Battery Care‎ > ‎Charging‎ > ‎

Battery Charging FAQ's

Return to the top of Charger FAQsHow do I safely charge my battery?

All lead-acid batteries contain highly corrosive sulfuric acid, generate explosive gasses and have warning labels that should be observed closely. For best results, charge the battery as soon as you know it is discharged. To charge your battery, follow these steps and important safety tips.

Before Charging:

1

Read the charger manufacturer's instructions.

2

Remove all jewelry and put on protective eyewear, gloves and work clothes.

3

Place the battery in a well-ventilated area since batteries emit explosive gasses.

4

Don't charge a frozen battery. Allow the battery to warm to above 32°F (0°C) before charging.

5

If applicable, remove the vent caps and check the battery's water level and, if low, add distilled water to cover the tops of the plates. Do not overfill.

6

To determine if the battery needs to be charged, test it with a hydrometer to determine its specific gravity and/or with a voltmeter to determine its state of charge.

7

If applicable, reinstall vent caps before charging.

8

While the charger is unplugged, connect the leads to the proper battery terminals. Note: For side-post and studded batteries, we recommend that you use adapters to insure adequate contact. For additional information regarding adapters, contact your local Interstate Batteries Distributor.

9

Set the charger to the proper settings for your battery, for example, 6-volts vs. 12-volts, low-maintenance vs. sealed, standard automotive vs. deep cycle.

10

Plug in and turn on the charger.

11

Do not wiggle the connections to check contact while the charger is turned on or plugged in.

12

Choose the lowest amperage setting initially. Once the charger is on and the battery is charging, you may want to choose a higher amp setting to reduce charge time.

During Charging:

1

Keep the vent caps on.

2

Do not allow smoking, open flames or sparks near the battery.

3

Do not allow the battery to become overheated or hot to the touch.

4

Discontinue charge if battery bubbles or spews acid as this is a sign of overcharging or internal damage to battery.

After Charging

1

Immediately after the battery is fully charged, turn off and unplug the charger. Continuing to charge a fully charged battery may severely damage the internal plates and shorten battery life.

2

Disconnect the leads from the battery.

3

To assure battery is at a full state-of-charge use a hydrometer. 1.265 or higher will indicate a fully charged battery or use a voltmeter after the battery sits for 2-3 hours in a static state (no load or charging). 

 
Return to the top of Charger FAQsHow long does it take to charge an automotive, powersport or marine battery?

Generally, we recommend that you use a low amp charge over a longer period of time. It usually takes several hours to effectively recharge a battery depending on how discharged the battery has become. Slow charging rates vary depending on the battery’s type and capacity.

Some chargers automatically adjust the current and length of charge according to the battery’s state-of-charge and then shut off when the battery is fully charged. If the charger requires a manual adjustment for current or shut-off, check the charger’s instructions to determine the proper current and length of charge based on your battery’s rating. 

Automotive: 
An automotive battery 5-amp to 10-amp is considered a slow charge while 20-amp or above is generally considered a fast charge. Fully charging a completely discharged automotive battery, for example, with a 10-amp charger may take approximately 6-10 hours at a temperature of 80°F. Lower ambient temperatures require a longer charge time. Repeated fast charges may overcharge a battery and reduce service life.

Powersport:
Conventional Flooded Batteries and AGM/Sealed Valve Regulated Batteries:

  1. Determine the state-of-charge with a voltmeter. Valve-regulated batteries are fully charged at approximately 12.80-13.00 volts after sitting for 1-2 hours in a static condition (no loads or charging).

    Batteries with voltage between 12.50–12.80 may need a slight charge. These batteries are below a 75% state-of-charge and a maintenance charge will keep the plate material fresh and prevent sulfation.

    Batteries with voltage less than 12.50 should be recharged at the recommended rates. Charge time for these batteries will range from 5-13 hours.

