House batteries

[Miramar Owner]

As I mentioned in an earlier post, I turn off the inverter about 10:00 at night (before I shut down the generator). In the morning I register 12 to 12.1 and the temperature has never risen above 40 degrees. That is when dry camping with daytime highs hitting 90.

We are in an area that requires gens to be shut off at 10 so I cool it down in the motorhome before 10 and it stays tolerable throughout the night.

I turn on the inverter to check before starting the generator. Never had a problem.

[mustang94]

ok hope I get this right.... I went ahead and tested volts and amp draw today on just about everything and here are my results. Batteries fully charged and just disconnected from shore power. The pic with 13.12 volts and 4.53 amps was my starting point.
battery and inverter turned off. 13.10 volts 1.80 amps 2nd pic
battery on and everything else off. 13.08 volts 4.09 amps
8 main LED lights on. 13.00 volts 8.82 amps
inverter only on 13.00 volts 7.25 amps
refrigerator only 12.86 volts 21.81 amps 3rd pic
main slide moving in 12.86 volts 21.80 amps
bed room slid moving in 12.91 volts 13.92 amps
slid with entertainment center 12.91 volts 15.70 amps
water pump only water running 12.92 volts 14.77 amps
tv, sat, dvd and switch box on 12.81 volts 23.36 amps
everything back off again 12.92 volts 7.09 amps
outside refrigerator only 12.80 volts 16.73 amps
main propane heater 12.75 volts 25.04 amps 4th pic
hot water heater electric only 12.91 volts 7.55 amps
water heater gas with electric 12.90 volts 8.65 amps
water heater only gas 12.90 volts 8.53 amps
entertainment, main lights, heater and fridge 12.44 volts 63.09 amps last pic

When everything was off the only lights I could see still on and unable to turn off through out the test was, my main to gauge lights, fridg off light, the 02 light, radio back light, bed room and out door tv light. Took a little more than a hour to do the test. You can also see in each picture the watts used at that time as well. Now time for me to do some math and see what I need. Hope all pictures come out in order.

[mustang94]

Originally Posted by Chance

Excellent point. If you look at typical residential refrigerator energy consumption, most newer ones use around 2 kWh or less of energy per day on average. Divided by 24 hours that's less than 100 watts on average, and we should expect that nighttime power consumption to be lower than daily average.

If using 28 Amps (over 300 watts) to primarily run the fridge (a few LEDs are insignificant), it means one of a few things:

1) Refrigerator is an energy hog (not efficient)
2) Refrigerator isn't running most of the time at night
3) Inverter isn't very efficient at that low power rate
4) A combination of above

My sister's 5er has a large residential fridge with 4 golf cart-size batteries (don't recall brand) and it runs overnight without generator. And to me that makes sense because these Trojan batteries store 1.6 kWh of energy each (that may be at 100-hour rate so actual is a little lower). Four batteries is therefore 6.4 kWh. At 50% that's still 3.2 kWh usable energy, which is more than most modern refrigerators should use in an entire day.

Personally, I would want to break down the 28 Amps in more detail because it seems high to me also if it is suppose to be mostly the fridge.

Oh here is the sticker from inside the fridge. Whirlpool full load 7.2 amps.
But this is when on straight 110 volts AC and not 12 volts DC.

[mustang94]

Originally Posted by Oneilkeys

That's really interesting and significant. I read thru the User Guide and they say nothing about not routinely discharging below 40 or 50%. Everything I have read (see below for an example) says that a deep cycle battery will last up to twice as long if you do not routinely discharge it below 50%. If Trojan stands behind its ability to routinely discharge its battery down to 20%, that gives you 30% more amp hours that you can use before you have to turn on your generator. I think I would get Trojan to confirm that before I did it, but it would be a good reason to buy Trojan batteries.

But would 20% battery @ 11.58 volts be enough to start the generator?

[Oneilkeys]

Originally Posted by mustang94@hot.rr.com

But would 20% battery @ 11.58 volts be enough to start the generator?

My Axis does not have auto start and I can always start my engine to fire up the generator or charge the batteries. Since I do not tow, I generally do not spend more than 2-3 days in the same place without moving the RV. So running the battery down to 11.6v and then driving the RV makes sense for me.

[gmc]

Originally Posted by mustang94@hot.rr.com

But would 20% battery @ 11.58 volts be enough to start the generator?

In a pinch - the 'Emergency Start' switch is a 2 way street...
It ties the coach batteries to the chassis battery - typically used to start the engine - but also allows the chassis battery to help start the genny.
Not something I'd want to have to use all the time - but... nice to have it as an option.

