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Old 07-20-2019, 07:10 PM   #21
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True.
But not always available, best laid plans notwithstanding...

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Old 07-20-2019, 07:34 PM   #22
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Originally Posted by glenncooper View Post
I'm not a believer that you need the generator. Your winter experience might be a challenge, but if you really run the numbers and pay attention to your actual usage I'd just go for the solar with the smart battery combiner so that you can safely get some charge from your bus's alternator.
So you are, in fact, a believer in a generator, Glenn. Only in this case, the generator you're recommending is a diesel-guzzling behemoth with all the subtlety of a moose in heat

That's a lot of metal to move to run a battery charger.
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Old 07-20-2019, 08:39 PM   #23
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Semantics, if ya please! What you're describing is an AC producing alternator!Click image for larger version

Name:	bullwinkle-poetry-e1376926707342-375x375.jpeg
Views:	5
Size:	41.8 KB
ID:	35862
A generator, on the other hand
Makes the juice for a DC plan.
While not as subtle as a moose in heat,
Bullwinkle J. Moose just can't be beat.
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Old 07-20-2019, 09:39 PM   #24
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A generator can either be AC or DC.

However, I concede the point, if for no other reason than you introduced Bullwinkle into the mix.

A rocky-approved move, I must say!


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Old 07-27-2019, 10:59 PM   #25
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Not sure anyone mentioned this as I took a look at the suggestions.

Make sure you have you sit cells running through an appropriate rated voltage regulator. It will bump the voltage down and amperage up. It also stops charging when your batteries are full.

You might not be able to match your batteries if you add more later. The best thing to do is to buy 4 if you can. They will age together. You don't want to put old batteries with new batteries.

I saved some money by buying 4- 6v golf cart batteries. I think all together I have a big 12v 440ah battery. Sufficient for a couple of days off the grid with the family.
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Old 07-28-2019, 01:02 AM   #26
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Originally Posted by KevinDarcy11 View Post
Hey all!

Working on my solar (no clue what I'm doing lol) I have 2 100w mono panels from renogy and plan on adding 2 more. I am just about to buy 2 100ah sized batteries and also considering adding 2 more. My question is if you want to basically match the solar wattage to the ah. 2 100w panels 2 100ah batteries, 4 100w panels 4 100 ah batteries and so on. I have done my power audit and attached it, any help is really really appreciated as I am in way over my head hahah!

Thanks,

Kevin



What kind/size laptops do you have that only use 8 watts of juice. Granted, both of my 17 inch laptops are antiques, but they use around 200 watts. Have they gotten that much more efficient?
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Old 07-28-2019, 01:06 AM   #27
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Originally Posted by glenncooper View Post
I'm not a believer that you need the generator. Your winter experience might be a challenge, but if you really run the numbers and pay attention to your actual usage I'd just go for the solar with the smart battery combiner so that you can safely get some charge from your bus's alternator.



Why would you want to run a large engine just to run an alternator?


An inverter generator seems like good backup, even if you had shore power.
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Old 07-28-2019, 01:22 AM   #28
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Semantics, if ya please! What you're describing is an AC producing alternator!Attachment 35862
A generator, on the other hand
Makes the juice for a DC plan.
While not as subtle as a moose in heat,
Bullwinkle J. Moose just can't be beat.



Now write an ode
To the diode.


And your battery will think
Quick as a blink


That the alternator
Is a generator.
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Old 07-28-2019, 01:29 AM   #29
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Looking For Moose and Squirrel

.

My vote is for the little generator!
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Old 07-28-2019, 02:14 AM   #30
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What kind/size laptops do you have that only use 8 watts of juice. Granted, both of my 17 inch laptops are antiques, but they use around 200 watts. Have they gotten that much more efficient?

I highly doubt that unless they're like Alienware or MSI. Only high end gaming machines use larger 150+ watt supplies. Most laptop chargers are around 65W (that's their capacity, not what theyre actually outputting). Ultrabooks are usually 45Wl Surface style (basically a tablet with a keyboard) are around 10-15W.
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Old 07-28-2019, 02:54 AM   #31
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I highly doubt that unless they're like Alienware or MSI. Only high end gaming machines use larger 150+ watt supplies. Most laptop chargers are around 65W (that's their capacity, not what theyre actually outputting). Ultrabooks are usually 45Wl Surface style (basically a tablet with a keyboard) are around 10-15W.



My HP power supply says 120v x 1.7a input 18.5v x 3.6a output,

I believe that amounts to about 204 watts in and 65 watts out


The power supply wastes around 139 watts as heat (it is hot), but still the home batteries have to supply the whole 204 watts and this is what we have to account for in the math, correct?
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Old 07-28-2019, 06:37 AM   #32
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Bravo!
Quote:
Originally Posted by kidharris View Post
Now write an ode
To the diode.


And your battery will think
Quick as a blink


That the alternator
Is a generator.
Thanx for playing along! [emoji106]
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Old 07-28-2019, 01:29 PM   #33
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Originally Posted by kidharris View Post
My HP power supply says 120v x 1.7a input 18.5v x 3.6a output,

I believe that amounts to about 204 watts in and 65 watts out


The power supply wastes around 139 watts as heat (it is hot), but still the home batteries have to supply the whole 204 watts and this is what we have to account for in the math, correct?
They get hot but switch mode power supplies are still far more than 30% efficient. It is closer to 75%. Newer USB-C/PD chargers are up to 90%. A 65W brick is not consuming 204W.

First of all, laptop chargers are worldwide. They are designed to use 90-260V (100-240V +6/- 10%). The nameplate input current rating is at the lowest input voltage (which is found in Japan) and maximum output.

The laptop itself is hardly ever - if ever - going to draw the maximum that the supply can offer unless it is say, a replacement that was undersized. Figure about 20% less than max. For the most part, a laptop is going to draw about 50%. Taxing the processor while charging the batteries would kick it up to about 80%.

I have been using a cheap 100W inverter for my laptop for years, and it has a 75W brick (19vx3.95A).
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Old 07-28-2019, 06:19 PM   #34
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They get hot but switch mode power supplies are still far more than 30% efficient. It is closer to 75%. Newer USB-C/PD chargers are up to 90%. A 65W brick is not consuming 204W.

First of all, laptop chargers are worldwide. They are designed to use 90-260V (100-240V +6/- 10%). The nameplate input current rating is at the lowest input voltage (which is found in Japan) and maximum output.

The laptop itself is hardly ever - if ever - going to draw the maximum that the supply can offer unless it is say, a replacement that was undersized. Figure about 20% less than max. For the most part, a laptop is going to draw about 50%. Taxing the processor while charging the batteries would kick it up to about 80%.

I have been using a cheap 100W inverter for my laptop for years, and it has a 75W brick (19vx3.95A).



Sounds like I just might have found a justification for buying a new laptop.


How many real world watts does the 100 watt inverter draw?
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Old 07-28-2019, 09:28 PM   #35
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Sounds like I just might have found a justification for buying a new laptop.


How many real world watts does the 100 watt inverter draw?
Unless specified otherwise, figure about 75% efficiency on the inverter. So whatever the actual AC draw is +25%.

They do also make cigarette plug chargers for laptops up to 150W, those work for pretty much everything except the high end gaming machines. Far more efficient that way instead of going DC-AC-DC. I use the inverter because it was a lot cheaper ($12) than the DC-DC adapter (about $70) and it's just for use in my truck, I'm not worried about off-grid.
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