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Downloads + FAQ + Definitions + Cross Reference


FAQ: Frequently Asked Questions

General Questions:
Q:
Why is charging voltage so critical to both gel and sealed lead acid batteries?
Q: What is the difference between gel cell and starved electrolyte batteries?
Q: Can I store my sealed battery in my garage during the winter or will it freeze?
Q: Are your gel batteries approved for air transportation?
Q: Do Gel or Absorbed Electrolyte Batteries have a memory?
Q: Why am I not getting the run time I expect from my new MK Gel batteries?
Q: What are the advantages and disadvantages of both types of sealed valve regulated batteries?
Q: Can I store my batteries on concrete?

HME/Mobility Questions:
Q:
How often should I charge?
Q: How do I charge my MK Batteries correctly?
Q: How should a battery be stored?
Q: What is the proper way to store batteries for the Winter?
Q: I want to store my MK Gel batteries outside for the winter. At what temperature do the batteries freeze at?
Q: Do I have a battery problem or a charging problem?
Q: My batteries were over-discharged and my battery charger will not start. What do I do?

Broadband/CATV, PV/Solar Questions:
Q:
How often should I equalize my MK GEL Batteries?
Q: Don't I have to equalize my batteries to prevent stratification?


General Questions:
Q:
Why is charging voltage so critical to both gel and sealed lead acid batteries?

A: Charge voltage is critical on these types of batteries because they both are recombinant batteries. This means that the oxygen that is normally produced on the positive plate in all lead acid batteries recombines with the hydrogen given off by the negative plate. The “recombination” of hydrogen and oxygen produces water, which replaces the moisture in the battery. Therefore the battery is maintenance free and never needs watering.

The sealing vent is critical to the performance of a sealed battery. The cell must maintain a positive internal pressure, otherwise the recombination of the gasses will not take place and the cell will dry out and not perform.

In addition, the valve must safely release any excess pressure that may be produced during overcharging, otherwise the cell would be irreparably damaged. It is because of the safety mechanism of the valve that overcharging hurts a sealed battery.
The excessive pressure that the valve is releasing is both hydrogen and oxygen. The more you overcharge a battery, there is less oxygen and hydrogen left inside the battery to recombine and create water. In essence, the battery dries out.

It’s important to note that a sealed battery must never be opened once it leaves the factory. If opened, the cell loses its pressure, and the outside air will “poison” the plates and cause an imbalance that destroys the recombination chemistry.

Hence the name: Sealed, Valve Regulated (SVR) Battery.

The correct charging voltage for a Gel battery is 14.4 to 14.6 volts maximum at 68°F. The correct charging voltage for our Absorbed lead acid battery is 14.4 to 14.6 volts maximum at 68°F.

 

Q: What is the difference between gel cell and starved electrolyte batteries?

A: Both are recombinant batteries; both are sealed valve regulated.

The major difference is that the “starved” or “absorbed electrolyte” battery contains an amount of liquid electrolyte added at the factory that soaks into the special separators. Therefore, it is non-spillable because all of the liquid electrolyte is trapped in the sponge like separator material. There is no “free” electrolyte to spill if tipped or punctured.

 

Q: Can I store my sealed battery in my garage during the winter or will it freeze?

A: Both types of our sealed batteries can be stored in temperatures as low as -20°F without freezing provided the batteries are fully charged.

 

Q: Are your gel batteries approved for air transportation?

A: Yes. Most of our gel batteries are approved for air transport by the F.A.A., I.A.T.A. and the D.O.T. This information is stated on a label located on the battery.

 

Q: Do Gel or Absorbed Electrolyte Batteries have a memory?

A: Our batteries do not have a memory. This is only true of ni-cad batteries.

 

Q: Why am I not getting the run time I expect from my new MK Gel batteries?

A: Our gel batteries are made with thicker plates than other batteries. It is because of these thick plates that we are able to get a longer cycle life from our gel batteries. The downside is that it takes longer for all the material inside these plates to become active. It takes approximately 15-25 cycles to break the battery in.

 

Q: What are the advantages and disadvantages of both types of sealed valve regulated batteries?

