Another inverter & a separate gen circuit

When we first bought our boat, I bought and installed an inverter to be able to operate the usual AC stuff while underway, since we don't have a generator. I, and my dubious wisdom, decided to save a few $$ and bought a 3500W off of ebay. It was advertised as a sinewave inverter and I paid in the neighborhood of $350 for it, remote included. Why in the hell I thought we would need 3500 watts since I never planned on having more than a 400ah house bank is beyond me. Why in the hell I believed it would actually be a sinewave as advertised was also another lapse in my judgement. It works fine but when we run our digital microwave on it, I don't need an oscilloscope to know that it's outputting current that's just as square as sponge bob's pants.
This new Samlex is only 1500 watts but it's all that we need and it's way quieter. I boiled a cup of water in the microwave to test it and the microwave performed just as it does on shore power...smooth and quiet.
The good thing is the wiring was already there so it was a relatively painless swap.
The other thing I did was add a 15A shore power receptacle that is designated for the portable generator we have. Our 30A shore power goes through a transformer and that was just one more thing to load the generator and rob wattage that could be used elsewhere. I am very hopeful that we'll be able to run the reverse cycle heat/AC with the generator after I add a start capacitor to the AC. I have it but haven't gotten around to installing it, since I need to remove the refrigerator to get access to the unit. I did try the AC on the gen while it was going through the transformer and it was definitely a no-go. Hopefully bypassing the transformer and adding a capacitor will allow it to start. It only takes a few amps to run ,once it's going.

The old faithful square wave inverter.

The new Samlex 1500 sinewave inverter, the inverter remote on/off switch & the Blue Seas remote control battery switch to power the inverter and the AC source selector switch to select shore power through a transformer or the portable generator ,bypassing the transformer. Also, a picture of the generator connection receptacle in the cockpit.

I installed a Victron Phoenix 1200VA unit that I leave on 24/7 to run the fridge and other appliances, it will run my microwave just fine and charges the laptop. Very happy with the unit and it's it the same price range as the Samlex you are using. It draws 1.5 amps while idle, so the idle current is very low.

What is the idle current of the Samlex?

sbman said:

I installed a Victron Phoenix 1200VA unit that I leave on 24/7 to run the fridge and other appliances, it will run my microwave just fine and charges the laptop. Very happy with the unit and it's it the same price range as the Samlex you are using. It draws 1.5 amps while idle, so the idle current is very low.

What is the idle current of the Samlex?

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The manual says idle current draw is less than .9 of an amp but I haven't checked what the actual battery SOC meter shows in the real world. I did plug in the crock pot, since we plan on using that while heading South next month. On low power it's drawing 10-11 amps of DC and on high, around 17. I'm quite happy with those readings since the stock alternator will be able to keep up while running. The microwave is a power hog @ 110A on high power.

On the rare occasions we watch TV, we have a separate 300w portable inverter that I plug into a 12v socket. I bought that when we were using the square wave inverter and will probably continue to use it for the TV but I don't doubt the Samlex wouldn't be just as efficient as the smaller one.

When buying an inverter one must be very careful. There is an amazing amount of misleading marketing. I have seen some vendors market as True Sinewave XX 40. Then when I read deeper I discover that True Sinewave is a brand name and has nothing to do with the sinewave. Buried in the manual I discovered it was your standard modified sinewave. Don't be fooled by names like True or Pure. Read the details.

I also remember a company whose product line was called Lifetime. If you bothered to read the manual you discovered it had a 90 day warranty.

Is your air conditioner compressor a rotary style?, if so, it will probably start just fine without upgrading the capacitor to a soft start.

You're better off with a Honda 2K generator on the swim platform. Using the batteries to make coffee, run the microwave, outlets, AC, etc still requires that you recharge the batteries. Plus it requires a much larger battery bank.

I use a 2K puresine invertor to run my TV, Apple TV and Hotspot. That is so I can watch TV late at night without needing to run the generator.

Gdavid said:

Is your air conditioner compressor a rotary style?, if so, it will probably start just fine without upgrading the capacitor to a soft start.

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It is but it killed the generator while trying to start. That's why I ran a separate generator circuit so as to bypass the transformer. Maybe it will now have enough umph to start it without the additional capacitor but if not , I'll install the cap and hope for the best

Shrew said:

You're better off with a Honda 2K generator on the swim platform. Using the batteries to make coffee, run the microwave, outlets, AC, etc still requires that you recharge the batteries. Plus it requires a much larger battery bank.

I use a 2K puresine invertor to run my TV, Apple TV and Hotspot. That is so I can watch TV late at night without needing to run the generator.

