Battery / Inverter vs. Generator for backup

[Perry]

I have been using an 1250 / 2500 watt inverter and a single 105 AMP-HR battery to build a spec house (no power yet). I run up to 4 compact flourescents and various power tools all day long, then bring the battery home each day to charge. I have also used a smaller inverter to power a few things our house (computer, TV, lights) when we lose power, which happens quite frequently here in the sticks.

My question is: Wouldn't a battery-inverter combination serve the purpose that many people buy a backup generator for? It would seem like if you have installed a 115 V well pump and don't use electric appliances (stove, hot water heater, etc.), you could certainly run a few lights, computer, one fridge and the well pump for at least a half-day or so if you had four 100 AMP-HR batteries. If the power outage was longer, you could start a vehicle and charge the batteries to keep the fridge going.

I know a generator would probably be cheaper and also allow 220 volts, but my ulterior motive would be to have the start of a PV system. Plus, I hate the sound and smell of a generator. With just my single battery setup I'm using now, I have a feel for how much energy (KWH) is available from a single battery.

[Mike90250]

Yes, for short term (power outages and such) a generator is a less expensive alternative than anything else. As run time and power demands increase, adding a battery, charger & inverter lets you reduce generator run times, and then even adding solar and charge controller, will reduce generator run times even more. At much greater costs. ($600 for a 200W panel, or $3 for a gallon of gas ? )

RV's do this in a fashion , a couple "house batteries" and on-board generator that tops them off.

[Sunking]

I have a feel for how much energy (KWH) is available from a single battery.

So how does it feel like?

12 volts x 100 AH = 1200 wh of which only 600 wh is usable or 0.6 Kwh

[russ]

The CFL lamps should just about take care of the battery - after that it is into no mans land - being ruined too quickly.

[Perry]

So how does it feel like?

12 volts x 100 AH = 1200 wh of which only 600 wh is usable or 0.6 Kwh

While I understand that only a load test or hydrometer test can accurately determine the state of charge......

I can work all day using a couple of Compact Flourescents and using my skill saw & screw gun and other various tools and (after three months of doing so) have not yet run the battery down enough to activate the low voltage indicator on the inverter. Also, my 10 amp charger rarely draws more then 5 amps when initially connected to the battery, so I'm figuring I haven't been violating the C/2 rule. Also, after using the battery, I immediately start the charging process to avoid sulphation damage.

Of course, during the framing stage of this project, I also used a cordless skill saw to do some of the cutting.

AS far as battery life goes.... even if I have drawn down the battery more and 50% subjected it to sulphation; the battery only cost me $80 and I have already saved more than that in gasoline by not running that noisy, stinking generator for 3 months.

[Perry]

The CFL lamps should just about take care of the battery - after that it is into no mans land - being ruined too quickly.

Running all 5 of my CFL's uses 100 watts of power, which means I can run all five for 5 continuous hours and still have a more than half charged battery. As I usually only run one or two at once (and turn them off when I leave the room), there is plenty of power for intermittent power tool use.

[russ]

Hi Perry - Right, the battery is a business expense and nothing more from your viewpoint.

Perfect solution for your construction.

Russ

[Perry]

Hi Perry - Right, the battery is a business expense and nothing more from your viewpoint.

Perfect solution for your construction.

Russ

Russ, I've used deep-cycle batteries for years to run my trolling motor and for car camping never knowing about the taboo of running them below C/2, leaving them uncharged and leaving them all winter without periodic recharging. Surprisingly, they still seemed to last 4 or five years! Maybe I just got lucky.

Of course, If I make an investment in multiple batteries, I would get myself a load-tester, hydrometer and a three-stage charger to protect my investment.

Thanks, Perry

[Perry]

how does it feel?

So how does it feel like?

I shoulda said it feels like a big, heavy bag of columbs.