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Old 09-28-2014, 08:10 AM   #1
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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 AGMs 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 Ive ruined all my AGM batteries by relying on the battery monitor.
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Old 09-28-2014, 08:22 AM   #2
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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?
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Old 09-28-2014, 08:35 AM   #3
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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.
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Old 09-28-2014, 08:42 AM   #4
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A quick update;
The SOC shows 100% and the ammeter on the battery charger is showing 75 amps output.
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Old 09-28-2014, 08:43 AM   #5
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Are all the grounds running through the shunt? That would be the only way a load wouldn't show.
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Old 09-28-2014, 09:32 AM   #6
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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.
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Old 09-28-2014, 09:40 AM   #7
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Quote:
Originally Posted by meridian View Post
Are all the grounds running through the shunt? That would be the only way a load wouldn't show.
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%
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Old 09-28-2014, 10:11 AM   #8
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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
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Old 09-28-2014, 10:18 AM   #9
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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.
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Old 09-28-2014, 11:59 AM   #10
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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.
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Old 09-28-2014, 12:14 PM   #11
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Quote:
Originally Posted by caltexflanc View Post
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.
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.
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Old 09-28-2014, 01:12 PM   #12
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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.
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Old 09-28-2014, 03:13 PM   #13
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Quote:
Originally Posted by timjet View Post
I purchased a victron dual bank battery monitor and installed it earlier this year.
Do you have it setup for 2 banks or just 1? If 2, is it getting wrong information from the other battery?

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Old 09-28-2014, 03:22 PM   #14
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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?
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Old 09-28-2014, 09:29 PM   #15
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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..

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Old 09-28-2014, 09:53 PM   #16
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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!)
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Old 09-28-2014, 09:59 PM   #17
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I see somehow I failed to paste in the Trojan link:

Battery Maintenance | Trojan Battery Company
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Old 09-29-2014, 07:31 AM   #18
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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.
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Old 09-29-2014, 07:41 AM   #19
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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
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Old 09-29-2014, 07:51 AM   #20
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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!!
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