# upgrading the battery bank



## hoofinitnorth (Oct 18, 2006)

We're in Southcentral Alaska.

We need longer use time between charges in the winter when we don't get a lot of sunlight so we want/need to upgrade the battery bank but are having trouble finding $$ to do it.

We currently have 4 Rolls/Surrette batteries (I think they are 1000AH but not sure) in a 24v configuration, a 7500w Outback stacked inverter, a 6KW gennie with authostart as back-up and charger, and all that jazz. Just running the gennie way too much for our likes in the winter.

Ideas on what we can do? We hear to add more batteries (either 8 in 24v or 8 in 48v - which is better and why? I forget!) we have to replace all batteries at once if they are over a year old. If that's the case, then what am I realistically going to have to spend or is there some other way to do this cheaper? We have been quoted around $1,000/battery installed (consistent with the original installer's costs) so 8 could be as high as $8,000!!! GoodNESS!

Ideas? Experience? Warnings?

I don't think we have used but still good golf-cart batteries available to us...


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## mightybooboo (Feb 10, 2004)

One thing you can do is add a new bank,then just switch between the 2.Dont have to worry about matching ages then.

The higher your voltage,the smaller the wires you can use.

Trojan L-16HC's were 225.00-275.00 each last I checked,6 volt,420 amp hours.

BooBoo :gromit:


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## Jim-mi (May 15, 2002)

Yes a second bat bank would be one way to go.

BUT . . .Beware that if using such as a Trojan L16 that you will have two different charging rates.
Those wonderfull Surettes are known to be hard to get the last 5-10% (charging) into the bat.
So if you were charging them (the Surettes and the Trojans) together you would stand a good chance of over cooking the Trojans.
Sollution; A good Bat switch--- 1 _ 2 _ both positions.
Charge and use both bats seperately.
Get good metering for both ( TriMetric ? )

Manual switching yes . . . . .much cheaper that way.

Sollution #2 . . . .reduce your load. (to lessen gen run time)


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## Runners (Nov 6, 2003)

Solving one problem might lead to another...

To me, the bottom line consideration would be the life of the battery(s). For instance...

2 24v strings might sound good, but if they're hooked up to the same inverter, you'd probably keep them both connected in parallel. If you only use one string at a time, then the tendency of deeper cycling would wear out the string faster. 

On the other hand, I'd go ahead and hit the older string first, keeping the new string 100% charged/equalized, ready to go - just shallow cycle it. In a half-dozen years or so, save whatever units you can out of the old string - and add another new string, migrate the shallow cycled string to the heavy load position. Just a thought...

I'm glad you covered the charge rate / equalization concerns! Mixing types or old/new units in a string eventually kills everything!

Some of the back issues of HP magaqzine - Richard Perez addressed the woes of mixing types pretty good!


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## WisJim (Jan 14, 2004)

If you switch to a different battery voltage you will need to switch inverters, too.


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## hoofinitnorth (Oct 18, 2006)

Thanks for the ideas! Keep 'em comin'!


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## hoofinitnorth (Oct 18, 2006)

Bump...

Still looking for guidance on my original questions...


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## idahodave (Jan 20, 2005)

Adding more battery storage may save on the number of charge periods, but make each one longer in order to fully recharge, so the net saving could be small. Is the battery bank large enough to cover a couple of days without charging?

Reduce the load as much as possible, if you haven't done that already. 

Try to schedule generator runs to be coincident with larger demand periods. If it's been cloudy I run the genny to charge while we shower to keep the pump and bathroom lights from drawing out of the battery.

Consider a small 24 vdc generator for recharge, it should be more efficient than running a 6.5kw genny lightly loaded. 

How much of your daily need does the array provide during sunny days? If you don't meet the daily demand when the sun is out, add more panels.


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## hoofinitnorth (Oct 18, 2006)

*idahodave* - no the bank was advertised to give us 3-4 days between charges but it is not even CLOSE in winter when we get no sun. Obviously the seller/installer didn't know his stuff because he couldn't even give us basic equations for calculating loads & usage to figure out how much battery power we'd need to go 3-4 days. At best we make it 24 hours between charges in winter (at worst it can be as little as 12 hours)!!! Now that is only about 3 months of the year at most when we have a bunch of cloudy, cold days, but that is UNACCEPTABLE given what we paid for the system and were supposed to get. We told him up-front that while we would conserve energy, this house would have to run like any other "normal house" with "normal loads" for its size and intended use (which we described to him and let him see first) for future marketability.

Yes, we're aware of the longer charging periods, which do not bother us but may push us to buying a bigger generator since I personally think it is undersized for our needs.

My husband does what you suggest as well - use your big appliances while the gennie is already running. The only trouble with that is microwave, which are notoriously problematic for gennie use and you don't run for long periods of time anyway.

