Battery pack with AC output with modified sine wave - SA330X

[Per Burström]

Hi,
I have a true sine wave AC inverter which I have used with very good results both with the Yamaha DXR10 I used to have as well as my current Fishman SA330X. The inverter I have been using both with a 18 Ah as well as a much larger lead acid battery. However, this combo is pretty heavy, mostly due to the weight of the battery, but even the inverter is rather heavy.

With the 18 Ah battery I can run my SA330X for around 3 hours at moderate volumes while playing at home.

Now I'm looking at getting combined battery and inverter, with between 20 and 30 Ah. However, these packs have a modified sine wave for the AC outlet. Anyone who has any experience in using of of these with their amplifier?

Thanks in advance!
Per

[jonfields45]

Another option would be a lithium battery for your inverter. I just ordered one of these:

https://www.ebay.com/itm/DC-12V-9800...72.m2749.l2649

Probably a little less risky to buy something branded:

https://smile.amazon.com/TalentCell-...8-2-fkmr0&th=1

I have one of these which helped me figure out how much power I really need (about 15 watts continuous for passive mixing into my CP8):

https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1

[phcorrigan]

I copied this from somewhere: "Modified sine wave power inverters will run about 90% of the applications out there, but most often not as cleanly or efficiently as a pure sine inverter. For powering typical resistive loads such as appliances and lights, a modified sine wave inverter is a cost-effective, reliable choice."

An electronic device is not a resistive load. A modified sine wave is also known as a stepped square wave. I would avoid this type of device for use with electronics.

[jonfields45]

Originally Posted by phcorrigan

I copied this from somewhere: "Modified sine wave power inverters will run about 90% of the applications out there, but most often not as cleanly or efficiently as a pure sine inverter. For powering typical resistive loads such as appliances and lights, a modified sine wave inverter is a cost-effective, reliable choice."

An electronic device is not a resistive load. A modified sine wave is also known as a stepped square wave. I would avoid this type of device for use with electronics.

Not sure you've got that right... Generally speaking, any load with a much larger start-up current, or poor power factor, is going to be a bad match to any inverter that does not have lots of current head room (meaning watts in the clobbered nomenclature of these devices). This would include fluorescent lights and motors. Generally speaking most electronics will have reasonable power factors and start up currents. But modified sine wave, or pure sine wave, high start up current and poor power factor are problems for both.

My experience with MSW inverters and powered PA speakers (QSC & Yamaha) is pure sine wave is not a requirement, but since they are cheap and generally have other features I like (temperature controlled fans), that is what I own.

[Mandobart]

What size is your inverter? I have a 200 W Cotek pure sine wave inverter that easily powers my Carvin AG300 (rated at 250 W when used with a 2nd cabinet). The inverter alone weighs maybe a couple pounds. I use it with a 70 amp-hour deep cycle lead acid battery. I built a small frame with a handle that houses these along with an AC powerstrip and panel with a 12 VDC outlet, voltmeter and USB charger port. The whole thing weighs just under 30 lbs and will run my amp and accessories for about 7 hours.

[Per Burström]

Originally Posted by Mandobart

What size is your inverter? I have a 200 W Cotek pure sine wave inverter that easily powers my Carvin AG300 (rated at 250 W when used with a 2nd cabinet). The inverter alone weighs maybe a couple pounds. I use it with a 70 amp-hour deep cycle lead acid battery. I built a small frame with a handle that houses these along with an AC powerstrip and panel with a 12 VDC outlet, voltmeter and USB charger port. The whole thing weighs just under 30 lbs and will run my amp and accessories for about 7 hours.

My inverter is a HQ rated at 300 W, and as I wrote it works really well. However, I have measured the power consumtion of the SA330X at moderate volume (playing at home) and it use less than 30 W. So my thought was to complement the powerful and heavy solution with something lighter, for example if have my eyes on a 20 Ah (at 5 V though) litium pack that can give 65 W at the AC outlet. But then it would be a modified sine wave.

/Per

[foxyloxy]

Hi Per. This answer is not strictly what you asked for, but I have been alarmed how many people connect mains equipment to an inverter without putting a fuse or tripswitch in the battery circuit. Batteries are quite capable of frying the wires to the inverter if there is a short, and Lithium batteries are much more reactive than lead-acid types, so it's very important to avoid getting them hot, we read about people getting injured when an iphone battery goes wrong, and you are talking about a much more powerful battery. Of course you may already be aware of the need for a fuse/tripswitch, but lots of people are not.

[Puerto Player]

I use a 2,000 watt inverter and a lead acid deep cycle battery mounted in a plastic crate with handles. It's heavy, but a a cheap little folding dolly works great if it's too far. I use it for a lot off different things, not just portable amps.

