Jerry Wenzel's posts

My location in the woods creates problems for getting sunlight to PV panels.  I'm looking for advice on how best to get a 40" x 40" PV panel about 25 or 30 feet in the air.

I have found several used TV antenna towers, but I'm thinking the wind load from a 40" x 40" panel is going to be considerably higher than a TV antenna.

Any ideas would be appreciated.

What are the power sources and what do you want to do with the power from these sources?

I have my cabin inverter system set up and running temporarily at my house.  It consists of a Xantrex Prosine 2kW inverter and 4 Energizer 220ah GC2 Batteries in a series/parallel connection to feed 12 VDC to the inverter.  I have some questions regarding the settings on the 100A battery charger built into the inverter.  Here are the settings that the Charger defaulted to when I selected generic flooded cell and entered 440 ah battery capacity.

Bulk Charge
Max Current 10% of battery ah capacity (Defaulted to 30%, I thought that was too high)
Max Voltage 14.4V
Absorption Charge begins after a time delay of 3 minutes at or above 13.5V

Absorption Charge
Max Current 44A 10% of battery ah capacity (Defaulted to 30%, I thought that was too high)
Max Voltage 14.4V
Max Time 8 hours.
Overcharge begins after a time delay of 3 minutes at or below 2.5% of battery ah capacity

Overcharge ( This is not explained very well in the manual other than it is the second half of the Absorption step)

Overcharge and Float also have settings but I don’t want to get too long with this message.

One question is about the 13.5V setting to begin the absorption charge seems low.  Any advice on a typical number there, on what is the overcharge part of the absorption step and any other advice from the gurus here would be appreciated.

Thank you,

Jerry

Ken,

I was planning on venting the top of my battery box to the outside of the cabin.  I have seen where some users have put in a small fan to assist venting during times of higher charge rates.  I'm not sure if the fan is overkill or not.

Your comments on the large thermal mass of the batteries is well taken.  My thought with the insulated battery box is that it would keep the batteries colder longer if we did do a winter trip.  Whenever we are at the cabin, we adjust the temp with windows or wood stove to be comfortable for us.  I also want the batteries to get to room temp ASAP, thus the uninsulated box.

Thank you,

Jerry

Ken,

Yes, I'm using 4/0 cable.  And your right, I picked up the AWT term from someone selling battery & inverter cables.

In regards to the igloo cooler.  I don't expect to use my cabin much in the dead of winter in NE WI.  Gets below 0 sometimes, -10 below may on a couple days.

My batteries will be in the cabin.

I'm thinking the cooler is eventually going to get as cold as the outside.  If kept topped off by a PV panel, the batteries should be good for -40 deg F.  Here comes my next set of questions:

Does keeping batteries float charged with a PV panel warm them to any extent?

If I'm not using them and its not cold enough to freeze them, is there any advantage to having them in a cooler to trap that charge heat?

Thanx,

Jerry

Ken,

Do you know if there are any known problems with a marine battery disconnect in off grid installations?  I was looking at using one and I thought I read where someone was not recommending them because they heated up.  The model you pointed out looks heavy duty, and the fact that its marine grade and designed for use in gasoline powered engine rooms leads me to believe it must be safe.  I don’t have inspectors to worry about, I just want something that’s long lasting and safe.

BTW, I decided to go with the 4 AWT cables so I don’t have to worry about upsizing later.  SAMs club has Energizer 220ah GC2 batteries for $65.  I’m thinking 4 of these would be a good set of “learning” batteries.  A local farm supply store has a small high strength plastic pickup truck tool box that will hold 4 L16s.  Any reason why I shouldn’t be looking at using that for a battery box as long as I vent it?

Thank you,

Jerry

Ken,

Thank you for your on-going support.  The Prosine does have a good charger, it is a fairly efficient inverter and I already have it, so should probably use it. It also has a "shore power" current limiting feature.  It monitors generator power consumption and backs off charging current if other loads, connected through the inverters transfer relay, need the power.

