Amp draw vs battery bank & solar array = totally confused!

[Sarahps33]

Hey there, so I'm hoping some of yall have already dealt with this and could shed a little light.

Things aren't making since to me. I have checked each appliance's output power that I plan on bringing on the road.

For example my laptop says 20v/2.25a on the charger.
For each device like this I went to this website for a quick calculation: https://www.batterystuff.com/kb/tools/dc-to-ac-amperage-conversion-run-through-an-inverter.html

And I'd turn it into 12v DC - giving me the amp draw.

In the case of my laptop it was converted to 4.14a
I took those amps and multiplied it by how many hours a day I would use it.
The most I'd ever use it in one day would likely be 7hrs.
4.14a x 7hrs = 28.98a

So that tells me how many amps I'd use from that laptop a day, right? Am I doing it right so far? Lol.

I did this for my coffee maker, phone charger, flashlights, printer, and so on and came up with 348 amps that we could "potentially" use in a day if we used and charged everything we owned in a single day (I think that's overkill, but just in case right.)

And that's without a fridge. We want a fridge with a freezer so we can be off grid for longer periods of time. I have one now and if it ran 12hrs outta 24 it would be an additional 192 amps.

So the total with a fridge is 539

That seems like an awful lot to me. I dont understand how people have whole gaming systems, fridges, and microwaves and can run off a small batt bank.

Did I mess up somewhere?

I'm reading that AGM's have a depth of discharge rate of 80-50%. If we used 80% of each batt then we'd need seven 100ah batts just to run for one day! (539a/80a=6.7 batts at 100ah). If we wanted enough back up power for 2 days (say it was cloudy out) than we need 7x3 = twenty one 100ah batteries. That's what I dont understand....

But! I also understand that this is where solar charging rates come in. I've only seen 60a being one of the highest charge controllers. So does that mean I can charge with 60 amps an hour with my solar panels? (Assuming I have full sun light?) And say I have 4 hrs of full sunlight a day 4hrs x 60 amps = 240 amps charged per day.

With an amp draw of 539 it would take roughly 2 days and 1 hour to put that back into the battery bank. And that would still only be replenishing our daily draw but not as fast as we use it and wouldnt provide those 2 days of cloudy weather cushion.

I'm so in need of some help here, lol. I cant wrap my head around it.

Thank you so much in advance for any info you can give me.

[Lwiddis]

“ They sell relatively small 6v batts that start at 225ah”

A small wet battery with 225 amps weighs about 65 pounds. Times six…400 pounds.

[JimK-NY]

It seems lots of ideas have been contributed but to my understanding it does not seem the concerns of the OP were answered.

I have a few comments that might help with my understanding of the OP's issues. First, it seems the OP is trying to start with an energy use audit. Trying to base that on manufacturer's specs is not going to work well. Instead actual measurements are needed. My solar system can do this for me. With consistent solar light I watch the steady amp charging amount. I then turn on the appliance being audited and note the decrease in amps. Looking at a computer, even a small laptop, is extremely important. They take a significant amount of power, probably more than most people realize.

In conjunction with the initial audit, it is highly important to find ways to reduce power consumption. First would be to avoid use of major appliances such as the microwave or an electric coffee pot. I only use my microwave on rare occasions when I have shore power or when I specifically start up the generator for using it. I found a way to make great coffee with just boiling water heated with propane.

Even small adjustments can help. I avoid the use of an inverter. I found 12 v chargers for laptop and almost all other items. I never found an option for camera or flashgun batteries so for them I use a small, cheap, non-sine wave inverter. A large, sine wave inverter wastes a lot of power.

The final step is to size the solar charging system. The size often depends on money and available space. Regardless of the size, a generator is still going to be needed for cloudy days, for camping in the shade, or when the requirements are just too large. A big solar system will minimize but not avoid all generator use.

[valhalla360]

pianotuna wrote:
What drives my crazy is folks who run non vented combustion heaters--especially catalytic.

Who suggested that on this thread?

[StirCrazy]

Gdetrailer wrote:

Itinerant1 wrote:
I don't even worry/ think about the 48ah draw with the lfp's. I could probably make an adjustment within the ME-ARC if it was a issue. The 1,280w solar & 500ah lfp are a pretty good match together. When the day comes and I just need to replace the batteries I'll probably add 100ah more and just about eliminate the generator except for the very rare stretch of bad solar production days, but that might not be for a few more years seeing the batteries aren't showing signs of voltage sag with high draws for long periods of time yet nearing 6 years of daily use.

