Solar power capacity

[BC88]

I now own a 2023 Keystone Cougar 25RDS, equipped with the 400i Solar pkg (400 watts of solar) and 2 lithium batteries. This past weekend, while camped in full sun all days, we had problems with battery power. The main draw was our 12v fridge set on off-grid mode, and my CPAP machine at night. Other draw was minimal, and batteries lasted only about 30 hours. Does that sound right? I was expecting 2 - 3 days of off grid capacity.

[Max23]

I have exact same setup. Using a small fan, C-Pap and fridge. I used 50% of that same battery capacity from sundown to sun up. Totally depends on what your running but that sounds exactly right. Nice thing is, you'll be surprised at how fast that will recharge in full sun. Takes more power than you thing to run things. I leave mine sit in the driveway between uses (if for short periods) with fridge running so as to not have to empty and refill every time and uses about 15 to 18% of my capacity. Sun has it charged in no time next day. So ya, short answer is what you got is about right. I did forget to mention, we were also running the furnace, so a little more draw there. Again, however, charged to full by mid afternoon next day. Could run for days that way.

[snoobler]

My CPAP uses about 0.2-0.3kWh/night. That's about 25% of the capacity of a 100Ah 12.8V LFP battery.

We have a small 12V cooler that runs 60W continuously. That's 1.440kWh/day... that's 1.12X the capacity of a 100Ah LFP battery. In those two items alone, I've consumed 1 and a third of my battery capacity.

If you have an inverter ON, it consumes power even if it's not in use.

You may THINK you're not using much power, but it adds up.

It helps to get educated on the consumption of the various devices - voltage * current for power (Watts), or even better if the device lists Watts.

Your 400W array flat on the roof can produce 1.2-1.6kWh/day depending on shading and solar availability. If you have 2 100Ah batteries, then you can only reliably charge one per day at 1.28kWh assuming you don't use any power at all.

Spitballing: Assuming the PV provided enough to recharge ONE battery, you used three batteries worth of energy in 30 hours. That's 1280Wh * 3 / 30 hr = 128W on average at all times. That's basically the equivalent of two 60W incandescent light bulbs on for 30 hours.

[firestation12]

A Victron shunt installed between your battery’s negative post and the camper’s grounding point creates a measurable pathway of all power entering and exiting your batteries. The Bluetooth feature allows your smart phone to access the moment to moment status of charge of the batteries. At a glance you’ll know the state of charge and whether you are trending towards gaining or losing. Think of it as a fuel gauge for your battery. I’m not familiar with the solar flex system, maybe you already have something like the Victron shunt. One simple interim solution would be to use a small generator (2200 watts) for a few hours perhaps every other day.

[snoobler]

Originally Posted by firestation12

A Victron shunt installed between your battery’s negative post and the camper’s grounding point creates a measurable pathway of all power entering and exiting your batteries. The Bluetooth feature allows your smart phone to access the moment to moment status of charge of the batteries. At a glance you’ll know the state of charge and whether you are trending towards gaining or losing. Think of it as a fuel gauge for your battery. I’m not familiar with the solar flex system, maybe you already have something like the Victron shunt. One simple interim solution would be to use a small generator (2200 watts) for a few hours perhaps every other day.

+1

In addition to that, the Shunt and MPPT can be setup in a VE.Smart network where the shunt feeds the MPPT the true battery voltage and net current. This makes the MPPT charging more accurate and can encourage longer bulk phase and higher current during absorption phase.

The only caveat is bluetooth range. The transmitter is on the shunt itself, and Victron confirms its proximity to the induced magnetic field from current flowing through the shunt interferes with the signal. BT range of only 10m is pretty typical.

The BMV-712 is essentially the smart shunt with a remote display and control panel. Its BT transmitter is in the display, so the BT range is dramatically better, and you have the benefit of a remote display. It also works in a VE.Smart network and can be connected via smartphone and tablet to VictronConnect for monitoring and programming. Spendy though.

Either version can be used with a battery attached temperature probe and feed temperature data to the MPPT for temp comp on Lead acid as well as low temperature charging protection on LFP.

[NH_Bulldog]

The SolarFlex 400i system comes with a Victron Smart Shunt. You can connect to your smartphone for real-time usage data to see what is coming in, what is going out and how long your batteries will last.

[snoobler]

Originally Posted by NH_Bulldog

The SolarFlex 400i system comes with a Victron Smart Shunt. You can connect to your smartphone for real-time usage data to see what is coming in, what is going out and how long your batteries will last.

Awesome.

Hopefully, they instruct users to setup a VE.Smart network between the two. Very good stuff.

[NH_Bulldog]

The manuals, set-up guide, and quick start guide are all in the Keystone site, and in hard copy format in the trailer documentation that comes with it.

[firestation12]

Quote:
by NH_Bulldog
The SolarFlex 400i system comes with a Victron Smart Shunt. You can connect to your smartphone for real-time usage data to see what is coming in, what is going out and how long your batteries will last.
Awesome.

quote:
by Snoobler
Hopefully, they instruct users to setup a VE.Smart network between the two. Very good stuff.

Thanks guys, looks like we have a fan club of Victron products here. Any thoughts for BC88 about interim fixes for his running out of power after 3 days??

[NH_Bulldog]

Not a fan of Victron, that is just what comes with the SolarFlex 400i system, and he actually ran out of power after 30 hours not 3 days. My mention of the shunt was simply to direct him to an available resource he has on hand to actually see exactly what is using what and drawing his battery/batteries down so quickly.

