Yuasa YUMICRON YUA00ACC04 Manuel d'utilisateur télécharger pdf (Page 15)

As we mentioned earlier, an electrochemical action

within the battery produces electricity. To understand

it, let’s look inside a battery again: you’ll see cells

made up of lead plates. Some plates are positive

charged. Others are negative charged. There’s also

the electrolyte – a sulfuric acid solution that conducts

the current. It sets off the chemical process that takes

place in the battery.

So what goes on when a battery discharges?

The electrolyte reacts chemically with the lead plates –

and it’s not exactly a match made in heaven: it turns

them into lead sulfate. If sulfate reminds you of sulfa-

tion, you’re right on target: this build-up of sulfate

crystals is exactly what battery-killing sulfation is.

In the process, the electrolyte – which contains hydrogen,

sulfur and oxygen – gives up its sulfur and some of its

oxygen. The electrolyte turns to water. Now you

know why a discharged battery – filled with water

instead of electrolyte – can turn into an ice block when

the temperature drops even into the 20s. On the other

hand, a properly-charged battery won’t freeze until the

mercury gets way down in the minus range.

The chemical process causes free electrons to slowly

gather on the negative plates. They just hang there

until a load is placed on the battery – a light or starter’s

switched on – which causes a swarm of electrons to rush

to the positive plates.

If the chemical process just went on and on,

unchecked, the lead plates would soon turn totally to

lead sulfate, the electrolyte would become pure water,

and the chemical and electrical activity inside the bat-

tery would come to a standstill. It’s bad for a battery.

So is allowing a battery to remain discharged for a

prolonged period. Recharging becomes hard or

impossible.

The good news: except in extreme cases, the process of

discharging can be reversed. You work that magic by

putting a larger voltage on the battery – for example,

14v on a 12v battery. That’s charging.

Here’s what goes on when a battery charges:

The electrical charge flowing back in causes the lead

sulfates to send their sulfate back into the electrolyte.

As a result, both the electrolyte and the plates return to

their original composition.

You’ll notice bubbles in an actively-charging battery.

That’s called gassing. It occurs because hydrogen and

oxygen gases are liberated as the charging current

breaks down the water.

Several things are actually happening here. The

process breaks down water into hydrogen and oxygen

vapor, which escapes out the vent tube. You have to

replace that loss. Add distilled water to each cell after

charging. Then give the battery a “mixing charge” for

another hour. The hydrogen and oxygen gases that

are given off can also build up pressure in the battery –

which is why batteries are vented, and why the vent

tubes can’t be bent or blocked. Very importantly,

hydrogen and oxygen are very explosive. It bears

repeating that sparks, flames and cigarettes around

charging batteries can be a one-way ticket to trouble.

POINTS TO REMEMBER

❐ Deep discharge or prolonged discharge leads to harmful sulfation.

❐ A discharged battery freezes much faster than a charged battery.

❐ Charging can reverse discharging.

❐ Charging gives off hydrogen and oxygen, which are explosive.

The Discharge – Charge Cycle

SECTION

Inspecting, Testing

and Charging

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Yuasa YUMICRON YUA00ACC04 Manuel d'utilisateur Page 15

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