The C-Brats Forum Index
HomeForumsMy TopicsCalendarEvent SignupsMemberlistOur C-DorysThe Brat MapPhotos

Power inverter
Goto page 1, 2, 3  Next
 
Post new topic   Reply to topic    The C-Brats Forum Index -> Electrical and Wiring
View previous topic :: View next topic  
Author Message
TyBoo



Joined: 23 Oct 2003
Posts: 5056
City/Region: Warrenton
State or Province: OR
C-Dory Year: 1996
C-Dory Model: 25 Cruise Ship
Vessel Name: TyBoo
Photos: TyBoo
PostPosted: Tue Jan 21, 2020 9:34 pm    Post subject: Power inverter Reply with quote

I have a 1500 watt Cobra branded inverter onboard that I use mainly to run a Keurig coffee maker and a small microwave.

Today I tried to power a new induction cooktop and found that until a load is placed on the AC side of the inverter the output voltage just sitting there is about 70vac and the stove shuts down before it even gets started with a low voltage error. If I start the 900 watt microwave the output voltage at the inverter goes up to 106vac and then the stove will turn back on and they will both run. That, of course, overloads the inverter if I set the stove to a usable power level. It is also kind of dumb to have both things trying to run at the same time.

I don't really understand all I know about this stuff, so - here are my questions. Thanks in advance.

Is there something wrong with the inverter I have? The smaller inverter that powers the TV and a couple of video cameras always has 107-110 volts output when idle, so why doesn't the larger one? The input voltage to it is greater than 13vdc with either the motor running or the shorepower charger on to feed the batteries. There is a good deal of voltage drop when running the Keurig but the unit (almost) always stays above the 11.5vdc cutout point.

Speaking of voltage drop... When I installed the inverter I wanted it inside the cabin so I ran heavy lines from the batteries. The first try with AWG 2 wires didn't work so I ended up using 1/0 stranded copper battery cable for both legs from the batteries located port stern to the inverter located starboard amidship. That is a run of a little over 20'. I don't get any significant voltage drop with the 900 watt microwave but the 1400 watt Keurig pushes it.

I am using two marine cranking batteries (Group 24 I think, but maybe 27) and I don't recall the CCA rating but it is pretty good. I get them at Costco and replace them every few years because I pretty much abuse them. They are cabled in parallel and have been left that way for years. The kicker has its own battery that will start the main if I need to jump it so I don't worry about it. There is a 150 fuse at the battery just for the inverter supply.

If I replace the inverter I am thinking about putting it in the compartment with the batteries using short DC cables and a long AC supply line to the cabin. That should minimize the voltage drop on the DC side and safely feed the appliances inside that are used one at a time. The hatch where the batteries sit is a semi-dry compartment under the floor and there is room in it to put a small box of some sort to protect the inverter from all but humidity. I suppose it would have to be large enough and vented so the inverter fan will be able to supply cooling as needed. Can I reasonably expect the inverter to last very long out there under the floor? They aren't all that cheap, although I could get one for less than that battery cable in there now is worth.

Just a quick glance on Amazon turns up this 2000 watt inverter that is rated pretty good and accepts a remote switch so it can be turned on and off from inside the cabin. It is priced low enough that a complete fail on my part wouldn't hurt a whole lot.

This turned out to be a long winded post. I appreciate any advice or insights you can offer.

_________________
TyBoo Mike
1996 25' Cruise Ship
Back to top
View user's profile Send private message Send e-mail
SnowTexan



Joined: 08 Aug 2019
Posts: 63
City/Region: Carlton
State or Province: WA
C-Dory Year: 2006
C-Dory Model: 22 Cruiser
Vessel Name: Miss Maria
Photos: Miss Maria
PostPosted: Tue Jan 21, 2020 11:17 pm    Post subject: Reply with quote

Without seeing your wiring, I suspect your inverter is fine and you are using an inexpensive multimeter to take the reading? Is the inverter a modified sine ? Correction: you could be using an expensive multimeter that is not a true RMS meter, and not get an accurate reading on a modified sine inverter. My electrical background is from running a royal ton of DC cathodic protection Lines from AC sources, not residential or marine work. But I would check the meter and inverter type first. Or post here and I can look after Iíve slept and compare notes with my electrician buddy if nobody more knowledgeable than myself replies (though no doubt they will!)
Back to top
View user's profile Send private message
SnowTexan



Joined: 08 Aug 2019
Posts: 63
City/Region: Carlton
State or Province: WA
C-Dory Year: 2006
C-Dory Model: 22 Cruiser
Vessel Name: Miss Maria
Photos: Miss Maria
PostPosted: Tue Jan 21, 2020 11:29 pm    Post subject: Reply with quote

