Battery giving half AH

[Sailingbluew]

Can anyone figure out what could causenof only 150 amps useable with current setup?

4 Lifeline Batteries GPL-6CT AGM Battery 300AH. these are 6V.
1200AH which is 600AH at 12V. I should be able to use half so 300AH, but it seems like I'm getting less than 150AH useable even with engine running for 4-5 hours with a 120 amps alternator.

The batteries with easy access had 6.19 and 6.18V and one of the inaccessible batteries had 6.25V at the same time, measured directly at the batteries at night.


Is it possible to install batteries the wrong way so they get charge but not giving any output?

Do anyone notice something off about the wiring? They do produce 12V, so that part seems fine.


Previous owner installed. They should be around 2-3 years old.

[Dockhead]

You've got 600AH of nominal power at 12V, so 300AH usable is about right if you cycle the batteries between 50% and 100% as you're supposed to.

You should have 12.78V open circuit (no loads, rested with no loads for several hours) when the batts are fully charged. And 12.18 when they are at 50%. That's when you should start charging them, at the latest.

Here's the manual for the batts: https://lifelinebatteries.com/wp-con...al-5-06-19.pdf


Note that it may take many hours of charging to get to 100%, as the charge acceptance of lead batteries goes WAY down at about 85%. And how is your alternator regulated? If it's not regulated to give a proper absorption charge, it may never get the batteries to 100%.

[Sailingbluew]

Originally Posted by Dockhead

You've got 600AH of nominal power at 12V, so 300AH usable is about right if you cycle the batteries between 50% and 100% as you're supposed to.


You should have 12.78V open circuit (no loads, rested with no loads for several hours) when the batts are fully charged. And 12.18 when they are at 50%. That's when you should start charging them, at the latest.

The problem is that I don't have 300 AH, I have about 150 AH before I reach around 50% according to my renongy battery monitor.

[Dockhead]

Originally Posted by Sailingbluew

The problem is that I don't have 300 AH, I have about 150 AH before I reach around 50% according to my renongy battery monitor.

There are two possible things going on here:


1. The battery monitor is not reading correctly. This is a very common problem. You should evaluate state of charge achieved by resting voltage, not AH put into the battery.


2. The batteries are approaching end of life. Also very common. Reduced capacity is the sign. With almost worn out batteries, you will get a high voltage very quickly, and then voltage will collapse with much less AH out than you would expect.


3. Both.

[S/V Illusion]

If connected in parallel, the voltage should be equal on each. The only reason for disparate voltage reading is a high resistance connection (s).
Are the readings you cited taken when interconnected?

Another fundamental question - How old are these batteries?

[hlev00]

This article may be useful. The website also has lots of other great information, particularly around how critical it is to charge AGM batteries completely after each discharge

https://marinehowto.com/programming-a-battery-monitor/

[Dockhead]

Originally Posted by S/V Illusion

. . .

Another fundamental question - How old are these batteries?

He said 2-3 years.


I've seen lead batteries die faster than that.

[Sailingbluew]

Originally Posted by S/V Illusion

If connected in parallel, the voltage should be equal on each. The only reason for disparate voltage reading is a high resistance connection (s).
Are the readings you cited taken when interconnected?

Another fundamental question - How old are these batteries?

The voltage is a little lower on battery 1 and 2 then 3 and 4. I checked the voltage directly at the battery terminals. I didn't remove any battery cables. They are under the sink and access is difficult. By interconnected I assume you mean still plugged together by cables, then yes

[wholybee]

What is important to realize here is that AGM batteries can be damaged and have a very short life if not properly maintained and charged. That sounds like what is going on here. They MUST be fully charged minimum once per week. And by fully charged, that is 100%, not 97%. If you only charge to 97%, then that will over time become the new 100%. And that repeats until you only have half of the advertised capacity.

This is very difficult to do with Solar, and if charging by alternator would probably take 8 hours with a bank your size from 50% to 100%.

The ONLY way to know if the batteries are good is to take them out and test them one at a time. (below is a DIY test for a 300Ah 6v battery)
1) Charge a battery to full.
2) Connect a load that will draw about 15A at 6V. Use a meter to be sure. This Might be hard to find something that will work.
3) Time how long until the voltage reaches 5.25V
4) Hours that takes x 15 is the capacity of the battery. If the battery is good, it should take about 20 hours.

The good news is that Lithium is now pretty cheap. A 300Ah Lithium will give you the same 300Ah usable, and be much smaller and weigh a ton less. I 460Ah would be a nice upgrade, still smaller and lighter.

[PippaB]

To me this could be a battery problem, an installation problem, or a configuration problem, and without knowing more it is hard to chase.

1. Where is the shunt installed? - Is it "seeing" all of the current? Use an amp clamp to compare current reading from the shunt to real world. Is the shunt value configured properly in the monitor?
2. What is the capacity listed in the battery monitor? Did the installer get this wrong and put in 300Ah? Press and hold the "OK" button for three seconds to get to the settings screen and see what capacity is listed for the batteries.