    Batteries below 11.50 volts require longer recharge times (20 hours) and often require special charging techniques. Voltage readings this low are often an indication of internal damage and usually requires replacement. At the very least, these batteries have very high internal resistance and can require higher voltage and special equipment to overcome the high resistance. Use care when attempting to recharge low-voltage batteries. Batteries that gas heavily and emit a strong odor are most likely damaged.

  2. Select a charger that is approximately 1/10th the amp hour capacity of the battery. The proper charger levels can normally be found on the battery label. Use a charger designed for motorcycle/powersport batteries. Constant current or manual chargers are not recommended.

  3. Typical charging time (in hours) versus the amount of current (charger capacity), is illustrated on the chart below. A 500 mA charger is used in this table. Using a larger capacity charger will require less charge time.
500mA Charger
Battery Amp Hr

Hours

2

2

3

3

4

4

5

5

6

6

7

7-8

8

8

9

9

10

10-11

11

11

12

12

14

14

16

16

18

18

19

19

20

20

24

24

25

28

28

28

30

30

After charge and a 1-2 hour rest, voltage should reach a minimum of 12.80 (6.35 for 6 volt) and specific gravity should read approximately 1.280. (These are only estimates.)

Marine/RV:
Make sure to use a charger specifically designed for deep-cycle or marine/RV batteries. To fully charge a completely discharged battery with a 10-amp charger may take approximately 6-10 hours. Charging time will vary based on size of battery, state-of-charge and size of charger.

 
Return to the top of Charger FAQsHow many charger types are available?

There are various charger types available. It is best to choose an automatic or maintenance-free charger, if possible. 

Automatic Charger:
An automatic charger is one that will automatically shut off when it electronically senses the battery is at or near a full charge. Many will also automatically start a recharge when it senses the battery has discharged too low.

Maintenance-Free Charger:
A maintenance-free charger is considered a charger that senses when a battery is at or near a full state-of-charge level, then automatically switches to a maintenance or float stage to maintain the battery at or near a full state-of-charge.

Manual Charger:
A manual charger is a charger where the user has to adjust time-to-charge and/or a low-medium-high charge rate. This type of charge should be consistently monitored to ensure the battery doesn’t become overcharged.

 
Return to the top of Charger FAQsHow do I select the right charger for my application?

Automotive Battery Charger:
A 5-amp to 15-amp maintenance-free or automatic charger can be used when the battery has become discharged. A 1.5-amp to 5–amp automatic charger can be used to maintain an automotive battery if the vehicle sits for extended periods. However, it should not be used to recharge a highly discharged battery.

Powersports Battery Charger:
Powersports and motorcycle batteries normally need to be charged using a charger rated no higher than 10-amps. A 2-amp to 8-amp automatic or maintenance-free charger can be used if the battery is highly discharged. A 750 milli-amp to 3.5-amp maintenance-free or automatic should be used to maintain the battery during off season or when the battery sits for extended periods.

Marine/RV Battery Charger:
Normally, marine and RV batteries are discharged often and deeply so it is recommended that a deep-cycle charger specifically designed for this use be used. A 10-amp to 20-amp automatic charger or maintenance-free charger is recommended for discharged batteries. A 2-amp to 8-amp automatic or maintenance-free charger can be used to slow charge or maintain the battery during off-season.

 
Return to the top of Charger FAQsWhat is the difference between an automatic and manual charger?

Automatic Charger:
These chargers automatically sense the voltage and current (amps) internally and shut off or switch to a maintenance charge at end of the charging cycle. These chargers are often marketed as Maintenance-Free or Automatic.

Manual Charger:
A manual charger is one that is normally a timed charger and allows a manual setting of low, medium and high levels of current and voltage regulation. It will continue charging until charger is turned off or shut off by timer. Always monitor a manual charger.

 
Return to the top of Charger FAQsShould I allow my battery to become highly discharged before recharging?

