small 24V inverters

wxh3

I am pondering switching my system to 24V (putting my 2 panels and 2 batteries in series). It would require me getting a small (<300W) 24V inverter. The main options I see are Samlex and Exeltech. Anyone have any opinions about either of these or others as well? It seems like the Exeltech is roughly twice as expensive. (Why?) I like the fact that in the 125W and 250W sizes it does not have a cooling fan. The Samlex 300W 12V inverter I have has a fan that kicks on at a pretty low wattage.

My continuous 24 hour load is less than 20W. On a normal day I would not expect to go above 60W. I really don't expect to need to ever go above 125W though nice to have the option I guess.

icarus

Re: small 24V inverters

If you do a google search there are lots of them out there in the 300 watt range 24vdc. I can't vouch for any of them however.

Tony

n3qik

Re: small 24V inverters

I am also looking at going from 12v to 24v. But have decided not to base on cost at this time. I look over my system and will not gain much by going to the higher voltage. Cheaper to add a panel or two.

You should look at what gains to cost ratio you will get. With a 12v system you have more options with lights, etc. If it is currently working for you, then let it be.

wxh3

Re: small 24V inverters

Well, I went ahead and got an Exeltech 250W XP inverter. Biggest complaint so far is that it is quite noisy. It has no fan but makes an audible high frequency buzzing/cricket-like noise constantly. Not super loud but very noticible if you are somewhat close to ithe inverter in a quiet room. Other inverters I've had haven't made any noise (that I've noticed anyway) if their cooling fans (if they had one) were off. Since the lack of noise from a fan was big reason I got this one instead of the much cheaper Samlex, it is pretty upsetting to me.

I do wonder if the noise is normal or if could be a problem with my inverter.

Second complaint is that the ground connection is on this small 6-pole connector that already has a required jumper in it to connect to AC neutral connector. It isn't very big..I don't think I can fit anything but 12-gauge wire in it with the jumper. Also the connector seems pretty flimsy. You have to remove the back cover (6 screws) to access the screws for the wire connectors.

Edit: When put a 65W load on the buzzing became much worse. Maybe most people have their inverters in places where they don't care about noise???

n3qik

Re: small 24V inverters

I have 2 inverters, other than fan noise, there is nothing coming from the inverter. I would contact the seller for replacement.

wxh3

Re: small 24V inverters

n3qik wrote: »

I have 2 inverters, other than fan noise, there is nothing coming from the inverter. I would contact the seller for replacement.

Are either of yours Exeltech inverters? Most of what I see on the internet regarding complaints from inverter "noise" is from RF interference...not audibile frequencies.

n3qik

Re: small 24V inverters

Nope, I have the cheapest inverters you can buy on ebay. One Xantrex 1000 Watt MSW and one Carspa 600 watt true sine.


Quote from Wind&Sun store:

"We have been selling Exeltech inverters for over 13 years, and we have never had one single report of any failure of any type. In fact, we have never even heard of one going bad that was not grossly abused (like hooking the battery terminals to AC power..)."

This plus others on the internet makes be believe you may have a bad one.

creakndale

Re: small 24V inverters

I have an ExcelTech XP-600 and unloaded it softly chirps once a second like an annoying cricket. As soon as I add any load, it stops chirping. The ExcelTech fan turns on when it's heavily loaded as expected.

It's good to know that other small inverters don't chirp under no load condition.

SavingEnergy

Re: small 24V inverters

I have two Exeltech 125w 12v inverters. They do not make any noise under any conditions. I would call the manufacturer and describe the the problem. Do not open the unit, you will void the warranty. I've called them to ask technical questions, and they have been very helpful. I think you picked a very good unit. They are American made, and have a very high mean time between failure rate.

By the way, they do make a 125w 24v version (according to the manual). It would be much more efficient than running a 250w model at 20-60w. I was told by one of their engineers that efficiency drops way off below 1/3 of the rated load of the inverter.

John

wxh3

Re: small 24V inverters

Tried a different 24V XP250 and also an XP125. Both behaved basically the same as the original. There is a soft audible buzz at low or no load, although the XP125 is a little quieter. However, determined that the really loud buzz/rattle occurs only when laptop(s) are part of the load. While the buzz does get a bit louder when adding the simliar loads of one or two 60W light bulbs (pulled them out of a closet...I switched completely to CFLs 6 years ago) it is much quieter than having a laptop load. Something about a laptop load looks different to the inverter than a light bulb load.

mike95490

Re: small 24V inverters

wxh3 wrote: »

Tried a different 24V XP250 and also an XP125. Both behaved basically the same as the original. There is a soft audible buzz at low or no load, although the XP125 is a little quieter. However, determined that the really loud buzz/rattle occurs only when laptop(s) are part of the load. While the buzz does get a bit louder when adding the simliar loads of one or two 60W light bulbs (pulled them out of a closet...I switched completely to CFLs 6 years ago) it is much quieter than having a laptop load. Something about a laptop load looks different to the inverter than a light bulb load.

Are these SINE wave inverters, or MOD [square] wave ? I would expect pure sinewave to be very quiet, and mod to be a little noisy.

wxh3

Re: small 24V inverters

mike90045 wrote: »

Are these SINE wave inverters, or MOD [square] wave ? I would expect pure sinewave to be very quiet, and mod to be a little noisy.

Pure Sine wave, not mod.

wxh3

Re: small 24V inverters

Got a Samlex 300W 24V inverter as it was was relatively inexpensive. It makes absolutely no sound at all when fan is off. However, even with no load connected the loud fan runs about half the time in a well-ventilated location in an 80F room. As the electrical noise from the Exeltech is more tolerable to me than the Samlex fan, I will probably use it during the warmer months and maybe try to switch to the Samlex when it gets cooler. Hopefully at 68F the fan will stay off with small loads....

I checked the no-load current of both inverters. The Samlex (with fan off) was 0.23 amps (5.75W) and the Exeltech 0.30 amps (7.5W). Both of those are a bit higher than the specs state. Maybe my meter is off a bit...

wxh3

Re: small 24V inverters

Solved the fan noise problem...opened up the unit and unplugged the fan. Will use the inverter for my small 24/7 loads (< 15W) and other stuff that maxes out at less than 35W. Also there is an auto-shutoff if it gets too hot. So far has been running fine and doesn't feel very warm at all with 35W load.

Tech support guy said go ahead for low loading but warranty would be voided. Fine with me. I have my other inverter in parallel for larger loads. It will normally be switched off.