I hope this is the right link, and not the scene from point break that I sent to my buddy earlier ...

https://youtu.be/PHixK2d_uZU
Back to top
View user's profile Send private message
SnowTexan



Joined: 08 Aug 2019
Posts: 63
City/Region: Carlton
State or Province: WA
C-Dory Year: 2006
C-Dory Model: 22 Cruiser
Vessel Name: Miss Maria
Photos: Miss Maria
PostPosted: Tue Jan 21, 2020 11:32 pm    Post subject: Reply with quote

Sorry triple posting... what Iím asking is: is your inverter a modified sine inverter, and is your meter a true RMS meter? If yes to modified sine, is the new stove compatible?
Back to top
View user's profile Send private message
TyBoo



Joined: 23 Oct 2003
Posts: 5056
City/Region: Warrenton
State or Province: OR
C-Dory Year: 1996
C-Dory Model: 25 Cruise Ship
Vessel Name: TyBoo
Photos: TyBoo
PostPosted: Wed Jan 22, 2020 12:13 am    Post subject: Reply with quote

The meter is an older Fluke DMM. It is on the boat so I can't get the model number right now. That RMS stuff is a little beyond me so I cannot answer further.

The inverter is a Cobra CPI 1575 1500 Watt modified sine wave (now discontinued).

The output voltage reading on the meter changes from 70vac to 106vac when I switch on the microwave. At that point the induction stove will operate as it should.

The internet seems to be heavily on the side of saying the stove will work on MSW. Nevertheless, perhaps I should limit my replacement options to PSW inverters? Those are getting up there in cost and I would be hesitant to risk locating it back close to the batteries. Moving or substantially changing the battery arrangement is not a good option for me. The whole project is not worth that much effort.

Thanks! I have a cheap Klein DMM I can take down tomorrow and check the voltage again to compare with the Fluke.
Back to top
View user's profile Send private message Send e-mail
SnowTexan



Joined: 08 Aug 2019
Posts: 63
City/Region: Carlton
State or Province: WA
C-Dory Year: 2006
C-Dory Model: 22 Cruiser
Vessel Name: Miss Maria
Photos: Miss Maria
PostPosted: Wed Jan 22, 2020 12:53 am    Post subject: Reply with quote

TyBoo wrote:
The meter is an older Fluke DMM. It is on the boat so I can't get the model number right now. That RMS stuff is a little beyond me so I cannot answer further.

The inverter is a Cobra CPI 1575 1500 Watt modified sine wave (now discontinued).

The output voltage reading on the meter changes from 70vac to 106vac when I switch on the microwave. At that point the induction stove will operate as it should.

The internet seems to be heavily on the side of saying the stove will work on MSW. Nevertheless, perhaps I should limit my replacement options to PSW inverters? Those are getting up there in cost and I would be hesitant to risk locating it back close to the batteries. Moving or substantially changing the battery arrangement is not a good option for me. The whole project is not worth that much effort.

Thanks! I have a cheap Klein DMM I can take down tomorrow and check the voltage again to compare with the Fluke.


I believe your meter is most likely not a true RMS meter and taking an improperly calibrated reading on the modified sine wave inverter. If you could borrow a TRMS meter and test the AC output of the inverter it would tell you if your inverter is working. If my first guess is correct then most likely your stove and the inverter are not playing well together. Iím sorry I donít know how induction stoves are wired, and if they operate with simple circuitry or have some crazy computer in the in them. It sounds like they may need a good jolt of clean juice to kick in, which leads me to believe they also are more of an off/on type of battery drain than one that can be controlled? I would like to know more about them if anyone knows how the electricity is converted back to heat in these? Can they be dialed down and run at low power or are they cycling on and off at full throttle to maintain a temperature?
Back to top
View user's profile Send private message
DavidM



Joined: 24 Dec 2017
Posts: 188
City/Region: Punta Gorda
State or Province: FL
C-Dory Year: 2006
C-Dory Model: 22 Cruiser
PostPosted: Wed Jan 22, 2020 6:56 am    Post subject: Reply with quote

Whether the voltage is being read correctly doesn't change the fact that the induction stove won't come on unless something else is turned on first.

This is probably due to how the stove interacts with the inverter- it puts very little load on during its initial start up, so the inverter thinks it sees nothing and turns itself off.

So use the microwave or preferably a smaller load to get the stove started then turn it off.

