How to Interpret GoPower

[Shiny]

Warning: long post, many questions

Please forgive if this duplicates posted info but I could not find it..

Context: newbie to solar and power management systems, trying to build confidence when camping without shore power as we have 2 mini-CPAPS that draw 5 or 6 AH each overnight.

Last outing we used the inverter for our CPAPS, furnace ran, fridge was on propane, water pump was left on. We went to bed with 88% SoC indicated, woke to 63%.. seemed acceptable but not much margin. We now have DC-DC converters for the CPAPs but I want to better understand the GoPower indicator and what we can do to conserve.

Trailer Config (as-manufactured by ETI): 2 6V Flooded Batteries, 2 190W rooftop solar panels, GoPower Solar Controller, 1500W Inverter

Questions:

1. Is my "safe" power use overnight ~100 AH?

If so, I feel the correlation between GoPower SoC and AH to recharge are inconsistent...

2. Can I trust the "Capacity" indicator on the GoPower Controller?

As I understand, the controller displays SoC as a %. Is this SoC estimate accurate when both charging and under load? Does it automatically set the 100% level? If so, how do I know the battery hasn't lost capacity?

3. Can I use the AH indicator to measure power draw since last reset?

I can reset the AH using the app when the SoC hits 100%. After reset and then charging to 100%, do I interpret the indicated charge as what I used from the battery overnight or does it also include power used to "maintain" the battery after replenishing?

4. Is there any way to measure power used per appliance without something "direct" like a Victron 700 or 712 battery monitor that directly measures current?

5. Has anyone tabulated current draw or power usage per appliance?

For example, what is the AH consumption of the water pump? heater blower? fridge when running on propane?

6. How much power does the inverter consume if nothing is connected?

We have a microwave...when the inverter is on, the microwave gets power (the display is a good way to know the inverter is on). How much power is it consuming just idling? Are there other appliances/systems that will pull power (idling or auto-switch to AC) from the inverter when it's on even though I'm not using them?

If you made it this far, congratulations and I am grateful for anything you can offer.

Mike

 

[alanmalk]

...
1. Is my "safe" power use overnight ~100 AH?
...
Mike

Just a partial answer to your questions since my time is limited.

For general information, it is sometimes very helpful to understand the difference between Amps and Amp-Hours.

Per some website definitions:
1 amp hour is defined as 1 amp of current expended for 1 hour.
Or in other words, power used right now is "Amps". This what you measure with multi-meters or more elaborate shunts - like Victrons.

Power used over a period of time, over night for example, is "Amp-Hours". You measure this with your watch, or more easily with Victrons.

Your newish, properly charged and maintained batteries are good for 220 AH. But pulling all 220 AH will shorten their total life span rather significantly. Pulling half, or 110 AH, followed by a timely recharge, will maximize the battery life. Going in-between is not the kiss of death, and for a pleasant camping experience my Opinion is: use what you need and put an extra dollar in the budget for new batteries when that happens.

 

[Perry Butler]

First of all none of them are accurate, but they are relative.

We found our GoPower solar charge controller's information to be essentially as simple as it gets. As long as everything is working properly it's fine. Then we spent four days trying to figure out why our batteries were not charged and had to be replaced, when the camper was only 3 months old.

So we purchased a Victron Smart BMV-712 battery monitor and got a lot more information. It's not perfectly accurate with every readout, but relative enough to be worth the money for us. The 712 was worth every penny for us. It allowed me to find that after two years our WFCO charger failed, and decided to provide 21 volts to our batteries, smoking them. It's rare, but it happens. Our WFCO charger has been disconnected since we purchased our third set of batteries.

At the time of the second battery failure last February, I decided to replace the GoPower SCC with a Victron 100/30 SCC. It gives historical data that the 712 doesn't provide. We also have a Victron 100/20 for our portable solar panel. The 712, 100/30, and 100/20 all talk to each other as a system.

It depends on how much information you want, but if your can keep your leaded batteries above 40% SOC (some say 50%) you should be fine with two 190 watt panels. We had the discretionary money, and I had the knowledge (or willingness to learn) where the Victron units were valuable to us.

OTOH, my Opinion is, I'd camp more before I replace anything.

Enjoy,

Perry

 

[Shiny]

Thanks both..

I can complexify anything simple so I appreciate the "buy new batteries when mine are dead" but I'm curious how others interpret and use the information available from the GoPower controller.

Like most that have invested in a solar system, I just want to go camping and not have to fire up a generator to bring the batteries up before going to bed.

The solar system works great so far...with good sunlight we have seen the SoC recover to 100% by 10AM and stay there all day. And yes, if it's overcast, I can and will use the generator.

