Battery Bank System

thank you for this info. hiebtser

thanks, I talked to the magnum tech rep and he walked me through the set up and was very helpfull. American made to boot.....Lot of this stuff is new to me but it's interesting and I have learned alot. Thanks again for you help...

lee; elnav is right look at home power magazine, there at your bigger stores or theatibrary perry

Truely its not the size of the bank it is your average power draw that determines the wattage range for your array...Power tools do eat alot of amps but you are probably only running them intermittently ...I personally just use a genny when running any high draw stuff and use my panels for keeping the lights and a low draw computer..what you should do is add up all the rated power draws for equitment in your cabin, then figure out how long each of them runs in a day...multiply the two and that give you how many kilowatt hours your eating per day...with that I would get a sizeable enough array to give you alittle cushion. If your generator is remote startable, consider getting an auto transfer switch. It determines if the load will be a bit high for the inverter/battery bank and cuts on the generator to handle it.

My inverter, an old trace 4024, is my best friend. It has generator auto switching build in and programmable! I have it programmed to turn on the genny when load is more than 15 amps, and when the battery bank hits 50%. With that I can get away with the modest array i have, and only hear a generator but for an hour here ad there

Calculating the size of a solar panel and the associated battery bank is a complex task. Because the number of solar hours per day is typically only about 1/3 of the total 24 hour period you need to replace the total 24 hour consumption during that sunny period. On the other hand the battery bank should have enough reserve to provide for an extra day if the weather is cloudy. Some experts recommend two extra days reserve. Good advice but given present cost of batteries and the fact such costs will likely escalate, this may become too expensive. But you must have at least enough capacity in the battery to run the full 24 hour period and not discharge below the safe limit.

On the other hand it may not be affordable to install a solar panel large enough to deliver the full power consumption rate needed at peak demand. Grid-tie installations are predicated on this principle. The idea being you sell back excess power during peak production periods and buy back during peak demand periods. In effect the grid serves as a storage medium. In locations where the power company pays a reasonable rate and the installation cost may have some sort of tax benefit or an actual grant, this is feasible but many locations do not have that. Nor do totally OFF-Grid installations work thqat way. New building has the advantage of being able to amortize the solar sysem cost as part of the total house mortgage, but a retrofit to an older home may not qualify for such funding. you pay the entire cost up front. Either way most solar panels cannot deliver a charge current strong enough to completely reverse sulfation. For that you need to have a periodic fast charge from a generator. Otherwise you will be replacing the batteries in a lot less than every ten years.

Generators: Those that are big enough ( typically 10kW or bigger) to be fitted with an auto start panel are normally too large for the available charger capcity. If you have a 300 - 400 amp hour battery bank then you can only use a 100 amp to 150 amp capacity charger at the most. Any more will usually cause battery damage. Depending on Battery system voltage, your charger will only demand something in the range of 2kw to 6kW at the most. The back up generator should be sized to match the charger so it runs at about 80% loading.

It makes no sense having a 10+kW generator driving a 2kW charger. not only that but it will lead to engine service problems.

Having dealt with many off grid systems I absolutely love honda's 3000i(or any of their i seires). they can have an external autotransfer switch added ..it just piggys off the inverter output and wait for the load to jump to a set point .so there is no need for an industrial gen set with the auto transfer built in.

Are the Honda 30001 the model that has an inverter internally and can be synchronized with a cable joining the two generators?

If not, some of the big inverters will overload the 3000 watt genset.

Gas versus diesel. Hmmm! This is a bit problematic. Long term usage with welders show that a typical gas engined welder will run about 3000 hours before needing an overhaul, The same capacity welder with a diesel runs 10,000 hours before an overhaul.

Unless you plan on running for many hours on end, and acumulating much moer than 3000 hours the greater cost of a diese genset may not be justified. Secondly if this is a back up genset which will see the most use in winter time, gasoline may prove easier to start at very cold temps.

I can personally wouch for how nasty it gets trying to start a smal d iesel at -20 below . In fact most of the newest consumer propane blow torches do not deliver enough heat to really warm up a 6kW size genset motor block. Even after ten minutes you can stil lplace your bare hands on the cylinder head. And if your batteries are already delpleted, you may not have enough power for electric glow plug heating.