David
Back to top
View user's profile Send private message Send e-mail
Mikew



Joined: 13 Jul 2015
Posts: 3
City/Region: Albany
State or Province: NY
PostPosted: Wed Jan 22, 2020 8:30 am    Post subject: Reply with quote

Mike, inverters stay in an idle state with no or low output voltage until they sense a load then go to full output voltage. This is so they donít draw high
Input current and drain your battery needlessly. Your stovetop has a smart
circuit built into it to protect it from low voltage. So these two devices have a
conflict when connected together, as you found out.
Try doing what David suggested , plug in a simple resistive load first , such as
a 60 watt light bulb, let the inverter come up to full voltage, then plug in the cooktop. You can then remove the bulb to save some power.

Mike
Back to top
View user's profile Send private message Send e-mail
Marco Flamingo



Joined: 09 Jul 2015
Posts: 884
City/Region: Seattle
State or Province: WA
C-Dory Year: 2004
C-Dory Model: 16 Cruiser
Vessel Name: Limpet
Photos: Limpet
PostPosted: Wed Jan 22, 2020 11:09 am    Post subject: Reply with quote

I've looked at this issue quite a bit, mostly on RV sites, and have concluded that you basically never know if an inexpensive induction burner will work with an inexpensive inverter. And if it doesn't, which to blame. I lucked out and my inexpensive burner ($50) works with my "inexpensive" ($250) inverter. I had read enough to know that I might have bought an induction burner that would end up being used at home and an inverter that was larger than I needed on board.

Most of the posts that I saw blame the inverter for being MSW "Modified Sine Wave." Electronic geeks say MSW is really am acronym for Modified Square Wave made to look like a sine wave. Okay, whatever. The fact is that some MSW inverters will power an induction burner and some don't. Some claim that certain brand names of MSW inverters are a better mimic of a true sine wave and that's why they work.

The best solution I saw was to go boat to boat (or RV to RV) with the induction burner and see whose inverter will power up the burner. The second "fix" was to borrow induction burners and try them with your inverter. Not a sophisticated electrical analysis, but might be the fastest solution.

I'm entertaining the idea right now of replacing a three burner propane oven/stove with a two burner induction cook top. The boat already has a 3KW MSW inverter. I think I'll plug in my induction burner first to see if that MSW inverter will power it. Even if it does, it probably isn't a guarantee that it will work with a newer cook top. Another "low tech" solution was to order the items on Amazon Prime and quickly try them. If they don't work, send them back within the return period. Again, not a sophisticated solution.

I also saw some interesting posts on how the burner senses whether there is a pot on it and is effected by the alloy of the pot. Common knowledge is that some pots don't work. Some even find that certain pots work better. What was surprising was that some pots work better because the induction burner draws more juice with the "good" alloys. A cast iron pot, while kind of a pain on a boat, might just pull enough juice to kick on the inverter.

Mark
Back to top
View user's profile Send private message Send e-mail Visit poster's website AIM Address
thataway



Joined: 02 Nov 2003
Posts: 17468
City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
Photos: Thataway
PostPosted: Wed Jan 22, 2020 12:08 pm    Post subject: Reply with quote

Nice video to explain True RMS and its importance. I agree with Mike W. These less expensive inverters do need a small load to come to full power, and the "on" circuit of the induction burner (I have an identical burner) is not enough to trigger the full output output of the MSW inverter

I err on the conservative side having owned MSW inverters since the early 70's (and the electrical "noise" going with them when hooked up to many appliances). I use a PSW inverter on the boat, coupled with 180 amps usable from the Li batteries.
My Victron does fine with the induction burner alone. One of the reasons I use the PSW, is that microwaves will run on the MSW, but don't seem to put out as much power, and make a lot more noise.

It really helps to have an oscilloscope to see what the true voltage and wave form is from an inverter. Some of the newer MSW are stepped so closely to sine wave, that many appliances work perfectly with them.

When it warms up a little, I'll take my simple "Kill-a Watt" meter to the boat and see what the draw of the induction burner is on its "on" setting. There are circuits in the induction burner which keeps it from turning on if there is not a ferrous or induction type of pot on the burner. I believe the circuits for even the cheap induction burner are not simple. There are variable power levels. They don't seem to vary in power use at each level, but I have not fully assessed this when cooking.

_________________
Bob Austin
Thataway
Thataway (Ex Seaweed) 2007 25 C Dory May 2018
Thisaway 2006 22' CDory November 2011 to May 2018
Caracal 18 140 Suzuki 2007 to present
Thataway TomCat 255 150 Suzukis June 2006 thru August 2011
C Pelican; 1992, 22 Cruiser, 2002 thru 2006
Frequent Sea; 2003 C D 25, 2007 thru 2009
KA6PKB
Home port: Pensacola FL
Back to top
View user's profile Send private message Send e-mail
TyBoo



Joined: 23 Oct 2003
Posts: 5056
City/Region: Warrenton
State or Province: OR
C-Dory Year: 1996
C-Dory Model: 25 Cruise Ship
Vessel Name: TyBoo
Photos: TyBoo
PostPosted: Wed Jan 22, 2020 1:27 pm    Post subject: Reply with quote

It sounds like I need an exciter on the boat. Maybe Lois is up to it. We are going back down to the dock to fool with it today so we will see if that does it.

