12v batteries or 24v batteries, this is a question.

[oldjohnt]

1 hour ago, Johnxhc said:

So I am now debating on 24v or 48v now...

Hey John, The plot thickens lol. First it was 12 versus 24, now its 24 versus 48 ??????? HEY THATS NOT BAD, ITS FUN TO DESIGN FOR THE BEST. It looks like you have done your homework and cost breakdowns. If COST ONLY is what matters fine, but engineering wise I like the higher operating voltages myself to reduce current. 

I'm unsure of your system or specs and if you choose multiple 24 Volt Solar Panels you can still configure them (series or parallel or series/parallel etc) for 24 or 48 and even more net voltage down (Vmp is higher) to your charge controller, and many of which accept up to 100 Volts PV input, so if the MPPT output can charge your 24 volt battery bank I don't understand how higher net voltage up top allows for MORE solar watts????????? I see how many watts you can put on your roof depending on your roof real estate instead of if you connect the panels at 24 or 48 volts ???

I congratulate you for researching and considering cost and other engineering factors before making your final decision. Whatever net  solar panel voltage you use is, of course, a different animal then deciding on what battery voltage you use. As long as your charge controller will handle the solar input voltage (say 24 or 48 or more) and charge your chosen battery voltage (12 or 24 or 48) and your Inverter/Charger will charge that same battery YOURE GOOD TO GO.......

Fun and interesting  chat, for us sparkies at least

 

John T

[hemsteadc]

2 hours ago, Johnxhc said:

so I am now debating on 24v or 48v now...

I have 48 and love it. Much smaller wiring, and I can run air without burning up wires and connectors running hundreds of amps. I have a Victron 48/12 converter which keeps the coach at a steady 12.8 all the time.  You do not want to be tapping one 12v battery in series for your 12v loads.

[GlennWest]

I have 21kwh of lithium. 48v is no brainier with this much battery. But smaller is debatable. As long as you can keep amps in a manageable amount, little benefit in higher voltage. 

[Johnxhc]

1 hour ago, Kirk W said:

Your black background sure makes what you post difficult to read.

I thought white on black is easier to your eyes :))

I didn't realize that background got carried over after the post.

Just check with two other discuss forums, my post is black on white just like everyone else, only this forum is different, the admin should be able  change it so the individual's background does not get carried over.

Now I am using white background only for this forum.

 

[Johnxhc]

53 minutes ago, oldjohnt said:

Hey John, The plot thickens lol. First it was 12 versus 24, now its 24 versus 48 ??????? HEY THATS NOT BAD, ITS FUN TO DESIGN FOR THE BEST. It looks like you have done your homework and cost breakdowns. If COST ONLY is what matters fine, but engineering wise I like the higher operating voltages myself to reduce current. 

I'm unsure of your system or specs and if you choose multiple 24 Volt Solar Panels you can still configure them (series or parallel or series/parallel etc) for 24 or 48 and even more net voltage down (Vmp is higher) to your charge controller, and many of which accept up to 100 Volts PV input, so if the MPPT output can charge your 24 volt battery bank I don't understand how higher net voltage up top allows for MORE solar watts????????? I see how many watts you can put on your roof depending on your roof real estate instead of if you connect the panels at 24 or 48 volts ???

I congratulate you for researching and considering cost and other engineering factors before making your final decision. Whatever net  solar panel voltage you use is, of course, a different animal then deciding on what battery voltage you use. As long as your charge controller will handle the solar input voltage (say 24 or 48 or more) and charge your chosen battery voltage (12 or 24 or 48) and your Inverter/Charger will charge that same battery YOURE GOOD TO GO.......

Fun and interesting  chat, for us sparkies at least

 

John T

Hi,John, 

Maybe I misunderstand the Victron MTTP requirements ?

Here is my understand, please correct me if I am wrong (I have not bought the charge controller  yet, still have to time to switch).

