Author Topic: OFF GRID POWER; various thoughts on...  (Read 556697 times)

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Offline hpinson

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Re: OFF GRID POWER; various thoughts on...
« Reply #1025 on: June 21, 2012, 10:34:20 AM »
I had been looking at the Surrette, because of their excellent warrenty.  I had a vendor who I trust tell me just before I ordered that he liked the Surrette warrenty but not the product.  I guess they have had some unexpected failures. I went with another battery maker-- Deka... nowhere near the warrenty as the Surrette though... some other alternatives are Sun Xtender, Interstate, and Trojan. I think they all ship from the factory to ensure you are getting a fresh battery.  Mine were AGM.

Offline Squirl

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Re: OFF GRID POWER; various thoughts on...
« Reply #1026 on: June 21, 2012, 10:41:14 AM »
1200 amp hours with 215 hour GCBs would be six strings.  From what I read, it would be difficult to keep those evenly charged.  I have not seen any hard data on how much extra strings can decrease the longevity of the bank.  The recommended maximum in most solar books and publications is three strings.  That is why you see very low voltage high amperage batteries.  Three sets of 400 amp hour batteries would be within most recommendations.  Although the most publications recommend as little strings as possible, it is not practical to have just one.  It can lead to charging difficulties if you more than one input and if you have one battery go bad, you lose all power.

If adding batteries it is also recommended to replace them all at once.  The shortened life and decreased depth of the old batteries will shorten the life and performance of the new ones.

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #1027 on: June 21, 2012, 10:45:55 AM »
Quote
current usage can be 1700-1900 watt hours per day according to my charge controller

Not quite the same as actual use,as the CC amount going into the batteries is accounting for losses in the system. Meaning that CC data number is larger than the calculated, item by item x hours a day/week, calculated totals. It also is measuring the float amount of power.

With numbers like that (large) perhaps the total system needs some reassessment. Like is the electric fridge efficient enough for use with a PV system? Should the battery bank be 24 VDC? Perhaps a solar tracker is required to get more juice out of the sun hours?


The ideal battery bank would be a series string of 2 volt cells; nothing in parallel.  And you buy a spare  as windpower did.

I also believe that connecting the series strings to buss bars is much better than making the parallel connections with cables. OJH does have copper buss bars IIRC.

Just because something has been done and has not failed, doesn’t mean it is good design.

Offline Squirl

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Re: OFF GRID POWER; various thoughts on...
« Reply #1028 on: June 21, 2012, 10:48:30 AM »
Trojan RE series also has up to a 7 year warranty too.
http://lib.store.yahoo.net/lib/wind-sun/Trojan-RE-Warranty.pdf

I don't know how it stacks up to a Surrette, who have a great reputation too.
I was looking into them because Trojan batteries have a good distribution network and I may be able to find them locally without paying for shipping.

Offline OlJarhead

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Re: OFF GRID POWER; various thoughts on...
« Reply #1029 on: June 21, 2012, 10:54:47 AM »
Good points and info on the CC readings.  I wasn't sure about that but it makes sense.

My neighbor has a 1000AH caterpillar battery bank and ~500watts of solar on a tracker and it seems to do the trick except in the winter where he must run a generator every weekend to get the bank back above 70%.  So, my thought was that my 615 watts of solar and 880AH of batteries would at least, according to my original calcs, do the trick.

SO far, if there is sun, the batteries go back to 100% daily and I've used the system in the winter with little to no sun and the bank appears to do 'ok' in that it's still above 50% in the morning (often above 80%) but I'd planned the system to do that in 3 days not 1.

My thought is that I failed to calc based on winter numbers rather then a yearly average.  Using winter numbers means the system will provide enough power in the winter and excess in the summer -- which is fine by me!

So, I'm back to the drawing board. 

I'll do more research on usage to try to get the system tailored correctly but I'm pretty certain I'll need to at least bump up to 1200AH and 820watts of charging power to ensure I have enough power to use the system on cloudy winter days without worrying.