[jonfields45]

I just saw this today in an ad from Monoprice. It claims full sine wave. Not too pricey and at 220 watt-hour should power your regular PA at acoustic music volumes for a three set gig. It is SLA but not crazy heavy at 18 lbs. I've generally had very good luck with Monoprice's products. I would take one of these and a standard powered PA speaker before climbing onto the S1 or Loudbox Mini Charge bandwagons.

https://www.monoprice.com/product?p_...eryName=DM6490

When my $20 rechargeable lithium battery shows up I'll report how long it can run my CP8 at high volume. But I've run into a few hitches kitting this up for someone who is not an EE. My inverter is no longer for sale. These things are likely the product of a first world semiconductor company application note and designed/manufactured most often in China. My strategy was to find a major solar or marine supply importer assuming they would apply a reasonable qualification process to a low end inverter (given they need a good reputation to sell the expensive stuff). That worked for me last time but to start over would be a blind recommendation.

The other problem is most of the common cheap batteries use M5525 or M5521 (Tube Screamer standard stomp box power plug dimensions) output jacks with center positive. I have found cables to take that to banana plugs for the inverter, but so far only available China post and nothing in the US. No problem for me to solder something up as I've got all the piece parts.

[jonfields45]

Originally Posted by jonfields45

Another option would be a lithium battery for your inverter. I just ordered one of these:

https://www.ebay.com/itm/DC-12V-9800...72.m2749.l2649

Probably a little less risky to buy something branded:

https://smile.amazon.com/TalentCell-...8-2-fkmr0&th=1

I have one of these which helped me figure out how much power I really need (about 15 watts continuous for passive mixing into my CP8):

https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1

The cheaper battery showed up today with what amounts to a 3.5 watt charger. Assuming the battery is really 9800 mAh @ 12 volts (roughly 120 watt hours) it is going to take over a day to charge :~(! Not a confidence builder so far.

Update: I dug through my old power supply shoe box and found a 12 volt 1 amp power supply whose connector was just right M5521 and 14 volts open circuit (higher than the 12.6 to trigger charging). According to my power meter I am now charging at 11 watts.

Update 2 - It doesn't work. Turning on the inverter collapses the battery output to a few volts triggering the inverter under voltage fault.

[agedhorse]

I strongly discourage the use of MSW inverters with most modern electronic devices. The modified sine wave can interact with SMPS control circuitry as well as power factor correction circuitry if present. They are also very noisy electronically and can result in noise feed-through to the power supply and power amplifier's rails (which have almost no noise rejection).

PSW inverters are far superior, but the battery and inverter must be sized to supply the inrush current that electronic loads require. If it can't supply adequate current, either the inverter will shut down, fail, or cause problems with the load itself.

[Big Band Guitar]

A 1 to 1 isolation transformer would smooth out the modified sine wave.

The more iron in the power supply the better.

I would say if there is no power transformer in whatever your using don't use modified sine wave. I wouldn't run a switching power supply off one either.

[agedhorse]

Originally Posted by Big Band Guitar

A 1 to 1 isolation transformer would smooth out the modified sine wave.

The more iron in the power supply the better.

I would say if there is no power transformer in whatever your using don't use modified sine wave. I wouldn't run a switching power supply off one either.

Not really. A transformer in general reflects what's presented at the primary to the secondary multiplied by the transformer ratio. Because there is good coupling from primary to secondary (electromagnetic at low frequencies and electrostatic at high frequencies due to capacitance between pri and sec) the noise tends to couple pretty well. There are true isolation transformers with specially designed magnetic circuits that will reduce coupling, but this is more for common mode noise. Something else that can be an issue with MSW is excessive heating of the transformer core due to abrupt changes in magnetic flux at the MSW step points.

Virtually every device uses a transformer to isolate the amplifier from the primary of the power system, it's virtually guaranteed by the global agency safety regulations that amplifier products are designed and tested to. SMPS also have a transformer, but it's just in a different location.

Using a MSW inverter is not recommended with any audio electronic device.

[phcorrigan]

Originally Posted by agedhorse

I strongly discourage the use of MSW inverters with most modern electronic devices. The modified sine wave can interact with SMPS control circuitry as well as power factor correction circuitry if present. They are also very noisy electronically and can result in noise feed-through to the power supply and power amplifier's rails (which have almost no noise rejection).

Agreed. (I have to add this stuff because my message was too short!)

[jonfields45]

Given PSW inverters are getting to be very reasonably priced I agree an MSW is not worth the risk, if for no other reason you are scraping the bottom of the price/quality barrel at the powers we need. However, I used one for years (Harbor Freight bottom of the line!) with various powered speakers and mixers and never had an issue. Assuming the first power supply stage of your speaker/amp/etc. (with or without transformer coupling) is rectification and filtering (and then off to the switching regulator if that is the topology), it really should not matter (though bad design finds its way into many products...). I've discussed it with with QSC tech support (years ago) and they said MSW was just fine for their products (original K series back then).