Samlex Inverter Power Draw Question

[EMD360]

I just finished a Samlex pure sine wave PST 3000-12 inverter install. I ran 00/2 cables because that was recommended in the user manual. I added a Renogy 30 amp transfer switch with the charger wired to the shore power connections so the charger stays off when shore power is off. It is practically next to the battery compartment under the dinette seat.

I also installed the remote at the entry wall so I can see the readings without bending over like with reading the Victron meter (when not using Bluetooth) or the surge protector which I ordered without the remote by accident.


So my first test was to run the microwave for 1 minute. I was kind of shocked to see the time remaining plunge from 9 hrs to 27 min in power left after only 1 minute.
The 14.6 capable batteries were not fully charged reading 13.37 volts at start. Not sure why they were at that level as they are on shore power so the progressive dynamics 9160L should have them a bit higher.
The voltage dropped to 12.87 in a minute. The Victron reads 98% charge but only 27 min remaining power. Maybe there is something wrong with my meter settings.
Start:

End after 1 minute of microwave power used:


Does this amount of power draw seem about right for this inverter?

[pianotuna]

EMD360,

If I were going to upgrade at my home, I'd jump right to 50 amp.

To do solar an energy audit is a good way to start. Find one in this series of articles:

https://freecampsites.net/adding-solar/

[EMD360]

A combination inverter charger converter may have been a better choice. It took me awhile to figure out the three separate devices, the charger and DC to Dc were first decisions then I decided to add an inverter. I considered the Renogy but decided the appliance is most likely to run is the microwave. Late night warm milk helps me sleep. It’s hard to tell what surge this inverter could take for 5 min. Kind of a problem with the specs. I saw several combination devices but I had just upgraded the others. We were camping this week but on 30 amp electric and everything works even at the same time! I may have to upgrade to a 30 amp outlet at home. I used the inverter in the boat launch parking lot to inflate our Intex boat. Nice to have it onboard. Next is solar right?

[3_tons]

BTW upon re-read, 6000 watts is ample surge wattage, but 8ms is equivalent to about only 1/2 of a half of a full sinewave cycle (i.e. 1/4 of a full cycle), meaning that the surge rating is relatively meager, which is a reflection of the inverters inner-workings…Per my previous (bargain inverters…) recall that ‘advertised wattage ratings’ is only part of the story, and when it comes to ‘heavily reactive’ loads (e.g. compressors and microwaves), surge ratings and duration matters most because these loads tend to ‘push back’ against the power source (your Samlex)…I would also consider running a second set of cables (in parallel) to your existing 02’s to help minimize voltage sag (say, under heavy loading), and for possible future use - FWIW, to my ProSine 2.0 I’m running 0004 AWG cabling, 6’ roundtrip… JMO…

For example the ProSine 2.0 (2000w) has a surge rating of 4500w and a duration for 5 seconds (does run my 11kbtu air cond without a hitch…), while even 20 seconds in not uncommon on say a heavy, old school copper-transformer based ‘Low frequency’ inverter…

Just a heads up: Considering your desired usage, for your next inverter you might keep in mind a true load sharing type, combination inverter-charger…Personally (in this regard…), my next ‘someday’ inverter will likely be a Victron multiplus hybrid (true load sharing type) inverter-charger…

3 tons

[pianotuna]

EMD360 wrote:

I am disappointed that the charger draws so much more power that the old WFCO did.

Micro ran ok on inverter just not on shore power 20 amps.

Charger on shore power and the rest on inverter is a very interesting idea! The charger plug is in a difficult position but I might try this. Thanks.

The WFCO didn't really work. That's why it didn't draw much power.

Great news on the microwave. It may work on shore power, with the converter turned off.

This is called double conversion. I often only had a 15 amp circuit, with no access to the shore power breaker, so I'd routinely run just the converter. The rest of the loads were carried on a 2500 watt Cobra MSW inverter rated to run motors. If you are going to do this, it may be a good idea to carry replacement fuses for the converter. DAMHIK

I did have a large battery bank of 875 amp-hours.

[EMD360]

Probably right on power sucking! But it’s so convenient to reheat our coffee and cook hot dogs for the grandkids. About all they will eat besides chicken nuggets.
I am disappointed that the charger draws so much more power that the old WFCO did. Especially when it’s hot. It’s a 60 amp instead of a 55. Micro ran ok on inverter just not on shore power 20 amps.
Charger on shore power and the rest on inverter is a very interesting idea! The charger plug is in a difficult position but I might try this. Thanks.

