Brain Storming a small power system?

How complicated would it be to recharge a deep cycle battery using my car?

My recent 4 days without power has me thinking about a small DC power system to run some lighting and maybe small fans.

Should not be any problem at all if you are doing a direct swap. Are you trying to have it in your car only for charging? Say, a place in the trunk? If so, then you will need to make sure your alternator can handle the extra load, you will also need to make sure it is electrically isolated from the rest of the car electrical system. Or you could just buy a trickle charger and have it in the house; with adequate ventilation. Also, a single small solar panel would do the job.

2 cents

I ran across this inexpensive solar charger at the Northern Tool web site.
The idea is to place it in your car window, to charge or maintain the car battery. I bet it could be used in some other creative ways too. (?)

Might be a really cheap way to keep a 12v battery (or batteries) charged for some basic emergency lighting, etc ...

Those small solar cells will maintain a battery but they can't recharge a dead battery.

We have one of these which can be left plugged into a car's power socket/cigarette lighter to be recharged or just maintained. I worked great for running a fan, a lightbulb, charging my cell phone, and assorted other low-draw items when Hurricane Ike hit last fall.

From the manufacturer's website:
Product Features
* Runs 115-volt AC or 12-volt DC products anywhere
* Built-in 400 watt inverter
* Sealed, non-spillable 20 amp-hour AGM battery
* 250 PSI Air compressor for inflating tires and small sports equipment
* Jumper cables designed for safe and efficient jump-starting
* Built-in light provides illumination in emergency situations at home and on the road
* 3-digit display allows for easy battery status monitoring
* Audible alarm signals overheat and under voltage conditions
* Overload and over-temperature protection to ensure longer inverter life
* AC charger stored in the unit
* Recharge at home or from a vehicle

-Blast

Not so much in the car, as just in a carrying case where I can take it out and quickly connect it to my car's system to recharge it, then take it back inside the house to use when power is out for extended times.


Would one of these 12v power supplies work better????

There are a couple of precautions to consider with charing a deep cycle battery using a vehicle power supply circuit. First, as mentioned, a depleted battery can put a big load on an alternator, which isn't designed for such high peak current. You may damage the regulator and/or the diodes in an alternator unless you use an in-line current limiter on the charging circuit. I like to put a headlamp in series with the battery to keep the current flow at less than the max rated for the alternator circuit, although doing so will make the charge time longer, as it should be.

Another big consderation is the differecne between the make up of a deep cycle battery vs an automotive battery. Vehicle electrical charging systems are built so that the battery is constantly floating on a charge voltage, allowing a trickle charge to be constantly applied to the auto battery. This trickle charge keeps the battery at full charge, but a fully charge deep cycle battery is not made for this type of operation, and will fry if left to float on a trickle charge circuit. For this reason, once a deep cycle battery has reached full charge, it needs to be isolated from the vehicle electrical circuit. Again, having the headlamp in the charging circuit is a great aid for this. As the battery charges, the voltage drop across the lamp decreases, and the lamp gets dimmer. When the lamp is no longer putting out light, the battery is fully charged and can then be switched out of the circuit. An ammeter is a better indicator, but for the basics, this has been a good standard for battery charging for a long time.

This is the kind of system we used in a slide-in truck camper years ago. Go to an RV dealer and ask them to set you up.

Blast, that Xantrex unit looks like a really handy piece of equipment.
I like that the internal battery is "user replaceable" too.
Do you know what the expected service life is for the battery?
thanks

For your lighting I would go with high efficiency LED lighting replacement bulbs. Some of the LED bulbs are getting to 60-70 lumen per watt efficiency and compete with CFL bulbs although are still more expensive than CFL (the local Electricity supplier gives CFL bulbs away free of charge)



Anglepoise copy lamps from a local DIY store costing around $30 each. GU10 and E27 LED bulbs from DealExtreme

http://www.dealextreme.com/details.dx/sku.15070

http://www.dealextreme.com/details.dx/sku.12960

Each LED Bulb consumes only 3 Watts each

A typical room can be illuminated for around 10W (500-600 lumen) total for adequate emergency lighting. This would compare to 60-80W of Halogen or conventional tungsten lighting and 12-15W for CFL.



