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Old 09-22-2018, 09:07 AM   #1
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How to check batteries

I read a lot of threads that discuss battery's not being fully charged with generator! Am I to under stand if my generator will never fully charge my house batteries?

Example: If I boondock for several days. And run my generator a couple hours each day, even thou the battery reading is telling me it is at full charge, it is not really "Toped Off"?
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Old 09-22-2018, 11:47 AM   #2
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Depending on what make and model you have, type of batteries and what converter is installed plus your energy usage are all determining factors that you don't supply.
Converters will generally taper off as the batteries get more charged. so the first hour may deliver X amount of charge but the second hour will only deliver Y/X ( a fraction). Batteries are best kept above 50% and the closer to 100% the better.
This is why solar is used so much in RVs. While the combination of generator and converter can give you a quick charge the slow all day consistant charging of solar is much better.
On the last point your battery test should be after 2 hours of resting ( no charging or use) which is pretty hard to get if you are using the rig.
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Old 09-22-2018, 03:12 PM   #3
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Originally Posted by homeless View Post
I read a lot of threads that discuss battery's not being fully charged with generator! Am I to under stand if my generator will never fully charge my house batteries?

Example: If I boondock for several days. And run my generator a couple hours each day, even thou the battery reading is telling me it is at full charge, it is not really "Toped Off"?
When you are on shore power do your batteries charge fully? Do you have an auto start for your generator?
My generator will start if the batteries get low. When they are charged the generator will shut down if no other 'on demand' load is active.
You always have the option to manually run your generator to charge the batteries. If you can read the charging amps, you can watch the rate fall as the batteries top off.
You can always replace your inverter with a smart one.
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Old 09-23-2018, 05:14 AM   #4
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Smart Inverter! So maybe the light is coming on for me. When on shore power my meter is always somewhere around 13.5. So I have a dumb inverter? I have noticed that number being higher but not by a lot maybe 13.7, does it range a lot or go to zero, is that how a smart inverter works? Does this mean when on shore power I am over charging my batteries?
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Old 09-24-2018, 08:09 AM   #5
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Smart Inverter! So maybe the light is coming on for me. When on shore power my meter is always somewhere around 13.5. So I have a dumb inverter? I have noticed that number being higher but not by a lot maybe 13.7, does it range a lot or go to zero, is that how a smart inverter works? Does this mean when on shore power I am over charging my batteries?
A smart inverter is a magic black box to most of us. For technical specs, look at the Magnum MS-2000. 2000W 12VDC Pure Sine Inverter Charger MS Series | Magnum Dimensions
This is a 2K pure sine wave inverter/charger. The charger monitors the charging characteristics of your batteries as they charge and changes the charger output values as needed.
The inverter is smart also and will supplement power to the AC loads connected to it if you exceed the available 30A of shore power. (Yes. A bit complicated.)
To answer your question about voltage range...
Shore or generator charging depends on a few things to be in place. If you will post a signature, similar to mine, with more info about your coach, I will use that to research your wiring schematics.

Rick
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Old 09-24-2018, 11:44 AM   #6
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Smart Inverter! So maybe the light is coming on for me. When on shore power my meter is always somewhere around 13.5. So I have a dumb inverter? I have noticed that number being higher but not by a lot maybe 13.7, does it range a lot or go to zero, is that how a smart inverter works? Does this mean when on shore power I am over charging my batteries?
Unless your power converter is out of adjustment, it shouldn't overcharge your batteries. The 0,2V difference you're seeing may just be the charging circuit cycling on and off, or it could be some device using more or less power as needed. At these voltage readings, I wouldn't worry about it, they're in the normal range.
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Old 09-24-2018, 01:29 PM   #7
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A smart inverter is a magic black box to most of us. For technical specs, look at the Magnum MS-2000. 2000W 12VDC Pure Sine Inverter Charger MS Series | Magnum Dimensions
This is a 2K pure sine wave inverter/charger. The charger monitors the charging characteristics of your batteries as they charge and changes the charger output values as needed.
The inverter is smart also and will supplement power to the AC loads connected to it if you exceed the available 30A of shore power. (Yes. A bit complicated.)
To answer your question about voltage range...
Shore or generator charging depends on a few things to be in place. If you will post a signature, similar to mine, with more info about your coach, I will use that to research your wiring schematics.

Rick

I have a 2000 Itasca Suncruser.
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Old 09-30-2018, 05:03 PM   #8
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I would not worry too much. If your batteries in the morning still have a good charge. In normal use boondocking charging 2 to 4 hours a day, like 2 morning and night even winter using furnace at night we stay charged up. It is a long charge cycle to get to 100% charge near 4 hours constant charge as the last 10% I is tough.

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Old 09-30-2018, 07:37 PM   #9
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The biggest problem with RV batteries is knowing the true state of charge. The battery monitors in most rigs are no better than sticking your head out the window to get a weather forecast; virtually useless. I just installed a Victron BMV-712 and was able to determine that my coach batteries were not doing well and the starter battery isn't doing much better. These are the original batteries and are essentially shot after 3 years and they were never really stressed. The original battery monitor with the 4 LEDs indicated that everything is fine, except you begin to notice that you need to charge them more frequently. One of my two coach batteries has a bad cell and is totally useless. Being in parallel with the other battery, it's really difficult to tell what the true state of charge was.

