Battery Backup

[lux1moonprince]

Hi everyone,
I'm thinking of adding a battery backup to my prep stores. Thinking of adding 2 X 220 amp 12v leisure battery's, connected to a mains charger that will topup the battery's once a week.
I only ever intend to use this if the power goes off and I'm happy once I've used it I can't recharge it.
I'm really looking at this to keep the kids occupied for a couple of weeks by allowing iPads etc to be topped up and to run a 12v Tv.
At a later date, I may add some panels to allow power up if the power goes off.
My questions are, should I look for anything specific in a battery? Can I use any charger? If I plan to set this up in a basement, do I need to be aware of any potential issues I.e. Fumes, risk of fire etc.
Thanks

[Mortblanc]

If working off mains for recharging then there is a device called a "float charger" that trickles current to the battery and keeps it topped off without overcharging. They are inexpensive and worth the effort.

Look for deep cycle marine batteries in the amperage rating you desire. Most of the proper batteries are going to be rated in amp hours. How many amps does the device draw and how many hours will the battery power it. Amps become more important and easier to calculate than converting it to watts and such. Most of your 12v appliances have amp hour ratings for this reason.

I have one deep cycle battery that is nearly 15 years old and still takes and holds a charge. It has been used in my caravan as primary power source for two years, in the house for emergencies and in the boat as a starter motor and to power the electric fishing motor. As of this summer it was still providing current on call.

One or two batteries are not going to power your house during grid down situations for more than an hour or two. It's a waste hooking them up like that. That use requires big battery banks with big solar panels. Dedicate your small system to lighting with 12v LED or florescent type lights and recharging the computer devices and phones and they will keep you operating for several days. You can recharge most devices right off the battery using an automotive plug. My 12v tv would pull my 180 amp battery down at an alarming rate. I missed the end of several GP races due to that.

Place your batteries on a wooden frame, not on the dirt or concrete of a basement floor. Even a board between the battery and floor is better than nothing.

A good panel for charging is handy, especially in the summer months. Not so much in your winters at the higher latitudes. Do not waste time with the small panels used for automotive dashboards. Go straight to a 45w pannel. It will actually charge the battery rather than just teasing it.

I lived off grid for two years in a self contained caravan and for one summer I had a 45w panel hooked up. All appliances were 12v and I was working a lot outside, only coming inside due to weather or darkness. I would keep the lights on for a couple of hours, read a little then go to bed. I did not have to recharge off mains power from April until October. When the daylight hours got short I needed mains for a recharge.

If you are running an inverter then you will pull down the batteries more quickly than if using 12v appliances. The inverter uses a lot of power to cool itself during the conversion. However, a high load inverter is handy for emergency use of power tools.

Remember that there are several tricks you can do with batteries of this type. One is that you can run jumper leads from your vehicle to the batteries and recharge them off your vehicle alternator. At one time I had a battery rack in the back of my pickup and a wiring harness that allowed me to shut off the car battery and transfer recharging power to the marine batteries. I would recharge the batteries on the trip to work and back each day, then plug the caravan into the battery bank when I arrived home in the evening.

You can also recharge off of a garden tractor pulled up next to the basement window.

[lux1moonprince]

Thanks Mortblanc, the detail to your reply is amazing. I feel a lot happier about doing this now.

[Straight Shooter]

many thanks MB great post !

[Lightspeed]

Re Charging: Halfords sell a good "smart-charger" that does the job MB described above.

We've had one f these in permanent operation for the last 5 years in an installation similar to the one you are planning and its performed perfectly.

[CharlesHarris]

For a house backup which will power a large inverter for well pump, AC or freezer, four L16 wet cell golf cart batteries with 400watt solar array and charge controller. You have to stagger appliance use, but can keep food cold, keep the sleeping area comfortable in a mid-Atlantic summer, run power tools, ham radio and such.

[harrypalmer]

Bump your solar array to over 1KW, not that much more expensive and will cope better in winter.

[Mortblanc]

You guys are replacing the 200-300 pound unit the OP asked about with a multi-thousand pound full house system.

[harrypalmer]

About a thousand dollars for the kit plus your deep cycle batteries. Do you have a scheme in the states where you sell 'spare' power you don't use to utility companies? Your system could pay for itself in a year or so.

Small generator and batteries will do a 'quick fix' for the OP I suppose.

[Mortblanc]

Oh yes we have the sell back power scheme, and it is a scheme.

In my area they stop paying for the power when they hit their quota and just take it.

Even then it is difficult to justify a full system in my area. I have an all electric home with both heat and cooling working. winters get and stay at -20 for a good part of the winter and most of the summer is above 30c. We had 30c temps this week for the first week of November and my AC was on. I cook, heat, cool and run a 50 gallon water heater plus lights and accessories. My bill runs about 75 pounds a month your money.

That kind of cheap electricity doubles or triples the payback time and does not justify the worry, inconvenience or expense.

I quit being the kind of miser that worries over the number of pennies it takes to heat up a teakettle long ago. I also quit paying out the wazoo just so I can thumb my nose at the system. An emergency system is cheap enough to install and works well for emergencies. Why try to live your life like it was a perpetual emergency when you only need the system two weeks out of a decade?