Batteries charged - Not Really!

[gpounder]

Batteries charged - Not Really!

Setup - DP with 6 flooded GC2 batteries - 690AH total - 200 watt solar - Residential refrigerator, Dual LP finance, coffee maker, microwave, DTV and computer use

Home after 4 days boondocking in the California desert. Each day I carefully monitored the battery condition and ran the generator for about 4 hours in the morning and evening. Generator usually started when batteries were at 12 - 12.1 volts with operational load.

The morning we left the generator ran for about 3 hours and we had a 5 hour drive home. With the engine running batteries were at 13.9 volts which is normal.

So got home and plugged into 50 amp service and saw the Magnum monitor show charged and 13.5 volts, The Victron battery showed a 3 amp charge.
Now two days later I am at a 1.2 amp charge so you would thing I am fully charged but NO and I went to check water levels and do a specific gravity test. I was surprised to see the gauge in the red. I held down the charger button to activate the EQUALIZE mode with pushes the voltage to 15.6 volts which causes a initial 30 amp charge. After one cycle I am now in the green and the batteries are really charged.

Know I am very knowledgeable on batteries and the RV systems so what happened because I did do everything by the book. Basically I believe the charger got fooled into thinking the batteries were fully charged. This happens when the voltage rises to cut off level and the charger throttles back. The final charge cycle is "absorption" mode and I had it set for 4 hours but the charger moved to "charged and float" early.

Bottom line, read the meters but also do a specific gravity test. Some people recommend using "Equalize" mode once a month.

[THenne1713]

(Suspicion) would be a small film of white lead oxide terminal corrosion that stops the charge cycle at about 70-80%. I too worked w/ batteries on aircraft, but had a vehicle w/ alternator/ electrical issues, and started monitoring hydrometer readings daily. I found that charge would suddenly fall off one day, and cause was found to be this light white film, out of sight, under the terminals. I would clean the terminals and full charge would restored the next day.

[gpounder]

Originally Posted by THenne1713

(Suspicion) would be a small film of white lead oxide terminal corrosion that stops the charge cycle at about 70-80%. I too worked w/ batteries on aircraft, but had a vehicle w/ alternator/ electrical issues, and started monitoring hydrometer readings daily. I found that charge would suddenly fall off one day, and cause was found to be this light white film, out of sight, under the terminals. I would clean the terminals and full charge would restored the next day.

I will check to see if I have a volt drop across the connection points under load, batteries about 10 months old with new cables.

[richard5933]

A few stray thoughts about your initial post - no particular order and I'm not sure if any/all of it applies. Just some initial observations from your post...

Curious about the way you are checking the voltage level of the batteries. You mentioned that they "were at 12 - 12.1 volts with operational load." A possible problem is that you really can't check the voltage level (state of charge) of batteries accurately when they are under load. Best way to check is to remove the load and wait a bit for the voltage to stabilize, then take a voltage reading.

Another thing that stands out from your initial description is the way you're running the generator for a few hours at a time. My battery charger takes about 30 hours to go through a complete cycle, starting at the boost voltage of 14.6v, then the normal mode of 13.6v, and then finally leveling off at the storage mode of 13.2 volts. If I stop the process in the middle somewhere and turn off the charger it will start over again at the top of the cycle and work through it again. I'm wondering if your charger setup is being 'confused' by the shorter run times of only 4 hours.

Your post mentions the charge rate in amps, indicating how much of a charge your batteries are pulling. But, the charger doesn't push with amps - it pushes with voltage. That amp reading on the battery monitor is showing how much of a load is being applied to the system, not how much is being pushed through. If the charger is at the wrong voltage level your batteries may not charge properly. What is the output voltage of the charger that goes with the different amp readings?

On the subject of battery monitors, do you have ANY load attached to your battery bank which does not run through the shunt? If you do, then there is no way for you to ever get an accurate reading of the state of the battery bank.

I find that on my setup, with 780 Ah of capacity and a 70-amp charger, that I have to occasionally cycle everything off for a few minutes. Doing so allows the charger to get a fresh reading of the battery levels when I restart, and then I allow it to go through a complete cycle before turning off again.

Also wondering about your solar setup. You've got 200 watts of solar, but you didn't mention how that's set up. The 200 watt panels can produce about 16 amps at 12v, but that's not the important number. What voltage are your panels putting out, and what type of charge controller are you using? I've seen some solar setups which didn't produce enough voltage or had the output levels of the charge controller set too low to actually charge the batteries.

How far down are you running the batteries? You've got only about 350 Ah of usable capacity in that battery bank, and with the load you describe it would struggle to go to long without being charged. If you run the batteries below 50% state of charge 'things' can start happening that are not always good.

Hope some of this helps.

[gpounder]

Originally Posted by richard5933

A few stray thoughts about your initial post - no particular order and I'm not sure if any/all of it applies. Just some initial observations from your post...

Curious about the way you are checking the voltage level of the batteries. You mentioned that they "were at 12 - 12.1 volts with operational load." A possible problem is that you really can't check the voltage level (state of charge) of batteries accurately when they are under load. Best way to check is to remove the load and wait a bit for the voltage to stabilize, then take a voltage reading.

Another thing that stands out from your initial description is the way you're running the generator for a few hours at a time. My battery charger takes about 30 hours to go through a complete cycle, starting at the boost voltage of 14.6v, then the normal mode of 13.6v, and then finally leveling off at the storage mode of 13.2 volts. If I stop the process in the middle somewhere and turn off the charger it will start over again at the top of the cycle and work through it again. I'm wondering if your charger setup is being 'confused' by the shorter run times of only 4 hours.