[3_tons]

Yours is not a surge problem - inverter and generator output decreases with higher ambient temps, while Air cond begins to present an even larger load… Attempting to run a microwave (or air cond) and charger at the same time overwhelms the 20a circuit…A hybrid type (load sharing) inverter may make the difference…Another tip, get rid of power sucking stick house microwave or consider a stay at Embassy Suites…

3 tons

[time2roll]

EMD360 wrote:
Yesterday at above 95 degrees while we were at a day park the generator would not start. I used the inverter instead just long enough to run the air compressor for tubing. Today, another hot one at about 95°, I tried running the microwave while plugged into our outdoor extension cord on a 20 amp circuit. It blew the circuit. The PD charger was running hot with the fan on constantly. So I unplugged it and ran the microwave and again the time remaining dropped fast to 23 minutes and 13.3 volts. It appeared to bounce back to 25 min just running the fridge and any additional loads. I was surprised the micro circuit was tripping with the charger running in the heat.
The Samlex peaks at 6000 amps for 8ms.
I’m not going to try to run the air from the inverter. I am waiting for morning when it’s cooler to see if there is a problem with the generator. We will have electric hookups this week so won’t need either the inverter or the generator until next week.

I would try to run the converter to keep the battery charged by using the extension cord.
Then run what you need off the inverter. Both at the same time if the set up allows it.

[EMD360]

Yesterday at above 95 degrees while we were at a day park the generator would not start. I used the inverter instead just long enough to run the air compressor for tubing. Today, another hot one at about 95°, I tried running the microwave while plugged into our outdoor extension cord on a 20 amp circuit. It blew the circuit. The PD charger was running hot with the fan on constantly. So I unplugged it and ran the microwave and again the time remaining dropped fast to 23 minutes and 13.3 volts. It appeared to bounce back to 25 min just running the fridge and any additional loads. I was surprised the micro circuit was tripping with the charger running in the heat.
The Samlex peaks at 6000 amps for 8ms.
I’m not going to try to run the air from the inverter. I am waiting for morning when it’s cooler to see if there is a problem with the generator. We will have electric hookups this week so won’t need either the inverter or the generator until next week.

[pianotuna]

EMD360 wrote:
So it does not damage the AC compressor to have the inverter just shut down without turning the AC off first? I’m always leery of running the air on just an extension cord even with a 20 amp fuse.

If it shuts down--best to wait about 3 minutes before restarting.

What matters is voltage drop. If it drops below 107, I get out my autoformer to fix the problem.

Running on low voltage causes cumulative damage to the air conditioner.

[3_tons]

EMD360 wrote:
So it does not damage the AC compressor to have the inverter just shut down without turning the AC off first? I’m always leery of running the air on just an extension cord even with a 20 amp fuse.

The air cond compression is mostly a ‘power off or on affair’, with ‘power on’ being the most difficult LRA load for your inverter to resolve (called Locked Rotor Amps), A soft-start device (in lieu of the OEM start capacitor) has often been reported to help manage this extreme high compressor starting load, making life easier on inverters and generators…

To your question about a low voltage inverter shutdown, I would be more concerned about operating while in a continuous low voltage condition which could result in increased current to the motor windings…Improper battery cable AWG gauge and excessive round-trip cable length can also result in a low voltage bottleneck…Some inverters even have double terminals so one can double up on their cabling to reduce voltage drop (smaller gauge cables in parallel can be easier to manage).

Also, know that there are lots of bargain priced inverters on the market, and not all inverters of the same ‘advertised wattage’ rating can handle these extreme LRA load (inductive loads) in the same way, because of differences in electronics. This aspect should not be overlooked…Motor start-up load amperage can momentarily be 4-6 times that of normal running amps, spec’s that should reflected in your inverter’s published surge rating and duration…

3 tons

[EMD360]

Both the inverter and the BMS have an auto shutoff at 10v. Can’t change either one. The inverter is +- .01v. I believe it set the Victron at 10.4v for depletion. Have not set up an alarm yet though.

[EMD360]

So it does not damage the AC compressor to have the inverter just shut down without turning the AC off first? I’m always leery of running the air on just an extension cord even with a 20 amp fuse.

[3_tons]

Itenerate1, from actual operating experience, I fully agree with your assessment…I routinely run my air cond (concurrent with 440w solar) from a single 200a/h LFP…In fact, I was on hand when my neighbor’s lone 100a/h LFP continued to operate his 11kbtu Coleman Mach 1 PS, though (via oversight - ugg! ) the battery had inadvertently gotten down to a mere 06% SOC before discovery!!

I believe that this characteristic (though commonplace with portable tools) is often difficult for FLA converts to fully grasp (the age old ‘rejection before eventual acceptance’ thingy…), and also points to how relatively unimportant the need often is to fully charge a LFP to 100% SOC…Another benefit is the higher receptivity rate (many have attested to…) common with LFP, a significant attribute when harvesting..

3 tons

[Itinerant1]

You're using LFP so the SOC or "I’m curious if the fully charged battery can take more inverter load" doesn't really have an effect the way I think you're thinking that lead does, but when the lvd (low voltage disconnect) is reached it will shut itself down.

As an example the other day I turned the A/C on when the the SOC was 60% and ran it till 35% (near 2 hours) so it was inverting at 140a +/- for a couple hours, the inverter was showing 12.2v before I shut it off. If I kept it going the inverter would of shutdown at 12.0v probably in another hour or so.

Edit.. the inverter will shutdown before the batteries have reached the lvd (vpc). The charge/ discharges source should be setup to disconnect before the battery bms does the shutting down.