Battery AMPS Per Motorhome System

[MattTaylor]

I used a meter with an amp loop clamped around the positive battery leads to find out how much power is being pulled from the batteries when I turn something on, whether it be a 9v something operating directly off the battery bank or a 120v something operating off of our 3000 watt inverter. Out of interest and in hopes that this information may help someone else in the future, I provide those numbers here. All numbers are in amps per hour and were read directly from the meter.

3 Speed Fantastic Fan
Low = 0.3
Med = 0.7
High = 1.2

1141 Type Light Bulbs
8 = 11 amps
7 = 9.7
6 = 8.3
5 = 6.8
4 = 5.1
3 = 3.7
2 = 2.2
1 = 0.7

Refrigerator = 23
LED Rope Light (Walmart) = 0.6
25 Inch Flat Screen TV, Direct TV H25 Converter, Power Inserter = 5.3
Mr. Coffee, 12 Cups, 900 Watts = 63
Front Air Conditioner = 83 amps!!
Front Air Conditioner Fan Only = 24
Floor Fan, Squirrel Cage Type (Walmart) -
Low = 6
Med = 7
High = 8
Portable 3 Speed Bonaire Swamp Cooler
Low = 10
Med = 12
High = 14
Microwave (and the winner is!!) = 163 AMPS!!

The reason I went thru this testing is because on our latest boondocking weekend trip to the lake we woke both mornings to find our battery bank at 48% SOC as stated on the Go Power charge controller, but I didn't bother to measure voltage at the battery bank, will next time. Because of this low SOC and the camp area's quite hours until 8am I had to wait for coffee, in my world that is simply unacceptable, ha! I think adding 2 more T-105 batteries will solve this issue for us. Comments from the more experienced solar experts out there are always welcomed of course.
If I'm not thinking correctly on this, please, someone point it out. Thanks!!

[twinboat]

If the 4, T105 batteries are in good shape and charged by late afternoon, then you need to use less power or add capacity.


You list your refrigerator at 23 amps. If it runs 1/3 the time, that is 7.6 AH X 14, late afternoon and night hours. That is 106 AH, almost 1 set of T105s to 50%, just for it.


That leaves you 1 set of T105s, for everything else. I think you are a little light, on your battery capacity.

Don't wait for morning coffee, hit the boost switch, for the 2 minutes it takes to brew it.

[JFNM]

Hi Matt,

Good info. I agree, a larger bank may be the answer. Couple questions/thoughts for you.

1. I run my refrigerator on LP when boondocking. I'm guessing you do not have this option? If an electric only refrigerator, perhaps consider a dedicated smaller inverter (300 watt??) to minimize the amount of 'wasted' power.

2. When boondocking, I use an old style percolator coffee maker on the stove (LP).

3. Turn that big inverter off at night. Most of them consume a good bit of power even when doing nothing. Mine (2000 watt) is kept off unless needed and that is limited to microwave and TV use - nothing whilst sleeping.

4. If you need some air moving at night, get a 12V fantastic fan so the inverter is not necessary. I don't live in a hot/humid area and admit that this may not be enough in that situation.

Hope that helps!

[twinboat]

I should have mentioned, that your inverter could be using a lot of power. I had a cheap, 2500 watt Sine wave, one that drew 4 amps at idle. That's 40 AH a night, doing nothing.


My Xantrex PS2000, only draws .4 amps idle. Dig into your inverter specs, to see what kind of draw it has with no load.


I assumed, from the draw, you are running a residential refrigerator. If not, the 120 volt heating element can be as high as 500 watts, on a RV fridge.

[MattTaylor]

Thanks for the reply guys! Just returned from town where I bought 2 more T-105s to add to the bank, that should solve the coffee problem but I do like the idea of an old style perk-pot.

The inverter is the Go Power model. It's a 3000 Watt with a 6000 surge rating PSW inverter. I checked it's draw at idle, the meter said 1.5 amps but the spec says that it's no load power draw is 2.0 amps. It also has a power save feature that drops the no load draw to 0.55 amps.

The fridge is the original electric/gas auto selecting type. My plan was to run it on solar during the day, then flip it to gas in the late afternoon and boost the battery bank before losing the sun. I think I'll adopt your method of just running on gas all the time while boondocked, it seems to sip propane. We've ran it on propane a bit, cooked on the stove, even ran the furnace since buying the rig 3 years ago, it came with a full propane tank and according to the LP idiot lights it's still full... not sure I understand exactly how that works.. magic maybe? In hindsight, I recall seeing the spec for the fridge, said it draws 314 watts / 12.8 volts = 24.5 amps. Perhaps the difference is that I had the door shut so the internal light was not on.

We have the Fantastic Fan in the kitchen area and it works really well, I listed it's amp draw, only 1.2 amps per hour on high. I'm considering buying another, especially if I can find a used one on the cheap, and use it to build my own swamp cooler because the Bonaire pulls 14 amps with the water pump on but get this... it pulls 13.5 amps when running only the fan! If I can adapt a Fantastic Fan the entire thing would draw only 1.7 amps per hour, that would be awesome!

Well, gonna go install those 2 new batteries. That gives me 675 amps of storage, 337'ish amp hours of use. Good thing, coffee pot is almost empty.

[twinboat]

Running the fridge on battery during the day, is cutting into about half your solar output, during you peek charging times. That could be why you don't get that morning coffee.

More batteries will help, but use the gas, unless plugged in or traveling.