I never planned on running 2 appliances at once.  I just didn't want anything to get damaged if it did happen.  The Prosine can provide 2kW continuous and 4.5kW surge.  Now that I'm planning on using it, I was thinking about putting either a 10 to 15A breaker on the AC output of the inverter to limit it to providing 1200 or 1800 Watts.

Leaving the technical aspects and looking some more at why I'm putting in a system that could handle an appliance.  Our new cabin is going up next to a multi-family cabin that has its only electric light in the outhouse and no running water. 

Its clean but primitive.  I don't much mind it and can identify with your and Thomas Allen Schmidt's comments on simplicity.  However, the rest of my family, particularly my wife and daughters, like being at camp, but don't like the outhouse, lack of running water, inflexible gas lights etc.  Along with building the new cabin for more room for our family, another reason was to give it some more conveniences without going overboard.  I enjoyed this area as a kid and I'm trying to strike a balance in creating something my kids and grand kids will enjoy.

In using the Prosine, I'll need the beefed up DC power system.  But once its in, with the exception of a bigger battery bank, I should be set for the future.  A friend has some 350 MCM cable for me.  I need to see if I can get lugs crimped on the 350 MCM or look at buying prelugged 4/0 cables.  I'd like to post my DC cabling and protection for review once I come up with a design.

My first question regards to the DC system.

If I'm committed to limiting the inverter output to 15A or 176A DC ((15A*120VAC)/12VDC/0.85 eff) should I use a 200A fuse even if the inverter and DC cabling can handle 300A?

If I use a fuse instead of a breaker, do I need a disconnect and if so are there any suggestions on disconnect types.

With my solar exposure, there are 2 trees south of the cabin that may block sun in the non-summer months.  I could cut them down if needed.

The reason I said future PV panels is because I was planning on not installing them until late fall or spring.  We are busy finishing the cabin and using a 3500W genset to run tools and it could charge the batteries at the same time.  However, if I want to leave the batteries at the cabin this winter, I think I should have the PVs up to keep a float charge on the batteries and prevent them from freezing.

I have a 3500 watt Kohler genset with manual start.  I also have access to a 1000 watt "cheapo" generator.  At this point I'm trying to decide if I should size my batteries and inverter to handle a 1000W kitchen appliance load and a 200W lighting/small TV/fan load or nix the ability to run kitchen appliances off the inverter and put in a 300W inverter.

If I do just the lights, I will likely put in a remote start genset for other high power, low use kitchen loads.  If I do that, I could possibly depend on the genset for most of my battery charging and use a PV to do the finish charging.

In regards to using a charge controller (cc) for charging from a genset powered DC supply.  It looks like some ccs can take DC from a variety of sources.  The Xantrex C series appeared to be able to do this.  I have a 24VDC 25A power supply I was thinking of putting between a genset and a cc. 

Could you let me know what problems you see with that approach?  I know its more pieces.

Also, do you know of AC multi-stage battery chargers that allow you to limit the max charge current so as to not exceed 10% of the ah rating of the batteries?

Thank you for you patience.

Ken,

Initially I wanted the convenience of the family being able to have lighting and use of small appliances "at their finger tips"  IE They need to conserve but power is there when they need it.  The 2 appliances I thought we would make intermittent use of were a microwave and toaster.  To run one of those at a time and have extra for lighting, I got the 2kw inverter.

After doing more homework, I began to realize the challenges and expenses of feeding a 2kw inverter with adequate DC power.

In looking at my loads, I had the 1000+ watts to run a appliance and 165 watts of lighting load.

It got me to thinking whether I could simplify and reduce costs on my system by giving up the ability to use 2 appliances or putting them on the generator.  I'm also thinking a 300W inverter is going to be more efficient at providing 100 watts of lighting load than a 2000W inverter.  I have questionable solar exposure and think I have a better chance of future PV panels keeping up with replacing lighting power than what the 2000W inverter will consume.  I also plan on eventually upgrading to a remote start genset so using kitchen appliances would be able to be used with the flick of a generator start switch.  A kitchen on a genset also allows the use of long running heating appliances like griddles, quesadilla makers, blow dryers etc.

