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Forum: Battery Power

24 August 2006

Sacmer – at 19:20

Ok, I know if I read every post of Alternate power for dummies archives I might gleen some info but I am lazy. I am thinking of small amount of battery backup for running computer, task lighting, small electrical appliance for short time. I am somewhat handy with home repairs but not a whiz and definately hate the math when it comes to watts/volts/amps etc.

Would something like this be useful or is it overpriced:http://www.mrsolar.com/page/MSOS/CTGY/portable

60 amp hour battery/3000 watt inverter/80 watt solar module

How much run time does this battery give you for DC appliances and how much if you used the inverter for all AC usage? How long would it take to charge with the 80 watt solar panel? Any educated comments appreciated.

lazy – at 19:24
anonymous – at 20:07

I should have also said I somewhat dread obtaining all above individual components and assembling them into an effective portable system without electrocuting myself.

pfwag – at 20:57

There are better solutions. The devil is in the details.

The key thing in sizing is watt hours. You have to put 10–15% more into the battery than you take out. Your solar panel will only provide its rated output when perpindicular to the sun. Clouds reduce the output even more. I haven’t done the math, but would guess that unless you are going to have your solar panel track the sun, the 80W module in the unit you referenced probably can’t generate more than about 300–400 Whrs on a cloudless day. That, however, is enough to run a few things for a few hours each day if you are judicous in your power use. That is also about the maximum you want to discharge the battery, assuming you are using a deep discharge storage battery.

25 August 2006

Sacmer – at 11:16

bump

Eccles – at 11:27

Sacmer - We can’t tell you run time without you tell us what you are running and what its power requirements are.

Note also that the inverter is a 1500 watt inverter with the ability to support a 3000 watt surge momentarily.

Just so you can get a feel for what the numbers mean for this setup. If you were to completely drain your ^) Ah battery (not something I would recommend doing), and if you were using the inverter at the 1500 watt level, your battery would be gone in 20–25 minutes.

Using the 80 watt panel, it would take you 2 sunny days to completely recharge that battery again.

Sacmer – at 11:45

Sorry, I forgot only 1500 watt inverter. Well, in the DC mode I was thinking of a DC fan and perhaps small (LED0 lighting as in a motor home. Obviously don’t have the product yet but just trying to get some ball park ideas. AC wise a laptop computer, perhaps something like 700 watt rice cooker for 30 min if the propane runs out.

Hillbilly Bill – at 12:02

Sacmer – at 11:45

My advice about the rice cooker, buy more propane.

Eccles – at 12:03

Sacmer - That 700 watt rice cooker would probably use just about the full day’s harvest of electricity on a good day. So it is doable.

But for cooking, there are better uses of the sun than to collect it, convert about 10% to power and throw the rest away, feed it to a battery which will lose about 15% of the power you feed it, then feed the power from the battery back out to an inverter which will lose about 10% of the power you feed it, send the rest to an electric rice cooker which will lose about 10% of the power you send to it.

You would probably do well to look into solar cookers if you want to use solar energy as a backup cooking method. Also, you would use less of your energy if you used thermos cooking to prepare your rice.

Hillbilly Bill – at 12:25

I’ll just post my experience in the ever-challenging world of alternative energy to give a benchmark.

One of the appliances I want to run if the grid is down is my breadmaker. I know there are lots of different ways I could bake bread, but I decided I want to do it this way for as long as possible.

I have a battery bank of three 115Ah batteries and a 1500W inverter. If I start with my battery bank topped up I can bake a loaf of bread with no problems. However, at the end of the 3 hour cycle my bank is at 60% and I need more than a full day to get it filled back up with the 60W of panels I have now.

Keep in mind that for 2 1/2 of the 3 hour cycle, the breadmaker does not use very much power. When it is cooking in the last 30 minutes, the heating element will draw about 500W for a few seconds and then click off. This happens every minute or so, depending on the ambient temperature. It is really shocking to watch the voltage and amperage guages on the inverter when that element is powered!

Originally I thought that I would be able to bake a loaf of bread, use the computer for a few hours a day, and watch a DVD at night on TV. To do that I will need more batteries and more panels. I have already spent plenty so I am scaling back my “wants” to fit the reality of the situation.

H. G. Wells – at 12:48

Some what off topic. Good deal on Duracell batteries at Walgreens (NOT RECHARGEABLE)

Duracell 16-pack AA or AAA, 8-pack C or D, On sale for $ 7.99

Then the walgreen rebates. Buy $20.00 of duracell and get a $10.00 Walgreens gift card. Also there is a $3.00 per pack rebate at Walgreens.

3 packs = $23.97 - $19 = $4.97 for 3 packs (+ TAX on $24)

So for $5 you can get 24 D size batteries.

These offerers are in the booklet near the checkout stand.

YES I normally use NIMH batteries.

26 October 2006

Closed - Bronco Bill – at 20:57

Closed to maintain Forum speed.

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