A: Gel Battery Advantages:
• Totally maintenance free
• Air transportable
• No corrosion
• Spill proof/leak proof
• Installs upright or on its side
• Superior deep cycle life
• Very low to no gassing (unless overcharged)
• Compatible with sensitive electronic equipment
• Superior shelf life
• Rugged and vibration resistant
• Very safe at sea with no chlorine gas in bulge (due to sulfuric acid and salt water mixing)
• Will not freeze to -20°F
• Lowest cost per month (cost / months of life)
• Lowest cost per cycle (cost/ life cycles)

Gel Battery Disadvantages:
• Higher initial cost
• Heavier weight
• Water can not be replaced if continually overcharged
• Automatic temperature sensing, voltage- regulated chargers must be used
• Charge voltage must be limited to extend life
(14.4 to 14.6 volts maximum at 68°F)

Absorbed Electrolyte Advantage:
• Totally maintenance free
• Spill proof/ leak proof
• No corrosion
• Installs upright or on its side
• Lower initial cost than gel batteries
• Compatible with sensitive electronic equipment
• Very low to no gassing (unless overcharged)
• Excellent for starting and stationary applications
• Will accept a higher charging voltage than gel batteries

Absorbed Electrolyte Disadvantages:
• Shorter life cycle than gel in deep cycle applications
• Automatic temperature sensing, voltage regulated chargers must be used
• Water can not be replaced if continually overcharged
• Charge voltage must be limited to 14.4 to 14.6 volts maximum at 68°F

 

Q: Can I store my batteries on concrete?

A: Many people have the impression that when batteries sit on concrete, energy “leaks out” or they are ruined. The short answer is that letting modern batteries sit on concrete does not harm or discharge them in any way.

However, this legend is historically based in fact. The first lead-acid batteries consisted of glass cells that were enclosed in tar-lined wooden boxes. A damp concrete floor could cause the wood to swell, breaking the glass inside.

The Edison cell (i.e. the nickel-iron battery) that preceded the rubber-cased battery was encased in steel. Those that weren’t isolated in crates would discharge into concrete quite easily. Later battery cases used primitive hardened rubber, which was somewhat porous and could contain lots of carbon. A moist concrete floor combined with the carbon in the battery cases could create electrical current between the cells, discharging them.

None of this is a problem with modern batteries in their hard plastic shells. In fact, concrete is generally an excellent surface on which to place a battery. The electrolyte in a battery sitting on an extremely cold floor with very hot air around it could stratify, causing damage from sulfation; whereas concrete provides good thermal mass to buffer any temporarily extreme temperatures in the battery compartment.


HME/Mobility Questions:
Q:
How often should I charge?

A: Daily Users:
Charge daily. This applies to anyone who actually uses his or her equipment outside of the home.

Occasional Users:
Always be sure to charge before an outing and always after active use. The ideal recharge point is about 50% on a scooter or wheelchair gauge.

 

Q: How do I charge my MK Batteries correctly?

A: To properly charge your mobility battery, follow these simple procedures:
- Use the manufacturer’s automatic charger for all routine charging.
- Never use an automotive or wet-type charger on gel/sealed batteries. (They’ll quickly ruin your battery).
- Never run your battery completely flat.
- Don’t “top off” the battery with frequent charging.

 

Q: How should a battery be stored?

A: - Always store your batteries FULLY CHARGED.
- Check all batteries once a month and recharge as needed.
- Wet batteries can hold their charge up to 3 months.
- Sealed batteries can hold a charge for up to 6 months.
- When storing a chair or scooter for more than 2 weeks, charge the batteries and then disconnect them.
- Avoid hot and cold extremes when storing.

 

Q: What is the proper way to store batteries for the Winter?

A: Store batteries fully charged. Check them once a month and recharge as needed. Sealed batteries can hold their charge from 6 to 12 months. Remember, if storing your chair for longer than a couple of weeks, it’s best to charge the batteries and then disconnect them.

 

Q: I want to store my MK Gel batteries outside for the winter. At what temperature do the batteries freeze at?

A: MK Gel batteries can be stored in sub-freezing temperatures as low as -25°F without freezing as long as they are fully charged prior to storage. The self-discharge rate of fully-charged batteries is so low in these conditions that they will not require charging for many months; however, if your gel batteries are frozen … they will not always recover.

To attempt recovery the following is the best plan of action:

1) Bring them inside and let them sit at room temperature for two days. (They must reach 60°F).
2) Charge the batteries normally. (Follow standard safety procedures).
3) Run a capacity check either through a quality discharge tester or by operating your power wheelchair in a controlled environment.
4) If you don’t get enough run time then repeat steps 2 and 3.