My twenty year old Bernz propane torch seems to deliver twice the heat output as the new models sold in the consumer stores. At least judging by how fast it heats and how quick it uses a bottle. A cold starting diesel will also smoke more until warm than a gasoline generator.

Propane or natural gas fuelled gensets are very nice. But propane has a problem with really cold starts lower than -30 C The vaporization point of propane is around -34. colder than that and it simply won't volatize and burn. Ask any propane fuelled vehicle driver. Now you need electric fuel heaters etc.

Best bet is gasoline.

Don't let the diesel get cold, park it on a heated slab within an insulated envelope and be prepared.

Thanks for that reference. Even a quick Google search produced many good hits.

One sentence caught my attention.

"This engine ran quietly and promised good durability but.... falling world oil prices and vanishing interest in alternative energy within the US Govt. scheme of things, scratched funding for further work". This from a recent letter from Mr. Lockwood. The incalculable harm done by the lobbying efforts of the entrenched oil industry will go down in the history books as being among the biggest man made disasters for our civilization.

With a small 1- 3 kW genset running pretty much 24/7 you can generate and store enough energy to maintain a western style household as far as the electrical energy consumption goes. And it doesn't have to be a large battery bank when the genreator runs continuously. The bank only has to be large enough to support starting surge loads of inductive motors and short term peak demand loads for maybe half an hour at a time.

I use a converted a semi cab sleeper that works great for my gen set bldg. It's insulated and the first cold snap I put a propane heater in the sleeper and ran it for only 30 minutes and the diesel started right away. If I had it to do over I would of put it on a slab and ran some pvc pipe from my cabin slab heat system.. It is'nt that inconvenient to heat up the small area with propane but the slab heat is very nice and efficient. Thanks

Please reply with more info regarding the honda gen set... Hiebster

I like the Home Power magazine - they have a really good section on PV panels - you can read some of the primer articles on line as well - http://www.homepower.com/home/. Good luck!

in responce to the 3000i question . I do not think they can be stacked like the 2000i's. In terms of overloading gens, inverter charger units i come into contact with (xantrex, trace, frontius, sma) can be programed to limit its the current draw from an ac source. I usually put that limit to 60% of the rated operating current of the genset(around its rated peak efficiency sweet spot.)

I am familiar with the current limiting feature but that isn't the point. Every so often you need to hit a battery with a large enough charge current to flush out the residual lead sulfate. The charge current should be about 25% of the total Amp hour capacity. On a 800 Amp hour bank this means a charge current of 200 amps. How many solar panels installations can deliver so much current?

A Trace or Xantrex inverter charger can usually only use half as much wattage for charging as it can deliver inverting. So a 4000 watt inverter will use 2000 plus 15% or roughly 2300 watts. But that is not enough current to properly recharge a fully depleted 800 amp hour bank at a C/4 rate. In round numbers you would need a 5 kW generator to deliver the right charge.

And when you use a limited charge current the charging takes so much extra time. Worst case is when the charging takes 8 - 10 hours. Getting back to the original thread purpose. If you have a 4000 watt inverter that can only absorb at most 3000 watts while charging and the genset is a 12kW or worse a 15kW; then th egenset is only loaded lightly. Under extremely cold conditions, the engine block may never warm up properly. My suggestion was that it would be better to have a smaller genset that could be fully loaded to its optimum point. I'm more used to diesels and their sweet spot is around 80% but maybe you are right that gasoline gensets have a sweet spot at 60%. Either way both instances is way more than the 20% - 25% a Trace 4024 loads down a big Onan of 12kW - 15kW capacity.

My question about the paralleling was because I just finished a system design that used a Honda 2000 and that model does have the parallel cable feature. But I am not familiar with the 30001 series.

A friend of mine is working at a system that uses solar panels to drive water pumps. He told me that he was able to find solar panels that operate as 12VDC output with a mean full power of 200W, with something like 1/2 sq. meter area. They're GE made. I'm pretty sure you're gonna find over the web several different panel specifications, as he told me that's what they have chosen among the options.

A combination of panels will give you the desired voltage and power. However, I'm affraid it's not gonna be too cheap to install, you're gonna need some pairs.

