Dry Camping and Batteries

jeffreymhardy · 02-23-2016, 06:47 PM

I know this is not a Sunseeker or even Forest River-specific question, but I always get good feedback here so I thought I would pose it. I'm trying to evaluate exactly what I'm going to be able to do for how long without AC power. Now, I'm only trying to see if I could manage a 2-3 night stay somewhere without power, so I did a test of my fully charged batteries that came with my Sunseeker.

What I had running was a TV, a roku and a hotspot, all totaling 43 watts and .59 amps. I bought a 300 watt inverter which is plugged into one of my 12v outlets with an extension cord feeding those three very small power users.No lights or anything else on other than smoke detector, etc.

After one hour, my battery charge was down to 12.3 v from 12.9 v which, from what I read, is about as low as you should ever let your batteries get.

Are these just the worst batteries ever, or am I missing something here? Yes, I could run my genny and top it off, but that's not something I want to have to do hourly.

Any comments would be appreciated.

flymhi · 02-23-2016, 06:59 PM

What size/type/brand of batteries are you running?

jeffreymhardy · 02-23-2016, 07:09 PM

Well that's a very good question. It's a 2015 Sunseeker 3010ds and it's got two 12v batteries connected in parallel. They have absolutely no brand name on them, I guess they're just the generic batteries Forest River puts in...I'm very willing to replace them with something much better I just don't have any experience knowing what I should be able to expect realistically. An hour for those couple of low power devices seems abnormal but maybe I'm missing something. For example maybe the inverter I'm using creates more drain than I know ? Just haven't ever worked with this kind of thing before. Thanks for trying to help

jeffreymhardy · 02-23-2016, 07:11 PM

Also I'm using a fairly cheap way of actually measuring what's left in the battery...it just plugs into a 12v outlet and has a digital readout. I guess that could be flawed...

JLeising · 02-23-2016, 07:14 PM

.59 amps at 120 volts is actually about 70 watts. Also converts to about 6.5 or 7 amps at 12 volts (adding some for the inverter).
Voltage under load is a poor indicator of battery state of charge. The voltage tables posted on the forum apply to batteries that have "rested with zero load" for 24 hours, I believe. There are monitors that measure and accumulate total charge and discharge amp-hours.
Suspect you have other draws on the battery. Frig control board, CO / propane detector, lights, etc. Could easily be a few amps "with everything else turned off". Non-LED lights are a big drain. Putting the slide-outs out and the jacks down will consume some of your available battery capacity, as, although for a short time, these are large current draws.
If your Sunseeker has the factory dual size 27 house batteries, you should have about 200 amp-hours of battery capacity - or 100 amp-hours to the "50% - try not to discharge below" level.

jeffreymhardy · 02-23-2016, 07:19 PM

Thanks for that maybe I'll do the same test without running the inverter at all and see how fast it drops to that same point with just the "onboard" constant power drains...

jeffreymhardy · 02-23-2016, 07:21 PM

I know this is a newbie kind of question but...you came up with 7 amps...and you said I should have 100 amp hours. Am I being too simplistic to calculate that theoretically I should be able to run that stuff for 14+ hours?

JLeising · 02-23-2016, 07:29 PM

Yes - if the stuff you mentioned is all that is using power, the .59 amps at 120 volts is correct, your inverter is reasonably efficient, and your batteries start fully charged, 14 hours to 50% charge point sounds about right.

jeffreymhardy · 02-23-2016, 07:33 PM

I have one of these: http://www.amazon.com/gp/product/B00...rch_detailpage . I plugged it into AC power, and then plugged the powerstrip that has the items I listed above plugged into it. The .59 amps and 43 watts is what it measured consistently over an hour or so. Does that seem like the right way to measure the actual draw?

jeffreymhardy · 02-23-2016, 07:33 PM

And..thank you again for taking the time to try and help...much appreciated.

RamblerGuy · 02-23-2016, 07:56 PM

I have the same Kill-a-Watt meter and it works well. The readings I get are very close to nameplate wattage for appliances I've tested, and the volt readings agree with my Fluke multimeter. Your amperage and wattage readings should be good.