The Inverter/Controller I am looking at is Victron Energy 50A SmartSolar MPPT 100/50 Charge Controller w/ Bluetooth

Nominal PV Power (12V System):  700W
Nominal PV Power (24V System):  1400W

My understanding is if my RV battery system is 12v, it will only put 700w to the system, if my RV battery system is 24v it will be able to  put 1400w to the system.

Or the 12v , 24v is refer to the voltage on the Solar panel side???
 

Please advise.

 

 

 

[hemsteadc]

40 minutes ago, Johnxhc said:

?Or the 12v , 24v is refer to the voltage on the Solar panel side???

Google up the picture and it's printed right on the controller.  I think I'd want something higher then, I mean than 100v on the PV side.

Edited September 2, 2020 by hemsteadc

[GlennWest]

27 minutes ago, Johnxhc said:

Hi,John, 

Maybe I misunderstand the Victron MTTP requirements ?

Here is my understand, please correct me if I am wrong (I have not bought the charge controller  yet, still have to time to switch).

The Inverter/Controller I am looking at is Victron Energy 50A SmartSolar MPPT 100/50 Charge Controller w/ Bluetooth

Nominal PV Power (12V System):  700W
Nominal PV Power (24V System):  1400W

My understanding is if my RV battery system is 12v, it will only put 700w to the system, if my RV battery system is 24v it will be able to  put 1400w to the system.

Or the 12v , 24v is refer to the voltage on the Solar panel side???
 

Please advise.

 

 

 

Yes if 12v you can only have 700 watts of solar. If 24v 1400 watt solar. And if it 48v caplable 2800 watt of solar. As long as amps are within limits 

[oldjohnt]

33 minutes ago, Johnxhc said:

The Inverter/Controller I am looking at is Victron Energy 50A SmartSolar MPPT 100/50 Charge Controller w/ Bluetooth

Nominal PV Power (12V System):  700W
Nominal PV Power (24V System):  1400W

My understanding is if my RV battery system is 12v, it will only put 700w to the system, if my RV battery system is 24v it will be able to  put 1400w to the system.

Or the 12v , 24v is refer to the voltage on the Solar panel side???

Hi again John, here's my take on your question BUT NO WARRANTY CHECK WITH VICTRON and the experts and the Big Boys,  all I have is a little 1080 watt system and 12 battery volts........

If the MAXIMUM CURRENT the controller can pump out is 50 amps and at 14 charging volts for a 12 volt battery 14x50=700 Watts

If the MAXIMUM CURRENT the controller can pump out is 50 amps and at 28 charging volts for a 24 volt battery 28x50=1400 Watts

So if indeed the MAXIMUM CURRENT is 50 amps on the controllers battery charging output, YES your understanding is correct

And if the MAXIMUM PV Input Voltage it can accept is 100 Volts, then I think you're limited to a net 48 volt solar since depending on the suns intensity and angle  my 48 volt panels may send 70+ volts down into my controller but never over 100

IE That charger can ONLY DELIVER 50 amps and that's true for a 12 or 24 (maybe even a 48) volt battery bank. I dont know if that Victron controller will charge a 48 volt bank ?????????????????? I think it s 12 or 24 ONLY, data sheet says that, must be true !!!!

If you need more charging amps YOU MAY NEED A BIGGER CONTROLLER (or use multiples, I've seen that)  because even if you have more solar that Victron controller can still only pump 50 charging amps (and I think 24 volt battery is max) even if you had wayyyyyyyyyy more solar capacity up on the roof.

Warning this is getting over my pay grade and is much more of a system then my little Class C 1080 watt 12 volt 50 amp MPPT system has CHECK WITH THE BIG BOYS although I "think" Im correct which isnt worth a lot lol

John T

[jcussen]

42 minutes ago, Johnxhc said:

Hi,John, 

Maybe I misunderstand the Victron MTTP requirements ?

Here is my understand, please correct me if I am wrong (I have not bought the charge controller  yet, still have to time to switch).

