Battery monitor may have ruined my batteries

I purchased a victron dual bank battery monitor and installed it earlier this year. I also replaced 3 of the 4 house batteries. The 3 new batteries are 105 AH AGM’s and the 4th existing battery is also a 105 AH AGM but about 2 years old at the time of the new battery install.
I calibrated the battery monitor to a house bank capacity of 360 amps. Since the existing battery was 2 years old I allowed for 60 amps of decay on this battery, hence a capacity of 360 amps not 420. (4*105) – 60 = 360.

I have used the SOC feature of the battery monitor exclusively and have never allowed the SOC to fall below 70%. This morning I got up to check the batteries as I do every morning and the SOC read 84% and for grins I checked the voltage – 10.4 volts verified by a second d v-meter.

I started the generator and checked the battery charger output and it read 85 amps. It is a 100 amp charger.

I think I’ve ruined all my AGM batteries by relying on the battery monitor.

I'm not sure I would blame it on the monitor. What would you have checked without it? Could it be a corroded connection causing high resistance? It seems unusual that they would fail overnight. Disconnect all batteries and check each individually. Maybe a bad cell?

This didn't happen overnight. I suspect that nothing has changed since the install. The only thing I can think of is there is a load that the monitor is not aware of. I very carefully researched the proper install so I think it's right.

Last night I charged the batteries to about 95% SOC but did not check the voltage. This morning about 10 hours later the SOC was 84% with only the refirg and anchor lt on. A drop of 11% SOC is consistent with this usage over this amount of time.

I know the battery monitor sums the amp use to determine a SOC, but I also thought it takes into account the voltage.

I'm charging the batteries now, but after only 30 minutes of charging the SOC is showing 95%, this can't be right.

A quick update;
The SOC shows 100% and the ammeter on the battery charger is showing 75 amps output.

Are all the grounds running through the shunt? That would be the only way a load wouldn't show.

The SOC's are not perfect. They sometimes need to be reset to "full". If your SOC is reading 100% and your charger is still putting out 75 amps, it appears the batteries are not fully charged. The charger should be tapering off as the batteries are reaching their capacity. That last 20% takes a while to put back in.

I suspect what Terry said above. There is a something that isn't wired through the shunt that should be.

meridian said:

Are all the grounds running through the shunt? That would be the only way a load wouldn't show.

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Yes all loads through the shunt except digital v meter that monitors gen start bank, eng start bank and house bank. I also have a panic alarm hot wired to a house battery that will sound a siren through a panic switch.

I will call victron. I just noticed the monitor is indicating a charge current of 60 amps with battery voltage of 13 volts, the battery charger is on and indicating a charge current of 75 amps.

The battery monitor should reset the SOC to 100% when both of the following occur:
1. Charge voltage exceeds 13.2 v and
2. Charge current is less than 4% of bank capacity, which is 14.4 amps in my case.

Current voltage 13
Current charge rate is 60 amp

So neither of the above conditions have been met to reset the SOC to 100%

SOC is currently at 100%

If you were to take all the current draw off of the batteries, and let them sit for 24 hours, i think that the voltage would be more in line with the SOC. I also have the same meter, have noticed the same thing, but have relied on the SOC. No problems so far. I have also recently replaced house AGM batts, going back to lead acid regular deep cycle batts. When the inverter charger, is powered up and charging the charge rate, to get to full charge seems to be in line with the draw the Victron is showing. DS

Have you taken a volt meter right at the batteries, not through a panel meter?
Was everything working OK at the time you took your voltage reading at the panel? It wouldn't have been if you were really at 10.4 volts because that is a dead battery, the reefer and other 12 volt electrics would be non functional.

I think your issues, if they indeed exist as described in your post, first started by not having all four batteries the same age and model. This may be the root cause. Second, if it is not, it appears your calculation was wrong, thus the monitor may read 100% but the charger is still seeing a hungry battery bank 60 amps of decay on a 105 amp battery is essentially a dead battery. I have not used a Victron, so am not familiar with using one in practice. If you were using a too low capacity to start, and only charging to a max 100% you may have been habitually undercharging.

I don't understand why the battery monitor is showing a SOC of 100% when the parameters that determine that are not met.

After a charge time of 3 hours and with voltage of 13.62, battery monitor showing a current charge of 43 amps and the battery charger showing a 50 amp charge current I shut down the genny. The monitor still shows a SOC of 100%.

After 30 minutes voltage has dropped to 12.55.