We need the CPAPs, the fridge, and heater at night. So I'm simply trying to learn how to assure we have sufficient capacity to go overnight without wondering if recharging a cell phone or turning on the audio system or leaving the water pump on will leave us gasping for breath at 3AM.

So far, I think the GoPower SoC indication may be inconsistent with the AH reported.... but my memory is questionable. For example, I recall seeing the battery depleted to ~60% capacity in the morning, then seeing ~40 AH from the solar panels to recover to 100%. If my batteries are indeed 220 AH, I expect that 40% recovered to be 80-90 AH, not 40...

I also have concluded the battery voltage readout on the GoPower is never "static" and is therefore not a great indicator of SoC.

Before I spend money on a Victron or similar monitor with more accuracy, I figured I'd ask those with more experience.

I do, however, like the "go camping more" before making any changes answer.

With exception of the "greedy" appliances (AC, microwave, Keurig), we have not had any issues to date. We've now spent 13 nights on 4 different trips without running out of battery power so to date are happy with the trailer config being a good fit for what we need.

 

[alanmalk]

...

I also have concluded the battery voltage readout on the GoPower is never "static" and is therefore not a great indicator of SoC.
...

A major issue with converting a lead-acid voltage into a SoC is the false reading you get if the battery is being charged or discharged when the reading is taken. You must totally rest the battery - no charge and no discharge - for a minimum of 15 minutes, and preferably an hour or more - before using the voltage tables to estimate SoC. Of course, enforcing a rest period while camping is not practical. The other issue is that as the battery ages it has less capacity, so when half of its life is used up, 100% full is not 220 AH, but rather 110AH. At some point you will wake up after a normal evening with a dead battery. Pull out the credit card and the problem is solved.

 

[Shiny]

..... You must totally rest the battery - no charge and no discharge - for a minimum of 15 minutes, and preferably an hour or more - before using the voltage tables to estimate SoC. Of course, enforcing a rest period while camping is not practical....

Consistent with what I've read, thank you.

So what is the GoPower controller using as a measure of SoC?

Is it just assigning 100% to the highest voltage it saw in the last week or something? As I understand, it only totally stops charging/maintaining when it's dark. And then, the battery has some load so it seems there's never an opportunity for a "static" or "at rest" voltage measurement.

Now you're making me wonder if my batteries are already half dead!

Hmmmmm....

 

[richm]

6. How much power does the inverter consume if nothing is connected?

The GP-1500TS data sheet shows the 'no load current' is <0.9A. So it would consume a maximum of 22 amp hours per day when nothing is connected. It's possible to turn the inverter off to save energy.

 

[Perry Butler]

The GP-1500TS data sheet shows the 'no load current' is <0.9A. So it would consume a maximum of 22 amp hours per day when nothing is connected. It's possible to turn the inverter off to save energy.

I just completed a week of no charging with our roof solar or WFCO, and according to our Victron 712 battery monitor used 119 amp hours for the seven days. The daily use by the fridge (it ran on 110 but the controls are 12v), LP detector, water pump (flushed the toilet perhaps once a day), and any other items I've missed, was about 17 amp hours a day. It took less than a day (I checked at about 4 pm) for our theoretical 465 watts on the roof to get our Soneil SiO2 batteries into float. According to Soneil's charts we were 95% full by sundown and completely full by 10 am the next day when I checked again.

In all honesty, once a day I turned the solar back on for about 5 minutes to see how the panels performed in the middle of the day, so the actual ah's used would be perhaps 1-4 ah's higher.

Enjoy,

Perry

 

[alanmalk]

...
Now you're making me wonder if my batteries are already half dead!

Hmmmmm....

Half dead...
That could be reworded as "half charged" or "half capacity of new".
Half charged can be determined by the resting voltage - easy enough to do at home when not camping and after sunset.

Half original capacity, or "do the batteries only hold 110AH when full", is more difficult to determine. You have to measure the outgoing Amp-Hours starting at full charge and going down to under 12 Volts. This is where a AH meter comes in very handy (Victron is mentioned a lot on this forum).

Otherwise you have to use a constant load (pulls a constant AH current regardless of the voltage) and a timer. Constant loads are not a consumer item (easy enough to make if you have modest electronic skills). The timer would be even more complicated - has to shut off at a known voltage. Too messy.

The simplest answer to the "half of original capacity" question is: Do the batteries give me sufficient power for a typical camping trip? No quantitative answer for this but try taking a voltage reading in the morning before the sun hits your solar, and before you start using the water pump, furnace, fan, etc. Yes, the fridge, propane detector, and other small devices are still drawing power so not a true "resting" voltage - but close enough for government work, as they say. If above 12.3 then you are probably in good shape. If under 12.2 then it may be time to look into new batteries. Use a reasonable quality multi-meter rather than GoPower readings, just to be safe.

