Floating neutral DC from generator

[Nick R.]

Hello,

Is it possible to use a generator with floating neutral DC to charge battery?
8.3 amps/12 VDC

Ultra-Quiet 2200i™

powerequipment.honda.ca

What would be the most suitable battery for this "charger"?

Thank you.

 

[FilterGuy]

The generator spec says:

DC Output Volts / Amps | 12 / 8.3

12V is too low to charge either Lead Acid or LiFePO4 unless you have some type of boost converter to boost it to a higher voltage.
I do not know of a charge controller that can also boost the output to a higher voltage than the input. (They may exist. I am just not aware of one).
That leaves using a stand alone DC-DC boost converter. If you just used a boost converter you could charge the battery to a specified voltage, but if you leave it on for a long period it would not be good for the battery. Since this is a gas generator, I assume it will not be used continuously so maybe that is ok. If not, then you need to add a charge controller between the boost converter and the battery. With the energy losses through each device, you will be getting less than 8A of charge for all the effort.

Bottom Line: I don't think it is worth trying. Instead, get an AC-DC charger and use the AC output of the generator.

 

[tigerwillow1]

The DC output of the eu2200i is unfiltered and unregulated. It's simply a generator winding run through a full-wave bridge rectifier to the connector on the panel. Its output is pulsating DC that is suitable for charging flooded lead acid batteries and possibly nothing else. AGM batteries are said to be damaged by ripple on the charging supply, so I'd expect this output to kill an AGM battery in short order. Even though the charging output is ok to use on a flooded battery, it is very inefficient. When in use, the "eco" switch has to be turned off. It's an ok emergency charging source. If used regularly, you're much better off plugging a charger into the generator's AC output. The situation is the same with just about every portable generator with a battery charging output. You can see for yourself from the instructions and wiring diagram in the eu2200i manual.

 

[Nick R.]

The generator spec says:

DC Output Volts / Amps | 12 / 8.3

12V is too low to charge either Lead Acid or LiFePO4 unless you have some type of boost converter to boost it to a higher voltage.
I do not know of a charge controller that can also boost the output to a higher voltage than the input. (They may exist. I am just not aware of one).
That leaves using a stand alone DC-DC boost converter. If you just used a boost converter you could charge the battery to a specified voltage, but if you leave it on for a long period it would not be good for the battery. Since this is a gas generator, I assume it will not be used continuously so maybe that is ok. If not, then you need to add a charge controller between the boost converter and the battery. With the energy losses through each device, you will be getting less than 8A of charge for all the effort.

Bottom Line: I don't think it is worth trying. Instead, get an AC-DC charger and use the AC output of the generator.

Thank you very much! AC-DC charger then.

What would be the "sweet spot" best AC-DC charger, battery combination, to utilize the 2200 watts AC output, to charge a battery as large capacity as possible (maybe a rack mount LiFePO4?), running the generator as short period of time as to get battery fully charged?

The charged battery would use an inverter to provide about 150 watts 120 AC for a gas boiler.

This is a emergency power failure scenario to keep a gas boiler running in the winter, initially from a fully charged battery, if that runs out of power to use the gas generator to keep the boiler running and simultaneously get the battery recharged with the extra power from the generator. Once the battery is recharged, the generator would be shut down, boiler would keep running from the battery - until it runs out again. Hopefully by then the power is restored, if not, gas generator started up, the cycle continues.

Thank you again!

 

[Nick R.]

The DC output of the eu2200i is unfiltered and unregulated. It's simply a generator winding run through a full-wave bridge rectifier to the connector on the panel. Its output is pulsating DC that is suitable for charging flooded lead acid batteries and possibly nothing else. AGM batteries are said to be damaged by ripple on the charging supply, so I'd expect this output to kill an AGM battery in short order. Even though the charging output is ok to use on a flooded battery, it is very inefficient. When in use, the "eco" switch has to be turned off. It's an ok emergency charging source. If used regularly, you're much better off plugging a charger into the generator's AC output. The situation is the same with just about every portable generator with a battery charging output. You can see for yourself from the instructions and wiring diagram in the eu2200i manual.

the generator.

Thank you very much! AC-DC charger then.

