Multi use power idea

[Jcknorr]

Hi folks,

I am looking for advice on my choice to go with a 24 volt house battery over a 12 volt system. I know there are alot of threads around this but I have a very specific setup I am building and wanted to bounce this around and see if im missing anything. Here goes....

I have a 2015 toyota tundra sr5 that I am fitting with an MSJ vanguard camper system. I plan on doing moderate length off grid camping (probably 1 week without power at most) but also some fishing trips with my boat where I would stay for the weekend at a campground.

I have not bought any of the following yet but this is my thought on setup for power:

- renogy 12/24 volt 50 amp dc/dc charger and solar controller

- A 24 volt lifepo4 battery (not chosen yet but probably 100ah)

- at least 1 200w 24 volt solar panel fixed on camper

- one 200w foldable 24v solar pannel

- bluetti elite 100v2 power station (open to other suggestions)

So how i would use this system is for the truck or fixed solar to charge my 24 volt battery while driving. Once stopped I would switch to the portable solar panel if needed. The 24 volt battery would then in turn be used as a continuous charge for my bluetti, essentially using the bluetti as my inverter. The 24 volt batyery would give me a quicker more efficient charge from what i understand when plugged into the power station solar port. I would also at times remove the 24 volt battery if on a fishing trip and use it in my boat as a trolling motor battery.

I like the idea of the bluetti or a power station in general because there are times I may use the power station outside of the truck for other power needs.

I am not sure everything i will be powering yet since camping for long stretches with more than a tent is new to me. But right now I am planning on a hcalory diesel heater, electric cooler, camp lights, a radio and maybe some camp cookware possibly down the road but im fine with propane and fires for now.

I am open to any and all feedback on what you all use and if you think this setup will be sufficient. I feel like I have done all the math and planning and it should be more than enough but I may have missed something.

 

[grubworm]

ive built several solar systems for my camp trailers and even a smaller system to go in the camper shell of my Tundra. its hard to give exact advice on this because things are always going to be changing. I've upped my power numerous times over the years and currently have 600w of panels on top of our bigger camp trailer with 2 LiPO batteries of 280ah each.

just keep it scalable. the 24v is really nice because you can use smaller gauge wire since your amp draw will be half of that of a 12v system. I'm running 12v components, but really wish I went with 24v and eventually I'd like to go 48v just to keep the amps down. the electric cooler will be a decent size draw and depending on the size and ambient temp its working against, you might end up using around 20ah overnight. we use 12v fans and they will draw a good bit on higher speed. the diesel heater pump doesn't pull much, but its fan will pull a decent bit. I run my diesel heater off of its own 35ah battery and its been enough to run the heater all night with power left.

what you have sounds good and you can always add panels and up battery size if needs be. id recommend getting a good terminal block, like Blue Sea, (stay away from the cheap Chinese import stuff when dealing with this...they have a lot of junk that will overheat and cause problems) and have it set up where you can easily add circuits. you will want your electric cooler on its own circuit with a decent size wire gauge feeding the outlet for it. you can always add panels or go with 300w panels that will take up less space.

our last trip was very overcast and I had a hard time fully charging batteries, so that is also why I like to have the bigger capacity...never know when it will be cloudy and you cant get a good charge. I do have all my panels mounted to the roofs so that I can charge when traveling. some folk only go with folding panels and if you drive all day and set up at night, not sure when you are going to be able to charge batteries. I take a folding panel for just in case and I can use it while at camp to speed things up.

the power stations are nice...I have 2 I take and they are great for setting up on a picnic table or away from your rig and have power for lights and fans or for charging phones and laptops, etc. I take cordless tools with me and the power station has the built in inverter for 120v so I can plug in my battery charger for 18v batteries.

sounds like you have a good set up. you will grow and use more power over time, its pretty much inevitable, so just keep it scalable where its easy to up your panels and batteries and don't go with any cheap import components...DC is low voltage, but very high amps and crappy cheap components will not last and might even cause a fire.

also, not a bad idea to get a battery monitor. they use a shunt that will wire to the negative terminal of the battery and basically everything goes thru the shunt so it can monitor the power leaving as well as the power coming in to give an accurate reading of the battery. I highly recommend one of these added to your system.

