Use mod sine wave for deep freeze?

[Yakapo]

It seems that quality psw inverters are out of my budget. Can I run a deep freeze off a mod sine wave inverter?

if not, can I get a pure sine for the deep freeze and run a mod sine at the same time off the same battery bank?

 

[gnubie]

You can but if it's a standard AC motor type the motor will run hotter as will the fan motor inside the fridge freezer if it has one, and the same for the auto-defrost timer motor if it has one of them. Any AC noise filter will also get a bit upset and buzz and get warmer than usual too.

If it's an inverter type fridge freezer and has active power factor correction it may not turn on at all.

Yes, you can run two inverters off the same bank at the same time, just keep an eye on the current you are pulling out of the battery.

 

[Yakapo]

You can but if it's a standard AC motor type the motor will run hotter as will the fan motor inside the fridge freezer if it has one, and the same for the auto-defrost timer motor if it has one of them. Any AC noise filter will also get a bit upset and buzz and get warmer than usual too.

If it's an inverter type fridge freezer and has active power factor correction it may not turn on at all.

Yes, you can run two inverters off the same bank at the same time, just keep an eye on the current you are pulling out of the battery.

can I run two 24v inverters in series off a 48v battery bank?

 

[gnubie]

No.

 

[Craig]

No.

Why Not?
Not saying one should but why not?

 

[gnubie]

Are you asking for yourself or the forum?

As a basic starting point, relative impedance. If you did stack two 24V loads in series and one was drawing 1 amp and the other 2, that would result in one thing receiving low voltage and the other kaboom voltage. If you then won the jackpot the kaboom one would go short effectively putting 48V across the other and it would go kaboom too.

 

[Hedges]

You could do it if you tapped middle of the 48V battery, so each inverter saw 24V of battery.
Then you have to keep it balanced, which would work best with two, 24V chargers. Some PV capacity would be wasted.

Maybe with enough inductive filtering, the corners (high frequencies) of the "modified sine wave" (I call it modified square wave) would be rounded enough that a motor would be OK.

"quality psw inverters are out of my budget" - Yakapo - what is your budget?

 

[Craig]

Are you asking for yourself or the forum?

As a basic starting point, relative impedance. If you did stack two 24V loads in series and one was drawing 1 amp and the other 2, that would result in one thing receiving low voltage and the other kaboom voltage. If you then won the jackpot the kaboom one would go short effectively putting 48V across the other and it would go kaboom too.

So it could be done if both inverters used the same amount of amps as each other?

 

[Craig]

You could do it if you tapped middle of the 48V battery, so each inverter saw 24V of battery.
Then you have to keep it balanced, which would work best with two, 24V chargers. Some PV capacity would be wasted.

Maybe with enough inductive filtering, the corners (high frequencies) of the "modified sine wave" (I call it modified square wave) would be rounded enough that a motor would be OK.

"quality psw inverters are out of my budget" - Yakapo - what is your budget?

I actually used the two charger trick to keep my 24volt marine/rv batteries balanced. it worked reasonably well as long as the panels all were in the same sun

 

[gnubie]

Sure but then you have two 24V batteries in series, not a 48V battery. If we want to put in any number of exceptions anything becomes possible. We could go out and get high amp buck converters and use them to run the 24V inverters too.

and to answer the other part, perhaps. You have only addressed one issue by some how contriving both inverters to present nigh on the same load at the same time... with absolutely no exceptions. Not sure how exactly that would be achieved. Whoops, microwave turned off and TV inverter blew up. Might be a slight drawback.

and I'm not really interested in picking apart the problems any more than this.

 

[Yakapo]

Sure but then you have two 24V batteries in series, not a 48V battery. If we want to put in any number of exceptions anything becomes possible. We could go out and get high amp buck converters and use them to run the 24V inverters too.

and to answer the other part, perhaps. You have only addressed one issue by some how contriving both inverters to present nigh on the same load at the same time... with absolutely no exceptions. Not sure how exactly that would be achieved. Whoops, microwave turned off and TV inverter blew up. Might be a slight drawback.

and I'm not really interested in picking apart the problems any more than this.

That makes sense.

