Inverter

[BarbaraG]

I'm looking into having an inverter put in, but have a number of questions.

1. What kind of batteries are in the FR3? I find nothing in the documentation and can't see anything on the batteries. Would it be helpful (and possible) to replace them with more or better batteries?

2. I primarily want to be able to watch TV and run the furnace (can live w/o the microwave)... oh, and the computer. For how long would I be able to do so for different sizes of inverters?

3. What happens to the appliances I'm running if I drain the batteries using the inverter? Would they potentially get damaged as the power goes down?

I do understand the whole watts = volts* amps, but I don't know how much charge gets stored in the batteries or what the discharge curve looks like.

Any help would be appreciated.

Thanks.

Barbara

[BarbaraG]

Okay, I looked at the curve posted above... I guess what I don't know is what amp-hours the batteries are rated at.

Oh, another thing: how long would I have to run the generator to recharge the batteries?

Thanks.

Barbara

[Herk7769]

Originally Posted by BarbaraG

Okay, I looked at the curve posted above... I guess what I don't know is what amp-hours the batteries are rated at.

Oh, another thing: how long would I have to run the generator to recharge the batteries?

Thanks.

Barbara

Barbra,

Amp Hours vary by manufacturer and may even have to be calculated from the Reserve Minutes (RC) that some use (multiply RC by 0.4167 to get AH).

Since you should NEVER discharge any deep discharge battery below 50% capacity, recharge can take anywhere from 4 to 36 hours depending on whether you use a dedicated charger or the converter in your camper.

http://www.forestriverforums.com/for...now-54002.html

Herk

[cucamelsmd15]

Originally Posted by herk7769

Barbra,

Amp Hours vary by manufacturer and may even have to be calculated from the Reserve Minutes (RC) that some use (multiply RC by 0.4167 to get AH).

Since you should NEVER discharge any deep discharge battery below 50% capacity, recharge can take anywhere from 4 to 36 hours depending on whether you use a dedicated charger or the converter in your camper.

http://www.forestriverforums.com/forums/f218/my-battery-water-level-and-charger-its-surprising-what-i-dobnt-know-54002.html

Herk

I wouldnt say NEVER discharge below 50%, but you significantly reduce the battery life if you do.

Barbara, the inverter size doesnt matter, the battery size is what matters. The FR3 comes with two group 27s that are about 200 amp hours total. With our charger, if you discharge to about 50%, youll need to run the generator for about 2-2.5 hours conservatively to get back to full charge.

When we dry camped a few weeks ago, it was particularly cold (which hurts battery performance anyway), but running the furnace, watching a little TV with the Blu Ray player, charging the cell phones overnight, and running a bedroom clock, we were at 50% battery in the morning.



We were at 12v even. Remember, it was in the 20s that night, which meant we ran the furnace A LOT.

As far as what happens when the batteries die, well, lots of weird stuff can happen that you probably dont want to think about.

If having an inverter is something youre really serious about, youll either want to switch to two 6v golf cart batteries, or better yet, upgrade for 4 6v batteries (I plan on doing the latter). The 12v provided with the coach will work in a pinch, but you wont dry camp for more than 2 days at a time on them if I had to guess.

[Herk7769]

Two things:

1) Even 3 hours of charging will not replace a substantial amount of the lost capacity due to the staging in the converter or battery charger. It certainly will not bring it back to 100% as FLOAT charging starts at about 90% (and no load) and the charge rate is measures in milli-amps. Voltage will recover to above 12 volts quickly (surface charge), but the battery will still need to replace the lost electrons (capacity to deliver) at a safe rate to prevent boiling the battery and can take more than 36 hours on shore power or generator to reach 100%.

2) The Battery lights are not a reliable way to determine capacity as what most people use as "FULL" is actually "C" for "charging." The "F" is used only when checking your holding tanks and propane is equipped. The lights will still be "Good" (3 lights) until the battery capacity drops below 50%.

[BarbaraG]

Okay, here is what I'm getting:

1. I probably should get 4 deep-cycle golf cart batteries if I'm going to get an inverter.
2. I don't want to let the batteries get below 50% of their charge. How do I know if the battery monitor lights are not reliable?
3. Inverter size doesn't determine how long I can run TV, etc., on my batteries, the batteries do. What then does inverter size determine?

Does anyone know a good reference for this stuff so I don't have to be asking for a tutorial on the forum?

Thanks much, all.

Barbara

[Broadway Joe]

Re:3 the inverter size determines the total amount of items it can power. If you have a 200 watt inverter you can only power an item that draws approx 1.75 amps.

[rockfordroo]

You must convert AC amps to Watts by multiplying by 120 volts; THEN convert those Watts BACK into DC amps by dividing by 12 volts.

