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gcrank1
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# Posted: 13 Feb 2023 08:33pm
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Oh....and your 33amps est and 8ga. wire is WAY off
A 4000W inverter needs wires from the bat-bank big enough to carry the whole 12v input load (Not the 120v output) for the 4000W; that is the Massive 334Amps!
Then there would be the proper fusing.....
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travellerw
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# Posted: 13 Feb 2023 10:23pm - Edited by: travellerw
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Ok.. Lets start with some math.
First a toaster oven is rated at about 1250-1500W (depends on brand and size). Lets assume the worst case scenario @ 1500W.
1500W divide by 12.2V (sag voltage of a FLA batt at that draw). Equals 122.95A.
Now if we assume your inverter will be 2ft from your battery bank than that is 4 ft of wire (you must add the positive and negative wire lengths together). We will also say, not more than 3% loss in the wire and never let the wire get hotter than 75C. To meet this requirement you will require 1AWG. However, 1AWG would be good all the way up to 12ft (or 6ft from your battery bank). Just some numbers for you to chew on.
Another thing to think of is that fridge. I don't know what it is, but you said it states 50W (could be true). If so it will consume 50Ah @ 12V per day. Now remember you shouldn't draw FLA batts down below %50, so you really only have 200Ah of usable power (with brand new batts). 50Ah is a pretty sizable chunk when you add the 30Ah you will consume with the toaster oven. Cloudy days happen.. LOTS..
Finally, the solar panels. That is a whole onion to unwrap for sure. I'm not sure how you calculated your usable Kwh, but that can be pretty complex. There are calculators out there to help that will calculate based on your location, tilt of the panels, ect. Its good practice to take %15-20 off of those numbers.
Anyway.. Its a deep topic with lots of opinions. The only real truth is in the math and results. I would suggest you spend a bunch of time researching and reading on places like DIY Solar Forum.
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gcrank1
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# Posted: 13 Feb 2023 11:26pm
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For an array Ive seen figures of 60% to 70% fairly often; ie, an 800W array will do 480-560W and that on good 'solar days' and depending upon location about 4-5hrs in a good summer day. (Winter....pfffft to some, Ive seen folks tell of 10%)
That means 2160W to 2520W of a 4.5hr good summer day.
I tailored my amps usage so my LA bats would recharge by noon-1pm the next day (if a good solar day), that with some use right off the solar while charging, not a lot. Our big use is evenings and if hot all night with a fan running.
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Brettny
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# Posted: 14 Feb 2023 06:03am - Edited by: Brettny
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Quoting: gcrank1 A 4000W inverter needs wires from the bat-bank big enough to carry the whole 12v input load (Not the 120v output) for the 4000W; that is the Massive 334Amps
Then theres the fact that a typical 12v or 6v batter is not rated to output that many amps. The other thing is 4 100ah batteries wouldnt last very long at all with that load.
I didnt do the math but do have a solar setup that runs a 4.5cuft fridge. Unless you have lithium batteries your going to need more battery than that. I also think the 4kw inverter is way overkill.
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Ominous Ann
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# Posted: 14 Feb 2023 02:38pm
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No I nailed the estimated amp draw in DC
The wire size isn't 8 aug wire, it's -8 or 00000000 gauge. Which is huge and doesn't like to bend.
My arrangement puts the inverter in a straight line with the batteries so  not my first rodeo.
My confusion stems from the fact these guys don't list the amps available in each of the four circuits.
Also nothing is set in stone, I have bought anything and won't till it all makes sence.
Gotta go look up Renogy now, someone mentioned they weren't all that. So gotta look into it.
Cheers and thanks for all the great info.
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Ominous Ann
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# Posted: 14 Feb 2023 02:53pm
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The estimate of the panels output is from the manufacturer so yes it's likely inflated.
The fridge at 50 watts per hour
50 x 24 = 1200 watts at 120 = 10 amps ac or 100 amps DC or 4.2 amps DC per hour.
At 1/4 of peak an 800 watt solar system should produce 200 watts / 12 volts or about 30 amp/hr.
