Recharging a Bike Battery

[jimjim999]

Hi All

I have a battery that appears to be for a motorcycle which was flat that came out of a sit-on mower that I bought with my house.

I'm charging it up using my Halford's automatic battery charger.

I was just wondering how long these things take?

It's been on charge now (bubbling away if i look down in there) for days! I do stop charging in the night however, as I don't like leaving these things on when I'm not awake / around.

Many thanks
Pete

[LazyPup]

JImJim999,, Thank you sir.You just made my day. While attending technical school I once had to do a complete report on lead acid batteries and after working on that project for days I wondered if i would ever have need of the information I had aquired.

Typically a lead acid battery is comprised of two or more cells. When the battery is fully charged the plates are pure lead (chemical symbol PB) and suspended in a solution of sulfuric acid electrolyte (H2SO4.)

As the battery discharges the electolyte compound H2SO4 breaks down into its basic components of sulfur dioxide (SO2) and water (H2O). The Sulphure dioxide combines with the lead (PB) to form lead sulfide (PBSO2). During this process free electrons are discharged which produces the current flow.

To charge a lead acid battery an electrical charge is then fed into the battery which causes the leadsulfide (PBSO2) coated plates to release the sulfure dioxide (SO2) which then combines with the water to form Sulfuric acid (H@SO4) and this process can be continually repeated, but during the charging process a small portion of the hydrogen (H) in the water is released through the battery caps or vents and in time will weaken the electrolyte until the battery will no longer take a charge. Great care should be taken when working near batteries that are charging because the released hydrogen gas is extremely explosive.

Caution: Whenever attaching the battery charger cables, they should be attached to the battery before the battery charger is plugged in to prevent the possibility of a spark that could ignite the hydrogen gas.

The best method of testing the charge on a lead acid battery is to measure the specific gravity of the electrolyte by means of a Hygrometer. ( a hygrometer looks like a small turkey baster with a flexible tube on the end and some little balls or a float inside. You can buy an inexpensive hygrometer at any automotive parts store.)

When a lead acid battery voltage level is low the electrolyte specific gravity (weight) is low and the indicator will sit low in the hygrometer tube. As a battery is charged the specific gravity of the electrolyte is heavier and the float will be suspended higher in the tube.

If a lead acid battery is extremely overcharged or charged too rapidly it can cause the lead plates to swell and make physical contact with the adjacent plate, which then shorts them out and negates there purpose. Overcahrging can also cause the plates to swell and bits of the lead will flake off, settling to the bottom of the battery housing causing the cells to short out.

To compensate for the flaking problem battery manufacturers make some batteries with a deeper sump in the bottom of the cell which allows more buildup before it will eventually short out the cell. The batteries with deeper cell cavities are sold as "Long Life" batteries.

In order to reduce the swelling problems of rapid charging some batteries are made with a wider spacing between plates.

A combination of wider plate spacing and deeper sumps results in batteries that are sold as "Deep Cycle batteries". (these are very common as marine batteries)

The time required to charge a battery is determined by the rate at which the charge is applied.

Automatic battery chargers have a circuit in them to sense the rate of charge. When a battery is severly low the electrolyte is primarily water and has a high resistance to electrical current flow. As the electrolyte begings to transform from water to sulphuric acid the electrical resistance drops and the rate of charge reduces. When the electolyte is fully restored the resistance is minimal, which means the battery draws less current from the charger. When the sensing circuit detects current flow is minimal it should shut the charging circuit off, although some charges have a trickle charge feature to keep a minimal charge on the battery to overcome shelf loss.

If you do not have a hygrometer you can get a good estimate of the overall charge by measuring the voltage in the battery. An automotive battery should show approximately 13.6 Volts DC when fully charged and will drop off to 12 volts DC or less when its dead.

Normally a rapid charger should charge the battery to full charge within an hour. A slow charger would take 2 to 6 hours depending on the size of the battery.

[jimjim999]

Hi LazyPup! Many thanks for your detailed reply! (You have already and recently helped me with advice in the plumbing section with my smelly shower!)

I have been charging my battery now for days as I described in my initial posting. So, according to your answer, it should really have charged by now, right?

I don't have any electrical gadgets or anything, but I think Halfords have a gizmo like you describe that measures the output of the battery if you take it in there, and they then tell you if you need to buy a new one.

What I would say though, is that the battery is a motorcycle one and has been described by a neighbour as a really powerful one, like as if it's between a bike and a car battery, if you know what I mean.

My neighbour told me not to charge it with the charger in 'car' mode, as this might 'damage the plates' (as you've described) and he said that a slow charge is better - so to leave it on 'bike' mode, even though it's a beefy one.

Don't know if that would make any difference - maybe I'll take it down to Halfords for them to tell me if it's ok, as it's been on for many days now!...

Just as a bit of advice (if I do need a new battery) would it be best to disconnect the battery from the mower when not in use? I was worried that the mower was taking a bit of the charge or something and completely draining the battery so much as to ruin it (like now?!). Also, my mower is kept in the shed in winter - maybe I should bring the battery into the house and store it somewhere where it's not so cold? I hear a drop in temperature can kill the battery, and ruin it's ability to be re-charged?

Many thanks for your helpful reply
Pete

[LazyPup]

Most batteries are carefully designed for the anticipated normal use of the service they are intended for. If you are operating that equipment in its normal manner such as using you automobile every day or two, or operating your mower weekly you should have no problems, but if you store the automoblie or mower for the winter you should disconnect the battery and in cold climates store the battery indoors.

Most automotive parts stores should have a battery tester on hand to check a battery for you. Some have a machine that will actually put and electrical load on the battery to simulte how well it would work when attempting to start a motor.

Overcharging a lead acid battery can be harmful because it will boil off an excessive amount of hydrogen (That is the bubbles you see) and it would deplete the electrolyte.

Due to some small internal resistances lead acid batteries will slowly discharge when stored. As you can see from the previous explanation, as the battery discharges the sulpuric acid electrolyte will transform to water and will eventually freeze and short out the plates or even rupture the battery housing.

When storing a battery do not leave it sitting on a metal or concrete surface as that will also enhance the "shelf life" discharge rate. Batteries should be store on a wooden shelf, small piece of plywood or even cardboard to prevent rapid deterioration.

Remember that lead acid batteries give off a small amount of hydrogen gas, which is extremely flamable or explosive, so they should be stored in a well ventilated area away from any source of ignition such as a water heater burner or furnace. They should also be stored close to the floor to prevent them from being knocked over and breaking the housing which would cause the acid to leak out.

HERES A TIP: If you live in an extremely cold climate which often goes to zero or below get a piece of sheet styrofoam about 1/4" to 3/8" thick and cut a piece to the size of the battery base. Place that sheet under the battery in the car battery holder and it will help keep you battery fully charged when the car is not running.

I am posting an illustration of a "HYGROMETER BATTERY TESTER". You can get a small version of them at any autoparts store for $2 or $3. Just be careful that you get the one for batteries becuase they have a similar hygrometer that is used to test the antifreeze in the radiator.

When testing or handling lead acid batteries be sure not to get any of the liquid on your skin or clothing. If you get it on your skin wash it off immediately. If you get it on your clothing it will make your clothes literally crumble apart in a few moments.