Exploded Batteries, please help and explain.

[John Suter]

Hi Adria,

Sorry you are having so much trouble.

First, what likely happened. Typically, the
lead-acid type batteries you are using for starting
and possibly for the coach, will indicate 12.65V when
fully charged and at rest. "Fully charged" batteries
will contain a maximum amount of sulphuric acid
(H2SO4) which has a freezing point well below 32
degrees farenheit. As the batteries discharge (a
discharged battery will indicate 12V or less) the
electro-chemical reaction tends to change the liquid
composition toward H2O (water) which we know has a
freezing point close to 32 degrees farenheit. If
lead-acid batteries are overcharged (often called
boiled) the liquid evaporates, at which time water is
added back to a level to cover the lead plates, and
the batteries recharged to convert the water back to
acid. In either case it would appear the batteries
reached a temperature below that required to freeze
the remaining liquid to the point of cracking the
cases.

--- Adria Haynes <mrbeebody@...> wrote:

> I
> decided then that
> I'd just leave it plugged into shore power through
> the winter and
> leave the battery switch by the shifter set to OFF.

Can't say for sure about your model, but typically,
the battery charger only charges the coach batteries
and not the engine batteries unless the battery switch
(boost switch) is set to on, then, if left on for
prolonged periods of days/weeks, the engine lead-acid
batteries become "boiled."

> I went out about 5-6 weeks ago, flicked on the
> battery switch, and
> she fired right up.

When you did that, you electrically "combined" all
batteries (coach and engine) and, as the coach
batteries had been charging all along, they in effect
provided the power to start your coach. Note: in all
likelyhood, your engine batteries were already
dead/damaged.

> I let her tun for about 30
> minutes and all was
> well.

The engine alternator provided a charge for both the
engine and coach batteries, but 30 minutes was
probably not sufficient to charge the engine
batteries. You did not say whether or not when you
shut off the engine, you also disabled the battery
switch. If so, the engine batteries returned to their
uncharged state. If not, the engine batteries likely
were so discharged, or damaged from prolonged
discharge, that they "tricked" the charger into
providing maximum charge amperage until all remaining
batteries became boiled and damaged.
This situation/causation is why the recommendation
is to replace all batteries at once. An attempt to
charge damaged batteries along with good batteries
will likely damage them all.

> I spoke to a different guy at the Sam's club
> and He started telling me that you can't
> let 6V
> batteries get that cold

Unfortunately, he should have suggested that
batteries should be fully charged to survive cold
weather.

>
> I didn't think there would be any problem with
> leaving it plugged in
> since it was made for full timers who would do the
> same darn thing.

I trust the above explanation will clarify that
leaving it "plugged in" still requires that a close
eye be kept to prevent overcharging and "boiling" and
the acid/water level must be kept above the top of the
lead plates at all times.

> Has anybody else ever experienced this?

Most of us have also learned the hard way,
unfortunately.

John Suter


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