Batteries are the biggest problem for most folks who have renewable energy systems. Those problems typically stem from just three causes.

1. A poorly designed battery bank, either too large or too small for the loads
2. Parallel strings of smaller batteries (an attempt to make a large batter)
3. Improper charge parameters.

All of the above constitute abuse.

Let’s talk about the first two problems.

All lead acid batteries are made up of two volt (2V) cells. Thus a six volt battery has three smaller 2V cells; twelve volts have six 2V cells, and so forth. Many folks are unaware that batteries also come in large amp-hour two volt configurations as well.

A common battery choice is paralleling small batteries together to make a large one. Paralleling looks good on paper, but because the way batteries are made they all have different internal resistance. So if we take eight six volt batteries and connect them in series for a 48 volt bank, in the series configuration electricity has to pass through every cell, resistance is not a problem.

If we were to take eight more batteries and parallel them to the first string of eight, we will have two strings with different internal resistance. One will have less resistance than the other. So when we start to charge these strings electricity will naturally take the least path of resistance and more will flow toward this string causing the voltage to come up sooner, while the second string will lag behind somewhat.

The problem starts to arise because the energy source (solar charge controller, inverter/charger or any other type of battery charger) it can only “see” the highest voltage in the system. When the first string comes up in voltage it cuts the charge rate back, and the second string doesn’t get fully charged. Now this doesn’t make much difference at first because everything is still pretty equal, but over time, the string that’s being charged fully will develop significantly less resistance, while the other, by never being fully charged, will develop more resistance because of sulfation starting to harden. The problem just exacerbates from here.

Generally speaking… “Every time you add a parallel string of batteries, you cut the life in half.”

Note: Lead sulfate crystals form as a natural part of the discharge process on the surface of the plate pores of the active material. If the sulfation is left in this condition (by not charging properly) the sulfation starts to harden. Hard sulfation = large lead sulfate crystals. Sulfation becomes a problem when large crystals form and become difficult to decompose by normal charging. Eventually the crystals “grow” completely around the plates preventing any contact between the electrolyte and the plate. When this happens the battery capacity drops dramatically. Typically at this point the battery “”Charges” quite fast and also loses its charge fast as well.

Hard Sulfation is caused by:

1. Not charging the battery up to 100% SOC at each discharge/charge cycle (Batteries need to be fully charged at least every 10 days.)
2. Allowing the battery to stay in a discharged condition (PSOC) for too long, or too often.
3. High stratification of sulfuric acid (with S.G low at the top of the jar, while high at the bottom of the jar)
4. Uneven Specific Gravity between cells (some will sulfate faster, some will “boil”, thus loosing moisture)
5. Operating battery in excessive temperatures (which will age the battery faster)

Flooded lead acid batteries also require a regular equalization charge (overcharge) to fight against stratification and to “equalize” any uneven battery cells, which will always happen over time.

The Third Problem.

We can use all sorts of devices to attempt to charge batteries; the problem is the manufacturer of the device had no idea what you were going to charge. They only knew the voltage of the bank or battery. They could not have known how big (Amp Hours) the system was and that’s the problem.

Charging with a good three step charger starts with the Bulk Charge; in this mode there’s constant current (amps) and variable voltage (the voltage will slowly rise). When the voltage has risen to a pre-programed point the Bulk passes off to the Absorption Mode. At this point the battery is around 80%charged.

In the Absorb Mode we have constant voltage and variable current, the amps typically start off at about50% and slowly taper down to around 20% if the charger is held in the Absorb Modelong enough the battery will be theoretically fully charged.

The Absorb Mode is the most important charge mode, because it’s the one that actually charges the battery fully. Batteries need to be fully charged at least once every ten days, for longest life and overall health, which will avoid abusive premature failure.

There is nothing “Built-in” to any charger that senses when the battery is fully charged. Lots of folks mistakenly assume that when the charger goes into Float Mode the battery is full… WRONG! The charger only goes into float mode when the Absorb Timer times out. This timer has (or has not) been set by someone. The factory default is purposely set short, because they have no idea of the size of battery bank you intend to hook to the charger.