Speaking for myself only: I don't have a Amp-Hour meter. I do have a constant load somewhere in the junk room but no intention of measuring my batteries. I do have 7 year old AGM (200 AH) batteries which performed fine last week (furnace on 2 hours per day, fan on 30 minutes, water pump for 15 minutes, fridge&lights&misc low drain devices 24 hours). I was parked where the 160 watt panel was mostly in the sun. Everything worked, camping was good and fishing even better. New batteries are in the budget, probably sooner than later.

 

[Shiny]

Thanks again to you both!

Perry - I really appreciate the data. You are much better at conserving power than we are but your numbers are encouraging.

Have you measured your furnace load? maxi-fan? any other?

Even with our expected 12-15 AH CPAP drawdowns, your numbers suggest we SHOULD have plenty of margin unless the furnace is super greedy or as Alan clarifies, our batteries aren't really getting charged or have lost significant capacity. Both are unexpected as the trailer is a 2020 with little use... but I don't really know the history as we bought it used earlier this year.

Alan - I have been lazy but will get out my voltmeter and get a more direct reading on the battery. Hopefully the GoPower reading is close enough. If not, the Victron monitor may be worth it to me. Thanks for the guidance on a target for lower "safe" voltage.

More importantly, I have enough guidance from both of you to better assess both our charging system and our batteries. I have to believe the GoPower AH readings will provide insight into my power consumption but if I continue to see a discrepancy between the AH to charge vs the SoC readout I will have to dig in and find out why.

We are headed to the Frying Pan tomorrow for 3 nights, will give me a chance to learn more. Hoping for aspen colors but we are probably a little early still.

Mike

 

[alanmalk]

...

We are headed to the Frying Pan tomorrow for 3 nights, will give me a chance to learn more. Hoping for aspen colors but we are probably a little early still.

Mike

Some honest cold air heading to Colorado on Monday - should be a good opportunity to test your furnace and its impact on the battery.

FYI, found my old notes. My heater fan uses 2.75 Amps. My water pump between 2 and 4.5 Amps depending on load, 7 lights use 1.5 Amps, Max fan 0.3 to 3.75 (low to high).

 

[Shiny]

Thanks Alan!

Yes, we are bringing the jackets....and the generator.

If (BIG IF) our batteries are still good for 110 AH we should be fine based on your and Perry's numbers...

As to cold, we're actually predicted to get some rain tonight in Montrose. That's a blessing. But you know how it is here... the 4 seasons are summer, more summer, winter, and more winter.

Hopefully we won't be turning around for snowpack over McClure Pass, though... I've got boundaries.

 

[Shiny]

The GP-1500TS data sheet shows the 'no load current' is <0.9A. So it would consume a maximum of 22 amp hours per day when nothing is connected. It's possible to turn the inverter off to save energy.

Thank you for the current value.

Yes, we figured out how to switch the inverter on and off...had to read the book but it was there. The GoPower app is the easiest way for me.

 

[Shiny]

Good news is we had enough battery to get us through the night with 2 CPAPS and heater running. It got down to 25 one night so all was good. The furnace worked well.

My statement earlier was "We need the CPAPs, the fridge, and heater at night.....to assure we ... go overnight without wondering if ...will leave us gasping for breath at 3AM."

True story- I woke from a dream about gasping for breath in a department store. It was 4AM. My CPAP wasn't pushing air. The battery was down to 12.4V so I was concerned but I went back to sleep without the CPAP.

I now think the battery hadn't been fully charged by the solar that day and I had no way to know this. The CPAP had come unplugged! So the next night I ran the generator for about 2 hrs before sunset to add margin. I slept until after sunrise so have no idea how low the battery voltage dropped.

I still have no idea how much power we are using nor how healthy our batteries are. I don't think the GoPower controller is easy to interpret and I don't trust the SoC readings. When it reads 100% with the panels charging and voltage well above 13V, I don't know what it means.... I will read the book and seek more direct help from GoPower if I remain uncertain.

I will probably buy a battery monitor to gain confidence. I'm leaning toward the Balmar SG200 as it claims to monitor both SoC and "health" (degraded capacity) of the batteries. If I can measure the AH consumed I think I'll have a much better chance of making "informed" decisions about our power use and batteries.

 

[Randy in Maine]

I am waiting for my 21NE and still camping in an older "Shadow Cruiser" with a single six year old Walmart 12 volt deep cycle marine battery (size 27) and a 100 watt Renology suitcase solar panel to charge it. I have a $15 LED voltmeter wired (with a 12 volt socket and 2 USB charge ports) into the 12 volt circuit that powers up my ReMed Auto 10 CPAP machine from the battery. I don't use the trailers 1000 watt inverter. I use the 12 volt power supply for the ResMed machine (I got from Cpap.com ~$80 about 5 years ago) and it has never failed me. Some times the voltage in the house battery drops to around ~11.3 but the cpap has never had an issue with power source.