Short Answer: No.
A lead-acid battery doesn’t require to be discharged to a specific level prior to being recharged. However, the more times it is discharged to a low state-of-charge the less cycle life. As a point, “opportunity charging” is a term that refers to battery charging when the opportunity presents itself rather than waiting until the battery reaches a specific discharge level. If it is a convenient opportunity to recharge daily and the battery is showing 75% charged, don’t wait; charge it.

 
Return to the top of Charger FAQsWhat will happen if I don't charge my battery properly?

The two extremes of improper battery charging are undercharging and over- charging. 

Undercharging
Failure to allow the charger to charge long enough to restore the battery to full state-of-charge. Continually operating the battery in a partial state-of-charge or storing the battery in a discharged state will result in a condition known as sulfation.  Sulfation reduces the battery’s performance and may cause premature battery failure. 

Overcharging
Charging beyond the full state-of-charge causes accelerated corrosion of the positive plates, excessive water consumption, and in some cases, damaging temperatures within a lead acid battery. Deep-cycle batteries should be charged after each discharge and/or after storage of 30 days or more. We recommend that a deep cycle battery not be discharged below a 50% state-of-charge. Recharging a severely discharged battery (below 50% state-of-charge) will often result in reduction of battery service life and performance.

 
Return to the top of Charger FAQsDo I need a special charger for recharging sealed AGM batteries?

Yes, when recharging sealed lead-acid AGM or Gel-type batteries it is best to choose a charger with a selection specifically for them. These batteries can be overcharged by some chargers that are used for regular or liquid electrolyte batteries. Some of the liquid electrolyte chargers have their internal voltage regulation set too high for AGM or Gel battery.

 
Return to the top of Charger FAQsWhat's the best way to charge deep cycle batteries?

The maximum constant current rate in amps should be approximately 20% of the amp hour rating of the battery. Normally, deep-cycle batteries do not require special charging procedures; however, we recommend that you use a charger designed specifically for deep-cycle batteries. Repeated fast charges may overcharge a battery and reduce service life. For example, the Interstate SRM-27 is rated at approximately 100 AH, so a 20-amp charger should be the maximum. Also, it is best to use a charger that is adequate to recharge the battery within 10-12 hours. 

 
Return to the top of Charger FAQsWhy won't my battery take or hold a charge?
  • A battery may not accept a charge for several reasons. It may be beyond repair because of a bad cell or an internal short, or it could be so severely discharged that it requires a professional caliber charger. Some chargers have minimum voltages that must be present in the battery before the charger will switch on. Normally these low voltages are well below those exhibited by a battery that appears to be "dead."
  • Often however, the battery is not given the adequate amount of time to accept a charge. One of the best tips regarding battery charging is to observe the charger's ammeter swing needle (available on some chargers) during the charging procedure. After the charger is connected to the battery and is on, the needle should deflect to a high amperage level if the battery is partially discharged. If the battery is severely discharged, the needle only deflects slightly away from zero. Continue to observe the needle in either situation. On a normally discharged battery only, the needle will start to taper in amperage back toward zero, usually in less than five minutes. This reduction in amperage typically indicates the battery is accepting a charge. On a severely discharged battery, the needle will start off very low then rise. This rise of the needle is a preliminary indication that the battery is accepting a charge.
Note: Always determine the battery's state-of-charge before and after recharge. The most accurate method (on a removable vent cap battery) is to perform a specific gravity test with a hydrometer. If the battery will not hold a charge adequately, contact your local Interstate Distributor.
 
Return to the top of Charger FAQsHow can I test my charger to see if it is bad?

Check the ammeter gauge (where applicable) or the indicator lamp on the charger. If the charger is working properly, the ammeter gauge should deflect to an amperage level above zero once the charger is connected to the battery and is turned on. If the battery does not respond to charging within a few hours, your charger may not be working correctly.

 
Return to the top of Charger FAQsWhere can I find a charger for my battery?
Interstate Battery System of Lake Havasu has chargers are available for purchase. If we do not have the one you are looking for we can get commercial grade chargers for you.
 
 
Comments