The Inverter/Controller I am looking at is Victron Energy 50A SmartSolar MPPT 100/50 Charge Controller w/ Bluetooth

Nominal PV Power (12V System):  700W
Nominal PV Power (24V System):  1400W

My understanding is if my RV battery system is 12v, it will only put 700w to the system, if my RV battery system is 24v it will be able to  put 1400w to the system.

Or the 12v , 24v is refer to the voltage on the Solar panel side???
 

Please advise.

If your solar output is 700 watts at 12 volts  you will put 700 watts into your 12 volt batteries. The same 700 watt input will be  700 watts into your 24 volt batteries, the advantage of higher volt batteries, is that you can use one smaller controller.  Several controllers will do the same thing at 12 volts.  Which ever way you go, there is no free lunch, 1000 watts of solar will only produce 1000 watts of power to your batteries, no matter what your voltage.

It is up to you to determine whether the cost of another controller will negate the extra gear you will need to supply 12 volts to your coach and how to charge your 24 volt batteries off a 12 volt alternator.

In my case it was cheaper to stay 12 volts and buy another controller, plus I like the fact that if one controller goes down, still have production  from the other.

Good luck on whichever way you go.

 

42 minutes ago, Johnxhc said:

 

 

 

 

[oldjohnt]

John, here's a PS

Not knowing your roof space or how many solar watts you end up with, that 1400 Watt controller delivering 50 amps into 24 battery charging volts (50 x 28) may ??? be big enough, if not surely two of them (2800 Watts) will.

Here's my reasoning. Subject to geographic location, time of year and suns intensity and angle BIG FACTORS you may only get perhaps say 70% of the effective charging watts pumped into your battery of the solar watts flat mounted up on a roof. For Florida winter camping about the most charging watts I get from my 1080 flat rooftop watts of solar is 700 watts. YOU MAY GET MORE OR LESS, IT DEPENDS ON SUN AND ANGLE AND TIME OF YEAR AND LOCATION   Don't anyone have a calf lol

Therefore, for that Victron controller to deliver 1400 watts of charging, that may equate to like 2000 watts of solar panels up on a flat roof SO HOW MUCH ROOF SPACE DO YOU HAVE AND HOW MANY SOLAR WATTS ARE YOU PLANNING  ???????? If you need that much you must be building a system capable of running an AC unit for X time, are you ??????????

What Im saying is a single 50 Amp MPPT controller that can pump 1400 watts into your 24 volt battery bank might???????????? be enough for say 1500 to 2000 watts of solar panels ???????????  

I can envision at least four up to perhaps six 300 watt panels up on your roof (1200 to 1800 watts) and if so that 1400 watt controller could (in theory at least subject to sun) get you by charging a 24 volt battery bank.

So now???? How many Amp Hours of batteries are you planning???  Im thinking 48 volts up top and 24 volt batteries at this time WHAT ARE YOU THINKING AT THIS TIME????

Gee its fun spending YOUR money lol 

John T

[Johnxhc]

2 hours ago, jcussen said:

 

 

You just opened my eyes, yes, now I think about it,  it does make sense to have two charge controller and keep the battery at 12v!!! 

I think this is what I am going to do.

Thank you!

[Johnxhc]

1 hour ago, oldjohnt said:

John, here's a PS

Not knowing your roof space or how many solar watts you end up with, that 1400 Watt controller delivering 50 amps into 24 battery charging volts (50 x 28) may ??? be big enough, if not surely two of them (2800 Watts) will.

Here's my reasoning. Subject to geographic location, time of year and suns intensity and angle BIG FACTORS you may only get perhaps say 70% of the effective charging watts pumped into your battery of the solar watts flat mounted up on a roof. For Florida winter camping about the most charging watts I get from my 1080 flat rooftop watts of solar is 700 watts. YOU MAY GET MORE OR LESS, IT DEPENDS ON SUN AND ANGLE AND TIME OF YEAR AND LOCATION   Don't anyone have a calf lol

Therefore, for that Victron controller to deliver 1400 watts of charging, that may equate to like 2000 watts of solar panels up on a flat roof SO HOW MUCH ROOF SPACE DO YOU HAVE AND HOW MANY SOLAR WATTS ARE YOU PLANNING  ???????? If you need that much you must be building a system capable of running an AC unit for X time, are you ??????????

