Battery bank and inverter options

MainerInExile · December 2009

Howdy all, first time poster. I've been reading through the archives, lots of great stuff in here.

I'm working on helping my parents design a solar system for their house in Maine. They have been off-grid for over 30 years (I grew up there), using a generator for power when they need it (basically for pumping water, laundry, dishwasher, etc.), plus a small 12V battery system for a few lights, wood heat, propane refrigerator, hot water, stove.

I have been pushing them to add a little solar and improve the battery/inverter system for years, and combination of high diesel prices and dropping solar prices is finally getting them to think seriously about doing it. Their current generator is great, by far the best of any they've had -- an 1800 RPM diesel, 6 kW, but it's getting on in years and hours (I think they're up to around 6000 hours and 6 yrs old).

I see two primary objectives for this effort:
1. Save money by cutting back on diesel fuel use.
2. Provide reliable backup for a few days if the generator has an issue and try to avoid running the generator when conditions are the worst (i.e. no more starting the genny when it's below 0, which happens a fair bit, but usually coincides with sunny winter weather and fresh snowfall).

I see a few secondary objectives:
1. Making their house easier to operate as they get older.
2. Allowing them to install an automated heating system that will keep their place from freezing so they can travel during the winter.

Where I'm headed is a small solar array (around 0.8-1kW) and a battery bank/inverter that can be charged from the solar array or the generator. They would still run the generator quite a bit during cloudy periods and to run larger power tools (planer, table saw, circ saw, etc.). We'll do some major energy efficiency work inside the house to cut down on consumption, too.

So, now I get up to my questions. I want to design a battery bank and inverter system that will allow them to potentially expand the solar array and battery bank at a future date. They already have 4 x 6V 225 Ah T-105 clones (I think they are DEKA) purchased last year. Their max draw would probably be around 3-4 kW right now, with a shallow well pump, washing machine, vacuum and small microwave running all at the same time.

On the batteries, where should I locate them? Can I put them in a box in the basement with a vent tube to the outdoors? It regularly gets down to 20 below in winter there, and can get as cold as 40 below.

On the inverter, I want them to get a pretty good quality sinewave inverter so they can run electronics without a problem. I'm looking at Xantrex XW, Outback VFX, and Magnum MS-AE. I hadn't really heard of the Magnum product, but it sounds like a high quality product. Any thoughts on their equipment compared to the Xantrex or Outback equipment?

On battery bank design, I'm sort of debating between a 24V and 48 V system. One possibility would be to get 4 more T-105s and run a string of 8. That would give me 5.4 kWh storage with a 50% depth of discharge, which would probably let them limp along for 3 or 4 cloudy days if they were trying hard to conserve juice during a generator outage.

Could I draw 4 kW or a 6 kW total during a theoretical max load pump start off a string of 8-T105s? If I was drawing 50V off the batteries, that would give a current of 120-150A during the surge, depending on efficiency, which seems like an awful lot. Can I draw that kind of current on a battery like that for a short burst? I'm expecting a more typical load to be a few hundred watts or less with some periods of 1-2 kW.

Another question is can I mix battery manufacturers/sizes on different strings if I keep the same overall battery type? I.e. could I run a 24V array with a string of 4 T-105s and a string of 4 L16s?

Given the prices I have seen on stuff, I'm thinking about a Magnum MS4448 AE and 4 more T-105s (for a string of 8) with a string of 4 or 5 large solar panels totaling around 1 kW run through a MPPT. I think we'd look at adding another string of solar panels and another string of batteries at a future date, depending on output stats from this one.

mike95490 · December 2009

Re: Battery bank and inverter options

If you will need 240V for large motors or pumps, the XantrexXW's can do that, otherwise you need transformers, or need to gang 2 inverters together.

XantrexXW need a 240 generator, to use their internal hi-amp charger for the batterys

For hard starting motors, I've heard the XW has a good surge capacity, and the higher voltage battery bank is the way to go.

