Another Bank Of Batteries Cooked....

[Maine Sail]

Just another reminder that solar panels, large enough to do anything, should have a controller..

Last fall I winterized a customers boat which included fully charging the batteries, checking electrolyte level (did not need any), a specific gravity test (sight refractometer), conductance test and one hour of equalization while I was there working on the boat. I then left them 100% disconnected.

Today when I got there to reconnect everything I found a 20W solar panel connected to the house bank. This panel is only about 9% of the banks capacity which is 225 Ah's...

Last fall the batteries tested nearly perfectly, considering the age, and they put up 710CCA on my analyzer. Today they measured JUNK at just 2 CCA.... The battery cases are bulged, the positive posts are bulged and the batteries had a couple inches of exposed plate... They were chronically over charged...

Despite my suggestion that the batteries would be fine if fully charge and left disconnected, as they had been for the previous 6 years, the owner went back to the boat and installed an unregulated 20W panel.....

When I called him today; "Well I read on the internet that a panel of less than 10%........."

I'll upload some pics of the destroyed batteries soon...

This bulge around the positive post was not there last fall:

The cases were fine last fall:

Last fall these batteries were still capable of 710 CCA, today just 2 CCA........

 

[Charles Erwin]

Gotta love internet resources - they can't tell you anything that is not true!

 

[shemandr]

When you hire someone with expertise it is smart to listen to the expert. Then if something goes wrong you can complain. But if you supersede the experts advice than you have no recourse. Except that the expert would probably still like your business - it"s better than no business. But family plan rates no longer apply.
We go through this all the time.

 

[Stu Jackson]

He shoulda read YOUR articles, Maine Sail.

 

[Maine Sail]

I certainly don't mind the business right now, or ever, but I am already 6-7 weeks behind. Today's job was supposed to be about 1 hour then onto the next one... Instead it turned into half a day fetching new batteries, lugging them up and down the ladder, installing etc. etc...

Next time your yard or technician is running behind you'll have an understanding of why.....

 

[Maine Sail]

He shoulda read YOUR articles, Maine Sail.

He thought he was helping, can blame him for trying to do something good. He just never asked about it or I would have explained it to him...

I don't doubt that he read that what he was doing was okay he just got the application/context wrong. Problem is that in the winter the self discharge rate drops to literally nothing yet the panel keeps pumping and pumping so it is easy to drive the voltage over 15V even with a relatively small panel......

 

[tkanzler]

What causes the bulging? It's not like they're sealed and pressure can't escape.

 

[MrUnix]

Today when I got there to reconnect everything I found a 20W solar panel connected to the house bank. This panel is only about 9% of the banks capacity which is 225 Ah's...

How do you calculate that? I'm thinking 20W is approx. 1.6A @12v if running at 100% efficiency (which we know is impossible).. how is that 9% of a 225Ah bank?

Confused

Brad

 

[Stu Jackson]

Brad, the math of it is the panel wattage divided by the house bank in amp hours. 20/225 ~= 9%

 

[Charles Erwin]

What?

"This panel is only about 9% of the banks capacity which is 225 Ah's."

9% X 225 = 20.25 amps - not watts.

EDIT: I imagine - guessing actually - the problem is that the voltage goes up since the panel is not voltage regulated and one assumes that this leads to gassing and heat which leads to more heat and etc.

Charles

 

[Maine Sail]

What causes the bulging? It's not like they're sealed and pressure can't escape.

It s likely the positive plates buckled after losing enough electrolyte while still being fed high voltages.. Plates can physically grow in size due to corrosion of the grid. As it has been explained to me the lead dioxide, which can result from over charging, takes up more space than the grid plate lead that originally formed the plate.


I rarely see bulging in chronic undercharging but do see it occasionally in cases of over charging, especially when there is a large loss of electrolyte as was the case here.

Cases of chronic over charging are much more rare these days than they were years ago. Most battery failures I see are from chronic undercharging not over charging... In fact the last two over charging failures I've seen have both been from un-regulated solar left unattended for long periods of time. One was a bass boat with a bank of two trolling batteries and this one a sailboat stored on the hard...

I would have to guess these batteries have been subjected to a few hours of 14.6V - 15V+ every day since last October...

 

[Maine Sail]

What?

"This panel is only about 9% of the banks capacity which is 225 Ah's."

9% X 225 = 20.25 amps - not watts.

EDIT: I imagine - guessing actually - the problem is that the voltage goes up since the panel is not voltage regulated and one assumes that this leads to gassing and heat which leads to more heat and etc.

Charles

Charles the internet "rules" you often see, and what my customer saw, are a panel wattage of less than 10% of "C" won't over charge a battery.

20 watts is about 9% of 225Ah's.... Thus below the 10% guidance people often read about...

