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Powermax Charger Efficiency

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gabe1475

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Does anyone have experience with the efficiency rating on a Powermax Charger/Converter? Want to make sure I pair with a generator that will not feel overtaxed and would prefer to run at about 60% load given that I will probably be running for a couple hours at a time.

Looking at the propane powered AI Power Generator rated at 1500w. Was initially thinking the 55am charger, but with efficiency losses pointed out by another member on this forum will that be running at the close to the max ratings?

Does anyone have any feedback on what they have seen with these units as far are actual AC draw vs charge? Does not have to be the 55 amp model.
 
The specs for the 24v is 85% or better efficiency. I can't imagine the 12v is any lower.

The specs for the 55a charger says its max output is 780 watts.

So if my math is correct to figure out what you are asking?

1500w x .85 (85% efficciency) = 1275w (100% load on generator)
1275w x .60 (60% load) = 765w
1275w x .612 (61.2% load) = 780

If the efficiency is higher than 85% the load should be lower than 61.2%.

However, generator wattage outputs drop at higher altitudes due to lower levels of oxygen. There are high-altitude kits for both gas and propane generators to help adjust for it. I've never used them, so I don't know how well they work. The point being that lower wattage output would mean higher load.

Why propane? They put out less power than gas generators. Propane can be harder to find. The only advantage I know of is that propane supposedly has an unlimited shelf life.
 
RogerD said:
The specs for the 24v is 85% or better efficiency. I can't imagine the 12v is any lower.

The specs for the 55a charger says its max output is 780 watts.

So if my math is correct to figure out what you are asking?

1500w x .85 (85% efficciency) = 1275w (100% load on generator)
1275w x .60 (60% load) = 765w
1275w x .612 (61.2% load) = 780

If the efficiency is higher than 85% the load should be lower than 61.2%.

However, generator wattage outputs drop at higher altitudes due to lower levels of oxygen. There are high-altitude kits for both gas and propane generators to help adjust for it. I've never used them, so I don't know how well they work. The point being that lower wattage output would mean higher load.

Why propane? They put out less power than gas generators. Propane can be harder to find. The only advantage I know of is that propane supposedly has an unlimited shelf life.
Click to expand...
I guess the way I would look at it is as follows, keep in mind I am new to this so perhaps not looking at this correctly. Since only using as a charger and there would be no other draw calculating at 55amps / 13.5v. Also assuming specs per manufacturer are correct, one of the pieces I was hoping for feedback on.

55amps @ 13.5v = 743w
743/.85 = 874w

Next piece would how much loss is there between what the generator puts out vs the actual usage of the converter. Have never had a generator, so no real world experience in this. If loss is minimal, 874w on a 1500w generator seems to be in that 60% load range that I am aiming for.

As far as why we are prefer propane, we are already carrying propane on our trailer, one less thing to worry about bringing along. We do have the option of using gas since the generator is dual fuel, but would only use that if we ran out of propane and did not have an option to refill the tanks.
 
gabe1475 said:
Was initially thinking the 55am charger, but with efficiency losses pointed out by another member on this forum will that be running at the close to the max ratings?
Click to expand...
If its me that you reference, my main objection was not the efficiency.
The unit pulled > 15 amps through a plug and cord that are rated for 15 amps.
A continuous use appliance should not pull more that ~12 amps from a 15 amp rated plug and cord.

The 50amp@24volt power max uses a 15 amp plug.
Competing products by progressive dynamics and iota rated 40amp@24 volt use a 20 amp plug.
 
Last edited:
smoothJoey said:
If its me that you reference, my main objection was not the efficiency.
The unit pulled > 15 amps through a plug and cord that are rated for 15 amps.
A continuous use appliance should not pull more that ~12 amps from a 15 amp rated plug and cord.
Click to expand...
Was actually referencing a post by time2roll who posted on my thread in coming up with a backup option for our solar panels:

diysolarforum.com

Best Backup Option for Charging Batteries

Interested in finding out what the consensus is on a backup option for charging Lithium batteries when solar is not performing/in shaded area: Options I am considering: - DC-DC charger off TV, this would be while the Truck is idle. If we are driving, not really an issue as the solar panels...
diysolarforum.com diysolarforum.com

I did see you post as well and agree that if it is pulling well over the specs per the manufacturers sheets, something is off with the unit.
 
smoothJoey said:
If its me that you reference, my main objection was not the efficiency.
The unit pulled > 15 amps through a plug and cord that are rated for 15 amps.
A continuous use appliance should not pull more that ~12 amps from a 15 amp rated plug and cord.
Click to expand...
Don't you have the 24v / 50 amp?

That's the one I've been looking at buying.

The specs on it says 14a. Which would make sense based on the efficiency / max output it would pull around 1700 watts.

Which should be a 12 gauge cord - yes?
 
RogerD said:
Don't you have the 24v / 50 amp?
Click to expand...
Yes
RogerD said:
That's the one I've been looking at buying.