I think George is correct, the batteries have been continuously under charged and I have probably ruined them because I relied on the SOC.

caltexflanc said:

I think your issues, if they indeed exist as described in your post, first started by not having all four batteries the same age and model. This may be the root cause. Second, if it is not, it appears your calculation was wrong, thus the monitor may read 100% but the charger is still seeing a hungry battery bank 60 amps of decay on a 105 amp battery is essentially a dead battery. I have not used a Victron, so am not familiar with using one in practice. If you were using a too low capacity to start, and only charging to a max 100% you may have been habitually undercharging.

Click to expand...

Even if I estimated the used battery capacity as too low and I actually had a capacity closer to 420 amps (4*105 amp) it shouldn't effect the SOC that much. SOC is reset to 100% when the monitor senses the battery charger current has become less than 4% of the battery bank capacity or in my case 14.4 amps. The voltage on the battery bank also has to be above 13.2 volts. Though the voltage finally made it to 13.6 the charge current was still well above the 14.4 amp threshold for the monitor to set the SOC to 100%.

Battery voltage on the battery monitor is 12.52. With a digital volt meter on the terminals of one of the batteries on the house bank is 12.49.

Sounds like something is wrong with that SOC meter, or something wrong with the way it is hooked up. I would not rely on it until sorted. In the mean time, use the classic technique of topping up batts. Call it 100% when amps decay at whatever bulk charge rate voltage is appropriate for your batts.

You have quit charging now at 13.2v? That's too low, still not topped up. Needs to be around 14.5v with amps tapering off.

I don't know what algorithm that SOC thing uses, but if it thinks you have a good bit of capacity left with volts at 10.5, it is seriously missing something in its calculation. It can't actually measure SOC, it derives it from amps in and amps out, but sure as heck ought to look at voltage too!!!

Hopefully your batts did not take much of a hit.

Top them all the way up and also make sure none is getting warm.

timjet said:

I purchased a victron dual bank battery monitor and installed it earlier this year.

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Do you have it setup for 2 banks or just 1? If 2, is it getting wrong information from the other battery?

Ted

When you are taking the voltage reading, are all loads off? If there is any load on, 12.55 is virtually a 100% charged, since the open circuit voltage of a fully charged battery is 12.7. Are your battery monitor and charger both set for AGM batteries?

Here is some helpful guidance from the folks at Trojan regarding charging AGM (VRLA) batteries.

And again when you got that 10.5 volt reading, which is that of a completely, totally deceased battery, was anything working?
Have you taken voltage readings of each individual battery in the bank?

SOC issue

The SOC is not full proof and according to the tech company that installed our new Magnum Inverter this past spring "dont ever rely on this alone"

In the 3500 miles we have put on since March the SOC has only been used as a guide. The bigger problem was the battery temp monitor which caused a few issues based on its tolerances and limits.

Dont blame yourself there are so many issues with battery charging and alternator upgrades and adding solar that one can only address ine issue at at time.

Dont be hard on yourself..

Gerald
Takes Two

I don't have a Victron, but have the Xantex LinkPro. I trust it works similarly, but I could be wrong. My LinkPro sometimes loses its place in the % of charge and needs to be resynced.

Mine was installed incorrectly the first time by the low-paid, amateur installer I hired to do the job. The guy thought he knew what he was doing but he f'ed it up. I had to re-read through every step of this instruction page to make sure it was installed correctly. It wasn't. After cussing over the obvious error, I got over it and forgave myself for messing up the install the first time. After I moved the ground connection, all seemed to fall into place.

Now in the case of my LinkPro, it still loses itself once in a while and needs a FULL recharge and a resync to start over again. Not a big deal, but it's not the perfect SOC meter I thought it would be. I have now concluded that the Balmar SmartGuage paired with one of these Victron or Xantrex SOC meters is probably the best of both worlds. I just can't rationalize spending additional $300 for a % of charge meter that's more accurate than the current SOC meter but it lacks the amps in-out data that I rely upon when monitoring my electron flow rates into and out of my battery bank.

If I was in your position, I'd leave that smart charger on for a week to make sure I had a full charge and then re-synchronize the SOC to the new 100%. Verify all grounds are connected downstream from the shunt. That means no grounds are on the battery neg terminal(s) except the one leading to the shunt. Nothing else connected between the battery neg (-) terminal and the shunt. All grounds are on the terminal block(s) between the shunt and the engine ground. No exceptions.

