be converted up or down to the programmable output voltages (Typical 40W maximum @ 12Volts)

Inverter Mode – to allow for external DC sources such as from Deep Cycle Lead Gel Cells (6V DC, 12v DC, 18V DC, 24v DC) to be directly converted to Mains AC (either US, UK European standards) to power conventional mains powered equipment (120 Watts Maximum).

Direct Mains Conversion Mode - Regulated US (100-127V@ 60Hz) to UK European (220-240V@ 50Hz) conversion and UK European to US conversion (Maximum 100W).

External Battery Charging Mode for Deep Cycle Lead Gel cells - Microprocessor charge (14.4V) and trickle charge control for external Deep Cycle Lead Cells from either Mains AC input or DC input i.e. Solar PV array.

External Battery Charging Mode (NiMh and NiCd)- Microprocessor charge and trickle charge control for NiMh and NiCd (1.5V) and from either Mains AC inputs or DC inputs i.e. Solar 12 V or 24 V Photo Voltaic array.

Double Standard +5V USB power output connections to allow connection of multiple USB powered devices such as Mobile phones, MP3 players etc which would be completely. Independent of any of the above modes.

Uh... your starting performance specs sound comprehensive. Have you priced components +> got a SWAG on material cost to make a prototype?

If one skips the mains conversion mode, any idea of cost reduction?

I'm interested to hear how this progresses.

Regards,

Tom

Are you sure you don't just want a big SLA gel cell?

For charging:
With a 25W panel you probably want a charge controller. Mains chargers exist for 110/240V 50/60Hz, and you can probably charge from a car lighter socket.

For using:
A small inverter will give you ac power. 12V direct from the battery is a useful voltage for many things, and there are car accessories that could be used as is (including coffee makers!). Finally, you can get USB power converters the plug directly into car lighter sockets to give 5Vdc up to 500mA, and there are a range of USB powered doodads that you can buy (that have no requirement for a PC, they just happen to use the USB-shaped plug for power).

A 7Ah gel cell is pretty heavy, but you could attach a fused lighter socket for general use, and (fused) Anderson PowerPoles for plug-and-play 12V applications, then you just need a bag or box to keep all the accessories together.

You could re-purpose one of the "emergency jump start" units that you can find at auto stores- it has a battery inside, a carrying handle, a lighter socket and often some sort of charge circuit. Radio hams use this sort of thing for emergency communication power.

Having said that, your specification is pretty complete and I wish there was such a device.

HTH,

A

Hi AyersTG,

The design is at a very early stage, it hasn't been designed yet!! Just trying at the moment to get a specification going with some feedback on what would be useful features and what would be pointless for various emergency scenarios in the office, home, automobile, marine or field environments in terms of power requirement over a 2-3 day period for example.

For example an 800 Whr battery pulled from a vehicle would be able to provide continous lighting using the 'solar charger' for a medium sized room for around 60-80 hrs.

A major part cost is going to be the 12 18650 cells. A pair will cost around $9

http://www.dealextreme.com/details.dx/sku.6979

So the cells are going to cost around $54

The SSC P7s costs are around $24 each so for 2 each will be around $48.

The microcontroller will be a PIC18F458, (already have some of these lying around with a PIC development board and PIC programmer etc) so these costs are essentially zero. Other semiconductor costs will most likely be covered by the 'send me a sample' approach.

The microcontroller will be at the heart of the design, using a firmware approach to control the switching DC/DC regulator, AC input switching PSU, Inverter AC output, SSC P7 LEDs and the Lithium ion cell array charger circuitry designs. The 'mains conversion mode' should essentially just be another part of the firmware.




The idea is to be as flexible as possible for the smallest and lightest device possible. Essentially the device would allow the use of a big external sealed lead acid gel cell (or even automobile or deep cycle marine type cells) to be used externally with the 'solar charger' and PV panel but also allow the use of readily available lightweight lithium ion cells to allow portability. (The 100 Whr Lithium ion array weighs only around 580 grams compared to around 3Kg for a lead gel equivalent cell)

When used with the PV panel it would allow charge control to recharge the lead gel cell or it could borrow some of the charge from the lead gel cell to store internally to the Lithium Ion cells to be used later. Some of the charged 18650 cells should be able to be removed and even used to power individual 18650 single cell flashlights for example.

I think you should first figure out how much power you will need for any given task. For lighting I would go with low voltage lights like LEDs, they are extremely energy efficient. I would also try to stay away from devices that require 110-volts AC, an inverter takes a lot of power to do it’s job. Also look into reducing your electrical needs before you build a solar / battery pack. Every watt you can save, is a watt you don’t have to generate. Solar panels are expensive and produce little for the money you put into them. And they take all day to do their job.

i use those 18650 cells in some of my lights stated capacity is 2500 mAh. I have 21 of them one was DOA lowest capacity was 2140mAh highest was 2330 mAh. dam good cells for the money .

http://www.candlepowerforums.com/vb/index.php? maybe worth a visit,read this thread http://www.candlepowerforums.com/vb/showthread.php?t=106242 if you are new to lo-ion cells

It sounds overly complicated to me. I understand your wanting to go lightest, but remember lithium ion cells have a shorter life, you loose 10-20% per year capacity so you have to figure in replacement costs. Also inverters are inefficient unless you have a really complex and expensive design so your going to be wasting a lot of energy there and your not going to run much of anything at all off of a handful of small cells like that (remember power in = power out so when you jump the output voltage up 10x you pull 10x more current on the input.)
As someone else stated, a 12v sla and some fuses and connectors will give a simpeler solution.

One thing that tells me it probably sucks a lot of power is the fact it’s made out of the same type of case they use for those super big car audio amps that kids love these days. Those cases are made out of aluminum, have fins and a fan to cool the components. Anything that generates that much heat is not too power efficient. Heat in any electronic device is the sign of power loss, all things generate some heat. When you have an unlimited power source this is OK, but when running on batteries, you want to keep this loss as low as possible.


I would also guess that if it burns out, your repair guy may not be able to find replacement components (ICs transistors switching diodes and the like) it’s common for companies for a device like this that is made in limited numbers to have custom components and proprietary numbering for the parts. This basically makes it un-reparable unless you send it to the factory that made it or to the importer (who will swap it for a new one and not for free.)


If you buy it, buy an extended warrantee if you can. Power amps have a fairly mortality rate, and it’s worth having a warrantee if you can get it.

I was looking at buying either this:
http://www.canadiantire.ca/browse/product_detail.jsp?FOLDER%3C%3Efolder_id=1408474396672502&bmUID=1213744311235&PRODUCT%3C%3Eprd_id=845524443298939&assortment=primary&fromSearch=true

or this:
http://www.canadiantire.ca/browse/product_detail.jsp?FOLDER%3C%3Efolder_id=1408474396673606&PRODUCT%3C%3Eprd_id=845524443299759&bmUID=1213744467168&assortment=primary&fromSearch=true

just what i need a portable battery backup to run small items...

peace
al

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