Cariboocoot · December 2009

Re: Battery bank and inverter options

You might want to look into designing a system based on the XW 6048 and use it to replace the generator, saving diesel fuel consumption for cloudy days. But the question is how much money are they planning to invest? I don't know what they're currently spending on diesel, so it's hard to guess what the dollar trade-off would be here. And of course the big question is how many kWhrs are needed per day?

MainerInExile · December 2009

Re: Battery bank and inverter options

Thanks for the replies, folks.

It's unclear exactly what they can get their consumption down to. Right now, they basically use a bunch of inefficient stuff when the generator is on and don't think twice about it. But I'm assuming they can easily get down to about what I use in my house, around 4-5 kWh/day, and maybe less. I plan to submeter some loads (esp. water pump) to see where the draws are. I will fully optimize the system, so we will replace every lightbulb in the place, plus consider a water pump, washing machine, and dishwasher upgrade.

The objective is to basically eliminate the generator use during the sunniest months of the year, running the generator more during extended cloudy periods and during the dark, cloudy winter months. We might consider adding another system element in the future, like a wind turbine (not likely) or another string of PV panels (much more likely). I figure the generator costs around $800/yr in capital and maintenance (plenty of oil changes), plus they run it about 1000 hrs/yr and use about 0.5 gallons of diesel/hr. At $4/gallon, that's another $2000/yr, $1500/yr at $3/gallon. I'm figuring we could cut their generator use by at least 50% with the system I had in mind. So that's $1200-1500/yr in savings, plus we add quite a bit of convenience to their lives, and open up a whole new world of possibilities (like automated heating, maybe a chest freezer, showering without turning on the genny, etc.) So if we get a system cost of around 8-9k and the feds kick in 30%, we'll be at around a 5 yr payback.

They don't currently have any 240V loads, but the generator feeds 240 with a neutral to the main panel in the house, so I'd like to keep the circuits balanced the same and try to reduce the funkiness in at least one element of their system.

I'm pretty much set on a higher voltage system, to keep the wire sizes down. So if I'm pretty much settled on 120/240 out and 48V in, the big questions are:
8 vs. 16 T-105s?
XW 6048 or 4548 vs. Magnum MS4448-AE?

Does anybody have experience with the Magnum equipment? I've seen and touched and played with the XWs in action and liked them alright (we had some of the first ones on our Solar D house in '07). But the Magnum equipment is enough cheaper and appears to have the same feature set. Thoughts?

halfcrazy · December 2009

Re: Battery bank and inverter options

I use a lot of the magnum stuff my house here in Maine runs on a magnum inverter feel free to come check it out. They are a lot more affordable then the XW line a few less features but for a offgrid enviroment i think they are a great bang for the buck

dsp3930 · December 2009

Re: Battery bank and inverter options

A Xantrex XW6048 will set you about about $3k plus the cost of #6 AWG circuit wire, and conduit, etc you need to hook it up.

It hooks into a 60A dual pole breaker at the bottom of your main panel for powering the unit from mains power. (and selling back if desired). That connection is called AC1. If you don't have a mains connection, then AC1 is never connected.

AC2 is for your generator connection. It requires a 120/240v generator. (If the Xantrex units likes your generator, it will sync up.) If/when AC2 has no input, it will draw power from your battery bank. The output from the inverter is sent to the Load (L1/L2) connection that is hooked into your subpanel via a 60A dual pole breaker. (or your main panel if you aren't grid connected and don't have a sub) The inverter will support up to 6k watts constant or 12k watts surge.

The Xantrex unit also has a built in 2 or 3 stage charger for your batteries if AC1 or AC2 are connected.

The MPPT Solar Charge controller by Xantrex runs from $450-600 and charges your batteries (or provides excess power to your sub panel if your batteries are full).

mike95490 · December 2009

Re: Battery bank and inverter options

I'd use the larger battery bank, and the XW.

But I know nothing about the MS4448

icarus · December 2009

Re: Battery bank and inverter options

4-5 kwh/day is a pretty big load on a battery based system. Something on the order od a 2-4 kw Pv system,at ~$5-10/watt. Since you are experience with off grid, we don't have to remind you of the conservation, first, conservation second, conservation third argument.