[Chance]

Originally Posted by mustang94@hot.rr.com

Oh here is the sticker from inside the fridge. Whirlpool full load 7.2 amps.
But this is when on straight 110 volts AC and not 12 volts DC.

I looked up your model number and found, as expected, that the "average" power usage based on energy rating is much lower than the 7.2 Amp peak.

On "average" the fridge should use just under 2 kW-hours per day, so averaged over 24 hours in a day, that's under 100 watts. So average current over long periods of time should be in range of 1 Amp or so at 115-Volts.

The "full load" current probably only kicks in for short periods; like maybe the occasional defrost cycle and the like.

[Oneilkeys]

Originally Posted by gmc

In a pinch - the 'Emergency Start' switch is a 2 way street...
It ties the coach batteries to the chassis battery - typically used to start the engine - but also allows the chassis battery to help start the genny.
Not something I'd want to have to use all the time - but... nice to have it as an option.

That is true. However, my genney does not start as easily as my engine. If you run down your coach battery trying to start the genny, it's AAA time. At least with the engine I know it is going to start and then charge both batteries. With my genny, I am never quite sure. Good point on the two way aspect of the emergency start. In a pinch it could be useful.

[JamieGeek]

I've used the emergency start to start the genny. I had to do this for one simple reason (I'll give you a clue in a single word: "Harris").

Originally Posted by Oneilkeys

my genney does not start as easily as my engine.

I've wondered: Which is better: Start the genny and let it charge stuff up, or start the V-10 and let it charge stuff up. Sure the genny does take a little more cranking than the V-10 but its starter is smaller and thus shouldn't require the current the V-10 does.

Ultimately I think the decision comes down to: Which battery is "more dead"--start the other engine (e.g. if house battery has less charge than coach then start the V-10).

[Chance]

Originally Posted by JamieGeek

I've used the emergency start to start the genny. I had to do this for one simple reason (I'll give you a clue in a single word: "Harris").


I've wondered: Which is better: Start the genny and let it charge stuff up, or start the V-10 and let it charge stuff up. Sure the genny does take a little more cranking than the V-10 but its starter is smaller and thus shouldn't require the current the V-10 does.

Ultimately I think the decision comes down to: Which battery is "more dead"--start the other engine (e.g. if house battery has less charge than coach then start the V-10).

Personally, under those circumstances I would always start the V10 first.

There are many reasons I would start the engine first. One major concern is that if house batteries are too dead to start a little Onan, then connecting chassis battery to house in order to start Onan may suck too much juice from chassis battery to house batteries. Unless you disconnected the house batteries while attempting to start the Onan, the risks of getting stranded are much greater in my opinion.

I also agree with above comment; V10s normally start much faster than generators.

[JamieGeek]

Originally Posted by Chance

One major concern is that if house batteries are too dead to start a little Onan, then connecting chassis battery to house in order to start Onan may suck too much juice from chassis battery to house batteries.

That is what I was saying: if the house battery is discharged start the V-10, if the chassis battery is discharged start the genny.

It would stand to reason that the V-10 starts quicker (fuel injection) vs the genny (carburetor).

[Oneilkeys]

It would be interesting to check out how many amps the V10 takes to start vs the genny. I don't have a meter in my chassis battery and it starts first time, every time, so it is difficult to see how much battery drain it takes to start it. For my genny, I hadn't started it in several weeks and I ran the house batteries down from 12.3 to just under 12v before it started. And that is with two 29 non-Harris batteries.

[Chance]

Originally Posted by JamieGeek

That is what I was saying: if the house battery is discharged start the V-10, if the chassis battery is discharged start the genny.

It would stand to reason that the V-10 starts quicker (fuel injection) vs the genny (carburetor).

Sorry Jamie, I must have not followed your point entirely.


The other option of course is to eliminate the generator altogether and let the engine do its job when necessary. Granted there are regulations/ordinances that may limit running the engine as a generator, regardless of how misguided and or inappropriate they may be. I'm liking that approach but it's expensive and may limit where and when you can use it.


By the way, I haven't owned one, but it seems some newer generators are fuel injected. Maybe they start quicker -- don't know.

[JamieGeek]

Originally Posted by Chance

The other option of course is to eliminate the generator altogether and let the engine do its job when necessary. Granted there are regulations/ordinances that may limit running the engine as a generator, regardless of how misguided and or inappropriate they may be. I'm liking that approach but it's expensive and may limit where and when you can use it.


By the way, I haven't owned one, but it seems some newer generators are fuel injected. Maybe they start quicker -- don't know.