 

[Kent R]

ive built several solar systems for my camp trailers and even a smaller system to go in the camper shell of my Tundra. its hard to give exact advice on this because things are always going to be changing. I've upped my power numerous times over the years and currently have 600w of panels on top of our bigger camp trailer with 2 LiPO batteries of 280ah each.

just keep it scalable. the 24v is really nice because you can use smaller gauge wire since your amp draw will be half of that of a 12v system. I'm running 12v components, but really wish I went with 24v and eventually I'd like to go 48v just to keep the amps down. the electric cooler will be a decent size draw and depending on the size and ambient temp its working against, you might end up using around 20ah overnight. we use 12v fans and they will draw a good bit on higher speed. the diesel heater pump doesn't pull much, but its fan will pull a decent bit. I run my diesel heater off of its own 35ah battery and its been enough to run the heater all night with power left.

what you have sounds good and you can always add panels and up battery size if needs be. id recommend getting a good terminal block, like Blue Sea, (stay away from the cheap Chinese import stuff when dealing with this...they have a lot of junk that will overheat and cause problems) and have it set up where you can easily add circuits. you will want your electric cooler on its own circuit with a decent size wire gauge feeding the outlet for it. you can always add panels or go with 300w panels that will take up less space.

our last trip was very overcast and I had a hard time fully charging batteries, so that is also why I like to have the bigger capacity...never know when it will be cloudy and you cant get a good charge. I do have all my panels mounted to the roofs so that I can charge when traveling. some folk only go with folding panels and if you drive all day and set up at night, not sure when you are going to be able to charge batteries. I take a folding panel for just in case and I can use it while at camp to speed things up.

the power stations are nice...I have 2 I take and they are great for setting up on a picnic table or away from your rig and have power for lights and fans or for charging phones and laptops, etc. I take cordless tools with me and the power station has the built in inverter for 120v so I can plug in my battery charger for 18v batteries.

sounds like you have a good set up. you will grow and use more power over time, its pretty much inevitable, so just keep it scalable where its easy to up your panels and batteries and don't go with any cheap import components...DC is low voltage, but very high amps and crappy cheap components will not last and might even cause a fire.

also, not a bad idea to get a battery monitor. they use a shunt that will wire to the negative terminal of the battery and basically everything goes thru the shunt so it can monitor the power leaving as well as the power coming in to give an accurate reading of the battery. I highly recommend one of these added to your system.

Good stuff in this reply, thanks.

 

[Jcknorr]

Thanks for all the feedback. We're you suggesting a stepdown and a terminal block for plug ins? I have been thinking about that for added usability. And then i am guessing you mean from the stepdown you would suggest a separate plug wired soley for the cooler so it doesn't have other things in the circuit?

 

[smritte]

24v-12v converters are common. They are normally called "Buck Converters" with 12-24 being called "Boost Converters". Cost is based on current and quality.
Charging a 24v battery using a buck converter will work but depending on the battery charge rate the converter can be costly. The down side is unless you really search, the converter will only be 24V. You need around 29V to charge a 24V Lithium Iron. Amperage wise, If you were charging an AGM or L/A the max charge rate is ~25A. I've had lithium's that would only charge around 10A and I've had some that can charge as high as 100A. The charge amperage is going to be based on how they built the battery. A proper charge controller for that will be very expensive. You could also do what I do. I have my alternator charging slightly higher and my solar tops off the batteries. If I was doing 24V, I would use a good Boost converter to keep it at 24 and a permanent solar to bring it up higher. Lithium's don't care if their slightly undercharged. 80% charge is fine but you only get 80% power minus 10% because you cant run them to zero. Having a good charge controller bringing them up to 90+ is a bonus but, I think I saw you wanting to run a folding panel. A 100w 24V panel on paper is 4A. In reality it will be less due to normal loss even if its in direct sunlight. I have 380w on my trailer and I get a pretty consistent 20A ish as 12V. Obviously in direct sunlight.
Bottom line there is, If you cant get a good charge controller for 12v-29v, you need to calculate at 70% what the AH is. On that, how fast the battery charges is based on how much it will accept and the charge controller output. Having a 100a controller isn't going to charge 100a if the battery only accepts 10A. The same applies the other direction. If you were running L/A or AGM, I could calculate charge time easily because its a chemical thing and the numbers are set. Lithium's have too many variables. BTW, Lithium's don't like to be charged too fast either, unless their designed for it. Slower charge means longer charge time.