That said, any off grid system loads WILL grow with time. The biggest mistake folks make is under estimating their loads, and overestimating their solar input.

Tony

BB. · December 2009

Re: Battery bank and inverter options

Using the PV Watts website, assuming 1kW of solar panels, and derating of 0.52 (panel, charge controller, battery, inverter losses) for Caribou Maine:

"Station Identification"
"City:","Caribou"
"State:","Maine"
"Lat (deg N):", 46.87
"Long (deg W):", 68.02
"Elev (m): ", 190
"PV System Specifications"
"DC Rating:"," 1.0 kW"
"DC to AC Derate Factor:"," 0.520"
"AC Rating:"," 0.5 kW"
"Array Type: Fixed Tilt"
"Array Tilt:"," 46.9"
"Array Azimuth:","180.0"

"Energy Specifications"
"Cost of Electricity:","12.2 cents/kWh"

"Results"
"Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
1, 3.36, 58, 7.08
2, 4.34, 67, 8.17
3, 5.23, 86, 10.49
4, 5.75, 89, 10.86
5, 4.99, 74, 9.03
6, 5.09, 71, 8.66
7, 5.15, 73, 8.91
8, 4.99, 72, 8.78
9, 4.26, 61, 7.44
10, 3.45, 53, 6.47
11, 2.38, 35, 4.27
12, 2.73, 46, 5.61
"Year", 4.31, 784, 95.65

If you aim for 9 months of the year with no generator use, that would give you January at 58 kWhrs per month or nearly 2kWhrs per day minimum (this is at the 120/240 VAC outlet).

You can play with the numbers and settings to better estimate your system requirements/expectations.

-Bill

stephendv · December 2009

Re: Battery bank and inverter options

When considering the maximum loads, bear in mind that some inverters have a "generator assist" or "boost" or somesuch feature where they can add their own power to that of the generator. So if 95% of the loads are less than 4kW, but once in a while they need 8kW, the inverter can power on the generator and then assist it. So you don't need to splash out on a bigger inverter for the 5% of the cases that need that power.

AFAIK, the Xantrex XW, SMA Sunny Island 5048, Victron's have this feature, but the Outbacks don't. Don't know about Magnum.

MainerInExile · December 2009

Re: Battery bank and inverter options

Thanks again for the various replies. I sort of forgot the other big question...

Where should I put the batteries and inverter?

The array is going on a detached garage maybe 100 feet from the house. The generator is in another outbuilding 75 feet from the garage and 125 feet or so from the house. Right now, there's AC wiring (not sure of the gauge, but I think it's enough to carry 25 kW) going from the generator to the house.

I want to minimize power line losses, so I'd like to keep my DC runs short (plus I'm going 48 V on the battery bank and may go higher on the array).

Right now, I'm thinking about building a battery cabinet in the basement, with a vent tube to the outside, below the room with the existing AC panel, and mounting the inverter adjacent to the existing panel.

This would mean I want to run a high voltage array, so I can cut down on the wire size and losses for the run from the garage to the house. I'd probably want a solar array disconnect both near the array at the garage and by the inverter. Does this sound about right?

BB. · December 2009

Re: Battery bank and inverter options

Where to place the batteries and inverter on a system with significant distances involved is always a tough question...

From an electrical point of view, make the "long run" high voltage... For your system, that would be ~Vmp=100 VDC panels or 120/240 VAC from the Split Phase inverter (if you choose a split phase inverter).

If you end up with a pure 120 VAC inverter system, then the 100 VDC vs 120 VAC probably no real difference--and I would choose to put the inverter+battery bank next the home.

Next, Batteries in the Basement. As long as you have ventilation and a decent battery box (keep acid fumes, if any, away from valuables and electronics, vent hydrogen gas safely, keep tools and kids from touching the battery connections, etc.). Aim to keep the batteries around 70-80F (below 32F/freezing, they loose capacity, above 120F or so they fail from heat).

Keeping the generator shed separate from your solar shed/array/battery bank is probably a good idea (one user here had a fire with his genset and took out his entire PV Array/battery bank/inverter/charge controller setup).

