# Question about what to do with "Free to me" Electricity

Discussion in 'General Electronics Chat' started by seanreit, Aug 8, 2010.

1. ### seanreit Thread Starter New Member

Aug 8, 2010
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I have a storage unit in my apartment complex that has free 120VAC included with it. I asked specifically if I could charge my battery banks in there, and they said no problem, it's accumulated amongst the complex's overhead.

I primarily ride my 48V electric assisted bike for transportation and it has quantity 8 12Volt 12AH batteries (sealed lead acid). They are in two banks of 48VDC 12 AH for a total of 24 AH in parrallel.

If I wanted to transfer left over capacity from my bikes batteries at the end of the day to a 600w Grid Tie inverter to my apartment, I don't know how to calculate a couple of things.

1) Suppose at end of the day I have 6AH left of 48VDC, how big a chord would I need to tie my bike batteries to the grid inverter.
2) using the 6AH 48vdc how many days of doing this would I need to cover the cost of a 600W grid tie inverter (assuming I pay two hundred for the inverter).

My local killowatt hour cost here is about 11 cents. Oh, and how long would it take me to transfer the energy from the batteries to the grid tie inverter, as I would be doing it by having my wife drop an electrical chord off our balcony at the end of the day, and plugging it in.

If it's an hour, that's OK, if it's more than that, guess this is not worth doing.

Last edited: Aug 8, 2010
2. ### Potato Pudding Well-Known Member

Jun 11, 2010
684
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You will very likely lose money. The extra drain on your batteries will reduce their life so you might find that your bike is draining before you get home, let alone having charge to run an inverter.

Make your life simpler and spend the inverter money on high efficiency bulbs and appliances. Disconnecting unused equipment, turning up your refrigerator temp, and other ways to reduce your electric bill by reducing power usage make more sense.

If your power rates are \$2 a kW then maybe you can think about the type of scheme you describe but it would be anything but free between the cost of the inverter and the need for more frequent battery swaps.

3. ### seanreit Thread Starter New Member

Aug 8, 2010
2
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Gosh, I was hoping this I wasn't going to come across as someone who was trying to scheme. Whether I rode my bike the additional AH's or filled a little into the apartment, I was just simply interested in the math of it.

But I can certainly appreciate simplifying my electrical needs with your suggestions. I'm actually in process of building a vertical wind generator and a solar panel so I will be purchasing the grid tie inverter anyway, soon, I was just looking to see if it made economical sense to offset the cost with energy tied into the rate of my storage unit. Maybe it doesn't. Thanks for taking the time to respond. I appreciate yours and all others opinions. Regards,

4. ### marshallf3 Well-Known Member

Jul 26, 2010
2,358
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Even deep cycle marine batteries lose a ton of useable life if discharged much past 70% - it's the nature of a lead-acid cell.

I do however appreciate your thinking of this, keeping that attitude may eventually lead to something far more practical in the future. In the meantime do us all a favor and power a mosquito zapper off of it.

We've got a real energy conscience person at the corporation, in time I'm thinking about tossing together a wind generator to power the warehouse sound system off of just so I can say I'm doing it. A few hundred watts is nothing when you average the KWh we use during a month - I even qualify as a "Power and Light" customer and I utilize their "Time of Use" option as I can save money with it considering my peak demand isn't much higher during the peak rate hours in the summer months.

5. ### Ron H AAC Fanatic!

Apr 14, 2005
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6AH at 48V is .288 kWH, about 3 cents worth of electricity at 11 cents/kWH. It's gonna take a LONG time to amortize a \$200 inverter - 17 years if you do it once a day.

6. ### marshallf3 Well-Known Member

Jul 26, 2010
2,358
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Kind of like the car that supposedly air conditions itself from solar panels on the roof. If you could get that much power from solar panels you could run the darn car off it.