The 2 day reserve

mountainman · December 2019

I get full sun on the panels from 8-4.
Pv watts gives 4.7 hours for Dec at 62° from horizontal.
I'ved seen 50 amps With a 780 watt array * .77~ 600 *4.7 2828 wh a day.
If the sun leaves at 4 pm and it rains 2 days thats about 64 hours on the battery.
Slightly over 2.5 days
I use ~858 wh per day.
I did a 64 hour test ~ 2300 wh. From a 5 kwh battery
With a 2.3 kwh usage *1.2 l.A. efficiency 2760 needed to recharge.
About what my array can make in a day.
Does this system seem fairly balanced?

Estragon · December 2019

Getting to full or nearly so after 2 days no sun in Dec sounds pretty good to me.

My shadows are too long and days too short now for much production.

mountainman · December 2019

I'm in the middle of a 200 acre field I'm restoring a old farm house built in 1902
Im currently Living in a camper on solar
propane and occasionally generator.
Until I get the home livable.
From 4-5 pm Pines to the west shade the panels.
But by 4 the sun's so low I dont think I'm missing much production.
Im usually floating by noon any way.
Summers at my mounting property
Is a completely different situation
With trees everywhere
I get about 4 hours full sun on the panels in June. In Dec an hour or so from 3-4
Lots of generator time.

mike_s · December 2019

mountainman said:

Im usually floating by noon any way.
Summers at my mounting property
Is a completely different situation
With trees everywhere

Solar haiku (in spirit, anyway)?

Photowhit · December 2019

Sounds pretty good.

I just did a 4 day 'test' my self. No sun the last 4 days, I pushed about 3.5 kWhs back into my old'ish forklift battery (8yrs old) before I hit absorb, I'll likely reach what the charge controller considers full today. I'll need to equalize tomorrow to recover 1-2 kWhs of lost capacity.

mountainman · December 2019

Photowhit how does your charge controller consider the battery is full?

mountainman · December 2019

According to S.G. My cheapo cc will go into float prematurely.
Doesn't use end amps. Just timed absorb. I set the absorb time to 1℅ of battery amps ~2.5 hours.
After a couple over cast days I set float voltage to absorb ~2.47 per cell until SG rises to what I think is full.

Photowhit · December 2019

mountainman said:

Photowhit how does your charge controller consider the battery is full?

I jjust have mine set for 3 hours absorb, Midnite Classic's can be set for end amps, I just never set it up.

softdown · December 2019

2 day reserve this time of year would be a strong battery bank. I think a lot of our members are hitting up their generator on most days. This week-end is set to be the shortest days of the year. Though a minuscule difference than present.

KenMorgan · December 2019

here at fuji I have run up to 3 days with minimal production on a 600 a/h bank. My bank is large enough that it only brought me down to 69% so one good sunny day will bring me back up to 100% but I would like to equalize after that. my batteries are still fairly new at so I want to take care of them.... though I have been lusting over a 2000 a/h forklift battery I discovered on alibabba...I could run a week..or two with that thing and no sun

mountainman · December 2019

Seems ive read that fork lift Batteries rate a/h differently than GC. Where GC use 20 hour rate not sure about how fork lift rates there capacity. @Photowhit if you would how does a fork lift battery a/h rating compare to true deep cycle or GC. Also how do they compare dollars to kilowatt?

mountainman · December 2019

Here in nc We just had 3 days of rain and clouds with very little production.
Almost 90 hours on the 416 a/h GC batteries.
Soc around 40℅. 1.140
In just 1 day of 40f and clear skies brought
SG back to 1.230
By the end of the next cloud less day SG was up to 1.265.

BB. · December 2019

This thread has some information... And that (at the time), several brands of Forklift batteries (appeared to) dramatically overestimate their 20 Hour capacity numbers vs their 6 Hour * Fudge Factor conversion number(s).

https://forum.solar-electric.com/discussion/350920/forklift-batteries-publshed-capacity-vs-actual

-Bill

mike95490 · December 2019

"Usually Floating by noon means nothing" when it's cloudy !

