How to Interpret GoPower

[Shiny]

Thanks again emers382. Seems your electrical system is working well but hard to know if ours is equivalent or not.

I attached ResMed estimates for AH.

It says an Airsense 10 set to 10 cm pressure with humidifier and heated tube will consume 46 AH. Our 2 AirMinis at the same pressure will use 10.

We seem to both be at ~70% in the morning. Our furnace fan is unlikely to use as much power as your CPAP and everything else was similar so I'm still questioning the health of our batteries and I want to keep investigating.

Mike

[Shiny]

Originally Posted by Randy in Maine

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

Maine is a LONG way from Mancos! We hope to see Maine sometime. We lived in the southern tier of NY for a couple years but never got past Burlington in that direction.

[emers382]

Originally Posted by Shiny

Thanks again emers382. Seems your electrical system is working well but hard to know if ours is equivalent or not.

I attached ResMed estimates for AH.

It says an Airsense 10 set to 10 cm pressure with humidifier and heated tube will consume 46 AH. Our 2 AirMinis at the same pressure will use 10.

We seem to both be at ~70% in the morning. Our furnace fan is unlikely to use as much power as your CPAP and everything else was similar so I'm still questioning the health of our batteries and I want to keep investigating.

Mike

We don't have the heated tubes perhaps that's the difference.

[Shiny]

Originally Posted by emers382

We don't have the heated tubes perhaps that's the difference.

Yes, could be!

I failed to post the attach these ResMed tables. Thanks to NEWYORKHILLBILLY for posting a link to these.

Table says the tube heater does consume a lot of power. Noted!

[KirkB]

Hi Shiny,

I saw your mention of AH which is not displayed on my solar controller (I have the 2014 Escape install, previous models, and 2 6V batteries). If you have calculated the typical overnight AH draw, you can determine if the solar system has replenished the batteries to last another night by checking the AH reading.

My controller panel does not track AH. I have not invested in a battery monitor, so rely on my solar controller to get a rough read out of battery charge levels.

During the day, I look at a combination of voltage level and charging current (amperage) to determine if my solar system is close to recharging my batteries. If I see my solar panel at around 13.6V at midday (assuming bulk charge is complete), with a small (< 0.5A) current, then I know that my controller has completed most of it's charging for the day (the lower the better). If it takes a larger current to reach the target voltage of 13.6, or is at a lower voltage, that is when you might need to give things a boost with your generator, if it is late in the afternoon.

I don't run much on the 12V electric side especially midday, so anything more than a small amperage level indicates to me that the battery is needing charging amps to keep at at the target float charge level, and not fully charged.

I have a smaller panel (either 85 or 90W), so max amps for me is around 5A. I bet people with newer panels see higher charging amp levels during bulk charge in the morning after a high draw night.

Here is a quick summary of how I read my voltage and amperage levels:
- Normal voltage (~13.6V), low amps (<0.5A), adequate sun, charging almost complete.
- Normal voltage (~13.6V), high amps (>0.5A), adequate sun, charging not complete
- Low voltage (<13.6V), high amps (>0.5A), adequate sun, charging not complete.
- Low voltage (<13.6V), low amps (<0.5A), low sun. This is when you can't tell if your system is close to a full charge, if the sun is not out, or you parked in the shade.

Aside from the first scenario, you may want to top up with your generator until you are confident with your solar recharge, and battery state of health. Your definition of low amps and high amps may differ from mine, but hoping this helps you to read your solar controller.

If your batteries are still in good shape (have full rated capacity), you should be OK for a couple of days before topping up with your generator.

Hope this commentary is useful.

[Shiny]

Originally Posted by KirkB

...
During the day, I look at a combination of voltage level and charging current (amperage) to determine if my solar system is close to recharging my batteries. If I see my solar panel at around 13.6V at midday (assuming bulk charge is complete), with a small (< 0.5A) current, then I know that my controller has completed most of it's charging for the day (the lower the better). If it takes a larger current to reach the target voltage of 13.6, or is at a lower voltage, that is when you might need to give things a boost with your generator, if it is late in the afternoon.

I don't run much on the 12V electric side especially midday, so anything more than a small amperage level indicates to me that the battery is needing charging amps to keep at at the target float charge level, and not fully charged.

I have a smaller panel (either 85 or 90W), so max amps for me is around 5A. I bet people with newer panels see higher charging amp levels during bulk charge in the morning after a high draw night.

Here is a quick summary of how I read my voltage and amperage levels:
- Normal voltage (~13.6V), low amps (<0.5A), adequate sun, charging almost complete.
- Normal voltage (~13.6V), high amps (>0.5A), adequate sun, charging not complete
- Low voltage (<13.6V), high amps (>0.5A), adequate sun, charging not complete.
- Low voltage (<13.6V), low amps (<0.5A), low sun. This is when you can't tell if your system is close to a full charge, if the sun is not out, or you parked in the shade.

Aside from the first scenario, you may want to top up with your generator until you are confident with your solar recharge, and battery state of health. Your definition of low amps and high amps may differ from mine, but hoping this helps you to read your solar controller.