I would not worry about adding a second DC cutoff at the array from a safety point of view... Also, depending on your eventual PV Array configuration, there is a good chance you will need a combiner box + circuit breakers anyway for the solar array (for safety reasons)--so there will be a manual cutoff there anyway.

By the way, is there a reason you want the array on the garage vs just mounting the panels on the ground (assuming you have a good place for the panels)? It makes them easier to keep clean, possibly to clear snow (if an issue for your area--mount them a bit high on the ground for room for snow to shed from array--tilt array at steeper angle in winter for more sun, better shedding).

Mounting the array on the garage may provide a bit better security (less obvious to thieves, a bit more difficult to get at). Figuring a way to alarm them (if appropriate) may be a good idea too if your parents travel for extended periods (panel theft has been a problem in some areas--perhaps less now that prices have dropped).

-Bill

solargirl · December 2009

Re: Battery bank and inverter options

Quote : Aim to keep the batteries around 70-80F (below 32F/freezing, they loose capacity, above 120F or so they fail from heat).

BB
I have my batteries in an wooden box that is insulated, during this last cold spell we had it got down to 28 here at night for 2 days , I have a mini temp laser and tested the temp of the batteries they were 42 degrees.

Now I am worried about keeping the batteries cool in the summer, it gets really hot here 90 to 100 most days in the summer.

Any ideas Anybody?

BB. · December 2009

Re: Battery bank and inverter options

Put them in a pit in the ground (cool earth year round), or some sort of ventilation that lets cool air flow through the batteries at night?

Hot air tends to rise and cool air fall--so if the batteries are in a low, cool area, they should tend to keep cooler than if you had your bank in the attic.

Batteries are full of lead and electrolyte... So they have a lot of thermal mass. Measuring the temperatures once in a while will give you a good idea if you are going to have problems or not.

-Bill

PS: To give you an idea how temperature affects batteries (and in fact, most every common material including electronics) is the rule of 2 for every 10C change in temperature.
,
If your batteries are 10C (18F) hotter than 25C/77F, they will last 1/2 as long. If they are 20C/36F hotter, they will last 1/2*1/2=1/4 as long.

On the other side, if you cool them by 10C/18F, they will last twice as long.

This is an "aging factor". There are other factors (how many, how deep of cycles, boiling water dry, contaminated water added to electrolyte, charging, equalization) that also affect battery life.

A cool battery that is otherwise badly treated is not going to last very long anyway.

solargirl · December 2009

Re: Battery bank and inverter options

I don't think putting them in a pit is going to be an option for me.. They are built in 3 metal trays, 8 cells per tray and weigh 1500 pounds per tray.

It does cool off here at night so I will just have to wait till summer and see how hot they actually get.

But as of right now I couldn't be happier with the performance of these batteries, the are at 95 % full now 9:30 pm, they seem to be handling the load that I have on them, 4- 6 amps 24 hrs. ( knock on wood)

Tonight the charge controller read 11.5 kw for the day!

I want to thank all of you who have responded to my questions, and given such valuable information.

It has been a long 3 months since my husband passed, and this is one less thing to worry about.

Thankyou

Solargirl

icarus · December 2009

Re: Battery bank and inverter options

In the heat of summer, ensure that they have as good ventilation as possible, perhaps drawing air from a crawl space or basement. Keep them away from high ambient heat and direct sun if you can. Put them in an insulated enclosure that protects them from high heat, but will exhaust heat and draw in cool air. A simple temperature controlled ducted fan (like the Zepher) will move a lot of air on little power. If you have a 50 cu ft box, and it's air inlet draws air from under the house or the cellar, wit will be cooler, and venting it out the top. Serves the dual purpose of keeping the batteries cool (er) and vents the Hydrogen at the same time.

I personally "worry" more about warm batteries than cold, even living where we do. MY batteries routinely see ~30 several times a winter, and are below freezing quite often.

Tony

arkieoscar · December 2009

Re: Battery bank and inverter options

I had never seen the magnum products. It looks like a cheaper alternative to Xantrex. You already have one user's experience. I would speak with some of the dealers to see if they think it's comparable in quality. It's only about half the weight of the comp. Xantrex but I not sure if that means much. I'll be looking into using them in the future. Saving $500 on the inverter could buy some more battery or PV.

