Choosing Batteries for your Solar / Renewable Power System
- Filed under: Solar Power and Off-Grid Living
- Date: Apr 22,2008
Most solar and wind powered set-ups have the same basic concept. The sun or the Wind creates power, which is then stored in batteries. That way, even when the sun isn’t shining you have power. Also, the batteries act as a kind of power regulator. This article will explain what kind of batteries you need, and how much power that will give you.
Almost all solar installs require Deep Cycle flooded Lead-acid batteries. Deep Cycle technically means that it has been designed to be drained a lot before being recharged. Don’t be fooled though, although they are called “Deep Cycle Batteries”, if you want them to last for the longest amount of time, you don’t want them to discharge more than 30-40% MAX.
A Quick lesson on the power that is IN a battery:
The storage capacity of the batteries are usually calculated in Amp Hours. So if you see a battery that is labelled 6 Volts, 200AH it means it can technically put out 1 amp for 200 hours, or 200 amps for 1 hour. Since watts = volts * amps, a 200 amp hour 6 volt battery would “hold” 1200 watts of power for future use. If this is new to you, you should read “Calculating Power Consumption for your renewable energy system”
Sorry, no car batteries :
I apologize if this crushes your hopes and dreams of cheap batteries, but you should NOT use Car Batteries for your renewable energy system. Car batteries are meant to supply a high amount of amps in a very short period of time. (Just enough to start you car) They would work if you used them, but not for very long. (A few months maybe depending on how fast you get to charge it)
Golf Cart Batteries :
The most common batteries used in solar energy / renewable energy are golf cart batteries. They are pretty good at handling deep discharges, and have a decent life expectancy for the price. (2-4 years depending on how they’re taken care of) Golf Cart batteries are usually 6 volts, and about 200AH. Since most renewable energy systems work on either 12 volts, 24 volts, or 48 volts, you need to buy these batteries in pairs and connect them in series / parallel to get the desired voltage. (When connecting batteries in SERIES, the voltage of the batteries add up, but the AMPS stay the same, when in Parallel, the voltage stays the same but the amps add up - I will dedicate a post about this soon) I get the kind that has 3 caps on TOP that lets you directly access the inside of the batteries for maintenance. (To top off the water level or to check the specific gravity of the batteries to know EXACTLY how charged they are)
Other Deep Cycle Lead - Acid Batteries :
Forklift Batteries : If you can get these, and afford them, TAKE’EM ! They are the BEST batteries for renewable energy installations. They’re just like the golf cart ones, but with a MUCH higher life expectancy. They are very heavy and expensive.
Gel Cell batteries : Gel Cell batteries do not require any maintenance, do not put out any gasses when being charged a lot, are sealed and can be placed in any way. These batteries are usually fairly expensive and have the same life as the golf cart batteries if they’re not discharged too often. (2-4 years) If you get a good deal on them, it would be worth using these batteries. Charging these batteries requires a special charger however. 
RV / Marine batteries : I see these at Canadian Tire and Wal-Mart. I would stay away from them unless you’re really in a jam and don’t plan on making these batteries last forever. They’re almost as bad as car batteries, but not. 
(They will last a little longer)
In conclusion, I would recommend getting Golf Cart or Forklift Deep Cycle flooded lead acid batteries. Before buying batteries however, you need to know how much power you require to run what you want to run. You can use the same steps as my article about how to figure out how many solar panels you need to decide how much power you need every day and then how many batteries are required. (Don’t forget that you only want to use the top 30-40% of what your battery bank can actually hold!)
If you’re looking for LOTS of information on solar power and wind power systems, you might consider buying these sets of e-books that are filled with tips and tricks for solar power.
Thanks for reading and good luck on any future / current projects ! Let me know if there’s something I should add to this article ! (email digitalmind (AT) techienation (DOT) com )
8 Responses for "Choosing Batteries for your Solar / Renewable Power System"
[...] Choosing Batteries for your Solar / Renewable Power System(2-4 years depending on how theyre taken care of) Golf Cart batteries are usually 6 volts, and about 200AH. Since most renewable energy systems work on either 12 volts, 24 volts, or 48 volts, you need to buy these batteries in pairs . [...]
Thanks a million for this article. I’m looking into how I can store power generated from solar cells and maybe even a steam engine. This post has given me some essential tips.
Cheers, Simon
Digg
I want to build a back up solar power system I will propably start small as I want to power a couple of misting fans and some florescent lights . My question is I have seen a modified sine wave inverter at harbor freight tools that is 2000watt / 4000 watt surge this is larger than I would need but if i wanted to expand the system i would have the capacity . Is it alright to use this size an inverter in a small system ?
Hot in the arizona desert
thanks Tom
Digg
I want to build a back up solar power system I will propably start small as I want to power a couple of misting fans and some florescent lights . My question is I have seen a modified sine wave inverter at harbor freight tools that is 2000watt / 4000 watt surge this is larger than I would need but if i wanted to expand the system i would have the capacity . Is it alright to use this size an inverter in a small system ?
Hot in the arizona desert
thanks Tom
Hi Tom,
this really depends on the size of the battery bank that will be connected to this 2000 watt inverter. If you’re connecting a 3000 watt battery bank to this inverter, then no ! When an inverter is turned on and connected to a battery bank, even if there is no load, it’s using power. The bigger the inverter the more power it wastes while turned on, so you don’t want to get an inverter that’s WAY more than you can handle, but you do always want to get an inverter that takes into account some future expansion… so basically it all comes down to how big your battery bank is and how much “recharge power” you have (in solar panels, or a generator, or whatever). Give me more details, and I’ll send you more too !
hi Digg
Thanks for the reply on inverter. basically I’m trying to learn as I go so If there is any books that you could recommend that would be geared to the beginner that would help. Cost wise I was looking at purchasing 6 trojan t-105 6volt 225 ah batteries and connecting them in series. I would like to power them with a couple of sharp 175 watt blemished panels I saw if still available . anyway I would like to be able to build out about 350 to 400 watts from the panels.
Ultimately I would like to be able to operate the two misting fans a couple of florescent lights and if possible be able to filter the water in a small 8000 gal. pool in the event of a major emergency. Don’t know if this is possible on the same system as it seems that any option for the pump would required a 12volt pump for efficiency also after reading a couple of articles I’m thinking it would be better to spend the extra money for a true sine wave inverter instead of the modified one I mentioned
Thanks again Tom
Hi Tom,
There are tons of books out there to help with solar power, but I find that you can learn it all for free by browsing the internet and trying things out. If you really want to buy some documentation to have it all in one place, there’s a link near the bottom of this post that has a kit of solar and wind books that people seem to enjoy. It’s affordable and you can get your money back if you don’t like it. (but don’t wait to report that)
I can offer you lots of free help instead though.
It just involves a lot of back and forth with questions and stuff… Here we go ! :
Are you planning on a 12 volt battery bank ?? With 6 batteries, that seems to be the only combination that works. (These T105’s are 6 volt batteries, right?)
The reason that’s my first question, is because it’s rare to see 175 watt panels that output for 12 volt charging. Usually panels over 100 watts are designed for 24 volt batterybanks or more.
All that means is that you need either 2 more batteries, or 2 batteries less.
Let me know and I’ll send more details about the specifics of what is needed for your project.
DigitalMind
Hi Digg
you were right about the panels I was looking at 175 watt panels are rated at 24 volts not 12. So what are the benefits of 12 or 24 volts.I was going to build a 12 volt system with about 300 watts of pv panels.
Thanks Tom
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