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I just bought 50W solar panel with charge controller. Can I use standard Car Battery (Liquid type)?

The battery is planned to be used to power my night lights at the rooftop garden

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    Are you wanting to charge a battery for a vehicle with it? If not, then you might get a better answer if you explain what you're planning to use the battery for. This is especially important if you're wanting to fully drain the battery as I understand car batteries don't handle that well (it drastically shortens their useful life).
    – Highly Irregular
    Commented Mar 8, 2016 at 8:38
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    That's two questions in one. I suggest you edit the last sentence out, also because it's very easy to search for yourself, e.g. goalzero.com/solarlife/2013/05/28/…
    – user2451
    Commented Mar 8, 2016 at 10:44

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There is no "best battery." There are different kinds of batteries for different applications. Here are some things to consider,

  1. What voltage do I want? (Most DIY projects pick 12V because they want to run 12V appliances built for RVs.)
  2. How much power do I need (instantaneous power)? Eg. do I want to run a Microwave (fairly high), just a couple of lights (pretty low), or start a large engine (very high).
  3. How much energy to I need to store? Eg. do I want to run that Microwave for one minute each day and a light for one hour, or do I need an hour for the microwave and five hours for those lights?
  4. What temperature is the battery going to have to endure? (If the battery is going to have to charge below freezing, that eliminates any kind of lithium. If the battery is going to go below -15° F (-26° C) then you probably don't want Flooded Lead Acid unless you are willing to keep it fully charged.)
  5. Is space and/or weight an issue?
  6. What's my budget? If your budget is pretty low, you are pretty much stuck with car batteries and low budget golf-cart batteries. If your budget is high, you can go all-out with lithium or Ni-Fe (Nickel Iron). (Lithium [LiFePO4] is the ultimate for performance, is smallest and lightest, and has better life than lead acid. Ni-Fe is the ultimate for lifespan and durability but is lower in performance.)

As I said, there are many different kinds of batteries and each one has it's purpose. Here are just a few to give you an idea...

The Lead acid group

These are the cheaper batteries and each of these sub-catagories are available in "Flooded" (needs maintenance), Gel, or AGM. Both of the latter are maintenance free.

  1. Shallow cycle, or "car battery." These are high performance (they handle a lot of amperage and instantaneous power) but they have a low life and they don't like to be cycled (drained) very deeply.
  2. Marine "deep cycle" batteries. Don't let the name fool you, these batteries are not meant to be deeply cycled either. They can be cycled deeper than a car battery and have a longer live but they can't handle as much amperage.
  3. Budget friendly golf cart batteries. These get better life and deeper cycling than marine batteries but again, they lose some amperage (performance).
  4. Commercial Batteries. These include high end golf cart batteries and many "solar batteries." These are built for deep cycling and lower amperage still.
  5. Industrial Batteries. These include the most rugged, most durable Lead Acid batteries available. They have the longest life, and the deepest cycling but also the lowest performance and amperage relative to the size of the battery.

Most applications where you need commercial or industrial batteries, you need a lot of storage so the bank ends up large enough that the lower amperage is not a problem. Whereas a car battery doesn't need to store a lot of energy but it needs to deliver a lot of power all at once.

Lithium Batteries

Lithium batteries are very expensive and there are many types that are not really safe and (no matter what the manufacturer says) if you charge a lithium battery of any kind while the internals of the battery are below freezing, it will significantly shorten the life and increase the fire hazard. The LiFePO4 (lithium iron phosphate) is a very stable battery that will outperform and outlive any Lead Acid battery (of the same size) if it is not overly abused.

Ni-Fe

Ni-Fe batteries are comparable to industrial lead acid batteries but they have substantially longer lifespan and better deep cycling. A well maintained Ni-Fe battery will outlast a lithium battery by a long shot. These batteries are very expensive so you need to make sure you're getting the right ones the first time.

If you give us more details on your project, I can add a couple of details that might help you decide what you need.

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  • Hi Max , thank you for brief explanation. My project basically is to power night light around my rooftop garden compound. And I have 2 used car batteries for this project. I live in equator line and looking forward if the power can light the garden for 5 hours (evening to midnight)
    – Pet
    Commented Mar 9, 2016 at 2:02
  • @Pet That sounds like a fun project. I always say that if you have something that is free, go ahead and try it... you have nothing to lose. I don't know what kind of night lights you are using or how many but I would guess that it won't be too much power and the used batteries might work out great.
    – Maxfield Solar
    Commented Mar 9, 2016 at 3:37
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How about a much shorter and perhaps easier answer?

Check out saltwater batteries. They are quite large because of the low energy density, but are also inexpensive and many consider to be well-suited to low-cost energy storage.

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  • Do you have experience with these salt water batteries? I've heard a lot (both good and bad) about them but I haven't actually seen them or talked to anybody who has used them.
    – Maxfield Solar
    Commented Mar 9, 2016 at 3:40
  • I have a friend that has been building solar energy systems for several years. Even his father's yacht is solar. He is switching to saltwater batteries when his current set fails. He has been researching this for years. That's all I have at the moment, but I could ask him for his research.
    – Daniel
    Commented Mar 9, 2016 at 4:01
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I don't think there is a "best battery". this depends on your purpose and usage of the battery. If you would like to charge your solar panel for long time or if you are welling to have this for couple of hours extra. Deep-cycle, lead-acid batteries have been employed in renewable energy and reliably used in off-grid applications as your case here. Typical deep-cycle, lead-acid batteries cost about half as much as lithium-ion, so maybe you can save some money.

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