I rushed into getting the 2000W inverter. But I have learned in the past weeks that off grid power systems require some thought to serve a family’s needs and still be cost effective. I want to step back and take a realistic look at what best fits my needs and budget.  The cabin is new, no wiring yet and the walls are wide open. 

My question at this point is do I spend the extra $500+ on upsized batteries & DC cabling/breakers or do I sell the Prosine and put in a system that can provide power for CFL lighting and other small loads.  I’m not in a rush to make that decision and I want to take the time to get the system right for our needs. 

This forum has been great for learning and I welcome more feedback.

I’ve been learning a lot on the forums.  I’ve been asking questions regarding a cabin with a 2000W inverter system and the maximum current I can pull from a set of golf cart batteries. (See Lead Acid Max Discharge thread) I wanted to be able to run a couple of small kitchen appliances, along with CFL lighting.  At this point the appliances were a 1000W microwave and 800W toaster. 

I bought a remanufactured Xantrex Prosine 2000W Inverter/Charger.  I liked it because it has a built in charger, pure sine output, and a sophisticated remote display with a lot of monitoring functions and settings.  However, I underestimated the cost, wiring size and battery bank to provide this inverter with 200 to 400 AMPS of 12VDC.  1500+ Watt loads would be short term, but still the system needs to be sized to handle what the inverter can pull.

When looking at my other AC loads, they are 165W of CFL (Assuming all the lights are on) and maybe a small TV or a Fan.  I’m now rethinking my approach and considering a smaller inverter with the bigger loads run by the generator if needed.  The generator would also charge the batteries whenever it’s running.

With taking the big loads out of the equation, I now estimate 450 watt hours per day.  At 20% DOD, my battery capacity should be 222 A/H which can be met by a set of 6 Volt GC2(T-105) in series.

I’m looking for feedback on this new design and suggestions for the equipment. (My initial selections are in parens)

Inverter, pure sine.  (300W MorningStar SureSine)

Battery Monitor (MorningStar Remote Meter connected to Inverter)

Charger, Could I use a solar charge controller and feed it with a DC power supply or unregulated battery charger run by the generator?  When I add PV panels I could use a relay or diodes to allow either the generator DC power or PV panels to feed the controller? (Xantrex C35)

If I use a pair of T-105 225Ah Batteries in series, is 30A bulk charging current to much?

I know I need to fully charge the batteries on a regular basis, but do deep cycle batteries mind getting intermittent bulk charging as the generator is started and stopped for other uses? 

Thank you,

Jerry

Based on the feedback from the forum, I'm looking at upping my planned batteries for an off grid cabin from 2 GC2s (Golf Cart Batteries) to either 4 GC2s or 2 L16s.  My inverter is a 2000W 12V Input Prosine 2.0

Is there any drawback to having 4 GCs in a series parallel configuration as opposed to 2 bigger L16s in series?

If I go with the 4 GC2s is it acceptable to put a 125A breaker off each series pair.  Or do they need to be paralled first and sent through a 250A breaker?

I know if one 125A breaker tripped under load the other would immediately trip.  But the 2 125A breakers would allow the use of smaller cabling all the way to the inverter.

I would take care in either case to keep the cabling identical and in the case of 2 - 125A breakers, keep the breakers identical.

Thank you,

Jerry

Thank you for the feedback.

I like the idea of 1 outlet to limit what can be plugged in.

My philosophy is to make an educated estimate on a system that will provide our off grid power needs.  The support from the community here is definitely helping me become more educated. I know that as I learn I may need to add batteries or more solar/wind charging.  Instead of giving my batteries an early death, I'd rather use the generator to fill in the power shortage until I evolve the system to meet our needs.

Along those lines, I planned on doing the following:

*Educating the family on minimizing power use and hope some of it sticks.

*Monitoring the DOD on the batteries and either shedding load or running the generator to prevent > 30% DOD.

*Recharging the batteries ASAP.  Either solar or generator.