Sheldon · December 2009

Re: Battery bank and inverter options

i'm hoping to use my batteries to load shave, here in Central Ca (near Gilroy) where it can be over 100F at 4pm.

Had not thought about them being too hot, they will recharge after its cool outside on "off peak" where over night ambient is typically 50F (planning to have a 4.5 kw inverter and a 1kw turbine with eventual 3kW PV, so charging from grid is likely) Sounds like I need to make an insulated box for them, with convective and forced venting, as well as providing reflective surface to cut radiative heating.

Anyone make an option for the XW system that will control a fan ?

BB. · December 2009

Re: Battery bank and inverter options

I would recommend that you look at the costs (and losses) running a battery based hybrid/off-grid inverter for load shifting...

A few years ago, I went through the math for a simple setup of a off grid inverter, battery charger, and batteries. Assuming the batteries are discharged 25% a day, and ~10 year life for good quality batteries -- came out to, very roughly, $0.45 per kWhr just for the hardware and batteries. Add then utility charges around here of $0.084-$0.41 (off peak summer E-6) vs peak charges of $0.30-$0.62 per kWH summer peak.

Load shifting may not be a very good way to save money.

-Bill

mike95490 · December 2009

Re: Battery bank and inverter options

Load SHAVING, use a simple Grid Tie PV system, and feed directly from the PV, which will offset your usage. Enough PV, and you spin the meter backwards. But the utility may not have your efforts in mind, be careful they don't extend your peak rate till 8pm. That's killer after 6pm, when there is no sun

BB. · December 2009

Re: Battery bank and inverter options

I believe that PG&E (Northern California may include Gilroy) requires E-6 Time Of Use Rate Plan for new Grid Tied systems (may also be able to use E-1 flat rate too).

I have E-7--but a few years ago, the powers that be probably decided that E-7 was too advantages for Grid Tied Solar folks (peak is Noon-6pm week days).The E-6 plan has peak to 7pm and partial peaks to 9pm weekdays:

It is pretty easy to delay dinner/laundry until 6pm... 9pm would be much more difficult and I probably would choose flat rate metering (or even the new Smart Meter plan--if it is available) as the TOU E-6 plan is way too complex to effectively manage power unless there are some optional heavy loads (electric vehicle, well pumping to holding tank, ice making at night, etc.).

E-6:

3. TIME PERIODS: Times of the year and times of the day are defined as follows:
Summer (service from May 1 through October 31):

Peak: 1:00 p.m. to 7:00 p.m. Monday through Friday

Partial-Peak: 10:00 a.m. to 1:00 p.m.
AND 7:00 p.m. to 9:00 p.m. Monday through Friday

Plus 5:00 p.m. to 8:00 p.m. Saturday and Sunday

Off-Peak: All other times including Holidays.

Winter (service from November 1 through April 30):

Partial-Peak: 5:00 p.m. to 8:00 p.m. Monday through Friday

Off-Peak: All other times including Holidays.

Holidays: “Holidays” for the purposes of this rate schedule are New Year’s
Day, President’s Day, Memorial Day, Independence Day, Labor
Day, Veterans Day, Thanksgiving Day, and Christmas Day. The
dates will be those on which the holidays are legally observed.

-Bill

Sheldon · December 2009

Re: Battery bank and inverter options

Its going to be E6 metering, according to PG&E, we have one of the old meters at the moment, will need to get it updated for net usage. By adding Xantrex XW4548 with a 1kw turbine to the eventual 3kw PV we end up with a calculated power bill of less than $1 a day (currently running closer to $10 a day)

That involves load shifting things like pool pump to off peak, some time based fans to pull cool evening air into plenums and to chill winery and selling from the turbine, PV and batteries during peak.

Calculations show that I'll need about 100Ahr usage to cover 1-7 peak time with anticipated 800 W of wind and 3 kW of solar during peak usage June-Sept

solargirl · February 2010

Re: Battery bank and inverter options

No problem yet but I think I will run into one if I don't fix this,

Trace Inverter 4048, when charging with a generator at night there is somekind of a cooling fan that usually comes on after while.... it isn't coming on.

