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Old 12-16-2018, 06:28 PM   #1
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Default How to make sure you have enough battery

We bought our first RV a few months ago for our next trip to Florida this winter. Most of the time, we will be bound docking but I'm wondering how I will be able to manage the battery capacity when we'll be off the grid for a night. Having the furnace shut down in the middle of the night because the battery is dead is probably not something we want to experiment with. I assume that after a while, you learn what you can expect from a 105 Ah battery but until then, how can I make sure I won't have bad surprises in the middle of the night?

At least, I will need to run the 12V fridge and the furnace for the night. Hopefully, we will also be able to watch the TV a few hours and take a shower.

Any tips?

By the way, we have an underhood generator if needed. And the only battery monitoring system is the RV voltmeter.
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Old 12-16-2018, 07:24 PM   #2
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We bought our first RV a few months ago for our next trip to Florida this winter. Most of the time, we will be bound docking but I'm wondering how I will be able to manage the battery capacity when we'll be off the grid for a night. Having the furnace shut down in the middle of the night because the battery is dead is probably not something we want to experiment with. I assume that after a while, you learn what you can expect Teen Killed In Crash Near Little FallsThe 15-year-old crashed his vehicle into a tree Saturday evening.from a 105 Ah battery but until then, how can I make sure I won't have bad surprises in the middle of the night?

At least, I will need to run the 12V fridge and the furnace for the night. Hopefully, we will also be able to watch the TV a few hours and take a shower.

Any tips?

By the way, we have an underhood generator if needed. And the only battery monitoring system is the RV voltmeter.

You had mentioned elsewhere, you were looking at a battery monitor, and that is by far the best way to keep track of the battery SOC.


If you have a full battery when you settle in for the night, you would have avout 80ah of usable power. Compressor frig in coolish weather will be 30-40ah per day, so less than 1/2 that overnight. Furnace we would need to what it is to get some idea.


Big thing is to keep the inverter off, assuming you can do that in your model as it will use power even if you aren't using 110v power. Run the engine if you run the micro on the inverter.



Hot water may or may not need power, TV/DVD will and likely need inverter on.


My guess would be you will be OK overnight, but need to charge the next day and unless you drive a long ways, it will likely be short of full, maybe 90%, same if coming off shore power. That should still be enough for the next night.


Best check would be to shut off everything you can and wait an hour before you check the voltage. If you are then under 12.0v, you are getting close to 20% SOC and running out of power.


Once you get the monitor, it will very easy to know, so if that can be done before you go, it would be well worth the effort. One 105ah battery with a compressor frig can be a challenge.


I went to the Roadtrek site and it appears you have the Suburban propane furnace, as do we. We used about 15-20ah overnight with it running in 40ish degree temps in the past with it, but we keep it pretty warm at 65* most nights. It showed propane water heater so none used there.


You are still looking at making it one night if you are close to full in the afternoon, I think.
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Old 12-16-2018, 10:51 PM   #3
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I really wanted to use a shunt but it seems it won't be possible to install it before we leave. It's already winter here. However, I think I will need to really consider using the kind of sensor you suggested me. Without a monitor, it seems that all you can do is hoping.

Our TV/DVD operate directly from 12V so I should be able to leave the inverter off.

Thanks!
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Old 12-16-2018, 10:59 PM   #4
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I really wanted to use a shunt but it seems it won't be possible to install it before we leave. It's already winter here. However, I think I will need to really consider using the kind of sensor you suggested me. Without a monitor, it seems that all you can do is hoping.

Our TV/DVD operate directly from 12V so I should be able to leave the inverter off.

Thanks!

Good on the inverter, that will save you capacity.


It will be very interesting to see what the battery monitor folks say about using the non shunt sensor. I don't think anyone has tried that to this point. If it is accurate enough, and compatible with electronics, it could really save folks a lot of work sometimes.



Good luck on your trip!
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Old 12-21-2018, 10:02 PM   #5
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We commonly use 40-50 Ah at night running compressor fridge, lights, Cpap, heating, no TV. My guess is you probably be ok for one night at a time. But why not sleep in the van a few nights in the driveway and see how much you use?

I have a Victron monitor with the shunt, but testing even with just the battery level lights or a voltmeter should get you close to knowing how much you use.
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Old 12-22-2018, 02:53 AM   #6
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Knit: I'm about to install the Victron. I'm guessing that you're happy with it?
Yoshimura: Running an old 1997 PW with a single 100AH battery. Just finished camping at the CO River where we were stationary for 3 days (friends did the daily driving in their Jeep). Fridge is 3-way so we were on LP. Cold at night so ran Suburban furnace continually. Primitive battery level indicator dropped from full to 3/4 each night. 100W suitcase solar charged battery during day up to full. Will know more when I get accurate readings from Victron. We don't run TV. Use iPad to watch movies/TV series. Never ran RV engine.

Booster and Knit are spot on. Test and see what you use. From what I've learned on this forum, Booster's observation about 105AH and compressor fridge is a good guage: If I were running one, I would get another 100AH into the system. But who knows. Test her.
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Old 12-23-2018, 06:10 PM   #7
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This is very interesting Info. We have a 2008 Roadtrek Agile. My friend just put some.very high end new batteries in his Sprinter ($3000+) but they hold a massive amount of amps. Not sure what id want to put in ours but the 200 amp stock batteries seem to only last about 24hrs without charging. I dont want to soend $3000 but would like to find a happy medium. I wonder if with solar and a new battery package we could run for 2-3 days without running engine or generator?
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Old 12-23-2018, 08:44 PM   #8
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By the way, we have an underhood generator if needed. And the only battery monitoring system is the RV voltmeter.
Have you considered "topping off" the battery before going to bed by running that underhood generator a while prior to turning in for the night?
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Old 12-24-2018, 06:05 AM   #9
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This is very interesting Info. We have a 2008 Roadtrek Agile. My friend just put some.very high end new batteries in his Sprinter ($3000+) but they hold a massive amount of amps. Not sure what id want to put in ours but the 200 amp stock batteries seem to only last about 24hrs without charging. I dont want to soend $3000 but would like to find a happy medium. I wonder if with solar and a new battery package we could run for 2-3 days without running engine or generator?
Thanks
Max
Do you have a monitor in place to let you know how much power you are consuming? You will have to determine if your current batteries are worn out or if you actually use that much power.

As a for instance, I use one 100 AH battery. I can usually make that last two days with some furnace run time in there. Three days for sure without, assuming no TV, which is normal. 150 watts of solar does fill it up nicely.

I do have an LP fridge, with circuit board. My parasitic drain runs about 8-9 watts with fridge in cooling mode and other monitors and things.

I do tend to be quite frugal with battery power. LED lighting, device charging and a bit of water heating and pumping time, that's about it. Maybe the electric blanket for 30 minutes, drawing about 3+ amps from time to time.
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Old 12-24-2018, 01:21 PM   #10
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Have you considered "topping off" the battery before going to bed by running that underhood generator a while prior to turning in for the night?
Yes, I will definitely do this until I have a better understanding of our consummation.
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