We actually have more panels than our system can handle in the summer, as we've discovered - another issue the installer didn't anticipate. We have to add another MX-60 to use all the power we get on sunny summer days!

We think we can make the basic upgrades without the battery & gennie stuff for under $1,000 including install but the batteries are the biggie. Are the figures I mentioned earlier really reliable? Are there other sources or other types of batteries I can get cheaper somewhere?


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## hoofinitnorth (Oct 18, 2006)

*WisJim* - Our inverter can handle a different voltage, just needs to be reprogrammed/set-up for the new voltage. Or so we've been told...


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## Jim-mi (May 15, 2002)

Hoofing, Your last post shure has me wondering.

Your first post said you have 7k of Outback (two stacked).
Outback does not make a multi input voltage inverter.
Its one or the other.---24 or 48.

I shure dislike my stupid microwave. It says 600 watts
That might be cooking power, but the damn thing takes 1100 watts input. . . . . . .thats ugly.
So it sits on the counter__only__ used when theres enough sun or wind.
I really ought to throw it out.

If you could change your habbits and NOT use the micro your batterys would love you.


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## hoofinitnorth (Oct 18, 2006)

*Jim-mi* - The seller/installer told us we could just change the software on the inverter when/if we wanted to change the battery bank (which will also require different wiring). Another installer told us that is not so but that there are ways around replacing the entire inverter...

We rarely use the MW, mostly use the propane oven/range.


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## justmyluk (Apr 28, 2005)

Where are your batteries located? Are they in an insulated building where they stay warm in the cold winter months or are they in an uninsulated building/ battery box? Cold weather will suck the life AND charge out of good batteries in just a very short time.


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## Jim-mi (May 15, 2002)

Hate to tell ya but that guy is blowing smoke at ya.
(I'm a seller\installer)


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## tnhomestead (Jul 23, 2006)

Have you tested the batteries? I can go 2 plus days with 1/4 the battery power you have! A good 24 vdc gen setup will be easier to run, can build it yourself cheep too, or buy one for about a grand.(OUCH)


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## idahodave (Jan 20, 2005)

It's too bad that you can't (or shouldn't) add a second string in parallel with the first, and not have to think about switching between banks. 

I'd drop a note to Rolls and ask their advice about paralleling another string to the one you have. If you have a TriMetric include the "Cumulative Battery Amp Hours" which might be useful information to Rolls. 

Maybe if you ran on the new string for a year it would better match the older one so they could be paralleled.


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## TechGuy (Oct 25, 2006)

hoofinitnorth said:


> *Jim-mi* - The seller/installer told us we could just change the software on the inverter when/if we wanted to change the battery bank (which will also require different wiring). Another installer told us that is not so but that there are ways around replacing the entire inverter...


Its the transformer that really determines the operating voltage of the inverter. A transformer is used to boost the voltage up to the AC output level. I can't imagine that a simple software upgrade would permit the inverter to operate at a different voltage (at least while maintaining the same level of efficiently). Its possible that the transform primary might be wired with multiple taps to handle different input voltages, but this would probably require some manual reconfiguration to use a different voltage.

Your best bet would be to find the manual that came with the inverter. If you can't find it. Search on the internet for it. In the worst case you should be able to contact the manufacture and ask them if can be reconfigured for a different voltage. Your best bet is probably to keep using the existing operating voltage.


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## idahodave (Jan 20, 2005)

Possibly confused the charge controller and inverter? A MX-60 will work for different system voltages.


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## Gunga (Dec 17, 2005)

Have you looked into wind or micro hydro units? When it's dark or cloudy they could charge your batteries.


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## hoofinitnorth (Oct 18, 2006)

*justmyluk* - yes, they are in a separate heated building in an insulated box with a built-in vent that comes on when the batteries are gassing.

*Jim-mi* - we know a lot of what this guy told us was BS - went to court and proved it. Now there's a nice record of his dealings in detail for others in the area to read.

*tnhomestead* - yes, batteries all test out fine and Surette/Rolls says that is about right for our loads. Remember, we have a fairly large house in Alaska with all modern appliances (although they are energy savers they still suck power). Summer is not a problem at all unless we have several days of clouds. The problem here is that we don't get enough direct sunlight for a few months of winter to get the batteries really healthy so when they get low the gennie comes on and batteries hate gennies vs. solar for charging so they get worse and worse until the sun comes back. When we can do a really good corrective equalization things do improve but it's tough until then. I'm confused by your suggestion though - we already have a 24vdc genset installed...