What Im saying is a single 50 Amp MPPT controller that can pump 1400 watts into your 24 volt battery bank might???????????? be enough for say 1500 to 2000 watts of solar panels ???????????  

I can envision at least four up to perhaps six 300 watt panels up on your roof (1200 to 1800 watts) and if so that 1400 watt controller could (in theory at least subject to sun) get you by charging a 24 volt battery bank.

So now???? How many Amp Hours of batteries are you planning???  Im thinking 48 volts up top and 24 volt batteries at this time WHAT ARE YOU THINKING AT THIS TIME????

Gee its fun spending YOUR money lol 

John T

John,

I am in Southern California so we do got plenty of sunshine here, I am thinking about 4 325w panels on the rooftop, I just ordered 6 12v battle born batteries 100ah, will order charge controllers and invert/charger tomorrow.

it does make sense to have two charge controllers and keep the battery at 12v in my case.

It is so nice at this stage you can just change just change the design without any consequences ::)

Thank you for all your help.

I learned so much here, your guys are great!

[GlennWest]

8 minutes ago, Johnxhc said:

John,

I am in Southern California so we do got plenty of sunshine here, I am thinking about 4 325w panels on the rooftop, I just ordered 6 12v battle born batteries 100ah, will order charge controllers and invert/charger tomorrow.

it does make sense to have two charge controllers and keep the battery at 12v in my case.

It is so nice at this stage you can just change just change the design without any consequences ::)

Thank you for all your help.

I learned so much here, your guys are great!

Just remember big cables with 12v. 

[Johnxhc]

7 minutes ago, GlennWest said:

Just remember big cables with 12v. 

Yes, that will be my next question, how big? with 6 12v battle born connected parallel, 2400w inverter/charger. 

I assume meme all my existing cable (factory provided, such as level jack, slide , cable to 12v panel, alternator cable) will NOT need to be changed, they will be directly connected to the Busbar. Please correct me if I am wrong here.

so the thick cable we are talking about her is between the batteries, battery to Inverter, charge controllers to busbar etc, to fuses? is 2 gauge good enough?

[GlennWest]

Your inverter will say what size cable you need. And that will be the size you need to connnect batteries also. And I serously doubt 2 guage will be enough. Now from solar controller depends on amps you bringing down.

Edited September 3, 2020 by GlennWest

[oldjohnt]

56 minutes ago, Johnxhc said:

I am in Southern California so we do got plenty of sunshine here, I am thinking about 4 325w panels on the rooftop, I just ordered 6 12v battle born batteries 100ah, will order charge controllers and invert/charger tomorrow.

it does make sense to have two charge controllers and keep the battery at 12v in my case.

Good plan John, with 1300 watts of solar and TWO of the Victron 700 Watt controllers (those totaling 1400 watts will be plenty) into 600 Amp Hours of 12 Volt batteries, that's a pretty good overall balanced system. And you can even probably run an AC unit for a  limited time but I would definitely install a Soft Start on the AC. That many Battle Borns could stand much more charging current, but hey 1300 solar watts is darn good 

 Good thing you're staying at 12 volts, its a standard, you don't need a 24 to 12 DC Converter, I don't think you can series two 12 Volt Battle Borns anyway (would have to buy their 24 volt batteries) . 

