Batteries for 120w panel?

[JadeOnWheels]

What size amp hour batteries should I get for this system, and how many? I see the cheaper 6-volt golf carts are only 35ah. Can I run 4 of them serially, or can I run two 100ahs serially? 

For those of you with 100-120 watts of power, what can you reasonably run? I need to be able to use my laptop for 4 hours a day. Is it better to use the battery, then plug it in and let it recharge the rest of the time? I have a cell phone and tablet too, and of course, I'll have a fan I'll be running for several hours. I'm going to use Luci Lights, but also will have LED string lights, although I won't use both at the same time.

 

[Almost There]

Do you already  have the 120W panel?

I ask because the usual way of figuring out things is to assess your power needs, then match the system to that. If you've already got the panel and it's the only one you're figuring on using for the long term you will have to limit what power you use to what you can produce.

Most people ascribe to a 2 watts of panel for each AH of battery so that the battery stands a fair chance of getting to 100% but that depends on where you're parked. In the PNW, I could have 4 times the solar wattage as battery and still not get them to full each day. In AZ in the summer time, the batteries would be full by 11 AM.

If you're using 6 V golf cart batteries, remember that you need to team each pair up to make a 12V battery. I use 4 235 AM batteries for a total of 470 AH. That sound like a lot but only 50% of the battery capacity can be used without risking the integrity and life of the battery.

What other charging methods are you planning on installing? Are you planning on being able to recharge the batteries from shore power on a regular basis.

 

[JadeOnWheels]

Do you already  have the 120W panel?

I ask because the usual way of figuring out things is to assess your power needs, then match the system to that. If you've already got the panel and it's the only one you're figuring on using for the long term you will have to limit what power you use to what you can produce.

Most people ascribe to a 2 watts of panel for each AH of battery so that the battery stands a fair chance of getting to 100% but that depends on where you're parked. In the PNW, I could have 4 times the solar wattage as battery and still not get them to full each day. In AZ in the summer time, the batteries would be full by 11 AM.

If you're using 6 V golf cart batteries, remember that you need to team each pair up to make a 12V battery. I use 4 235 AM batteries for a total of 470 AH. That sound like a lot but only 50% of the battery capacity can be used without risking the integrity and life of the battery.

What other charging methods are you planning on installing? Are you planning on being able to recharge the batteries from shore power on a regular basis.

Yes, I already have it. I have to do what my budget will allow, and I found a great deal on this one. I'd ideally like to have 200w, but no money for that. I'm also using an isolator, and will be mostly a city dweller, but still want to be able to boondock from time to time. I'm going to try to rig something up where I can recharge on shore power if necessary, without having to cut a hole in the side of the van. Have to study on that a bit more. 

I know I have to team up the batteries, which is why I want two, but like I said, I'm on a budget, so can't get the really expensive ones. I just don't know if I should waste my money on two 100ah batteries if I can't charge them. I know they'll charge when I'm driving, or if I use shore power, but on a daily basis, not with my panel they won't.

 

[lenny flank]

To answer your question, then:

My setup consists of a 100w panel and a 105ah battery. With that, I charge my laptop, charge my camera batteries, charge my electric razor, and charge the AA batteries for my hockey-puck interior lights. That's all I use.

I find 100w to be plenty of power during the summer. In the winter, when the sun is less intense and the days are shorter, it BARELY serves, and I charge the laptop in a mall or library whenever I can to save on the battery.

If you are not running something else (such as, for example, perhaps a refrigerator which you need for medical reasons.....) then this will do the job for you.

If you are running other things, it will not.

(As for me, I bought the 100w system almost three years ago. Today, I could get a 200w system for essentially the same price, and a 300w for not much more.)

 

[John61CT]

Do you need a fridge or not?

Huge difference.

Give a list of your loads, hours per day.

Sam's Club Duracell flooded GC 6V in pairs, best possible value.

 

[lenny flank]

Do you need a fridge or not?

Huge difference.

"Electricity" is something that is taken so much for granted. Most people have no idea how much power they actually use up each day in an apartment, and when they think about RVing or van-dwelling they assume they can have all that stuff again with just a solar panel on the roof.

:idea:

 

[frater secessus]

For those of you with 100-120 watts of power, what can you reasonably run?

I've been collecting reports of various sized solar installs by wattage for just such an occasion.

 

[lenny flank]

I've been collecting reports of various sized solar installs by wattage for just such an occasion.

Back in my longer days, while kayak-camping, I used to charge up my little ASUS Netbook with a 45w foldable solar panel. Does that count?



PS--it took forever.

 

[John61CT]

I remember when access to the Internet even over a 4800bps modem required rare skills, hacking winsock anyone?

Few years from now maybe off-grid energy will also be a no-brainer.

 

[jonsun]

I used to run my calculator on solar

 

[jonyjoe303]

120 watt panel laying flat on the roof will get you about 6 amps of charging power when the sun is overhead, on a good day it might give you 30/35 amps back into your battery. 
A large laptop can use up to 6 amps of power, a small netbook maybe 2 amps. 

You can charge a 100ah battery easily or even larger but it will take several days. But many times when I had my 120 watt panel, I produce more power than I use, and I only had a 75 ah agm, I was wasting potential power. Even though a big battery won't charge in one day, once it's topped off all the extra amp hours will come in handy when you have cloudy weather. Just get the bigger battery since you got multiple ways you plan on charging, solar can be what tops it off.