So I have put a small fan up where the vent holes are just to keep it cool while I'm charging. I haven't had to use the generator much but I don't want to burn up the charger in the inverter.

Who do I call, What should I do?

Thanks
Solargirl

BB. · February 2010

Re: Battery bank and inverter options

I believe the Trace/Xantrex SW line is obsolete and there are few, if anybody, servicing.

The fan may have failed--and you can probably replace that (or somebody else with knowledge of basic tools/electricity). Also, it is possible that cold weather may be keeping the unit cool enough with your limited usage....

-Bill

solargirl · February 2010

Re: Battery bank and inverter options

Thankyou for your quick response BB

This inverter is 9 years old, how long do most go?

So then my next question is, What is the best inverter out there?

Something similar to what I have ?

BB. · February 2010

Re: Battery bank and inverter options

10 years is an OK life--5 would probably be short, and 15 would be pretty long (from what I have seen--others may have better ideas).

If the inverter is running fine--fan replacement is a normal thing (fan bearings will generally fail before the electronics) and you should be able to find a "computer type fan" to replace it with (guessing--I have never worked on any modern inverter).

I believe you would need to backup your setup (menu option) as it may be lost when you remove battery power (read elsewhere here).

Perhaps somebody here has changed a fan in their SW setup and can give you some guidance.

Since I am not in the solar business--just a volunteer Moderator here--I will point you to our host as a place to start looking for good quality equipment (us two moderators are not connected with our host either--other than keeping spam out of this forum).

The best bang for the buck right now is the Xantrex XW family (several generations past your Trace/Xantrex SW line--is a Hybrid inverter--can do both off grid and grid tied operations from 24 or 48 volt battery bank). Take a look at the XW 4024 model if 4kW and you want to stay with 24 volt battery bank (and rest of system). The XW 6048 would be your "ideal" model if you can migrate to a 48 VDC battery bank. Not much more expensive and a 48 volt battery bank reduces the DC current by 1/2 because of the higher voltage.

Of course, you should review your past and futures loads, battery bank layout, and other options for your upgrade...

For now though--a $25 fan and an hour of work to replace it may be a better investment (we are a practical and "cheap" bunch here

).

-Bill

solargirl · February 2010

Re: Battery bank and inverter options

BB. wrote: »

10 years is an OK life--5 would probably be short, and 15 would be pretty long (from what I have seen--others may have better ideas).

If the inverter is running fine--fan replacement is a normal thing (fan bearings will generally fail before the electronics) and you should be able to find a "computer type fan" to replace it with (guessing--I have never worked on any modern inverter).

I believe you would need to backup your setup (menu option) as it may be lost when you remove battery power (read elsewhere here).

Perhaps somebody here has changed a fan in their SW setup and can give you some guidance.

Since I am not in the solar business--just a volunteer Moderator here--I will point you to our host as a place to start looking for good quality equipment (us two moderators are not connected with our host either--other than keeping spam out of this forum).

The best bang for the buck right now is the Xantrex XW family (several generations past your Trace/Xantrex SW line--is a Hybrid inverter--can do both off grid and grid tied operations from 24 or 48 volt battery bank). Take a look at the XW 4024 model if 4kW and you want to stay with 24 volt battery bank (and rest of system). The XW 6048 would be your "ideal" model if you can migrate to a 48 VDC battery bank. Not much more expensive and a 48 volt battery bank reduces the DC current by 1/2 because of the higher voltage.

Of course, you should review your past and futures loads, battery bank layout, and other options for your upgrade...

For now though--a $25 fan and an hour of work to replace it may be a better investment (we are a practical and "cheap" bunch here ).

-Bill

Thanks Bill

I will have someone look at the fan, but I think I should also look at a new inverter before next winter, I am not on the grid and I'm way out in the middle of nowhere so it might be a good idea to have the old one for a backup? My battery bank is a 48 volt so I'll look at the 6048. Thankyou for your help !