WIRE SIZE

1) Of course the closer the Inverter is to the battery bank the better to reduce line voltage drop

2) Line voltage drop is a function of DISTANCE,,,,,,,,,,WIRE SIZE,,,,,,,,,,CURRENT

3) Lets do the math:

    Even if you may not fully load it,  2400 Watts being drawn from the batteries to the Inverter at lets use 12 battery volts = 200 Amps but the Inverter IS NOT 100% efficient

 Based on the length and due to inverter inefficiency, to be on the safe side Id be looking at 4/0 stranded coper cable myself even if 3/0 may well suffice. I depends on distance and tolerable voltage drop, my 4/0 is ONLY a suggestion 

NOTE many just use a simple ladder to connect multiple batteries in parallel which sure "works" but if you want to achieve better load and charging balance among all those expensive batteries so some don't work harder and others slack so they age the same, take a look here:  http://www.smartgauge.co.uk/batt_con.html  It tests and shows how better connection methods greatly improves load and charge balance among multiple batteries, even if sure a simple ladder "works"

Glad to be of help, Im jealous now lol but my little system is fine for ALL EXCEPT AC

John T

 

   

 

Edited September 3, 2020 by oldjohnt

[jcussen]

44 minutes ago, Johnxhc said:

Yes, that will be my next question, how big? with 6 12v battle born connected parallel, 2400w inverter/charger. 

I assume meme all my existing cable (factory provided, such as level jack, slide , cable to 12v panel, alternator cable) will NOT need to be changed, they will be directly connected to the Busbar. Please correct me if I am wrong here.

so the thick cable we are talking about her is between the batteries, battery to Inverter, charge controllers to busbar etc, to fuses? is 2 gauge good enough?

In most cases, original wiring to 12 volt panels and loads will be fine, I also run 6 battleborn's and run 4 gauge from each battery to busbar. [limited by bms to 100 amps charge/discharge] My original wiring to inverter was 3/0 and with a heavy load got warm, so swapped it out to 4/0, but I have a 3000 watt inverter. Depending on how many amps are coming out of controllers, 2 gauge is probably overkill, I run 50 amps out of one controller and 30 out of the other and use 4 gauge. Alternator will not put out the 14.4 volts your BB's like, so you will probably need  a dc-dc charger if you want to fully utilize your alternator.  I use this one.

.https://www.invertersupply.com/index.php?main_page=product_info&products_id=195599&gclid=Cj0KCQjwhb36BRCfARIsAKcXh6EWPk4xNbhlFY07PT8CpAo8em9wmyCVK51xnT3J7MYeUBnuTIW 

With enough solar, you may be able to run one ac [with easystart] running down the road without running generator.

Don't forget a good battery monitor, very important with lithium, I like the BMV 712, bluetooth so no wires to run. Most Victron solar controllers are also bluetooth, so you can do settings and read amps and volts all from your phone.

Edited September 3, 2020 by jcussen

[oldjohnt]

53 minutes ago, Johnxhc said:

is 2 gauge good enough?

NO see my post above, I didn't know how to merge it in grrrrrrrrrrrrrr Dont forget about catastrophic fuse protection and master On Off switches rated for that  high current

John T

[RandyA]

After reading all the discussion and comments my take away is that you are making things much more complicated than they need to be. 

First, your coach was built to work off of 12 volts (actually 12.1-14.4).  Your lights, slides (if you have them), water pump, furnace, converter charger, refrigerator eyebrow, propane alarm and possibly more were designed for 12 volts DC - as was your wiring and fuse/breaker sizing.  You also have the engine side that is 12 volts and provides charge current when driving.  If you maintain the converter/charger on shore power you will still need a 12 volt battery connected to operate the slides.  Leave all of the OEM stuff alone.  Using buck converters to reduce 24 or 48 volts to 12 volts turns a lot of valuable power into unneeded heat.  Put 18 volt parallel connected panels on the roof with a MPPT controller and leave the rest of it alone. 

