Need advice on what battery to use with Solar

[dodecagon2000]

i am installing 4 15watt panels on the roof of my custom camper and i was wondering what i should use for a battery? should i use a diehard platnum or a battery like this
http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200344115_200344115

what should i do? i am stumped and i have no expericance witht these things. i will be running my fridge of this battery at camp and maybe the LED lights and a laptop and two 1.4amp fans at the most. What do you guys think...any help would be great.

thanks

 

[FAW3]

The battery shown is rated 110 amps at 12 volts. (corrected post of this first paragraph...I don't know what happened on my first read...somehow I read the voltage was 6 volts? I apologize for my misread....the link is clearly a 12 volt battery) Anyway, now that I am awake...)

But let's back up just a bit...here are some general questions you should answer before you buy:

What battery size/weight/ventilation/vibration considerations do you have? These factors will guide you toward lead/acid, AGM and gell types.

What controller do you have...does it support proper charging of the TYPE of battery you are considering...this is critical for best battery life. Some offer selectable outputs for the various types. Charger should match battery in this regard. The controller spec sheet should mention these data points.

Are you starting something, or is this for a house battery...I would think your planned use would best be served by actual deep cycle type unit(s).

What are your estimated "draws"...as you typically use the battery(s)...how many amps per hour for how many hours? Does your battery selection meet your needs with a good reserve?

Anyway, I am sure you will get additional good support here, so keep asking good questions! Better to get some info from the web and some practical users before the $$$ hits the counter.

 

[dodecagon2000]

The battery will only be used for small LED interior lights, a laptop and running an Engel 45qt refrigerator. I would say that the fridge would be running for about 12hrs a day and i can remember what the draw is on the fridge. I would say for a quick calc on a battery size i could forget the interior light and the laptop because the interior lights are almost irrelevant because of there size and that they are led's and i hardly ever use the laptop. SO for space and ventilation i will be mounting it under my bed platform in the camper and the ventilation is not bad but not ideal. So i am kind of lost on battery manufacturers and sizes and what charge controller to use. Any ideas? maybe some one could shed light on there system components and what the run on there system. Also this battery will not ever start the vehicle...its not what it is inteded for. for what ever its worth.

 

[FAW3]

Ok, please check the previous post...I corrected it as to the battery info...I must have been near zombie mode when I hit/read the link cause I swear I thought it said 6 volts.

Your power demands: I checked the Engle site, it appears the unit draws 2.5 amps per hour. For a full day the power demand would be 2.5 x 24 (hours), or 60 amps, assuming the unit ran all the time, they typically cycle on/off to regulate temps, but this is worst case and provides a reserve.

Running a 1.5 amp fan, say from 10pm to 6am (8hours); would draw 12 amps.

Lighting, let's just say 2 amps for 5 hours; 10 amps. Total current demands are 82 amps over 24 hours (worst case), you might get by with a bit less...but for planning, it is better to figure worst case, cause we all lie about how much juice we use.

Power supply: 4 15 watt solar panels...output (in the ideal world) would be 60 watts (amp output is watts divided by 12 volts=5 amps)...your actual output will be about half that typically at best (clouds, sun at angle, heat loss). This is about 5 amps/hr.(ideal). So lets say a good day gives you 8 hours of sun, figure 3 amps/hr averaged output (real life)= 24 amps back into battery in a good day.

You put 24 amps back in to the battery on a good day...so, without a external source of additional charging power, your running a deficit of 58 amps over 24 hours....you need to bridge this deficit with more input amps (higher rated solar panel(s), alternator charging from vehicle or a generator/charger), or of course, less amp demands.

The system you initially mentioned with one of these batteries would get you thru the first night out, figuring it was charging off the alternator as you drove...OK, but your battery would be down in the AM and absent supplemental charging, by day two, your out of juice.

Play with your "energy budget", and figure your amp needs over 24 hours...figure your solar output in real world numbers, of any other available charging input systems, and think of your battery as a glass of amps you never want to draw down more than 40%...and you'll be on your way.

 

[telwyn]

power consumption spreadsheet

First, I am by no means an expert on this, however, I did post a power consumption spreadsheet that a buddy of mine made for me when I was going through a similar exercise for my trailer build.

Check out post # 2 in this ExPo thread to access it:

http://www.expeditionportal.com/forum/showthread.php?t=28712

Hope this is helpful.

 

[Martyn]

From our in house calculations using the high efficiency Powerfilm 60 Watt foldable solar panels produce enough power to run an Engel 45 fridge for 24 hours.

The panel puts out 3.4 amps per hour in full and partial sun light light. We calculate for 8 hours of full sun plus shoulder hours in the morning and afternoon. (Fridge: 1.2amps x 24hrs = 28 amps, Panel 3.4amps x 8hrs = 27.2 amps + morning and afternoon sun)

If you run anything else you will be drawing from your battery.

It's important to calculate the actual power output rather than the nominal i.e. a 60 W panel at 100% efficiency would but out 5 amps but none of them work at 100%, and some are very inefficient in anything but full sun.

The other thing that is frequently over looked is accessories like fridges run 24 hours a day and the sun does not.

 

[dodecagon2000]

so it sound like i should consider uping my solar wattage to compensate for the fridge consumtion. It sounds like you guy like the power film products...any suggestions on any other solar panels? I doont really care if they are rigid or flexable.

 

[VicHanson]

You need a deep cycle battery for continual use, AGMs are good but are more expensive than regular wet cell deep cycle ones. I am looking at Trojan T-105RE batteries, they are specially designed for solar or wind recharging. They are 6v and 225AH, so you need two of them in series for a 12v system. They are about $140 each. They also weigh 67 lb each so if you can find them locally and save on shipping, that would be good. Trojan is one of the highest recommended deep cell battery makers. A so called marine battery is not a true deep cycle battery, and will not last as long.

It is not recommended to discharge more than 50% so you need to keep that in mind as well.

Sun Electronics in Miami and Phoenix have some great prices on solar panels, as well as the charge controllers http://sunelec.com/ Morningstar make some good controllers.

I have done a lot of research into solar systems and it seems that there is a lot of misinformation out there, as well as installers that don't know what they are doing. Use short, big wire, make sure there are NO shadows on your panels, and charge your batteries fully according to the battery manufactures specs.

Here is one guy that seems to know what he is talking about
http://handybobsolar.wordpress.com/2009/07/22/solar-power-that-works/

Your system is probably smaller than what he is talking about but his blog will give you some good ideas.

Vic