The arrangement you mentioned suggests that you have a total of 680Ah@24VDC assuming 12V batts. To find out really how much power you need in solar panels, how long do you expect your batteries to be charged by sun? If you'd like to have the same power of the generator, you'd need roughly more than 30 solar panels of such type...

thanks for the info. I would like to use a dc pump for water from my well. It is only 14 feet deep. I have a 18 inch culvert with the 1/2 horse 10 gallons per minute submersible pump. I always have at least 6 feet of water in the culvert. the well is 25 feet from my cabin. I have a 44 gallon psi tank that kicks in at 30#s and off at 50#s. The pump uses alot of surge power and the dc pump would be great. I use a 24 pump for my in floor closed heat system and that works great. It sounds like I will always have to have a generator to help charge the batteries even if I use solar panels. I'm very happy with the magnun 2440 inverter charger system. I have the option for a gen start module but start it manually for now. The gen set I bought is a chinnese special that looks great but I dont have the world of confidence in it. Alway listening for strange noises and pray it keeps running. All this stuff is new to me but very interesting. Helps to eliminate the trial and error stuff with good info from people like yourself. thanks again... Lee

Ah ha! Now I know what you want. We provide cattle watering stations which run from a small solar panel driving a Shureflo submersible pump. These pumps can lift as high as a couple of hundred feet but do not develop much pressure since they dump into a drinking trough. BUT. . . they are great for low voltage limited current flow and driven directly from a solar panel without needing a battery. . The beauty of these is the absence of a battery which requires maintenance. A cattle watering well placed miles away out on the range doesn't get much attention.

You might need to have a seperate pressure pump fed from a storage tank. We also use the Shureflow DC presure pump. Given your very shallow well the submersible 24V pump may be able to generate enough pressure to operate your system. Even so I recommend a cistern or storage tank inside your cabin for a reserve when its dark and the solar panel pump will not run. This second pump could be either 24V direct or a small 120V AC pump. Trouble is these use more power than the direct dirve 24V DC pumps because they typically develop more pressure.

Hello elnav,

You might need to have a separate pressure pump fed from a storage tank. We also use the Shureflow DC pressure pump. Given your very shallow well the submersible 24V pump may be able to generate enough pressure to operate your system. Even so I recommend a cistern or storage tank inside your cabin for a reserve when its dark and the solar panel pump will not run. This second pump could be either 24V direct or a small 120V AC pump. Trouble is these use more power than the direct drive 24V DC pumps because they typically develop more pressure.

All true but a ram pump will do the same without electricity.

http://science.howstuffworks.com/question318.htm

http://en.wikipedia.org/wiki/Hydraulic_ram

bwire: a RAM pump relies on moving water and a large quantity relative to the pumped amount. In the case being discussed we are talking about a well not a stream. If yo uhave yo pump water up from a well, yo umay as well stoer it rather thna use a large amount of it to pump ans pressurize a small quantity. Ram pumps are genrally used for irigation water or systmes with open water conduits no ta closed pressurized system as is being comtemplated here. Lee is also located in an area with below freezing temps during the winter. This also precludes using running water unless the stream is large enough to prevent freezing. My mention of a cistern or storage tank was intended for a relatively smal ltank that could fit into the building envelope so as to remain heated above freezing during winter.

Would it be smart to remove my existing ac submersible pump and put a sureflow 24volt in my heated cabin. Would this pump enough water from the 14 foot well to pressurize the 44 gallon tank with a psi switch set at 30 start and 50 stop. I have a pitless adapter set in the culvert with the 1 inch line running to the cabin below the frost line. the culvert is 25 feet from the cabin. Like I said I use a 24 volt pump to circulated water glycol in my closed in floor heat system and it works great. I heard I could use a capacitor inline to my existing submersible pump to lower the startup amps when the pump starts to help lower my draw on my bank?? I thought about getting a larger tank and just pump water from the well with a dc pump of some sort and use a cheap RV dc pump to keep psi water for my cabin needs???? My inverter/charger is working great but I'm trying to fine tune the other components.... thanks

It depends on how much energy you actually use. It also depends on how far fropm pump to solar PV panels. In a cattle watering station we place the PV right at the well head. But if you are thinking of running the well pump from th eexisiting PV and they are mounted some distance from the pump it is not a good idea. Do you really need to maintain pressure in your system at all times? If so why? You mention "cheap RV DC pump. Why do you consider it "cheap"?

You ask a number of valid questions but I get the impression your system has evolved rather than being plannd and designed.