What would be the "sweet spot" best AC-DC charger, battery combination, to utilize the 2200 watts AC output, to charge a battery as large capacity as possible (maybe a rack mount LiFePO4?), running the generator as short period of time as to get battery fully charged?

The charged battery would use an inverter to provide about 150 watts 120 AC for a gas boiler.

This is a emergency power failure scenario to keep a gas boiler running in the winter, initially from a fully charged battery, if that runs out of power to use the gas generator to keep the boiler running and simultaneously get the battery recharged with the extra power from the generator. Once the battery is recharged, the generator would be shut down, boiler would keep running from the battery - until it runs out again. Hopefully by then the power is restored, if not, gas generator started up, the cycle continues.

Thank you again!

 

[Skypower]

Thank you very much! AC-DC charger then.

What would be the "sweet spot" best AC-DC charger, battery combination, to utilize the 2200 watts AC output, to charge a battery as large capacity as possible (maybe a rack mount LiFePO4?), running the generator as short period of time as to get battery fully charged?

The charged battery would use an inverter to provide about 150 watts 120 AC for a gas boiler.

This is a emergency power failure scenario to keep a gas boiler running in the winter, initially from a fully charged battery, if that runs out of power to use the gas generator to keep the boiler running and simultaneously get the battery recharged with the extra power from the generator. Once the battery is recharged, the generator would be shut down, boiler would keep running from the battery - until it runs out again. Hopefully by then the power is restored, if not, gas generator started up, the cycle continues.

Thank you again!

Keep in mind the “running watts” rating, not the watts on the big decal. That Honda 2200 is rated at 1800 running and a 2200 surge. So your max AC amps continuous is 15.

 

[FilterGuy]

Thank you very much! AC-DC charger then.

What would be the "sweet spot" best AC-DC charger, battery combination, to utilize the 2200 watts AC output, to charge a battery as large capacity as possible (maybe a rack mount LiFePO4?), running the generator as short period of time as to get battery fully charged?

The charged battery would use an inverter to provide about 150 watts 120 AC for a gas boiler.

This is a emergency power failure scenario to keep a gas boiler running in the winter, initially from a fully charged battery, if that runs out of power to use the gas generator to keep the boiler running and simultaneously get the battery recharged with the extra power from the generator. Once the battery is recharged, the generator would be shut down, boiler would keep running from the battery - until it runs out again. Hopefully by then the power is restored, if not, gas generator started up, the cycle continues.

Thank you again!

There are a few limits that you want to consider.

1) What charge current are your batteries rated for? If you have 4 batteries that are each rated for up to 100A charge current, then the max charge current for the batteries is 400A. However, if you only have 1 battery it would be 100A.

Since you illuded to wanting to grow the system over time this presents a little bit of a problem because you don't want a 400A charger on a single battery thinking you will add batteries later.

2) What is the 'available' power from the generator? As @Skypower mentioned you have to start with the 'continuous power rating (1800W), then you need to subtract out any power the boiler and other loads will be using. The remainder can be put toward charging the battery.

3) What is your budget? Unfortunately, AC-DC chargers can be surprisingly expensive compared to other equipment we discuss here on the channel. The good news though is that you can parallel chargers. This means that you could start small and add additional chargers as the budget permits. This also allows you to add additional charging capacity as you add additional batteries. (See point 1 above).

I normally tell people to stay away from power supplies as chargers because a power supply will hold the battery at the charge voltage permanently. This can age the battery rapidly. However, in the scenario described, the power supply would not be on permanently so this would not be an issue. Consequently, power supplies could be used for your needs and may be a cheaper solution. (If you go this route, make sure the power supplies can be paralleled).

Do you have an inverter? what type is it?

 

[tigerwillow1]

When sizing a charger, you also have to take its power factor into consideration. While the generator is advertised in watts, it is actually rated in VA. If you can find a power factor corrected charger, that's great. If it's not power factor corrected, chances are that you won't find the power factor in its specs. Without knowing that, I'd assume a typical power factor of 0.7, and efficiency of 80%. Starting with 1,800 VA and multiplying it by 80% efficiency and a 0.7 power factor gives you 1,008 watts of DC output. At the typical 14.4 volt bulk charge level, that's 70 amps. A good candidate for a charger is an RV power converter. Some standard sizes are 45, 60 and 80 amps. The eu2000i is maxed out with a 60 amp converter (not power factor corrected). Maybe you could get away with 80, maybe not. Also, if you're much above 1,000 feet in altitude, the available generator output will begin to taper off as you go higher.

