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Discharging battery myths

Batteries operate amazingly
well considering how many myths there are regarding their operation and
maintenance. Here are a few of the more notable myths.

1. Storing A Battery On
Concrete Will Make It Discharge.

The best explanation for
this myth goes back to the early 1900s when battery cases were made of porous
material like tar-lined wood boxes. But today’s batteries are encased in
plastic (polypropylene to be exact) or hard rubber and are better sealed in
order to eliminate external discharge – that is, if the top of the stored
battery is kept clean. Corrosion of posts can accelerate the natural discharge
that occurs when batteries are stored.

2. Stored Batteries Don’t
Lose Their Charge.

All batteries discharge
depending on the type of battery, its maintenance, and the storage temperature.
The rate of discharge can be as low as 1% to 3% per month or as great as 60% to
70% per month. “Heat over 100°F. increases internal discharge,” says Andy
Anderson of “As temperature increases, so does internal
discharge. A new, fully charged battery left sitting 24 hours a day at 110°F.
for 30 days would most likely not start an engine.”

3. Driving A Vehicle Will

Recharge A Dead Battery.

A deeply discharged or dead
battery (that causes you to jump-start a vehicle) cannot be brought back to
full charge in a short time from running the engine. Such batteries need to be
fully recharged with an external battery charger, which uses far less energy
and does a better job recharging than an idling engine.

4. A Weak Battery Won’t Harm
An Engine’s Charging System.

A weak battery places
additional stress on a charging system and the starter, causing them both to
fail as they try to compensate for lack of voltage or current.

5. Maintenance-Free Batteries
Never Need Maintenance.

All batteries need
maintenance. For example, maintenance-free batteries can consume some of the
water in their electrolyte solution in hot operating conditions or from
excessive charging voltage. And that water needs to be replaced. The posts and
cables on all types of batteries corrode if left exposed and require care
whether they are maintenance-free or not.

6. You Don’t Need To
Disconnect A Battery When Working On It.

Always disconnect the
negative terminal on any battery you are working with. If you don’t, you risk
having the metal tool you are using around the battery contact the positive
terminal and a nearby grounded metal part on the vehicle. The battery can
deliver enough current to turn that tool cherry red in a few seconds (as the
tool will be conducting several hundred amperes of energy). Disconnecting just
the negative terminal eliminates a short circuit from occurring.

7. Refill A Battery With Tap

Only use distilled or
demineralized water in batteries. Tap water, even from a reverse osmosis
treatment system, contains calcium or magnesium sulfate crystals that fill the
pores and coat the plates on a battery. In a pinch, use rainwater.

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