Seems like it should work
And the battery load is 1/4 of that across all four batteries or 25 amps each over each 24 hours or 1 amp per hour
Also seems like it should work.
The 4000 watt inverter was only a few bucks more than the 2000 watt. I kinda like to oversize things like that so they dissipate heat better and lose less efficiency.
I could be wrong and I'm all ears but it seems like I'm on the right track with my numbers and just need to settle on the components.
Thanks for all the great advice.
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FishHog
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# Posted: 14 Feb 2023 03:45pm
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realistically the fridge once cold will run 1/2 of the time give or take depending on outside temp and how much you open it.
I would look into the standby power draw of that inverter compared to a smaller one. Upsizing can be good, but it might waste a lot of standby power compared to a smaller one. I don't know if that is true, but I'd research it before deciding bigger is better. While it almost always is, it isn't always.
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Ominous Ann
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# Posted: 14 Feb 2023 05:44pm
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I will. I'm also going to look into the LI batteries someone suggested.
My thinking on the inverter size was I wanted something that would handle two 15 amp 120 lines
120 x 15 = 1800 watts
x2. = 3600 watts
= a 4000 watt inverter
Granted the fridge isn't going to draw 15 amps but I calculated it that way just to be sure.
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Ominous Ann
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# Posted: 14 Feb 2023 11:19pm
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Hmmmm
I changed the batteries from V-Max 12V 100 amp hour group 27 (whatever that is) 70 lbs $299 each. No cycle life listed.
to
LiFePo 4
12V 100 amp hour model YX-12100LF 23 lbs $279 each. 7000 cycles
The Lithium battery suggestion was a good one. Saved enough weight I'll need to adjust some other stuff to keep the weight balanced throughout the vehicle some but
Great idea.
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gcrank1
Member
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# Posted: 15 Feb 2023 12:11am
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My target with LA been to use the top 30% of charge to get good battery life and be able to recharge in a reasonable amount of time (they charge slow)
With the LFP, where a good 90% is usable, it is like one 100Ah LFP equals 3 x 100Ah LA.
And with my 40A power supply 'charger' I can recharge in 2.5hrs! Was a total game changer for me.
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razmichael
Member
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# Posted: 15 Feb 2023 07:32am
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Quoting: Ominous Ann to keep the weight balanced throughout the vehicle some but
Might have missed this earlier regarding this being for a vehicle. May not be applicable but keep in mind the limitations of charging LFP in cold temperatures.
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FishHog
Member
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# Posted: 15 Feb 2023 07:49am
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I missed the vehicle part as well. In the camper van I built, I went Lithium for weight and to avoid any offgassing as they are inside.
The charging below freezing isn't much of an issue for me as I use the van in warmer places and heat the inside in cold places. But I do keep an eye on it. Had the van all loaded up ready to go except for water, and it got cold. I was 36 hours driving south before the battery warmed enough to allow it to charge. Now I put it in last keeping it warm until we leave.
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Brettny
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# Posted: 15 Feb 2023 08:06am
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Quoting: Ominous Ann The wire size isn't 8 aug wire, it's -8 or 00000000 gauge
Never seen that wire used. Arnt you into MC300 mc400+ catagory at that point?
I work on systems with 700vDc and 1500A fuses and never saw anything over 0/4awg labeled anything but MC???.
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travellerw
Member
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# Posted: 15 Feb 2023 10:59am
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Quoting: Ominous Ann The 4000 watt inverter was only a few bucks more than the 2000 watt. I kinda like to oversize things like that so they dissipate heat better and lose less efficiency.
That logic does not work with cheap Chinese inverters. It simply doesn't work with made up numbers.
If you want to look at Victron, Mastervolt, ect, then sure. Pretty sure you won't find a 4000W @ 12V with those brands. There is a reason why!
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Steve_S
Member
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# Posted: 15 Feb 2023 02:20pm
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I've kept out of this rabbit warren but will add this for clarity. ONLY ADDING BASICS !
The General Rule is to not pull more than 250A from a "Battery Bank" regardless is 12,24,48,72VDC.
