Inverter Power went ZIP.....

fansill · 09-26-2011, 04:48 PM

Good Evening All,

Just back from another great weekend in the Big Baby. We were boondocking at the Nascar Races in Loudon and I was anxious to fully access and understand how much power I could get from my house batteries via the 2000 watt inverter.

First couple of days when we turned in for the evening...(evenings have to be without generator noise) the inverter read approx 12.5. We watched TV, we had lights on and off and the fridge was running on Propane all night. In the monring when I got up, the Inverter would read anywhere from 10.4 to 11.4. Then I tried to start up my Keurig coffee maker and everything would go off...No TV, no 110 lights...nada. I gathered that my coffee maker was too much draw on the batteries, so I started up the gennie for running the Keurig.

Last night out we started our quiet time with the inverter saying 12.3 and hubby left the TV on almost all night (with the accompanying satellite receiver). I woke at 4am and shut it off but then when the pups woke me at 6:30...there was no power at all from the inverter. Everything was flat. I tried to start the Gennie and it would not start. When I started the ignition, the gennie started up fine.

I have 4 house batteries that are original to my 2005 Revolution coach. They are 12 volt.

My questions are....

1. DO you think it is normal to only get about 12 hours of TV and receiver use out of 4 batteries?

2. Does the Generator start using the house batteries? And is this why I could start the gennie once I started the engine?

3. Could I have just one bad battery and would this cause them all to get sluggish or discharge quickly?

4. If I figure out it is just one or two batteries that should be replaced is it advisable to just replace the bad ones or should I replace them all?

5. Right now I have the original 4 - 12 volt batteries. How can I figure out what kind they are and do any of you have suggestions for my options for replacing them? Brands?...Types?...etc...

Thanks in advance for your assistance. I am still loving my new toy and really enjoying being the main driver of the Big Beast...

Faith

JimM68 · 09-26-2011, 07:20 PM

There are meters / gauges you can buy that will track and display the ampere hours you have drawn from your battery bank. The manufacturer of my inverter, Magnum, offers one as an option, replacing or adding onto the original panel.
That will let you see in black and white how much power you are taking from your batteries, and if they are delivering what they should.

It does seem to me that you are getting about what you should out of your batteries.
We did the chicagoland speedway races last weekend, I would start the generator at 12.0 volts, and let it run until it showed "absorb charging" this worked out to a 2 hour charge in the morning and another shorter one in the evening.

Anything with a heater (coffee maker, hair dryer) will suck some serious power. 12 amps into the coffeemaker = 120 amps out of the battery.

How did you like the races?

DrewCrewOf2 · 09-28-2011, 04:32 PM

In My "Not So Humble Opinion" (kidding) and being in electronics for over 50 years... 2011-2005 = 6 years is a potential problem! You did say they were the original batteries, right? Batteries age and being used/unused can stress them a lot. Sitting unused they will sulpher up in the bottom and any battery only has so many charge/discharge cycles in them even if you treat them just right. 6 years may be pushing it.

Are you familiar with using a hydrometer? They never lie. here is a link to a tutorial:
Battery Tutorial

Math wise (hope I don't get this wrong) say each battery is new and is a 100 amp-hour battery. 4 times 100 = 400 amp hours if you run them pretty much dead. Roughly speaking 12 volts times 10 = 120 volts so you need to multiply the amperage of your appliance by 10 to see how long you could run it. Most deep cycle batteries are more than 100 amp/hours but this is for example.

Microwave probably uses 10 or more amps so 10 times 10 = 100 amp draw at 12 volts. Theoretically 4 hours of Microwave usage would kill the battery.

TV and Sat box I would guess maybe 200 watts 2 amps at 120 = 20 amps at 12 volts divided into 400 amp hours = 20 hours... if nothing else is on. Problem is, how well are the batteries being recharged each day? Running the generator for an hour won't do it. It will pick them up some but the batteries need a rather long "topping off" to get them all the way up. Reading the voltage with no load on the batteries is not an accurate way to determine charge level.

Oh, well I said enough... try to determine how good the quality your 6 year old batteries are by purchasing a hydrometer and testing them. I will bet they are sagging and need to be replaced... but... just guessing here. -Dennis

GaryKD · 09-28-2011, 05:46 PM

Hi fansill,
Charging to 12.3 VDC means you are at about 60% charged. Fully charged is 12.6 VDC or higher.

If the batteries are wet cell (one must add water from time to time) use a hydrometer to determine the battery condition. One must first ensure the cells are covered with distilled water and fully charged.