The specs on it says 14a. Which would make sense based on the efficiency / max output it would pull around 1700 watts.
Click to expand...
The specs do not match my test results.
RogerD said:
Which should be a 12 gauge cord - yes?
Click to expand...
The Powermax has a 14 awg nema 5-15p.
The competitors have nema 5-20p.
 
Last edited:
gabe1475 said:
I guess the way I would look at it is as follows, keep in mind I am new to this so perhaps not looking at this correctly. Since only using as a charger and there would be no other draw calculating at 55amps / 13.5v. Also assuming specs per manufacturer are correct, one of the pieces I was hoping for feedback on.

55amps @ 13.5v = 743w
743/.85 = 874w

Next piece would how much loss is there between what the generator puts out vs the actual usage of the converter. Have never had a generator, so no real world experience in this. If loss is minimal, 874w on a 1500w generator seems to be in that 60% load range that I am aiming for.

As far as why we are prefer propane, we are already carrying propane on our trailer, one less thing to worry about bringing along. We do have the option of using gas since the generator is dual fuel, but would only use that if we ran out of propane and did not have an option to refill the tanks.
Click to expand...
Propane gennys are thirsty. The reason why is less energy storage per kw compared to gasoline.
 
Zwy said:
Propane gennys are thirsty. The reason why is less energy storage per kw compared to gasoline.
Click to expand...
Agree, but not planning on using on a regular basis. If I could, would avoid even firing up, at this point don't have a benchmark for what I can expect for solar generation in a shaded location. If I squeeze 20AH out of my panels in a day, I may not even need this option.
 
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gabe1475 said:
Agree, but not planning on using on a regular basis. If I could, would avoid even firing up, at this point don't have a benchmark for what I can expect for solar generation in a shaded location. If I squeeze 20AH out of my panels in a day, I may not even need this option.
Click to expand...
Sounds like you have a good plan. Nothing worse than having dead batteries in the middle of nowhere.
 
RogerD said:
That sucks. What others have you looked at?

I know the AIMS con120ac1224dc 12/24 75/37.5 is supposed to be good and like $230.
Click to expand...
I looked at the aims but the tail current is low.
I also looked at
www.donrowe.com

DonRowe.com: KISAE AC2430 Abso Charger 30A 24V Battery Charger

KISAE AC2430 Abso Battery Charger is a 24 Volt, 30 Amp power factor corrected charger designed for marine and commercial applications worldwide.
www.donrowe.com
Same problem with low tail current.
I have a base load of ~10 amps so the charge would never terminate.
I've got one of these coming.
www.donrowe.com

IOTA DLS-27-25, 24 Volt, 25 Amp Converter/Charger | DonRowe.com

The IOTA DLS-27-25 converts 24 volts AC to 27.2 volts DC for both DC load operation and 24 volt battery charging up to 25 amps. UL Listed.
www.donrowe.com
The Iota is UL listed.
@HRTKD has an Iota and I think he is satisfied.
 
smoothJoey said:
I looked at the aims but the tail current is low.
I also looked at
www.donrowe.com

DonRowe.com: KISAE AC2430 Abso Charger 30A 24V Battery Charger

KISAE AC2430 Abso Battery Charger is a 24 Volt, 30 Amp power factor corrected charger designed for marine and commercial applications worldwide.
www.donrowe.com
Same problem with low tail current.
I have a base load of ~10 amps so the charge would never terminate.
I've got one of these coming.
www.donrowe.com

IOTA DLS-27-25, 24 Volt, 25 Amp Converter/Charger | DonRowe.com

The IOTA DLS-27-25 converts 24 volts AC to 27.2 volts DC for both DC load operation and 24 volt battery charging up to 25 amps. UL Listed.
www.donrowe.com
The Iota is UL listed.
@HRTKD has an Iota and I think he is satisfied.
Click to expand...

I was looking at the Iota DLS-27-25-X

Specs say its output is 750w and efficiency is >80%. Based on this I would assume that the AC input watts would be around 940w or less.

However, it says its max AC amps is 12.2 at 108v, which is 1317 watts. If it actually pulled 1317w and put out 750w. The efficiency would only be like 57%.

The specs are all the same for the Iota DLS-27-25 but says its output is 650 watts VS 750 for the 25-X

How is 12.2 amps possible?
 
RogerD said:
How is 12.2 amps possible?
Click to expand...
Power factor.

Power factor - Wikipedia

en.wikipedia.org en.wikipedia.org

I got my Iota yesterday.
Way better than the powermax.
I originally had the 30 amp powermax and it could only deliver ~25 amps.
The Iota is rated for 25 amps and delivers ~27.
The fan is proportional and really quiet.
The powermax fan is not proportional and howls like a banshee.
 
smoothJoey said:
Power factor.

Power factor - Wikipedia

en.wikipedia.org en.wikipedia.org

I got my Iota yesterday.
Way better than the powermax.
I originally had the 30 amp powermax and it could only deliver ~25 amps.
The Iota is rated for 25 amps and delivers ~27.
The fan is proportional and really quiet.
The powermax fan is not proportional and howls like a banshee.
Click to expand...
How many AC watts (input) is it taking to run it?

Did you get the 25 or 25-X?
 
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