Offline OlJarhead

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Re: OFF GRID POWER; various thoughts on...
« Reply #1030 on: June 21, 2012, 10:56:28 AM »
On a side note, the system isn't as bad as it might sound  d* it's just that I'm a worry wart!  d*

I run the fridge non-stop when I am there and last year ran it all summer (24x7) without drawing the bank down too far at all and that was before the addition of two more batteries to go from 660ah to 880ah.

I just don't think I can run both the fridge and freezer like that and want to.

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #1031 on: June 21, 2012, 11:08:41 AM »
Just because something has been done and has not failed, doesn’t mean it is good design.

Offline OlJarhead

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Re: OFF GRID POWER; various thoughts on...
« Reply #1032 on: June 21, 2012, 11:39:42 AM »
Dave Sparks has one of these...

http://www.stecasolar.com/index.php?Gefriertruhe_en

My fridge isn't a problem -- it uses less power then one might imagine.  It's energy star rated and has no freezer -- I think I figured it was using 27-35 watts per hour to run...but I'd have to go back and check.

I also have a freezer that doesn't use very much either and I can run both at the same time, I just have no need.  However I haven't tested the system enough yet.

As for the fridge in the link, I'd love one, but the price was too much for me when I put my system together....but again, mine does fine for what I use it for.  My biggest worry, frankly, is that if I wanted to spend a few months at the cabin in the fall or spring that I'd not have enough charging power and battery power to run the system without using a generator and I hate using the genny! lol.


Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #1033 on: June 21, 2012, 01:34:36 PM »
How about 6 of these Trojans...

http://www.trojanbatteryre.com/PDF/datasheets/L16RE2V_TrojanRE_Data_Sheets.pdf

$340 each plus freight which might not be all that much. Give 'em a call.
http://store.thesolarbiz.com/online/ProductDesc.aspx?code=TRO-50000&type=0&eq=&desc=Trojan-L16RE-2V&key=it

They are not 2 volt cells, they are 2 volt batteries; the three cells are internally connected to provide 2 volts instead of 6 volts. Not as simple as a pure 2 volt cell (you still have three cells to water in each unit...), but very cost effective for Trojans production. Six of them, nice simple with potentially neat wiring; 12 volts and 1110 amp hours @ 20 hour rate. heavy though at 120 lbs; but ya only have to move them once. Twice if you count when they get replaced some years down the road.   :)  With care I bet they could give you ten years easy.  Wonder what Dave thinks of that?  ???
« Last Edit: June 21, 2012, 02:27:48 PM by MountainDon »
Just because something has been done and has not failed, doesn’t mean it is good design.

Offline alex trent

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Re: OFF GRID POWER; various thoughts on...
« Reply #1034 on: June 24, 2012, 05:14:00 AM »
This is posted in another thread, but is a separate issue. Any thoughts?

Trojan AGM 31 battery

Iota 55 AMP smart charger

So on the first go round with the new battery...after 4 hours on the charger still in the bulk stage and battery voltage at the inverter after a 3 hours off charger and no load except inverter is 12.5 V, which for AGM I read as about 75%.  When I got the volt reading off the battery when first bought it was 12.3 volts (on inverter meter)...which is 50%. Sounds like something is screwed up...any ideas? Could it be my generator which is not true sine wave?  I have read things about how they do not supply the right current for charging at full volume.  On the other hand, Iota is one of the charger that is supposed to be able to deal with that.

I have the connections to the inverter connected to the same posts as the charger.  Remain on when charging but the inverter is turned off.  I assume this is not the problem as the inverter is not doing anything when off.
« Last Edit: July 03, 2012, 03:11:42 AM by alextrent »

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #1035 on: June 24, 2012, 01:20:07 PM »
Is the voltage meter known to be accurate for certain?


Is it THIS battery?
Just because something has been done and has not failed, doesn’t mean it is good design.

Offline alex trent

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Re: OFF GRID POWER; various thoughts on...
« Reply #1036 on: June 24, 2012, 03:32:14 PM »
I would not vouch for the meter on the inverter.  In use with my regular batteries...looked to be reading a bit low....0.4 V.  This is based on the alarm going off and the shutdown which were different with when the even was to happen and the meter reading.

I am going to invest in a decent meter when in the States this week.

