another st charger option

[Lloyd]

Hi Bruce,

They make a fixed voltage, non-temperature compensated charger look like the barbaric piece of battery abusing  crap that it is.

I haven't used on of these, unless it was in the shop recovering a bat that had been abused. Even the best multi stage ac charger running from the ac plug of a generator is very poor, as compared to an efficient dc gen. The need to size the ac gen to the largest load, makes them run most of the time in a very inefficient manner.

Thanks for your help Bruce.

Lloyd

[BruceM]

Llyod,  The MPPT charge regulator as AC charger back end approach is better suited to a 48V system, as the 80 amp units represent a 3500 watt+ charging capacity, which is a good match for a genset. As a single unit they don't have enough current capacity for a 12V system, though they can be put in parallel to do so.  (Hang onto your wallet.)

Few people recommend 12V systems for new off grid systems, these days.  200 amps is not an easy amount current to work with, and real world losses in these systems are problematic.

In your case, with a bunch of 12V marine equipment, I can understand why you'd want to stick with 12V, and your direct DC charging system will make that work well.  There is at least one company making a custom alternator regulator that does temperature compensated, 3 stage charging.




I

[Lloyd]

Hi Bruce,

Thanks for your input....I appreciate you knowledge and incite(I get a little crusty too), along with your willingness give it so freely.

Don't take this as being argumentative, and as Bob said everyone has different needs, with different answers.

While I like many of the attributes of the 48 v sys.

12v has some complementing reason also. Take 6 t-240 6v Trojans series/parallel and you get a fairly resilient 720 amphr bank(for under $600.00)., I've yet to find a lower cost per kwh then this set up.

With the same Trojans, 4 will get you a 24v 440 amphr bank @ under $400.00 dollars, but no resiliency, so you have to ad 4 more(another $400.00, bc if you loose one bat in the 4 group the whole bank is down.

Getting into a resilient 48v sys changes all the parameters, and the cost skyrocket bc now your looking at a whole different bat, and those mothers are big money.

Other factors in favor is the sheer number of 12 v based users ie motors, pumps lights, chargers and any other thing that you need that runs on dc voltage. It's been my experience that once you leave the 12v realm, you have fewer options, at a much higher price point.

There are other issues with 12v, but there are at least 6 that I know of multi-stage charge controllers, w/temp, and true bat sense.  I know that a 24v ho alt is almost 2/3 more then a 12v alt. I have no idea the premium for a 48 volt alt, this is where the mmpt controllers appear to step in.

Other things like high current, and resultant voltage drop. One way of dealing with the voltage drop, is using a distributed panel system, while it may add some complications for the electrically challenged, it's not a big issue for those skilled in dc systems.

Not to mention that a smaller PV can be used...

I'm just talking out loud, so don't get frustrated with me.

Lloyd

Now this is a resilient Bat Bank, if you can afford it.

[Lloyd]

Llyod, Your case for 12V for an off grid system of respectable size doesn't hold water, technically.  There are lots of different AH wet batteries.  A failed battery in either a parallel or series string is equally problematic.  Other arguments of yours are equally erroneous:  smaller PV?  Busses solving distance/loss problems?  AH comparisons for battery banks of different voltages?  Must have a 12V system for a few items that need 12v?  Egads, Llyod.

It's great that you like 12V, know how to work with it and can get by with it for your boat, with some custom engineering work.   But there really are good technical reasons why 48V is being used in most new off grid systems of moderate or larger size.  In the future I think you'll see even higher voltage systems, as you do now in larger facility UPS systems, and in electric vehicles.

12V is still king for small setups, for obvious cost reasons.

Hi Bruce,

While I agree with you on many levels...just not all.

Unlimited dollars and we can do anything...and I agree that the future maybe higher buss voltages.

Now if I have a 6 string 12 v group and I loose a bat, I disconnect that pair, and I still have a 440 amphr bank to limp along on, and since we cant just replace 1 bat in the string bc age, and condition, I have to replace the whole bank.

Now if I have a 4 string 24v and loose one bat. I'm out of business until I replace the bank. Sure we can go to 12 volt bats, but you have be willing to pay about twice as much for the same amphr bat that will preform the same, and your amortized kwh cost will be greater.