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I think that's why I bought a 3500w inverter in the first place...I had a vision of running a small AC for the stateroom only for maybe a few hours but I quickly realized that even a small AC unit on an inverter would require more battery capacity than I was willing to install. We bought a Wen 2000 (or 2200?) watt inverter generator that we do run on the swim platform to charge the batteries through the onboard charger and heat water with the AC current side of the water heater and we're happy with it. It sure would be nice if we could use it for intermittent heating and cooling though.

boomerang said:

I think that's why I bought a 3500w inverter in the first place...I had a vision of running a small AC for the stateroom only for maybe a few hours but I quickly realized that even a small AC unit on an inverter would require more battery capacity than I was willing to install. We bought a Wen 2000 (or 2200?) watt inverter generator that we do run on the swim platform to charge the batteries through the onboard charger and heat water with the AC current side of the water heater and we're happy with it. It sure would be nice if we could use it for intermittent heating and cooling though.

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Interesting, a friend is running a small AC on a Honda 2kw inverter gen, i don't think he had a soft start but I will have to ask him.

Edit: he just got back to me and he does, it is a 16kbtu cruisair and he did install a soft start.

Another data point: my new honda 2.2k starts my Dometic 12k BTU with no soft start mods.

My friend is running a 16kbtu dometic with this capacitor:

https://www.amazon.com/dp/B08H72RSD8?ref=ppx_pop_mob_ap_share

There is more to a system than just the plain numbers. A deep-cycle wet battery such as 6v Trojan golf carts are designed for longevity but when a hi-amp draw hits them, voltage can drop dramatically and cause a low-voltage cutout on an inverter. What's hi-amp? Depends on size of battery bank. I can tell you from recent experience on my van that running a 700W electric teakettle off a 220AH battery bank (two 6v GC batteries) immediately took the battery voltage from 12.8v down to 12.0v (it recovered to 12.7v a few minutes after the load was removed). If I had four GC batteries, voltage drop would be minimal, but point being is for FLA batteries, there is a significant drop across the posts under relatively hi-amp draws.

When replaced with two 100AH LIFePO4 batteries, there was virtually no voltage drop. I am able to run a small, 5000 Btu window AC for a couple hours on the LiFePO4 bank.

One last observation. In my van, I have some space constraints so could only fit a 1500w PSW inverter. I wish I could have fit a 2000W. The start-up surge on my small Dewalt table saw trips the 1500w over-current of the inverter. If I'm fast enough to reset the inverter while the saw blade is still spinning, I can avoid the hi-surge of start-up and get the saw running, but I would definitely recommend a 2000W PSW at a minimum.

Peter

mvweebles said:

There is more to a system than just the plain numbers. A deep-cycle wet battery such as 6v Trojan golf carts are designed for longevity but when a hi-amp draw hits them, voltage can drop dramatically and cause a low-voltage cutout on an inverter. What's hi-amp? Depends on size of battery bank. I can tell you from recent experience on my van that running a 700W electric teakettle off a 220AH battery bank (two 6v GC batteries) immediately took the battery voltage from 12.8v down to 12.0v (it recovered to 12.7v a few minutes after the load was removed). If I had four GC batteries, voltage drop would be minimal, but point being is for FLA batteries, there is a significant drop across the posts under relatively hi-amp draws.
...

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I have 6 GC-2 on my system right now, and 2 more are to be added soon for a total of 8. The 6 handle 100+ amp loads with little voltage drop, as I cook with an induction stove or run the microwave at 1200 watts.

sbman said:

I have 6 GC-2 on my system right now, and 2 more are to be added soon for a total of 8. The 6 handle 100+ amp loads with little voltage drop, as I cook with an induction stove or run the microwave at 1200 watts.

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We have eight GC15 batteries (932ah). We have run our microwave, toaster, coffemaker, and, before we installed a permanent induction cooktop on a dedicated, non-inverter circuit, a portable induction cooktop, not all at the same time, of course. The batteries don't seem worse for the wear but, so what if they last six or seven years, rather than seven or eight.

I just went through the inverter purchase maze. One has to look closely at the website specifications as the "sine wave," "true sine wave," and "pure sine wave" descriptions may or may not be what will work. I was originally sent a "sine wave" inverter that didn't work for an induction stove top. For an additional $20, the OP could have bought a 3,500W pure sine wave inverter by the same manufacturer. I finally purchased this exact model and have no problems (unless its ability to produce more power than I need is a problem). I do have momentary substantial voltage drop if I load it up (520Ah flooded lead deep cycle), but they recover to about .2V less when the inverter turns off, depending on how long I've run a heavy load. Best I can tell the batteries are 4 years old. Time will tell (maybe) as to whether I'm killing my batteries.