When I had my F-Series pickups I looked into obtaining a PTO generator (since the trucks did have PTO). I doubt PTO is available on the E-Series stripped chassis--wouldn't that be interesting: just eliminate the Onan all together and put a generator off the V-10.

Of course we could always put this bad boy in the Axis too:
Generator Head - 10,000 Watts Max, Belt Driven
7.2kW!! Run two A/Cs and the RV sitting next to us LOL

I believe all the quiet Honda generators are fuel injected but our common Onan's are not and still have a carb.

[Chance]

Originally Posted by JamieGeek

When I had my F-Series pickups I looked into obtaining a PTO generator (since the trucks did have PTO). I doubt PTO is available on the E-Series stripped chassis--wouldn't that be interesting: just eliminate the Onan all together and put a generator off the V-10.

Of course we could always put this bad boy in the Axis too:
Generator Head - 10,000 Watts Max, Belt Driven
7.2kW!! Run two A/Cs and the RV sitting next to us LOL

I believe all the quiet Honda generators are fuel injected but our common Onan's are not and still have a carb.

Jamie, I think you will likely see an engine-driven alternator approach succeed in marketplace first because it can run at various engine RPMs. With a standard generator (unless it was inverter type), you'd be limited to one speed in order to get 60 Hz current. That's the beauty of the system that Roadtrek and now Hymer are offering (at least in principle -- Devils often in details).

A second alternator when supplied from chassis manufacturer is cheap -- like around $500 if I recall right. That's for a small +/- 250 Amp X 12-Volt alternator (over 3,000 watts) that could charge house batteries fairly fast.

But with a dedicated system/alternator for the house, it would make little sense to stay with 12 Volts. It requires too much current. That's where a stand-alone dedicated system needs to work at 48 Volts. And at that voltage even a 100-Amp alternator would produce more power than the typical 4,000-Watt Onan. You can buy a 200-Amp X 48-Volt alternator today that puts out around 10,000 watts. That's overkill though except to charge large lithium battery banks in minutes.

The Roadtrek system appears to me to be the way the industry will take power generation, except that it will adopt 48-Volt as the new standard. Below is a picture of components Roadtrek integrate to work as one. Lithium battery bank, solar, inverter, alternator, and controls. I like the principle a lot, just don't know about how well the design has been executed.




P.S. -- Onan QG 5500 and QG 7,000 come in EFI fuel injected models.


.

[wredman]

I assume the house can not drain the chassis battery?

I also assume the engine can charge the house batteries

If I drain the house batteries, I would start the engine with the chassis battery, let run a few minutes, and then start the generator with the charging house batteries and alternator power being supplied. Then shut off the engine an let the gen continue charging. Is this how it works?

[Oneilkeys]

[QUOTE=wredman;52481]I assume the house can not drain the chassis battery?

I also assume the engine can charge the house batteries

If I drain the house batteries, I would start the engine with the chassis battery, let run a few minutes, and then start the generator with the charging house batteries and alternator power being supplied. Then shut off the engine an let the gen continue charging. Is this how it works?[/QUOTE

In the Axis the BIRD and Trombetta separate the house and chassis batteries so that running down the house batteries does not also discharge the chassis battery and leave you without the ability to start your engine. When the engine is started or the generator is turned on or the coach is plugged into shore power, the BIRD opens the Trombetta to charge both the house and chassis batteries at the same time.

So yes, if you drain your house batteries below what will start the generator, you can start the engine and wait a few minutes to put a charge on the house batteries and then start the generator.

[blw2]

Originally Posted by Oneilkeys

That's really interesting and significant. I read thru the User Guide and they say nothing about not routinely discharging below 40 or 50%. Everything I have read (see below for an example) says that a deep cycle battery will last up to twice as long if you do not routinely discharge it below 50%. If Trojan stands behind its ability to routinely discharge its battery down to 20%, that gives you 30% more amp hours that you can use before you have to turn on your generator. I think I would get Trojan to confirm that before I did it, but it would be a good reason to buy Trojan batteries.

My guess is that the 50% magic number has safety factors upon safety factors built in, as it has made it's way through to be "common knowledge". It's a nice easy round number. Also, it seems to perhaps apply more to the hybrid type and not the true deep cycle batteries.

[Chance]

Manufacturers often have charts similar to this one that may help buyers determine what is best depth of discharge based on specific requirements.

[Techn0]

Originally Posted by Chance

Manufacturers often have charts similar to this one that may help buyers determine what is best depth of discharge based on specific requirements.

So according to Trojan's User Guide and that diagram, I can discharge my new T-125s down to 20%. That would give me 392 amp hours of battery. Okay, works for me. I will see if it lasts for that many cycles. Hopefully lithium is mainstream before I have to replace them again.