Now, if I understand correctly, you want the battery bank primarily to power a DC to AC inverter.  You also want to be able to recharge the inverter battery bank from solar.  Running two solar banks with two controllers is an acceptable method if you have an independently isolated inverter.  You can easily arrange this so switching all of your solar input to a single battery system for faster recharge is possible. So, how many watts do you want from your inverter?  If you are not trying to run air conditioning or an electric dryer from an inverter you will rarely need over 2000 watts at 120 volts with minimal load shedding and management - even if you have a residential refrigerator and occasionally warm your coffee in the microwave.  Pure sine wave inverters with internal chargers and transfer switches up to 2000 watts are inexpensive (by comparison) and quite manageable with 12 volts DC as an input.  This allows you to use readily available and inexpensive 18 volt solar panels for the rest of the real estate on your roof with the appropriate MPPT controller.  The need to go to 24 volt or 48 volt DC systems unless you need 220 VAC output (which you do not) is really a matter of available solar panels, inverters, batteries, how much 120 volt power you truly need, the time you are willing to put into the project and your pocketbook.

As I write this my wife has "Tool Time" on the telly in the background.  The show is a perfect example of how "we" as guys have a tendency to over engineer a system just because we can.  I encourage you to step back and take another look at what you are getting into.  I might add that I have picked up a tidy sum of retirement fun money from finishing over-ambitious electrical projects from boat and RV owners that got in over their heads and couldn't finish a project.  Yes, I do like Lithium batteries.  But, the cost of new ones is still pretty high.  Unless weight is a considerable factor I would even suggest taking another look at AGM's.  Again, a lot less expensive not only for the batteries but the charging and balancing electronics as well.  Lithium batteries could very easily outlast the life of your MH meaning you will not get "your moneys worth" out of them.  After experiencing a Lithium battery fire that destroyed our trailer (and almost us) 3 years ago I am understandably cautious in that regard.  I do have two 50 Ah 48 volt lithium batteries in my golf cart but park it well away from the fiver.  It also has a 48 volt DC motor.......not 12 volts.

Just my dollars worth.  You can't get anything for 2 cents any more. 🙂

Edited September 3, 2020 by RandyA

[oldjohnt]

13 hours ago, RandyA said:

Yes, I do like Lithium batteries.  But, the cost of new ones is still pretty high.  Unless weight is a considerable factor I would even suggest taking another look at AGM's.  Again, a lot less expensive not only for the batteries but the charging and balancing electronics as well.  Lithium batteries could very easily outlast the life of your MH meaning you will not get "your moneys worth" out of them.

GREAT POINTS AND DISCUSSION RANDY, From yet from another "Happily Retired" Electrical Engineer and 49 year RV owner, we basically agree, here are my thoughts:

  Sure Lithiums seem to be "the in thing" and fashionable nowadays (so one has bragging rights) and offer advantages such as,,,,,,,,,,, Much lighter weight,,,,,,,,,,,,,,,The possibility to discharge them deeper then 50%,,,,,,,,,,,,,Fast charging,,,,,,,,,,,,,,,,Supposed (if all works out as advertised ????) less cost per useable Life Cycles over the long run, etc. etc. Of course, the down sides are HIGH UP FRONT COST and the low temperature concerns.

 That being said, I chose AGM, the reasons being at my age I cant say I will be RVing many more years or will keep the same RV very many years IE may never gain any long term cost benefits to offset the initial high cost. If I were younger and know Id be using the same RV for 7 to 10 hears, weight was an issue, and iffffffffff I usually dry camp,  I WOULD BITE THE BULLET AND CHOOSE LITHIUM

 I think his decision to stay with a 12 volt battery bank versus 24 or 48 is reasonable as he avoids yet another component (24 to 12 Converter) although operating at higher voltages has advantages such as lower current and I prefer higher voltages WHERE PRACTICAL REASONABLE AND COST EFFECTIVE....... However WOW using 12 volt batteries requiring (based on actual load) 200+ Amps out of his battery bank to the Inverter is hefty indeed !!!!!!!!!!!!! although with adequate cables and protection is certainly "workable"  

