12 or 24 volt?

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Daiki Jin

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Ok in designing the trailer I would like to build, I'm stuck on the age old issue of power. I have a good background with 12v systems along with figuring out PV while I living in my Jeep. But for this trailer build should I start out with the 12v/100w panel, 100ah Lifepo4 battery, controller, DC-DC charger and 2000W inverter I currently have. Or upgrade to 24v to cut down on wiring sizing and costs and better power flow?

Subject to change specs depending on size of trailer I get plus budgeting:
3 panels from 300W@12v total to 360w+ if I go 24v
2x 100ah batteries... so either 200Ah@12v or 100Ah@24
won't use it much but would like at least a 1000W - 2000W inverter
switch for using shore power to charge and run 120AC while plugged in

Battery power will be running while we camp.
Fans to keep inside of trailer cool ( not living in it but for food storage and clothes)
Fridge either my current 12v compressor model or upgrade to something bigger maybe even a mini fridge ( hence inverter)
USB ports for phone charging
Lights for around tent and awning attach to trailer
possible water pump for sink and/or toilet

maybe a couple external connections for secondary moveable solar panel depending on how much sun hits top of trailer
 
I highly recommend going to 24v system. I have been living in the west TX desert, off grid now for over 4 years. I have a 24v system, started out with a 12v system until I could get set up, a month or so later. I would have went 48v but I am paralyzed from T4(chest) and my power chairs are 24v, so I use that for convenience. I have 2 separate systems, one for general use(my hut and garage containers, and one for my chair. It is WAY more efficient, the higher the voltage you go. NOTE After 24v systems, the price of inverters and charge controllers take a big leap. I have 2 x 40amp charge controllers, and one 24volt 2500w pure sine-wave inverter and 5x330w panels for the hut and 4 x 330w panels for my chair. The bulk/5 of my panels I bought used for 150 bux and they are the best/highest output, The new initial 3 were a little over 300 per panel. I saved a boatload buying used. 2(gave one to a friend) I bought used for 117 each. About 130 each for charge controllers and less than 200 for my inverter. NO WAY would I use a 12v system.
 
Or upgrade to 24v to cut down on wiring sizing and costs and better power flow?
If you are starting from scratch I think 24v panels and batteries are a little better, for reduced wire sizes and cheaper MPPT. You can get cheap little buck converters that you can place next to larger 12v loads too, so you can run mostly 24v from your batteries.

With 24V you will have less than half as much drop.
1/4 as much power loss. Or 1/4 the wire cross section and the same loss.

...And a single lithium battery, or even two 12V lithium batteries in parallel, would not be able to handle that much current on a continuous basis. Almost all 12V 100Ah lithium batteries are rated for 1C continuous discharge, which means 100A continuous.
In parallel they'd handle 200A, yes?
 
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Depends on the BMS, they are rated different for different purposes. I would go Amazon and get them there, still cheap and reliable as well. All the ones 100ah and above have 100a charge/discharge rates.
 
Yeah I built my battery pack from grade A cells I bought that were matched. Plus being they were cells I had the option when I was putting them in my Jeep I could lay them down flat for a lower profile. I would probably go same route and buy 8 new cells instead of trying to tie 4 new ones into my 3 year old ones.
 
tldr = If you are buying a 12V 100Ah battery for $350-450 on Amazon it is Grade B. Guaranteed.
You are wrong. When I first joined these forums a few years back, there was a guy named Will Prowse that reviewed solar components. He is on youtube with lots of videos breaking down the various batteries on amazon. In particular, the BMS. You would be benefitted greatly by going there and watching them. I am not going to teach a class here. Take my contribution or leave it.
 
Good info in the links posted above.
I have been reading the reviews over the past year or so on the several main sellers of them and I am pretty sure there were more than a handful of posts that identified the quality of cells. They also carry good reviews for mfg/seller replacement and warranty issues. I have a few different suppliers bookmarked for when I have the money, going to get them hopefully soon.
As always, do your own research, bad sellers everywhere for anything.
 
Here is one of the quality sellers, WAY better deals than most, ahem. https://www.amazon.com/Ampere-Time-...330-a548-74a658715741&pd_rd_i=B08P6LP1J9&th=1
also these folks https://www.amazon.com/dp/B091YCZV2...pY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU&th=1
I will add a video of a well trusted guy in the community for MANY years, where the battery is broke down, and he gives the test results, as I IMPLIED in my other post. Here is a short about him, https://shopsolarkits.com/blogs/learning-center/who-is-will-prowse-diy-solar



 
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...well trusted guy in the community for MANY years, where the battery is broke down, and he gives the test results, as I IMPLIED in my other post.
He tests it for capacity only. That definitely does not mean they are grade A. I've never seen him state that grade A cells were used in one of those cheap batteries.
 