In a scenario where the batteries are being used daily then a 10% of "C" wattage panel likely will never be able to over charge batteries. However, when left unattended for months and months, in cold weather where self discharge is almost non-existent, then batteries can reach dangerous over-charging voltages...

 

[Charles Erwin]

Thank you for this. I was not aware of the "rule."

Many of us would have no reason to look for such a rule. I just charge them up, disconnect, and come back at month 4 - (mostly because I read that on Compass.) It simply did not occur to me that there would be any reason to suppose a maintenance charge would be needed at relatively low winter temperatures.

Still - I can see how easy it would be to goof honestly like your customer did.

Charles

 

[Maine Sail]

Thank you for this. I was not aware of the "rule."

Many of us would have no reason to look for such a rule. I just charge them up, disconnect, and come back at month 4 - (mostly because I read that on Compass.) It simply did not occur to me that there would be any reason to suppose a maintenance charge would be needed at relatively low winter temperatures.

Still - I can see how easy it would be to goof honestly like your customer did.

Charles

The "rules" I suspect were generally born out of the off grid or off grid RV crowd where even with everything "off" there are still parasitic loads. In those scenarios a 10% panel will barely even break even and would likely never over charge.

On boats however our batteries are often 100% isolated with no parasitic loads and over time they can over charge. It is more a problem of the "rule" being applied out of the context it was meant for....

I can't recall the last time I saw that much water loss in 6 months so the bank voltage must have been pretty high at times to boil off that much....

The good news is that he now has a solar panel and only needs to add a small controller and his batteries will be in better shape than they had been....

 

[jrowan]

This is news to me that a battery looses less power over the winter months then in the summer. I always believed, & it seems like common sense that a battery would naturally loose more capacity as the temperature decreased because of the cold temp. reducing efficiency. Why else would an engine be harder to start in the winter & run down a battery faster when starting during cold winter temps? That is, other then more resistance on the starter from a cold engine & thick oil, etc.

 

[Maine Sail]

This is news to me that a battery looses less power over the winter months then in the summer. I always believed, & it seems like common sense that a battery would naturally loose more capacity as the temperature decreased because of the cold temp. reducing efficiency. Why else would an engine be harder to start in the winter & run down a battery faster when starting during cold winter temps? That is, other then more resistance on the starter from a cold engine & thick oil, etc.

You lose or reduce cranking ability only due to the cold temps. When it warms back up all that capacity and charge are still there, except for what you use at the cold temps..

In cooler/colder weather you increase longevity, slow to nearly stop self discharge and also drastically reduce the effects of sulfation. These are all very good for the battery. Cold slows the chemical reactions and warm temps increase the speed.

Temps above 80F begin reducing battery life, increase the speed at which sulfation occurs and increase the self discharge rates. Your cranking ability is slightly increased but the heat is damaging the battery from a longevity perspective..

This is from Rolls battery:

"The effect of temperature on self discharge for the average fully charged, new, conventional battery in good condition is approximately as follows:

1. At 100° F (37.8°C) .0025 Sp.Gr. per day
2. At 80° F (26.7°C) .001 Sp.Gr. per day
3. At 50° F (10°C) .0003 SG per day

A fully charged battery stored at 80° F (26.7°C) will take 30 days before it self discharges 25 percent. At 50°F (10°C) the time period increases to 100 days. This will give you an idea of how often a battery should be checked."

The Industry standard temp rating is 25C or 77F (call it 80F for round numbers)


Cold Effects:
—Ah capacity goes down when batteries are cold
—At 32F Ah capacity is reduced by 20%
—At -20F Ah reduced 50% but battery life increases by approx 60%
—In colder temps sulfation slows and self discharge also slows.


Hot Effects:
—For every 15F above 77F battery life expectancy is cut by 50% (all types of LA batteries)
—At roughly 120F Ah capacity is increased by 12% but battery life is drastically reduced
—Charge voltages need to change with temperature especially above 77F
—@ -40F voltage can be as high as 16.4V but at 120F voltage should be no more than 13.8V (depends upon brand)

—In hotter temps sulfation accelerates and self discharge does as well​

Heat & batteries = bad for long life

Cool & batteries = good for long life

 

[Chris Patterson]

I'm friends with a gentleman that has owned a heavy truck and equipment parts house for near 50 years, so this guy has seen it happen. I was also amazed at the information from him that stated that he sells 4 times the batteries in the summer, than he does in the winter. His sales tickets from through the years supported this with math that no one could argue. When I used to hang out there, sure enough, when those days got hot, his employees were flat rolling the batteries out the door. The heat was KILLIN' 'em.

(I too am easily over a month behind, and I think my "compadre contractors" are as well. Tough Spring).