Need advice on "reasonably priced" 24V inverter

[Sunking]

I spoke with Renogy. They said if I wish to run a small 5000 BTU air-conditioner, I should have eight 100 Ah batteries and that would give me about 4-1/2 hours of run time.

That is horrible advice. If you need 800 AH, buy 800 AH batteries. Never ever parallel batteries.

As for Trojans, you get what you pay for. Any of the FLA models would work. You need to come to terms with anything you take off-grid is going to cost you 5 to 10 times more than buying power from the POCO, and also makes you a heavy heavy polluter. So wrap your head around going off grid is going top be very expensive, lot of work, and nasty nasty for the environment.

[RenewablesRock]

AGM batteries have a niche application in solar, but you are paying a premium for something you do not likely need. AGM's cost roughly twice as much as FLA batteries and only last half as long making the end of life cost almost 400% higher. Running in parallel will shorten cycle life significantly. When it comes time for replacement I suggest you use say 6-volt 225 AH FLA batteries. A excellent quality battery is the Trojan T-105 and sells for $140 most everywhere. Initial cost are lower $140 / 1350 watt hours = $103.70 and will last 3 to 4 years vs 1 to 2 years for what you have now.

Yes, these same Universal 100 Ah batteries were $120 back in 2016. https://amzn.to/2NAZJkd

I would love to run those Trojan batteries, but I also have two existing Duracell Ultra 12V 100 Ah AGM batteries that I paid a fortune for. I spoke with Renogy. They said if I wish to run a small 5000 BTU air-conditioner, I should have eight 100 Ah batteries and that would give me about 4-1/2 hours of run time.

How can I get Trojan batteries with the same power for that price that are safe to put in the closet of my bedroom?

[Justin B.]

I will probably seriously consider that. I checked my receipts and the batteries were $159/shipped but that doesn't change the overall numbers that much. I went AGM due to my experience with them lasting considerably longer in my motorcycles as compared to regular lead acid plus the batteries are inside the cabin and at this time I don't have them enclosed or vented. Possibly by the time they die I can build a little "hooch" for the generator on the north side of the cabin. If I make it a two level thing I could put the batteries on the upper level (so the vented H2 will rise away from the generator) and the generator on the bottom.

I found that Sam's Club has Duracell 6v golf cart batteries for $124 and change. Here are the specs:

• 20 amp hour rate: 230
• 5 amp hour rate:174
• 6 amp hour rate: 178
• Battery electrolyte composition: acid
• Battery end type: top post
• Battery purpose: deep cycle
• BCI group size: GC2
• Freight class: 65
• Minutes at 25 amps: 448
• Minutes at 75 amps: 120
• Terminal type: DIN
• Volts: six

[Sunking]

They were $169/shipped ea. from Amazon.

Justin sounds like you are back on track an din the process of optimizing your system. Here is some food for future thought. It will not be long before it is time to replace the batteries, much sooner than you think. I assume those batteries you bought are 12 volt 100 AH AGM for $169 per battery? To put this into perspective a 12 volt x 100 AH battery has a capacity 1200 watt hours 1.2 Kwh. That means you paid $169 / 1.2 Kwh = $140.84-Kwh. With me so far and understand what I just did.?

AGM batteries have a niche application in solar, but you are paying a premium for something you do not likely need. AGM's cost roughly twice as much as FLA batteries and only last half as long making the end of life cost almost 400% higher. Running in parallel will shorten cycle life significantly. When it comes time for replacement I suggest you use say 6-volt 225 AH FLA batteries. A excellent quality battery is the Trojan T-105 and sells for $140 most everywhere. Initial cost are lower $140 / 1350 watt hours = $103.70 and will last 3 to 4 years vs 1 to 2 years for what you have now.

[Justin B.]

How much are the 100 Ah batteries? From Batteries Plus, mine were super expensive. I see on Amazon, I can get a Renogy 200 Ah battery for $369/ea. Would it be good to have 3 of these or have 6 of the 100 Ah?

They were $169/shipped ea. from Amazon.

[Mike90250]

How much are the 100 Ah batteries? From Batteries Plus, mine were super expensive. I see on Amazon, I can get a Renogy 200 Ah battery for $369/ea. Would it be good to have 3 of these or have 6 of the 100 Ah?

