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Author Topic: Boondocking battery charge. Am I nuts, or...?  (Read 1807 times)

cliffb

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Boondocking battery charge. Am I nuts, or...?
« on: March 10, 2018, 08:25:35 AM »
So, I'm dry camping. I have two Renogy AGM 100ah grid batteries in parallel. I am at about 9000 ft altitude. 50watt solar on top of the tt and another 100 watt panel on the ground.  Small 700 watt gennie.  Charge these up to 13.5 volts, but by morning I am down to 12.1 12.2. I run lights (led), furnace, 20" tv/DVD  (claims 30watt max usage), radio (50watts x 2 channel).  The question is this; I run all these things in the mix throughout the day and evening, but before I shut everything down I am at about 13.5v. Should I be getting more than barely one night out of this battery bank? It's seems like I should. Does the furnace really use that much juice overnight? Does this sound like a bad wiring job?  Any thoughts would be appreciated.
Thanks
Cliff , My dear wife and little Sophs.
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Flagstaff, AZ

OBX

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Re: Boondocking battery charge. Am I nuts, or...?
« Reply #1 on: March 10, 2018, 08:51:47 AM »
Your battery is rated in amp hours.  It may easier to add or factor what each device is drawing in terms of amps to keep your math straight .  You have other drains on power as well like the refrigerator, detectors, water pump, lights, etc.

You may also be using power at a higher rate than you are charging the batteries.

kdbgoat

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Re: Boondocking battery charge. Am I nuts, or...?
« Reply #2 on: March 10, 2018, 09:21:27 AM »
Your big battery drain is the furnace. The furnace motor draws quite a bit of power.
I know you believe you understand what you think I said,
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Back2PA

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Re: Boondocking battery charge. Am I nuts, or...?
« Reply #3 on: March 10, 2018, 09:31:46 AM »
Does the furnace really use that much juice overnight?

The short answer, as kdbgoat says, is yes, furnaces are huge power hogs. The only way to really know is have a power out vs power in meter such as a Trimetric. Short of that you can do a calculation as OBX suggests. I'd start with the furnace, With a stopwatch time the blower cycle so you know how long the blower runs in an hour. Using the rated amp draw of the blower you can come up with power usage over a given period of time. The 30 watt TV doesn't sound like much (I'm assuming this is a 120V TV), but 30 watts at 12.5V = is about 2.5 amps. Watch for 4 hours and you've used almost 10% of your available battery power (100A + 100A, 50% minimum discharge).

Your 150 watts of solar panels probably produce around 10A peak (pointed properly with both panels tilted) so I'm guessing on an average day your panels do not produce enough to bring your battery bank all the way back from 12.1 volts to fully charged. I'm guessing it would take 1.5-2 days, but others with more solar experience can weigh in on that and my other math.

before I shut everything down I am at about 13.5v.

At 13.5V you're not reading true battery voltage, either you're reading charging voltage from the solar or genset, or you're reading the surface charge from a recently charged battery. To get a true reading all charging sources need to be removed and you either need to wait perhaps 30 minutes or put a slight load on the battery for a few minutes, then read the voltage. A fully charged 12V battery reads 12.7 volts.
« Last Edit: March 10, 2018, 09:47:35 AM by Sun2Retire »
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kdbgoat

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Re: Boondocking battery charge. Am I nuts, or...?
« Reply #4 on: March 10, 2018, 09:37:04 AM »
Another thing to consider is ensuring that your batteries are truly fully charged. Here's a good lesson on that:

https://handybobsolar.wordpress.com

Go to the battery charging puzzle.
I know you believe you understand what you think I said,
But I am not sure you realize what you heard is not what I meant

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garyb1st

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Re: Boondocking battery charge. Am I nuts, or...?
« Reply #5 on: March 10, 2018, 03:29:22 PM »
Another thing to consider is ensuring that your batteries are truly fully charged. Here's a good lesson on that:

https://handybobsolar.wordpress.com

Go to the battery charging puzzle.

How much confidence do you have in this guy?   Lot's of good information ways to save $$$ if his information is correct.   
Gary B1st

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PJ Stough

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Re: Boondocking battery charge. Am I nuts, or...?
« Reply #6 on: March 10, 2018, 03:33:25 PM »
I havent read Handy Bob's blog lately, but I believe he is pretty knowledgeable when it comes to solar.  I also believe in the last couple of years he has warmed up to the idea of using MPPT controllers.
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Lou Schneider

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Re: Boondocking battery charge. Am I nuts, or...?
« Reply #7 on: March 10, 2018, 06:36:59 PM »
I agree with what HandyBob says, it makes perfect sense for wet cell batteries.