[DAN L]

matt taylor,
all batteries in a house bank should be the same model and age.
there is a preferred way to hook up 4 6v batteries to equalize or balance current draw and charging.
Google ''the 12v side of life.''

[MattTaylor]

Dan,

All the batteries are new T-105s. I installed the first 4 T-105s about 2 weeks ago, used them this past weekend for the first time. Thanks for the link!

[jbrv]

I am no help on the batteries.

I also like my morning coffee (really all day) and do not like to wait for it.

Two options. French press. Heat up water on the stove.

With that I also have a coffee maker like the one in the link. I am not a coffee snob, I just want something black that taste like coffee...........so.......That insulated carafe will keep coffee or water (to use with the french press) hot for at almost 24 hours (longest i went was 18 and it was still steaming hot)

Lets you brew the coffee when you have plenty of power and drink it later when power is not overflowing.

http://www.jcpenney.com/cuisinart-thermal-coffee-maker/prod.jump?ppId=1909376&selectedSKUId=78060080018&s electedLotId=7806008&fromBag=true&quantity=1&cm_mm c=ShoppingFeed-_-GooglePLA-_-Coffee%20Makers-_-78060080018&utm_medium=cse&utm_source=google&utm_c ampaign=coffee%20makers&utm_content=78060080018&gc lid=CLroitzc5MYCFYIXHwodZiEO7A&kwid=productads-plaid^83170164578-sku^78060080018-adType^PLA-device^c-adid^45810124418

[JFNM]

Originally Posted by MattTaylor

The fridge is the original electric/gas auto selecting type. My plan was to run it on solar during the day, then flip it to gas in the late afternoon and boost the battery bank before losing the sun.

I've contemplated a similar thing. I seem to have an excess of power in the afternoons (after battery bank is fully charged) and thought that a small dedicated inverter for the refrigerator might be the way to go. Automating this setup (e.g. dedicated inverter comes on when battery bank full, turns off when solar power drops below some level) would be a really neat but I haven't invested any time in this to know if it is reasonably possible. Since my refrigerator is NOT wired to my big inverter, I just run on propane.

Originally Posted by MattTaylor

We have the Fantastic Fan in the kitchen area and it works really well, I listed it's amp draw, only 1.2 amps per hour on high.

Sorry, I was pretty vague. I have one of the box style 12 volt Fantastic fans. I move it around as needed. On hot nights, it sits on the dresser blowing air directly on me whilst I lay in bed. A ceiling fan would be ideal but I'm lazy and that sounds like a big project.

Originally Posted by MattTaylor

Well, gonna go install those 2 new batteries. That gives me 675 amps of storage, 337'ish amp hours of use. Good thing, coffee pot is almost empty.

That is a pretty great battery bank. I only have 440 ah and it seems to be plenty for my use but size DOES matter!!

My biggest electrical "problem" is this silly convection oven. I sure wish I had my old propane unit back. On a positive note, I grill more, use the dutch over more, and may eventually get around to using the stove top pressure cooker more.

[twinboat]

Originally Posted by JFNM

I've contemplated a similar thing. I seem to have an excess of power in the afternoons (after battery bank is fully charged) and thought that a small dedicated inverter for the refrigerator might be the way to go. Automating this setup (e.g. dedicated inverter comes on when battery bank full, turns off when solar power drops below some level) would be a really neat but I haven't invested any time in this to know if it is reasonably possible. Since my refrigerator is NOT wired to my big inverter, I just run on propane.

I did this on my MH. I use a yandina battery combiner and a 120 volt, 12 volt coil, relay to the AC of the fridge.

When charging volts reach 13.5, the combiner closes contacts and sens power to the relay, which in turn, supplies the fridge with 120 volts.

Issue - the fridge heat coil, uses over 300 watts, about 35 amps, DC.

You need that much and more, solar output, to cover it.

You could use the combiner to switch the 12 volt side of a small inverter. The combiner is good up to 100 amps DC.

I chose yandina, because it does not need to sense 12 volts, on both sides, like a ciyrx combiner.

[JFNM]

Thanks twinboat - excellent info!

Hope this isn't hijacking this thread...

Have you considered what it would take to add another "trigger" to the combiner circuit that can detect a 'full battery' state?

I have a Trimetric monitor and Morningstar remote panel monitor - it would be neat to have outputs on these units that would switch on when the battery state is X percent and the panels are producing more than Y watts. The goal would be to switch the relay to the refrigerator inverter when the batteries are "full" (or near full) and there is sufficient solar power for the electrical component.

I may be overthinking this - not exactly sure what is necessary but my goal is to first charge my batteries and only then put the excess capacity to work.

[MattTaylor]

No worries on hijacking the thread, this is the kinda stuff I look for! Great info.

Went to the Tulsa RV show on Saturday and had a close look at the Winnebago Forza 36G, great rig! Took a real close look at the battery/inverter/fridge setup, I don't like it. The residential fridge would have to go in favor of AC/LP auto switching like the Norcold we have now. The battery bank would have to be upgraded, as would the inverter and charge controller. Basically, when we get it (not if ), the prewiring will come in handy, maybe.

[mel s]

Originally Posted by MattTaylor

Thanks for the reply guys! Just returned from town where I bought 2 more T-105s to add to the bank, that should solve the coffee problem but I do like the idea of an old style perk-pot.

MattTaylor
When boondocking, and when overnighting with no shore power, we make coffee on the propane cook top which uses NO amps, (and the refrigerator on propane which uses only a few).
Mel
'96 Safar