If the batteries are sealed first determine if they will accept a full charge. Let them charge for 3 or more days and take a reading across the batteries (with the charger off). 12.6 VDC is needed to be fully charged. If they will accept a full charge, take the batteries to a Battery+ store or any auto parts store. Have them do a load test on the batteries.

The batteries may be at the end of their life. If this is the case (will not take a full charge fail the hydrometer test or load test). Replace all the batteries is the only solution. Get the physically largest deep cycle batteries that will fit in the space available. When it comes to batteries size matters.

Not to confuse this, but you may get more cycle life from 4, 6 volt batteries (connected in series) than 4, 12 volt batteries (connected in parallel). Check the battery specs before you purchase.

DrewCrewOf2 · 09-29-2011, 06:40 AM

Here is a load tester where you can get a more serious idea of where your batteries are.

Battery Load Tester - 100 Amp, 6v/12v

These take a little getting used to, to get it right. There is a wire resistor load inside that gets very (like RED) hot when you flip the switch. You can only hold it on for less than 10 seconds. If you have a good, similar sized, fully charged battery, then go put it on that for 5-10 seconds. See how well the needle holds up. Let it cool off for 3-5 mins and try it again. Then unhook your batteries (need to test them one at a time) and while the reaction of the good battery is still fresh in your mind, start testing yours. If the needle sags out of the green during the test... out with the old and in with the new!

Still I think the Hydrometer is cheap and will generally tell you the truth. As Gary said, get a trickle charger (You newer rig probably already has one) and let them fully charge overnight before doing either the load or Hydrometer tests.

My fav Hydrometer:

https://napaonline.com/Catalog/Catal...145_0282520247

wa8yxm · 09-29-2011, 11:02 AM

To take them by the numbers:

1. DO you think it is normal to only get about 12 hours of TV and receiver use out of 4 batteries?

A: well.. I'd expect a bit longer from a "4=pack" but without load and capacity testing of the batteries... it's possible.. also 12.3 indicates they were not full when you started.

2. Does the Generator start using the house batteries? And is this why I could start the gennie once I started the engine?

A: In your case YES! and YES!.. not all rigs work that way but your question says yours does.. NOTE: on mine the Emergency Start switch would do it too... Not many work that way though.

3. Could I have just one bad battery and would this cause them all to get sluggish or discharge quickly?

YES! However with six volt batteries you always replace a pair, never just one.. WHY? because there are no six volt batteries in RV's. just 12 volt that come in 2 pieces for ease of handling.. That is to say the two six volt batteries in the pair are hooked like this
{bat}t{ery} so they work as one,, When you replace one half, replace the other as well.

If your 4 house batteries are ALL 12 VOLT: DISREGARD my six volt comments. It is still possible for just one bad one to take out the entire bank however.

4. If I figure out it is just one or two batteries that should be replaced is it advisable to just replace the bad ones or should I replace them all?

A: The experts all advise "Replace them all" I agree with them that this is best but save for the six volt comments above.. I don't push it. You can replace just one.. however consider if you do ... the rest may fail soon (likely will)

5. Right now I have the original 4 - 12 volt batteries. How can I figure out what kind they are and do any of you have suggestions for my options for replacing them? Brands?...Types?...etc...

A:Look at the label and google what you find Go to the manufacturer's web page

odds are they are "Marine/Deep cycle" type which is a type of starting battery, However it is possible you have true Deep Cycle batteries.

My preference is True Deep Cycle.. I've read posts from a lot of folks who say "No difference" but in my personal expierence.. BIG DIFFERNECE. Deep cycles can take the occaional "opps" way better than starting types including Marine/Deep cycle, What's an opps? Batteries so low the generator won't start comes to mind. Not good for any battery but Deep Cycles are more likely to recover.

If you have the room (They are taller) Consider going to six volt GC-2's in pairs. Each pair is around 220 amp hours..

Some facts:
Group 24 each around 70=75 AH (pair 150 ah)_
Group 27... Around 90 each (180 paired)
Group 29 Around 100 each (200 in pairs)
Group 31 around 120=130 each (figure 250 paired)

GC-2 pairs in series, 220=225 AH

NOTE: all figures are approximate and will vary from brand to brand (usually by less than 10 percent)

OPTIMA (bad choice) 60 percent of the above capacity and cost more too.

Trojan: Good brand of flooded wet cell
Lifeline: Best in the AGM (agm's are more expensive, not convinced of any benefits)

Sam's Club six volt: Best bang for the buck.