I haven't set down to do an amortization of a resilient 48 v bank, but I know going in that the inverters and bats, are going to be more per kwh after amortization, and my upfront cost will be much greater. That being said, I think there will be a day, once production cost are driven down, but we are still early in the manufacture cycle.

At this time in the manufacture cycle, the cheapest even in figuring associated losses is 12 v it's cheaper per kwh, until you start hitting what is larger then 80% of the installed systems.

Lloyd


This may be one of the best info sites on batteries. I will forgo a WP and just add this to the WP section on bats.
http://www.windsun.com/Batteries/Battery_FAQ.htm

[BruceM]

Llyod, I disagree with most of your technical assessment, but I'm glad you like 12V and it works for you.
I wouldn't use it or recommend it for an off grid power system myself unless it was a very small system. In this regard I am in agreement with most engineers and system designers.

Clearly, 12V is king for small systems, for cost reasons. 

[Lloyd]

Bank costs.


2-Volt 1766 Amp-Hour Deep Cycle
Surrette 2KS-33PS Deep Cycle Battery
Item# 2KS-33PS
Regular (MSRP) price: $950.00
Our Discounted Price: $780.00
Availability: Usually ships in 5-7 business days.

12v = $4,680.00
24v = $9,360.00
48v = $18,720.00


Concorde PVX-2580L (8D) Deep Cycle AGM Battery 12 Volt, 255 AH
Sun Xtender PVX-2580L AGM Sealed Battery
Item# PVX-2580L
Regular (MSRP) price: $918.43
Our Discounted Price: $585.00, 2 for $1,164.00, 4 for $2,320.00

12v = $  585.00
24v = $1,164.00
48v = $2,320.00


Crown Battery, 1090 AH @ 20 hr rate, 12 volt, 850 lbs
rown Industrial Battery 6-125-15
Item# 6-125-15
Regular (MSRP) price: $4,452.00
Our Discounted Price: $3,172.00

12v = $ 3,172.00
24v = $ 6,344.00
48v = $12,688.00

things to consider every time you increase the voltage you drop the amp load by almost half that's good, you increase the real estate required the house the bank, and the cost by dbl...that's some thing to consider, As you increase the initial cost you have to increase the fail safes to protect your investment...that's something to consider.

A 48 volt array will take more panels to match the 48v bats, with all of the associated controllers. This increases upfront investment and maintenance costs.

Something that most don't amortize into the deal is loss prevention...1 catastrophic event could wipe out a large investment, and it's likely your home owners policy isn't going to cover that loss. That is unless you purchase a rider upfront, which is another increase in up voltage costs.

Last but not least is the labor cost...up voltage also increases the labor...I'll bet by square.

Bruce...a systems efficiency, have to consider all associated issues, not just those that pertain to electrical losses.

Lloyd

[Lloyd]

http://www.thesolarguide.com/solar-power-uses/cost-faq.aspx

Solar Cost FAQ

What will solar energy cost me:

   if I want to use (a) solar panel(s) to help power my home?

   Solar electricity costs about $10 to $12 a watt installed, though you may be eligible for state incentives. Check your utility bill to see your monthly usage. A robust solar electric system will cost about $20,000. You can spend as much money, to receive as much solar electricity, as you feel comfortable with.

http://solarpanelspower.net/solar-panels/solar-panel-insurance
Does Your Insurance Cover Solar Panels?
What does your homeowner's insurance company think about solar panels?  Do you know?  You may be surprised to learn that your insurance company views renewable energy installations as a potential additional liability, rather than an integral part of your house for which coverage is provided in the event of a loss.  Do you need special solar panel insurance?

Insurance companies have cancelled insurance because of solar panel installations when they view them as "too risky."  95% of the time, these assessments are based on misinformation – or a complete lack of knowledge – regarding solar panels.  I have read about insurance companies that decided solar panels were a fire hazard due to the potential of overheating, and other companies that thought there would be water leaking around the installation.

Still, purchasing solar panel insurance can run you up to an additional $1000 a month!  You'll never save that much in electric bills.


