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Old 07-10-2018, 06:29 PM   #1
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Help! Battery life!

I set up a battery bank hooked to an Iota DLS-45 power converter and a Xantrex Prowatt 2000 inverter. I have four Duracell 6v golf cart batteries (225 AH). All I have connected is a late-model Frigidaire full-size fridge and I am sometimes running a box fan and white noise maker. I am charging with a Honda EU3000IS generator.

The first charge, I had 24 hours before I had low battery. I let it get all the way to 12.0 volts before recharging. Each charge has been shorter and shorter. I've tried to stay ahead of the batteries discharging since the first time, but it's getting pretty hard. Last charge was 3 hours between full charge and discharged. What's going on?

The batteries are still full on electrolyte. It charges up to 13.3 volts according to display on the inverter (I haven't installed the battery monitor yet).

What's going on? Did I install something incorrectly or do I have defective equipment? I'm only a week into using this system.
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Old 07-10-2018, 07:33 PM   #2
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It sounds like you may be using battery voltage as an indicator of state of charge. That is a bad way to go. Unless you have a battery monitor (with a shunt), you should be using a hydrometer to test the electrolyte.

It is also VERY unlikely that your generator is FULLY charging the battery bank. Do a little Googling to see how a battery charges (the various stages) and not that the final stage (from about 80% to 100%) takes many hours.
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Old 07-10-2018, 07:39 PM   #3
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Yep, what's your battery charger? Be nice to have an amp reading on the battery output at no load and load. A DC clamp-on ammeter (multimeter) is a great tool to have.
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Old 07-10-2018, 09:10 PM   #4
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I have a multimeter here with me. I can measure the amperage going to the batteries when charging if that helps.

5 hours charging with the generator and Iota DLS-45 and only 3 hours before the low voltage alarm doesn't seem right...
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Old 07-11-2018, 09:53 AM   #5
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Quote:
Originally Posted by JDOnTheGo View Post
It sounds like you may be using battery voltage as an indicator of state of charge. That is a bad way to go. Unless you have a battery monitor (with a shunt), you should be using a hydrometer to test the electrolyte.

It is also VERY unlikely that your generator is FULLY charging the battery bank. Do a little Googling to see how a battery charges (the various stages) and not that the final stage (from about 80% to 100%) takes many hours.
What he said with one addition ......

I would strongly suggest that you use a hydrometer to check your batteries even if you do have a battery monitor with shunt.

The battery monitor is a great tool but it cannot measure state of charge.

Once you confirm that your batteries are fully charged using the hydrometer then you can estimate SOC, over time, by watching amps in/amps out of the batteries using the battery monitor.
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Old 07-11-2018, 10:10 AM   #6
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The battery monitor is a great tool but it cannot measure state of charge.

Once you confirm that your batteries are fully charged using the hydrometer then you can estimate SOC, over time, by watching amps in/amps out of the batteries using the battery monitor.
Steve, not sure if you've said previously so apologies if this has been covered. Have you spent time with the Trimetric monitor? I ask as it is VERY tunable. With some time, it can be setup to be pretty accurate indicator of SOC. If not, I believe the manual is available online and might give you some ideas of all the options that can be set by the user to create an accurate and very useful tool.
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Old 07-11-2018, 10:29 AM   #7
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Steve, not sure if you've said previously so apologies if this has been covered. Have you spent time with the Trimetric monitor? I ask as it is VERY tunable. With some time, it can be setup to be pretty accurate indicator of SOC. If not, I believe the manual is available online and might give you some ideas of all the options that can be set by the user to create an accurate and very useful tool.
Yes I have and yes it can, but the only way I am aware of to "tune" is with the assistance of a hydrometer.

I agree that the Trimetric is a great tool. I have one. However, on its own, it cannot measure SOC. It can only estimate it based on amps in/out.

Not trying to be argumentative. Just pointing out that a battery monitor by itself is not going to give you the best performance unless you "tune" or calibrate it with the help of a hydrometer.
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Old 07-11-2018, 11:20 AM   #8
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Not trying to be argumentative. Just pointing out that a battery monitor by itself is not going to give you the best performance unless you "tune" or calibrate it with the help of a hydrometer.
No worries, I generally agree. Only a hydrometer will be completely accurate.

However; I think it is important to understand that using an hydrometer every time one would like to know SOC is simply NOT going to happen (in the vast majority of cases). For example; I probably look at my battery bank SOC 3-4 times per day. I am now lithium but in my last RV, the notion that I would retract one of the slides, walk outside, open the battery compartment, pull the battery tray slides out, remove all the caps (multiple 6V batteries) and use the hydrometer on each cell EVERY time I wanted this information is simply NOT realistic. The reasons to skip this process are nearly infinite - I'm in my pajamas, it's raining, I'm only curious, I don't want to get battery acid on this shirt, it's too hot, it's to cold, etc...

In my opinion, expecting someone to ONLY use a hydrometer will guarantee that he/she will ignore their battery bank and probably end up abusing it. That is certainly not best performance.

I do think it is realistic to properly tune a battery monitor and then validate its information at some interval (using a hydrometer) - maybe once a month. In this way, the user can easily access pretty good information about their battery bank and treat them appropriately.

We may be coming at this from two different angles. I prefer to think that people should and will learn a bit about their electrical system and how to use it. It is possible that another angle is that people generally don't care about this stuff and no matter what they have, are going to abuse it (due to lack of knowledge). Using this latter perspective, I can see that giving them a tool that requires some understanding and tuning and expecting them to use it correctly might be a mistake. The erroneous information might be worse than telling them to use a hydrometer and them just ignoring their batteries. At least then they cannot say "my monitor told me all was well".
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Old 07-11-2018, 11:26 AM   #9
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Not trying to be argumentative. Just pointing out that a battery monitor by itself is not going to give you the best performance unless you "tune" or calibrate it with the help of a hydrometer.
I just read this again and your last sentence stood out. I completely agree - there is no other way to tune the monitor. I hope I have not implied that (anywhere) and apologize if I have.
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Old 07-11-2018, 04:13 PM   #10
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I just read this again and your last sentence stood out. I completely agree - there is no other way to tune the monitor. I hope I have not implied that (anywhere) and apologize if I have.
I think we are in agreement.

The battery monitor is a great tool and relatively easy to use so it is more likely to get used.

However, if you really want to know, with good accuracy, what is going on with your batteries you need to back it with a hydrometer.

Now back to the OP..... What was the question?
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