 He hasn't told us of how he is going to configure (or what so called voltage, 12 or 24 or ???) his four panels ?? The method I chose for my four panels was to use "so called 24 volt" units wired in series/parallel so I send "so called 48 volts" down to my charge controller and on a typical day the Voltage I see  down from the panels to my controller is 70+ volts which works well for the many controllers that accept up to 100 PV input Volts. Having no idea of his loads or any energy audit I view his choice of 1300 flat rooftop solar watts as strictly HIS CHOICE and  "reasonable" (but all subject to loads and sunlight etc etc) to charge (based on sunlight, time and SOC) his 600 Amp Hours of batteries. Again not knowing his loads and use, 600 AH SURE SEEMS PLENTY and may be MORE then needed if he runs ALL EXCPET AC, but hey to run AC for a limited time Id rather have too much battery then too little. The thing I run into dry camping in many say Natl Forest camps IS THERE MAY BE A TOTAL SHADE CANOPY  so my 1080 watts isn't near as big as it sounds lol  Again, if there's roof room and in his budget Id rather have too much then to little solar

INVERTER SIZE if he needed to run ALL EXCEPT AC he might get by with a smaller 2000 (4000 peak) PSW Inverter like I chose HOWEVER again to run an AC his choice of 2400 watts "might" be in line subject to the AC and any Soft Start etc.  

Hey there's no necessarily right or wrong answer to some of this, its HIS RV HIS choice HIS budget maybe its different then a couple of us retired engineers may think LOL 

PS that's my "two cents" worth, and I'm NOT any solar expert by any means, I defer to them and the Vendors for their advice.

Pleasure sparky chatting with your Randy, looks like were on the same page. Hope our discussion helps John

John T   BSEE,JD

Edited September 3, 2020 by oldjohnt

[hemsteadc]

14 hours ago, RandyA said:

Using buck converters to reduce 24 or 48 volts to 12 volts turns a lot of valuable power into unneeded heat.  ny more. 🙂

Mine runs cool.  Running high wattage appliances at 12v creates a lot of unneeded heat. I think sometimes these 'efficiency' arguments go a bit over the top.

Edited September 3, 2020 by hemsteadc

[GlennWest]

I am runninng all my 12v from a buck converter. 48/12v 50 amp chinese brand. Runs cool. Which I ran #6 wire. Got a charger on battery.

[RandyA]

29 minutes ago, GlennWest said:

I am runninng all my 12v from a buck converter. 48/12v 50 amp chinese brand. Runs cool. Which I ran #6 wire. Got a charger on battery.

I will have to concede that you are basically correct in your observation and application.   "Buck" converters in today's market are typically designed to reduce higher input voltages to lower voltages through a FET switching transistor and LC  process where very little energy is wasted.  They are able to take (for example) a 24 volt 20 amp supply and provide an output of 12 volts at a level approaching 40 amps.  The Chinese "clone" market has made such devices relatively inexpensive.  This was not true with the family of original voltage reducing converters that relied on PWM and hypersil transformers with non-FET silicon transistors.  Those devices were not as efficient and much of the energy was lost in conversion as heat.  Still, NO converter is 100% efficient and losses are there - just as using a smaller gauge wire that heats up with a higher than rated current.  I personally do not like to use buck converters or load-up a project with an array of additional devices if I can facilitate a project without them.  Old school, maybe?  I do prefer voltage regulator IC's and/or buck converters when I need to maintain a constant peak voltage - but that is typically in small scale circuits.  I had the mantra "you can neither create nor destroy energy, only change it" drummed into my head for years - and I passed the same on to my students.  The caveat to that mantra was anytime you convert energy there is a loss.   I do have a buck converter on my 48 volt lithium powered golf cart to power the lights and horn.  Adding another low voltage system would have been foolish since one was not there to begin with.  I also have some small buck converters in the fiver tucked out of sight to preserve the life of Chinese LED's that are not internally regulated and fail quickly when the converter charger kicks up to 14.4 volts.  Even below their rated output they can run quite warm and need ample fresh air to keep them cool.  Glad to know your system is running working well and running cool.

[GlennWest]

Yes my choice was keep a seperate 12v battery and a charger for it or use the bulk converter.

[GlennWest]

Yes my choice was keep a seperate 12v battery and a charger for it or use the bulk converter.