You need to start with calculating how much power you need, base your battery size off of that and research the different batteries to match how your charging them.
The 24V being better is, but isn't true. Yes, the current is half, power loss in the wiring is half (ish) but now to keep everything efficient, you need all 24V accessories. Now you bring back the loss converting 24V to 12V and alternator charging 12V-24V. The conversion loss is dependent on which converters you run. The loss converting may be more than your saving with a 24V system. If your truck and everything you power was 24V, that's different. If vehicles were 24V we would have less issues with connectors, wiring, volt drop and corrosion wouldn't be as big of a factor. This is why the Military ran 24V forever.

Solar wise. I run 24V which actually ends up being somewhere between 24V-32V. 30V (ish) to my charge controller and its dropped to 12V there. I've built enough systems to see how much higher my loss is if I run 12V panels.
My experience with matching specs on a 12V battery and a 24V battery, you end up with close the same wattage when all is said and done. 12V, 100a is going to be around 24V, 50A for the same case size.
Draw it all up and weigh your options. Its a great idea just do the research before you buy anything.

 

[CATCOP]

So far I don't get any advantage to go 24V when we in USA sing on 12V. I just got the Bulette 200 and it's little brother the 50, they can charge off the vehicle or solar or 110 AC. My trolling motor was 12VDC, so I must be missing something.

 

[grubworm]

Thanks for all the feedback. We're you suggesting a stepdown and a terminal block for plug ins? I have been thinking about that for added usability. And then i am guessing you mean from the stepdown you would suggest a separate plug wired soley for the cooler so it doesn't have other things in the circuit?

yes
I split my system into subsections and I guess you could say I wire backwards...I have my loads, such as a water pump, lights, 12v recepticle for fridge, USB charging ports, etc. I wire them up and run those wires to a central location. I then get a terminal block with fuse protection and hook up my loads to that, making as many circuits as I want. usually lights on one circuit, water pump on one, 12v fridge on one, etc...
all my loads are 12v and my terminal block is 12v and every circuit has its own fuse. that is a subsection where all circuits go to the terminal block and I can add more circuits as long as I still have available spaces on the block. everything from the block to the loads is 12vdc. now, I have my second subsection that is 12vdc power to the terminal block. I can get that from a 12v battery or from a 24v battery with a converter like @smritte just said. I can even get a 120vac converter that will take shore power and convert it to 12vdc so I can still run my 12v loads, but with a 120ac source.

I like redundancy and versatility, so I wire everything for 12vdc and then have options on how to get the 12vdc to the terminal block. I wire my set up so I can have solar coming in to charge the battery OR I can plug into my generator and charge my batteries that way and my inverter generator even has 12vdc output so I could just unhook the battery from the terminal block and wire the generator as the 12v input and basically run all my 12v loads from the generator as I charge the battery. I can also pull up at a campground or really anywhere that has 120ac and just plug in my converter and run all my 12v loads normally without draining the battery. a lot of RVs have a power control station that has a built in inverter that automatically switches from 12v battery over to the inverter the second you hook up shore power. not a new thing, but I just do my own simpler version of that.

having a 24vdc battery is nice because the current is cut in half going to the terminal block and I also run a 3kw inverter, and it pulls a LOT of current at 12v, so being able to half that current draw would be nice and allow smaller cables. also, and really important to me, is an air conditioner. there is a 24vdc mini-split ac unit for RVs that I am wanting to get and the higher voltage means less amp draw...especially on something like an ac where the compressor is going to be power hungry. I don't have the unit yet, but I have planned ahead wiring for it.

 

[grubworm]

So far I don't get any advantage to go 24V when we in USA sing on 12V. I just got the Bulette 200 and it's little brother the 50, they can charge off the vehicle or solar or 110 AC. My trolling motor was 12VDC, so I must be missing something.

its more for big loads. most 12v loads in an RV wont matter, but when you get into something like an air conditioner, a 24v unit will pull half the current of a 12v unit, meaning you can use smaller cables and see a huge difference in the amp draw. even my 3kw inverter would benefit from being fed 24v. look at golf carts...those motors have a lot of torque and pull a lot of current...they use 48v instead of 12v and the amp draw is reduced by a factor of 4. you can really see the benefit of higher DC voltage there