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

[Johnxhc]

In the process of designing 1,200w system for my motorhome

I already decided to use 24v battery system.

Should I use 24v batteries in parallel connection or use 12v batteries series & parallel connections to construct the 24v system? does it make any difference at all either way?

All batteries are identical and will be purchase same time.

 

Any pro and cons?

Please advise.

 

Thanks!

[GlennWest]

What kind of batteries you planning on?

[Johnxhc]

Lithium 

[Nwcid]

The only thing that I can think of off the top of my head is that if you go with 24v batteries then you will have to have at least 1, possibly more depending on your design, DC converters down to 12v.  

If you go with 12v batteries then you could still use the 24v for charging the whole bank, but be able to wire your 12v stuff directly to the batteries.  

[oldjohnt]

John, there can be pros and cons so you have to decide what works best for you. I bet you already know most of this, but here goes regardless:

1) If you use 24 volt batteries versus two twelves in series THATS ONE LESS CONNECTION TO DEAL WITH

2) Some brands of 12 Volt Lithium batteries ARE NOT APPROVED TO BE USED IN SERIES to get the desired 24 Volts.

3) If you go with all 24 volt, you need another component, a 24 to 12 converter for powering the RV 12 volt loads and appliances

4) If you use two twelves in series and want to tap 12 volt loads off each, sure it can "work" but maintaining load balance and grounding so one isn't doing most of the work and the other slacking could be a concern.

5) If it were me I think Id go with straight single unit 24 Volt batteries (as many as needed wired in parallel) and just use a 24 to 12 Converter (common device) to power the 12 volt loads.

6) I would configure my multi panel solar array (series /parallel or whatever it takes) at 48 volts (Vmp higher)  and use a (if suitable unit available ????) Lithium compatible MPPT Smart charge controller to charge the 24 volt battery bank. 

7) You also need a Lithium compatible 120 VAC Charger that can charge your 24 volt batteries and I guess you will use an Inverter??? and if so I'd consider a Combination Inverter/Charger, perhaps a hybrid pass through ???? 

Sounds like you're doing your homework CONGRATULATIONS. I have a relatively small 29 Ft Class with modest energy needs and I'm running 1080 Solar watts and using three 12 Volt AGM's in parallel and get by just fine powering ALL EXCEPT AC.

Best wishes, God Bless and keep you safe

John T   NOT a Solar expert so see what the other fine gentlemen have to say

[GlennWest]

I'd just wire the lithium anyway you can to get 24v. I went 48v with mine. Just get the inverter for whatever voltage you wire for. Higher the voltage the less amps so wiring smaller, fuses smaller, etc

[Johnxhc]

4 hours ago, GlennWest said:

What kind of batteries you planning on?

Battle born.

I am thinking about 48v, but the mttp charge controller and inverter charge will cost minimum $800.00

Do you believe it is worth it? 

[GlennWest]

That price is very cheap. What are you asking about.

[Johnxhc]

2 hours ago, GlennWest said:

That price is very cheap. What are you asking about.

My bad, I mean $800.00 Extra, on top of $1,500.00 Victron MTTP charge controller & Victron Invert/Charger.

 

[oldjohnt]

8 hours ago, Johnxhc said:

I am thinking about 48v, but the mttp charge controller and inverter charge will cost minimum $800.00

Since you're talking about an MPPT charge controller I guess you are considering whether to configure your panels at 24 or 48 volts, right ????

