How much ac power does a dc charger draw? (Math)

[Nan_wpg]

Its still a chemical reaction, its not magic.
You can fast charge a lithium and use it straight away, you just will not have full rated battery capacity.
Its like the foam on your beer.
Pour it very fast you get less beer and more foam.
If you want a FULL glass, fill it very slowly.

I don’t understand. Lithium has no absorbtion (push power into battery via higher voltage).

la bulk charges and then absorbs for a long time. Lithium needs this too? (To a lesser degree?)

 

[Nan_wpg]

It will be >2048W, unless it is 100% efficiency which there is no such charger, so at 90% it will be 2275W. I would not load the Generator at full spec, I would do 80 ~ 85%.
I do not see the 40A charger in your link.

Honda generators. Always.

 

[Nan_wpg]

So, keep it simple. The charger should tell you it's maximum input wattage. Use that. Your factoring above for charger sizing is correct but the manufacturer has already done the efficiency calculation and will list it's max a/c draw for you.

Ok,

You don't want to load a honda 2200 to 2000 watts for any length of time. Yes, it can handle it but it's going to be screaming away at 4000 RPM driving you nuts.

Get the 3000euis if you forsee a 2000 watt draw for any length of time.

Was thinking of the 3000 Honda. Our 2000 is 15 years old and starting to burn some oil. It doesn’t owe us a dime. 7000 seems overkill.

I could skip the eu versions and just get the standard Honda generator. Cheaper and/or more power for sane money as eu. Not as quiet. It won’t be running as much as the eu does.

 

[Nan_wpg]

It will be >2048W, unless it is 100% efficiency which there is no such charger, so at 90% it will be 2275W. I would not load the Generator at full spec, I would do 80 ~ 85%.
I do not see the 40A charger in your link.

There’s isn’t a 40a charger In the link. If I buy 2 chargers to speed things up I just doubled the calculation

 

[Checkthisout]

Was thinking of the 3000 Honda. Our 2000 is 15 years old and starting to burn some oil. It doesn’t owe us a dime. 7000 seems overkill.

I could skip the eu versions and just get the standard Honda generator. Cheaper and/or more power for sane money as eu. Not as quiet. It won’t be running as much as the eu does.

Correct. You could save some cashola going with a standard non-invertor but honestly, the inverter gens, especially the Honda 3k are soooooo.....nice and reliable and quiet. They cost around the same as a 5500 open frame.

Do you want electric start? If not, Honda makes a 2800 open frame inverter.

 

[Nan_wpg]

So, keep it simple. The charger should tell you it's maximum input wattage. Use that. Your factoring above for charger sizing is correct but the manufacturer has already done the efficiency calculation and will list it's max a/c draw for you.

Ok,

You don't want to load a honda 2200 to 2000 watts for any length of time. Yes, it can handle it but it's going to be screaming away at 4000 RPM driving you nuts.

Get the 3000euis if you forsee a 2000 watt draw for any length of time. The nice thing about lithium is you can get the supermajority of charge and maintain a higher generator load for the duration of the charge rather than a large inrush and then the long, boring absorption time you get with LA.

How often do you foresee having to use a generator to rebulk the batteries?

we currently use the Honda 2000 at our cabin every night. It runs the Tv, lights, charges phones, and my Powerpack to run my cpap overnight.

seems like overkill (plus it’s loud) and we have to haul fuel for the genny (boat access so less I have to carry the better).

my thought process is to have a solar setup and genny/charger for backup only. BUT…….

there are some bizzare family Dynamics (it’s a shared family cabin) in that some people come out and contribute nothing and yet use everything.
im coming to the cabin on a trial basis. I want things at the cabin to make it “nicer” I.e Solar but I also want simple and easily removable if I need to bail.

so for the time being I’d like to run the genny less. We start the week with a fully charged 48v rack battery. It should power us for 3-5 days. When needed, run the genny and charger.

instaed of genny every day, it’s every few days.

if things work out I can look at a full blown solar system.

 

[Bud Martin]

It will be a good idea to get charger that you can adjust the charging current.

 

[Nan_wpg]

Correct. You could save some cashola going with a standard non-invertor but honestly, the inverter gens, especially the Honda 3k are soooooo.....nice and reliable and quiet. They cost around the same as a 5500 open frame.

Do you want electric start? If not, Honda makes a 2800 open frame inverter.

You don’t have to tell me how nice the eu’s are. They are fantastic. Electric start is not needed. It’s nice but not a deciding factor.
i don’t understand what makes the eu an “inverter” when the open frames also have “plugs” to plug things into.

is the power “better”?

 

[Nan_wpg]

It will be a good idea to get charger that you can adjust the charging current.

Then I’m looking at an inverter/charger. I want simple and dumb proof.

 

[RCinFLA]

Big factor on required generator size is power factor of charger. Cheaper chargers have power factor of 0.60-0.65 due to simple rectifier-filter for AC input to DC conversion. They draw their power in short high current peaks of sinewave. Power factor corrected charger has PF greater than 0.90 and draws current in a near sinewave shape across whole AC cycle.

Generators, inverters, and transformers are really rated for VA, not watts. Power factor is watts/VA.