There are a lot of variables in play, like what type of batteries, what capacity and how many does he have? Is he running his CPAP off 12v or from the inverter? Does the CPAP have a humidifier (those draw a lot of power). Has he confirmed that the solar panels are sending power to the battery/batteries? What else is he using (TV, stereo, coffee maker, toaster, lights, what pump, etc.)? Is he running the furnace, or tank heaters, or battery heaters (if he has lithium batteries). By far the biggest draw is going to be the 10 cf 12v compressor refrigerator. Most people only consider the running amps, but that spikes when it goes into defrost mode. That is related to how many times the doors are opened and closed, how much warm/moist food is put in there, etc.

Until the OP answers these kind of questions, all we can do is take shots in the dark as to what might be happening.

[firestation12]

Originally Posted by NH_Bulldog

Not a fan of Victron, that is just what comes with the SolarFlex 400i system, and he actually ran out of power after 30 hours not 3 days. My mention of the shunt was simply to direct him to an available resource he has on hand to actually see exactly what is using what and drawing his battery/batteries down so quickly.

There are a lot of variables in play, like what type of batteries, what capacity and how many does he have? Is he running his CPAP off 12v or from the inverter? Does the CPAP have a humidifier (those draw a lot of power). Has he confirmed that the solar panels are sending power to the battery/batteries? What else is he using (TV, stereo, coffee maker, toaster, lights, what pump, etc.)? Is he running the furnace, or tank heaters, or battery heaters (if he has lithium batteries). By far the biggest draw is going to be the 10 cf 12v compressor refrigerator. Most people only consider the running amps, but that spikes when it goes into defrost mode. That is related to how many times the doors are opened and closed, how much warm/moist food is put in there, etc.

Until the OP answers these kind of questions, all we can do is take shots in the dark as to what might be happening.

Oops, thanks for the correction….30 hours not 3 days. I think there was somewhat of a consensus between post #2 (who has the exact same set up) and Snoobler post #3 who provided a more detailed explanation that the OP’s battery drain was predictable and to be expected. I think that is what more in line of what was being asked i.e. “Does that sound about right?”. While the OP could respond to the many variables mentioned, it seems unlikely the technical answers would be of help. I could be wrong. I’m still anticipating to hear if anyone has a short term fix.

[NH_Bulldog]

Easy fix? Generator, as you suggested. That’s my go-to.

Everyone is also assuming that the solar panels are connected and charging the batteries, but we don’t know that for sure.

[snoobler]

One or more of:

Reduced utilization
More solar
Generator

[JRTJH]

Originally Posted by snoobler

One or more of:

Reduced utilization
More solar
Generator

Add bigger battery storage capacity to that list, but probably not "really effective" without "more solar"...

[snoobler]

Originally Posted by JRTJH

Add bigger battery storage capacity to that list, but probably not "really effective" without "more solar"...

I deliberately excluded that because it's typically the most costly option, and it only delays the inevitable.

PV determines how much energy you can use per day.
Battery determines how long you can go between charging.

[firestation12]

I liked the simplicity of this statement. It’s something we should use exactly as quoted.

[QUOTE=snoobler

PV determines how much energy you can use per day.
Battery determines how long you can go between charging.[/QUOTE]

[snoobler]

Originally Posted by firestation12

I liked the simplicity of this statement. It’s something we should use exactly as quoted.

Thanks. I participate in a DIY solar forum, and the number of stories of folks adding batteries to address their batteries running out of juice, yet still running out of juice... just later... and their willingness to keep doing it... was staggering. I had to boil it down to something simple to convey the point.

The goal of off-grid PV power systems is to permit perpetual use without external charging. RV boondocking usually has an endpoint, so it is different, but the same principles apply:

1) Either estimate your consumption in an energy audit or directly measure it with something like a kill-a-watt.
2) Define your use case (3, 5, 7 days or perpetual boondocking)
3) Size your PV and battery according to the demands of #2.

[NH_Bulldog]

Sounds perfectly logical. I think most people fail to understand the limitations of the factory systems and expect more than what the system is capable of producing.

For what it’s worth, Keystone says about the SolarFlex 200: you have everything you need to make a stop during your travels, open the slides, prepare a meal or grab a nap.

In the SolarFlex 400i system: This economical and robust package will get you off the grid in good conditions with a reasonable (but not endless) energy supply.

In the SolarFlex 600i-L system: equips campers for extended off-grid stays. 600 watts of solar collection and a 50A charger will rapidly refill batteries as well as capture and convert more energy on days when conditions are less than ideal.

At the bottom of the document, they have a disclaimer: *Performance will vary based on available sunlight, battery size/type, and power usage.

None of the Keystone systems proclaim unlimited off-grid capability.

[bmusser]

We have a 2022 Cougar with solar. What equipment /devises can actually be run off the battery?

[440scout]

Originally Posted by BC88

I now own a 2023 Keystone Cougar 25RDS, equipped with the 400i Solar pkg (400 watts of solar) and 2 lithium batteries. This past weekend, while camped in full sun all days, we had problems with battery power. The main draw was our 12v fridge set on off-grid mode, and my CPAP machine at night. Other draw was minimal, and batteries lasted only about 30 hours. Does that sound right? I was expecting 2 - 3 days of off grid capacity.

If it was me, I would get a good clamp-on meter (around $45. on Amazon)and start testing the solar input and output voltages at the solar charge controller. Depending on the rated voltage of your solar panels, thats what you should see at the input side of the controller, maybe 21 volts if the panels are connected in parallel and if connected in series, double that. When your batteries are weak you should see the most amps going to your batteries. On average a single 200 watt panel can output around 10 amps but you've got 400 watts so 20 amps on a sunny day. Clamp that meter around the positive wire to the batteries on the output side of the charge controller and see what you've got. This testing is a good start to troubleshooting but there's more you can do with that meter on the roof at each panel and at the batteries connections. Please let us know your test results. Good luck.