If you are relying on the monitor to tell you you are getting less than expected then first step is to confirm that everything about the monitor, its installation, and its configuration is correct. Only after that will you have the knowledge about where to chase next (if anywhere).

PS - if you tell us where in the general part of the world you are located you might find one of us nearby who would be willing to come down and take a look. I know I would be happy to grab my meter and assist if it was within an hour's travel. [and yes, I know my own location is not posted, but happy to disclose when needed]

[Fuss]

Originally Posted by wholybee

What is important to realize here is that AGM batteries can be damaged and have a very short life if not properly maintained and charged. That sounds like what is going on here. They MUST be fully charged minimum once per week. And by fully charged, that is 100%, not 97%. If you only charge to 97%, then that will over time become the new 100%. And that repeats until you only have half of the advertised capacity.

This is very difficult to do with Solar, and if charging by alternator would probably take 8 hours with a bank your size from 50% to 100%.

The ONLY way to know if the batteries are good is to take them out and test them one at a time. (below is a DIY test for a 300Ah 6v battery)
1) Charge a battery to full.
2) Connect a load that will draw about 15A at 6V. Use a meter to be sure. This Might be hard to find something that will work.
3) Time how long until the voltage reaches 5.25V
4) Hours that takes x 15 is the capacity of the battery. If the battery is good, it should take about 20 hours.

The good news is that Lithium is now pretty cheap. A 300Ah Lithium will give you the same 300Ah usable, and be much smaller and weigh a ton less. I 460Ah would be a nice upgrade, still smaller and lighter.

Yes, Do this test and then get yourself some lifepo4 if they don’t pass. If they do pass then sell them and get yourself some lifepo4.

[Sailingbluew]

Originally Posted by PippaB

To me this could be a battery problem, an installation problem, or a configuration problem, and without knowing more it is hard to chase.

1. Where is the shunt installed? - Is it "seeing" all of the current? Use an amp clamp to compare current reading from the shunt to real world. Is the shunt value configured properly in the monitor?
2. What is the capacity listed in the battery monitor? Did the installer get this wrong and put in 300Ah? Press and hold the "OK" button for three seconds to get to the settings screen and see what capacity is listed for the batteries.

If you are relying on the monitor to tell you you are getting less than expected then first step is to confirm that everything about the monitor, its installation, and its configuration is correct. Only after that will you have the knowledge about where to chase next (if anywhere).

PS - if you tell us where in the general part of the world you are located you might find one of us nearby who would be willing to come down and take a look. I know I would be happy to grab my meter and assist if it was within an hour's travel. [and yes, I know my own location is not posted, but happy to disclose when needed]

I installed the battery monitor and I set it to 600 AH, but at 470 or something the battery is at 12.3-12.2. there is a difference between shunt reading and multimeter readings of maybe 0.1V. I'm only running refrigerator 24/7, starlink a few hours a day, charge my phone and laptop sometimes and a few LED lights+ anchor light. I'm getting 2200 watt from solar (Total 400 watt.panels) and I'm maybe breaking even each day.

I'm in Mexico, sea of Cortez

[PippaB]

I take it that means 2200Wh/day from solar? Which is about 170Ah/day from solar (for a 12V system)?

Then I would guess that you are really running from 75% SOC to 50% (or so) every day, and if the monitor is resetting to 100% then the reset configuration is not right. Only way to know would be to get the batteries up to ~14.4V and hold them there until charge current reaches about 6A. Only then can you say you got to 100% SOC and watch what happens after that. If you are not getting to full absorption voltage and low tail current then the batteries are not getting full - which is to be expected if usage out and charge in are about equal (and it sounds like they are).

[Sailingbluew]

Originally Posted by PippaB

I take it that means 2200Wh/day from solar? Which is about 170Ah/day from solar (for a 12V system)?

Then I would guess that you are really running from 75% SOC to 50% (or so) every day, and if the monitor is resetting to 100% then the reset configuration is not right. Only way to know would be to get the batteries up to ~14.4V and hold them there until charge current reaches about 6A. Only then can you say you got to 100% SOC and watch what happens after that. If you are not getting to full absorption voltage and low tail current then the batteries are not getting full - which is to be expected if usage out and charge in are about equal (and it sounds like they are).

Charge in and out are about equal yes, but I was motoring for 5 hours a few days ago so now the solar is even going into float stage.

So the batteries cannot be wired wrongly and consequently I'm only using battery 1 and 2? It do look like they had outside help for the installation, it looks neat.

I posted my battery wire drawings in the first post. It is not possible to get a good photo of the battery area unfortunately.

[PippaB]

The wiring diagram looks correct. 1 and 2 are wired in series with each other, as are 3 and 4, and then 1/2 is wired in parallel with 3/4. So you should have full capacity available. Did you get the same behavior the day after you motored for five hours? If the solar goes to float (after a reasonable tail current is achieved) then the batteries may have spent too much of their life at PSOC (partial state of charge) and the only way to know would be to do a capacity test as wholybee describes.