Battery maintanance 101
Here is a copy of the message I recieved from Interstate. I thought all might enjoy and learn something. It's quite long but alot of good info.
George,
Thank you for your inquiry here at the home office of Interstate Batteries.
Q. Am I damaging the deep cycle batteries by charging them with the truck
alternator?
A. Remember, the alternator is not a charger, it is a maintainer. At start
up, the alternators' primary responsibility to all the electronic components
and to the entire electrical system then it will return to assist the
battery. Upon the start up, the battery's voltage is dropped. The amount of
voltage drop will depend on several factors. Here are a few: temperature,
battery maintenance, battery state of charge, overcharge, undercharge,
sulfation, and battery health. As long as you are at idle, the electrical
demands will exceed that of the alternators output. Therefore, the battery
in turn assist the alternator.
Q. Am I damaging the deep cycle batteries by charging them with the Onan
Generator?
A. It would depend on the output and float charge of your generator versus
the charge requirements needed for the SRM24. I assist you by giving you a
distributors' number and address nearest you if you provide to me your city,
state, and zip-code.
Q. If I leave the inverter plugged into house current at a campground or
during the off season will that damage the batteries?
A. As long as the inverter is smart and recognizes the internal resistance
of the battery and quits providing a charge to the battery. Otherwise,
constant current will be supplied to the battery creating an
overheated/overcharged condition.
Q. Would I be better off investing in your Optima batteries for my
application?
A. For your application, you will be better of using the SRM24s. The Optima
batteries are a good product. A disadvantage of them is the Optima battery
will not provide the ample amount of reserve capacity/ampere hour that your
application may require.
Here's some additional information on charging and maintenance:
1) Choose the correct charger that matches the type of battery you intend to
recharge, i. e. . liquid electrolyte, marine/RV, automotive, maintenance-free
and gel cell.
2) Match the proper battery voltage (6, 12, 24, or 36)
3) Choose the correct charger size in amps. A good rule of thumb is a
charger which will provide a maximum of 20 amps for each 100 Ah of the
battery
4) Select a charger with a capacity sufficient to fully recharge the
batteries within 8-12 hours
5) For optimum results, choose a maintenance-free type charger which is
timed or automatically shuts off when battery reaches a full state of charge
6) Always read and follow the charger instruction manual safety and
procedural recommendations. Different manufacturers offer various features
which may influence charging parameters.
*** DO NOT delay charging your battery after use. Recharge as soon as
possible after one day's use. Allowing the battery to sit discharged for
several days may hamper its recharge acceptance and ultimately its
performance
The battery in colder conditions will tend to discharge slower. Therefore,
the battery's life is longer.
About every 6-8 weeks a state of charge test will need to be performed. If
the voltage reading is below 12. 45v, charge battery to a full state of
charge. At 80 degrees a battery will be at 75% state of charge after 3
months. The longer the battery is left alone without its full state of
charge (12. 66v or 1. 265 specific gravity)battery discharge is greater as
well as sulfation within the cells. Sulfation is when a battery is allowed
to remain discharged too long, the accumulated lead sulfate in the plates
hardens and is not able to exit the plates to reconstitute the electrolyte.
Low temperatures; cold weather numbs the chemical reaction and drastically
reduces battery performance. Fully charged batteries at 0 degrees F. deliver
only 40% capacity; yet, at 0 degrees F. an engine requires twice the power
it would at 80 degrees F. A battery is at 65% efficiency at 32 degrees and
at 40% efficiency at zero degrees; so, once the battery is subject to these
cold temperatures (ambient temperatures will remain close to the same
whether the battery is insulated or not)the battery will discharge at a
rapid rate.
When batteries are maintained they can actually last quite a long time.
One of the simplest indicators of how your battery is doing is a hydrometer
reading and if you don't have a hydrometer they can be purchased for a few
dollars. When the battery begins to fail the hydrometer readings on the
individual cells will usually indicate a problem. When the readings from the
six battery cells are more than 50 points apart ( i. e. 1. 265 vs. 1. 215) the
battery needs to be replaced.
It is better to slow charge the deep cycle batteries. When you charge your
battery you are looking for quiescent current level. This is the point were
the charging amps drops to between 1 and 3 amps and remains constant. At
this point the battery is fully charged and the batteries internal
resistance will no longer accept the charge. Now if you have a dual stage
charger it will automatically shut itself off when quiescent current level
is reached. Once your battery is no longer taking a charge you can check it
with a volt meter and the reading should be at or above 12. 66 volts if fully
charged. Check the open circuit voltage of the battery every three months
if the battery hasn't used and charge the battery when the voltage falls
below 12. 45 volts (a 75% state of charge).
Should you have any other questions or concerns please e-mail me.
Sincerely,
Mark A. Estridge
Attention: TDR Forum Junkies 
even though the camper charger is only 5-6A. 