My recommendation is keep the float voltage high (same as bulk voltage) all the time, You going to run out of sunlight before the battery fully charges. I remember when I went to the battery place to buy an agm and told the guy there how I was going to charge it, he told me 6 amps was trickle charging for an agm. The agm's like higher amps. But you use what you got.

 

[John61CT]

120 watt panel laying flat on the roof will get you about 6 amps of charging power when the sun is overhead, on a good day it might give you 30/35 amps back into your battery. 
A large laptop can use up to 6 amps of power, a small netbook maybe 2 amps. 

Minor point, but those last three "amps" are actually amp hours AH.

 

[DLTooley]

I am in the process of upgrading my 50 watt system. I am attempting to run a refrigerator off of solar alone, running only when there is excess power. I am discovering that the controller has a lot to due with how much power you have available.

I've just ordered a bayite meter that tracks amps and will likely soon get the Victron 75/15 mppt controller.

The two gc2 batteries is currently the best way to go. I am still using a wal mart marine. One advantage of this alternative is the one year guarantee which I utilized after the learning experience of killing a battery.

 

[JadeOnWheels]

Do you need a fridge or not?

Huge difference.

Give a list of your loads,  hours per day.

Sam's Club Duracell flooded GC 6V in pairs,  best possible value.

I don't need a fridge. I eat mostly raw food, and can live for days on that without even cooking. I also dehydrate a lot of food for storage, so I have to look into a solar dehydrator. I don't eat dairy or eggs, so I have no need for a fridge. I drink all my beverages at room temperature. I can work my diet around foods that don't need refrigeration when necessary. Other than that, I'll use a cooler for things that need it, like carrots, celery, etc. Looking for a decent one now, or may DIY a cool box for the one I have.

I will eventually get more solar when I can afford it so I can have a small dometic, but can't afford either right now. Van dwelling is so I can save money and not work so hard.

 

[JadeOnWheels]

To answer your question, then:

My setup consists of a 100w panel and a 105ah battery. With that, I charge my laptop, charge my camera batteries, charge my electric razor, and charge the AA batteries for my hockey-puck interior lights. That's all I use.

I find 100w to be plenty of power during the summer. In the winter, when the sun is less intense and the days are shorter, it BARELY serves, and I charge the laptop in a mall or library whenever I can to save on the battery.

If you are not running something else (such as, for example, perhaps a refrigerator which you need for medical reasons.....) then this will do the job for you.

If you are running other things, it will not.

(As for me, I bought the 100w system almost three years ago. Today, I could get a 200w system for essentially the same price, and a 300w for not much more.)

That's very helpful. Thank you. That's what I needed to know about the laptop, since I do still work (online) and need to use my laptop for that. Since I will mostly be city dwelling, I can do most of my work on those days, to earn enough to support my boondocking. I'm also looking at a separate dc battery charger for the laptop. I'll see where my budget stands then. I have to start with bare essentials for now, which is why I need to city dwell so I can work and get free wifi.

 

[JadeOnWheels]

"Electricity" is something that is taken so much for granted. Most people have no idea how much power they actually use up each day in an apartment, and when they think about RVing or van-dwelling they assume they can have all that stuff again with just a solar panel on the roof.

:idea:

That's why I'm trying to learn. I have no such illusions, I just want to know if I can use my laptop, because right now, that is my only means of entertainment. I also have a tablet, which will draw much less power, that I can use for that if necessary. I'd rather not have to watch movies on an 8" screen, but if I must, I must. Life doesn't always give us what we want. If I can't use either on 120w, I'll just have to read more.

 

[JadeOnWheels]

I've been collecting reports of various sized solar installs by wattage for just such an occasion.

Thank you! that is so helpful!

 

[JadeOnWheels]

120 watt panel laying flat on the roof will get you about 6 amps of charging power when the sun is overhead, on a good day it might give you 30/35 amps back into your battery. 
A large laptop can use up to 6 amps of power, a small netbook maybe 2 amps. 

You can charge a 100ah battery easily or even larger but it will take several days. But many times when I had my 120 watt panel, I produce more power than I use, and I only had a 75 ah agm, I was wasting potential power. Even though a big battery won't charge in one day, once it's topped off all the extra amp hours will come in handy when you have cloudy weather. Just get the bigger battery since you got multiple ways you plan on charging, solar can be what tops it off.

My recommendation is keep the float voltage high (same as bulk voltage) all the time, You going to run out of sunlight before the battery fully charges. I remember when I went to the battery place to buy an agm and told the guy there how I was going to charge it, he told me 6 amps was trickle charging for an agm. The agm's like higher amps. But you use what you got.

Thanks. I can't afford AGMs right now, so I'm going with regular golf carts, and finding a way to vent them.

 

[John61CT]

Best value for batts by far is (in pairs) 6V GC, specifically the Duracell (Deka) flooded from Sam's Club or Batteries+.

200+AH for $180 or so.

If you do a lot of driving and want/need Alt charging of your House bank, there are different options, check in here first.

But only if you do a lot of driving.

Get a little lithium jumpstarter at some point in case you run your Starter batt down while boondocking.

 

[John61CT]

Once you have a car adapter for your laptop, best to run it straight off the House batt, keep its own batt relatively full. While solar is charging the laptop won't even pull the House down much.