 

Q: Do I have a battery problem or a charging problem?

A: The Digital Voltmeter is still the most valuable tool in the Mobility Technician’s arsenal for sealed batteries. The starting point for checking batteries is always the charge voltage. In 24-volt systems we know the chances for two bad batteries are less than 1 in 10,000. So what we need to determine is WHICH battery is bad or if either battery is bad. This is accomplished by checking the voltage of each battery separately.

As illustrated in photo 1, voltage for a pair of batteries can read in excess of 24-volts which can incorrectly be assumed to be a good set. However, as shown in photo 2 one battery has a voltage of 12.89 volts while the battery in photo 3 is reading 11.97 volts. Combined, the voltage of this set of batteries looks good, but clearly the battery in photo 3 is bad.
1
2
3


Two batteries in a 24-volt system charge and discharge together almost as one 24-volt battery. A wide voltage separation between two batteries indicates that you may need to replace both batteries. If both batteries read similar voltage, they should be fully charged before doing any further testing.

If both batteries are below 12.0 volts, the question becomes, “WHY?” Is the battery charger working correctly? Could there be a problem with the wiring or other components of the wheelchair?

You can determine the next step in the troubleshooting process once you know the voltage of each battery.

 

Q: My batteries were over-discharged and my battery charger will not start. What do I do?

A: Have you ever had a customer state that their batteries will not take a charge even though the charger was plugged in overnight? When you checked their batteries, you found that they both read 9 volts? This is usually due to a light or a brake being left on for an extended period of time, which drains the batteries.

The reason why the charger is not working is that most wheelchair battery chargers need to read at least 21-22 volts in order to begin charging. This is how the polarity protection system of many chargers works. If the user were to hook up the positive and negative backwards, nothing would happen to the charger or the batteries because the batteries never read any voltage so it never started.

The drawback to this polarity protection design is when a user over-discharges their batteries below the 21-22 volt cutoff. Although the charger is connected, it does not receive the signal to begin the charging process so the batteries never get charged.

The best way to solve this problem is to remove the batteries from the wheelchair and charge each battery separately with a 12-volt battery charger. When each battery is fully charged, they can then be reinstalled in the chair and returned to service. Note: It may take the batteries up to 15 cycles to return to their former capacity if they have been severely discharged.


Broadband/CATV Questions:
Q:
How often should I equalize my MK GEL Batteries?

A: MK GEL Batteries never need to be equalized. Here is why: One reason why batteries are equalized is to combat voltage separation from cell to cell within a battery. A 12-volt battery is composed of six 2-volt cells connected in series internally. A 12-volt battery reading 12.6 volts on a voltmeter should equal 2.1 volts per cell. However, when batteries are manufactured in a one -shot process cell, where the plates are activated within the battery, one cell may receive more or less electrolyte than the other five cells of that battery. When this happens a battery’s cells may equal:

2.13v - 2.12v - 2.13v - 2.11v -2.09v - 2.11v. (Sum=12.6 volts)

As a battery is discharged, the cells with the lower voltage will be drained further than the cells at the higher voltage. As the same battery is charged, the cells with the high voltage will be fully charged before the cells with the lower voltage. The more a battery is cycled, the more the cell separation takes place. Equalizing batteries helps to bring all the cells of a battery to the same voltage.

Our batteries are manufactured using tank formation to activate the plates. This process guarantees a fully formed and voltage matched plate. The extra handling of the plates provides an additional inspection step in the process to verify plate quality. Plates from hundreds of batteries are formed in a tank all at once providing not only balance from cell to cell of a battery, but also balance from battery to battery of a batch. .

 

Q: Don't I have to equalize my batteries to prevent stratification?

A: When liquid electrolyte or acid stratifies, the heavier charged ions actually sink to the bottom of the cell, leaving discharged acid at the top. This allows the top of the plates to oxidize and corrode reducing performance and shortening life. The bottoms of the plates also corrode due to the action of the higher strength acid. This can happen in Stationary applications, such as the solar industry, because the battery never moves.

Because our electrolyte is a thick-consistency gel, this acid stratification can never happen, so no, it is not necessary to equalize your MK GEL Batteries.


MK Battery: 1631 South Sinclair Street • Anaheim, CA 92806 • tel: 800-372-9253, 714-937-1033, fax: 714-937-0818
email: sales@mkbattery.com