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ALL ABOUT BIG BATTERIES. Batteries Use for Emergency or Field Power – “auto” and “marine” batteries. FIRST. Batteries are not long term power supplies UNLESS There is a readily available way to recharge them. Generator Solar Panels Commercial Mains. WHAT WE WILL COVER.

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all about big batteries


Batteries Use for Emergency or Field Power – “auto” and “marine” batteries

  • Batteries are not long term power supplies


  • There is a readily available way to recharge them.
    • Generator
    • Solar Panels
    • Commercial Mains
what we will cover
  • Chemistry of Batteries (how they work, so we understand the other parts of this)
  • What kills batteries
  • Different kinds of batteries (flooded cell, Gel cell, AGM)
  • How to keep your battery healthy and prolong its life
  • We will kill some wives tales along the way
lead acid batteries
Lead Acid Batteries

This presentation covers the following type of large batteries – Lead Acid Batteries – most often used by Hams

  • Automotive “cranking” batteries
  • “Marine” Batteries (also known as deep cycle or RV)
  • Gel Cells
  • AGM (Absorbed Glass Mat)

They are big and heavy

the extreme basics
  • Lead, lead oxide and sulfuric acid react to make electricity.
  • There are plates of lead, plates of lead oxide and a solution of very strong sulfuric acid.
  • These are housed in a plastic case with “terminals” on the outside.

Each plate generates about 1.02 volts, for a total of 2.04 volts

  • Lead Sulphate is deposited on both plates.
how to get 12 volts
How To Get “12 Volts”
  • So we have a cell that makes 2.04 volts!
  • Connect six cells in series
  • Cells in series add their voltage
  • 6 X 2.04 = 12.24 volts
  • This is why a “12 volt” battery will actually show a higher voltage than “12”.
  • That is why they are called “batteries” and not cells, they are a battery of cells.
the reaction can be reversed


By applying a voltage to the terminals higher than what the cells put out.


Pb SO4 + 2 H2O Pb + PbO2 + 1 H+ + 2 H2O

NOTE: NO HYDROGEN GAS IS MADE IN THIS REACTION ! Hydrogen is only formed when the water itself is broken apart (electrolysis).

  • Now what is this???
  • When a voltage is applied to water, it is broken down into hydrogen gas and oxygen gas.
  • This happens at a lower voltage that the charging voltage.
  • As long as there is lots material for the lead/lead oxide/sulfuric acid reaction, that will be favored over the electrolysis reaction.
  • But if to much voltage is applied, then both lead/lead oxide/sulfuric reaction and the electrolysis reaction can take place.
charging voltages not all batteries need the same voltage
CHARGING VOLTAGESnot all batteries need the same voltage
  • WHY?
  • Materials added to the plates causes small differences in the voltage required to recharge
  • Why would there be other materials added to the plates?
  • Add Strength or inhibit Hydrogen formation.
plate additives
Plate Additives
  • Antimony: makes the plates stronger BUT adds to creation of hydrogen (charging voltage about 13.8 volts)
  • Calcium: helps make plates a little stronger, BUT it reduces or eliminates hydrogen gas formation
  • BUT it requires a higher charging voltage (usually about 14. 2 volts)
plate additives17
Plate Additives
  • Antimony: because of hydrogen gas formation, the cells have “access” (caps) so that water can be replenished and gas (HYDROGEN) can vent (“off gassing”).
  • Calcium: These are usually seen as “sealed” or “maintenance free” batteries.
  • WHY?
Hydrogen gas is formed when a higher voltage is applied than required to completely recharge the battery.
  • ALSO: The sulfuric acid solution gets hot and boils, thus loosing water.
  • AND: The water itself is broken down by electrolysis.
but first
But First
  • AMPS and VOLTS are related
  • E = (I) x (R)
  • Amps (I) = amount of electrons flowing
  • (R) = resistance in the circuit
  • E = Pressure (like water pressure)
  • If we have more amps (flow) then we must push the electrons harder (higher voltage)
  • It takes a higher voltage to charge at 10 amps that to charge at 2 amps! Important later.
charging rate22