If your batteries are still in good shape (have full rated capacity), you should be OK for a couple of days before topping up with your generator.

Hope this commentary is useful.

Hi Kirk,

Thank you for taking the time to read the thread and respond in such detail.

Yes, your guidance is very useful!

I completely follow your logic when in float charging mode and have been interpreting just as you describe in that clearly written section I highlighted.

I'm not sure I've ever observed a bulk charge mode voltage (14.4V) and don't understand the "every morning" as described here by GoPower. At home, my camper is parked in morning shade so I don't see how a bulk charge mode could be effective without sunlight. What's the point of this bulk charge mode if there isn't enough sunlight? I admit total ignorance but is charging at 14.4V without any current useful?

Back to my original question about interpretation of SoC, I read the GoPower (GP-PWM-30-UL) manual again and it's clear. The SoC displayed is based only on voltage (attached).

I don't understand how the battery voltage is measured when the controller is charging the battery but I guess it's irrelevant if the SoC indicated is just a voltage reading.

As you say, I can (and have) estimated AH requirements overnight. If I reset the GoPower AH at night I can compare the accumulated solar charge AH the next afternoon and make a decision on whether to supplement by generator before it gets dark.

The morning after I charged with the generator, the SoC was 75% with corresponding 12.5V. This 25% "draw-down" is at least consistent with my estimated 40 to 50 AH usage and a 220 AH total capacity.

Mike

[KirkB]

Hi Mike,

You have 2 x 190W panels. They might be strong enough to complete the bulk charge 1/2 hour cycle before you get direct sun on your panels. The manual says that if you see a 100% SOC, the daily bulk charge has completed. If not, then it shows maximum of 90% SOC.

A battery which is more discharged will accept more charging current (Amps) at a given voltage. If your solar system can only generate 144 W of charging power, a depleted battery might be charging 12A at 12V. As the battery charges, the charging voltage will increase. A more fully charged battery could charge 10A at 14.4V with the same 144W. The bulk charge may run for a while before the maximum voltage or 14.4V is reached. Once the maximum charging voltage is reached, the amps required to maintain the voltage drops as the battery becomes more fully charged.

So if I see that the solar controller can push the batteries up to the max charging voltage with just a small amount of current, then I know that the batteries are reasonably well charged.

Hope this helps clear up some of your questions.

[Shiny]

Kirk - yes, thanks again and that makes more sense now.

As I now understand:

The batteries are a load that acts like a variable resistor... low R when depleted, high R when full. The supply will be "current-limited" by the available solar power until the battery accepts enough charge to reach the voltage "setpoints" (bulk, float, boost) which are all above the battery's resting voltage at full capacity.

During the bulk phase, the supply will be set to a max of 14.4V for 30 minutes each "morning", then reduces to 13.7V.

If I see 100% SoC, the bulk mode was completed, the system is in float mode and the battery is charged enough to exceed 12.8V. 12.8V may not correlate with fully charged but is at least at a consistent level and close to full.

If I see 90% and 13.6V, the battery is full but the bulk mode did not complete. I don't know why the bulk mode wouldn't complete, though. I've never seen 90% and low current in full sun.

As to the "health" of my battery (actual capacity), the AH provided during the day only indicates the overnight power usage IF there's enough sun to fully replenish the battery. If the AH indicated is below my guessed usage, I can use the generator to add margin/confidence.

If I really want to know the AH consumed, I need to invest in a shunt-based monitor.

Meanwhile, as long as we stay above 12.2V after a cold night, we are good.

[Brian B-P]

Originally Posted by Shiny

As I now understand:

The batteries are a load that acts like a variable resistor... low R when depleted, high R when full.

You can think of it that way, but it would more accurate to consider the battery as a fixed resistance, but as the battery's state of charge increases its internal voltage (what you see at rest) increases; since the charging current depends on the resistance and the voltage difference between what is applied and the internal voltage, as the battery charges up from a constant-voltage source the current drops.

Originally Posted by Shiny

If I really want to know the AH consumed, I need to invest in a shunt-based monitor.

True.

[Shiny]

Thanks Brian

I hope my inaccurate "model" doesn't confuse others.

I'd need a direct line to a team of very patient EEs to really grasp all this.

For now, 12.8V is declared FULL by the GoPower controller, Kirk's interpretation matrix is a great guide, and I need a battery monitor that can tell me AH in and AH out.

Great to have you all as a resource!

Mike

[Jack!]

We are building our new 5.0 and we are building in a little more power capacity. Plan on more dry camping, want less generator use, want to maximize solar within reason but have capacity for more as panel tech improves, and don't want power watching to be a major activity/concern. Not seeing "voltage monitoring" very accurate in our old trailer, as something is always adding or using power, purchased a Thornwave shunt. It has more features we liked, saves 3 yrs of data, supports switch relays, and longer range bluetooth so we check power occasionally from the truck while traveling. We will have the widened U-Dinette
and don't mind giving up some space to have 4-heated BB Li batteries there. Like the BB bms safeties. Going with ETI's GP 2-190 watt panels & a zamp where we can add a 100watt portable, as necessary. Also, having ETI wire up the standard GP PWM solar controller without cutting the hole in the bench to mount it. We will replace it with a Victron MPPT 100/50 blue tooth solar charger, which can support up to 700 watts of solar. This gives a little room to grow as panel tech evolves into the future. Costs are higher but this setup should help met the power goals we want.