For the record, I don't use the heated humidifier in the cpap when camping or at home so I probably draw less power to run it. Plus we only have one machine so your mileage may vary.

I think you may be using a fair amount of battery power to convert your 12 volt battery set up into 1500 watts of AC from the inverter and then back to DC for the cpap machine.

I will be setting up the new Escape just as you are with the single 190 watt solar panel and the 2 golf cart lead acid batteries. I will have a pair of 12 volt sockets near the bed.

Montrose is pretty nice. I lived out in Mancos for a while in the early 80s. I liked it!

 

[cpaharley2008]

Yes, I agree, DC to AC back to DC wastes energy....

 

[emers382]

Yes, I agree, DC to AC back to DC wastes energy....

As do I, not having an inverter we purchased the same 12 volt to 24 volt converter for Beth's Airsense as mentioned above and have used it successfully for three years. The lowest I've seen the battery in the morning was a recent trip where it was 69% according to the GoPower, and that's still using the humidifier.

 

[Shiny]

Randy - thanks for sharing your experience using a separate battery for the CPAP. I actually did the same when we were tent camping a few years back, so I get it. Our trailer has 12V outlets on both sides of the bed which is an incentive to use the trailer's battery.

We use the Airsense 10 at home but MUST have humidity so we use the ResMed AirMini when traveling/camping. They work well, are very small, and most importantly, have a cartridge that increases the humidity without consuming power. ResMed does not give them away but they need MUCH less power than the AirSense 10.


cpaharley2008 - understood and agree.. the ResMed AirMini devices are 24V. Our first few outings, we used the inverter but now have DC/DC converters in the hope of improving efficiency. I asked a lot of questions in a CPAP thread here.



As to the GoPower interpretation (subject of this thread), I logged readings for our 3-night trip to help me learn.

I think the only time I get a "clean" voltage reading is when it's dark. I'm not sure about the "%" readout but have more confidence in this when it's dark. This was no problem at night but I never wake before sunrise so unfortunately, I have low confidence in the morning readings.

As to night-time "loads, we kept the furnace at 65-67 overnight, water pump on and off as needed, lights, and our CPAPs. Fridge was on propane, "background" stuff like the gas monitor and system controls were on. We never turned on the inverter.

My estimate of just the "overnight" power demand is ~40 AH (attached).

My logged battery voltages and GoPower capacity estimates are also attached.

My conclusions:

1. I have reasonable confidence in the GoPower voltage and capacity readings taken in the dark. I don't know how it establishes "100%", though... Nor do I understand if I can trust "100 %" when the panels are charging the batteries.

2. You may have to wake up before sunrise to know how much you depleted the battery overnight. Once there is light, the solar charge raises the voltage. As above, I'm not sure how GoPower handles the "%" readout when charging.

3. If any doubt about the solar charge during the day, I need to run the generator before bedtime or at least decide after dark.

4. An AH monitor on the battery would provide MUCH more insight.

5. I still have no idea if my battery is "healthy" (AH vs %) but it's healthy enough to get us through the night if we start with a good charge.

Mike

 

[Shiny]

As do I, not having an inverter we purchased the same 12 volt to 24 volt converter for Beth's Airsense as mentioned above and have used it successfully for three years. The lowest I've seen the battery in the morning was a recent trip where it was 69% according to the GoPower, and that's still using the humidifier.

Thanks for this.

What batteries do you have?

Do you know the charge level when you went to bed? Do you monitor/manage this? If so, how?

Was the furnace running when you saw the 69%?

We did purchase a DC/DC converter for my wife's Airsense as a backup plan but we both did fine with the AirMini this trip. ResMed literature indicates power consumption for an Airsense with Humidity is ~10X that of the AirMini.

 

[emers382]

Thanks for this.

What batteries do you have?

Do you know the charge level when you went to bed? Do you monitor/manage this? If so, how?

Was the furnace running when you saw the 69%?

We did purchase a DC/DC converter for my wife's Airsense as a backup plan but we both did fine with the AirMini this trip. ResMed literature indicates power consumption for an Airsense with Humidity is ~10X that of the AirMini.

2 x standard Escape provided 6 volt

No I didn't check the level before bed but we'd only used lights and the little power going to fridge on propane, propane detector, water pump, and maybe a phone or two charging.

No furnace running as we haven't really been able to camp needing furnace since last March since we cannot enter your country to enjoy some winter time in the south. Today we should have been at the Mississippi River Rendezvous

The 69% could have been a bit lower before it was light out, maybe an hour or two before I checked it.

We haven't even considered buying a mini AirSense, just use the same AirSense 10 whether at home or traveling, with power of course plugged in, or without using the 12-24v converter.