OR, you could just multiply AC amps by 10 to get DC amps. (120/12 = 10)

[Herk7769]

If you are going to be operating on battery/inverter for any significant amount of your camping time, a good battery monitor system is a must.

I use the less expensive Trimetric TM-2025RV monitor system.

http://www.solar-electric.com/tr20mosy.html

You input the total capacity of the battery bank at 100% charge and it monitors the actual amperage in (charging) and out (discharging) and it will display remaining battery life as a percentage remaining.

You can also monitor the voltage on the batteries; a solar panel's output; and instantaneous amperage in/out of the battery bank using a shunt.

ADDED FYI: The 13.6 amps of charging is the maximum charging current I can get on a 50% discharged battery bank (2 - Deka DP-24 75AH batteries) with the OEM WFCO converter).

[Batts-toy]

Originally Posted by rockfordroo

OR, you could just multiply AC amps by 10 to get DC amps. (120/12 = 10)

You meant divide as in the example correct?

[Herk7769]

Run the furnace and drive an inverter is gonna be hard on a single battery. Even with two (depending on other draws - like incandescent lights), you may find you won't get through the night depending on the state of charge prior to quiet hours at the campground).

Knowing the actual % of capacity remaining is critical when there are quiet hours posted at the campground and you need the heater at night.

[cucamelsmd15]

Originally Posted by herk7769

If you are going to be operating on battery/inverter for any significant amount of your camping time, a good battery monitor system is a must.

Yes, and now would probably be the right time to mention that I also bought a Trimetric, just like Herk.

The FR panel, while merely ok for monitoring tank usage, is not an accurate portrayal of battery charge.

Also since herk mentioned incandescent lights, if you havent thought about swapping all your lights for LEDs, now would be the time.

[Herk7769]

Originally Posted by cucamelsmd15

Yes, and now would probably be the right time to mention that I also bought a Trimetric, just like Herk.

The FR panel, while merely ok for monitoring tank usage, is not an accurate portrayal of battery charge.

Also since herk mentioned incandescent lights, if you havent thought about swapping all your lights for LEDs, now would be the time.

And not very good at "Tank Usage" either!

http://www.forestriverforums.com/for...lbs-12034.html

[cucamelsmd15]

Nope. I see we have similar tastes in LED panels as well.

[rockfordroo]

Quote:
Originally Posted by rockfordroo
OR, you could just multiply AC amps by 10 to get DC amps. (120/12 = 10)

You meant divide as in the example correct?
__________________

No multiply: 1 amp at 120 VAC is 10 amps at 12VDC, thus multiply AC amps by 10 to get DC amps.

[Herk7769]

Originally Posted by rockfordroo

No multiply: 1 amp at 120 VAC is 10 amps at 12VDC, thus multiply AC amps by 10 to get DC amps.

A factor of 10 to 1 : DC amps to AC amps.

However, the ratio does not work when the DC voltage provided by the battery fluctuates from fully charged 12.7 volts to depleted 10.5 volts).

Appliances to be powered by your inverter are "amperage rated" (watts) at a defining voltage AC. For example 1000 watts at 120 volts. The inverter will manage battery draw to deliver (as best its controller can) 120 volts AC.

In this case the amperage would be 8.33 amps. Using the above ratio, you would draw 83.3 amps from a 12 volt battery (1000 watt demand).

However, a battery delivering 12 volts is actually 50% depleted. If the battery is fully charged, the amperage drawn by the inverter would be 1000 watts / 12.7 volts or 78.7 amps.

As the battery passes 50%, say down to 11 volts, The amperage draw will increase to 90.9 amps (1000 watts / 11 volts) which will accelerate battery depletion to inverter cut out voltage.

[rockfordroo]

83.3 amps vs 78.7 amps is only about a 5% difference.

I guess we could start talking about the accuracy of everyone's ammeter and see what changes that makes. Also, is it really 110 VAC or maybe it's 120 VAC. Or maybe less when it's 100 degrees out and everybody in the campground is running their AC units.

The 10 to 1 ratio is a "rule of thumb."

[PhotoMaster]

Originally Posted by rockfordroo

Also, is it really 110 VAC or maybe it's 120 VAC. Or maybe less when it's 100 degrees out and everybody in the campground is running their AC units.

Then we'll all need to carry some capacitors to shift the phase angle back from all those inductive loads!

Sorry! A blast from the past.

[Herk7769]

Originally Posted by PhotoMaster

Then we'll all need to carry some capacitors to shift the phase angle back from all those inductive loads!

Sorry! A blast from the past.

I am sorry; I thought we were talking about inverter loads.

[BarbaraG]

Okay, somewhere on this forum somebody posted a list of typical current draws for various appliances, etc. Should have saved it when I saw it. Now I can't find it. Has anyone else seen this and, if so, where?

Thanks.

Barbara