Battery Drain

[OrangeCrush]

Originally Posted by vanderwielen

Nope, the fridge/freezer will draw 75w when the compressor is on with a duty cycle of 33% when the ambient is 70. I suspect you don't have an AI and are simply parroting others via previous posts.

No I don't have an AI. Yes I was parroting others who have measured actual average daily usage of a compressor fridge at 50-60 amps per day. I should have stated it more completely and called it 50-60 amp-hours of battery capacity per day. Lets use your numbers and go through the math. 75W/12V = 6.25 amp-hours which comes out to 24*6.25 = 150 amp-hours per day. Assuming a 33% duty cycle you have an average daily usage of 150/3 = 50 amps-hours per day. Over 3 days time that would be 3/4 of a 200 amp-hour battery bank.

[uncle_bob]

Originally Posted by richard5933

Since this happens after your third night of camping without shore power, I'm going to agree with the others that said there is a problem with the settings on your generator's auto-on feature. My guess is that you're not fully charging the batteries - just barely getting enough in them to make it through the first & second night. By the third night you hit the breaking point and use the reserve capacity.

It's also worth checking to find out if your solar is actually charging the batteries at all during these events. You should be able to monitor the amount of charge going into your batteries during the day when the generator is not running. I'm guessing that either the charge parameters are set wrong or the solar system is not charging for some other reason. If it were, then you'd have enough charge to make it through the night easily with only a 45-watt load.

Or, your actual load is much higher than 45w. Perhaps not everything on the house side of the system is actually going through your shunt? How many ground wires do you have on your house battery negative connection?

Hi

On the X, the 712 is a stock item. They wire it correctly. The grounds all go through the shunt.

The shunt may or may not be programmed correctly ( = it could be at the default settings ).

CPAP demand varies all over the place, just like the fridge. If the CPAP is running through the inverter (sounds like it is) that makes things even crazier for estimating numbers. As noted above, getting a DC/DC converter to deliver (most likely) 24V to run the CPAP is a really good idea.

The big load is still the fridge. Mainly because it runs 24 hours a day.

The solar is 200W as far as the house bank is concerned. If you *ever* see half that, you are doing great with all the junk that shades is.

Bob

[uncle_bob]

Originally Posted by OrangeCrush

No I don't have an AI. Yes I was parroting others who have measured actual average daily usage of a compressor fridge at 50-60 amps per day. I should have stated it more completely and called it 50-60 amp-hours of battery capacity per day. Lets use your numbers and go through the math. 75W/12V = 6.25 amp-hours which comes out to 24*6.25 = 150 amp-hours per day. Assuming a 33% duty cycle you have an average daily usage of 150/3 = 50 amps-hours per day. Over 3 days time that would be 3/4 of a 200 amp-hour battery bank.

Hi

Again, the OP is running an X. The fridge in that specific AS pulls just over 10A at the "100%" point. Shove 120W into your math and things just get worse.

Bob

[Rocinante]

If that fridge runs on both AC and DC power, it might be wise to unplug the fridge from the AC outlet so it always runs on DC. That’s more efficient than inverting from DC to AC and then converting that back again to DC at the fridge. The Norcold fridge in our 2016 works this way, and we yanked the AC plug for that very reason. Now it runs only on DC power.

[OrangeCrush]

Originally Posted by uncle_bob

Hi

Again, the OP is running an X. The fridge in that specific AS pulls just over 10A at the "100%" point. Shove 120W into your math and things just get worse.

Bob

Thanks Bob, yes that is significantly worse. I was just trying to illustrate that 75W at 33% is the same as 50 Ah per day. I think your numbers sum up the real daily draw pretty good though I think in all fairness we should be using a little higher voltage for lithium.

[Johncapp]

I can confirm that 50 to 70 amp hours per day is about right for a 12 volt fridge raider. Ours is 10 ft.³ ,works beautifully , but we did have to go to 300 amp hour of lithium batteries. We can boondock for many days with that reserve.

