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old greybeard
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# Posted: 27 Dec 2013 07:54
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What type of protection do you use when you parallel batteries? If one shorts out a cell the current flow from the other battery could burn up you cables, do you use fuses or fuseable links?
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Dillio187
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# Posted: 27 Dec 2013 09:54 - Edited by: Dillio187
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Quoting: old greybeard What type of protection do you use when you parallel batteries? If one shorts out a cell the current flow from the other battery could burn up you cables, do you use fuses or fuseable links?
if you must use parallel banks, fuse them. I figure out my max load out of the entire bank, and use a fuse with about 10% headroom. I use these fuse blocks from Blue Sea Blue Sea fuse block
I am not a fan of using parallel banks though, because even if you take all the necessary precautions, you will still have issues with charging and discharging the parallel batteries evenly. As Don mentioned, even the smallest of differences in the resistance of the path will have one battery or the other providing more of the current than the other.
I bring up purchasing all the batteries at once, because I myself have had issues with it twice now from two different stores (Fleet Farm and Sam's Club). I purchased 2 golf cart batteries and set them up in a series for 12V, and tied them into copper bus bars. 3 months later, I bought 2 more batteries, cut identical length cables, and also tied them into the bus bar for a 440ah, 12V bank. Over the course of the next 6 months, 1 set of batteries needed water every 3 weeks, while the other set of batteries only took water every 2 months. This told me the parallel strings were not charging and discharging evenly, and I was slowly killing 1 set of batteries.
I also tried removing the bus bars and wiring the batteries as shown in the 2nd diagram Wiring Diagram
That was worse. It was really apparent to me that I had batteries with different internal resistances that would not work well in a parallel setup.
So what did I do? I bought a 24V inverter and series wired all the batteries together. Now they all take water at the same time and have been happy for over 2 years now.
I know there are people out there with many parallel banks that have not had issues, but many of them probably rotate batteries in and out for equalizing etc, and I wanted a more maintenance free system. All I can do is share my experiences with setting up some off-grid solar systems.
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Truecabin
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# Posted: 27 Dec 2013 12:12
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i started with 2 panels and 2 batteries Now i have 3 panels and 4 batteries and 310 watts i dont expect to add any more
cant find a link to that 280w system but the 280 is ok for me
my batteries cost 150 each and the panels cost a lot more back then
i think i could get by on 2 batteries but i went by the 10% rule and spent $300 extra on batteries
its ok i guess but easy to charge with the generator if its cloudy for a stretch
i dont know about mppt tracking its a lot of $$ for few % maybe mppt is cheaper now
maybe its better to buy more panels and aim some for morning and others for afternoon sun
just make sure the charge controller is big enough for adding panels later then no problem a bigger cc is not expensive
theres better ways to do everything but what ever you do its satisfying to get your own power from sun and even better if you didnt break the bank
if you get it mostly right you cant go wrong
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GomerPile
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# Posted: 27 Dec 2013 13:11
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It can be more than a few percent....think 10 or 20. They say 30% but I think that a bit optimistic.
The other thing that can be important so I will bring it up. If your panels are located any distance from your batteries wire losses become a big issue. You can spend money on bigger wire OR you can wire your panels in series and use an MPPT charge controller. Many of them will take 150VDC or more. In a 3x100W array (300w) thats 6.5 amps running thru your cable vs 20ish. You need to factor in the cable savings in the cost of the charge controller.
Quoting: Truecabin i dont know about mppt tracking its a lot of $$ for few % maybe mppt is cheaper now maybe its better to buy more panels and aim some for morning and others for afternoon sun
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Truecabin
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# Posted: 28 Dec 2013 00:09 - Edited by: Truecabin
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very good info dillio and gomer
i use 12v because it was so easy to use automotive and RV stuff
and 12v lights are easy and low power
also easy the charge with a generator
12v has its benefits but wire size is not one of them
24,48v have benefits but it gets more complicated and expensive and if lights are most of what you need 12v is good for LEDs
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Dillio187
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# Posted: 28 Dec 2013 10:29 - Edited by: Dillio187
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I run a 12V system in my cabin with 2 golf cart batteries, and a 24V system here at home.
I'm in agreement that I like 12V in my cabin. I can jump start my truck or ATV from it, and it has a lot of other uses. When the golf cart batteries fail I will likely get some real solar batteries and it will stay 12V, but be in the neighborhood of 370ah with 2 batteries in series. The Morningstar 300W 12V inverter is one of the best out there, it has a very low idle draw and is very efficient. The remote on/off switch is a neat touch as well.
All I run in the cabin is lights, my radio gear, computer and phone chargers, small drills and a small dust buster. If I want to run the shop vac, air conditioner, or saws, I start my Honda generator. We have no fridge, we usually use a cooler with ice in the summer, and the porch in the winter :D
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creeky
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# Posted: 28 Dec 2013 16:20 - Edited by: creeky
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I must say this topic has had great moments of hilarity.
Clearly there are many ways to the one.
rmak you are on the right track with a 280 solar system and a small generator. that will give you lights. charge phones etc.
Your 280 watt solar system needs 280 to 400 amp hrs at 12v of battery. there is reliable data that points out cheap deep cycle batteries are pretty much just as good as expensive ones. so start cheap!
pwm solar chargers require your entire system to be the same voltage. Panels, charger, batteries. Some folks (like me) use higher voltage panels with lower voltage battery packs. Hence, I recommend mppt. MPPT has two advantages. 1) they convert higher voltage panels to lower voltage battery banks. 2) they extract more power from your panels. they also grow with your system better ... but
Let your generator run the battery charger attached directly to the battery bank. The charger will have a fuse. I like the PowerMax chargers. There is a "boondocker" model. The IOTA is probably top of the class for small system chargers but it is a bit pricier.