Marco Flamingo said:

I just went through the inverter purchase maze. One has to look closely at the website specifications as the "sine wave," "true sine wave," and "pure sine wave" descriptions may or may not be what will work. I was originally sent a "sine wave" inverter that didn't work for an induction stove top. For an additional $20, the OP could have bought a 3,500W pure sine wave inverter by the same manufacturer. I finally purchased this exact model and have no problems (unless its ability to produce more power than I need is a problem). I do have momentary substantial voltage drop if I load it up (520Ah flooded lead deep cycle), but they recover to about .2V less when the inverter turns off, depending on how long I've run a heavy load. Best I can tell the batteries are 4 years old. Time will tell (maybe) as to whether I'm killing my batteries.

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That is the exact one as I ordered and it was advertised as a pure sine wave inverter. If you look at the pictures, I can't see anywhere on the actual unit that states it's a non-modified sinewave inverter. Does yours say sinewave on the case?
Also, just to be clear, I'm NOT attempting to run the AC off of the inverter. We have a 2000w inverter generator. That's what I'm hoping to be able to run the air conditioning/heating unit on.

diver dave said:

Another data point: my new honda 2.2k starts my Dometic 12k BTU with no soft start mods.

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Interesting. All of the research I've did (it was actually all from this forum )
before buying the generator indicated that folks had good luck with a portable generator running an AC unit. Some said they had to use an aftermarket capacitor to help the compressor over the starting hump so that's why I ordered one, just to be sure. I don't recall anyone saying they ran their generator through the ships service that included a transformer in the line. That's why I'm hoping bypassing the transformer will allow our AC to start using the generator. I'm hoping the 200 watt difference between yours and ours isn't the straw that broke the camels back.
FYI our's ,I think, is a 10k btu unit and maybe the compressor is smaller than your 12k. I'll take the genny don to the boat maybe this evening and maybe that lemon will be squeezed!

Marco Flamingo said:

I just went through the inverter purchase maze. One has to look closely at the website specifications as the "sine wave," "true sine wave," and "pure sine wave" descriptions may or may not be what will work. I was originally sent a "sine wave" inverter that didn't work for an induction stove top. For an additional $20, the OP could have bought a 3,500W pure sine wave inverter by the same manufacturer. I finally purchased this exact model and have no problems (unless its ability to produce more power than I need is a problem). I do have momentary substantial voltage drop if I load it up (520Ah flooded lead deep cycle), but they recover to about .2V less when the inverter turns off, depending on how long I've run a heavy load. Best I can tell the batteries are 4 years old. Time will tell (maybe) as to whether I'm killing my batteries.

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Once you get over about 1200-1500 watts continuous, a 12V system really becomes a challenge due to the high currents required. To max out a 3500 watt inverter at 12V requires 300 amps continuous which is a wiring challenge with dual 2/0 cables required even at short lengths.

Another issue that is often overlooked with cheaper inverters beyond the sine/modified sine issue is the idle current.

I currently have two inverters onboard. A Victron Phoenix 1200VA (~ 1200W) which I leave on all the time (my boat is completely off grid), the fridge is plugged into it, I charge my laptop from it and use it to run small fans occasionally. It draws 1.5 amps idle, about 18watts, 432Whrs idle consumption in 24 hours, 36 amps drawn from the house bank over 24 hours to support it.

The Victron 1200VA Phoenix unit, for the price is a very high quality unit that would be ideal for most peoples needs and would be a better selection in most cases than an equivalently priced 'cheap' 2500-3500W unit. Unless you are wiring up your 2500W+ unit with the proper wiring and have sufficient battery to support the draw when using it at high power levels, the extra capacity, high idle current and cheap construction is all a downside over having a high quality, efficient unit with a lower rating.

My other inverter is a (cheapish) AimsCorp 2500W Pure Sine inverter/charger. It draws 6 amps idle, 72 watts, and it would use 1.4kW in a 24 hour period just to be turned on. I turn it on only when I need to run a large appliance and it powers the microwave, induction cooktop and any power tool I throw at it just fine but the high idle current is a big downside.
At some point I'll upgrade it with a high quality unit with a much lower idle current and won't need two inverters at all. I'll also rewire for a 24V or possibly a 48V house bank at that time as well.

Unfortunately the idle current does go up with inverter size even in the best designs, but all the quality units I've looked at beat the one I have now by at least 4X better.

Shawn,

I don't remember if it actually states "pure sine wave" on the inverter, but I know that it comes in two versions. I also know from reading lots of websites that there is a new and older version of the 3,500W (which IIRC looked to be mainly the number of outlets and the direct AC connection capability). The reviews for the "newer" version were much better, so I got mine from Amazon based on the picture in the advertisement (not always accurate). Like I said, it was a maze. I'll look to see if it states "pure sine wave" next time I'm at the boat. The modified sine wave made the induction stove top howl and used more amps. It was a nonstarter.

