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Onan Generator - how long to fully charge batteries?

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Posted 2017-12-03 5:06 PM (#170872)
Subject: Onan Generator - how long to fully charge batteries?


Posts: 16

Location: Bend, Oregon
I have a 2016 Exiss LQ trailer that I had the dealer install an Onan in the hay rack. I bought the trailer new in 4/16, and the generator was installed before I brought it home. I have had nothing but problems with keeping the batteries charged. I would run the generator for two hours, the indicator said the batteries were charged, and then by morning (with only using interior trailer lights) the batteries were dead. The dealer has been offering suggestions for the past 18 months, but finally took it in and ran tests - it appears that the Generator was pulling from the batteries when not in use. I also had a faulty toggle switch for the horse area and back exterior light, and those lights would come on randomly. So, all of that is supposedly fixed, and I have the trailer back home.

This morning I ran the generator for 1.5 hours, lights indicated a full charge on batteries, and left the radio, interior trailer lights, the outside door light, and the horse/back area lights on, just to see how long I could run before the generator wouldn't start. It's been 6 hours, and I'm down to two red lights, the generator did start, but I think another hour, and it won't.

How long should fully charged batteries last? I hear people going for two-three days on fully charged batteries, and surely they must be using some lights, water pump, etc. I don't think mine will make it 8 hours - but I know I have a lot of things turned on. Tomorrow, I will charge the batteries for two hours (is that long enough for a full charge?) and just turn on the interior lights and see how long it lasts.

The Trailed is plugged in to power at the house, so everything stays charged. But we purposely didn't plug it in so we could test it and see how often I need to charge it. My previous trailer was a Trails West with a built in Onan, and that trailer could go for a couple of days without running the generator. I am really disappointed with my current trailer. When I take it dry camping, I have to make sure I'm close enough to my friends trailer to jump it if my batteries go dead, and I worry the whole time about whether I'm going to get the jacks up to hook up again. Total PITA. Any help/suggestions/critiques are welcome!

Thanks in Advance.

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Posted 2017-12-04 11:54 PM (#170893 - in reply to #170872)
Subject: RE: Onan Generator - how long to fully charge batteries?


Posts: 3833
Location: Vermont
Do you have electric over hydraulic jack stand(s) or straight electric jack(s)?...Because they pull some amps when they are being deployed

You need to do some wattage calculations on your unit to determine where your major electrical draws are  occurings.

Also, are these the same batteries that you ran to the point of lights out?


Edited by PaulChristenson 2017-12-04 11:55 PM
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Posted 2017-12-05 9:50 AM (#170895 - in reply to #170872)
Subject: RE: Onan Generator - how long to fully charge batteries?

In my trailer we converted all the lights over to led and that helped. I can go to an event for a couple of days without to many problems as long as we keep things to a minumum in the trailer and don't spend a lot of time with all the lights on. I normally run my generator for a few hrs in the evening mainly to cool it down at the end of the day and sometimes so the kids can watch a movie. My Onan 4000 is up on the hay rack as well but it has its own starting battery. Keep in mind we spend most of our time outside and conserve power very well.
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Posted 2017-12-06 10:48 PM (#170906 - in reply to #170872)
Subject: RE: Onan Generator - how long to fully charge batteries?


Posts: 25
Hello I put a Post on about solar panels. take a look at it. I would not be with out them.

Thank You.
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Posted 2017-12-07 12:20 AM (#170909 - in reply to #170872)
Subject: RE: Onan Generator - how long to fully charge batteries?


Posts: 85
Location: Calgary, Canada
Indicator lights are generally not a very good way to determine the battery state of charge. The best way is to measure the specific gravity of the electrolyte in the battery ... although this is not easy or often practical. The next best way it to measure the stabilized voltage of each battery and compare it to a state of charge chart. Voltage stabilization for a lead acid battery can take 12 to 24 hours, so to determine the true state of charge, you must give the battery time for the voltage to stabilize after charging or after use. For example, a 12 volt battery at 100% state of charge should have a stabilized voltage of 12.73 volts. The same battery at 50% state of charge has a stabilized voltage of 12.10 volts. For 6 volt lead acid batteries, stabilized voltages are 6.37 volts at 100% state of charge and 6.02 volts for 50% state of charge. For maximum battery life, the battery should not be taken below a 50% state of charge. Fully running down lead acid batteries can result in dramatically reduced lifespans (reduced numbers of cycles).

And discharging batteries and not charging them right away can lead to battery sulfation, which also reduces the battery life span (again dramatically).

Battery maintenance is also an important aspect of getting good life out of your batteries. Maintenance includes keeping the electrolyte at the proper level using only distilled or de-mineralized water, keeping the battery terminals clean and keeping the batteries in a full charged state when your trailer is being stored. Life spans on batteries can be quite variable based on the number of cycles they are subjected to, depth of discharge and how good of maintenance they receive. Lead acid deep cycle battery life can be more than 6 years or as short as 1 year depending how you treat them.

Now that your wiring problems have been sorted out, I suspect that you now have a battery problem and NOT a generator problem. You can check your battery condition by fully charging them (I prefer to use a stand alone smart charger rather than the LQ built in battery charger). Once they are fully charged, let the voltage stabilize for 12 to 24 hours with no load on the batteries. Then record the stabilized voltage of each battery and compare it to a battery state of charge chart. In a full charged condition, the batteries should be at or above the 100% voltage rating. If your batteries are at less than the 100% voltage rating, they are likely sulfated and are not capable of accepting a full charge.

If you are not so handy, you can take your batteries into a battery shop / auto shop and have them professionally load tested to determine their condition.

As PaulChristenson indicated, your batteries need to be adequately sized to the amount of load you are putting on them. Batteries are rated in Amp-Hours which is a measure of their capacity. Entry level batteries (lighter, less lead and acid) typically have lower Amp-Hour ratings. Higher priced batteries are typically heavier (more lead and acid) and have higher Amp-Hour rating. You need to match your battery capacity to your usage requirements.

As ckkoch09 indicated, changing your frequently used lighting to LED will help to reduce your electrical requirement and prolong your battery life.

And as hitmis indicated, solar panel(s) can also add to your battery capacity by keeping them at a higher state of charge ... another good idea.

So in summary, I don't believe that you have a generator problem ... rather I suspect a battery problem due to sulfation.

PS - having a generator without having dedicated generator starting battery really limits your options. If it is possible, I would consider having a dedicated generator battery installed.

Regards, 3CW

(Battery Chart.JPG)

Attachments Battery Chart.JPG (70KB - 0 downloads)
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