Obviously 48 solar volts means there's less current down from panels to MPPT BUT IF THAT ALONE JUSTIFIES EXTRA COST that's a decision ONLY YOU CAN MAKE. I prefer and configured my panels at 48 volts but had it cost much more then 24 I may have changed my mind lol. My MPPT solar charge controller (for charging my 12 volt bank) accepts up to 100 Volts PV Input so deciding on 48 up top versus 24 was a no brainer in my case SINCE NO EXTRA COST regardless if 24 or 48 solar panel volts  BUT THATS FOR CHARGING MY 12 VOLT BATTERY BANK NOTTTTTTTTTTTTTTT  A 24 VOLT BATTERY BANK 

NOTE you indicated you decided on 24 Volt battery bank BUT IF THAT MEANS YOUR INVERTER CHARGER AND MPPT costs a lot more again ONLY YOU can make that decision.  Myself and others have offered opinions on the 12 versus 24 volt battery choice  BUT NOW THESE NEW COST FIGURES ADD EVEN MORE CONSIDERATIONS

if you need to use series battery connections check with Battle Born to see if that's okay !!!!!!!!!!!!!!!!!

Soooooooooooo are you still staying with 24 Volt batteries or due to extra cost (don't forget you also need a 24 to 12 converter if you go 24) or rethinking 12 ????????????????   YOUR CHOICE 

John T

[GlennWest]

Maybe John. His 110v converter will supply 12v as long as he has 110v. 

[oldjohnt]

2 minutes ago, GlennWest said:

Maybe John. His 110v converter will supply 12v as long as he has 110v. 

Yep the many typical 120 VAC Input Converter/Chargers are for charging 12 volt batteries and could feed 12 volt loads when plugged to shore power. I think he's torn between 12 or 24 volt house battery configuration???? As noted above there are pros and cons either way.

John T

[Shawn Patterson]

One advantage of going with a 24v or 48v system is that you can reduce the gauge of the wire you are using between your batteries and the inverter. This may or may not be an advantage depending on the length of your wire runs and how tight your installation area is.

Edited September 2, 2020 by Shawn Patterson

[jcussen]

16 hours ago, Johnxhc said:

In the process of designing 1,200w system for my motorhome

I already decided to use 24v battery system.

Should I use 24v batteries in parallel connection or use 12v batteries series & parallel connections to construct the 24v system? does it make any difference at all either way?

All batteries are identical and will be purchase same time.

 

Any pro and cons?

Please advise.

 

Thanks!

Just curious on why you think a 24 volt system would be better than a 12 volt system?

[GlennWest]

On a large system, it saves some problems. Amps get  too high. Smaller systems not so much. Amps are easy to manage. Helps with solar panels also. Controllers allow more wattage with 24v and even more with 48v.

Edited September 2, 2020 by GlennWest

[Johnxhc]

3 hours ago, oldjohnt said:

Since you're talking about an MPPT charge controller I guess you are considering whether to configure your panels at 24 or 48 volts, right ????

Obviously 48 solar volts means there's less current down from panels to MPPT BUT IF THAT ALONE JUSTIFIES EXTRA COST that's a decision ONLY YOU CAN MAKE. I prefer and configured my panels at 48 volts but had it cost much more then 24 I may have changed my mind lol. My MPPT solar charge controller (for charging my 12 volt bank) accepts up to 100 Volts PV Input so deciding on 48 up top versus 24 was a no brainer in my case SINCE NO EXTRA COST regardless if 24 or 48 solar panel volts  BUT THATS FOR CHARGING MY 12 VOLT BATTERY BANK NOTTTTTTTTTTTTTTT  A 24 VOLT BATTERY BANK 

NOTE you indicated you decided on 24 Volt battery bank BUT IF THAT MEANS YOUR INVERTER CHARGER AND MPPT costs a lot more again ONLY YOU can make that decision.  Myself and others have offered opinions on the 12 versus 24 volt battery choice  BUT NOW THESE NEW COST FIGURES ADD EVEN MORE CONSIDERATIONS

if you need to use series battery connections check with Battle Born to see if that's okay !!!!!!!!!!!!!!!!!