Image: https://us.v-cdn.net/6024911/uploads/editor/nq/xynleiv2x29b.gif

When the sun comes out, my arrays really slam the batteries with about 60A ( 2 arrays, 2 controllers) and if I've not been keeping up with the generator, it can take 2 days to refill the 800ah bank.

We get a couple weeks like this every year

( NiFe - no sulfation or stratification issues )

Estragon · December 2019

Yep, during the 3 months of < 2hr/day average full sun equivalent around here, catching up with solar alone can't happen much.

mountainman · December 2019

August is the only time of the year that we have rain more than 3 days in a row.
Winters are normally sunny.
And about every 4 years we get a snow storm. 1" or 2" .

Photowhit · December 2019

mountainman said:

Seems ive read that fork lift Batteries rate a/h differently than GC. Where GC use 20 hour rate not sure about how fork lift rates there capacity. @Photowhit if you would how does a fork lift battery a/h rating compare to true deep cycle or GC. Also how do they compare dollars to kilowatt?

I'm currently 8 years in on a GB 12-85-13 rated 510ah 6hr rate 804ah 20hr rate. GB over rates these batteries in the 20hr rate. A more correct estimate would be 1.3x the 6 hr rate or around 660ah 20hr rate.

My cost was $2525 delivered, built with 2 flags instead off cords. I've since seen someone have all flags so they could pull cells for easier moving.

These are certainly true deep cycle batteries. I've once went 13 days with 1 hour of direct sunlight, I figured they were drawn down to 20% SOC or worse the last couple days. This was fall 3-4 years ago. I brought up and equalized ass I could, I don't run a generator (personal choice)

I likely damaged them a bit. I had one cell poisoned early, but it was always one of the highest SG for a couple years later it became the weakest cell. My guess is the battery would tests out about 80% of new, mostly due to bad cell. Went 4 cloudy/minimal days this year and dropped minimal load voltage to @22.5. I equalized it out and it continues to do well.

Expect/hope to make it 12 years, but I backed off my cost estimates to a 10 year life. 3 strings of 6 volt GC batteries would have a similar capacity. with a cost of around $1200 delivered. Total cost might be similar, though I'm happy with the forklift battery and would replace it for the ease of inspecting electrolyte and higher potential life. I would extend my absorption rate earlier (went 4 years with 1-1.5 hour absorb) and I have nearly no threat off poisoning/messing with my system. Unless lithium batteries have a dramatic reduction, I'll replace this battery in a few years when it dies.

DanS26 · December 2019

mike95490 said:

"Usually Floating by noon means nothing" when it's cloudy !

When the sun comes out, my arrays really slam the batteries with about 60A ( 2 arrays, 2 controllers) and if I've not been keeping up with the generator, it can take 2 days to refill the 800ah bank.
We get a couple weeks like this every year
( NiFe - no sulfation or stratification issues )

Mike....where are you getting this weather chart?

mike95490 · December 2019

I use Weather Underground. Sadly, they got bought out recently and have ruined their android app, and screwed up my 12 year long ad free subscription. their web / browser chart still mostly works well.

https://www.wunderground.com/forecast/us/ca/willits/95490?cm_ven=localwx_10day

softdown · December 2019

mountainman said:

Seems ive read that fork lift Batteries rate a/h differently than GC. Where GC use 20 hour rate not sure about how fork lift rates there capacity. @Photowhit if you would how does a fork lift battery a/h rating compare to true deep cycle or GC. Also how do they compare dollars to kilowatt?

It can be impossible to safely install an ~ 2000 pound block of lead in a good location. Then it has to be removed at the end of its life. Especially the relatively tall and skinny 24 volt configurations. I moved mine through ice and sand because I had to. It fell over twice, I jumped in the right direction twice. Not planning to move it again. I see that as a big drawback with the major forklift batteries.