Approximately one tenth the amp hour rating

  • 20 amp hour charging rate = 2 amps
  • 7 amp hour charging rate = 0.7 amps
  • 70 amp hour charging rate = 7 amps
  • Simple “manual” chargers have a charging voltage of about 15 volts. BE CAREFUL and do not over charge the battery or cause formation of hydrogen gas.
  • “Smart Chargers” will start the charging at a higher voltage (13.9 – 14.5) and as the battery gets closer to full charge, reduces the charging voltage. Some will then change to a “float charge” voltage.
in your vehicle or boat
In Your Vehicle or Boat
  • Automotive (“cranking”) batteries designed to provide big discharge, for short period, and then immediately recharged.
  • Why is our radio equipment designed for 13.8 volts?
  • That is the “float” voltage for most batteries.
  • The alternator in your vehicle puts out a higher voltage when the battery needs recharging, then reduces to 13.8 volts to “float” it.
  • When the battery is charged, the alternator is actually supplying the electrical power for the vehicle, and also “holding” the charge in the battery for when it is needed later.
two other activities
Two Other Activities
  • First
  • Small side reaction: Pure sulfur deposits on the plates (sulfination).
  • Sulfur does not conduct electricity
  • Sulfur coats the plate surfaces and prevents the chemical reactions, and insulates conductive surfaces.
  • Sulfination is happening all the time.
  • Worse in two cases
  • Worse when battery is left sitting and not used (discharged or charged)
  • Recharging helps knock off the sulfur from the plates
  • Vibration and sloshing also helps (like when in a car, boat, truck, RV)
low voltage
Low Voltage
  • The chemical reaction that causes sulfination is faster when the battery is discharged below 11.5 volts.
lead sulfate
Lead Sulfate
  • Second
  • During discharge, lead sulfate is deposited on the plates (remember)
  • A little bit of this falls off the plates and settles in the bottom of the battery
  • When the lead sulfate is not on the plate, it cannot be turned back into lead and lead oxide, thus the battery eventually will not be able to take much of a charge, or eventually will take no charge.
amp hours
  • Definition: The number of amps the battery can deliver at a reasonable discharge rate, for a designated amount of time, at a voltage not below 11.5 volts.
amp hours examples
Amp Hours Examples

20 amp hours = 1 amp for 20 hours, or, 2 amps for 10 hours, or 20 amps for one hour, 40 amps for ½ hour, etc.

7 amp hours = 1 amp for 7 hours, 3.5 amps for 3.5 hours, 7 amps for 1 hour, etc.

70 amp hours = well, you get the picture.

reasonable rate of discharge
About one tenth the amp hour rating

20 amp hour battery = 2 amps

70 amp hour battery = 7 amps

Lead Acid batteries can provide much higher discharge rates (i.e., more amps) but sometimes at a cost.

“Reasonable Rate of Discharge”???
discharge don ts
  • Max discharge rate before harming the battery is about one fourth the amp hours rating
  • 20 amp hour battery = 5 amps before harm
  • 70 amp hour battery = 17.6 amps before harm
  • 7 amp hour battery = 1.75 amps before harm
  • “Harm” is not death, just shortened life.
discharge don ts con t
  • Don’t leave partially or heavily discharged batteries sit for a long period before recharging.
  • This increases the sulfination process and allows more time for the lead sulfate to fall of the plates.
  • This shortens the life of the battery
other harm
  • High discharge rate causes:
  • Heating of battery
  • Over heating can damage plates and connectors of cells – warping & shorts & braking
  • Overheating can boil sulfuric acid solution

All these either reduce the life of the battery, In the worse case, it can be destroyed.

but don t be afraid
  • Automotive batteries and marine batteries can handle short periods of very large discharge rates without significantly reducing the life of the battery.
  • We will talk about how to prolong the life of the battery in a little bit.
battery sizes
  • Most automotive “cranking” batteries are about 45 amp hours
  • Most “marine” (or RV or Deep Cycle) batteries or 70 to 100 amp hours
  • Most smaller batteries, such as those found in UPSs, alarm backups, etc. are about 5 to 10 amp hours.
  • Most motorcycle and lawn tractor batteries are about 10 – 15 amp hours.
flooded cell
  • So far we have been looking at what is called a “flooded cell” or “wet” battery
  • The sulfuric acid in solution is a liquid sloshing around between the plates.
  • Sealed or Maintenance Free batteries have plates with calcium which does not allow “off gassing” thus no need to put water in the battery
  • Other flooded cells need periodic replenishment of the water in the sulfuric acid solution -- due to evaporation, off gassing, and just plain old use.
gel cells
  • Same chemistry and same plates, but the sulfuric acid solution is made into a gel, like jello.
  • More efficient since the ions in the electrolyte is physically closer to the plates
  • Do not off gas unless recharged at an over voltage
  • Sometimes can be installed on side or upside down -- consult manufacturer info.
  • Act more like a deep cycle battery, can be discharged below 11.5 volts with less harm.
  • Requires a slower recharge rate than flooded cell - can be damaged easier.
  • Requires a little higher recharge voltage than flooded cell -- Calcium added to the plates.
  • Absorbed Glass Mat
  • The sulfuric acid solution is absorbed on a fiberglass mat and held against the plates.
  • Strongest construction method - can take more bashing.
  • Also acts more like a deep cycle battery
  • Takes a little slower recharge rate than flooded cell – can be damaged easier
  • Require a little higher initial recharging voltage than a flooded cell -- also Calcium.
  • Can be mounted in any position (including upside down)
differences between auto and marine batteries
Differences Between Auto and Marine Batteries
  • Auto designed differently than marine
  • Remember the “do not go below 11.5 volts” in the chemistry section?
  • Sulfination and loss of lead sulfate
  • But the “deep cycle” can mean drawing those amps from the battery that are available below 11.5 volts.
  • WHY AND HOW?????
bigger is better
Bigger IS Better
  • Average life of auto battery is about 5 years (+/- depending on how well built)
  • To over come the added sulfination and loss of lead sulfate, they just put bigger plates into marine (RV, deep cycle, etc.) batteries, so that they also last about 5 years.
  • Life expectancy of a lead acid battery is directly related to the plate size and discharge/charging usage.
  • Use a battery designed for the load.
don ts

