How to handle an old battery?

[Alex Adams]

You can also use an old-fashioned "dumb" charger to bring the discharged battery up to enough voltage for the "smart" charger to work. Just make sure to use the lowest amperage setting if it has more than 1 amperage setting.

[mizterwizard]

There are several ways a battery can be optimized for different uses. It takes a certain amount of sulfur to go with a certain amount of lead to make a battery that will completely use up both at the same time. Nobody builds a battery like this for several very good reasons.

To start an engine, and maybe level out electrical system loads, like a vehicle battery does it is desirable to have the maximum plate surface. The amount of electrolyte isn't very important in this case. Starting batteries will typically use up all of their sulfur before the plates are fully sulfated.

One handy aspect of this optomization is that the strength of the electrolyte directly indicates the level of charge of the battery. The electrolyte can be measured with a hydrometer and the reading compared with a chart to get the charge level. Or, since electrolyte strength is related to battery voltage, you can just look at the battery voltage and get a good idea from there what the state of charge is.

A down side of this optimization is that when the battery is truly dead the remaining electrolyte is pure water. Since pure water is an insulator, it is hard to get any current to flow through the battery to get it to start charging again. There are solutions to this situation but generally patience and a good charger are sufficient.

I don't like "intelligent" chargers because they are too smart for their own good. Most intelligent chargers will refuse to even try to charge a fully dead battery. Like Alex says, it sometimes takes a dumb charger to get things going. Another alternative is to hook up a good jumper battery to the dead battery to fool the intelligent charger into thinking it is hooked to a good battery.

In a deep cycle battery it is desirable to have the lead plates get fully used up because they are expensive and heavy and having excess lead in the battery is wasteful. In this case there is more electrolyte in the battery so that there is enough sulfur to completely sulfate the plates. This kind of battery usually has an excess of sulfuric acid because it is cheap and light weight compared to lead. The extra electrolyte takes up more room so there is less room for lead plates. This means that deep cycle batteries don't have as many cranking amps as starting batteries but in the long run they put out more electricity.

Batteries intended for stationary use have a different optimization. Since weight and size are not nearly as important, they typically have way more electrolyte than the lead can possibly use. When the plates are fully sulfated the electrolyte is still fairly strong. This means that the battery voltage is not closely associated with the state of charge. In fact, in industrial settings it is possible to regulate the electrolyte strength so that the battery voltage is nearly constant. If the goal is to back up a stationary solar array with batteries then this kind of battery is the type to have.

Often, batteries used in a stationary system are open or have easily removed covers so that if there is a problem it is possible to remove the plates, electrolyte and settled out sulfate so that the cell can be completely rebuilt. We are never going to have that situation on an RV but I thought you might like to know what happens under different circumstances.

I like desulfaters. I have a couple. If you use them from time to time they can do a lot to maintain the capacity of a battery.

Basically what a desulfater does is give the battery a very sharp jolt of high voltage, high current electricity for an instant. This jolt will fry tendrils of sulfate that tend to build up on battery plates. Left unchecked these tendrils can short out the battery. Burning them off can restore function. A desulfater will also break the connections made by sulfate that has built up at the bottom of the cells so that the cells are not shorted out there either.

[Paul O.]

Thanks for the education!

[BahneCasita]

Originally Posted by mizterwizard

There are several ways a battery can be optimized for different uses. It takes a certain amount of sulfur to go with a certain amount of lead to make a battery that will completely use up both at the same time. Nobody builds a battery like this for several very good reasons.

To start an engine, and maybe level out electrical system loads, like a vehicle battery does it is desirable to have the maximum plate surface. The amount of electrolyte isn't very important in this case. Starting batteries will typically use up all of their sulfur before the plates are fully sulfated.

One handy aspect of this optomization is that the strength of the electrolyte directly indicates the level of charge of the battery. The electrolyte can be measured with a hydrometer and the reading compared with a chart to get the charge level. Or, since electrolyte strength is related to battery voltage, you can just look at the battery voltage and get a good idea from there what the state of charge is.

A down side of this optimization is that when the battery is truly dead the remaining electrolyte is pure water. Since pure water is an insulator, it is hard to get any current to flow through the battery to get it to start charging again. There are solutions to this situation but generally patience and a good charger are sufficient.

I don't like "intelligent" chargers because they are too smart for their own good. Most intelligent chargers will refuse to even try to charge a fully dead battery. Like Alex says, it sometimes takes a dumb charger to get things going. Another alternative is to hook up a good jumper battery to the dead battery to fool the intelligent charger into thinking it is hooked to a good battery.

In a deep cycle battery it is desirable to have the lead plates get fully used up because they are expensive and heavy and having excess lead in the battery is wasteful. In this case there is more electrolyte in the battery so that there is enough sulfur to completely sulfate the plates. This kind of battery usually has an excess of sulfuric acid because it is cheap and light weight compared to lead. The extra electrolyte takes up more room so there is less room for lead plates. This means that deep cycle batteries don't have as many cranking amps as starting batteries but in the long run they put out more electricity.

Batteries intended for stationary use have a different optimization. Since weight and size are not nearly as important, they typically have way more electrolyte than the lead can possibly use. When the plates are fully sulfated the electrolyte is still fairly strong. This means that the battery voltage is not closely associated with the state of charge. In fact, in industrial settings it is possible to regulate the electrolyte strength so that the battery voltage is nearly constant. If the goal is to back up a stationary solar array with batteries then this kind of battery is the type to have.

Often, batteries used in a stationary system are open or have easily removed covers so that if there is a problem it is possible to remove the plates, electrolyte and settled out sulfate so that the cell can be completely rebuilt. We are never going to have that situation on an RV but I thought you might like to know what happens under different circumstances.

I like desulfaters. I have a couple. If you use them from time to time they can do a lot to maintain the capacity of a battery.

Basically what a desulfater does is give the battery a very sharp jolt of high voltage, high current electricity for an instant. This jolt will fry tendrils of sulfate that tend to build up on battery plates. Left unchecked these tendrils can short out the battery. Burning them off can restore function. A desulfater will also break the connections made by sulfate that has built up at the bottom of the cells so that the cells are not shorted out there either.

I bought a desulfater at the recommendation of a friend. He didn't explain the process this eloquently. As he got to explaining it he ended up saying, "just get one and use it".

Thank you for the great post mizterwizard!

[Raspy]

Originally Posted by mizterwizard

I don't like "intelligent" chargers because they are too smart for their own good. Most intelligent chargers will refuse to even try to charge a fully dead battery. Like Alex says, it sometimes takes a dumb charger to get things going. Another alternative is to hook up a good jumper battery to the dead battery to fool the intelligent charger into thinking it is hooked to a good battery.

Chargers aren't really smart or dumb, but they work on different principles and have different capabilities.

The old fashioned chargers have large transformers the work based on the voltage and cycles of AC current. These are called ferro-resonant chargers. These constantly put out power regardless of the state of charge of the battery, so they can be hooked up to a dead battery and charge it. The disadvantage is that they taper their charging to zero at a charge state that may be a bit low, and lead to sulfation, or a little high and lead to water usage. If loads are applied to the battery during charging, the battery voltage may remain low and lead to sulfation. These are the reasons this type of charger is not good for being left continuously connected. They can also make sparks when connecting that can lead to a battery explosion, though that is unlikely.

A "smart" charger uses the battery voltage to turn on the charger. This means they cannot spark. And it means that if the battery is dead, they will not come on. These chargers also address the charging in a better way. First, they put in a "bulk" charge that is the full output of the charger, and brings the battery to 14 volts. Second, they apply an "absorption" charge where they only apply enough current to hold the battery at about 14 volts. During this phase, the current is gradually reduced and the battery approaches full charge. Finally, when the battery is fully charged, as determined by it's inability to take more current without exceeding 14 volts, a "maintenance" charge is applied. This, for flooded batteries, is about 13.2 volts. At that voltage, the battery will not sulfate and will not use water, so it can sit for long periods connected without failing. If a load is applied the charger will ramp up the amps, or even go back to bulk charging, if needed to carry the load. One other feature that many smart chargers have is the ability to "condition" the battery. This is a process designed to reverse sulfation. It does this by running the battery up to about 16 volts. This process can be initiated by the charger as it decides the battery is weak, or by a timer that does it occasionally.

If a battery is too discharged to turn on a smart charger, the battery can be jumped with a better battery or charged with a ferro-resonant charger until it reaches about 10 volts. If you just need a quick charge to get a car started, the ferro charger is fine. If you want to leave a camper always plugged in, or a battery on standby in the garage, a smart charger is much better than a ferro charger. The quickest and easiest way to tell the difference between the two is the weight and the age. All old chargers are ferro-resonant. Smart chargers are much lighter in weight and usually have some kind of charge indicator lights on the front. Smart chargers come in low outputs and these are called "battery tenders". These might be in the 1.5 to 3 amp-hour output, but any smart charger can be left connected for long periods. Higher output smart chargers of about 20 amps are commonly used in marine applications and left connected indefinitely. Modern camper power supplies seem to be mostly smart chargers now. Newer solar chargers have a smart program and even my Ram has a smart charging system. It is much better to leave the charger connected than to leave if disconnected, and better to leave it connected than run it on a timer. Every time the smart charger is re-energized with a timer, it goes through it's cycles and ramps the voltage back up to 14 volts. Leaving it on means it will constantly be at the proper maintenance voltage without damage. Proper charging can keep a battery viable for 10 years or more. Flooded batteries need to have the water level checked occasionally. If water is needed, add distilled water. The level must always be above the top of the plates, but not above the top of the gas vent slots in the fill hole. Fully charged batteries are very freeze resistant, so they can remain in the trailer during winter if charged.

Car batteries last quite a while, even without being on a smart charger in the car. Every time the car starts it ramps the running voltage to 14 -14.4 volts. But it runs much less than it sits not running, and so the overall higher voltage doesn't cause much water usage. Generally cars run enough to keep the batteries charged up enough to prevent sulfation, which is the death of lead acid batteries.

Lead acid batteries are full charged at a rested voltage of about 12.65 volts. They should not be discharged below 50% which is about 12.2 volts. They should not be stored at less than full charge or allowed to self-discharge gradually over a season of non-use.

[mizterwizard]

Many newer cars have truly smart charging systems that try pretty successfully to give the battery just what it needs. Not only do they turn up the volts and amps after a start to replace the used power but they also try to bring the battery to its optimal operating temperature.

Once the battery is charged they will drop the voltage so that the battery doesn't charge at all. If the load exceeds what the alternator puts out for a while they will turn it back up so that it replaces what was lost from the battery.

All of this sounds great until you try to diagnose a faulty charging system. With the ECM doing all sorts of funny things to the battery it can be hard to tell just what's going on.

Lead/acid batteries are not the best technology available but they do the job. The have been in service for so long that all kinds of ways have been invented to help them be all that they can be. Hopefully, soon there will be better alternatives available that also fit in a budget so that we can stop dealing with the short comings of what we have now.

Then all of this crap I know about batteries will become useless, like most of what I know.

[computerspook]

OK the battery probably is iffy and I would not want it failing in the field. That is expensive and very annoying to get fixed. Wait for a sale and get a new one. Then take care of it.

OK my replacement converter in my scamp has a battery minder in it and I use the camper a lot while home as kind of an extra office. So I just keep it plugged into power. But I also am responsible for two other trailers which are not campers, but have batteries. I got about square foot solar pannels for both that hook into the 12 volt electrical and arrange it so they can see the sun. If I didn't use my camper power so much I would do that for my camper. Do that and you should be able to get many years out of the battery.

[Roamer]

Also, let the auto parts store charge it. Leave it and come back tomorrow. They do this for free and have a much better charger that will do the best job. They will load test it and tell you the condition after.
If you are not a boondocker then maybe you want a battery with some life still in it. If you want to use DC power as long as possible out in the boonies you prob need a new one or two.
Going from house to campground to campground does not require a perfect battery.