Opinions on UST 30 & 60 day lanterns for power outage use, please.

[broadgage]

1200 lumens for 41 hours sounds very optimistic to me.
At 120 lumens per watt, 1200 lumens requires 10 watts.
8 D cells in series will produce about 10 volts on load.
10 watts at 10 volts is one amp.
I would not expect alkaline cells to produce an amp for 10 hours, let alone for 41 hours.
Alkaline D cells are typically about 18 AH, on slow discharge, much less if discharged quickly.

 

[mickeyfinn]

1200 lumens for 41 hours sounds very optimistic to me.
At 120 lumens per watt, 1200 lumens requires 10 watts.
8 D cells in series will produce about 10 volts on load.
10 watts at 10 volts is one amp.
I would not expect alkaline cells to produce an amp for 10 hours, let alone for 41 hours.
Alkaline D cells are typically about 18 AH, on slow discharge, much less if discharged quickly.

broad,

I don't have the knowledge to agree or disagree with your postulation.

But my first question is, and it's an honest one since I don't know the answer, do all bulbs burn power at the same rate?

Send me eight decent D cells or Paypal me enough $ to buy some and I'll happily test the lantern for you and give you an honest, detailed accounting.

I think it will start out fine at 1200 lumen, and by 41 hours the output will be noticeably less, but still plenty bright.

Remember, it did a straight 108 hours (4.5 days) on medium then another almost seven hours on high, which was REALLY bright, before I shut it down.

 

[broadgage]

As regards the question "do all bulbs burn power at the same rate" The simple answer is that LEDs in particular can have the rate of power use altered or adjusted, but there limits as to the efficiency of an LED. To produce 1,200 lumens must take ABOUT 10 watts, presuming 120 lumens per watt. I do not know the actual efficiency of the LEDs used in this lantern, but 120 lumens per watt seems a reasonable upper estimate, including driver losses.

Alkaline D cells do have a capacity of about 18AH on slow discharge (published data)
8 such cells in series will average ABOUT 10 volts in total during discharge, measured by myself and many others.
Alkaline D cells can supply 0.8amps for about 12 to 14 hours, published data by maglight and others, they claim a 12 to 14 run time with 0.8 amp bulbs and alkaline D cells.

I claim no great precision in my calculations, but am satisfied that 8 D cells simply can not produce 1200 lumens for 41 hours.
10 hours would seem the likely limit, possibly 12 hours under ideal conditions. 41 hours no way.

The lantern may well stay lit for 41 hours, but not at 1200 lumens.

 

[Bdm82]

As regards the question "do all bulbs burn power at the same rate" The simple answer is that LEDs in particular can have the rate of power use altered or adjusted, but there limits as to the efficiency of an LED. To produce 1,200 lumens must take ABOUT 10 watts, presuming 120 lumens per watt. I do not know the actual efficiency of the LEDs used in this lantern, but 120 lumens per watt seems a reasonable upper estimate, including driver losses.

Alkaline D cells do have a capacity of about 18AH on slow discharge (published data)
8 such cells in series will average ABOUT 10 volts in total during discharge, measured by myself and many others.
Alkaline D cells can supply 0.8amps for about 12 to 14 hours, published data by maglight and others, they claim a 12 to 14 run time with 0.8 amp bulbs and alkaline D cells.

I claim no great precision in my calculations, but am satisfied that 8 D cells simply can not produce 1200 lumens for 41 hours.
10 hours would seem the likely limit, possibly 12 hours under ideal conditions. 41 hours no way.

The lantern may well stay lit for 41 hours, but not at 1200 lumens.

You're 100% right that 1200 lumens for 41 hours isn't happening.

But runtimes are always rated to the ANSI FL1 standard of 10%.

So the question is... could it be producing 120 lumens at hour 41? If it is, it gets to say 41 HR runtime. (Though many on here consider 50% output the REAL runtime for their use.)

Whether it could do 120 at hr 41 all depends on the output curve. If it is outputting 1150 at hour 8, then we know it'd be a "no" do to the battery capacity limitations as you shared. But if it is already down to 125 lumens at hour 2, then enough battery power might be held back to make it to 41 hours. I doubt it actually follows either of these curves, but I don't have one to test (nor the will to chew through 8 bricks, no, I mean D cell batteries).

But hey, at the end of the day, it's all a bit moot. OP has what he's looking for and is happy with it, so good enough for me.

 

[mickeyfinn]

I claim no great precision in my calculations, but am satisfied that 8 D cells simply can not produce 1200 lumens for 41 hours.
10 hours would seem the likely limit, possibly 12 hours under ideal conditions. 41 hours no way.

The lantern may well stay lit for 41 hours, but not at 1200 lumens.

broad,

Did you perhaps miss the part earlier where I said:

I think it will start out fine at 1200 lumen, and by 41 hours the output will be noticeably less, but still plenty bright.

Remember, it did a straight 108 hours (4.5 days) on medium then another almost seven hours on high, which was REALLY bright, before I shut it down.

And Bdm82,

I don't have one to test (nor the will to chew through 8 bricks, no, I mean D cell batteries).

But hey, at the end of the day, it's all a bit moot. OP has what he's looking for and is happy with it, so good enough for me.

Those bricks, er, I mean batteries are useful for other things besides poweing lanterns during a hurricane.

For instance, you could use 8 Ds to weigh down one of those blue tarps covering a roof after the hurricane.

And you could use a mere three of them to repel looters during lengthy power outages.

Man, put three of those fat babies in an athletic sock and swing away with it and you can do some damage.

Put two each in your front pockets and you could easily walk through 150 mph winds without being blown away.

Yep, them Ds are something.

Take care