I ran it another 3 hours today and never go to float.  Started ar 12,3 V after overnight rest and 4 hours one the charger yesterday. . Did the slow blink all the time.,..no fast.  When I shut charger down and waited 2 hours I had about 12.6 5..about 65%.

The Iota instructions say to disconnect the positive battery/inverter connection before charging which i did and did not have enough time to see if that make a difference. That will be a pain but will do it if i have to to get charge.

Yes that is the exact battery.

Offline OlJarhead

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Re: OFF GRID POWER; various thoughts on...
« Reply #1037 on: June 24, 2012, 04:04:08 PM »
OK. I get it ;)

I FINALLY went and picked up a Specific Gravity reader (Hygrometer?  Hydrometer?) and checked my batteries.

After about 12 hours of use (arrived around 5:30PM or 6PM and checked at 7:30am) the SG showed the batteries at about 95% of charge after running the fridge all night and using lights for about 3 1/2 hours.

After 24hrs the 'Kill-a-watt' (or whatever it's called) meter I brought along showed 820 watt hours of power used AFTER the inverter.

This morning at 7:30am the batteries showed about 90% of charge (didn't get much charging done in the rain Saturday but did get some with the occasional sunny period and the MPPT controller making the best of cloudy weather).

So, perhaps I was being a bit peranoid after all.  I do need to equalize the batteries (never done completely) so plan to do it next trip and take readings of the SG while doing so (Trojan has a section on doing just that).

All in all I didn't see anything way out of wack (usually I read within 0.001 between cells) until the fridge kicked on while checking this morning and readings went a little crazy -- I figure you're probably supposed to kill the inverter and charger and check then but I was in a hurry and wanted to see what two days had done.

I know my readings weren't perfect but it appears at least for now, that I'm not using those batteries as heavily as I thought I was.

Incidentally the 820watt hours used in 24hrs reflects very close to what I had down in my solar/pv spreadsheet for just lights and fridge -- I actually had the fridge running slightly more but suspect that since I keep it closed most of the time it probably uses less energy then advertised (they probably base it on more opening of the door throughout the day then I do).

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #1038 on: June 24, 2012, 04:50:14 PM »

I FINALLY went and picked up a Specific Gravity reader (Hygrometer?  Hydrometer?) and checked my batteries.


 :) :)    [cool] [cool]   c* c*   8) 8) 
hydrometer for batteries and things like wine making (different range for wine  :D )

hygrometer for relative humidity 
Just because something has been done and has not failed, doesn’t mean it is good design.

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #1039 on: June 24, 2012, 04:52:42 PM »
alex

I'd get a good meter or calibrate yours against a good one.

If the charger won't go to float with that battery, put it on another good battery and see what happens there. (Jeep?) If it goes into float on the other battery then the AGM you bought would seem to have a problem.
Just because something has been done and has not failed, doesn’t mean it is good design.

Offline alex trent

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Re: OFF GRID POWER; various thoughts on...
« Reply #1040 on: June 24, 2012, 05:06:47 PM »
Great idea on trying it on a known good battery

I have a ggod 1 yr. old in the jeep.

I definitely am going to invest in a meter...got a suggestion for an EZ to use one?

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #1041 on: June 24, 2012, 05:21:49 PM »
An auto-ranging meter is nice, no need to set the dial to the range to be measured; helps eliminate errors. Plug in probes rather than hard wired ones.

I have an Amprobe I leave at the cabin... not sure of the model nbr but I think it's a 520 or a 530   ???   I paid something like $50 a few years ago. I also have a better, older Fluke that I keep at home. The Amprobe matches the Fluke pretty much to within a couple hundredths. I think Amprobe is actually owned by Fluke.
« Last Edit: June 24, 2012, 06:13:55 PM by MountainDon »
Just because something has been done and has not failed, doesn’t mean it is good design.

Offline alex trent

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Re: OFF GRID POWER; various thoughts on...
« Reply #1042 on: July 03, 2012, 03:31:57 AM »
See post 1035 for the background on this.

My reading and first call to Iota tech uncovers some strange stuff.

