I don't understand the Inverter Panel during Operation

[GaylesFaerie]

Hi, my 2012 R27 is currently on the hard in CT. It has a TruePower 1500 Watt Inverter with a separate ProNautic Battery Charger. All worked fine during the fall season.

During Covid quarantine I regularly go down to make progress where I can on winter projects. I have a Solar panel (not covered) to keep the batteries topped off during the winter. While onboard during a weekend I often bring lunch. Today's meal was a frozen dinner that I wanted to heat up with the Microwave running off the Inverter. Long story short, it worked. But, I was somewhat confused on the road to success and was hoping for some education on operating the Inverter and interpreting the Remote Operation panel.

Today when I went down to the boatyard, it was sunny, windy and we had snow on the ground and 40 degrees temp at 1:00pm. The boat was covered, except for my solar panel. The Victron battery monitor showed 100% SoC on the 3 house batteries totaling 330 amps. I switched the Inverter Service disconnect to ON. Then I went to the Inverter Remote panel (pictures below) and turn it on and it showed roughly 50% DC Input Voltage. Question 1: what exactly does that mean? Is the inverter only getting 6-7 volts?

Next I switched my rotary AC source switch to Inverter which showed green (no reverse polarity). Then I switched my AC panel main to ON but I only saw about 85-90 volts on the analog meter (mmm, maybe I can't eat afterall). Lastly I flipped the Microwave breaker to ON and heard a nice BEEP from the microwave (mmm, maybe I can eat). Popped in my frozen Mexican Bowl and hit 1 minute. The microwave ran for about 10 seconds and then stopped. Oh crap, its cold, I'm hungry and I can't eat. I waited a minute, hit 1 minute again on the MW - it ran for about 30 seconds then stopped.

Time to get out the phone and take pictures of the panel (not very filling but practical). I waited a minute or so again and hit 1 minute, this time the MW ran the full 1 min. While the MW was running the AC panel monitor showed 110V and the Inverter remote panel showed the DC Input Voltage drop to near zero (see picture) and the Inverter Output Current was at 50%. Are these readings to be expected? How does cold affect or not affect the Inverter operation? Is the Inverter on its last legs? What are nominal Inverter readings and what are optimal readings for the Inverter during operation?

I ran the MW for 1 minute 3 more times with success and sure enough, I had a hot meal on a cold day. The Victron battery monitor showed a total of 5 amps consumed during this affair.

My TruePower Installation and Operation manual leaves a lot to be desired with no indication at all what the two meter readings mean or what indicates desired and undesired readings. Hence, this query to my fellow Tugnuts.

Any edification on the operation of the Inverter, or more so how to interpret the panel indicators would be greatly appreciated.

GF

Inverter ON, Microwave OFF at 40 degrees F: https://photos.app.goo.gl/2EeTSjhDh9PxDfPf8

Inverter ON Microwave ON at 40 degrees F: https://photos.app.goo.gl/CkMNdm1raSCvk4FP7

 

[Red Raven]

I have nearly the same equipment on our R27 Classic except our battery monitor is a Xantrex Link Lite. Here is my interpretation of your results.

True Power input reading on remote with microwave off: I haven’t paid much attention to this gauge but it appears the green range is approximately 11.5V to 14V. Mid range is near full charge, perhaps 12.7V meaning you should have near full charge (but does not mean your batteries are healthy). Your Victron should have a button to read Battery voltage instead of SOC. SOC is the least accurate reading in these monitors! Next time, check the battery voltage prior to turning on the inverter. It should be 12.6 or higher if the battery is charged.

120VAC meter with inverter on and microwave off: 85 to 90V is normal with no load. Once you have a load it jumps to something near 120V. This is normal.

True Power Battery input reading on remote with microwave on: The microwave draws “up to” 10A at 120 VAC which is 100A from your battery at 12V! This will significantly drop the battery voltage during the current draw potentially as much as a volt or so. A red LED on the battery input voltage is not totally surprising given the temperature. Cold temps will reduce the amount of current that can be pulled from the battery and result in a lower battery voltage.