1. Leave a battery sitting unused for a long time (even if left fully charged at first)

  • Leave a discharged or partially discharged battery sitting for a long time. Recharge as soon a possible.
    • Disuse is the biggest killer of batteries.
    • WHY? The sulfination process can chug along, uninterrupted.
don ts48

3. Over charge (to fast, to long).

    • Boil the sulfuric acid.
    • Over heat the battery causing mechanical failure
    • Use the correct charging amperage
  • Under charge
    • Use the correct charging voltage (amperage)
    • Does not drive the reaction to completion and causes sulfation and loss of lead sulfate
Stratification: (flooded cell only) The acid solution at the bottom is strong and at the top weak. This messes up battery chemistry.
    • Strong recharging stirs up the acid solution as it warms up -- but don’t boil or over heat.
    • Movement (like driving around in our car) sloshes the acid solution around.
Sulfination: Recharging and movement can help remove the sulfur deposits.
    • The process of heating up and cooling off causes expansion and contraction of the plates (again, reasonable heating) and helps break off the sulfur deposits.
    • Movement, like driving you vehicle (vibration, hitting bumps, etc.) can help shake the sulfur off the plates. It is good to take your battery out to the field.
Quickly Recharging After Discharge
    • Quickly recharging helps prevent lead sulfate from falling off the plates. It is changed back to lead and lead oxide before it has time to fall off.
    • The longer a battery sits with lead sulfate on the plates, the more of it will fall off.



float charger
“Float Charger”
  • A float charger will maintain the voltage on the battery terminals so that the sulfination reaction is minimized.
  • A float charger will help prevent “self discharge”, by holding the lead/lead oxide to lead sulfate reaction at bay.
  • Some “Smart Chargers” also have the float function.

Charge your battery from inside the vehicle! Fully Automatic Battery Charger/Maintainer with Float Mode Monitoring for 6 and 12 volt batteries. 2 Amp, 12 Volt/4 Amp, 6 Volt slow charge with Reverse Hook-Up Protection is ideal for keeping stored, lead-acid batteries charged and power maintained at all times. Great for Motorcycle, Lawn Tractor, ATV, Snowmobile size batteries and to maintain larger Car, RV, Boat, Deep Cycle, Antique and Classic Car batteries too! Includes: 50 amp battery clamps, 12V accessory plug and permanent ring connectors for fast, easy charging every time. UL listed.


DieHard 10 amp Manual Battery Charger

For cars, trucks, boats, RVs, farm equipment, motorcycles, lawn tractors with 12 volt batteries. 10 amp fast charge for every day charging needs. Charges in 3 to 5 hours.

Rust-proof, shock-resistant polypropylene case for extended life and safety

Solid-state circuitry with silicon diodes for optimum performance

Spark-proof protection in automatic mode for added safety

Copper wound transformers for long life

Reverse hook-up protection, UL listed


DieHard 10/2/50 amp. Automatic Battery Charger

12V starter-Charger. Bring a fast, powerful charge wherever it's needed. For cars, trucks, boats, RVs, farm equipment, motorcycles, lawn tractors with 12 volt batteries. 2 LEDs power on/full charge.

Rust-proof, shock-resistant polypropylene case for extended life and safety

Solid-state circuitry with silicon diodes for optimum performance

Spark-proof protection in automatic mode for added safety

Copper wound transformers for long life

Lead Acid batteries are designed to last approximately 5 years when properly used.
  • Disuse is the number one killer
  • Abuse is the number two killer
    • Over charging
    • Under charging
    • To much discharge
    • To high a current discharge
  • A battery that is used is a happy battery!
voltage drop during use
  • As we use the battery, the voltage drops
  • Remember, we don’t want to go below 11.5 volts
  • But our equipment is designed to function best at 13.8 volts.
  • Some equipment shuts down at about 12 volts.
  • Can’t get all the amp hours out of the battery
for equipment that will work down to 11 5 volts
For equipment that will work down to 11.5 volts
  • Radio will not put out full power
  • Who cares, unless you need full power
  • A 50 watt radio set at 20 watts may actually put out 15 watts at 11.8 volts
  • But if it only takes 10 watts to reach the other station, who cares.
Keeps voltage at 13.8 – 13.6 volts
  • If you can’t use the amps that are available below 12 volts, then you are dragging a lot of battery around for not many amp hours