@Daiki Jin
Not knowing your trailer dimensions and actual system layout, it's hard to say if you'd benefit from going to 24-volt, considering such low demand. Still, the price of copper wire has increased significantly since I refurbed my camper back in December 2021 through January 2022. I had bought a lot of components before then, and lucky thing, too, considering inflation. That said, I think a year from now, you'd wish you had gone to 24-volt.

As to budget, you don't need the newest and best of the best and, therefore, the most expensive, nor does it have to last ten years; newer and better tech is always just around the corner. It's a costly illusion; don't fall for it. From reading the thread, it seems you've already gained the experience of building your battery, as did I, but with the cost and quality of ready-made batteries, it doesn't make sense. Used solar panels are dirt cheap and perfectly good. I bought nine used 250-watt panels for $65 each last year, and they're working just fine. I have them in three arrays, each array managed by an EPEVER 4215N 40 Amp MPPT. One is for ground deployment.

Since you're still designing and budgeting, I'll tell you what I did and why instead of what you should do. You could get by very well with half my system. You seem to have the basics down. A couple of years ago, I found a deal on a 1988 27-foot class C on the Ford E350 platform. It only had 53K on the odometer, ran perfectly, and everything worked; $4k cash; I couldn't pass it up. It was old tech, and over time I've upgraded, and one thing was a new 15K BTU A\C unit I found on sale. The RV is about 160 square feet, close to a 20-foot trailer. Now, like you, I have a window unit, a 6K BTU GE with a thermostat for boon-docking, which will do the job, but the overhead unit is for running on shore power. I found a nice ten cu foot apartment-sized fridge to replace the old 12/120v/propane unit. It was a shoe-horn fit but worth it.

I was browsing Will Prowse's forum/website when I found a thread from a Chin factory rep in Northern California in November last year. These batteries were selling on Amazon for $650 at the time with free shipping because of my Prime membership. She returned with a bid of $600 each with free shipping to my door. I couldn't beat it with a stick. I went with Chin 12-volt 200 Amp-hour LiFePO4; four configured 2S2P for 400 Amp-hours at 25.6-volts. That's 10.24kW of storage. You would be hard-pressed to build a 12-volt 100 Amp-hour, including a 100 amp BMS for $600. And no, I could give a "flying blank" if they're A or B-grade cells, they are great batteries, as are some others just like them. I know several people who did the same at different times, and all like them and have no issues. They came fully charged, packaged well, and had all kinds of documentation. They even threw in a sweet 15-amp charger.

I went with the Giandle 24-volt 4000w pure sine wave unit for my inverter. During the day down here on the beach in East Texas, with all three solar arrays charging, I can run the overhead 15K BTU A/C with no problem during the day and throw something in the microwave simultaneously. She doesn't blink. Flat out at 4000 watts at 120 volts; you only pull 165 amps from the batteries on the 24-volt side. Do the math, and you will quickly see the amperage at 12 volts. At 12 volts, you'll never draw the total 1280 watts from a 100 amp-hour battery. Because you can discharge at 1C doesn't mean you should in my book.

I'm an old retired engineer who likes to live comfortably out in the middle of nowhere away from people with all the comforts of home. I'm in Houston now, staying with my brother and doing upgrades. Gas is a bit costly right now, especially with a big block 460. I'll post pictures sometime when I have her looking pretty. She's a bit rough around the edges right now, but so am I. At my age, I've earned it. I've built a 3-foot rear bumper extension rear patio with all kinds of useful crap, including a sweet 4300w on gasoline and 3800w on propane duel fuel generator and slightly used on eBay for $500. My toad is a 2000 WJ Grand Cherokee with the Selec-trac 4x4 and 4.0 liter six; I love my Jeep.
 
ldsreliance stated that cheap batteries had grade B cells. You told him he was wrong... and then provided a bunch of "evidence" that doesn't support your claim.

So now you don't care... fine.

I think it's great that Chinese companies are making decent and inexpensive batteries now. Out of the box they work fine. The difference between grade B and grade A will generally show up as lower efficiency, faster degradation, and a higher failure rate. Since these batteries are supposed to last ~10 years we are a long way from having enough experience to say how good they are.
 
Ok in designing the trailer I would like to build, I'm stuck on the age old issue of power. I have a good background with 12v systems along with figuring out PV while I living in my Jeep. But for this trailer build should I start out with the 12v/100w panel, 100ah Lifepo4 battery, controller, DC-DC charger and 2000W inverter I currently have. Or upgrade to 24v to cut down on wiring sizing and costs and better power flow?