That all makes sense and I will take a small lamp with a 60w bulb to try. I know that just the microwave being powered up and not running is not enough for make the stove work. If I start the microwave the stove will then turn on but stops if I open the MW door. Maybe I just need to let the induction stove get the inverter up to speed on its own before removing the other load. Or leave the lamp on. We will see.

Thanks, and I will let you know the progress.
Back to top
View user's profile Send private message Send e-mail
smckean (Tosca)



Joined: 18 Jan 2014
Posts: 387
City/Region: Guemes Island (Anacortes)
State or Province: WA
C-Dory Year: 2005
C-Dory Model: 25 Cruiser
Vessel Name: Tosca
Photos: Tosca
PostPosted: Wed Jan 22, 2020 3:07 pm    Post subject: Reply with quote

Tyboo,

Tosca has had an inverter for at least 10 years. It is mounted by hanging it under the splashwell. Water doesn't get to it there, but it is most certainly very damp in that compartment. Never had a problem running that inverter.

My only complaint is that I have to get out of the cabin and open the hatch to reach the switch to turn it on. I highly recommend getting the remote switch of which you spoke.
Back to top
View user's profile Send private message Send e-mail
TyBoo



Joined: 23 Oct 2003
Posts: 5056
City/Region: Warrenton
State or Province: OR
C-Dory Year: 1996
C-Dory Model: 25 Cruise Ship
Vessel Name: TyBoo
Photos: TyBoo
PostPosted: Wed Jan 22, 2020 3:23 pm    Post subject: Reply with quote

Thanks Tosca! That is just what I wanted to hear.

I found one inverter on Amazon that has both the remote switch and the ability to connect the remote it to a switched power source so I can kill it with the master disconnect I have at the helm. It is a true sine wave and more than twice what I was hoping to spend but Lois wants to cook.

Funny thing is, I discovered that the 20 year old 250 watt inverter that I could replace for nineteen bucks today will run the stove just fine. Probably not for long, but it does it like I would expect. Maybe I just have a dorky inverter. Donít tell Ďem but I might go the try/return route with Amazon until I find the right match.
Back to top
View user's profile Send private message Send e-mail
SnowTexan



Joined: 08 Aug 2019
Posts: 63
City/Region: Carlton
State or Province: WA
C-Dory Year: 2006
C-Dory Model: 22 Cruiser
Vessel Name: Miss Maria
Photos: Miss Maria
PostPosted: Fri Jan 24, 2020 1:37 pm    Post subject: Reply with quote

Did ya get it up and running?


Nigel
Back to top
View user's profile Send private message
TyBoo



Joined: 23 Oct 2003
Posts: 5056
City/Region: Warrenton
State or Province: OR
C-Dory Year: 1996
C-Dory Model: 25 Cruise Ship
Vessel Name: TyBoo
Photos: TyBoo
PostPosted: Fri Jan 24, 2020 2:12 pm    Post subject: Reply with quote

Not yet - the first of the Amazon inverters to try should get here with the mail in a couple hours. It's the cheap one I linked earlier.

I was going to go with the pure sine wave right off the bat but after discovering the old 250 watt inverter will run the stove on low power I figured the newer MSW one might work for a couple hundred bucks less. We will see.

Interesting how quickly electronics evolve and get better/cheaper as they do. Kind of the opposite of everything else. That old inverter was bought for my toolbox at work back in the mid '90s to run a laptop computer. I remember very well the cost of the thing because the limit at the time that a foreman could approve for direct purchase was $200, and the inverter was $199.99. I had already convinced the superintendant to buy the $2500 laptop for me even though I was just a dumb mechanic so I didn't want to push it any further. The same thing today - different brand but better specs - would cost less than fifty bucks.
Back to top
View user's profile Send private message Send e-mail
Display posts from previous:   
Post new topic   Reply to topic    The C-Brats Forum Index -> Electrical and Wiring All times are GMT - 6 Hours
Goto page 1, 2, 3  Next
Page 1 of 3

 
     Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You cannot download files in this forum



Page generation time: 0.1014s (PHP: 69% - SQL: 31%) - SQL queries: 32 - GZIP disabled - Debug on