Everyone already know about checking the specific gravity of the cells and topping up the electrolyte with distilled water not tap water but there are additional things related to good care and maintenance.
In addition some people are now using AGM or GEL batteries. This completely changes battery and maintenance procedures. With the batteries being sealed it is no longer possible to check specific gravity.
Several reasons justify use of these sealed, spill proof batteries.
Transportation regulations make transport of the traditional acid filled lead batteries more difficult because they are classed as hazardous material. No such restriction exists for AGM. This makes it possible to ship them to places carriers like UPS would not otherwise consider.
AGM batteries have less self-discharge and do not sulfate as quickly. This makes them attractive for applications where prolonged periods of inactivity are regularly encountered. Vacation cabins may have a solar panel on the roof but in the absence of an occupant, who removes snow from the panel in winter times? The result could mean long periods between full recharge sessions.
Sulfation is most likely to be a problem under circumstances of intermittent use and periods of sitting partially discharged. Lead sulfation is the normal result of converting sulphuric acid and lead into a current flow.
Although every user manual clearly states to recharge a battery immediately after use how many people actually pays heed to this.
They will partially discharge a battery, and then leave it sitting because they have not discharged it fully. I have to confess I am guilty as the next person. The usual excuse being the battery will be used again real soon and we all know it can be destructive to leave a charger permanently attached and running. The rationale being the battery goes back on the charger right after we fully discharge it. Trouble is, that never seems to happen.
Now we have an expensive battery sitting they’re slowly deteriorating and loosing its capacity.
Apart from constant vigilance and care there are some other things you can do. Products called desulfators are available. These are electronic pulsers that soften the accumulated lead sulfate so that it will revert back to sulphuric acid and lead oxide when a charge current is run through it.
As electrons are withdrawn from a battery lead sulfate forms as part of the process. This sulfate is initially soft but begins to harden over time. A close analogy is thick mud splashed in the vehicle. When it is fresh and wet rain or a regular garden hose can easily rinse it off. As it dries and hardens it becomes more difficult to remove. Leave it baking in the sun for a week and you need a pressure washer to remove it.
Sometimes thick encrustations are even difficult to remove with a pressure washer requiring several tries to remove it.
Lead sulfate is similar. In this case the electrical voltage is the pressure and the volume of water is the current.
Because PV panels are very expensive most solar panel installation are on the skimpy side when it comes to charge current and weak sunlight morning and evening also detracts from the full charge current possible.
The conventional wisdom also contributes. Most guidelines recommend a three-day reserve in case of cloudy days. This is a sensible approach.
Unfortunately it sometimes results in partial discharges then a couple of days of cloudy weather. During this period of no sun the lead sulfate tends to harden, making it harder to reverse when finally some charge current once again becomes available.
The available charge current may not be strong enough to completely reverse the entire lead sulfate. This residue will remain and when further discharge occurs this old lead sulfate gets added to with new lead sulfate. If a large charge current is not used this sulfate build up becomes permanent. It may only be 1% but over time the accumulation of residual lead sulfate will rob your battery bank of storage capacity.
Attentive and prudent battery owners will have noted instructions in their user manual about ‘equalization charges done at periodic intervals. The intent of such equalization charges is to flush out lead sulfate.
In essence it is an over charge and will cause the battery to bubble and loose electrolyte; you must top up the battery before starting and after doing the overcharge.
Unfortunately this process is not recommended for sealed AGM or GEL batteries. The electronic desulfators are the only alternative.
It should also be mentioned that AGM and GEL cells required more care in charging because voltages vary compared to wet lead acid cells. They are less tolerant of over charging and suffer permanent damage if the batteries are charged to the point of out gassing.
Each type of battery has specific recommendations from the manufacturer. Long service life is dependent on how closely you adhere to these recommendations.
The old garage type charger is no longer sufficient. It is a constant voltage taper current type, which is not suitable for optimum charging of any type battery.
An added complication has to do with charge current as a percentage of total battery capacity. Most battery manufacturers will recommend not charging at more than 25%of the amp hour rating. This means a 100 A-H battery should not be charged at more than 25 amps. What they seldom mention is the minimum charge rate should not be less than 10% so you now need at least 10 amps. Charging a 100 Amp-Hour battery at 2 amps is not doing it justice nor will it reverse accumulated lead sulfate completely.
More recently lithium ion batteries have begun to be advertised as bulk storage suited to marine RV and off-grid homes use.
The technology has proven itself in small battery sizes but it is so new we have not really seen long term use in big amp hour sizes to know if this is viable. How many people keep the same laptop or cell phone for ten years?
The really high cost also proves to be a detriment. Not too many people can afford to put themselves on the ‘bleeding edge’ of technology.