On stage one (bulk)...lasts for 15 minutes to 4 hours...that sounds OK,

On stage two (absorption) "Stage two: Absorption stage, will remain on for a total of 8 hours.  After the 8 hours then it switches to the Float stage" So what I am reading is that this stage is on for 8 hours, no matter what the battery level is.  I assume the charge rate is reduced to fit the required amps into 8 hours.  In my case, this means at 50% charge when starting and stage 1 putting in about 20 amps, the charger in stage 2 is putting in the remaining 30 amps over 8 hours.....0r about 4 amps per hour.

This explains the charger staying on stage 2 even when little charge is needed and why the battery is only charged to 75% when I cut the time short.

Seems screwed up to me. i would think a "smart charger" would send in the max safe about during stage 2 and cut this time short.  I believe even 15 amps in stage 2 is fine.  This would mean that the battery would be charged in 3 hours not 8.

My thinking is that a single battery as I now have is the source of the problem and if I had 3 or 4 batteries and needed 200 AH, the 8 hour charge would not seem that bad???  Even then it sounds a bit weird.

Thoughts on my analysis and anything i can do.  Running the genset for 8 hours to put in 50 amps is silly.

Offline UK4X4

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Re: OFF GRID POWER; various thoughts on...
« Reply #1043 on: July 03, 2012, 05:14:01 AM »
I think I have a similar issue in my trailer, the two batteries are only 160am/hour and even after 7 hours of the generator they are not full.

The charger / convertor says its 100amps.....but I'm certainly not getting those results.

I will be probably adding a decent charger from Xantrex and some solar power to do the topping up.
as I'll be going from a 160a/h to 440amp and the present charger certainly won't cope



Offline alex trent

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Re: OFF GRID POWER; various thoughts on...
« Reply #1044 on: July 03, 2012, 08:35:18 AM »
The second reply I got from Iota kind of explains it. BTW, they reply right away and do a good job...although this answer is not what I want to hear.

It appears that for a small bank (in this case 1 battery) this is not the right charger. It likely would be for a larger bank and I will try it when I get two more batteries to bring me to 3 and330 AH total.  That means at 50% charge when I  crank up the generator I will need 165 amps and, simply put..... if I understand the Iota reply..... will make the charger put out more amps so the whole thing is more efficient. Right now, it does not sense a big load, so cuts back. He differentiated this Iota as a "power supply", not a "forced amp charger"...seems for me I need the latter but we shall see when i get my other batteries.  I would rather sacrifice some battery life and charge faster than have to run the genset 2x as long to put in 100 amps or so.

any body got any thoughts on this...am I correct or did i misunderstand the Iota specs and what the tech guy says.

Offline alex trent

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Re: OFF GRID POWER; various thoughts on...
« Reply #1045 on: July 05, 2012, 04:15:20 AM »
I thought this might be useful as it can be a real confuser!  This bad chart on SOC and volts made me pull my hair out for a while. On the good side, caused me to do a lot of reading about batteries and charging..

Below is a note I sent to the Iota guy who I had questions to about the slow rate of charge...which turned out to be not zoo slow after all.  Glad my notes were calm and nice!

I thought I would pass this on as it may help explain some of my "problem" and might be of help down the road to someone else.

I got a SOC by voltage off the net. Came from a good site with lots of detailed info. Says 75% is 12.60 and 50% is 12.30. So I am looking at my battery after 4 hours of charging and seeing 75%  (12.6 v) and that is confusing and makes it look like the charger is very slow (slower than safe needs to be)..

I now see from every other SOC chart, including the one Trojan supplies for my batteries that 75% is 12.35  and 50% is 12.10...and the 12.6v that I thought was 75% is actually 90%. Everything working fine!

That info, which appears faulty is the cause of the concern about the rate of charge and my questions to you.



The other thing I found useful was that with my set up it will the me about as long to go from 90% to 100% charge as it takes me to go from 60% to 90%...so to save running the genet...I just stop at 90% and go to 100% every 10 times or so for battery health.

