DC Generator instead of AC Inverter type?

**Mike90250** · 09-09-2020, 01:59 AM

Those look fine, but make sure they will supply the 58-65VDC batteries need under varying conditions. If they are "48v power supplies" that won't work well when a 48V bank needs 58V for charging. Do they have a charge regulator, or how do you adjust the voltage/amps ? Engine Speed ?

**Bala** · 09-09-2020, 07:16 PM

They are essentially an automotive alternator bolted to a honda engine, I have used a few over time and did set up similar for charging Traffic lights for road works, before solar and lithium.

The ones I used for the lights had a standard internal regulator, I had fitted an external adjustable regulator so I could set it 15v rather than the standard 13.8 to charge faster.

Big difference between your Yamaha inverter genset and the GX honda engine will be fuel consumption and noise. The inverter will throttle back engine RPM as load decreases the GX honda will run a a preset RPM.

The honda in petrol form is easy to work on and maintain. I have not worked on LPG Honda engines for a very long time so cant comment.

The alternator itself will be reliable and any auto electrician can repair or replace it.

**ron_jeremy** · 09-09-2020, 08:42 PM

Thx for the input. Our Yamaha inverter generator does not throttle, and runs at constant rpm no matter what load it sees. My interest in the DC units is charging amps: our 4kW Yamaha can output a max of 30A but the little DC Honda G3 24V model can output 80A -- a huge difference. I'd need a 12kW inverter genset to get the same amps.

**Bala** · 09-09-2020, 10:07 PM

The model you are looking at has a Honda GX200 engine, that engine started as a GX140 and they increased bore and stroke over the last 30+ years to increase horsepower. I have worked on most stationary engine and these are my favorite for reliability. I own a few. With frequent oil changes and a valve clearance check every now and then it will last a long time.

They list its run time at approx 4hrs, so that is approx 3 litres, or more of fuel in 4 hrs. They have a gravity feed fuel system so you can easily fit a larger extra fuel tank.

**extrafu** · 09-10-2020, 08:45 AM

Originally posted by ron_jeremy

Thx for the input. Our Yamaha inverter generator does not throttle, and runs at constant rpm no matter what load it sees. My interest in the DC units is charging amps: our 4kW Yamaha can output a max of 30A but the little DC Honda G3 24V model can output 80A -- a huge difference. I'd need a 12kW inverter genset to get the same amps.

I think you're confusing AC and DC output here. Your Yamaha outputs 30A *AC* at 120V. If you had a bigger inverter with a charger, you could take that 30A/120V AC input in and convert it to DC 24V at ~150A to charge your batteries. From what I see of the Trace documentation, yours should be able to charge at 120A which is likely OK for you.

**ron_jeremy** · 09-22-2020, 02:31 PM

Originally posted by extrafu

I think you're confusing AC and DC output here. Your Yamaha outputs 30A *AC* at 120V. If you had a bigger inverter with a charger, you could take that 30A/120V AC input in and convert it to DC 24V at ~150A to charge your batteries. From what I see of the Trace documentation, yours should be able to charge at 120A which is likely OK for you.

Hi @extrafu thanks for the input. Howver, I'm really struggling to wrap my head around DC amps vs AC amps. Isn't a 100A incoming charge from an AC generator the same as a 100A charge from a DC generator? Aren't all amps the same when it comes to charging the battery bank? I mean, "amps is amps", isn't it. or am I totally missing something here?

Are you saying my inverter is taking my generator's ~33.33A AC (4000W/120V*1000) and is then turning that into a 167A DC charge to the batteries (4000/24*1000)?

**SunEagle** · 09-22-2020, 03:04 PM

Originally posted by ron_jeremy

Hi @extrafu thanks for the input. Howver, I'm really struggling to wrap my head around DC amps vs AC amps. Isn't a 100A incoming charge from an AC generator the same as a 100A charge from a DC generator? Aren't all amps the same when it comes to charging the battery bank? I mean, "amps is amps", isn't it. or am I totally missing something here?

Are you saying my inverter is taking my generator's ~33.33A AC (4000W/120V*1000) and is then turning that into a 167A DC charge to the batteries (4000/24*1000)?

