I have a schumacher battery charger and when the battery gets close to full charge, it's putting out 16 volts. That seems a little high to me. is it safe to hook this charger up to my batteries when they are in the truck with it putting out that many volts?

 

Such a charger belongs in trash can.
The max charger should put is 14.5-15v and that only when it is computerized and is monitoring the current to be used for short period only.
The battery maintainers, or float circuit chargers (the ideal for long therm use) maintain 13.5V.
On the other hand the very sophisticated chargers have reconditioning mode, that can run at high voltage, but for very short times in bursts.

 

Is this a linear transformer based charger?

 

Check the manual and see if it mentions a desulfication mode. Some chargers will go to 16 volts for a short time to break loose the sulfides from the plates, returning them to solution. Schumacher makes good stuff, so chances are it is by design. But check the manual to be sure. I can assure you that 16V for a short period will not harm your battery.

 

You just totally contradicted yourself. So, should he throw it away, or is it working perfectly in a very sophisticated manner?

 

OP,

Yes, this is often referred to as equalization. Most vehicle batteries are now 'maintenance free' and I would strongly recommend against performing equalization on them. Equalization produces a significant amount of hydrogen gas that is vented from the maintenance free batteries one-way valve. In a standard lead-acid battery this can be replaced by adding distilled water but this is not possible with maintenance free batteries. When the maintenance free ones get sulphated enough that they need to be equalized it is time to replace them. If your battery does not have removable caps on the top so you can add water don't attempt to equalize (or de-sulphate) them.

Gassing voltage for a lead acid battery is about 14.5V at 75 degrees F. At 16V that battery is going to be gassing like crazy and you do that too long you will run all the water out of it.

This all said, a previous poster asked if the charger used a linear power supply. That is a great question because some linear power supplies will not regulate the voltage properly when there is little to no load on them. Since you mentioned that your charger is putting out 16V only when the battery is nearly charged that may be the case. As a battery approaches 100% charge the amount of charge current decreases and approaches zero. At this point there may not be enough load on the charger and its power supply to regulate properly. If this is the case then the gassing worries I mentioned above are not a problem as the gassing is going to be very minimal because there is only a trickle of current flowing (as long as the charger is not left like this for extended periods of time).

Also, have you checked your volt meter? Are you using the volt meter on the charger or a standalone one? I have found the ones integrated into the average battery charger to be highly inaccurate. I would check the voltage with a trusted calibrated volt meter before making any decisions.


---Aaron

 

I would add that, desulfation is rarely of any benefit to a battery in a vehicle, unless it has been sitting for long periods. There is plenty of agitation in normal driving and charging to keep the electrolyte mixed and the sulfate in solution. You could just skip that step.

 

Let me explain it further.
The battery charger going that high belongs in trash.
But sophisticated chargers might have build-in reconditioning circuits, what is separate from regular battery charging.
So if the 16V happened during reconditioning (equalizing, gassing, desulficating are also the names used to add confusion) that might be normal for that mode, but in such case the battery caps should be removed. I have seen batteries exploding when charged at too high rate with caps on.
To date the longest lasting battery I heard about was in our own Mercedes. Lasted 12 years and 3 months from the time we picked up the truck, till my son decided that getting morning jump is too annoying.
The battery was never hooked to a charger in its life and being maintenance free never had caps open. Spanish made.

 

I have never heard that simply vibrating or shaking a battery eliminates or even reduces sulphation. Sulphation is a function of battery discharge level, battery temperature, and time spent discharged. Frequently driving a vehicle will help reduce sulphation because the alternator will charge the battery. If you keep your batteries at 100% charge and rarely discharge them your battery will last a very long time. People that drive long distances and often will likely find their batteries last longer than those that keep it parked in the driveway and drive 5 miles a week.

I seen some interesting desulphation techniques from pouring salts into the battery to hitting the battery with low voltage AC waves to try to blow the sulphate crystals off of the lead plates but physically shaking a battery is not one of them.

Not saying you are wrong just that I have never heard of it.

---Aaron

 

I wouldn't argue my point either, it is just what I have read. Along the same lines is stratification, which basically means the acid is stronger at the bottom of the battery. Which lends itself to sulfates building up on the bottom of the plates first. A strong boil will agitate the acid, so it is well mixed top to bottom. It is discussed more on RV sites, and solar power sites, where batteries often sit for long periods. Desulfation techniques are very necessary in those applications. But we rarely even see it mentioned on automotive sites like this.

Anyway, I think it is likely that this is what the OP saw his charger doing.

 

It is really a waste of time for a battery you can replace for $100 and since they are usually 'maintenance free' it is academic anyways as there is very little that can be done.

My experience comes from Solar power systems and -48V power plants. In those systems it is critical to perform proper maintenance. There is a much bigger investment and they tend to be discharged greater. A vehicle just needs to start and then we hope the Alternator is sized properly to handle all the electrical loads of the vehicle so the battery is doing nothing when driving.

My Trojan L16's for my solar system are expensive enough to justify equalization. $500/battery makes sense to spend some time on maintenance and I have to discharge them during periods of weak sun.

I don't even know why some car battery chargers even have an equalization option. People buy them, don't know what it does, and figure 'hey, battery reconditioning? Sounds like a great idea'. They then proceed to blow all the water out of their maintenance free batteries and destroy them.

I was looking for a Smiley of a horse being beaten to death but couldn't find one. I am sure I have bored everyone on this site with uninteresting battery info.


---Aaron

 

It was nice to discuss it with someone who understands battery theory.

As far as I know, Ford doesn't use any maintenance free batteries in their trucks. And I make it a point to not buy them. Even our Escape came with a battery with caps.

 

And it was nice to read the discussion!
Rest assured there are quite a few of us on this board that appreciate it!