The voltage is only valid if sitting at rest with no charge or load for 24 hrs or so. It's not really practical to get a good reading when you're onboard your boat using the systems or charging the battery bank. If loads are on, the voltage will read lower than expected for the SOC. If charging has occurred recently, the 'surface charge' can cause the voltage to read higher than appropriate for the actual SOC. As mentioned, if your fridge was running when you read the 10.4V, you might not have actually damaged your battery. It could have been an artificially low reading due to the high load.

Fortunately, quality batteries are more forgiving than we sometimes give them credit for. Hopefully yours are just fine.

My new motto is Charge 'em, use 'em, ...and repeat as needed...then fuggetaboutit!!

No sense worrying about it. I take care of them, but when they die, they die. I'll buy more. If I have to spend $700-1000 every 3-5 years for batteries, who cares? It's less than a few months marina fee. If I beat the 5 year horizon, I'm money ahead. (BTW, my wife knows nothing about this new motto and would probably not agree with it!)

I see somehow I failed to paste in the Trojan link:

Battery Maintenance | Trojan Battery Company

Thanks guys for all you input.
Yesterday I charged the batts for 3 hours to this point:
V = 13.62
I or current going in/out = +43
SOC = 100%
CE or consumed energy = 0
Battery charger amp gauge showed 50 amps


The CE at 0 means that all the amps used by the batteries since the last time the SOC was 100% was replaced ie batteries fully charged.
Of course they were not fully charged as the battery charger was still putting out 50 amps and the I was 43 amps.

So I disconnected the old battery from the house bank and checked it's voltage alone after a couple of hours, it was 11.22. Dead!

I removed this battery from the house bank and charged the remaining three new batteries to a point where the charger amp gauge showed 0 and the I on the battery monitor showed 3.8 amps. This only took about 1.5 hours. The batteries should be fully charged.
I re calibrated the monitor to a bank capacity of 300 AH which should account for the removed battery and reset the SOC manually to 100%

This morning I checked the monitor and this is what I got:
Voltage: 12.24 or about 50% SOC based on voltage alone
SOC 81%
CE 68 amps

It appears to me the battery monitor is simply using the consumed energy CE to derive the SOC. 68 AMPS used out of 300 available AMPS is 78%. Pretty close to the 81% the battery monitor is displaying.

But this is very wrong and doesn't take into account the voltage. Again I know to get the true SOC of a battery it must be unloaded for 24 hrs and a voltage reading at that time will give an accurate SOC. Since when using the boat it's not practical to unload for 24 hours, that's the real value in installing a battery monitor.

Lesson learned:

I relied on the SOC alone to monitor battery condition and this has probably caused me to damage or destroy 3 new batteries by habitually undercharging them.

Last May I checked the condition of the 2 year old battery by fully charging it and checking voltage 24 hours later and though I don't remember it's voltage it was satisfactory. I called the battery manufacturer and got the voltage readings vs SOC.

This of course depends on the battery monitor being installed correctly. Al you posted a site back last year that described in detail the correct installation method and along with the monitor manual I got it installed properly. The last battery negative terminal in line on the house bank is connected to the shunt. The other shut terminal is connected to engine ground and to a terminal block. Connected to the terminal block is the negative lead from a small inverter and the negative lead from the batt charger. There are no sucker leads from any negative terminals.

Just a note, the proper way to wire a bank is to have the negative ground be connected to the last battery in line and the charging current go to the first battery, ie charge and ground on opposite sides of the bank.

From East Penn battery manufacturing co:

AGM Batteries SOC

% Charge Voltage
100 12.8 or higher
75 12.6
50 12.3
25 12.0
0 11.8

Going forward here's how I'll determine SOC:
Charge batteries until the voltage drops to the float stage: 13.4 - 13.6 volts.
Monitor I and Battery charger amp gauge. When they approach 0, the batteries have absorbed as much amps as their able.

Will be changing genny oil much more frequently!!

Sounds like you found the problem. You know what they say, "One bad apple can spoil the whole bunch." Hopefully the rest of the batteries can be revived.

Don't you have a Charles smart charger and shore power at your slip? If so, why not just leave the charger on whenever the boat's in the slip? The charger goes from bulk to absorption to float automatically. Then the batts are fully charged when you arrive. That's what I do with my house bank. I periodically resynchronize the monitor when I return to the boat to reset the monitor's 100% reference. My Xantrex will flash a "synchronize" message on the unit's screen when it's needed.

timjet said:

I purchased a victron dual bank battery monitor and installed it earlier this year. ...

Click to expand...

I don't trust myself to install electrical devices.

