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I have stressed batteries for so long, always falling on deaf ears. The capacity of the batteries in amp-hours determines what you can run off your system. How you charge the danged things, is another matter altogether. You can argue about that all day long. You can use solar panels, wind turbines, steam, generators, or a bicycle for all I care. But your batteries are the heart of the system! I don't care what else you have. If you're wasting too much time on how the batteries get charged, maybe you should re-think your system, and what you want to run off it.
I wish it was as simple as arguing. I'm good at that.
To the uninitiated, it would seem that you can treat a battery much as you would a can to store gasoline. Stick the hose/charging current in place, and fill 'er up. It doesn't work that way, although the more expensive technologies approach it.
Without getting WAY too technical for the thread, here are some basics that HAVE to be kept in mind.
I'll use a standard 12 volt lead-acid cell as an example. If you look on the battery specs, you may see something like:
500aH. That is 500 amp hours and is the nominal capacity of the battery. IF you hooked it to a resistive drain, you (in theory) could run a one amp twelve volt lamp for five hundred hours, OR a ten amp lamp for fifty hours. That is strictly theoretical, based on a new battery, and has little in common with reality.
In reality, you can only use 50 of those amp hours before recharging the battery or you risk damaging it. In an emergency, you might use 100 amp hours, knowing that you have shortened battery life. If you use more than half the total capacity before recharging, you'll be bringing it to the recycling center shortly.
What about recharging? Batteries have something called "internal resistance" and can only accept being recharged at certain rates. If you sit and watch a car battery being charged by a charger that contains an ammeter, you'll see it first hand. The first five minutes, it might charge at 30 amps, but then the meter will begin sliding down and generally, if the battery is any good, will level off at one or two amps for a LONG time, meaning ten hours or so. You CANNOT store energy into the battery faster without having it reject it or damaging the battery.
Why does this matter? Those first five or ten minutes when it is accepting energy at a good rate is called a surface charge. It means exactly that. The surface of the plates are accepting the energy. The problem is that unless you continue charging at the low rate, that surface charge will quickly get used the next time the battery is powering a device and it won't have any stamina to continue powering the device, but go almost immediately to a discharged state. The long slow charging is vital for the life of the battery and proper operation.
Now look at generators - they are made so that they can give that initial surface charge, but waste huge amounts of fuel in the long slow charge. With solar, there may not be enough ensolation on cloudy winter days to fully charge a battery set.
We are all used to car batteries. They power the high amperage starter motor for a few seconds, then the alternator on the engine kicks in and immediately begins recharging the battery and taking a lot of the electrical load of the vehicle. Other than being hot or cold, the car battery generally lives the life of Riley.
Alt energy batteries don't exist in such luxurious surroundings. In comparison, they are horribly abused. Even a trolling motor battery gets a proper recharge after a fishing trip. AE batteries might go for days before getting a proper recharge.
I have ideas on how some of the problems might be solved, but I have not verified them. Until those issues are resolved, be aware that batteries are expensive, you will likely need ten times the capacity that you think, and if you mess up, you will destroy them.
I bring the above to your attention as a caveat. You can believe it or not. Having gone through a few batteries myself, and read the same basic spiel from Richard Perez, I'm pretty convinced that I'm correct.
Harry that's a good read. I run a 18Ah batter as stock in my kawii Nomad bike. it's a 06 and the battery is still the same one.
I run a Shumaker auto float anti sulfation pulse charger at 1,5 amps and apx 14dcv.
As soon as i am done riding and have my gear off the bike, i plug it back in. I run a full time digital volt meter too, 24/7 til the battery comes in for winter, where it stays on that same charger in 55 degrees constant (cellar).
Others on the bike site (all Nomads) have replaced their batteries by now or are planning to, while i plan to use this one untill I have no choice.
Readings i get after just starting the charge are in the middle 14.5's and drop quickly to hoover at 13.33.
The past 5 years if I left the charger off 3 days and did not ride those 3 days the reading was 12.80dcv.