Until you get your system dialed in, and understand your actual loads and recharge capability (bunches of 100 w panels is a poor choice) I'd say use cheap 200ah, 6V golf cart batteries,. they will survive a couple mistakes before they conk out, much better to learn with cheap batteries. Besides, when done right, you can get 5 years out of them

[RenewablesRock]

Here will be my system after the Samlex inverter gets here:

8 - Renogy 100 W mono panels
60 A MPPT Charge controller
Samlex 1500 watt 24 V inverter
6 - Universal 100 Ah AGM batteries configured in series-parallel

Panels about 20' from cabin wired with #10 stranded wire and all battery cabled are #4.

How much are the 100 Ah batteries? From Batteries Plus, mine were super expensive. I see on Amazon, I can get a Renogy 200 Ah battery for $369/ea. Would it be good to have 3 of these or have 6 of the 100 Ah?

[Justin B.]

I have mostly came to the conclusions you have pointed out. I really don't care that much about bedside manner as long as I get a good answer. Unfortunately I threw this stuff together THEN started researching and visiting forums so I freely admit I did pretty much everything wrong except for initially buying a 60 amp MPPT charge controller. After your comments, a true assessment of my power needs, and my conclusions, I have ordered a Samlex 1500 watt 24 V pure sine wave inverter, 24 V LED bulbs, and a 24 V pump for my shower and kitchen sink. I will re-cable my 12V batteries in series-parallel and hope for the best. With the 24 V battery configuration I can then add the other 100 W panels to my array so I will have 2 parallel groups of 4 in series for a little over 80 V coming in from the panels. Hopefully this will keep the batteries charged as my 45 A IOTA 12V charger won't do me any good after the switch.

Here will be my system after the Samlex inverter gets here:

8 - Renogy 100 W mono panels
60 A MPPT Charge controller
Samlex 1500 watt 24 V inverter
6 - Universal 100 Ah AGM batteries configured in series-parallel

Panels about 20' from cabin wired with #10 stranded wire and all battery cabled are #4.

[Sunking]

OK where to start? If you are doing this as an upgrade, tap the breaks because nothing makes any sense. To start with most people consider 12 volts to be safe which is a half truth. It is safe in terms of low voltage, but is not capable of high power safely. It is fine for low voltage lighting, landscape lighting and other low power applications where wiring might be exposed to children. Low voltage is relatively safe in terms of Touch Shock potential. However it becomes very dangerous at high power levels. The issue is current and resistance. Power = Voltage x Current. If you have a fixed low voltage like 12 volts, to get high power means you have to increase current. High currents means very large wires, professional low resistance connections, and great care and detail on terminations. Just the slightest loose connection or undersized wire results in fire and melting copper wire. At 1000 watts when you consider efficiency on a 12 volt Inverter requires 100 Amps. 100 amps of current requires #4 AWG or larger copper wire. At 3000 watts is 300 amps and requires 4/0 AWG copper wire about the diameter of your wrist and use 3/8-inch hardware terminals which I guarantee neither you used nor can your 12 volt Inverter handle that size of wire or hardware.

100 amps is as much as a consumer can safely work with, and that does not imply it is safe. Still great care must be taken with wire sizes and termination. With a 100 Amp limitation means power get limited by voltage. 1000 watts @ 12 volts, 2000 watts @ 24 volts, and 4000 watts with 48 volts. You are at 3000 watts @ 12 volts, so the question is why change?

I think you are certainly correct in that 2000 watts is still much more than you likely need. and I highly doubt you have the battery capacity to even deliver 1000 watts for any length of time. 3000 watts @ 12 volts on paper requires a nice 12 volt 2000 AH battery weighing in around 1200 pounds. I also suspect you are using 12 volt batteries which was another oversight. To get 2000 AH using 12 volt batteries would take 10 to 15 batteries in parallel. Do you have any of that? If you did would need to start over to make it right and safe. So why do anything? You are already operating as inefficient as you possible can and as dangerous as you can make it? Why change to 24 volts and waste your money?

No wif you want to make things safe, more efficient, and made to work we can help you. But you need to completely change your outlook. Start by sane Inverter wattage selection. 24 volts is fine and dandy and can go up to 2000 watts providing you have a 2000 watt panel system, 80 amp charge controller, and a 1200 pound battery to feed it. Think more like a 500 to 1000 watt Inverter and a 300 to 400 pound battery like 4 x 6-Volt 250 AH golf cart batteries.

Now all that may piss you off and I do not care if it does. You just got the best advice you will ever get. Think what you really need, then design a system that can actually do it safely and economically.

[Justin B.]

I need to upgrade the installation in my cabin from a 12 V inverter to 24 volt. I need some suggestions for a reasonably priced 2000 - 3000 W pure sine wave 24 V inverter. I currently have a 3000 W 12 V inverter but don't think I really need 3 KW.

Thanks...