Choosing batteries for solar power offgrid or a battery backup system.

Choosing batteries for solar power offgrid or a battery backup system.

How to choose batteries for your needs and some tips on charging.

14 Comments on “Choosing batteries for solar power offgrid or a battery backup system.”

  1. I sure hope nobody listens to this moron. Listen folks, if you want a off grid battery buy a fork lift battery. I bought my for my system 25 years ago, I am not on the grid and never have been.

  2. I set up a small solar system using 2, 140 W solar panels and a 150AH, 12V Trojan battery with associated solar regulator to charge the battery and a 1500 W inverter to provide AC. I was disappointed that the Trojan battery failed after only 2 years and 3 months. I switched to a NiFe battery setup for 12V, because this type of battery is good for 20+ years. I am able to obtain about 0.5 KW/day on average. The NiFe batteries can run straight from the two, 140W panels connected in parallel, but I need to send voltage from nine, 1.2V cells so as not to create an input overvoltage situation for the 1500W inverter that was designed for Pb acid batteries. The dc voltage from 10 cells, which can be as much as 16.0V in direct sunlight, feeds dc/dc converters to power dc loads such as 12-24V LED lamps, laptop, cellphone, audio system, flat screens, and other electronic devices. It is also possible to power my refrigerator or freezer (not both) if I insert a timer between the inverter and the fridge. The fridge requires about 1000 WH/day, whereas the solar panels only produce about 500 WH/day, meaning I can only run the fridge for 12 hours or run it on a 50% duty cycle using a timer (15 min. on, 15 min. off).

  3. I got a system I built 5 years ago using a walmart deep cycle battery (the largest they sell). I originally built this for occasional use when the power went out (only 1 or 2 times in 5 years). I keep it on one solar panel (45 watt) (I have 2 more I don't connect), through a solar controller and feeding an 1800 watt inverter with digital readout for amp draw and voltage. I designed it to operate my refrigerator and chest freezer for indefinite periods as needed (if ever needed) whereby I'd connect the other 2 panels. I've checked the battery periodically and always has good volt readings and has worked when needed. I was able to build the entire system for around $700 back then (not sure what it would cost today). I've powered lights, fans, freezer and fridge for up to 14 hours during blackout without issues. I don't have to buy gasoline, worry whether the generator will start, etc. Maintenance is more or less making sure all components are working from time to time. I mounted the battery in a plastic battery box that is bolted to a $25 luggage dolly. On the front is my controller and junction box which has a voltage gauge and small service light so I can find the outlets during an outage. On top is the inverter which has the digital readout mentioned above. I can extend the dolly handle up for portability or down for storage (under a table). I estimate the entire works weighs about 100 lbs or so. Dimensions are the width of the battery box approx 20 inches by perhaps 16 inches height by about a foot deep. It has really been useful when needed. And I recommend this for a backup for emergency power. Don't want spoiled food.

  4. How do you monitor your 30% discharge. Do you have to manually do that and is there a device that will not let you discharge below 70% or some select-able level

  5. Great video. I am setting up a camper for retirement and want to use solar as I am going to be in BLM and National Forest so I have some questions.
    1. If I can safely vent my batteries are trojans better than AGM batteries in the long run. dollar per amp/hr used lifetime. Meaning does a AGM = 2 tojans over time
    2. If I use tojans how often do I need to check water – new and older
    3. What is the recharge time difference between trojan and AGM batteries

  6. You have a wonderful system there.  I have a total of 170 watt solar panels and 3 marine/rv batteries and 1 mat glass battery someone gave me.  You mentioned to charge your batteries once a month to full capacities.  I never heard that before.  My batteries show on an average 13.8 volts during the day and 12.8 at night time.  I only use my system as a back up in case I lose power during an earthquake.  Should I charge my batteries once a month to excite the electrolyte as you mentioned?.  Any help would be appreciated.  Again, you have a great system there.

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