FlyWright said:

Sounds like you found the problem. You know what they say, "One bad apple can spoil the whole bunch." Hopefully the rest of the batteries can be revived.

Don't you have a Charles smart charger and shore power at your slip? If so, why not just leave the charger on whenever the boat's in the slip? The charger goes from bulk to absorption to float automatically. Then the batts are fully charged when you arrive. That's what I do with my house bank. I periodically resynchronize the monitor when I return to the boat to reset the monitor's 100% reference. My Xantrex will flash a "synchronize" message on the unit's screen when it's needed.

Click to expand...

Thanks Al, I'll know soon enough if the remaining batts are any good.

I always leave the Charles charger on when in the slip. We're currently on the Chesapeake full time mostly at anchorages until it gets too cold. We've been on the boat since late May relying on the SOC meter to charge the batteries. I think they've been habitually under charged.

timjet said:

Thanks guys for all you input.
Yesterday I charged the batts for 3 hours to this point:
V = 13.62
I or current going in/out = +43
SOC = 100%
CE or consumed energy = 0
Battery charger amp gauge showed 50 amps


The CE at 0 means that all the amps used by the batteries since the last time the SOC was 100% was replaced ie batteries fully charged.
Of course they were not fully charged as the battery charger was still putting out 50 amps and the I was 43 amps.

So I disconnected the old battery from the house bank and checked it's voltage alone after a couple of hours, it was 11.22. Dead!

I removed this battery from the house bank and charged the remaining three new batteries to a point where the charger amp gauge showed 0 and the I on the battery monitor showed 3.8 amps. This only took about 1.5 hours. The batteries should be fully charged.
I re calibrated the monitor to a bank capacity of 300 AH which should account for the removed battery and reset the SOC manually to 100%

This morning I checked the monitor and this is what I got:
Voltage: 12.24 or about 50% SOC based on voltage alone
SOC 81%
CE 68 amps

It appears to me the battery monitor is simply using the consumed energy CE to derive the SOC. 68 AMPS used out of 300 available AMPS is 78%. Pretty close to the 81% the battery monitor is displaying.

But this is very wrong and doesn't take into account the voltage. Again I know to get the true SOC of a battery it must be unloaded for 24 hrs and a voltage reading at that time will give an accurate SOC. Since when using the boat it's not practical to unload for 24 hours, that's the real value in installing a battery monitor.

Lesson learned:

I relied on the SOC alone to monitor battery condition and this has probably caused me to damage or destroy 3 new batteries by habitually undercharging them.

Last May I checked the condition of the 2 year old battery by fully charging it and checking voltage 24 hours later and though I don't remember it's voltage it was satisfactory. I called the battery manufacturer and got the voltage readings vs SOC.

This of course depends on the battery monitor being installed correctly. Al you posted a site back last year that described in detail the correct installation method and along with the monitor manual I got it installed properly. The last battery negative terminal in line on the house bank is connected to the shunt. The other shut terminal is connected to engine ground and to a terminal block. Connected to the terminal block is the negative lead from a small inverter and the negative lead from the batt charger. There are no sucker leads from any negative terminals.

Just a note, the proper way to wire a bank is to have the negative ground be connected to the last battery in line and the charging current go to the first battery, ie charge and ground on opposite sides of the bank.

Click to expand...

The 13.6 volt reading was not the batteries' resting voltage, but was instead the charging voltage. Your SOC meter knew that it was still charging, and also knew that more amperage had been put in than it thought had been taken out, so it displays a 100% SOC. It know it is wrong, but "dead reconning suggests that is where it is. Just like if you were dead reconning in the fog.

Once your batteries are fully charged, it should start to drop the indicated SOC as the batteries are used. Then it will measure how many amps go back in to get back to fully charged (as indicated by the batteries not taking more than a trickle charge), compare that to what was taken out and calculate an efficiency factor for its future use in calculating SOC.

timjet said:

Thanks Al, I'll know soon enough if the remaining batts are any good.

I always leave the Charles charger on when in the slip. We're currently on the Chesapeake full time mostly at anchorages until it gets too cold. We've been on the boat since late May relying on the SOC meter to charge the batteries. I think they've been habitually under charged.

Click to expand...

I didn't realize you were still on your trip! You're living the dream!! WTG.

Now I understand why you can't charge longer. Hopefully now without that bad battery, you'll see more normal bank behavior. Just charge as much as possible...maybe even a night or two in a marina for the electrical power might be worth it to know you're back at 100% for a resync.

I know, I know...that costs money and pilots prefer free!!

