Battery Charge Readings ?

[Jbaffoh]

Originally Posted by btrayfors

That's very typical of flooded batteries.

Consider this graph showing three banks of golf cart batteries. The two on the top are 11-year old gels.

The third bank consists of two Trojan T-105s which are about five years old. The red curve shows the performance under load of this bank which has been under "pulser" treatment for several months.

The blue curve shows the same bank which has been equalized one time only.

You can easily see that the equalization made a difference.

You can also see that it is very typical for flooded batteries under a constant load to show a voltage dip, then a recovery.

This graph shows only the first 20 minutes under load. The "recovery", though, lasts a long time; it's not just transient. That is, voltage remains at the higher level for some time.

Bill

Wow, thanks, Bill! I never noticed this before.

It seems I should pick up a charger capable of equalization.

[sailorboy1]

Well the higher charging voltages seem to be making a difference. I'm out cruising this week and have had to run the engine to motor or motorsail quite a bit. Yesterday I probably ran the engine 7 hours. The amps appear to be stopping at around 12-14 (that's with normal house and sailing loads on). I've noticed that if I stop the engine a minute and then restart to force the regulator back into the higher voltage bulk program that the result is higher amps.

This morning got up and the voltage is much better than before (like 0.3-0.4 higher). I probably still haven't gotten the batteries all the way charged (gotten to probably 98% which would be OK if not for the history) and still need to do an equalization charge, but I'm feeling better.

Thanks for the help.

[Dockhead]

Originally Posted by Maine Sail

I have made a number of suggestions, none of which you are willing to accept....

Adjusting the voltage won't help your counting errors but will help the batteries charge slightly faster and more fully. Unfortunately you simply can't get effective recharging with only an alternator unless you want to run the motor for 10+ hours. If you are on a mooring your bank really needs solar, wind or another supplemental charging source or they will sulfate..

I am always asking for electrical advice here, not giving it, but . . .

I would venture to say that you are really fighting an uphill battle -- and one which can hardly be good for your engine -- trying to keep your batts in shape with nothing but your main engine.

Why not put on a solar panel? Then your batts will be getting a steady, gentle charge the whole time you're not on the boat. It will transform their lives. Or at least buy a small gasoline generator.

Once you're up to about 80% charge, your acceptance rate, as you know, will drop off so much that you will just be killing your engine -- and wasting a lot of fuel, too -- trying to get up that last bit. And yet, as others have told you, that last bit is crucial, at least once in a while, for your batteries' health.

[sailinglegend]

Originally Posted by Don Lucas

..... I've noticed that if I stop the engine a minute and then restart to force the regulator back into the higher voltage bulk program that the result is higher amps.

You don't need to stop the engine - just turn OFF the ignition and then on again. The engine won't stop but the alternator will re-set itself to boost mode.

Things to remember:

1. Battery monitors can be highly unreliable because:
a. They don't synchronize correctly with the batteries when 100% charged.
b. As they get old the actual Ah goes down.
c. Peukerts has to be set correctly in the initial set-up.
d. The charge efficiency has to be set correctly in the initial set-up.

ALL these change with age, so the efficiency of the battery monitor gets worse and worse.

2. "Float" mode doesn't mean the batteries are 100% charged - far from it sometimes - so resetting the charger will give you an idea.

3. Batteries are at 100% when the charge current falls to less than 1% of the actual capacity. So 400 Ah bank would be charging at about 0.5 amps at about 14.4 volts (absorption voltage not float voltage). You have to keep resetting the charger to achieve this absorption voltage.

[sailorboy1]

Originally Posted by Dockhead

Why not put on a solar panel? Then your batts will be getting a steady, gentle charge the whole time you're not on the boat. It will transform their lives. Or at least buy a small gasoline generator.

I never said getting a solar panel wasn't a good idea and it is in fact on my ugrade list of things to do. There's always something to spend boat bucks on!

But for my current sailing use the time I normally spend motoring out of my home port and back during the weekend etc. is normally enough to recharge my batteries. In fact during this whole problem I normally was very low to 0 on comsumed power when leaving the boat. It just wasn't getting a good enough charge due to the voltage issue.

[sailorboy1]

So ......... since all this I have measured the SG on the batteries and it indicated that batteriewere around 50% charged. So I got a small 800watt generator for $90 and ran the charger at equalize a while a couple of times.

The boat is on the hard now so I'm going to plug in the charger and eqaulize a day, do a discharge andthen recharge.

I'm hoping that I get the batteries back to 70-80% capacity, wich is enough for the next few years of planned operation.

Planning on installing 300W of solar this winter.

[Maine Sail]

Originally Posted by Don Lucas

So ......... since all this I have measured the SG on the batteries and it indicated that batteriewere around 50% charged. So I got a small 800watt generator for $90 and ran the charger at equalize a while a couple of times.