Your post mentions the charge rate in amps, indicating how much of a charge your batteries are pulling. But, the charger doesn't push with amps - it pushes with voltage. That amp reading on the battery monitor is showing how much of a load is being applied to the system, not how much is being pushed through. If the charger is at the wrong voltage level your batteries may not charge properly. What is the output voltage of the charger that goes with the different amp readings?

On the subject of battery monitors, do you have ANY load attached to your battery bank which does not run through the shunt? If you do, then there is no way for you to ever get an accurate reading of the state of the battery bank.

I find that on my setup, with 780 Ah of capacity and a 70-amp charger, that I have to occasionally cycle everything off for a few minutes. Doing so allows the charger to get a fresh reading of the battery levels when I restart, and then I allow it to go through a complete cycle before turning off again.

Also wondering about your solar setup. You've got 200 watts of solar, but you didn't mention how that's set up. The 200 watt panels can produce about 16 amps at 12v, but that's not the important number. What voltage are your panels putting out, and what type of charge controller are you using? I've seen some solar setups which didn't produce enough voltage or had the output levels of the charge controller set too low to actually charge the batteries.

How far down are you running the batteries? You've got only about 350 Ah of usable capacity in that battery bank, and with the load you describe it would struggle to go to long without being charged. If you run the batteries below 50% state of charge 'things' can start happening that are not always good.

Hope some of this helps.

I subscribe to the 50% rule and in fact wrote an extensive article about it.

I do have a Vitron Battery monitor that reads the battery voltage at the battery terminals and measures AH used along with current going into the battery. The Magnum meters are helpful but the amp loads will include the Coach too not just the battery.

The Victron said I used about 20-25% between recharging or 172 amps so a 4 hour charge with a 100 amp charger should be enough. The generator was stopped when the Magnum cycled to "charged" so by the book the batteries should have been charged. I did not do any specific gravity test in the field because I left tester at home.

The Solar is just a boost, 200 watts flat on the roof will never generate full power, more for storage. In the morning and evening when I used the generator the sun was so low there would be very little charge if any at all and the solar controller is connected directly to the battery shows on Victorn.

The readings 12 or 12.1 are noted with some loads, not meant to be a static test, just a sign that I was getting low.

[paul65k]

Originally Posted by gpounder

I subscribe to the 50% rule and in fact wrote an extensive article about it.

I do have a Vitron Battery monitor that reads the battery voltage at the battery terminals and measures AH used along with current going into the battery. The Magnum meters are helpful but the amp loads will include the Coach too not just the battery.

The Victron said I used about 20-25% between recharging or 172 amps so a 4 hour charge with a 100 amp charger should be enough. The generator was stopped when the Magnum cycled to "charged" so by the book the batteries should have been charged. I did not do any specific gravity test in the field because I left tester at home.

The Solar is just a boost, 200 watts flat on the roof will never generate full power, more for storage. In the morning and evening when I used the generator the sun was so low there would be very little charge if any at all and the solar controller is connected directly to the battery shows on Victorn.

The readings 12 or 12.1 are noted with some loads, not meant to be a static test, just a sign that I was getting low.

I actually don't think that 4 hours is enough time to fully top off 172AH on conventional LA or AGM batteries. With the 3 stages of charging (Bulk/Absorb/Float) if you are starting at 75%, the bulk will only go for a very short while, after that, you go into absorb and if you look at the Victron will see that it continues to step down until it hits float and then you still need a little more to get to the 100%.

Candidly this is the main reason Lithium batteries are so popular as they charge at bulk rate (100%) up until the BMS shuts down

[Mark_K5LXP]

Originally Posted by gpounder

I believe the charger got fooled into thinking the batteries were fully charged. This happens when the voltage rises to cut off level and the charger throttles back.

Something that comes to mind is if the alternator output during the drive boosted the bank voltage leading the controller to believe absorption was finished. Even if true, or for some other reason the controller was "fooled" to switch to float early, it should've detected the bank voltage dropping and initiated another charge cycle. If it's not doing that it's not about being fooled it's not doing what it's supposed to.

Mark B.
Albuquerque, NM

[757driver]

From the drive home and then plugging in right away if the Magnum remote panel was above 12.6v then the Magnum charger would go straight to Float and bypass the Bulk/Absorb/Float phase. It seems very likely that the drive home was not with a fully charged house bank and depending on your BIM or BIRD (as installed) it may not charge full time while driving.

Also, how long is your Absorb time in the Magnum remote? May be too short for the size of your house bank.

[gpounder]

Originally Posted by 757driver

From the drive home and then plugging in right away if the Magnum remote panel was above 12.6v then the Magnum charger would go straight to Float and bypass the Bulk/Absorb/Float phase. It seems very likely that the drive home was not with a fully charged house bank and depending on your BIM or BIRD (as installed) it may not charge full time while driving.

Also, how long is your Absorb time in the Magnum remote? May be too short for the size of your house bank.

When I stopped for breaks I always check the system with the engine running and the voltage on the house was 13.9 most of the time which show the two battery set tied together charged by the alternator. Also the current going into the house batteries taped off to just a a few amps some hours later.

Now it is possible that when I got home and plugged in I never saw the charger cycle to a charging state. I will be traveling today and plug in later today and see what happens.

FYI absorb time is set for 4 hours.