[David Hendrickson]

I recommend getting a Victron SmartShunt. It monitors charging rate and usage in real time.

[Centex]

Originally Posted by Jack!

.... purchased a Thornwave shunt ....

I'd not seen previous mention of that particular alternative on this forum, upon looking at the manufacturer website and documentation it looks like a very nice unit, certainly a competitive alternative to the Victron SmartShunt, offering at least equivalent features with maybe a few more it seems:

Link to Thornwave Labs Bluetooth Shunt webpage

Thanks for the mention, having choices is always good IMO!

[Perry Butler]

Originally Posted by Jack!

Also, having ETI wire up the standard GP PWM solar controller without cutting the hole in the bench to mount it. We will replace it with a Victron MPPT 100/50 blue tooth solar charger, which can support up to 700 watts of solar. This gives a little room to grow as panel tech evolves into the future. Costs are higher but this setup should help met the power goals we want.

We went over two years with the GP PWM zip-tied underneath the rear bench of the u-shaped dinette. OTOH, at four months of ownership we installed a Victron BMV-712 battery monitor, so the readout on the GP was essentially worthless.

When our batteries failed last winter I removed the GP PWM SCC and installed a Victron 100/30 SCC. Because we zip-tied the GP SCC there was no empty hole in the dinette after installing the Victron SCC.

Only after replacing the GP SCC with a Victron do owners fully understand why I said to zip-tie the GP SCC underneath the bench.

Enjoy,

Perry

[Jack!]

Originally Posted by Centex

I'd not seen previous mention of that particular alternative on this forum, upon looking at the manufacturer website and documentation it looks like a very nice unit, certainly a competitive alternative to the Victron SmartShunt, offering at least equivalent features with maybe a few more it seems:

Link to Thornwave Labs Bluetooth Shunt webpage

Thanks for the mention, having choices is always good IMO!

We looked at both options carefully and had the same conclusion. Thornwave looks to have the lead at this point and not being a huge investment we are giving the smaller guy a shot this time. They are coming out with a wireless BT panel soon, if one likes the data on the wall in any location you like. No wiring is handy. We also liked the many reviews on longer BT range, being able to setup a remote relay switch, & 3 yrs of data history.

[Centex]

Originally Posted by Jack!

We looked at both options carefully and had the same conclusion. Thornwave looks to have the lead at this point and not being a huge investment we are giving the smaller guy a shot this time. They are coming out with a wireless BT panel soon, if one likes the data on the wall in any location you like. No wiring is handy. We also liked the many reviews on longer BT range, being able to setup a remote relay switch, & 3 yrs of data history.

I can certainly understand all of that being attractive.

I happen to have the Victron BMV 712 w/shunt awaiting installation along with the VictronSmart MPPT 150/60 (larger array than your plan). For me there's a bit of attraction to having all my 'solar BT apps' in the same 'ecosystem' (interface consistency factor - hopefully easier learning and remembering for my old brain) and I did prefer a redundant hard-wired monitor readout/control panel independent of BT technology.

All that notwithstanding the Thornwave does strike me as a very nice alternative, especially for those with a non-Victron controller of whatever brand (certainly lots of other alternatives for that item). As indicated, I think it's great to get leads on alternative components here, having good choices is always good in my book, so thanks again!

[Shiny]

Originally Posted by Centex

I can certainly understand all of that being attractive.....

Agree... thanks Jack!!

I'm considering adding a monitor so it's good to learn of this option. Installation looks easy and the BT interface to a phone app eliminates wiring to a display. This also enables feature updates by software, not hardware. Their wireless touchscreen panel is another easy-install idea if it becomes available and isn't too complicated. The datalogging capability could provide hours of educational entertainment!

I was leaning toward a Balmar SG200 as it has a simple display and a BT interface for extra dollars. It also claimed to monitor battery capacity (health) over life which was an attractive feature for me as that's still an unknown for us on our used camper. I'll now look at the Thornwave system and compare. The Thornwave (at least the shunt) would cost less.

Mike

[Jack!]

Originally Posted by Perryb67

Only after replacing the GP SCC with a Victron do owners fully understand why I said to zip-tie the GP SCC underneath the bench.

Enjoy,

Perry

I get it Perry & doing the same. Asked to ship our Victron, for ETI to install, but best they can do is provide the GP charger uninstalled or install it wired up & working without cutting the bench hole. I chose the latter as the Victron MPPT will wire up the same and can be attached inside the bench in the same spot. ETI was good about providing what choices they can & had a good fallback in this case.
EBay is the next stop for the GP charger...