Say your battery charging is consuming 2000 watts of DC power and charger has 85% conversion efficiency.

A charger with 0.65 power factor requires a generator of 2000watts/ 0.85 efficiency / 0.65 power factor = 3620 VA generator.
A charger with 0.90 power factor requires a generator of 2000watts/ 0.85 efficiency / 0.90 power factor = 2614 VA generator.

Power factor corrected chargers are a bit more expensive. If charger does not specify its power factor then it likely does not have power factor correction.

Most hybrid inverter/chargers have a good AC charging power factor.

 

[Nan_wpg]

Big factor on required generator size is power factor of charger. Cheaper chargers have power factor of 0.60-0.65 due to simple rectifier-filter for AC input to DC conversion. They draw their power in short high current peaks of sinewave. Power factor corrected charger has PF greater than 0.90 and draws current in a near sinewave shape across whole AC cycle.

Generators, inverters, and transformers are really rated for VA, not watts. Power factor is watts/VA.

Say your battery charging is consuming 2000 watts of DC power and charger has 85% conversion efficiency.

A charger with 0.65 power factor requires a generator of 2000watts/ 0.85 efficiency / 0.65 power factor = 3620 VA generator.
A charger with 0.90 power factor requires a generator of 2000watts/ 0.85 efficiency / 0.90 power factor = 2614 VA generator.

Power factor corrected chargers are a bit more expensive. If charger does not specify its power factor then it likely does not have power factor correction.

Most hybrid inverter/chargers have a good AC charging power factor.

So it’s more than the “efficiency“ of the charger?

is there an idiot proof (me) quick rule of thumb?

 

[Checkthisout]

You don’t have to tell me how nice the eu’s are. They are fantastic. Electric start is not needed. It’s nice but not a deciding factor.
i don’t understand what makes the eu an “inverter” when the open frames also have “plugs” to plug things into.

is the power “better”?

The engine rotates an alternator that generators DC power which is then passed through an inverter to make AC. The Hz is produced by the inverter in the generator so the engine speed can be varied based on load.

VS

Regular generator which makes ac power based on rotation of........well lets see here.

Regular small gen must run at 3600 RPM to produce 60HZ so when it's not close to full load, it's very inefficient.

 

[Checkthisout]

So it’s more than the “efficiency“ of the charger?

is there an idiot proof (me) quick rule of thumb?

Yes. Look at the manfacturers specs for the charger

 

[Nan_wpg]

The charger I linked does not specify a power factor, just efficiency.

 

[Nan_wpg]

Correct. You could save some cashola going with a standard non-invertor but honestly, the inverter gens, especially the Honda 3k are soooooo.....nice and reliable and quiet. They cost around the same as a 5500 open frame.

Do you want electric start? If not, Honda makes a 2800 open frame inverter.

Just checking out the new 3200i on Hondas website. very tempting.

 

[Warpspeed]

I don’t understand. Lithium has no absorbtion (push power into battery via higher voltage).

la bulk charges and then absorbs for a long time. Lithium needs this too? (To a lesser degree?)

If you think your charging current will drop from 40 amps to zero in like one second, you might be surprised.
It comes down fairly quickly, but the battery is still absorbing amp hours during the time the current is falling.

 

[RCinFLA]

The charger I linked does not specify a power factor, just efficiency.

Since residential grid power does not charge for poor power factor their efficiency number does not include effects of higher peak current of poor power factor.

But for inverters, transformers, and generators their loses is proportional to peak current so it matters to these devices.

 

[Nan_wpg]

Big factor on required generator size is power factor of charger. Cheaper chargers have power factor of 0.60-0.65 due to simple rectifier-filter for AC input to DC conversion. They draw their power in short high current peaks of sinewave. Power factor corrected charger has PF greater than 0.90 and draws current in a near sinewave shape across whole AC cycle.

Generators, inverters, and transformers are really rated for VA, not watts. Power factor is watts/VA.

Say your battery charging is consuming 2000 watts of DC power and charger has 85% conversion efficiency.

A charger with 0.65 power factor requires a generator of 2000watts/ 0.85 efficiency / 0.65 power factor = 3620 VA generator.
A charger with 0.90 power factor requires a generator of 2000watts/ 0.85 efficiency / 0.90 power factor = 2614 VA generator.

Power factor corrected chargers are a bit more expensive. If charger does not specify its power factor then it likely does not have power factor correction.

Most hybrid inverter/chargers have a good AC charging power factor.

View attachment 128004

Just looking at the samlex 49v evo inverter charger, it has an ac input power factor of >.95. That’s really good

 

[Checkthisout]

The charger I linked does not specify a power factor, just efficiency.

All you need to know for gen sizing is the input wattage. The manufacturer will tell you what that is.

 

[Nan_wpg]

If you think your charging current will drop from 40 amps to zero in like one second, you might be surprised.
It comes down fairly quickly, but the battery is still absorbing amp hours during the time the current is falling.

I d-nt think anything. In fact I know nothing about lifepo4.

I thought the,current,stayed the same up until they are fully charged. Voltage is also,high all the,way to the top and then drops to,float.

current only,drops down for la battery?? Or am I wrong?