Battery for a small Renogy system?

[hausmutti]

I'd recommend a group 27 Marine battery from Walmart or Sams Club. If you're like most people, you're probably going to kill it so get a cheap one with a good warranty.

That'll be a flooded battery so you'll have to keep the water in it full.

My son is a software developer and I told him I saw an opportunity for someone to develop an app that would remind me to do things like check battery water

 

[Trebor English]

So, you don't worry about getting stranded?

 
No.  
 
I have a RC (radio control) toy amp hour meter to monitor solar panel input.  I use an electric clock to keep track of fridge compressor run time.  I use a voltmeter to observe battery charging voltage looking for 14.2 with a couple of hours of sun left.  The key is never to run it down too much and prioritize recharging over use.  Use less than gets generated.

I have not spent a bunch of money on equipment for a good BM.  I only have the typical bucket with air tight lid and a box of trash bags.

 

[frater secessus]

I use Google Calendar for that kind of thing. It can do popup or email notifications. I'd think others can, too.

 

[John61CT]

an app that would remind me to do things like check battery water

Check out ClearFocus, and Google Keep, if on Android.

We know you only accept golf cart batteries...lol.

Actually there are many dozens of FLA batt makes and models I'm happy to recommend, all true deep cycling, in may shapes sizes and voltages. It is true there aren't too many such made in 12V.

Dozens of AGMs too, and lots of LFP.

Those East Penn GCs just happen to be **by far** the cheapest, not only per AH but the cheapest way to get started

for someone actually in need of deep cycling on an ongoing basis.

If I ever hear of smaller/lighter thus lower-amp that meet that standard then I will start recommending them.

But I will bet real money they won't be cheaper, since there just isn't enough of a market for the magic of mass production and consumer channels to kick in.

http://www.pbase.com/mainecruising/deep_cycle_battery

 

[akrvbob]

My advice stands, when you are buying your first system, unless you are willing to do the learning about keeping your battery healthy, and then do the work it requires to monitor it, buy the cheapest battery you can and learn on it. Then spend the money on the second set of batteries.

A lot of that is the psychology of looking at two big batteries and thinking you can use all you want. You look at one battery and it seems obvious you need to be careful.

 

[GypsySpirit]

So, not to sound stupid, but how often does one need to water the batteries?

 

[John61CT]

You should **check** them very regularly at first, say weekly, then less often as you get familiar with what's needed for your particular setup.

Fill as needed of course.

Certainly no less than 4-6 weeks even if they rarely need topping up. I equalize monthly (manually) so usually do it then, but I've had setups that were very thirsty and watered almost every week.

 

[willprowse]

Check the charge rate of the battery. See how much solar the manufacturer recommends.

Check out this site for some ballpark numbers: http://www.mobile-solarpower.com/battery-banks.html

If weight is an issue, I would use a 35 amp hour agm sealed deep cycle battery. If you need more, just add another. They are cheap and tiny.

Sure you can use a 100 amp hour battery, and it is recommended, but if you plan to power a 12v slow cooker like the road master, you could pull it off with a 35 amp hour battery if the sun is out. And you would save a lot of money. The battery is the most expensive part of a system.

 

[John61CT]

I find it more productive to plan in 200AH units, and at $180 these are by far the cheapest component.

Horses for courses I guess.

 

[Weight]

It makes no difference as far as charging, with solar or any other method, of what the amp hour rating of the battery bank. We must return the energy used to the bank with a slight premium. Use the power available for charge with a 100 watt panel, from a 115 ah battery or a 460 ah battery. It is all the same. The rule of thumb if any is; Mount as much solar panel as you can fit. Have as much amp hour rated battery as you can afford. Use the energy you can replace. John is correct about the GC2 batteries. Bob's advice is also valid. The 12 volt battery linked way above is the type Bob was referencing. He picked walmart as they are everywhere for warranty.

 

[John61CT]

I do take issue with this "thumb".

Have as much amp hour rated battery as you can afford.

Many people "can afford" lots more than they actually need, and carrying 100's of extra dead lead pounds around is silly.

But most beginners grossly underestimate the bank size they need, and it is not optimal to add new batts to an old bank later.

It is true, without accurate information and knowledge money **will** be wasted, but I think with the GCs that wastage will be less.

The know-nothing owner murdering batts intentionally taking advantage of the warranty, is *not* part of my calculation, and I have to believe not a foolproof strategy.

 

[geogentry]

This brings up a question for me.  I see everyone talking about checking water and such on batteries here.  Why are AGM not recommended instead, or something similar?  AGM are sealed so no need to check/replace water, they are less likely to damage from road vibration, they dont release explosive gases into their environment, and they can be mounted in any orientation except upside down.  Is it just cost to suggest something different?

 

[John61CT]

They don't last as long and are much more easily damaged by suboptimal treatment.

And "only" cost?

Odyssey, Northstar and Lifeline are the only* true deep-cycle AGM I would recommend, and their cost per AH is just plain unaffordable for many (most?) here.

The higher CAR issue is marginal, so really that leaves only the mounting flexibility as IMO a strong reason *if* that is critical for a given setup.

Oh, and the ability to gauge SoC accurately with a cheap hydrometer is a huge plus for FLA.

 

[Weight]

Yes john. every thing can be taken to extreme. Battery banks as all systems should be sized to the expected loads. The high end of the estimate is better, in my experience. I would never use a marine battery for more than a few electronics and lights, maybe a small fan. Four GC2 batteries are required if I want/need the microwave. Add in my toaster, coffee pot, and lap top along with the rest? And then, I only have reasonable room for 400 watts of solar. So far there has been no problem charging 6 EGC2 wet batteries. BUT I am careful of my energy use. With very small voltage drop in the system. I don't have to return 340 plus amp hours. I only have to return what I use. I could get on well with 4 batteries, but was made a offer I could not refuse on 6.