Either you or your installer needs to program this setting (as well as all the rest) based on the engineering computation for your particular system i.e. the amount of solar panels, the size of your generator, the type of charge controller and the size of the Inverter/Charger that you’re using. If you’re doing this yourself and need help call us 6126-1253. If you go with the factory defaults, you batteries will fail, sure as God made little apples.

The Float Charge is relatively useless for charging. Never bother to run your generator during Float as it wastes fuel. Float Charge only fights against self-discharge of the battery; the floating charge voltage setting is never enough to fight against non-uniform specific gravities (voltage) between the different cells of the battery bank.

Equalization Charge is a nice sounding term for “overcharging” When you equalize you bring the electrolyte to a very corrosive state; in this state what corrodes are the plates. Too much overcharging just wastes the battery, but done judiciously it’s a good thing. When the battery plates corrode they are also cleaned of any impurities that are sticking to the plates, which is good.

The second benefit of Equalization is you “mix” the electrolyte up to avoiding stratification (S.G. low at the top of the jar and high at the bottom of the jar). When stratified, denser acid sinks to the bottom of the battery making a very nasty corrosive environment for the plates at the bottom to live in which will in turn corrode them away and your capacity with it.

The third benefit is the equalize part of equalization where you bring all the cells to equal voltage (and Specific Gravity) If your Equalization Charge didn’t bring all the cells to equal… Do it again!

You can’t read what has happened too soon after equalization as the batteries must sit “at rest”for a minimum of four and preferably twenty-four hours to do a good voltage reading or Hydrometer reading. Elsewise you readings will be inflated and inaccurate.

Equalization is almost all voltage and little amperage so the battery must be at full charge before programing an Equalize event elsewise it will never properly Equalize.

NOTE: If you use an accumulating amp hour meter to monitor your batteries like the TriMetric Meter or the Xantrex/Trace TM-500, and you should be, Equalization will bring the meter back to accuracy every time you equalize.

In the normal course of using a battery you ”cycle” it (you take it from full charge and discharge it, then you charge it back up) every time you cycle your battery a small amount of material flakes off the positive plate and falls to the bottom of the case never to see again. Over the whole life of the battery the plates turn into filigree and then fall apart at this point it’s no longer a battery. This sadly will never happen to most batteries sold however because 87% of all batteries “die” from abuse.

One last scenario
If your charger is not programmable, there’s no hope of you not endlessly buying and hauling batteries in and out of your place. Batteries are very expensive, nasty and heavy; it is way cheaper and easier to replace the charger with a good one than to replace batteries.

BATTERY MAINTENANCE

• Water, water and water. (Never, never let the batteries get low). If you don’t have a deionizing filter or you don’t have easy access to distilled water, use filtered rain water because it is distilled water. Never use ground water, because it contains minerals. If you really hate this task, we sell battery filling systems where you don’t have to come into contact with the battery acid at all. They’re not automatic but it takes less than three minutes a month. There are special hydrometers that fit this system as well.
• Voltage settings: follow the battery charge settings described above. Not sure? Call us 6126-1253we can help.
• Battery acid will ruin concrete. Put a good rubber matt under your batteries. We sell acid spill absorber / neutralizer to spread under the batteries that turns bright purple in the presence of battery acid. It will absorb the spill and neutralize the acid.
• Keep the tops of the batteries clean and free of dirt and moisture, to prevent “stray voltage” which will discharge the batteries slowly.
• Make sure that all the cable connections are clean and tight. Cover the connections with Quick Coat or Vaseline to prevent corrosion. Tighten the connections at least once every year, and don’t over tighten. Tight enough is the operative term here. Most battery terminals are lead and if you really tighten them the lead will squash and you’ll have a lose connection, in a very short time.
• Have an eyewash station handy that you can easily find if you’re blind. It is very cheap insurance, about 20 bucks.
• Wear protective clothing, gloves and a full face mask while working with batteries. Don’t even come within ten feet of your batteries in your new blue jeans (it’s a battery’s favorite snack)
• Keep fire, open flames, lit cigarettes well away. Don’t store flammables (like gasoline) near you batteries either.
• Make up two battery wrenches to tighten the terminals. Wrap each wrench completely with electrical tape except for the bolt end, to prevent arcing and explosion.
• Never let children near batteries. Make an enclosure with a vent to the outside and a locking lid.REMEMBER: Batteries are very dangerous!