Bob's talking to people who will actively manage their batteries while the RV manufacturers build towards set-and-forget, minimum maintenance operation.

I haven't been too involved with solar, but the points he makes about placing the solar controller close to the batteries for more accurate charging (not dropping out of bulk charging too soon) accurately mirrors what I've seen using an RV converter with the Progressive Dynamics' Charge Wizard and by manually controlling the charging voltage.

His battery charging voltages jibe with what Trojan specifies on their data sheets.  Although you have to be careful to reduce the voltage down to 13.5 volts float once the batteries reach full charge - don't keep it at 14.8 - 15 volts or you'll lose lots of water.

And AGM batteries are a special case - in this case you have to keep the charging voltage lower because there's no way to replace water that will be lost by charging at higher voltages.
« Last Edit: March 10, 2018, 06:55:56 PM by Lou Schneider »

garyb1st

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Re: Boondocking battery charge. Am I nuts, or...?
« Reply #8 on: March 11, 2018, 03:18:34 PM »
Lou, I'm not familiar with the Progressive product.  Is this a DIY install and how much if any day to day management is involved?  Also, when I google Progressive Dynamics Charge Wizard a number of options come up with a significant price difference.  Low of about $25.00 to just under $250.00.  I'm one of those RVers that have spent way too much money on batteries.  What do you recommend?
Gary B1st

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Lou Schneider

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Re: Boondocking battery charge. Am I nuts, or...?
« Reply #9 on: March 11, 2018, 10:55:13 PM »
Hi Gary ...

Progressive Dynamics was the first company to come out with an electronically regulated converter in the 9100 series.  The Charge Wizard adds microprocessor controlled multi mode battery charging to the converter.  Originally the Charge Wizard was a separate pendant that plugged into the converter, later it was included internally in the 9200 and 4600 series converters.

The original setup is still being offered with the external pendant for the 9100 series converters, without the Charge Wizard they're a very good single stage 13.6 volt converter.  The Charge Wizard pendant ($25) makes it into an intelligent multi-stage charger with bulk, absorption, float and storage modes that can also be manually selected via a pushbutton on the pendant.

Progressive's 9200 series converters include the Charge Wizard internally and it controls the output voltage just like the 9100 series with the Charge Wizard.  However, there's no way to manually select what mode you want unless you buy an external control pendant ($17), which is just a switch and an LED.

They also make their 4600 series Upgrade converters as a direct drop-in replacement for the older Magnetek chassis.  These include the Charge Wizard but do not offer a way to manually select the different modes.

Any of these will do a better job managing your batteries than a single stage converter.  They pretty much run themselves, but keep in mind, they're only active when you're on shore power or running the generator.

I did some fooling around when I first got my 9100 series converter and I was able to add a manual voltage control to the Charge Wizard pendant to let me set whatever output voltage I want, from about 11 volts to over 16 volts.  This primarily lets me boost the charging voltage when I'm running the generator to push lots of current into the batteries and minimize the run time.  A secondary reason is to let me make sure my batteries are fully charged according to the manufacturer's specifications when I'm on shore power.  But like I said above, this means you have to proactively manage the charging cycle and make sure the batteries don't run low on water. 

Using the Charge Wizard, and occasionally running higher voltages on a generator, I'd have to add water to the batteries every week or two when I was boondocking and moving lots of power in and out of the batteries.  But when I was on shore power and not actively using the batteries, they'd use little or no water for months at a time.

In the 9200 converters, the Charge Wizard is installed internally so the same control pins aren't brought outside the box.  I don't have a 9200 converter, so I don't have any idea how, or if, it can be modified for manual voltage control.

https://www.progressivedyn.com/rv/power-converters/






« Last Edit: March 11, 2018, 11:53:08 PM by Lou Schneider »

garyb1st

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Re: Boondocking battery charge. Am I nuts, or...?
« Reply #10 on: March 12, 2018, 12:54:42 PM »
Thanks Lou.  I'm pretty sure we have a WFCO 3 stage converter.  It seems to work fine, and will bring the batteries to about 13.6-7 when plugged in to the house 110 power.  Will an external control pendant work with a WFCO?  If not, I'll most likely wait until I return from Alaska when I'll reevaluate how much money I want to continue spending on my new(er) money pit. 