Standing floor directional Spot lamp with 3 x 1W 100 Lumen LEDs GU10s

http://www.dealextreme.com/details.dx/sku.16875

To power the lighting an emergency portable 40ah SLA battery with 300 Watt inverter can be used. (UK equivalent of the Xantrax power packs available in the US)

http://www.ringautomotive.co.uk/product_detail.asp?prod=1592

To charge the power pack a 45W or 60W Solar Panel kit could be used in conjuction with a solar charge regulator and setup quickly in an emergency.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=90599

A good demo is shown here for the 45W Solar Kit

http://www.youtube.com/watch?v=caeEyhJZnTs

A typical setup using a 40ah SLA battery would power a 10W lighting system for continuously for around 35 hrs (or around 3 hrs with a single 100W Tungsten bulb) without any solar charging, and almost indefinitely with the solar panel.

You could of course scale up the whole generating your own electricity using Solar PV and the only thing you would have to worry about would be this

Ours is more than five years old and still running with the original battery, though it doesn't get too heavy of a workout. Maybe 4-5 weekends per year not counting the hurricane.

-Blast

I put an equivalent Harbor freight cell for trickle charging the generator battery and it has worked great for years now, I randomly check it and it fires right up. These go on sale from time to time down to $9.


http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=44768

Lots of excellent comments above.

I have a couple of PV-solar/battery/inverter setups, one for my bare-bones office upstairs and one for a cabin on my property.

Some random observations:

- I find 45-60W of generation and a 60Ahr battery the minimum practical configuration for daily use. You can get by on a lot less for lighting only (esp. LEDs!) but if you want to power tiny fans or laptops, don't go small.

- You can scrounge efficient 12VDC mini-fans from the power supplies of old desktop PCs. Wire two in series and connect to a battery; they move just enough air to be useful.

- It's much cheaper, per watt, to buy discrete components these days (inverters and deep-cycle batteries) than to get all-in-one units like Xantrex (though I have had good luck with their products).

- Gel-cell batteries can be stored/used inside safely, because they don't normally vent. But be cautious in freezing climates: you can't charge a gel-cell when it's frozen.

- It's cheaper to spend money on super-efficient appliances than to add extra generation capacity (for photovoltaic setups anyway).

- Wal-Mart in Canada has just started stocking inexpensive LED bulbs, both 120VAC and 12VDC. I bought a number of them, and based on a couple weeks' use, I'm quite impressed. My office/computer desk now consumes 2W for lighting, and if I need to I can power these off-grid indefinitely. The brand is "Lights of America" (no affiliation). [EDIT: prices in CAD: 8.50 for 1 and 1.5 watt bulbs, 10.00 for 2 watt, 14.50 for 3.5 watt, 30.00 for 3 x 2 watt linkable pucks and 5 watt singles.]

- If you have a photovoltaic/battery setup, you're flying blind without a multimeter (and taking chances without a charge controller). I do like benjammin's idea of a headlight in series as a field expedient charge indicator; though I don't think it would work with PV panels.

Good luck!
Doug

I'd also look into some of outdoor solar powered lights, with a bit of ingenuity they can easily be adapted to work as emergency indoor lights in the case of a power outage.

I've actually considered that. My local hardware store has a set of 6 for 29.99 and I've thought about trying them.

Can't beat em for the price. I wouldn't want to read "War and Peace" using one but it couldn't hurt in an emergency.

The type with the solar cell on an extension are easy enough to rig up.

I've seen some where each light has their own cell, shouldn't be too hard to hack into them and run some wire to get the cell outside and the light inside.

I was thinking of the ones that have the spike to stick them in the ground.

A small base with some Styrofoam in it, and instant lamp!