BB. · February 2010

Re: Battery bank and inverter options

Duh... right there says it is a "4048"...

Regarding a backup--probably depends on how easy it would be for you to wire in the SW 4048 as a backup... May not be fun.

If you have a local distributor--find out what they stock as spares for their customers (if you are one already). You buying two of these XW 6048 is probably not a good idea (lots of $$$$). However a spare small genset + battery charger + "small" inverter for backup use (just enough to limp along until you get your main system backup) would probably be a good idea... You have both backup for your major components--and probably portable enough you can help a neighbor (or do some remote construction/off site work) and/or share the backup components/costs.

Also review your loads--(a new laptop with more processing power, same or less watts, lighting, appliances, insulation, , etc., to keep your power usage down).

Also, if it has been 9 years since you last did a major upgrade for your off-grid system--MPPT Solar Charge Controllers have come a long way, and solar panels are (yes, I am Mr. Obvious here) have come way down in price--reduce your generator runtime. Remote Battery Temperature Sensor for the Battery bank / Charge Controller. A battery monitor.

Keeping genset usage/size down and overall power usage low will help keep your off-grid power costs reasonable (I guess you have solar PV panels too).

I am going to bed now--obviously I am seriously short of sleep.

-Bill

solargirl · February 2010

Re: Battery bank and inverter options

BB,

I recently upgrades our batteries, added more panels and had a mppt outback charge controller installed. So I might as well get a new inverted too.

I think since we were always using the generator to keep the old batteries charged , I wore it out.

I am thinking if I put in a new inverted I will be set for at least 10 years, ( I hope)

Thanks

BB. · February 2010

Re: Battery bank and inverter options

The Xantrex XW 6048 is a good place to start... I would plan on 10 year replacement cycle (money in bank).

One question I always have is the Genset/AC Charger/Battery bank sizing.

The XW Inverter (6048 model current listed) has an internal battery charger--Programmable, Power Factor Corrected to 0.98, up to 100 amps (~6kW maximum?), 89% efficient, temperature compensated, etc... It is a very nice set of features (would nice to find a standalone charger family with the same specifications).

So--goes back to the genset rating, fuel type, battery bank AH capacity, and current charger AC current/power settings/capabilities...

If you can run your genset at round 50%+ of rated power--you should be in the most fuel efficient range--and cut generator charging when the battery charging current starts to drop (typically around 80-90% capacity)--and let your solar panels finish the charge (or don't bother to go over 90% state of charge on those days). You really only need to go over 90% state of charge when equalizing the battery bank.

I am "cheap" and hate to see you waste fuel/generator hours.

-Bill

solargirl · February 2010

Re: Battery bank and inverter options

BB. wrote: »

The Xantrex XW 6048 is a good place to start... I would plan on 10 year replacement cycle (money in bank).

One question I always have is the Genset/AC Charger/Battery bank sizing.

The XW Inverter (6048 model current listed) has an internal battery charger--Programmable, Power Factor Corrected to 0.98, up to 100 amps (~6kW maximum?), 89% efficient, temperature compensated, etc... It is a very nice set of features (would nice to find a standalone charger family with the same specifications).

So--goes back to the genset rating, fuel type, battery bank AH capacity, and current charger AC current/power settings/capabilities...

If you can run your genset at round 50%+ of rated power--you should be in the most fuel efficient range--and cut generator charging when the battery charging current starts to drop (typically around 80-90% capacity)--and let your solar panels finish the charge (or don't bother to go over 90% state of charge on those days). You really only need to go over 90% state of charge when equalizing the battery bank.

I am "cheap" and hate to see you waste fuel/generator hours.

-Bill

Let me tell you what I have maybe that will help,

20- 175 watt panels, an outback flexmax 80 charge controller, batterys are crown lift truck, rated at 1381 amp hrs. and as you know I have the 4048 trace inverter

I have a diesel generator 20kw dedicated to the house, the batterys say don't dischage more then 20%.

I am using about 4 to 6 amps 24/7.

Everything seems to be ok when the sun is shining .. But as you know sunny Ca. hasn't been that sunny lately.

Does that help?

Battery bank and inverter options

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