 

[Nick R.]

Keep in mind the “running watts” rating, not the watts on the big decal. That Honda 2200 is rated at 1800 running and a 2200 surge. So your max AC amps continuous is 15.

Yes, thank you!

 

[Nick R.]

There are a few limits that you want to consider.

1) What charge current are your batteries rated for? If you have 4 batteries that are each rated for up to 100A charge current, then the max charge current for the batteries is 400A. However, if you only have 1 battery it would be 100A.

Since you illuded to wanting to grow the system over time this presents a little bit of a problem because you don't want a 400A charger on a single battery thinking you will add batteries later.

2) What is the 'available' power from the generator? As @Skypower mentioned you have to start with the 'continuous power rating (1800W), then you need to subtract out any power the boiler and other loads will be using. The remainder can be put toward charging the battery.

3) What is your budget? Unfortunately, AC-DC chargers can be surprisingly expensive compared to other equipment we discuss here on the channel. The good news though is that you can parallel chargers. This means that you could start small and add additional chargers as the budget permits. This also allows you to add additional charging capacity as you add additional batteries. (See point 1 above).

I normally tell people to stay away from power supplies as chargers because a power supply will hold the battery at the charge voltage permanently. This can age the battery rapidly. However, in the scenario described, the power supply would not be on permanently so this would not be an issue. Consequently, power supplies could be used for your needs and may be a cheaper solution. (If you go this route, make sure the power supplies can be paralleled).

Do you have an inverter? what type is it?

Thank you very much for the great, detailed explanation.

I don't have any equipment yet, I am planning this emergency setup from ground up, based on the Honda generator, which is simple enough for my daughter to operate at her house. It is basically for frigid Canadian winters, where we have frequent power failures, during these times the natural gas supply tends to be intact, so only the lack of electric power for the gas furnace is what prevents the heating system to keep working.

The only thing that I may consider to expand with the system in the future is the option to add solar panel as an alternate charging of the batteries, as a supplement to the generator. I would like to buy the largest capacity battery that the generator (and potentially equal or lower capacity solar panels) output can serve for charging.

For your last point about keeping the batteries (fully) charged from the regular power supply: I was thinking of providing household power on a timer, using the cheapest nightly rate power, maybe with an additional feedback, where the power is not connected at all once the battery is fully charged and turn back on charging automatically when in time the battery charge naturally drops to a certain level, even without any load on it. I was actually hoping that an intelligent charger has this feature to monitor whether it should charge or not.

I hope it's not very confusing - thank you very much again all your kind assistance.

 

[Nick R.]

When sizing a charger, you also have to take its power factor into consideration. While the generator is advertised in watts, it is actually rated in VA. If you can find a power factor corrected charger, that's great. If it's not power factor corrected, chances are that you won't find the power factor in its specs. Without knowing that, I'd assume a typical power factor of 0.7, and efficiency of 80%. Starting with 1,800 VA and multiplying it by 80% efficiency and a 0.7 power factor gives you 1,008 watts of DC output. At the typical 14.4 volt bulk charge level, that's 70 amps. A good candidate for a charger is an RV power converter. Some standard sizes are 45, 60 and 80 amps. The eu2000i is maxed out with a 60 amp converter (not power factor corrected). Maybe you could get away with 80, maybe not. Also, if you're much above 1,000 feet in altitude, the available generator output will begin to taper off as you go higher.

Thank you very much, very useful, great explanation and calculation method. I will ask Honda about the power factor and efficiency. Altitude is not an issue.

 

[FilterGuy]

I don't have any equipment yet,

Good! Make a complete plan before you start buying. It is very easy to start buying too soon only to discover you bought the wrong things.


Will there be an inverter?
What DC voltage are you thinking?
Do you have a preliminary drawing of the system you are considering?

