RV 24v vs 12v redundancy...

filippomasoni

Solar Enthusiast
If I were you, I would get 8 more batteries and do 2x 24v packs.
That's overkill. From my energy audit, I'll have about 3 days of energy in the worst-case scenario without any sun or without moving the vehicle (I'll have a DC-DC alternator charger anyway). I'll bring a camping stove as a backup for extreme situations, without using the induction I can basically double my autonomy. I don't want to add too much weight and space as the camper is pretty small and I think 8 cells are already a lot.
 

DerpsyDoodler

Photon Sorcerer
That's overkill. From my energy audit, I'll have about 3 days of energy in the worst-case scenario without any sun or without moving the vehicle (I'll have a DC-DC alternator charger anyway). I'll bring a camping stove as a backup for extreme situations, without using the induction I can basically double my autonomy. I don't want to add too much weight and space as the camper is pretty small and I think 8 cells are already a lot.
Good call. What's the recommended fuse for your inverter?
 

jamiko

Solar Enthusiast
In my opinion if you want redundancy on 24v then you need two 24v packs. Switching back to 12v because a pack failed is headaches waiting to happen.

In hindsight, two 150AH 24V batteries running in parallel might have been better. Same Kwh, but added redundancy. Since you already bought the 304ah Lifepo4 cells, what about another smaller 24V battery. You could run in parallel and have smaller redundancy. I don't think they have to be 304ah. You could get 8 100ah.
 

emerge411

New Member
I decided to go with 12v. The 2400w/3000va Multiplus seems to run fine for many using 4/0 cable. Everything is located next to one another so the runs are very short. I will work on the install this fall. Shake down the system on some east cost trips summer of '22 and have time to make any adjustments before our trip west in the spring of '23. Current state of the plan below. I will share what I learn along the way.
 

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filippomasoni

Solar Enthusiast
Good call. What's the recommended fuse for your inverter?
I still don't know. As of right I only ordered the 8 cells, since it takes 2 months, and if there's any problem with those another 2 months. I'll start building the camper next year. Victron inverters seem to be the best ones, but very expensive and also bulky and heavy. I was also considering a Giandel 3000W, 2000W would be enough but since it's lower quality going to 3000w will probably give me some headroom. I'm in Europe and 240V models have different W output compared to US 120V.

I decided to go with 12v. The 2400w/3000va Multiplus seems to run fine for many using 4/0 cable. Everything is located next to one another so the runs are very short. I will work on the install this fall. Shake down the system on some east cost trips summer of '22 and have time to make any adjustments before our trip west in the spring of '23. Current state of the plan below. I will share what I learn along the way.
That's great, it's probably what I will end up doing as well. All my electricals will be close to each other so cable runs will be very short. Looking forward to your tests and experience. That looks great, very detailed plan!
 

DerpsyDoodler

Photon Sorcerer
I still don't know. As of right I only ordered the 8 cells, since it takes 2 months, and if there's any problem with those another 2 months. I'll start building the camper next year. Victron inverters seem to be the best ones,
They are considered (among a few others) top tier. Magnum, Outback, and Samlex (specifically their EVO line) are, as well.
but very expensive and also bulky and heavy.
Yes, all low frequency inverters >= 2000w will be large and heavy. This is because their components are different and that much larger and heavier. Consequently, this equates to better reliability and higher power output. it is worth it to find the space and weight capacity for them.
I was also considering a Giandel 3000W, 2000W would be enough but since it's lower quality going to 3000w will probably give me some headroom. I'm in Europe and 240V models have different W output compared to US 120V.
Good to know (you're European 240). I'll keep that in mind. I don't believe it changes anything i've already said.
 

filippomasoni

Solar Enthusiast
They are considered (among a few others) top tier. Magnum, Outback, and Samlex (specifically their EVO line) are, as well.

Yes, all low frequency inverters >= 2000w will be large and heavy. This is because their components are different and that much larger and heavier. Consequently, this equates to better reliability and higher power output. it is worth it to find the space and weight capacity for them.

