Deep cycle battery maintenance

[Andy Taylor]

About how far above the plates should the water level be?

How often does the water level need to be checked?

Thanks.

[Fishing Rhino]

Technically, just enough water to cover the plates.  Usually, or used to be, you fill them to the level of the bottom of the fill tube when you remove the cap.

That was the way I learned to do it years ago.  Today, ?????????

The main thing is the plates should be covered.  Excess water will dilute the acidity levels of the electrolyte.

[Way2slow]

If the battery is not fully charged, add just enough distilled water to cover the plates. After the battery is fully charge finish adding water until it touches the indicator ring at the bottom of the fill opening. Never fill and uncharged battery, it's likely to boil over.

Never charge a battery with any of the plate area exposed.

You should only add distilled water, but it's better to add plain tap water than to charge it with the plates exposed and you don't have distilled water, but get distilled water to finish filling it.

The type charger you have will have a lot to do with how often you add water.  A good charger will boil very little water out during charges.  The cheap, automatic chargers can have you adding water every few charges.   If running flooded cell batteries with caps, you should check them at least once a month.  Don't take but a few minutes to be sure they are at the proper level

[Andy Taylor]

Thanks guys. When charging, should the caps be on or off?

What do you mean by "cheap, automatic charger?"

[jdw174]

If you don't have maintenance-free batteries you should pop the caps loose when re-charging.  Also, do it in a vented area.

[Fishing Rhino]

If you don't have maintenance-free batteries you should pop the caps loose when re-charging. Also, do it in a vented area.

An excellent point.  I always have the hatch to the battery compartment wide open when using the onboard charger.

Not only are the fumes explosive, they are also corrosive. 

As a side note, batteries in good condition will produce much less gas when being charged.  If you notice a sharp, pungent odor when you open the battery compartment, it's very likely you have a bad battery, or a battery on its way out.

[Way2slow]

Actually, you should not loosen or take the caps off the battery, that increase water loss during charging.  The caps are vented so they will relieve any pressure differences. 

You should prop open your battery compartment if it's enclosed. 

My boats is outside under a cover so always stick my marker bouy's under all the covers to hold them open to keep them from sweating and to vent my battery area before I put the cover on.   

[scrutch]

Another note on non-maintenance free batteries... you should hose down your batteries with water every so often. 

filling and charging those type batteries will get some electrolyte solution on the outside of the case.  If you put a volt meter on the outside of the case you can show as much as 3 or 4 volts discharge. 

Spraying down the batteries will help reduce "stand loss discharge",  especially it hot weather.

if you cant spray it in you boat, it's worth your time to remove the batteries and spray them outside the boat.

[Ann-Marie]

Although it is good advise to wash the batteries down to minimize corrosion, the amount of power lost through the surface conductivity is too small to measure. 

Battery capacity is measured in ampere-hours, that is the amount of amps being drawn multiplied by how long it flows.

Although a volt meter can measure "3 or 4 volts" that says nothing about how much current is flowing.  To get a reading on a modern voltmeter only takes a few millionths of an amp.

Even if the amount of current on the surface was 1,000 times as much that would still only be 1/1000 amp so it would take 3.5 years just to waste 1% of the battery capacity.

[Fishbone]

Waytoslow is right with what he said. Being an ex-batterery tech, we only ever used tap water on fork truck batteries. That's the 3,000 pound jobs. The tops were scrubbed with soap and water, then hosed down. The plates absorb the acid during discharge (that leaves water behind, allowing a discharged battery to freeze in the winter) which drops the level. Charging drives the acid back out, raising the level to overflow point if filled when discharged. All batteries (good or poor) give of gas bubbles when at 80% charged (leave caps on) and should not stink. At 80% a good charger will cut back on the current rate till 100% is reached. They also should not boil or get real hot....that's a sign of a sick battery.