 

[Nick R.]

Good! Make a complete plan before you start buying. It is very easy to start buying too soon only to discover you bought the wrong things.


Will there be an inverter?
What DC voltage are you thinking?
Do you have a preliminary drawing of the system you are considering?

Thank you again!

Please see attached drawing, sorry for the horrible handwriting
I am open to consider any suitable DC voltage that supports the goal.
I hope the sketch is clear enough.

This emergency backup system would not be connected to the home electrical system at all.
The gas furnace power supply would be completely disconnected from the home electrical system before switched over to the backup power.
Something similar to this solution, in terms of separating the furnace from the household electrical power:

 

[tigerwillow1]

I will ask Honda about the power factor and efficiency.

These are attributes of the charger, not the generator. Not a Honda question. As far as I know, chargers with PF correction are still fairly rare. Xantrex makes some chargers and inverter/chargers with PF correction, saying the "typical" PF is 0.98. In approximate numbers, using this instead of a 0.7 PF charger will let you get about 40% more DC output from the same generator when the generator is maxed out. I have a PF corrected inverter/charger and have witnessed the difference first-hand. If you don't need squeeze the maximum out of the generator, it doesn't matter a whole lot. An eu3000i will probably do just as well with a non-PF corrected charger as the 2200i will do with the PF corrected charger.

 

[FilterGuy]

Thank you again!

Please see attached drawing, sorry for the horrible handwriting
I am open to consider any suitable DC voltage that supports the goal.
I hope the sketch is clear enough.

This emergency backup system would not be connected to the home electrical system at all.
The gas furnace power supply would be completely disconnected from the home electrical system before switched over to the backup power.
Something similar to this solution, in terms of separating the furnace from the household electrical power:

Great start!!!

Now lets fill in some detail.

1. First and foremost: what is the power needs of the heating boiler? This is important for sizing both the inverter and battery correctly.
   • Are there pumps and or blowers involved? (We need to make sure we cover any possible surge currents.
   • Is there any 240V needs?
2. I am surprised it is only the heater. I understand that it is probably the most important thing for staying alive in a cold climate, but I would think there would be at least a few lights and other items.
3. How long do you want to be able to run the boiler on a full battery charge? This is important info for properly sizing the battery.

 

[Nick R.]

Great start!!!

Now lets fill in some detail.

1. First and foremost: what is the power needs of the heating boiler? This is important for sizing both the inverter and battery correctly.
   • Are there pumps and or blowers involved? (We need to make sure we cover any possible surge currents.
   • Is there any 240V needs?
2. I am surprised it is only the heater. I understand that it is probably the most important thing for staying alive in a cold climate, but I would think there would be at least a few lights and other items.
3. How long do you want to be able to run the boiler on a full battery charge? This is important info for properly sizing the battery.

Thank you again!

It is an Allied Air A95UH1E model, it uses blower, no pump, the unit is 120V, with a 15A fuse on the panel.
The manual is not helpful in terms of the total power consumption, a unit nameplate is supposed to display power consumption, mind you, nothing seems visible related to it on the outside of the furnace.

What's useful is, that the manual mentions this about generator use: control board requires proper polarity and proper grounding and the generator should have less than 5% THD, total harmonic distortion.

I discovered that there is also a humidifier installed on the furnace, with 120VAC, 7A sticker, mind you it is powered off completely.

Next week I can bring an AV meter and check how much Amps are drawn on the dedicated wire after the furnace switch when the unit starts up and when it is running.

There is no need for 240V. Because there is no transfer switch involved, the cook stove operates with natural gas. Temporary lighting is easy enough with some portable, rechargeable LED lights which are on stand-by anyway, without messing with bringing in external power cords from the generator. The main concern is not to freeze, which can be a real danger in -20C, which is not rare.

Ideally the battery would last from 8-9 PM to 7 AM, for noise consideration to neighbors. It can be somewhat shorter, it's OK if the furnace doesn't run continuously, as long as it can maintain at least 17-18C.

Thank you very much again!

 

[Nick R.]