NOW HERE IS A TOOL..everyone should visit http://ideas.4brad.com/solar-economics-spreadsheet

[mobile_bob]

here is my take

a 12volt system can work, and work well "if" you can locate generation and storage very close together.

the big limitation is the availability of high output high quality inverters to make AC from your 12vdc

stepping up to 24volts  helps some, but you don't really get your best bang for the buck till you go to 48volts, but

there is tons of appliances that run on 12, lots on 24, and very few that run on 48volts, which is kinda nuts in my books

even jacobs figured that he would have to produce appliances to run off his 32volt wind gens, why the 48volt manufactures
haven't taken a lesson from history is beyond me, i guess they just figure we will just convert to AC and live a happy life?

the assessment of battery costs, is not really an apples to apples comparison, because the figures don't illustrate
that while the 48volt banks cost 4x the 12volt banks they also have 4x the kwatt/hr capacity.

where i would go with 12volts would be "if" i had a ready source of inverters, and where i could install everything
batteries, generators, panels etc on and in a storage container, and do all the power conversion in a close linked system
and then transfer the 120/240 to the house in a conventional manner.

one thing i now know for sure, is if i were concerned about efficiency of the generation in BSFC, i would go with at least the 24volt
system as outlined in my white paper, and likely would recommend going to 48volts because i am fairly sure there will be another increase
in efficiency of the alternator.

if i were a single guy, i would buy two 20ft shipping containers, set them about 20ft apart, live in one, generate my power in the other
and have room for all the mechanicals and a small shop area to maintain them.  a completely autonomous house. with a greenhouse between
along with a small courtyard area, for a couple rabbit hutches, and put a view deck patio up topside.

then a 12volt system would probably suffice quite nicely.

bob g

[Lloyd]

Professor,

I am not in any camp as a 1 voltage fits all, especially in the state of manufacture cycle we're in...availability of devices is directly proportional to cost and over all efficiency.

I used to be one of those guys whom had to have the latest greatest motherboards, and associated hardware...then I realized I was one of the fools with money(not receiving a return on investment), investing in research and development that funded their(manufactures) bottom line, as profit to the share holders and more funds for the engineers(to tinker with)...this all kept their bean counters happy...and ultimately technology advanced.

But now that I have started to consider amortization into my everyday purchases...I might look like the slow adopter, but....I am getting more bang for my buck...which is good for my bottom line.

So while 48 volt looks to be the most efficient from an engineer's stand point...stop and do a bean counter stand point....based on the current price of the system over all., and net ROI.

I think in another post you hit the nail on the head when you suggested we need to think differently,  conservation, and load timing, added with system design.

Conservation is the biggest ROI. If we can scale back the sys requirements bc of new and better equipment, more efficient design, load management, Conservation is the guy driving the truck, and that guy will save us money at every turn if he's not a lead foot.

Lloyd

[BruceM]

Llyod, you don't seem to realize you can reduce the AH of batteries of a 48V bank by 3/4 and still have the same power storage capacity as a 12V bank. You  pay about the same yearly costs for the same power storage capacity of bank, regardless of voltage or design service life of batteries.  That's consistent with conventional wisdom on wet lead acid batteries and the Windsun battery info article you posted, your statements are not.

First you argue for redundant parallel strings, then you trot out prices for monster 2V cells, which certainly wouldn't be used in parallel.  Or high dollar AGM batteries???

I don't agree with any of your assertions, including the nonsense on PV insurance making PV power worthless ($1000 per month for home power PV).  Your signal to noise ratio is below my tolerance limit, I won't respond further.

Bob,
You beat me to posting the above.  

I agree, for small systems, as I said before, the equipment cost advantage of 12V is there. There is no real advantage in battery costs, as Lloyd has tried to claim.

Most of my off grid friends don't use DC appliances;  they use new high efficiency AC units for a fraction of the cost, that perform in the real world (not marketing brochures) nearly as well.  They would rather put that extra $1500 towards more PV or wind power, or better batteries.

12VDC is very handy to have around.  I have a separate small, low current 12V system for house and shop use in my own off grid setup. It provides the power for the 10 watt house heating circ pump, my fiber linked cell phone receiver, and some other very low power electronics.

Getting a great deal on some surplus equipment would certainly influence  system voltage choice.  If I could get along with inverters, and had some bargain gear and a free set of monster Surrette or HUP 2V cells, I wouldn't mind that 12V system one bit.  Alas, inverters and I don't mix.

[Lloyd]

Bruce , don't get frustrated my noise will result in a more profitable signal.