On the other hand, no expensive cabling is required. But they certainly use a lot more water than typical batteries. I would be willing to work with ~1000 pound batteries inside of a house with no staircase challenge. Not a lot more than that.

mcnutt13579 · December 2019

I have said it before and I will say it again. Energy storage does not belong anywhere near a house. You would not put a propane tank in a house, do not put a battery in a house.

Assuming you have a shed with a solid concrete floor. Rent a machine/hire a crew to move it once every 10-15 years. Easy and done. Industrial batteries are way better than anything you can move by hand.

softdown · December 2019

mcnutt13579 said:

I have said it before and I will say it again. Energy storage does not belong anywhere near a house. You would not put a propane tank in a house, do not put a battery in a house.

Assuming you have a shed with a solid concrete floor. Rent a machine/hire a crew to move it once every 10-15 years. Easy and done. Industrial batteries are way better than anything you can move by hand.

I think almost every regular poster may take issue with that assessment. Safe to assume that your car battery and fuel tank are procured in a trailer that follows at a safe distance?

BB. · December 2019

Energy storage is also a matter of materials and scale...

A single car battery is 1/10th the size/weight/energy storage of a typical off grid battery bank.

Gasoline/diesel are liquid at room temperature and if there is no oxygen/air with the fuel, it is much less likely to cause issues. Plus it is easier (in general) to suppress gasoline/liquid fires vs propane/LNG/etc. fires. And again scale. 100's of gallons of propane vs 10-20 gallons of gasoline. Plus when propane tanks get hot/overfilled, they can vent.

Propane tends to settle (heavier than air) vs natural gas which does not (lighter than air) (gasoline fues are heavier than air too--But garages are generally above grade and are vented--And newer regulations require dryers+water heaters to be elevated to reduce the chances of fire/explosion, and newest water heaters that use metal screens to prevent flashovers).

Add the issues of electric cars, and their battery failures (again, many times more energy than a car starting battery). And the in ability to make a failed/failing battery safe short of storing the whole car in a tank of water to lessen the chances of re-ignition.

Issues of Li Ion chemistry cells and the possible hydrofluoric acid fumes from a failing Li Ion battery, the level of toxicity is many times higher than getting sulfuric acid based electrolyte on your skin/breathing the fumes.

Not saying that 20 gallons of gasoline and a battery in a car, stored in a garage, is entirely safe (there are many house/garage fires involving said cars)... Just be aware of the risks and do what you can to minimize them (both for safety, and cost of failures/rebuilding).

-Bill

mountainman · December 2019

Comparing 2 strings of 4 top quality 330 a/h l16 Batteries for a 24 volt system. Wouldn't the price per kw be about the same?
Without the mobility issues. Or would the forklift battery last longer. Making it more cost wise.

softdown · December 2019

BB - you seem to be referring to propane when mcnutt was admonishing us not to have solar batteries in the house. mcnutt13579 said:

I have said it before and I will say it again. Energy storage does not belong anywhere near a house. You would not put a propane tank in a house, do not put a battery in a house.

My Denver home has natural gas piping connected to an unlimited supply. As do most cold weather homes. Even in N. Carolina we had a large container of heating oil/diesel next to the house. As did nearly everyone else with an older home.

Its all good though. The important thing these days is to identify as safe from hazardous materials - which are literally everywhere. Got a lithium battery sitting on my lap right now. With electricity going to it. Shiver me timbers.

softdown · December 2019

mountainman said:

Comparing 2 strings of 4 top quality 330 a/h l16 Batteries for a 24 volt system. Wouldn't the price per kw be about the same?
Without the mobility issues. Or would the forklift battery last longer. Making it more cost wise.

Seems that forklift batteries tend to claim to last longer. None of us has deciphered the magical pixie dust they would use to attain that achievement. Though it is clear that a 2000 pound FLA battery will tend to outperform 1400 pounds of FLA batteries.