*Limiting the max current the batteries get hit with.

*Checking water and equalizing when needed.

Will doing those things help get more years out of my batteries?

My inverter calls for a 300A fuse/breaker to handle surge loads.  Should I be looking at a 200A breaker, which will limit hitting my smaller battery bank with unexpected surge loads?

Does anyone have any thoughts on whether my process of putting in a estimated system, and filling in with the generator until any shortfalls in the system design are corrected?

Ken,

I calculated my watthour/day usage from the wattage of the load times the number of hours I expected that load to be on.  That's where the 750 watt hours came from.  I don't expect to draw peak current during normal daily use.

I didn't do a good job of explaining why I'm asking about the high 200A+ currents.  My inverter is 2000W with a 4500W surge.  I rarely expect to draw 1500 or more watts.  However the inverter is capable of drawing 200A to 400A from the batteries if enough AC load is turned on. 

I wanted to make sure I didn't damage the batteries if someone turned a microwave and toaster on at the same time, or plugged in a larger power tool.  I'd rather the batteries and DC cabling could handle an occasional high current instead of blowing a fuse or breaker or damaging a battery.

I looked through my inverter manual (Xantrex Prosine 2.0) and don't see a setting setting for max DC current draw.  I need to enter the battery type, but that appears to be for charging use not limiting maximum discharge current.

This is a weekend cabin and will generally only see load 2 days per week.  I planned on sizing the solar panel(s) to take 2 or 3 days to fully charge the batteries after a weekend of use.  I also have a 3000W generator, but would like to minimize its use.

Your comments on the discharging the batteries too much are well taken.  I was thinking I might be discharging the 2 GC2 batteries too much.  For a bigger bank, 4 golf cart batteries or 2 L16 batteries cost about the same.  I'm thinking 2 L16s are a better/simpler solution.

Any thoughts on sizing the batteries and DC supply system to take the loads of high unexpected AC usage?

Are 2 L-16s in series better than 4 GC2 in a series/parallel connection?

Any recommendations on battery manufactures?  Trojan and Crown seem to be popular.

Thank you for your patience! I'm new to off grid power.  I'm enjoying the learning and appreciate the help.

Jerry

Thomas,

My estimate on current draw included inverter efficiency.
 
2000 watts/ 12volts = 167A.  167A / .85 % Eff = 196A.

The 600A was what the inverter manual said was its maximum current draw.

As you said, I don't think a set of golf cart batteries are going to put out 600A.  I'm looking for guidelines on what is the max current draw that a battery can handle.  Which, as you said, battery makers don't seem to publish.

Your correct about the surges only lasting a couple seconds. I only plan on having 1 appliance (microwave, toaster, etc) plus a lighting load on at any one time. 

Now that I'm seeing the size of wire used for a 12 volt system, I do see the logic in running higher battery voltages.  However, this is a weekend cabin with power for lights and a few appliances, so I think the 12 volt system will work fine.  I may look into bigger L16 batteries and check my inverter programming to see if it has a current limit setting.

Does anyone else have any more thoughts on the max current draw on a lead acid battery(s)

Thank you,

Jerry.

I'm planning a solar power system for our weekend cabin and have a question regarding discharge current.  I have a ProSine 2.0 2000 watt inverter with a 12V supply.  The main load in cabin will be CFL lighting which I calculated to be about 425 watt hours/day.  The other loads would be small appliances at about 325 watt hours per day.

A set of 6V GC2 Golf cart batteries (225AH) could handle that load with about a 33% Discharge.  However, I'm having trouble finding what maximum current a lead acid battery can put out without hurting it. At 2000 watts the inverter is going to pull close to 200A.  At its 4500 watt surge its closer to 600A.  Can anyone provide feedback on determining how much continuous and surge current a particular set of batteries can take?

Thank you,

Jerry

I'm looking at purchasing an inverter for my cabin and plan on using numerous compact Compact Fluorescent lamps.  Do Compact Fluorescent Lamps work as well and last as long on a modified sine inverter as they do on a pure sine inverter?