Llyod, you don't seem to realize you can reduce the AH of batteries of a 48V bank by 3/4 and still have the same power storage capacity as a 12V bank. You  pay about the same yearly costs for the same power storage capacity of bank, regardless of voltage or design service life of batteries.  That's consistent with conventional wisdom on wet lead acid batteries and the Windsun battery info article you posted, your statements are not.

First you argue for redundant parallel strings, then you trot out prices for monster 2V cells, which certainly wouldn't be used in parallel.  Or high dollar AGM batteries???

As I posted, redundancy is important in an off grid, and there's know way to provide redundancy without additional parallel bats over nominal voltage.

The bats I posted are in a range from the biggest money the the mid sized money, it doesn't matter which tier(price point) you decide to buy bats in.

Let's just take  a known, well performing bat that is in the low dollar tier...the trojans t240's

12v  6 X 6v= 3 parallel 12 volt string, with an AH of 720 x (6 x 89.00)= $534.00 that's  0.74 per AH
24v  4 X 6v= 1 series   24 volt string, with an AH of 240 x (4 x 89.00)= $356.00 that's  1.48 per AH
48v  8 X 6v= 1 series   48 volt string, with an AH of 240 x (8 x 89.00)= $712.00 that's  2.96 per AH

Now to get any redundancy in the the 24 or 48 volt bank you have to dbl the cost of each choice. From here it doesn't matter what voltage bank we choose, all we need do is break down to actual wattage used(charge-discharge) to calculate, the true costs of the bat bank on kwh.

Just because the higher voltage has more available, doesn't mean we  are getting a value from that investment...much like the situation where the stand by ac gen is sized to the to the highest load it has to run as opposed to being able to sacle up and down to the actual load.

My whole point is to be true, we have to calculate over all efficiency...and that is in no uncertain terms, the total cost of the system as it relates to our actual energy usage.

I don't agree with any of your assertions, including the nonsense on PV insurance making PV power worthless ($1000 per month for home power PV).  Your signal to noise ratio is below my tolerance limit, I won't respond further.

This is not my assertions, if you read the article you'll see that it was written by an attorney, on her blog whom is very keen on solar.

So, Bruce...the point of this forum and the resultant discussions is an attempt for us all to exchange our knowledge, and drill down to what is the best for each of our own situations.....one size doesn't fit all....and I am not proposing that it does.

My point is consider all the cause and effect.

Lloyd

[Lloyd]

Bank costs.


things to consider every time you increase the voltage you drop the amp load by almost half that's good, you increase the real estate required the house the bank, and the cost by dbl...that's some thing to consider, As you increase the initial cost you have to increase the fail safes to protect your investment...that's something to consider.

yes Bruce...I do understand

Llyod, you don't seem to realize you can reduce the AH of batteries of a 48V bank by 3/4 and still have the same power storage capacity as a 12V bank. You  pay about the same yearly costs for the same power storage capacity of bank, regardless of voltage or design service life of batteries.  That's consistent with conventional wisdom on wet lead acid batteries and the Windsun battery info article you posted, your statements are not.

Lloyd

[mbryner]

Lloyd,

I've missed the forum for the past day, so there was a lot to read.

Please remember, in a battery bank you can't go by amp-hours unless you're comparing the same voltage battery banks.   Like Bob says, you're comparing apples to oranges.   Amp-hours works great when you're at Walmart buying a battery for your truck:  they're all 12 V batteries.

You have to use kwh when comparing battery banks of different voltages.   Using the values in your last post as an example:

12 v bank:   6 batteries = 8.64 kwh     = $61.80 per kwh
24 v bank:   4 batteries = 5.76 kwh     = $61.80 per kwh
48 v bank:   8 batteries = 11.52 kwh    = $61.80 per kwh

See, cost per kwh is the same, unless you are getting a discount by buying batteries in volume.    The total potential stored energy in the banks is proportional to the number of batteries in the bank, not the voltage configuration of the bank.