BB. · January 2020

In theory, good quality forklift batteries should last 15+ years. Downside is weight, they need more solar (higher self discharge, suggest at least 13% rate of charge vs 10% minimum for FLA batteries), and they use more distilled water and seem to have less room for electrolyte (you may have to check/add water more often over the life of the batteries).

Some forklift batteries, you can change out a bad 2 volt cell--So that can be nice, if needed.

Past this point, I will let others with much more experience than I add to the thread.

-Bill

mountainman · January 2020

Changing out a cell would be adding new to old. Doesn't the rules apply to lift Batteries
The same as Gc or floor sweeper Batteries?

BB. · January 2020

Yep... But changing 1x 2 volt cell and leaving the other 11 (if 24 volts or 23 cells for a 48 volt battery) is probably a better "risk/reward" vs changing out 6 or 12 volt batteries (larger percentage of bank "replaced").

We had one member from Hawaii here that was buying up used 36 VDC batteries (18 cells). And he would wire around the bad cells and make it a 24 volt battery out of the remaining good cells (and he could use any of the other 2 volt cells that still may be good later if he found another bad one).

Overall, he was very happy with the results. We have not heard from Adas in about a decade, but you can look through his posts for further information:

https://forum.solar-electric.com/profile/adas
https://forum.solar-electric.com/profile/discussions/adas
https://forum.solar-electric.com/profile/comments/adas

-Bill

softdown · January 2020

mountainman said:

Changing out a cell would be adding new to old. Doesn't the rules apply to lift Batteries
The same as Gc or floor sweeper Batteries?

I'm kind of known for "independent views" - I think that "rule" is solid gold for battery sellers and installers. Perhaps fine for people with tons of disposable income and no hobbies to support. I'd also bet our government does it a lot - almost anything to drive up the debt. Actually I know that - my brother does maintenance for the government. He hates the fact that so many of his co-workers never fix anything. They just replace everything. Pretty easy to plug in new stuff and unplug old stuff.

Replacing entire units instead of fixing bad parts? Your choice amigo. Others will disagree of course. We have plenty of the aformentioned bouncing around.

Solar batteries are very frequently killed by one bad cell. That has been the case with every single one of the five batteries I have had to replace. According to this pearl of wisdom, I would have replaced eight batteries, instead of one, a total of five times. I would consequently now be moving back to the grid "teet".

Sure they were not the best solar batteries at all. Last I checked not everyone drives a Toyota or Honda with manual trannie or a Ford truck(I have five by the way). Lots of people "invest" in the wrong item. Especially the first time.

Photowhit · January 2020

mountainman said:

Changing out a cell would be adding new to old. Doesn't the rules apply to lift Batteries
The same as Gc or floor sweeper Batteries?

I think in general it does follow that 'rule'. Like I said in my long reply, I have a poisoned cell. I know it's what 'bottoms out' and reduces the batteries capacity. Likely some jerk poured a can of beer in it, or something, back when I worked security.

If it was simple to replace I would have years back, it happened in the first year of the batteries life, though didn't effect it's SG until later. Because of this I was very interested when I saw a forklift battery made with flags on each cell. This would make moving the battery much easier and replacing a cell easier.

As is, I would have to have someone drive out from St. Louis to 'pull' the bad cell and replace, The cost would be prohibitive. I may 'play' with this battery one it is replaced and try to chemically clean the plates and replace the electrolyte. I've been to OBS(?) in St Louis and watched their operation of rejuvenating forklift batteries.

I only expect 5-8 years out of L -16 batteries. Some better batteries you might expect 10, Rolls Trojan. Like I said I only expect about 15 years normally from a forklift battery, I'm 8 in and content that I'm good for many more even as is... having 2 sets of L16 would be more hassle to check and water as well.

The 2 day reserve

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