The RV type pump only runs when you actually need water but an AC pump typically uses a pressure tank and if you have a pressure leak the AC pumps cycles. Using an AC pump involves a conversion loss in the inverter of around 10%. If the intention is to power the cabin entirely by solar panels then you have to start thinking about every watt you consume. your PV capacity is finite and yo uhave to make every erg count.

It is true that most RV pumps flow a lesser volume of water compared to an AC pump. However you may also have noticed that one of the energy saver methods often promoted is a flow restrictor in the shower head and faucet outlets. So s the lesser flow typical of a DC pump really an isue? The principal reason for going AC 120V in an off grid situation is to reduce losses in long wire runs. This is especially true for 12V systems and also why most newer systems are now 48Volts. But it doesn't always make sense in a system with short wire runs. Determining exactly how much energy is wasted or saved is an exercise involving a load analysis for every device used. It is time consuming but not very difficult. The formula is straight forward.

Storing 44 gallons under pressure may not be the most energy efficient, just as storing 40 gallons of hot water heated by electricity. Which is why some sytems use a storage cistern and gravity feed and either insta hot water or solar collectors for hot water. If you also used solar collectors for hot water then the more you store the better. The thermal mass of lots of hot water could help keep th ecabin warm in winter. Then bypass most of the tanks in summer when hot water capacity is not needed.

Regarding the cheap rv water pumps....I meant reasonably priced and if they shit the bed you just buy another....... again could I just pump water from my well to a storage tank in the cabin with a 24 volt pump and figure out a way to start and stop the pump when the tank is full. then use the rv pump to get water to the shower, toilet and washing faucets. No I did not have the system designed by a so called professional... Common sense and hard work prevailed. Also thanks to the internet.... I realize that I won't beable to entirely power the cabin with solar panels and I will always need the gen set. I do have the water restricted in the shower and other users. My hot water comes from a tankless propane water heater and only comes on with demand. thanks for you input..

Nothing wrong with designing it yourself. No one said you had to pay a professionalto do it. Yes common sense is great, provided it is applied correctly. RV pumps can provide pressure but at a flow rate somewhat slower than city water. Most of them can realistically deliver 2.5L per minute. Some pumps are rated at 3.2L and even 4.5 L per minute. But pipe diameter and lenth may reduce these figures. However what I was getting at was determining the comparative losses between using an AC pump and reducing losses in the higher voltage lines but living with the 10% extra loss in the inverter versus going direct DC 24V to a distant pump and getting maybe 15% losses as a result of line losses. The cost of using much larger wires to compensate for the longer wire run is usually not an option. However that is yet a third cost consideration.

Also, a pure DC system my in fact have lower MTBF than a more complex inverter based system.

If you already have an Insta hot (no storage ) propane water heater, so much the better. A gravity tank based system in combination with a solar collector may prove quite useful. Sine the tank would presumably be located up high and thus closer to the roof, a thermo siphon instead of a powered circulation pump might also have reduced power consumption benefits.

By design I meant doing a full load calculation for the entire system rather than simply adding on bits and pieces as the idea occurs to you. In it's simplest form a load sheet is just a list of all electrical appliances; the power consumption and the duration of use in a 24Hr period. You can get fancy and use a spread sheet so that when you play "what if" and change pieces, the final total is automatically adjusted. Now you have a real oversight as to how various options compare. I have seen some load sheets also include cost per energy unit. For an example, propane often looks like a good energy saving option. That is until you look at the $$ per BTU to heat with. It may be cheaper to use some other energy alternative.

Here in the PNW elecric grid power is so low per kilowatt that sometimes it actually is cheaper over a 10 year period to run in a $30,000 power line than to go off grid. Usually this not an option to consider in the Mid West.

Finding a way to control pump cycle as gravity tank empties and needs refilling, is easy. Several forms of float switch arrangements use form C contacts on their micro switches so you just wire it to suit. NC insead of NO. If you are into scrounging, get a water level switch from an automatic washing machine. These switchs are hydrostatically operated diaphram switches and they do have a form C micro switch. You simply adjust them to start the pump when hydrostatic pressue drops and stops the pump when pressure rises again. Same as they do in the washing machine. Its one of the things that rarely breaks down in a washing machine. A scrapped unit would often still have a working switch inside.