Offline rsbhunter

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Re: OFF GRID POWER; various thoughts on...
« Reply #1046 on: July 11, 2012, 07:46:30 AM »
Have been looking into the nickle-iron batteries....They are being called a "lifetime" battery, supposed to last 25 years???? I'm in the process of getting my land excavated, tree roots dug out, going to build the one story cabin (600 SF) . I have already bought 2350 watts in panels, a Outback VFX 3624, and a Midnight 6 gang combiner box...i plan on having a solar/storage shed  approx. 30' -50'   from the cabin. What are some recommendations for battery bank size? I am honestly looking at the iron/nickle batteries....in the 400 Ah 24 volt (at20hr) set up...... But don't want more battery than what the panel can produce in around 4-6 hour range...i do have a 3.5K genset, and plan to find a 4-6K either propane, or diesel unit for a permanet unit...I'm at 10'000ft in S. Colorado.....supposedly real good solar expousure...Glad to see this posting area, i too believe that there needs a seperate "off grid" section.....Alot of us out here, and more everyday....and we are buying the "countryplans.com    plans....rsbhunter

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #1047 on: July 12, 2012, 04:40:02 PM »
I think Edison developed nickle iron batteries for the early electric vehicles.  That's about all I know about them though.  How do their charging requirements match with lead-acid batteries?

As for the size of the battery bank that can be hard to say as there is a wide disparity in what people expect from their off grid systems. My personal experience has been that use will grow; the only question is by how much.  We've been fortunate; my estimates of what battery capacity was needed has worked out well. I used the Off Grid sizing tool that is available...   http://countryplans.com/smf/index.php?topic=8192.0

System failures are frequently caused by too small a battery bank, and/or too small a PV array.  Be careful with the estimating of the power needs (or wants). It can be done if time is taken.

A generator can be handy but they need maintenance. I seem to run our generator mostly just to keep the engine in good shape, rust free, the fuel fresh, etc, than I actually need it for charging the batteries. We can even equalize the batteries using solar power if we plan it right.
Just because something has been done and has not failed, doesn’t mean it is good design.

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #1048 on: July 12, 2012, 05:06:39 PM »
An observation. The daytime temperatures have been reaching 88 at the cabin for a couple of weeks. It doesn't stay that high for too long; maybe 84 by noon, hits 88 between 2 and 3 PM and then falls to below 80 by 6 or 7 PM.

The battery electrolyte is now at a reasonably constant 65 F degrees. I wonder how high it will get by mid August?  Nights are still cool; in the 50's.
Just because something has been done and has not failed, doesn’t mean it is good design.

Offline Cowboy Billy

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Re: OFF GRID POWER; various thoughts on...
« Reply #1049 on: July 13, 2012, 06:26:51 AM »
Other than weight which in no problem for me. I like the one big battery approach. No parallel strings to worry about. All the connections for the battery are sealed so I don't have to worry about bad connections and have to be cleaning connections. When I test SOC with a hydrometer I only have one 24v battery to check not two or more strings of battery's. It takes up a smaller area than multiple battery's. And forklift battery's are designed for heavy discharge and charge in a industrial setting so in my lighter use as the heart of my solar system it should last a long time.

We also found we could put a heavy duty light dimmer switch on a 6v battery charger and charge one cell at a time since the connections between cells are accessible. Which allows us to equalize the battery by just charging the low cells. Not by trying to charge the whole battery which over charges some cells and causes sulfation in them.

We started our system with a old very used 1094lb 804 amp/hr 20hr rated battery and ran that for five years until one cell went totally bad. We are going to send it out and have a new cell put in and use it in a secondary location.

Last december we decided to get a new battery. We wanted to use up some tax credits while they are still available. And wanted a new larger battery for our main system. But I am glad we started with a used battery as it really taught us battery maintenance and care. Trying to take care of a battery that was in bad shape when we got it.

We ended up getting a 1482 lb 1182 amp/hr 20 hr rated 24v battery for $3188 delivered. And are very happy with it.



I think the prices are very comparable to the equivalent amp/hr of a multi battery system. And you don't have buying connections for between the battery's.

GB price list. GB is the only place we found the prices online.

http://gbindustrialbattery.com/Forklift_Battery_Sizes_and_Specifications_Zone15.html

A 12v 1182 amp/hr 20 hr rated 735 lb battery is $1745. But you can check the price list for other sizes.

Billy

 

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