[mobile_bob]

Marcus boiled it down to the core issue, in my opinion

also

a few years back i set out and got the best prices i could find for all the popular flooded lead acid batteries

when i took into account all the factors, cost, amp/hrs, cycle life, etc it was amazing that there was almost no
difference per kwatt/hr between the highest quality and the lowest

you pay more for a high quality battery and get my cycles, so it all comes out in the wash

it was as if there was a conspiracy or something

on topic

there are other factors too

taking the same battery that make up a 12volt bank, and using it for 48 provides more kwatt/hrs or it will provide for shallower discharges
which lead to longer lifespan in more cycles, here the relationship is not linear and the advantage in lifespan tips to the use of 48volts, "if"

you have a means of efficiently charging at the upper end of the charge cycle where battery efficiency is poorest, so there is no advantage
with 48 if you are burning fuel to do the charging, but is an advantage for solar where we don't pay for sunlight (at least not yet)

for me:

system voltage was determined by the ability to get the mx series exeltech inverter system, which was 48vdc
had the inverters been 24 or even 12volts that would have been my determining factor as the low cost of surplus
inverters was more than enough to offset the cost of a very large battery bank of the best quality batteries made.

once the voltage was set, then came the journey to determine the most efficient method of charging them, i got enough
solar to do the job, so i  was left to determine which voltage of generation provided the most kwatt/hr per gram of fuel
consumed.

this is where 12volts gets kicked to the curb in my opinion, there really isn't much available that will provide 250amps charging
at 14.4 volts dc, with efficiency over about 52-54% (ad copy notwithstanding), 24volt alternators are about the same, but
after much research and testing i found that i can reach close to 80% with my system at 28.8vdc that pretty put the last nail
in the 12volt coffin, and if as i suspect, my 48volt project x alternator clears the 80% efficiency ceiling there is no way i would
use or recommend a 12volt system. 

except as outlined for very specific applications like Lloyd's boat, or a cabin?

its only after taking all the factors into consideration that for me a 48 volt dc system is the only way to go

conclusion:

if you have to burn fuel to charge your battery bank, 48volt  system will pay for the battery bank in fuel savings
over a 12volt system of similar kwatt/hr capacity. (or at least it should if the system is setup right)

bob g

[Lloyd]

Firsts things first.

I am not advocating one voltage over another.

Second, ohms law says it doesn't matter...watts or amps it is a metric only, dependent on voltage.

Amp hr or kwh(just a different way to measure) its' the same if you ascribe to ohms law..to which I do.

Bat banks are marked in amp hrs, not watt hrs.

Bat banks are storage only, not watts or amps consumed, or regenerated.



Now that we got that settled...my only point is the initial investment, over amortization.

How much does a 12v bank for storage cost?

How much does a 24v bank for storage cost?

How much does a 48v bank for storage cost?

What is the 24 hr watt/amp load? no matter what bank voltage you choose.

How much fuel does it cost to replenish that 24 hr watt/amp hr load?


Fuel is the cost of equipment and amortization, no matter the voltage.

Fuel equals, a diesel/gas/propane gen set dc/ac, acquisition costs, repair and maintenance, plus the actual fuel burned replenishing the watts/amp hrs burned.

Fuel can be a solar PV system, acquisition costs, repair and maintenance.

All associated systems require loss prevention costs. Insurance, security.....

All of the above are independent of the nominal voltage of the system of your choice.



Now what are the savings of one voltage over the other .

Efficiency in regenerative time?

Increased cost of the lower voltage, due to VD..which equates to bigger conductors, and associated?



Now just as an example we run a 12volt(i used this voltage bc I'm crusty) a little perky\cat/volvo, spinning a 250 amp alt..regenerating 220 amps/2640watts at 14volts back into a bank in one hour, on 1 liter of diesel $2.45 per gal= 0.264172051 x 2.45=$0.65 cents.

220amps over 24 hrs = 9.16 amps burned every hr non stop for 24 hrs. Now we have to amortize the equipment? Is it  a dc or ac gen, does it include solar, how big should the bat bank be.

How many amps/watts are you burning over 24 hours?
How many are burning more then 220 amps in 24 hrs? remember ohms law do the math and convert to 12 volts so that we may compare apples to apples.

How much do our system really costs.

Remember omhs law..it doesn't matter what the nominal voltage of the system is, we burned the same in a 24 hr period, almost, bc there may be some efficiency at the higher voltage...but the metric is going to be small on a 24 hr period.

In the end a bat bank will increase the system costs the higher you go in voltage....if you use a well tested bat manufacture...the higher voltage may increase the storage value...but if that exceeds the required storage between regeneration...that's a loss not a gain.

Since there is no redundancy in a single series string, we have to add redundancy, no matter the nominal voltage, what is the cost of this redundancy?


Lloyd