 

[Yakapo]

You could do it if you tapped middle of the 48V battery, so each inverter saw 24V of battery.
Then you have to keep it balanced, which would work best with two, 24V chargers. Some PV capacity would be wasted.

Maybe with enough inductive filtering, the corners (high frequencies) of the "modified sine wave" (I call it modified square wave) would be rounded enough that a motor would be OK.

"quality psw inverters are out of my budget" - Yakapo - what is your budget?

I would like to get a 48v 2000 watt inverter for around $750.

I can get a Samlex 24v 2000 for $600, but then it’s hard to add more panels without upgrading the controller to something really expensive.

right now I have 6 x Trojan 8v batteries, and 3 x 300 watt panels. Next purchase is the inverter.

 

[Hedges]

Here's the 48V inverter I have:

SMA SUNNY ISLAND 6048-US. Brand New. | eBay

Model 6048-US.

www.ebay.com

I've been seeing them for $2200 delivered, but not at the moment. 3x your target price.

Why 48V if you don't have an inverter yet?
Wire your batteries as 3s2p for 24V, and there will be better selection of economical inverters.

Is that 190 Ah? 190 x 8 x 6 = 9120 Wh.

Trojan Battery | Battery Maintenance

The key to achieving optimum performance and long battery life is to follow a regular care and maintenance program. Read our tips for high performance battery maintenance.

www.trojanbattery.com

"Charge between 10% and 13% of 20 hour rate."
you've got 900W STC of panels, might achieve 750W peak charging.
Need at least one more panel.
Ideal charge current would be 35 to 40A (assuming 26V)
How about a charge controller with that maximum output, and over-panel (with panels at multiple orientations) for sustained steady current?
For instance, two of these, IF they can be paralleled and working in same mode at same time (I'm not sure)

Epever 2210 20A MPPT Solar Charge Controller - SanTan Solar Store

Buy our Epever 2210 20A MPPT Solar Charge Controller for just $85. Click the link to start shopping today!

store.santansolar.com

 

[Yakapo]

Here's the 48V inverter I have:

SMA SUNNY ISLAND 6048-US. Brand New. | eBay

Model 6048-US.

www.ebay.com

I've been seeing them for $2200 delivered, but not at the moment. 3x your target price.

Why 48V if you don't have an inverter yet?
Wire your batteries as 3s2p for 24V, and there will be better selection of economical inverters.

Is that 190 Ah? 190 x 8 x 6 = 9120 Wh.

Trojan Battery | Battery Maintenance

The key to achieving optimum performance and long battery life is to follow a regular care and maintenance program. Read our tips for high performance battery maintenance.

www.trojanbattery.com

"Charge between 10% and 13% of 20 hour rate."
you've got 900W STC of panels, might achieve 750W peak charging.
Need at least one more panel.
Ideal charge current would be 35 to 40A (assuming 26V)
How about a charge controller with that maximum output, and over-panel (with panels at multiple orientations) for sustained steady current?
For instance, two of these, IF they can be paralleled and working in same mode at same time (I'm not sure)

Epever 2210 20A MPPT Solar Charge Controller - SanTan Solar Store

Buy our Epever 2210 20A MPPT Solar Charge Controller for just $85. Click the link to start shopping today!

store.santansolar.com

160ah - which would be 7.68 kWh.

why 48v? Well I guess I was trying to make it work with one controller. They had a larger allowed wattage if you used a 48v battery. It never occurred to me that I could use two controllers.

I can get another panel for next to nothing. I measured them with a multimeter the other day and was getting over 290 watts per panel. 40 volt panels by the way.

$75! That is much less than I anticipated spending. But the max pv input is 520 watts,

 

[Steve_S]

Pure Sine Wave versus Modified Sine Wave Inverters

FAQs | Find answers about our power products | Samlex America

Have a question about Samlex power conversion products? Refer to our FAQs for both general information and product specific FAQs.

www.samlexamerica.com

Pure Sine Wave vs. Modified Sine Wave Inverters – What’s the Difference?

Pure Sine Wave vs. Modified Sine Wave Inverters- What's the Difference?

Click here to learn the difference between a pure sine wave and a modified sine wave inverters. altE Store - Making renewable do-able since 1999.

www.altestore.com

 

[Supervstech]

I agree... unless you have a huge load needing 48V for wire and fuse protection, going 48V isn’t practical...