Soooooooooooo are you still staying with 24 Volt batteries or due to extra cost (don't forget you also need a 24 to 12 converter if you go 24) or rethinking 12 ????????????????   YOUR CHOICE 

John T

Here is why  I chose 24v, for VICTRON ENERGY 50A SMARTSOLAR MPPT 100/50 CHARGE CONTROLLER W/ BLUETOOTH, Cost $381.00

Nominal PV Power (12V System):  700W, Nominal PV Power (24V System):  1400W, so if I put 1,300w (I am thinking about 4 325w panels) solar panel with 12v,this is not big enough as it out has 700w unde 12v, so I have to buy this:

VICTRON ENERGY SMARTSOLAR MPPT 150/100-TR CHARGE CONTROLLER W/ BLUETOOTH 

 

cost  $924.00

 so more than $500.00 difference on MTTP charge controller alone. also I need 3,000w inverter/charger, that is 

VICTRON 12v inverter charger cost $1,679. while the  24v inverter charge cost $1,284.

another $400.00 saving, plus the cost of wires , taxes (CA), I think that is at least $1,200 saving with 24v

of course I have to do 24v to 12v converter, $141.00. Also 

Also when you consider the invert/charge or MTTP fail in the future, the cost to replace those will be much high if I go 12v 

It makes me almost wants to go 48v, the cost of 48v inverter/charge & MTTP is $800 more than 24v. So the cost of going 12v is almost the same as I go 48v, but going to 48v, I could increase my solar panel to 2,000w or even high wattage on solar panels later on, no to mention the wire size etc..

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

 

 

 

 

 

 

 

 

 

 

 

 

 

[jcussen]

2 minutes ago, Johnxhc said:

Here is why  I chose 24v, for VICTRON ENERGY 50A SMARTSOLAR MPPT 100/50 CHARGE CONTROLLER W/ BLUETOOTH, Cost $381.00

Nominal PV Power (12V System):  700W, Nominal PV Power (24V System):  1400W, so if I put 1,300w (I am thinking about 4 325w panels) solar panel with 12v,this is not big enough as it out has 700w unde 12v, so I have to buy this:

VICTRON ENERGY SMARTSOLAR MPPT 150/100-TR CHARGE CONTROLLER W/ BLUETOOTH 

 

cost  $924.00

 so more than $500.00 difference on MTTP charge controller alone. also I need 3,000w inverter/charger, that is 

VICTRON 12v inverter charger cost $1,679. while the  24v inverter charge cost $1,284.

another $400.00 saving, plus the cost of wires , taxes (CA), I think that is at least $1,200 saving with 24v

of course I have to do 24v to 12v converter, $141.00. Also 

Also when you consider the invert/charge or MTTP fail in the future, the cost to replace those will be much high if I go 12v 

It makes me almost wants to go 48v, the cost of 48v inverter/charge & MTTP is $800 more than 24v. So the cost of going 12v is almost the same as I go 48v, but going to 48v, I could increase my solar panel to 2,000w or even high wattage on solar panels later on, no to mention the wire size etc..

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

You do realize, that voltage down from panels has nothing to do with battery voltage, I have 1455 watts of solar running through two victron charge controllers. One string is 120 volts and the other is 60 volts. Output is still 12 volts from charge controllers. I have a 48 volt system on the house, and it works well, but when I looked at running the coach at higher voltages, found it was cost prohibitive. Don't know what kind of coach you have, but if you have a 12 air compressor or 12 volt hyd motors or 12 volt slide motors, all this must be added into you 12 volt loads.  Don't know if you have a converter or an inverter, but a converter alone may not be able to handle all your 12 volt loads, Plus charging from a 12 volt alternator requires added expenses. All my 12 volt electrical equipment is in one bay, so cost of wiring there was not a big factor. Because of the high voltage  coming from the panels, was able to use two runs of 10 gauge, easy to run, and I still have room for expansion.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[GlennWest]

Pardon me, the higher the battery voltage the more solar wattage you can run. 

[jcussen]

3 minutes ago, GlennWest said:

Pardon me, the higher the battery voltage the more solar wattage you can run. 