*idahodave* - what's a TriMetric? Will contact Rolls/Surette. Good suggestion on running another string for a while to "age them" to match existing string. Would need some way to automatically switch between banks though... I do have the manual and have read it several times but it's not set up for our specific system - has a lot of "if you have this then that" and if you don't have all the technical knowledge to identify the "this" then you don't know the "that"!  I know we have some sort of transformer that the 2nd installer we consulted for maintenance & court case said we could make some changes here and there but it will cost us a lot more. *sigh* I know the difference between the MX60 and the inverter but good thought on that possibility.

*Gunga* - hydro isn't an option here but we are looking at wind. The trouble is the ugly and costly tower we'd have to stare at and high expense of guy wires to secure it (in addition to the ugly solar tracker we already stare at). Still would need to upgrade batteries though!

Keep the ideas coming - they're making us think!


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## idahodave (Jan 20, 2005)

A TriMetric is a 4" square panel that displays voltage and current. It totals ampere hours used from the battery bank, and offsets them with charge currents. It will also display percentage of bank charge and a few other parameters. 

One of the other parameters is a total of ampere hours supplied by the battery bank. The total number can be used to determine how much the batteries have been used. Handy little thing to have. I'm surprised that a system as large as yours doesn't have one.

Is your generator really 24 vdc or is it 120 vac and the inverters act as chargers when it's running? 

A small 24 vdc genny was suggested so you wouldn't have to run the big genny all day to finish charging the battery bank. Your generator should charge that bank as well as the array does if you let it run long enough.


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## Jim-mi (May 15, 2002)

Here is yet another confusion factor.
No TriMetric . . . . . . . . .
What do you have for your (fuel gage) battery monitering . .?
An "E meter"--a "Link 10" . . . or what .?

I'm sorry you feel that way about "that ugly tower" . . . .

When I look at my windturbines up on their towers (three of them) all I do is smile . . . . . .knowing that I'm harnessing some of the wind energy to power my place.

guess I better quit replying on this thread


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## hoofinitnorth (Oct 18, 2006)

*idahodave* - Ah, the other installer that would do any maintenance, further installs, etc. suggested something like a TriMetric too. He said what we have now is like a gas tank with no gauge. 

Not sure about the 24vdc vs 120vac. How would I know? I think the gen does both AC & DC... Not sure though. I was thinking of the batteries on the 24vdc comment earlier, sorry about that... The gennie we have now is only 6KW and at max power (about 80% or around 4.5K), it takes several hours just to get the batteries up to 29vdc to charge them for 4 hours. When everything works ok and there is no sunlight at all on the tracker, the gennie takes about 6-7 hours to complete a charge cycle. It does charge fine but the power isn't as "clean" so the batteries don't like it as much as the array.

*Jim-mi* - please don't stop posting here. The issue of the looks is less of a deal to us than it is to our neighbors or potential buyers. The solar tracker first gets "ew what is that thing" and then "oh neat!"


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## idahodave (Jan 20, 2005)

I think you should call back the other installer and have him add a TriMetric to your system. Have him teach you how to use it.

A bigger genny may not charge any faster. Chances are good that yours is a 120 vac output and the inverters act as chargers when it's running. The inverter charge rate determines how long it will take to recharge. The genny also supplies 120 vac to the house during charge periods. 


I need a little help with stacked Outbacks (when stacked do both act as chargers? I'm a Xantrex user) but assume two of them may charge at about 160 amps max or a little over 4kw into the battery. That would leave about 2 kw to run the house when the gennys on and just starting to charge a discharged battery. The charge rate will taper off as the batteries charge so there will be more generator power left for the house as the process continues. A 6-7 hour charge time is not out of line.


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## justmyluk (Apr 28, 2005)

Jim-mi said:


> I'm sorry you feel that way about "that ugly tower" . . . .
> 
> When I look at my windturbines up on their towers (three of them) all I do is smile . . . . . .knowing that I'm harnessing some of the wind energy to power my place.
> 
> guess I better quit replying on this thread


Jim-mi...I agree with you. I too am a firm believer in adding wind power to a solar system. I have a small system hooked up down in my shop. (3 solar panels, 2 12v deep cycle batteries, charge controller, 1200w inverter, small wind turbin, and diversion load) I use it to run the lights in my shop for now but as I add to the system, I'm going to run a line to the house and use it for back up when the power goes out. Who knows, I may take one room at a time and convert it to all solar/wind as my system grows.

I have the wind generator hooked up to a diversion load for when the batteries reach full charge (an old sealed beam spot light that draws 10 amps). It's a good feeling to look down at the building at night and see that light going on and off. I know that even WITHOUT the sun, my batteries are at a full charge and the wind turbin is still producing more...

My small wind turbin is only on a 20 foot tower that I attached to the side of my building on a 1" pipe, attached to a 4x4 post (I didn't need any guide wires) I painted it John Deer colors and it looks like a decorative lawn ornament (with 5 foot blades). My neighbors love it...


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