The boat is on the hard now so I'm going to plug in the charger and eqaulize a day, do a discharge andthen recharge.

I'm hoping that I get the batteries back to 70-80% capacity, wich is enough for the next few years of planned operation.

Planning on installing 300W of solar this winter.

Don,

Just be sure to 100% charge the batteries before you bring the voltage up. They should be accepting very little current, less than 1% / "C" at 14.4V, before moving to an equalizing voltage. Some chargers run a full bulk, absorption, float cycle before you can even enter into equalization, but not all do.

What tool are you using to measure the SG? How did it compare to the terminal voltage? Were any cells out of balance?

[sailorboy1]

Originally Posted by Maine Sail

What tool are you using to measure the SG? How did it compare to the terminal voltage? Were any cells out of balance?

I used an hydrometer that since rolled off the desk and broke. The voltages suggested the batteries were 95+% SOC at the start and the SG suggested they were all about 50% (I didn't spend much time tempwrature comppensating as there wasn't any point in my mind). All cells measured pretty much the same.

The SG did come up some, but I was only able to do the charge a few hours before I had to stop to do other things (like do some work that I'm paid to do). I did run the charge some more after while hirricane prepping but couldn't check the SG. But the current suggested that they had a way to go.

[Maine Sail]

Originally Posted by Don Lucas

I used an hydrometer that since rolled off the desk and broke. The voltages suggested the batteries were 95+% SOC at the start and the SG suggested they were all about 50% (I didn't spend much time tempwrature comppensating as there wasn't any point in my mind). All cells measured pretty much the same.

The SG did come up some, but I was only able to do the charge a few hours before I had to stop to do other things (like do some work that I'm paid to do). I did run the charge some more after while hirricane prepping but couldn't check the SG. But the current suggested that they had a way to go.

Were either of these readings "resting" readings....

[sailorboy1]

Originally Posted by Maine Sail

Were either of these readings "resting" readings....

yes before I started the charge I checked the batteries, the SG indicated them at 50% while the voltage suggested they were at least 95%

This has been the indication all year long, the batteries come up and hold a voltage that indicates full charge, but once operating the voltage seems to indicate that they are 1/2 the capacity of their rating based on the amp/hrs out and the voltage

At the same time they kind of indicated this last year when they were new.

[sailorboy1]

So I'm been on the hard so have run the battery charger numerous times. I also have run an equalizer charge a couple of times.

Yesterday when I plugged into shore power the battery charge ams quickly went down to less than 2 on my 460 AH bank. I also checked specific gravity and they indicated charged.

Today I go t the boat and the voltage is still 12.78. I used the inverter to use a drop light and was using about 2.5 amps. The voltage dropped down to 12.3V???? When I turned it off the voltage slowly went back up to 12.6V. Used a whopping 2.5AH.

This just seems all weird to me as I don't feel the voltage should have dropped like this under such a small load. But this is how my batteries have acted since they were new.

Am I confused?

[s/v Jedi]

You were using 2.5A at 12V or 2.5A at 110V? If at 110V, it means you must multiply with 10 (12*10=110 good enough) for current at 12V meaning it is about 25A in that case.

[sailorboy1]

@ 12V

[s/v Jedi]

Originally Posted by Don L

@ 12V

Okay, I think it is time you give it a full cycle: turn the charger, solar etc. off and bring it down. Is is a deep cycle bank? If so, cycle deep, then charge it all the way up using the AC powered charger.

[FlyingCloud1937]

Originally Posted by Don L

So I'm been on the hard so have run the battery charger numerous times. I also have run an equalizer charge a couple of times.

Yesterday when I plugged into shore power the battery charge ams quickly went down to less than 2 on my 460 AH bank. I also checked specific gravity and they indicated charged.

Today I go t the boat and the voltage is still 12.78. I used the inverter to use a drop light and was using about 2.5 amps. The voltage dropped down to 12.3V???? When I turned it off the voltage slowly went back up to 12.6V. Used a whopping 2.5AH.

This just seems all weird to me as I don't feel the voltage should have dropped like this under such a small load. But this is how my batteries have acted since they were new.

Am I confused?

Don,

Your symptoms suggest a sulphated battery bank. But we don't really have enough information to make that diagnosis.

How are you monitoring amp and amp hrs?
IIRC you have a shunt that is mis-wired has that been corrected?
What is the temp of the electrolyte?

SPG can only accurately estimate the state of charge, if it is temp corrected, and at a 24hr resting voltage.

I see your symptoms all the time, the new bank takes a while to produce the actual amp/hr ratings, but what happens is it become badly sulphated before it ever gets broke-in. From poor charging practice, and poor charge design.

Your bank's 20 amp hr rate is about 23 amps...so if at 23 amp load you should be able go a good 6-7 hrs before you would see 12.3. At 2.5 amp load you shouldn't see 12.3V for at least 40 plus hrs.

You need to go to Battery University.

Lloyd