Subject to change specs depending on size of trailer I get plus budgeting:
3 panels from 300W@12v total to 360w+ if I go 24v
2x 100ah batteries... so either 200Ah@12v or 100Ah@24
won't use it much but would like at least a 1000W - 2000W inverter
switch for using shore power to charge and run 120AC while plugged in

Battery power will be running while we camp.
Fans to keep inside of trailer cool ( not living in it but for food storage and clothes)
Fridge either my current 12v compressor model or upgrade to something bigger maybe even a mini fridge ( hence inverter)
USB ports for phone charging
Lights for around tent and awning attach to trailer
possible water pump for sink and/or toilet

maybe a couple external connections for secondary moveable solar panel depending on how much sun hits top of trailer
Hello:
I'm running 24 Volt with 100Amp rated lipofe... 4 100 watt panels... and a 2000 watt inverter. I run a 24 volt mini fridge 24x7. Many small chinamade electronics are 12/24. My ceiling lighting is also 12/24 input rated.
If I connect to utility power(120V) I use an old x-box power supply with a boost converter to run into the MPPT with a automotive relay to select the panels or the boost converter.
I prefer 24 volt, bottom line.
 
Ok.....i asked for advice like most people. The back and forth opinions on differences between A and B aren't really needed. We all have our own opinions on them including me. To me they both have their own uses ( more intense usage I'd go for A while B are good fot lower usage and less power draw, enough of my opinion on them). So I'm asking that we keep it more towards advice on this. And I thank everyone so far that has offered it.
 
Welp, what it boils down to is the sellers on Amazon that I posted give the SAME 5 year warranty for HALF THE PRICE of the online seller above agruing with me. I for one, having TAUGHT basic electricity and electronics for the Navy back in the early 80s, while I was awaiting my class in nuclear power school, know quality when I see it at LOW COST vs a $25,000 toilet being sold to me. Pay what ya want, I'm LIVING the advice I give. I don't charge you 2x the price, it's free. Outta here.
 
UNo mas... Will Prowse paid OUT OF HIS OWN pocket for the AmpereTime, Chins and Zoom batteries, your HE gets paid for reviews doesn't count there. Lots of folks here have bought amazon batts, with NO problems. As you saw last year also on similar thread. I like to buy low cost, live my entire life that way, be 58 here shortly. I CERTAINLY am giving clear info, NOT to sell my expensive stock, lol.
 
Welp, what it boils down to is the sellers on Amazon that I posted give the SAME 5 year warranty for HALF THE PRICE of the online seller above agruing with me.
I think you just like to argue...

You were called out for making false statements... which you actually did. The "online seller above" did not make any false statements. Now you are backpedaling and pretending it was about something else. No one is arguing that the premium batteries are a better value except for the strawman you invented. They actually *could* be as far as you or anyone else knows (only time will tell).
 
Ok in designing the trailer I would like to build, I'm stuck on the age old issue of power. I have a good background with 12v systems along with figuring out PV while I living in my Jeep. But for this trailer build should I start out with the 12v/100w panel, 100ah Lifepo4 battery, controller, DC-DC charger and 2000W inverter I currently have.


My take:
  • 12v -> 24v DC-DC chargers are relatively rare
  • small 24v systems are relatively rare unless one is relying exclusively on inverters (greater efficiency when the voltage delta is lower)
  • DC-DC charging between TV and TT can be challenging
If this were for a van, class C, or similar all-in-one RV I'd say the 100w:100Ah DC-DC@12v setup above would be both practical and common. Not sure why the inverter is so big (no giant loads were mentioned) but if you own it then roll with it.

Since there is a trailer involved I would skip DC-DC and spend that money on more panel for the trailer, enough to support your loads offgrid. If you are married to the idea of DC-DC charging the trailer battery see this approach to injecting higher voltages into the 7pin.

maybe a couple external connections for secondary moveable solar panel depending on how much sun hits top of trailer

I'd put the portables on their own controller since they will be seeing different conditions.
 
Let's keep the focus on 12v vs 24v systems....Knowing about grade A and B lithium cells is important of course, but arguing over who sells or endorses either one (or not) is not very helpful to the OP when committing to a 12v or 24v design.

A new thread dealing with the subject of types and grades of lithium cells and batteries might be a good idea if someone wants to do that.
 
I think you just like to argue...

You were called out for making false statements... which you actually did. The "online seller above" did not make any false statements. Now you are backpedaling and pretending it was about something else. No one is arguing that the premium batteries are a better value except for the strawman you invented. They actually *could* be as far as you or anyone else knows (only time will tell).
WHERE in my posts have you saw a LIE? Your reading comprehension us at 3rd grade level.
 
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