Not everyone has deep, deep pockets full of money nor does everyone wish to pack 1.2KW worth of solar on their roof and on the sides of their RV. That is why I mentioned using smart technology like inverters with power saving feature.

It is why I can run my home fridge, plus 30K BTU furnace, some lights and yes even some TV and PC for entertainment for 24 hrs without solar or generator and still have power leftover out of one pair of 6V FLA GC2 batteries.

If I really wanted to boondock full time, I can simply add 3 100W solar panels which would extend my time between using a gen to charge the batteries to several days all on one pair of GC2s..

So, $300 in solar panels and my trusty $200 worth of GC2 batteries for $500 in total can easily hang with $1.2K in solar plus $3500 worth of Lithium 500Ahr battery bank..

The key is conservation, I can live like I am on the grid with only a few minor changes like putting things that do not need power 24/7 on power strips with switches, turn items off via the power strip saves a lot wasted energy in phantom loads. Conservation is a lot cheaper than trying to pretend you are still on the grid with wasteful habits.

I don't find solar a waistfull thing at all. Rather I think generators are a waist I did the camper for 600CDN and have never ran out of power and I don't get hookups or stay in campground for that matter, well technicly they are forestry sites and turn offs up in the mountians so some could be considered campground but primitve no hookups , heck some don't even have picknick tables or toilets and you have to bring your own firewood. if you ran a generator in some of these places anyone else up there would probably linch you, and in most normal campground you get two hours in the morning and teo hours around supper that your allowd to run the genny. so 1 to 2000 cdn for somthing you can barley use? plus I now find the peace and quiet is what I am camping for, even the drone of a quiet honda gets on my nerves now.

on my 5th wheel I use about 80AH/day and my 480 watts of solar makes sure I am topped up every day as long as it is nice. I will be upgrading these to 24V panels and a new mppt charger so I will have just shy of 1000 watts. my camper is more primitive, no microwave, only one 120 outlet but no inverter so its 12V life in there. I have a 325watt 24v panel on that with two GC2 batteries for now and I have only been concerned about power after three days of rain and no sun. I will be putting one more panel on that one also to just bump that 3 or 4 amp charge on a dim day up to 8ish, also going from 100 watts of usable battery to 300ish of LFP will make a big difference in my sun dependency.

[Itinerant1]

One person's waste is another person's living/ enjoyment. 😉

Edit: 0700 this morning walking the dogs enjoying a cup of coffee and not a soul around within view of any direction. 35% SOC making second pot of coffee and use the microwave for breakfast. If this is wasteful I'll happily keep lugging around the solar on the roof.

[Gdetrailer]

Itinerant1 wrote:
I don't even worry/ think about the 48ah draw with the lfp's. I could probably make an adjustment within the ME-ARC if it was a issue. The 1,280w solar & 500ah lfp are a pretty good match together. When the day comes and I just need to replace the batteries I'll probably add 100ah more and just about eliminate the generator except for the very rare stretch of bad solar production days, but that might not be for a few more years seeing the batteries aren't showing signs of voltage sag with high draws for long periods of time yet nearing 6 years of daily use.

Not everyone has deep, deep pockets full of money nor does everyone wish to pack 1.2KW worth of solar on their roof and on the sides of their RV. That is why I mentioned using smart technology like inverters with power saving feature.

It is why I can run my home fridge, plus 30K BTU furnace, some lights and yes even some TV and PC for entertainment for 24 hrs without solar or generator and still have power leftover out of one pair of 6V FLA GC2 batteries.

If I really wanted to boondock full time, I can simply add 3 100W solar panels which would extend my time between using a gen to charge the batteries to several days all on one pair of GC2s..

So, $300 in solar panels and my trusty $200 worth of GC2 batteries for $500 in total can easily hang with $1.2K in solar plus $3500 worth of Lithium 500Ahr battery bank..

The key is conservation, I can live like I am on the grid with only a few minor changes like putting things that do not need power 24/7 on power strips with switches, turn items off via the power strip saves a lot wasted energy in phantom loads. Conservation is a lot cheaper than trying to pretend you are still on the grid with wasteful habits.

[Itinerant1]

I don't even worry/ think about the 48ah draw with the lfp's. I could probably make an adjustment within the ME-ARC if it was a issue. The 1,280w solar & 500ah lfp are a pretty good match together. When the day comes and I just need to replace the batteries I'll probably add 100ah more and just about eliminate the generator except for the very rare stretch of bad solar production days, but that might not be for a few more years seeing the batteries aren't showing signs of voltage sag with high draws for long periods of time yet nearing 6 years of daily use.

