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Old 11-07-2017, 11:28 PM
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BroMikey BroMikey is online now
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Lead Acid Battery Facts

As charging circuits have evolved it is time to understand what
the newer excepted perimeters are for charging a lead acid battery.


Three Stage Battery Charging

The BULK stage involves about 80% of the recharge, wherein the
charger current is held constant (in a constant current charger), and
voltage increases. The properly sized charger will give the battery as
much current as it will accept up to charger capacity
(25% of battery capacity in amp hours), and not raise a wet battery over 125 F, or
an AGM or GEL (valve regulated) battery over 100 F.

The ABSORPTION stage (the remaining 20%, approximately) has the
charger holding the voltage at the charger's absorption voltage
(between 14.1 VDC and 14.8 VDC, depending on charger set points)
and decreasing the current until the battery is fully charged. Some
charger manufacturers call this absorption stage an equalization
stage. We don't agree with this use of the term. If the battery
won't hold a charge, or the current does not drop after the
expected recharge time, the battery may have some permanent

The FLOAT stage is where the charge voltage is reduced to between
13.0 VDC and 13.8 VDC and held constant, while the current is reduced
to less than 1% of battery capacity. This mode can be used to maintain
a fully charged battery indefinitely.

Recharge time can be approximated by dividing the amp hours to be
replaced by 90% of the rated output of the charger. For example, a
100 amp hour battery with a 10 % discharge would need 10 amps
replaced. Using a 5 amp charger, we have 10 amp hours divided by
90% of 5 amps (.9x5) amps = 2.22 hour recharge time estimate.
A deeply discharged battery deviates from this formula, requiring
more time per amp to be replaced.

Recharge frequency recommendations vary from expert to expert.
It appears that depth of discharge affects battery life more than
frequency of recharge. For example, recharging when the equipment
is not going to be used for a while (meal break or whatever), may
keep the average depth of discharge above 50% for a service day.
This basically applies to battery applications where the average
depth of discharge falls below 50% in a day, and the battery can
be fully recharged once during a 24 hour period.
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Old 11-07-2017, 11:33 PM
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BroMikey BroMikey is online now
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Battery Testing

Battery Testing

Battery testing can be done in several ways. The most popular
includes measurement of specific gravity, and battery voltage.
Specific gravity applies to wet cells with removable caps, giving access
to the electrolyte. To measure specific gravity, buy a temperature
compensating hydrometer at an auto parts store or tool supply.
To measure voltage, use a digital voltmeter in the DC voltage
setting. The surface charge must be removed from a freshly
charged battery before testing. A 12 hour lapse after charging
qualifies, or you may remove the surface charge with a load (20
amps for 3 plus minutes).

State of Charge Voltage Specific Gravity

12V 6V
100% 12.7 6.3 1.265
75% 12.4 6.2 1.225
50% 12.2 6.1 1.190
25% 12.0 6.0 1.155
Discharged 11.9 6.0 1.120

Load testing is another method of testing a battery. Load testing
removes amps from a battery (similar to starting an engine). Some
battery companies label their battery with the amp load for testing.
This number is usually 1/2 of the CCA rating. For instance, a 500
CCA battery would load test at 250 amps for 15 seconds. A load
test can only be performed if the battery is at or near a full charge.
Some electronic load testers apply a 100 amp load for 10 seconds,
and then display battery voltage. This number is compared to a
chart on the tester, based on CCA rating to determine battery

Sulphation of batteries starts when specific gravity falls below
1.225 or voltage measures less than 12.4 (12v Battery ) or 6.2
(6 volt battery). Sulphation can harden on the battery plates if
left long enough, reducing and eventually destroying the ability of
the battery to generate rated volts and amps. There are devices for
removing hard sulphation, but the best practice is preventing
formation by proper battery care and recharging after a discharge
cycle. Sulphation is the main reason a significant portion of lead
acid batteries don't attain their chemical life span.
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Old 11-07-2017, 11:50 PM
RAMSET RAMSET is offline
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Location: NYC and Conn USA
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a very useful resource for beginners and professionals

many of the fellows use this resource

Battery Information Table of Contents, Basic to Advanced
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Old 11-07-2017, 11:55 PM
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BroMikey BroMikey is online now
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Posts: 6,168
Scooter Battery Charge Rates

At this site find what a slow charge is for a 5ah battery made with
lead plates.


standard rate charger:

12 Volt 1 Amp slow charge

12 Volt 2 Amp fast rate charge

12 Volt 5-8 Ah Pack

However very few sites talk about minimum charging rates because
taking to long to charge is bad for batteries unless you have pulsing

The new switchmode charging circuitry is counted in these days and
considered an improvement.


Last edited by BroMikey; 11-07-2017 at 11:59 PM.
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