[uncle_bob]

Originally Posted by Rocinante

If that fridge runs on both AC and DC power, it might be wise to unplug the fridge from the AC outlet so it always runs on DC. That’s more efficient than inverting from DC to AC and then converting that back again to DC at the fridge. The Norcold fridge in our 2016 works this way, and we yanked the AC plug for that very reason. Now it runs only on DC power.

Hi

The compressor fridges they use in the X aren't to bad this way. Their effecendy on AC is very close to what it is on DC.

The *big* gotcha is the inverter. It is never a good idea to run the inverter to power something off batteries if that same item could go direct to the battery. Add another ~ 20% to the numbers if you go battery to inverter back to dc in the device.

Bob

Bob

[uncle_bob]

Originally Posted by OrangeCrush

......though I think in all fairness we should be using a little higher voltage for lithium.

Hi

..... which makes the example post even longer and gets into even more confusion using WH and KWH vs AH. Tracking battery voltage change as the battery dies ...yikes ... lots of tables and the like.

Bob

[Wazbro]

Originally Posted by OrangeCrush

Thanks Bob, yes that is significantly worse. I was just trying to illustrate that 75W at 33% is the same as 50 Ah per day. I think your numbers sum up the real daily draw pretty good though I think in all fairness we should be using a little higher voltage for lithium.

I believe using 12 volts, while less accurate, is better since it would give you a small margin for reserve to help compensate for other battery drains you might not have thought of. Remember the goal is to not run the batteries dead, not to be completely accurate as to why they went dead.

[JoanneAZ]

Originally Posted by Xman

I checked the information on the battleborns that came with our 24X and it indicates that at 0A, a single battery is charged at 13.6V resting and 14.4v charging. I looked at the settings on the auto start for the generator and it comes on at 12.4V and turns off at 13.2. This is how it came from Airstream and we have not used the auto start so it may be that yours is set the same way. On the Battleborn flier this indicates that the charge at 12.4V would be between 9% and 14% and at 13.2V it would be at 70%.

It may be worth contacting your dealer to see what Airstream or Battleborn recommends for the autostart settings. We just run the generator manually and look at the SmartShunt readings as discussed below.

You should be able to see the state of the battery using the Victron Smart Shunt that came in the 24X. Download the Victron app and connect using bluetooth and it will estimate time left on the batteries charge. This is a feature that our dealer never told us about and there is no information in the owners packet on it. We just noticed it when we were adding the bluetooth dongle to the MPPT.

Hope this helps.

Thank you. Facing same issues with dead house lithium batteries with fridge draw and wasn’t sure how long to run the generator before going to bed. 2021 AI GT

[Xenu672]

I would like to point out that on my airstream there are two things I had to do to make it Lithium ready. You have to reset your solar controller to lithium. This can be done by finding the mppt solar controller box and making sure it’s set to solar and my charger had a jumper cable I had to install for lithium. Without the jumper cable shore power charging (generator charging) would not place a high enough voltage to actually charge it correctly

As the others posters noted for lithium batteries you need to make sure the charging voltage is above 13.6V. Typical lithium charging profiles start at 13.8 and top off at 14.5. To know how long to charge the battery you need to know how much amperage you will be pulling. Then for a typical 30A generator that will charge about 30 A per hour. If you pull 40 amps over the night then run it for 2 hours to give you room.

As an example, in my airstream my fridge and heater running intermittently pull about 8A per hour. Over 10 hours this draws down 80A. Running a 30A generator I would want to run it three hours before bed to ensure I would last the night on one battery

[JoanneAZ]

Thank you for all the posts. Looks like I will need to look for a quieter generator since I will be running it 5 hours a day on cloudy days or replace my fridge with a propane fridge or install an extra lithium battery to make 300A or just keep on driving LOL. I will install the victron app. The voltage equivalents you listed were helpful. I didn’t realize I need to charge to 14+V

[DW 24X]

Thanks for your recent post. I would hope that Airstream would have it setup correctly but I will verify the solar controller.