I recommend you record the battery voltage shown on your Victron during each of these steps. I would not trust the SOC reading alone. If the battery voltage is above 12.7 volts prior to turning on the microwave you likely are near 100% SOC and the red LED on the inverter remote is likely a voltage below 11.5 due to cold and the high current draw. If you are seeing lower voltages than this or get similar results at warmer temperatures you should probably load test your batteries.

BTW. The current consumed over time would be in AmpHours or AH and not Amps. Amps is instantaneous current draw. AmpHours is Amps times Hours. 5AH would be equivalent to 100Amps for .028 hours or 1.7 minutes which is about the microwave “on” time you indicated.

I would suspect your results are all normal except for the microwave shutting down early. Are you sure it did not run the full time programmed? That microwave cannot heat a plate of food in one minute! If it really shut down then perhaps your batteries are a bit compromised. Do a load test. In any case this is not likely an inverter issue but rather a battery issue.

One more thing. Make sure that only the microwave is on and no other breaker when you are on inverter. Otherwise you may be overloading the inverter.

I hope this helps!

Curt

 

[GaylesFaerie]

Thanks for the reply Curt. I only mentioned the ProNautic Battery Charger to indicate I don't have a combination Inverter/Charger. I took all my battery readings off the Victron which showed 12.85V when I got on board. There are no other loads on the hard, all service switches are off (Engine & House which includes Thruster) and all 24 hour fuses are pulled and all battery cells topped off with distilled water (but I don't have a specific gravity reading yet). The Victron did show 11.4V while the Microwave was ON which didn't seem abnormal.

Good to know about the 120VAC reading 85-90 without load, that's new to me and I hadn't noticed that during my maiden usage this fall.

Your Ah calculations makes sense. I just looked up the wattage on the MW which is 1050W which is almost on the button for 10A at 120VAC. Also I mis-remembered the Victron Consumed Energy (CE) display, it was 5.7 *Ah* not amps.

Back to interpreting the displays; I'm still confused by the 2 percentage scales. With the MW OFF, the DC Input Voltage was at 50%. 50% of what, has got me confused. With the OFF off the Inverter output current makes sense at zero since there is no load on it yet.

With the MW ON, lets say the DC Input Voltage is 10%. Again, 10% of what? Does that mean its just really really close to the minimum voltage the Inverter needs to work (whatever that number is)? Similar guess on the Inverter Output Current, does the 50% reading mean I'm pulling about 50% of what the Inverter is capable of before an overload? That would be very useful to know if true.

Positive on the shut down times. I actually timed it the second time because the first shut down was so quick. And yes, 1 minute will never get my frozen Mexican Bowl hot, but I have this habit that annoys my wife to no end of heating frozen items over multiple cycles to let the heat spread a bit more evenly and eliminate cold spots. Down on the boat in the middle of winter she is nowhere to be seen (or annoyed). #;-)

GF

 

[Red Raven]

GF,

Sorry about the incorrect use of The ProNautic name. I meant the TruePower Inverter Remote. I have corrected it in the post above so not to confuse others in the future.

As far as I can tell the little bar graph range for the battery input meter is what I would call the “Usable Range”. In other words it is the range under which the Inverter can effectively operate. This range appears to be (empirically) about 11.5V to 14 V. Kind of like an SOC meter with a higher top end range. Below 11.5 volts the bottom most red LED will light. In this range the inverter cannot produce the 120VAC without an overload situation. I believe this is why your inverter is shutting off. Your photo shows the red LED lit and your Victron was indicating 11.4v. When under charge the batteries can read as high as 14V so that becomes the upper limit for the meter. Somewhere in the middle is normal for a fully charged battery not under charge with little or no load.

I suspect the 50% on the output current does mean 50% of max inverter current output. However, the 100% output capability depends on input voltage being sufficient. With 11.4 volts on the input the inverter limited on what output voltage and current it can produce. The limitation here is the batteries in terms of voltage and current available. The more current the inverter tries to draw the lower the battery voltage becomes until the inverter trips its safeties.