Actually "amps is not always amps". When you use AC amps to charge a DC load there usually is some type of loss due to converting through a piece of equipment from one voltage to another.

**extrafu** · 09-22-2020, 05:50 PM

Originally posted by ron_jeremy

Hi @extrafu thanks for the input. Howver, I'm really struggling to wrap my head around DC amps vs AC amps. Isn't a 100A incoming charge from an AC generator the same as a 100A charge from a DC generator? Aren't all amps the same when it comes to charging the battery bank? I mean, "amps is amps", isn't it. or am I totally missing something here?

Are you saying my inverter is taking my generator's ~33.33A AC (4000W/120V*1000) and is then turning that into a 167A DC charge to the batteries (4000/24*1000)?

Stop thinking about amps, think about power. As @SunEagle said, you won't get 167A of DC power because of losses during conversion. But you'll definitively get a lot more than 33A. For example, my Kohler 14RESA runs at 240V and maxes out at 60A. But during the bulk charge cycle of my batteries, I'm pumping in them 130A @ 60V through my XW6848.

**ron_jeremy** · 09-22-2020, 07:47 PM

Originally posted by extrafu

Stop thinking about amps, think about power. As @SunEagle said, you won't get 167A of DC power because of losses during conversion. But you'll definitively get a lot more than 33A. For example, my Kohler 14RESA runs at 240V and maxes out at 60A. But during the bulk charge cycle of my batteries, I'm pumping in them 130A @ 60V through my XW6848.

Oh man, ok. I guess I was thinking about amps because battery chargers are rated in amps (example, 120V/2A, 120V/6A, etc.). Maybe that's strictly related to AC charging?

Anyway, is my math correct? That is, does a 4kW 120V generator (rated at 33A AC continuous) actually put a charge of 135A @ 29.7V into the 24V/960AH battery bank (less losses for cable, inverter, heat, etc.)? Or am I off base here, too?

**extrafu** · 09-23-2020, 05:57 PM

Yes your math is ok.

**Mike90250** · 09-24-2020, 01:17 AM

The math is right . And at that point I say, your DC amps are too high to manage properly, and you should move to a 48V half the amps system. cables and connectors that can handle 130A for 2 hours without thermal issues, are going to be expensive.

24V 1000ah
is the same storage as a
48V 500ah but only half the amps to deal with 67A.

**ron_jeremy** · 09-25-2020, 02:28 PM

Thank you very much for all the help.

This is an inherited system and yes, 48V is on our roadmap but only if we keep the house because it will likely entail scrapping everything & starting fresh (we need new solar panels anyways).

Also, my AC amps vs DC amps confusion led me to believe the generator was undersized to charge the battery bank. Good to know it's ok for the job.

By the way, the copper cable going from the inverter to the battery bank is labeled 4/0 AWG. Is it sized correctly?

**Mike90250** · 09-25-2020, 03:54 PM

Originally posted by ron_jeremy

.......

By the way, the copper cable going from the inverter to the battery bank is labeled 4/0 AWG. Is it sized correctly?

Should be ok, if the charger in the inverter is only doing 60A

I wanted to mention also, the Power Factor / efficiency of the charger is also important. Many inverter/chargers have a .93 PF which is way better than the typical .6 of most automotive chargers, if you run them off a generator, lower PF requires a larger generator

**PNW_Steve** · 09-25-2020, 07:15 PM

Originally posted by ron_jeremy

We live off grid & have a small PV array, Trace SW4024 inverter, 60A MPPT charger, 24V battery bank (12 x 2V), & a Yamaha EF4400iS inverter type generator. I noticed these DC generators can offer much more amps (for a given size) to charge the batteries:

https://www.altendc.com/g3-gasoline-battery-charging-dc-generator

Is this type of genset compatible with an off grid system?

Where are you?
I have a Yanmar Diesel 2.4kw 24 volt DC generator that I bought for a project and wound up not using. Come take a look.

DC Generator instead of AC Inverter type?

DC Generator instead of AC Inverter type?

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment