Hybrid Inverter with low starting voltage

barax · Aug 4, 2023

Hi,

I am trying to find a hybrid Inverter/all in one which can start mppt with a low voltage. For solar I am using only panels within balconies.

I have found the 24v 3000w EcoWorthy hybrid Inverter.

Do you know of any similarly specked startup voltage hybrid inverters?

They seem very rare/I cannot find any.

Thanks in advance

DIYrich · Aug 4, 2023

What specs are you looking for?
I believe the Victron EasyShare 24v has a minimum mppt voltage of battery voltage +5v, or around 32v

barax · Aug 4, 2023

DIYrich said:
What specs are you looking for?
I believe the Victron EasyShare 24v has a minimum mppt voltage of battery voltage +5v, or around 32v

Since the solar array is small, I am trying to find something which starts the mppt with low voltage. My panels are 12v.

From eco worthy site: https://it.eco-worthy.com/collectio...le-pura-e-controller-60a-per-sistema-off-grid

This what seems to be a good range for me:

Solar input voltage range: 30Vdc~100Vdc

I don't have many panels to play with but doing them in pairs or threes in series and then in parallel with the combined ones should work

RCinFLA · Aug 4, 2023

HF hybrid inverters PV charge controllers boost the PV voltage up to inverter's high voltage DC bus. Bus is about 250vdc for 120vac inverters and 500 vdc for 230vac inverters. Some 120vac units have an additional intermediate DC to DC converter to convert 500vdc to 250vdc between output of PV controller and 120vac inverter's 250vdc internal bus. This allows up to 500vdc PV input on a 120vac inverter.

For HF AIO inverters, the lower the operating voltage of PV array, the more voltage boost required by the PV controller and the lower the conversion efficiency by PV controller's boost DC to DC converter. Best efficiency of converter is when PV array Voc is near the maximum allowed by inverter where Vmp is running as close to inverter's HV DC bus as it can get. (This is typically where the manf. specs their PV efficiency.)

All the present offered LF AIO inverters use a PV charge controller that down converts PV DC voltage directly to battery terminals on inverter. They have better PV conversion efficiency when run with lower PV array voltage.

As the PV DC to DC converter difference in input to output voltage gets greater the switching duty cycle of DC to DC converter is reduced. There is a limit to how short of time the switching duty cycle can be run to maintain stability of DC-to-DC converter.

barax · Aug 4, 2023

RCinFLA said:
HF hybrid inverters PV charge controllers boost the PV voltage up to inverter's high voltage DC bus. Bus is about 250vdc for 120vac inverters and 500 vdc for 230vac inverters. Some 120vac units have an additional intermediate DC to DC converter to convert 500vdc to 250vdc between output of PV controller and 120vac inverter's 250vdc internal bus. This allows up to 500vdc PV input on a 120vac inverter.

For HF AIO inverters, the lower the operating voltage of PV array, the more voltage boost required by the PV controller and the lower the conversion efficiency by PV controller's boost DC to DC converter. Best efficiency of converter is when PV array Voc is near the maximum allowed by inverter where Vmp is running as close to inverter's HV DC bus as it can get. (This is typically where the manf. specs their PV efficiency.)

All the present offered LF AIO inverters use a PV charge controller that down converts PV DC voltage directly to battery terminals on inverter. They have better PV conversion efficiency when run with lower PV array voltage.

As the PV DC to DC converter difference in input to output voltage gets greater the switching duty cycle of DC to DC converter is reduced. There is a limit to how short of time the switching duty cycle can be run to maintain stability of DC-to-DC converter.
View attachment 161002

Thank you, I am trying to understand.

If I got it right, and in my case I need a single phase 240v ac;

Both high frequency and low frequency all in one inverters will utilize the PV array.

Say I need 3.5kw inverter. I must choose one that is low frequency so that the 12v panels might reach its maximum right?

I understood that each panel might operate around 18v. So if I have 10, it would only be 180v at peak, and only if connected in series. Correct?

If I arrange them with groups of 36v each then I should aim for a low frequency inverter because the lower the better?

Am I missing something?

RCinFLA · Aug 4, 2023

You also have to consider the current and associated wire gauge required for lower voltage PV arrays with higher PV array current.

For HV inverters, you should not consider any array less than about 1000 watts. HF inverters consume about 50-60 watt of overhead power just to charge batteries. LF AIO's consume about 10-15 watts of PV overhead power to charge battery, but PV to AC output loss is greater due to having to run the AC output inverter to convert from battery voltage PV injection to AC output.

barax · Aug 4, 2023

RCinFLA said:
You also have to consider the current and associated wire gauge required for lower voltage PV arrays with higher PV array current.

For HV inverters, you should not consider any array less than about 1000 watts. HF inverters consume about 50-60 watt of overhead power just to charge batteries. LF AIO's consume about 10-15 watts of PV overhead power to charge battery, but PV to AC output loss is greater due to having to run the AC output inverter to convert from battery voltage PV injection to AC output.

Great, got it thank you. Any low frequency AIO brand you recommend?

RCinFLA · Aug 4, 2023

barax said:
Great, got it thank you. Any low frequency AIO brand you recommend?

Victron, Xantrex, Outback. Stay away from 240 vac LF inverters that do not provide an AC input neutral if you are planning grid interconnect to AC input. A good LF inverter provides AC input power supplementing which is very nice to have when running from a generator input to avoid overloading generator.

barax · Aug 4, 2023

RCinFLA said:
Victron, Xantrex, Outback. Stay away from 240 vac LF inverters that do not provide an AC input neutral if you are planning grid interconnect to AC input. A good LF inverter provides AC input power supplementing which is very nice to have when running from a generator input to avoid overloading generator.

Top! Thanks a lot. Off to google!

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