12V X 250A = 3000W (120V=25A / 240V=12A)*
24V X 250A = 6000W (120V=50A / 240V=25A)*
48V X 250A = 12,000W (120V=100A / 240V/50A)*
* NOT Corrected for Inneficiencies & losses
Surge Handling Capabilities allow for this to be exceeded "momentarily" to supply Start Power (Surge Demands) for motors like Fridge, Well Pump etc but this is for less than 30 Seconds.
High Frequency Inverters can only handle X2 Surge while Low Frequency Inverters can handle 3X the surge and are more capable for anything with a motor.
Tier-1 / High Quality Brand Name Inverter Systems such as those from Samlex, Victron, Magnum etc can be up to 97% Efficient. "Value Grade" from cheapo no name brands (Chinese & Other) to even brands like RENOGY (aka Run Ohh Gees) average between 85-90% efficiency.
LFP - LiFePo4 - Lithium Iron Phosphate Battery info.
- By Default, cannot be charged below 0C/32F.
- LYFP (very $) can charge from -30C but LYFP is NOT sold for ESS Usage & is very $$
- Can Discharge @ 1C Rate but only take 0.5C Rate for Charging.
- Capable of up to 3C Burst Rate depending on BMS (Battery Management System)
- Charges much faster than Lead Acid chemistries.
- Do not offgas or leak.
- Can have between 6000-10000 Full Cycles if kept within the Working Voltage Range.
An A-Typical 12V/100AH LFP Battery Pack will provide 1,280Wh or 1.2kWh with a Working Voltage Range of 11.6V to 13.6V. Yes this is a Very Flat voltage curve.
Commercial LFP Battery makers offer them without warmers by default but now most product lines have a warming feature as an option. NOTE that if a battery uses a warmer, that energy is drawn directly from that particular battery and is controlled by that battery's BMS.
A SPECIAL NOTE ON VOLTAGES !
Do NOT bork your project !
If going 12V, then stick to 12V batteries, if going 24V then BUY 24V, do not kludge 12V batteries together in series to make up the voltage. Stay Native and apply KISS rules.
MOBILE APPLICATION
Charging will be an issue and depending on the chemistry you choose it could get complicated. Vehicle Alternators are good for Lead Acid Vehicle Batteries but they are lousy for Big Batteries with lots of Amp Hour and rotten with Lithium based chemistries. If you intend to use the Alternator for charging batteries (beyond the normal 12V car battery) an upgrade WILL be required to handle the larger capacity batteries. If you intend to use LFP or other Chemistries an external DC to DC Charger is most often required but there are many ways to get there and thanks to the Marine folks, it's well sorted with many options & possibilities (but all at a cost).
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More info than intended but there for review later on for anyone looking at this thread.
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Hope it Helps, Good Luck.
Exiting Rabbit Warren.
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Ominous Ann
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# Posted: 17 Feb 2023 06:59pm
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Yeah I got the 8/0 wire size wrong, I can get away with half that. I went with LIFEPO-4 batteries.
I did more research on the wire sizes and compared a bunch of different calculators and came up with this for a layout. Wire sizes are noted.
The system is independent of the alternator and I seriously doubt I'll be drawing any more than 200 amps dc or 20 ac at any given moment, and even then it would only be for a very short moment.
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Brettny
Member
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# Posted: 17 Feb 2023 08:10pm
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Your diagram shows a short in the system.
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Ominous Ann
Member
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# Posted: 17 Feb 2023 08:18pm
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LOL no
The terminals coming off the inverter are above one another, so in plan view it might look like there's a red and a black connected but in fact there just above and below one another.
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gcrank1
Member
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# Posted: 17 Feb 2023 08:34pm
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Well, um....really, this has taken the original thread so far off the rails and deeply into your project that I seriously recommend you start your own thread.
It aint hard, then it is All About Your Project.
Please
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Ominous Ann
Member
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# Posted: 1 Sep 2023 09:27pm
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Completed the system months ago and it worked like a charm, first time, no corrections. Been working perfectly going on six months now.
I'd have never made it without your faith in me LMAO.
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