[Gdetrailer]

Itinerant1 wrote:

StirCrazy wrote:

Itinerant1 wrote:
Batteries living in the PSOC (bouncing between 25%-95%) using whatever is needed at anytime during this period of time with the daily use of 200-250ah. Decided yesterday to do a full charge using the generator, it was another overcast/ drizzle day and at 1:45pm (47% SOC) with solar production of only 50ah total for the entire day.

wow 50AH a day is my daily use in the camper on a cold evening with the furnace running a bit during the day and all night. in the summer I only use about 20 to 25AH.

Steve

The inverter alone is 48ah daily. Like I said I live like on hookups. December is the roughest month power production/ use with shorter daylight hours, if I can get the nose of the 5th wheel facing the sunrise solar production is usually good throughout the day with little needed help from the generator with an hour charge boost on occasion. This is the 6th winter on the system using it like this.

If you have 120V devices that do not need to be powered 24/7 you could use an inverter which has a power save or load sense setting. That will easily slash your wasted power via the inverter running with no load by half.

The inverter I used for my home fridge conversion has that capability, I set it so a 9W load will trigger the inverter on. When no 120V load is detected the inverter goes into a deep sleep. Load detection is nearly instant on, just a slight delay when I open the fridge door and the 120V light turns on.. Granted that may not work well for say your TV, but for myself it is enough savings that it beats having to drag an extra pair of GC2 batteries around.

[Itinerant1]

StirCrazy wrote:

Itinerant1 wrote:
Batteries living in the PSOC (bouncing between 25%-95%) using whatever is needed at anytime during this period of time with the daily use of 200-250ah. Decided yesterday to do a full charge using the generator, it was another overcast/ drizzle day and at 1:45pm (47% SOC) with solar production of only 50ah total for the entire day.

wow 50AH a day is my daily use in the camper on a cold evening with the furnace running a bit during the day and all night. in the summer I only use about 20 to 25AH.

Steve

The inverter alone is 48ah daily. Like I said I live like on hookups. December is the roughest month power production/ use with shorter daylight hours, if I can get the nose of the 5th wheel facing the sunrise solar production is usually good throughout the day with little needed help from the generator with an hour charge boost on occasion. This is the 6th winter on the system using it like this.

[StirCrazy]

Itinerant1 wrote:
Batteries living in the PSOC (bouncing between 25%-95%) using whatever is needed at anytime during this period of time with the daily use of 200-250ah. Decided yesterday to do a full charge using the generator, it was another overcast/ drizzle day and at 1:45pm (47% SOC) with solar production of only 50ah total for the entire day.

wow 50AH a day is my daily use in the camper on a cold evening with the furnace running a bit during the day and all night. in the summer I only use about 20 to 25AH.

Steve

[OkieGene]

I'll 2nd the suggestion of getting a Kill-a-watt meter.

[pianotuna]

Valhalla,

Nope.

I push hard on balanced wiring, solar, and a few other topics, too.

What drives me crazy is folks who run non vented combustion heaters--especially catalytic.

[valhalla360]

pianotuna wrote:

valhalla360 wrote:

Lead Acid batteries can take a fairly large bulk charge up to around 80-90%...it's that last 10-20% that are slow...so...

Run the generator in the morning to bulk charge quickly to 80-90%, then let the solar top up the batteries slowly over the rest of the day.

Yes, occasionally, the solar won't do the top up but as long as it's not all the time, the batteries should remain happy.

That's a great plan Valhalla360.

Unfortunately Lead acid do want to get to 100% as often as possible. My favorite battery doesn't require that, except once every 30 cycles.

We need specifics and to run a few numbers if we want to be sure but in general terms, you can get 80-90% in 1-2hours with a generator and then a modest solar array should be able to top up the final 10-20%...this will get you up to 100% most days and you can expect a nice long life out of the battery bank.

PS: do you have a franchise for your "favorite battery"...you seem to be pushing them really hard on multiple threads.

[pianotuna]

valhalla360 wrote:

Lead Acid batteries can take a fairly large bulk charge up to around 80-90%...it's that last 10-20% that are slow...so...

Run the generator in the morning to bulk charge quickly to 80-90%, then let the solar top up the batteries slowly over the rest of the day.

Yes, occasionally, the solar won't do the top up but as long as it's not all the time, the batteries should remain happy.

That's a great plan Valhalla360.

Unfortunately Lead acid do want to get to 100% as often as possible. My favorite battery doesn't require that, except once every 30 cycles.