 

3 minutes ago, GlennWest said:

Pardon me, the higher the battery voltage the more solar wattage you can run. 

How so Glenn, know one Foretravel guy, that has 3000+ watts on the roof and he still runs a 12 volt system.  Depends on the solar controllers, believe he runs 3 Victron 150/100's.The higher the output voltage is, the greater the number of solar watts  the solar charger can handle, but by using several  controllers, outputting 12 volts is very possible.

 

[lockmup68]

and 24/48 is much more efficient than 12v. Especially if you are using dedicated 24/48v devices. 

[jcussen]

17 minutes ago, lockmup68 said:

and 24/48 is much more efficient than 12v. Especially if you are using dedicated 24/48v devices. 

Other than an inverter, what other dedicated 24/48 volt devices are used in a motorhome. I hear there are  some 48 volt ac's on the market, but have not seen one. Efficiency on a 48 volt inverter is about the same as a 12 volt one. Wiring will be smaller, of course, but if you have your controllers, batteries, and inverters in close proximity, and use the proper size wiring, can't see much difference.

[Johnxhc]

3 minutes ago, jcussen said:

Other than an inverter, what other dedicated 24/48 volt devices are used in a motorhome. I hear there are  some 48 volt ac's on the market, but have not seen one. Efficiency on a 48 volt inverter is about the same as a 12 volt one. Wiring will be smaller, of course, but if you have your controllers, batteries, and inverters in close proximity, and use the proper size wiring, can't see much difference.

Of course you have two charge controller! that is already the double the cost than one ::)

I am a little confused here, you say that  "... Output is still 12 volts from charge controllers. I have a 48 volt system on the house"

so the output from charge controller is 12v and the house battery system is 48 volt? I thought the output voltgage from the Charge Controller has to be high than the house battery system?

Also "All my 12 volt electrical equipment is in one bay, so cost of wiring there was not a big factor", assume the house battery system is 48v, how do you get the 12v without DC to DC convert?

 

Please advise.

Thanks.

[Kirk W]

12 minutes ago, Johnxhc said:

Of course you have two charge controller! that is already the double the cost than one ::)

I am a little confused here, you say that  "... Output is still 12 volts from charge controllers. I have a 48 volt system on the house"

so the output from charge controller is 12v and the house battery system is 48 volt? I thought the output voltgage from the Charge Controller has to be high than the house battery system?

Also "All my 12 volt electrical equipment is in one bay, so cost of wiring there was not a big factor", assume the house battery system is 48v, how do you get the 12v without DC to DC convert?

 

Please advise.

Thanks.

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

[jcussen]

12 minutes ago, Johnxhc said:

Of course you have two charge controller! that is already the double the cost than one ::)

I am a little confused here, you say that  "... Output is still 12 volts from charge controllers. I have a 48 volt system on the house"

so the output from charge controller is 12v and the house battery system is 48 volt? I thought the output voltgage from the Charge Controller has to be high than the house battery system?

Also "All my 12 volt electrical equipment is in one bay, so cost of wiring there was not a big factor", assume the house battery system is 48v, how do you get the 12v without DC to DC convert?

 

Please advise.

Thanks.

House is a separate 48 volt system on my house to charge my car and run fridges and freezers..  Sorry for the confusion. On coach am running two series strings, one at 120 volts down and one at 60 volts down. Solar charge controllers will take that high voltage and reduce it to what my batteries require, in my case 14.4 volts. My coach battery  system is 12 volts only, if I had a higher voltage would have to reduce it to handle the 12 volt loads and modify alternator charging to charge higher than 12 volt batteries.

Like I said, wanted a 48 volt system in my coach, but after figuring out all the extra cost associated with going back to the 12 volts the coach needs, found it not a fiscally practical. Your case may be different though. For my house higher voltage was more practical.

 

[jcussen]

8 minutes ago, jcussen said:

Agree about the black background.

 

 

Edited September 2, 2020 by jcussen