Battery usage configuration

lalakai

Maybe I'm making this harder than it seems.  Trying to set up a simple system to take AC or solar energy, put it through a battery or batteries, while pulling from same batteries with inverter.  Part of this reasoning is to develop a very stable consistant power source that will be converted back to AC.  There are computer UPS systems that will take the AC current, run it through batteries, then convert it to pure sine wave output.  I want to do the same with the battery system I use with my solar panels.  How could I set it up for a single 12 volt battery, or a series of batteries linked together??  Any input would be appreciated.  Thanks

vtmaps

Number 1 question:  when you are drawing power from the batteries, how much are you drawing, and for how long?  In other words, what are your loads?  Systems are designed to power loads.  If you don't know the load, you can't design the system.

--vtMaps

BB.

Yes... Functionally, that is a simple system to implement as you state.

With Lead Acid Batteries, you do run into a bit of a problem because deep cycle batteries do not like to float for months at a time. And float service batteries (again, Lead Acid) do not like to deep cycle (may only last a few hand fulls of cycles, or a couple of years of float+cycle service).

The rule of thumb that seems to have general acceptance here (I do not have the experience to confirm or deny)--You want to cycle your Deep cycle battery down by ~25% discharge about once a month, then recharge to keep the battery reasonably happy. So, turn off the AC main/battery charger and let your loads run directly from the battery bank.

If you are into a bit more cutting edge--Replace your battery bank with LiFePO4 type batteries. They are looking very interesting. Should give you both long float and cycle life. And they are good with relatively (compared to lead acid) high discharge current (if you only need a few hours of backup power--keep the battery bank small).

An Iota battery charger with an IQ4 module would seem to be a good fit. Although, the Iota battery chargers are not very "generator friendly" (not a "power factor corrected" power supply).

http://www.solar-electric.com/batteries-meters-accessories/bach2/bach1.html

Or you can go with the (near mythical) TC2--Should be a good supply.

http://www.xantrex.com/power-products/battery-chargers/truecharge-2-2.aspx

Or an integrated AC Inverter-Charger. Can be very nice units... But with all-in-one units, if something fails, the whole unit is down.

-Bill

lalakai

vtmaps said:

Number 1 question:  when you are drawing power from the batteries, how much are you drawing, and for how long?  In other words, what are your loads?  Systems are designed to power loads.  If you don't know the load, you can't design the system.

--vtMaps

when I started the first system I didn't have a specific "load" target in mind.  I wanted a portable power system that could operate simple electronics, portable LED's, while being able to be recharged by multiple methods (AC, solar, DC).  That system was based on a single 12 volt truck battery, supported by 2 140w solar panels.  The next unit was nearly as portable but used 2 6 volt batteries linked for 12 volt output.  The 2 solar panels can't fully recharge the 2 batteries in a day with full light and I knew that going in.  The biggest power draw I've pulled from the battery is a portable LED work light system that uses 1.1 amps per hour.  The primary focus is simple mobility.  Switching to a pure sine wave inverter allowed me to use the system with more sensitive electronics.  Part of that research also identified that quite often the AC current from a standard house outlet isn't real "clean".  My tv shows a difference when it's being used with the pure sine wave inverter, so I started to look at power conditioners but soon realized I could use my battery system instead, if I could set it up so I could charge the battery while drawing from it.

BB....your info on discharging the batteries once a month makes sense.  The charge controller I use has a maintenance cycle meant to refresh the battery and I wonder if that would have the same effect??  Something I need to research more.  Thanks

BB.

Usually, the "maintenance cycle" is a timed Equalize Charge cycle... Not the discharge by 25% and then recharge I was talking about.

Whether you like once a month EQ (to "stir the electrolyte"), EQ when "needed" (when cells are >0.015 to 0.030 or greater between high and low cell), or whatever--There are justifications that can be made for either.

-Bill