Also it looks like I should review the auto on auto off set points.

[3OnOurWay]

Do you know we ran into the same, in all of our manuals and information there is an email from Magnum to Airstream to program the custom settings on the inverter for the lithium batteries.

Though in our case our inverter isn’t set to custom so it’s tough? How much do you go exploring and changing when the learning curve is high so I feel your pain we are in a new to us. 2021 GL. Smaller fridge than you guys.

[Xenu672]

Never assume or hope when it comes to the dealer. I’ve had very bad luck with their workmanship. In my case airstream set up the system for agm compatibility and then the dealer dropped in the lithium stuff without bothering to change anything. I had to do my due diligence and check their work to find out the solar charging was setup wrong, the controller wasn’t switched properly and the charge controller didn’t have the jumper in.

[DW 24X]

If anyone has photos or literature on the solar setting and jumper cables, it would be appreciated.

[Rocinante]

Here's a tip: Never have an RV dealer of any kind install a Lithium and/or solar upgrade. They know so little that they don't even know what they don't know, and they care even less about the result. Basic repair services, sure, but don't expect them to properly handle upgrades of this nature. Go find a specialist who knows what they're doing.

Oh, and as an aside, I strongly recommend against changing out your compressor fridge for a propane fridge. The van doesn't have the right holes in the outside to vent that thing, and besides, they are terrible. You can, however, improve both efficiency and performance of your existing compressor fridge by improving ventilation behind that fridge. Airstream does a miserable job of engineering the airspace behind our fridges, regardless of model, so you're going to want to get in there and improve it. Thus far I've used hole saws to drill extra ventilation holes, added a grille at floor level, and insulated the van behind the fridge (there was nothing) so it doesn't suffer as much on hot sunny days, and got noticeable improvements. Next I'll be experimenting by adding fans (hopefully quiet ones!) behind the fridge to encourage better airflow and thus better cooling of those rear coils when it's operating.

[Xenu672]

Originally Posted by DW 24X

If anyone has photos or literature on the solar setting and jumper cables, it would be appreciated.

What are the model numbers of your electrical components (the solar controller and charge converter)? I have a travel trailer and I have the victron mppt solar controller and wfco9855lis charge controller.

[uncle_bob]

Originally Posted by Rocinante

Here's a tip: Never have an RV dealer of any kind install a Lithium and/or solar upgrade. They know so little that they don't even know what they don't know, and they care even less about the result. Basic repair services, sure, but don't expect them to properly handle upgrades of this nature. Go find a specialist who knows what they're doing.

Oh, and as an aside, I strongly recommend against changing out your compressor fridge for a propane fridge. The van doesn't have the right holes in the outside to vent that thing, and besides, they are terrible. You can, however, improve both efficiency and performance of your existing compressor fridge by improving ventilation behind that fridge. Airstream does a miserable job of engineering the airspace behind our fridges, regardless of model, so you're going to want to get in there and improve it. Thus far I've used hole saws to drill extra ventilation holes, added a grille at floor level, and insulated the van behind the fridge (there was nothing) so it doesn't suffer as much on hot sunny days, and got noticeable improvements. Next I'll be experimenting by adding fans (hopefully quiet ones!) behind the fridge to encourage better airflow and thus better cooling of those rear coils when it's operating.

Hi

I'd add:

The propane fridges are going the way of the dinosaurs. Some number of years out, you need a part .... hmmmm .... nobody local stocks those anymore. Ok, order it up .... hmmm ... none in stock anywhere. Ok, put it on backorder. In comes the email "we expect to fill your order in 48 weeks".

While that all sounds a bit much, I've run into the same thing on various similar items over the years. Yes, there are *supposed* to supply parts for a while after you buy something. Apparently a 48 week backorder still meets that requirement.

Bob