>I think they've been habitually under charged.<

AGM die if overcharged perhaps the guesstimates put in the SOC meter charged at too high voltage , or for too long?

Some SOC meters learn the battery banks current capacity , and use that info to charge properly.

Well probably the monitor didn't take into account the bad battery so it eas calculating a SOC based on a higher bank capacity. But what I don't understand is why the monitor didn't take into account the bank voltage when calculating the SOC. 10.8 volts and SOC of 80 %?????

MYTraveler said:

The 13.6 volt reading was not the batteries' resting voltage, but was instead the charging voltage. Your SOC meter knew that it was still charging, and also knew that more amperage had been put in than it thought had been taken out, so it displays a 100% SOC. It know it is wrong, but "dead reconning suggests that is where it is. Just like if you were dead reconning in the fog.

Once your batteries are fully charged, it should start to drop the indicated SOC as the batteries are used. Then it will measure how many amps go back in to get back to fully charged (as indicated by the batteries not taking more than a trickle charge), compare that to what was taken out and calculate an efficiency factor for its future use in calculating SOC.

Click to expand...

Yes I will do that and have been the day or so since I determined there was a problem. Voltage is a good indicator of SOC but only after being unloaded for 24 hrs.
My problem is I have no idea what my bank capacity is. I have 3 105 AH batteries but their condition is unknown and I won't know until I completely recharge them, let them sit for 24 hrs and take voltage readings.

I can't do that right now as we are living on the boat. As Al suggested we will hook up to a marina probably in 3 days at Tangiers Island. They'll get a good complete charge but I still can't unhook them for 24 hrs. That will have to wait until we pull the boat out of the water the end of Oct.

Going forward I'll monitor voltage and recharge at 12.3 volts. I know the unloaded voltage should be higher so I should be safe operating it in this manner. Again without knowing the bank capacity the SOC is worthless.
Also monitoring the amps used and recharging those amps will work, but only if the batts in the bank are in excellant condition. IOW unless the batts are new they will require more amps in to get to fully charged than they use.

Then again the charge rate drops so low at the float stage that the only practical way to fully charge the batts is a day or two at a marina.

Perhaps I'm wrong though.

Tim, I think, with a little help from your friends, you've really got yourself a bit upside down and inside out here, something I am an expert at doing to myself on any number of issues. Do you have the Calder book? Worth a re-read to understand the world of battery charging. Also worth a complete re-read is the manual for both your charger and your battery monitor. Time to forget the past and start fresh.

timjet said:

Well probably the monitor didn't take into account the bad battery so it eas calculating a SOC based on a higher bank capacity. But what I don't understand is why the monitor didn't take into account the bank voltage when calculating the SOC. 10.8 volts and SOC of 80 %?????

Click to expand...

The SOC only calculated the % of charge from the amps out vs. amps in. It's a straight count after synchronizing at a full charge and inputting the AH capacity of the bank...much like a digital fuel flow/fuel quantity counter. It doesn't use battery voltage to compute SOC. That's where the Balmar SmartGuage has an advantage over this type of SOC. The Balmar unit uses battery voltage and other parameters, but not current flow, to calculate SOC. It learns your battery bank and adjusts its capacity over time based upon the actual battery bank charge and discharge performance.

My hunch is that your monitor read the amps going into the bank, but the dead battery stored very few of those amps and also caused a loss in the other batteries connected to it. You saw an artificially high SOC due to that amp count that wasn't being captured. It's like having a leak in your fuel tank as you're counting your fuel volume going into the tank. You stop the pump at what you think should be full, but the fuel has leaked and continues to leak out the bottom. At least you've identified and fixed the leak.

FF said:

AGM die if overcharged perhaps the guesstimates put in the SOC meter charged at too high voltage , or for too long?

Some SOC meters learn the battery banks current capacity , and use that info to charge properly.

Click to expand...

Not in this case. The Victron SOC is not connected in any way to Timjet's charger and has no influence on how the charger functions. It is only connected to the batteries. It just reads amps in and amps out and calculates the effect of that gain or loss on the AH capacity Tim has set for his bank.

Sounds like you're on the right path, Tim. Good to hear you can charge for a few days to top them off.

Do you plan to replace that bad battery with a new one to regain some capacity? If so, maybe putting one in early at the marina stay can give it a good charge to start off. Granted, if the others are low, they will bring the new guy down to their level over time, but at least you've regained some capacity with the addition of the new one.

BTW, are all your house batteries the same size and brand AGM?