Gary
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Gizmo

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Re: Boondocking battery charge. Am I nuts, or...?
« Reply #11 on: March 12, 2018, 01:29:14 PM »
How much confidence do you have in this guy?   Lot's of good information ways to save $$$ if his information is correct.

His material is quite wordy and it is clear he has an ax to grind, but let that not diminish the validity of his material on solar, he really does know his stuff and the information is sound.  Another excellent source and easier to follow as it is straightforward is this http://www.jackdanmayer.com/rv_electrical_and_solar.htm
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Lou Schneider

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Re: Boondocking battery charge. Am I nuts, or...?
« Reply #12 on: March 12, 2018, 01:46:15 PM »
Thanks Lou.  I'm pretty sure we have a WFCO 3 stage converter.  It seems to work fine, and will bring the batteries to about 13.6-7 when plugged in to the house 110 power.  Will an external control pendant work with a WFCO?

No the Charge Wizard is proprietary to Progressive Industries Dynamics converters.

Bringing the batteries to 13.6 - 13.7 is standard for most stock converters, the point Handy Bob makes is that level is NOT fully charged according to Trojan and other battery manufacturers.  Fully charged requires 14.7 - 15 volts for several hours, until a hydrometer test indicates the electrolyte is fully saturated, then reducing the voltage.   However, 13.6 - 13.7 is the highest you can go without keeping track of the battery water levels, as the higher voltages WILL use water.
« Last Edit: March 13, 2018, 12:11:19 PM by Lou Schneider »

ChasA

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Re: Boondocking battery charge. Am I nuts, or...?
« Reply #13 on: March 13, 2018, 07:57:20 AM »
A minor correction. The company that makes the charge wizard is Progressive Dynamics.  Progressive Industries is a different company.
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Lou Schneider

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Re: Boondocking battery charge. Am I nuts, or...?
« Reply #14 on: March 13, 2018, 12:10:35 PM »
Thanks, Chas!

John From Detroit

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Re: Boondocking battery charge. Am I nuts, or...?
« Reply #15 on: March 13, 2018, 05:09:12 PM »
One night of furnace use on 100 AMP hour pair (200 total) sounds about right to me.

As many have said. Furnace Takes a lot of power.

More battery may help but you will also need more solar more than likely to re-charge by sun
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arcticfox2005

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Re: Boondocking battery charge. Am I nuts, or...?
« Reply #16 on: April 18, 2018, 03:42:28 PM »
Try something new - turn off the furnace!!! In over 20 years of RVing in pickup camper, fifth-wheel, Class A, and now Class C, we have NEVER felt the need to have the furnace on at night. This includes 2 trips to Alaska, late enough in the season that as we were going north up the Alcan, everybody in the world was headed south.

Bill

UTTransplant

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Re: Boondocking battery charge. Am I nuts, or...?
« Reply #17 on: April 18, 2018, 04:46:50 PM »
Try something new - turn off the furnace!!! In over 20 years of RVing in pickup camper, fifth-wheel, Class A, and now Class C, we have NEVER felt the need to have the furnace on at night. This includes 2 trips to Alaska, late enough in the season that as we were going north up the Alcan, everybody in the world was headed south.

Bill
We are sitting in a campground in Iowa waiting for our household goods to be delivered to our new house. Tonight it wonít be too cold, maybe 21. Of course it never got above freezing today with an ugly snowstorm going on. Tomorrow night it will be 16 with a high in the low 30s, mostly cloudy skies. If we didnít run the propane heater we would not have water since we would freeze up. We are good to 25 without the propane heater, but lower than that we need it. The electric heater we have doesnít do a bit of good for the tanks though it can keep the interior nice and toasty.
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Frank B

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Re: Boondocking battery charge. Am I nuts, or...?
« Reply #18 on: April 22, 2018, 05:15:13 PM »
Try something new - turn off the furnace!!! In over 20 years of RVing in pickup camper, fifth-wheel, Class A, and now Class C, we have NEVER felt the need to have the furnace on at night. This includes 2 trips to Alaska, late enough in the season that as we were going north up the Alcan, everybody in the world was headed south.

Bill


Or just keep it turned way down.


We keep ours set to about 60 degrees overnight when we are heading south from Alberta to warmer climes in December and January. We have extra blankets on the bed, and even at home prefer it when it is cool in the bedroom at night. We both sleep better that way.  If the outside temperature is around -15 C, you sure don't want to turn it off overnight. That is just too cold for comfort. You also risk having the plumbing freeze up.


Remember, of course, that you're still going to have to heat the unit up the next day. That too is going to take some power.



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