Of course, your benefits from solar are that your batteries stay charged even if you're away for a long time (months). when you are at the cabin you have renewable power. you don't have to haul gas. fill gas. burn gas. repeat. And it's cool living with no bills and no noise.
Still. If you are off grid there will be times when that charger / generator combo will be essential.
and after all that. the northern wind-sun site has a beginners corner ...
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rmak
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# Posted: 28 Dec 2013 16:49
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Thanks, Creeky, for the right on advice. I appreciate all the folks who took the time to help me. A lot of the technical stuff was too advanced for me.
Any source for cheap deep cell batteries?
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creeky
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# Posted: 28 Dec 2013 17:10
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i hear the "club" stores are good but i went to an "only" battery / industrial battery store in my area for the best price ...
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Dillio187
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# Posted: 28 Dec 2013 17:25
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Sam's Club sells golf cart batteries, or most any Fleet Farm style store will as well.
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spoofer
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# Posted: 29 Dec 2013 14:30
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I always use walmarts biggest deep cell marine for my "el-cheapo" system. they seem to last about 7-8 years.
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toofewweekends
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# Posted: 29 Dec 2013 21:53
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rmak,
We have a similar sized place in Alaska, used a couple of weekends a month, with a couple of week-long stays. We've run 4 years on a 100w panel, 2 6v Costco batteries and a 350w inverter. That takes care of lights, music, and dvd movies. We back it up with a Honda 2kw. Also, we use a battery charger to top things off in the winter when solar in Alaska just can't keep up in an economical way. And, when we microwave, charge or run tools, etc., the Honda gets used. It's been a fine "system" and we learned what we wanted for a small investment. As retirement nears, and the batteries age, I will upgrade with another panel and controller to handle it, replace the 2 batteries with 4, and bump up to a larger inverter. Then I can make toast w/o firing up the generator in the morning! But for now, this does fine and requires very little maintenance or thinking.
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rmak
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# Posted: 30 Dec 2013 11:30
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Thanks toofewweekends (great handle, by the way)
That's good proven advice. I'm still curious as to how you folks use your generators. Do you keep them outside, as in a small covered box or small shed? I don't know if I want to store something with gasoline in the cabin because of fumes and the fact I have a wood burner. I'm sure when the generator is outside it needs to be in the open for exhaust. But on a day like today when the snow's coming down heavy (get any of that in Alaska?) I wouldn't want to leave a $1000 generator sitting and getting wet.
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Dillio187
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# Posted: 30 Dec 2013 11:55
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I'm building a 4 sided, insulated box for mine. The open end will face away from the cabin for air flow and exhaust purposes.
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skootamattaschmidty
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# Posted: 30 Dec 2013 14:26
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My generator is stored in a small shed when I'm not at the cottage. On one side of the shed I ran the steel roof down to almost ground level following the same slope as the roof. When I use the generator I roll it out of the shed and to the side under this extended overhang. Under here it stays dry and is covered from snow and rain. The front and back of the overhang is open to allow ventilation. I have a 3000 wat Honda mounted on a piece of plywood with pneumatic tires so it rolls in and out easily.
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toofewweekends
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# Posted: 31 Dec 2013 00:34
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When we leave, we put the generator inside the cabin and have had no fume problems. When we're there, we put it outside ready to use. If there's likely to be snow, and I remember, I'll throw a tarp over it overnight (not when it's running, duh). The Honda seems pretty impervious to the elements, though. Still, a noise-insulated sort of dog house box for it is on the to-do list.
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Skiguy
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# Posted: 2 Nov 2014 07:29
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Its been fun reading this tread and discussions. I set-up a small solar system recently. Two 100 watt solar panels, with a 30 amp charge controller and two 6 volt deep cycle batteries with a 2000 volt inverter. The total cost is less then $1000 bucks. Like most people my cabin is used on weekends and a few extented stays on vacations. I also have a generator which is used to run power tools and could be used to charge the battery bank if needed for extented stays. The cost of a solar panels system and kit have come down in price where its more affordable to get started. Shop around on eBay. I found this website very useful on battery calulations but you dont have to buy the Trojan brand. http://www.batterysizingcalculator.com/
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creeky
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# Posted: 2 Nov 2014 14:10
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I will add a point to skiguy.
watch out on "lifespan" and charging specs.... If you have top of the line lead acid batteries you can get away with stuff that will kill basic deep cycle.
mtndon shows a chart on page one of this thread that are not applicable for GC2 (good deep cycle) batteries.
Rolls are top of the line. Trojan is pretty good. Crown are very good. Best for full time systems. imho.*
then you have good gc2s. brand name less expensive batteries available for golf carts etc (hence, gc). Probably the best bet for reliable lower cost solar storage over 2 or 3 seasons.
then you have marine/starter deep cycle. Best for intro systems and weekend use ...
But don't expect lower cost batteries to perform/last/charge the same way. Nor take the advice of a top tier lead acid battery and apply it to your second or third tier battery.
* I'll add that new lfp lifep04 batteries are probably best for off grid full time users now.
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Steve_S
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# Posted: 3 Nov 2014 22:22
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Here's a Generator Tip:
As many varieties of generators in use are Gas based I came across this up for my Champion 7200 this but the little inverter can't be done. Tri-Fuel Conversion Kits which allow Gas, Propane, Natural Gas.
Best part for propane, it's not going to sour on you. For winter time, keep a bit of fresh gas handy for cold starting to get it going then switch to LP when warmed up. Recharge the Batteries & warm up all at once ;)
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