Re: new rectifier, smaaaall charge
That's just not chemically or electrically possible, or battery makers would routinely add more H2SO4 (a very cheap substance) to achieve more voltage/power.
Hi wilde1j
OCV voltage is highly dependant on "acid to water" ratio. That's why a battery's voltage declines when the H2SO4 migrates into the plates upon discharge. The reason manufacturers don't add more acid to the mix is because the higher concentration increases internal activity and dissolves the grids and plates earlier in time and longevity is reduced. Since the higher concentration is not required in moderate climates, battery life is kept to a reasonable length with SG of 1.265.
In colder climates, battery efficiency drops dramatically, making cold starts difficult resulting in batteries being lowered in state of charge from the extra engine load and cranking durations. This results in frozen batteries and high warranty returns. Since H2SO4 has a very low freezing point it acts as antifreeze. To reduce freezing and to add better cold weather efficiency, some manufactures increase acid content to the mix.
Some SG is often unreadable on some hydrometers, as their mix in Canada exceeds 1.230 which results in a OCV of 13 volts.
There is a down side to this. If this battery is used in warm climates, its life expectancy is drastically reduced, as I can testify to. We have 60 batteries kept inside for training purposes. We have to replace them once a year due to premature failure. Their SG is not readable on refractometers because it is too high!
I worked in a facility for 8 years that did the warranty for batteries. Batteries average 12.8 volts when fully charged. I remember sending back a crate of batteries which would only reach 12.6 volts fully charged. (fine for the U.S. but not for -50 F)
This is why when you purchase a container of Electrolyte, it always specifies the acid content as its different for cooler climates.
In Canada, we don't use the U.S. charts and grids on OCV vs. SG because they don't go high enough for our applications.
It is very easy to prove this. Discharge a battery, drain the electrolyte, add new electrolyte. Now you have a battery with a higher acid content. Its OCV will be high, its current output will be high........but it won't live long in moderate temperatures.
Now marine batteries are a different breed of cat! Since they are only used in moderate temps, their SG is what you would consider normal. But since we see as many automotive batteries in boats as marine batteries, we have to include both in our discussions.
Cheers....