That said, I have a 48V diy solar generator I built with a 1500W Aims pure sinewave HF inverter that I paid around $300 for...
How big is your deep freeze?

 

[Hedges]

160ah - which would be 7.68 kWh.

why 48v? Well I guess I was trying to make it work with one controller. They had a larger allowed wattage if you used a 48v battery. It never occurred to me that I could use two controllers.

I can get another panel for next to nothing. I measured them with a multimeter the other day and was getting over 290 watts per panel. 40 volt panels by the way.

$75! That is much less than I anticipated spending.

One controller would be preferred. You don't have many panels yet. You can get higher current charge controllers, but I think your battery's desired charge rate is the limit.

Figure out what loads you want to power. Does this have to be entirely off-grid, year round? In that case, using the reduced sun available in December/January, figure out how many panels are needed. Design a system that supports all your loads, probably from a single sine-wave inverter (cheaper per watt if larger)

The thing about DC coupling (unless there are some smart units communicating with inverter, or if they use a current sense at battery and have programmable charge current), is that batteries have to accept all the current PV produces. And charge rate is limited to what PV produces. FLA and SLA have preferred charge rates.

That is why I suggest sizing MPPT charge controller to the battery, and over-paneling with strings of panels at various angles. Then you can get optimum charge current for several hours of the day. Panels are cheap. Batteries are expensive.

 

[Yakapo]

One controller would be preferred. You don't have many panels yet. You can get higher current charge controllers, but I think your battery's desired charge rate is the limit.

Figure out what loads you want to power. Does this have to be entirely off-grid, year round? In that case, using the reduced sun available in December/January, figure out how many panels are needed. Design a system that supports all your loads, probably from a single sine-wave inverter (cheaper per watt if larger)

The thing about DC coupling (unless there are some smart units communicating with inverter, or if they use a current sense at battery and have programmable charge current), is that batteries have to accept all the current PV produces. And charge rate is limited to what PV produces. FLA and SLA have preferred charge rates.

That is why I suggest sizing MPPT charge controller to the battery, and over-paneling with strings of panels at various angles. Then you can get optimum charge current for several hours of the day. Panels are cheap. Batteries are expensive.

This one should work for 4 panels. It has three stage charging and temperature compensatio.

Epever 6415AN 60A MPPT Solar Charge Controller - SanTan Solar Store

Buy our Epever 6415AN 60A MPPT Solar Charge Controller for artistic, economical and practical efficiency for $250.00 today!

store.santansolar.com

It’s a 75’ run from the panels to my garage. The panels will be in my back yard. I can adjust the angle based on the season.

 

[Hedges]

Yes, that charge controller and wiring should work for four panels and your batteries in 24V configuration.
Charge rate will vary, following peak output of panels.

To provide optimal charge rate, that charge controller and 9 batteries wired 3s3p, and over-paneling so charge controller would produce 60 amps for several hours per day (at 26V or so as battery charges). 13,680 kWh of battery charged at 1560 W

Ideally there would be a shunt to measure battery current and charge controller would be programmable to set charge current (would deliver more current to cover what loads consume so battery charge current constant.) I don't know if any DC charge controllers offer that.

 

[Yakapo]

Yes, that charge controller and wiring should work for four panels and your batteries in 24V configuration.
Charge rate will vary, following peak output of panels.

To provide optimal charge rate, that charge controller and 9 batteries wired 3s3p, and over-paneling so charge controller would produce 60 amps for several hours per day (at 26V or so as battery charges). 13,680 kWh of battery charged at 1560 W

Ideally there would be a shunt to measure battery current and charge controller would be programmable to set charge current (would deliver more current to cover what loads consume so battery charge current constant.) I don't know if any DC charge controllers offer that.

$20 shunt and battery monitor I’ll get.

Amazon.com

And I already have a 100a busman breaker for the positive side of the battery bank.

However, I’d rather not have to buy more batteries. The project is mainly for backup. (Which is not that frequent). I could have bought a generator, but this task looked more interesting and I don’t have to store fuel. Total daily use might be 2.5kwh per day. At the most.