Next time you try it watch the inverter meter to see what it does when the microwave shuts off. It would be interesting to see if the overload LED turns on. Running the microwave from the inverter taxes the inverter and batteries to their max capability. Any weakness in the battery is going to cause the system to trip. In your case, this could just be the cold temperature or it could be the batteries are degraded. 11.4 volts at 40F with that load is not that unreasonable but appears to be just enough to trip the inverter. I recommend load testing the batteries and/or confirming you can get microwave operation at warmer temperatures to meet your needs.

Curt

 

[HRowland]

Hi Gary,
The Victron battery monitor is measuring voltage at the batteries. There is a fairly long 2G cable feeding power/ground to the inverter, the batteries are on the opposite side of the boat, the round trip cable length is likely in the 20-25 foot range. When running the microwave the current from the batteries is probably 100A or so, this will result in 1/2 to 3/4 volt drop through the cabling. If you saw 11.4 V at the battery then the inverter is seeing less than 11V which is low. Cold batteries do not help, they have increased internal resistance. If your batteries are the same ones installed before I sold your boat to the previous owner, then they are now 3 years old. I never got more than 3 years use from the house bank in the past. These batteries are Ultrapower EV27TM, 110AH flooded deep cycle group 27. Ultrapower is a house brand for North East Batteries, they are manufactured by Exide. You may be due for a new set of house batteries. The low voltage may have caused the inverter to drop off and shut down your microwave.
Howard

 

[GaylesFaerie]

Thanks everyone, that helps me get a better handle on things. Howard, the Ultrapower batteries are still in the boat and until this cold whether issue have been working fine and giving good readings as far as I can tell. Also, can I replace the house bank independent of the Engine? Or all 4 at once? BTW, curious when exactly you sold the boat.

WRT to the batteries health, I'll measure the specific gravity in all the cells once the weather warms up a bit, another learning exercise at the least. I recently bought a HydroVolt temperature compensating meter for that. As a first time motor boater I've not dealt with a bank of batteries before. Are there any obvious signs that they are on their last legs? I thought a voltage reading after 24 hours of no charge/no use below 12.7 would be an indicator. Can I not trust the Victron for that or is it more complicated... wait - we are dealing with electricity here, so I'm sure it is but eager to learn.

GF

 

[Red Raven]

Your batteries (or the connections to the inverter) may have higher than normal impedance/resistance. My first set of batteries measured 12.7 or higher when not under load. Under even moderate load (e.g., flushing the toilet) they would drop as low as 10.5 volts! Even if the specific gravity measurement tells you they are fully charged you still could have an internal impedance problem resulting in low voltage under load. In addition to the specific gravity measurement, check and clean all the connections from the batteries to the inverter and do a load test of the batteries.

Curt

 

[knotflying]

Thanks everyone, that helps me get a better handle on things. Howard, the Ultrapower batteries are still in the boat and until this cold whether issue have been working fine and giving good readings as far as I can tell. Also, can I replace the house bank independent of the Engine? Or all 4 at once? BTW, curious when exactly you sold the boat.

WRT to the batteries health, I'll measure the specific gravity in all the cells once the weather warms up a bit, another learning exercise at the least. I recently bought a HydroVolt temperature compensating meter for that. As a first time motor boater I've not dealt with a bank of batteries before. Are there any obvious signs that they are on their last legs? I thought a voltage reading after 24 hours of no charge/no use below 12.7 would be an indicator. Can I not trust the Victron for that or is it more complicated... wait - we are dealing with electricity here, so I'm sure it is but eager to learn.

GF

You can buy a load tester or remove them and have them tested at one of the auto stores. Make sure they have rested at least 30 minutes before doing a load test. My usual mode of operandi is to replace the flooded every three years regardless of state. For about $90.00 each you can get group 27 at Walmart. Many people like the AGM especially if battery replacement is difficult. They have come down in price, but with a couple of owner operator mistakes they can be killed also and at a higher price tag to replace. Keeping things simple is always better when boating. 😀