I have a new tanks and battery monitor system by See Level, a separate battery monitor system, and just ordered an Amp-L-Start by LSL Products that will charge the starter battery while on shore power or when the generator is running. Note: Most RVs do not charge the starter battery while on shore power or while the generator is running. I also have an original equipment battery isolator solenoid that will connect and charge all 3 batteries while driving but keeps the starter battery isolated while boondocking or on shore power unless I press the "battery boost" button to reconnect all of the batteries. This is why the Amp-L-Start is very useful in keeping the starter battery charged, especially if the radio you listen to is powered by the starter battery.

A big problem begins to surface as you consider changing out the coach batteries with very expensive Lithium ion batteries that can be damaged by the alternator charging system, designed to charge lead-acid batteries and is not very sophisticated. Definitely not a good charging system for Li ion batteries. I am now researching how to disable the battery isolator solenoid while the RV is traveling down the road. Of course, the old 3-stage coach battery charger will need to be upgraded to a Li ion charging system. The starter battery will need to stay isolated until you really need a boost and press the battery boost button. It all sounds complicated, and it is somewhat, until you sit down and think this stuff through each camping situation; what is getting charged by what and where does my power really come from? Is my power getting adequately replaced (a BMV can help here)? You definitely don't want to be caught in the boonies with no power to even start your generator or engine.
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Old 09-30-2018, 08:33 PM   #10
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When you read your "battery" voltage, you are really reading the converter (AC to DC) / charger voltage if it is plugged in to shore power or on the running generator. The battery is likely in some sort of charging state, depending how deeply it was discharged. Unless you switch the battery disconnect, you will always read the converter, generator, or some sort of load, such as the smoke and gas detectors. Real battery voltage needs to be a "resting" voltage, disconnected from charge and load for several hours. Now you can estimate your state of charge and condition of the battery. Notice I wrote singular battery. If you have two batteries, they need to be uncoupled in order to get the condition of each one, as one bad battery can drag down the other when combined in parallel. Serial connections are easier to test but much more destructive when one battery starts going south.

Smart chargers automatically adjust their output voltage or current as the battery becomes charged and it's needs change. This is why you very often see 13.6 volts but occasionally you may see 13.2 volts when the batteries are nearing full charge. The charger is really trying to put out 14+ volts but the battery is pulling down the voltage during a deep charge. If you never see 13.2 volts, you may have a problem with the charger or one or both of your batteries which may be just getting tired and need replacing. Voltage alone tells you very little. You need to see how the voltage changes under light, medium and heavy loads. Light loads should have little affect on healthy batteries. As your batteries age, the 75 amp hour capacity, for example, may drop to 50 amp hour capacity, even lower. Eventually they will charge forever yet hold no load capacity, a.k.a. dead battery.
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Old 09-30-2018, 09:12 PM   #11
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Rv house battery notes

RV HOUSE BATTERY NOTES (Partial Reply)

I have a 2004 Winnebago Itasca Horizon with an older 2000W Dimensions Quasi-sine Inverter/Charger. I like it okay. (It's not so dumb, but not so smart either.) One day I will replace it with a pure-sine wave inverter/charger, but not today. I also have 4-100W solar panels to assist with my battery charging.

Note: Smarter chargers are “healthier” for your battery system, but every so often a good “dumb” charger does a better job if you want to manually recondition your battery bank.

Since this thread deals with undercharging and over charging your battery bank, I will comment on that first:

I think it’s possible you are expecting too much from you meter. Here’s an article on measuring your battery State Of Charge (SOC) you need to read to understand how inaccurate your meter can be. (Emphasis on “can be.”)

How accurate is the measuring of a battery state of charge? - Tawaki Battery - Charge your way

* If you are thinking about how fully charged your battery bank is, then you have to consider how accurate your measuring devices are.

In addition, there is a problem measuring SOC if you are using your RV. I.e., your house battery bank is never “at rest” long enough to take a good measurement. That said, I will skip everything you can read about in the attached .pdf and just give you my conclusions:

Don’t worry about what your house battery monitor says above 12.4V or what you solar SOC meter reads above 70%, since neither is accurate most of the time!

* The best way to really know if your charger is able to fully charge your battery bank, and the only time to trust your voltage meter, is to let the system charge for 1-2 days and then let that battery bank come to rest for 4 hours before your read your voltage meter. …My guess is that if you do this your meter will read 100% or be in the “full green range”.

Note: For days I was going nuts taking measurements off my Power Management Panel in volts and then looking at the voltage chart (see attached) to determine if my battery bank was fully charged. This not how to do it!

And to make matters more confusing, I was trying to compare that voltage information (and voltage chart) to my Solar Panel SOC metering device that shows its SOC in terms of % charge… which never gets over 70% most of the time.

Why? Because, as indicated earlier, I was using my RV (with various devices putting a load on the battery bank, and/or I was looking at this solar SOC meter during the day when the solar panels were pumping amps into the battery bank. So nothing about my battery bank was “at rest.”

* You know what I think you need to do with your volt meter on your Power Management Panel? Answer: JUST IGNORE IT when it reads over 12.4 volts -- and pay attention to it when it drops under 12.0 volts!

* To read more on this subject you can download the attached .pdf as I don't want to bore everyone. However, in this .pdf I do list other possible reasons (thoughts of mine) in the event a charging system is underperforming.


Good RVing!

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