Good to know (you're European 240). I'll keep that in mind. I don't believe it changes anything i've already said.
I'm not doubting the high quality of those brands and I'm sure they are heavy for good reasons. I did a quick search and can't seem to find those other brands sold in Italy, I'll dig deeper.
I really like Victron non only because of the quality but also the convenience of the apps etc and I'm planning to use mostly Victron stuff components: alternator DC DC, MPPT, shunt, battery monitor... But I found inverters to be so much more expensive than the "cheap stuff" I mean, not twice but 4-5 times more. I'm sure they are worth it, especially in a home environment where they are ON 24/7, but for a small camper where it'll be on for a max 2h per day (only for cooking) spending 1200 euro seem a bit too much. I'm trying to keep the budget reasonable and save some money. Giandel is used by many people and recommended by Will so I though that could be good enough. Do you know any other brand that's like in the middle between the top tier and the cheap stuff?
 

12VoltInstalls

Solar Addict
Just a thought since you’ve decided on 12V: why not skip the induction plate and use propane instead? A 20# cylinder goes a very long time and with a demand H2O heater that is another bennie.

Giandel has been good for me 3+ years but I probably have never had it see 1000W (it’s a 1200/2400”surge”) but that was my plan: never max it out for longevity. Bigger dollar transformer inverters probably not as much of a concern but still… it seems you’re building for the induction plate when propane is pretty cheap on the small scale.

I’m pretty happy with 12V but I see 24v or 48v for higher demand as making sense when I build permanent.

On the other hand, over the road 12V is much more easily cobbed up on the fly from auto parts stores and walmartha-type places - or in remote locations for that matter.

I like having native 12VDC and 120VAC available. (translate to 220 in your case I guess) However, you sorta have to make a plan and get committed to the higher voltage AC and build for it to drop 12VDC entirely. Unless…

If I were in your situation I might roll out a 200W 12VDC solar panel system into a couple (or one?) 12V batteries for what? $350/$400 or less and then build fir a robust small 48V LiFePo system for your inverted AC power needs and call it good. Treated properly, inexpensive 12V deep cycle lead acids can go 5 years or more.
THAT’S redundancy.
 

filippomasoni

Solar Enthusiast
Just a thought since you’ve decided on 12V: why not skip the induction plate and use propane instead? A 20# cylinder goes a very long time and with a demand H2O heater that is another bennie.
I've debated that for a while because many people suggested it ( even on this forum on my thread about 12 vs 24v ) and I know it's the most popular option because of price and simplicity. But I've wanted to go with induction since the begging and decided to go for it so I pulled the trigger on the 8 cells last week. Without the induction 4 cells would have been enough. So I'm set for that, and I agree with this:
If the decision was anything like mine, its because getting the propane in the first place is annoying.

You can heat water and cook with solar quite easily - if you have enough of it.
It gets more annoying in countries where it's not readily available, needs to carry a lot of adapters and definitely require to have at least 2 canisters to have a backup and carry a lot in many countries. It also takes a lot of space, even though I did the math and it's a lighter system than carrying twice as much batteries and big inverters.

Gas is also a cost and with a quick math I could probably repay for the extra electrical system in about 3-4 years, not accounting that in some cases I might need to travel a bit out of my way to go find gas.

Anyway I don't want to go off topic more than we already did and I'd like to keep the discussion on 12V vs 24V and redundancy.

OP decided to go with 12V because redundancy is great when traveling and I fully support that.

Someone mentioned that with Amy's cells there would be hardly any problems, and I ordered from her, so hopefully I'll get good ones. Even getting half of the cycles they are rated for (6000) they'll last more than 8 years.

If a cell was to go bad, should it show signs straight away? Or is something that can happen anytime?
The pack is matched by the produced, so if I tested them all top balance, capacity test and compress them properly they should last a long time. So technically there's a higher chance some other components will fail before cells right? Like the BMS, MPPT etc?
The more stuff there is and the more complex the higher the chances of something braking, cells are just a few materials doing a chemical reaction...