I also did not connect my inverter AC output to the house. I already have a Xantrex inverter/charger for that (modified sine). Good enough for most loads, but the induction stove top requires a clean wave. My installation allowed for the inverter remote right next to the stove, which is also where the battery monitor is located (right side of picture). Easy to keep an eye on the usage when cooking. An inverter circuit breaker (left of battery 1-2-Both switch) allows me to turn off everything to the inverter to eliminate the standby amps for the inverter/stove top (about 1.5A).

My pure sine wave inverter is mounted directly underneath in the floor cabinet and has additional info on its screen regarding the AC output and voltage at the inverter. Need to get on my knees to read it, so usually don't.

Shawn,

Does your boat still have the plumbing, fuel and electrical infrastructure of the original generator? Mine still runs fine, and is actually not as noisy as they are notorious for but eventually I'll swap it out for a 3 cylinder 8kw that is in my garage. I'd like to see it go to a good home.

Gdavid said:

Interesting, a friend is running a small AC on a Honda 2kw inverter gen, i don't think he had a soft start but I will have to ask him.

Edit: he just got back to me and he does, it is a 16kbtu cruisair and he did install a soft start.

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I'd also expect a inverter type Aircon to be much more suited to genset or inverter power. They have much less inrush of current on start up. It is typically this inrush that stalls or even damages non-mains power supplies. They also have the advantage of running at reduced power when temperatures stabilise vs cycling on and off at full power.

Success! Well, moderate success.

So I came home and took the generator to the boat to see if it would power the 10k air conditioning/heating unit. The older Dometic I'm sure draws more than a new, state-of-the art one but it begrudgingly comes to life and operates like it's supposed to operate, without the isolation transformer in the circuit. I think putting a start boost capacitor on the AC will solve the heavy initial load on the poor generator.
Notice I'm not calling the cap I bought a soft-start. It's a $12 capacitor marketed for just such cases as ours. I found out about it from another member on here ,HopCar, who I will be sure to thank if it makes the difference, which I feel it will, since it's right on the threshold of go/no go. I wasn't good with paying $429 for the soft start, at least until I tried this one first.
I also only paid $400, delivered ,for the 2k gen from Amazon. Again, maybe the 2200w Honda would've done the trick but this one got good reviews and was a third the cost of a Honda.
I'll post the final results when I get around to installing the magic capacitor. There's just so many other important loose ends to tie up before we head South in just over a month that I might wait a bit on tackling this one.

I'd like to know why batteries get 'drained' when inverter is on, but not in use.????

Jiggernaught said:

I'd like to know why batteries get 'drained' when inverter is on, but not in use.????

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High waste heat = poor design.
My Magnum doesnt have this issue. I measured it recently with my BMS; dont recall the exact reading, but it convinced me to leave it on when the boat was occupied.
(Lots of folks charging things)

Jiggernaught said:

I'd like to know why batteries get 'drained' when inverter is on, but not in use.????

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When an inverter is turned on, you have circuitry running to boost voltage from 12V to 120V and convert it to AC. To do this requires power even if nothing is plugged into it. Similar to a gas generator idling, it is using fuel even if you have nothing plugged into it, less than when there's a load on it, but not zero fuel usage.

Better quality units have better quality components, better circuit designs, better firmware and engineers that spent time making sure the idle current is as low as possible, cheap units have none of that.

Thanks for clarifying. I wasn't aware that much juice could be consumed, in my case draining two 850 amp batteries and two 1300 amp 4D's , inside of a week.
The unit I have is 2000 watt (without naming brand) and cost about $1800 to replace. I wouldn't consider that 'cheap' but I realize cost doesn't always relate to quality.

Jiggernaught said:

Thanks for clarifying. I wasn't aware that much juice could be consumed, in my case draining two 850 amp batteries and two 1300 amp 4D's , inside of a week.
The unit I have is 2000 watt (without naming brand) and cost about $1800 to replace. I wouldn't consider that 'cheap' but I realize cost doesn't always relate to quality.

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I think you are confusing 'cranking amps' with amp hour rating. 4D's are typically about 200 Ah each, whatever your smaller ones are, are more likely 100aH each, so 600 Ah total. If your inverter is using 2 amps per hour idling (not much), in 300 hours it will have drained them dead, only 12 days, if it's using 3 amps, 8 days. If your batteries are older or not in top condition they will hold less than their rating and it will drain even faster.

Even a good quality unit will draw a couple of amps at idle. A steady, slow drain doesn't take long to eat up your batteries.