You may want to put a multimeter directly on the coach batteries. Other loads on the same ciucuit such as lights will affect the reading you get with a plug-in voltmeter.

JLeising · 02-23-2016, 07:59 PM

Don't know the device - seems a reasonable approach, but I don't understand the wattage reading and current reading discrepancy. Maybe it is reading peak current vs rms current? I just don't know. Power (watts) is volts times amps. 120 volts and .59 (rms) amps is about 70 watts. Assuming it is correctly reporting wattage, 43 watts at twelve volts would be about 3.6 amps, maybe 4 to 4.5 amps accounting for the inverter inefficiency. 20 to 25 hours in the previous discussion.

jeffreymhardy · 02-23-2016, 08:12 PM

I've been doing a bunch of reading online about how difficult it is to determine actual drain and remaining battery charge with the kind of cheap measuring device I am using (much less the even cheaper push-button 1/3-2/3-Full monitor that comes on the wall). I'm thinking of ordering a Trimetric 2030RV which will probably be very useful for what I want to do and do a much better job of helping me figure this out.

AlR · 02-23-2016, 08:36 PM

Get a Trimetric 2030RV. Put mine in a few weeks ago. Best investment you can make to moniter your batteries. Guess work removed!

jeffreymhardy · 02-23-2016, 08:52 PM

Yep that's what I just ordered. Seems simple enough to install.

ScottBrownstein · 02-23-2016, 09:00 PM

Quote:

Originally Posted by AlR

Get a Trimetric 2030RV. Put mine in a few weeks ago. Best investment you can make to moniter your batteries. Guess work removed!

x2x2x2x2

Nothing like it. No guesswork, you always know exactly where you stand.

jeffreymhardy · 02-24-2016, 07:09 AM

OK so to connect the Trimetric when I receive, as far as I understand I disconnect the one negative connection in the picture (NOT the interconnect) and connect it to the shunt...and then connect the other side of the shunt back to that negative battery terminal...so that the only path to the negative terminal is through the shunt.

But do I need to change anything on the positive side since (aside from the interconnect) I have leads coming off of both positive terminals?

https://drive.google.com/file/d/0B9v...ew?usp=sharing

https://drive.google.com/file/d/0B9v...ew?usp=sharing

ScottBrownstein · 02-24-2016, 10:14 AM

Quote:

Originally Posted by jeffreymhardy

OK so to connect the Trimetric when I receive, as far as I understand I disconnect the one negative connection in the picture (NOT the interconnect) and connect it to the shunt...and then connect the other side of the shunt back to that negative battery terminal...so that the only path to the negative terminal is through the shunt.

But do I need to change anything on the positive side since (aside from the interconnect) I have leads coming off of both positive terminals?

https://drive.google.com/file/d/0B9v...ew?usp=sharing

https://drive.google.com/file/d/0B9v...ew?usp=sharing

That is correct. I can't see how much headroom you have but someone on a forum made a shunt connector out of 3/4" copper pipe and it hooks directly to the negative post stud and then you just move the negative cable to the shunt output. No additional cables required.

You will need the 3 wires to the shunt (also shown) as well as a power wire for the Trimetric to any positive battery post. If you want to monitor your chassis battery, you run another small wire to it's positive post as well. The Trimetric will tell you that battery's voltage but will not monitor SOC, current in and out of that battery.

jeffreymhardy · 02-24-2016, 10:19 AM

Thanks for that! That's a great idea about the shunt attaching directly to the terminal, and thanks for the photo...that will help

ScottBrownstein · 02-24-2016, 10:25 AM

In addition, think about where you want to put the unit. My Monitor panel is in the bedroom and my first idea was to put it there. Turns out it was much easier to put it right by the entrance, above where the disconnect switch is located. In retrospect, that is a much better place since I can see it from the cockpit and it does indicate things that you want to see in real time, like, engine is running...is the alternator charging the house and how far to I have to go to get back to 100%?

Trust me, you will become a SOC miser, always wanting to see that 100% number again!!!!

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