This summer that has changed to 12.79 dcv i don't think i will worry much yet.
One problem I had with this thread was no genni made is as good as a genni with a battery a bank. But then you don't need a genni.... You need a photovoltic array and a larger off line battery bank for all the time.
I have a friend here in cloudy NH that makes more than he wants and he can't sell it since he is off grid. he has had to take some of the cells off line even for in winter on cloudy days,
I wish I could rep you guys for each post, but I have to spread the wealth. Incredibly helpful information in this whole thread.
My husband is planning to build our solar panels and run the house lighting system (no motors) off them. He wants a stand-by generator for those times power goes out due to storms, etc. He has talked of some day getting batteries but we aren't trying to go completely off-grid, just to handle the what-ifs. I know he'll find something in this thread to help him decide what/how to do something or even what kind of generator to get.
If you just need emergency lighting to get around, the little booklights from the dollar stores will do the job. I have one that I modified to use 3 AA batteries, using a resistor and a slide switch, and the thing runs for months. They won't be terribly bright, but used close up they are enough to read by.
Ah means amp hours. In theory a 12 volt batter marked 14, or 16, 0r 18 Or 30 Ah will run a item rated at 1 Ah for the number indicated.
Ie: 18 Ah in theory will run a 1 amp item 18 hours. Or it will run a 18 amp item 1 hour, and can run a starter motor on a vehicle that draws apx 365 amps a few seconds.
DCV just means Direct Current Volts, which any battery is, from hearing aid, wrist watches to car size batteries.
ACV just means Alternating current volts, and these is no such thing in a battery and this type of electricity must be generated by one means or another.
Cars use alternators these days that make ACV, but 1/2 of the power the alts make is lost as waste current in the form of heat, passing thru diodes that only allow current to pass one way.
Auto Float chargers turn on and off as demand is called for by the specific battery it is hooked up to.
Anti Sulfation Pulse is a means of working the battery internal plates to keep them busy and not allow sulfation death.
Small batteries like motorcycles, lawn tractors, scooters, golf carts, and the like will die a early death from plain lack of use, and can die as early as 90 days of no use.
Car batteries are rated in CCA Cold cranking Amps, and will also die early from sulfation death, but it will take longer.
My car has a battery in it that I don't recall where or when i bought it, but has blue over spray paint on it from when i painted the car in Spring 2002. it is not on a charger all the time, but it is part of the time and that is why it has lasted more than 10 years ...... so far.
[quote=Mac_Muz;26041420]
ACV just means Alternating current volts, and these is no such thing in a battery and this type of electricity must be generated by one means or another.
[quote=Mac_Muz;26041420]
One caveat here for clarity, voltage is the rated potential of a battery, amps (in the form of electrons), are what are stored and do the work, AC or DC refers to if the power is alternating (AC) which means the polarity is switched at a frequency, in the US it is usually 60 times per second or 60 cycles, where DC or Direct Current is only one polarity and stays that way.
A battery is only DC because it cannot change polarity.
For a system operating from a battery backup you will need an Inverter which changes the voltage from DC (battery) to AC (house voltage).
There is also a step up transformer that takes 12 Volts DC and steps it up to 120 Volts AC, but Ohms Law states that if you step up the voltage, you step down the current proportionally.
This means a battery with a stated value of 12v DC with 500 amps once the electricity passes through an inverter will be 120v AC with 50 amps potential.
In my state for alternative systems the usual rateing for an off grid home is to have batteries for 3 days supply of power with "no sun" meaning cloudy where the amount of charge from solar cells is of no useful level.
In addition to that 3 day supply, you also need a generator in case the storm or clouds or whatever go longer than 3 days or if your energy demands exceed normal daily use, which they probably will during a storm with additional lighting etc.
Usually for a solar system a battery system is a must as the solar cells will trickle charge the batteries and your use is from the stored energy as it takes a lot more cells to produce enough electricity to operate directly off of the cells, plus the cells don't work at night or on cloudy days.
Just a couple things to throw into the mix.
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