These are attributes of the charger, not the generator. Not a Honda question. As far as I know, chargers with PF correction are still fairly rare. Xantrex makes some chargers and inverter/chargers with PF correction, saying the "typical" PF is 0.98. In approximate numbers, using this instead of a 0.7 PF charger will let you get about 40% more DC output from the same generator when the generator is maxed out. I have a PF corrected inverter/charger and have witnessed the difference first-hand. If you don't need squeeze the maximum out of the generator, it doesn't matter a whole lot. An eu3000i will probably do just as well with a non-PF corrected charger as the 2200i will do with the PF corrected charger.

Thank you! I don't really need to squeeze the max out of the generator, the idea is to pick up the access power that is generated anyway beyond what's needed for the furnace, and use it to charge a battery, potentially reduce the usage of the generator (especially during at night) with the extra layer of power.

 

[FilterGuy]

It is an Allied Air A95UH1E model, it uses blower, no pump, the unit is 120V, with a 15A fuse on the panel.

That gives us some good info.

* Blowers have a start surge, but the surge is not near as large as a pump.
* 120V means you have a very wide selection of inverters available to you.
* With a 15A fuse, we know the max continuous power draw is only 1800W. I would be willing to bet it is less than 1500W. This means the inverter can be relatively small. (More on this later)

What's useful is, that the manual mentions this about generator use: control board requires proper polarity and proper grounding and the generator should have less than 5% THD, total harmonic distortion.

This tells us we need a pure sine wave inverter.


Is the attached the correct manual?

Starting on page 50 of the manual there are charts for wattage used by the blower for various sub-models of the A95UH1E. Do you know what sub-model it is? Some of the models only need less than 400 watts. Others need up to 800 watts. Overall, this is reasonably small, but we need to try to narrow this down in order to understand the potential start-surge current. (If it only takes 400W, a 1000W inverter would probably work, but I would recommend a larger inverter if it is 800W)

The next thing we need to understand is the duty cycle of the system. The heater will turn on and off to keep the temp constant. If it is on 90% of the time, the system will need more storage than if it is on 20% of the time.

 

[GooseF16]

I had a 120v heater and what I did to keep it simple as I learned is so simple its stupid..
I bought 2 Honda 2000's, 2x50 ft cords and 2 power strips.. and during power outages, I physically unplugged each unit I wanted to move.. fridges, lamps, fans, and used one dedicated to run the heat blower and electronic control.. I knew I didn't know enough about a home system yet, and that was good advice from a friend.. right now I have a delta pro and the gas generator that does the same... sometimes you already have the tools you need, with a little mods.. food for thought.. I got a boat tank gas lid mod for the Hondas.. and I still have them 15 yrs later.. when in doubt or something doesn't work, I just plop em on the front walk and fire em up with a box of cords.. good luck.. there is alot of smart folks on here that will help.. I really like this group.

 

[Nick R.]

That gives us some good info.

* Blowers have a start surge, but the surge is not near as large as a pump.
* 120V means you have a very wide selection of inverters available to you.
* With a 15A fuse, we know the max continuous power draw is only 1800W. I would be willing to bet it is less than 1500W. This means the inverter can be relatively small. (More on this later)

This tells us we need a pure sine wave inverter.


Is the attached the correct manual?

Starting on page 50 of the manual there are charts for wattage used by the blower for various sub-models of the A95UH1E. Do you know what sub-model it is? Some of the models only need less than 400 watts. Others need up to 800 watts. Overall, this is reasonably small, but we need to try to narrow this down in order to understand the potential start-surge current. (If it only takes 400W, a 1000W inverter would probably work, but I would recommend a larger inverter if it is 800W)

The next thing we need to understand is the duty cycle of the system. The heater will turn on and off to keep the temp constant. If it is on 90% of the time, the system will need more storage than if it is on 20% of the time.

Yes, this is exactly the manual.

It looks like the sub-model is the A95UH1E070B12S-05.

I wouldn't mind the larger inverter anyway, demands tend to grow only
I would also consider the larger duty time, since we have no winter experience with this house and furnace. In my house on the coldest days it's pretty much closer to 90% than 20%. This winter was so far fairly mild, so it doesn't mean much that right now it is turned off considerably more often than on.

Thank you again!