Just my thought, I might be wrong, but if this is the case than an 8S 24V configuration would be really nice, especially with an Electrodacus, and also a bit cheaper.
 

childcarepro

Solar Enthusiast
@emerge411, I support your decision.

Like you, I was decided on 24V, bought all my stuff except connection hardware (Victron 24|3000|70 + SmartSolar 100|50 + 6 x 200W 24V Newpowa panels + one 8S 280A 24V LiFePO4). Thank goodness I didn't install. So for now we're stil in a 2018 Winnebago Via with the stock flooded lead acid 12V 80Ah x 2 house bank. Long story short, our coach was bricked by the power wire falling out of our converter. Thank goodness I was able to find a great technician who was able to come right away, or our 2.5 wk vacation would have been over 2 days in!

Moral of the story is I never want to be that stuck again. And it's not just a fluke loose wire that could do this… we could be completely stranded with a single dead component: the single 24V battery OR BMS, fuse, etc. I had a rude awakening to the fact that almost anything in the electrical system can leave us stranded. So I'm switching to a 12V system. I have enough cells for three (3) 12V 4S batteries, each with its own 120A Overkill BMS (need 2 more 4S BMS's), so literally all 3 BMSes or batteries would have to fail for us to be completely dead in the water.I'm reducing the component count for fewer points of failure: a 12V system eliminates the 24-12V converter among other things.

What I love about a 12V system is you can start the engine with the house battery (battery boost), and not have to convert from 24V to 12V to have usable power for 12V appliances. Also, there are DC refrigerators/freezers and DC air conditioners that support 12 or 24V, but when it's only one voltage, it's always 12V (like the Dometic RTX 2000 12V DC air conditioner).
 

filippomasoni

Solar Enthusiast
@emerge411, I support your decision.

Like you, I was decided on 24V, bought all my stuff except connection hardware (Victron 24|3000|70 + SmartSolar 100|50 + 6 x 200W 24V Newpowa panels + one 8S 280A 24V LiFePO4). Thank goodness I didn't install. So for now we're stil in a 2018 Winnebago Via with the stock flooded lead acid 12V 80Ah x 2 house bank. Long story short, our coach was bricked by the power wire falling out of our converter. Thank goodness I was able to find a great technician who was able to come right away, or our 2.5 wk vacation would have been over 2 days in!

Moral of the story is I never want to be that stuck again. And it's not just a fluke loose wire that could do this… we could be completely stranded with a single dead component: the single 24V battery OR BMS, fuse, etc. I had a rude awakening to the fact that almost anything in the electrical system can leave us stranded. So I'm switching to a 12V system. I have enough cells for three (3) 12V 4S batteries, each with its own 120A Overkill BMS (need 2 more 4S BMS's), so literally all 3 BMSes or batteries would have to fail for us to be completely dead in the water.I'm reducing the component count for fewer points of failure: a 12V system eliminates the 24-12V converter among other things.

What I love about a 12V system is you can start the engine with the house battery (battery boost), and not have to convert from 24V to 12V to have usable power for 12V appliances. Also, there are DC refrigerators/freezers and DC air conditioners that support 12 or 24V, but when it's only one voltage, it's always 12V (like the Dometic RTX 2000 12V DC air conditioner).

I fully support that, redundancy is the key especially for long travels in remote areas.

Although like I said before if a cell was to go bad, shouldn't it show signs straight away? Or is it something that can happen anytime?
Technically there's a higher chance some other more complex components will fail before cells right? Like the BMS, MPPT, inverter, etc.
Of course, having 2 or 3 12V batteries like you're doing means redundancy even on the BMS side, so that's also covered and maybe in the case of 2 solar panels we could even go with 2 separate MPPTs
 

MattiFin

Solar Addict
They are considered (among a few others) top tier. Magnum, Outback, and Samlex (specifically their EVO line) are, as well.

Yes, all low frequency inverters >= 2000w will be large and heavy. This is because their components are different and that much larger and heavier. Consequently, this equates to better reliability and higher power output. it is worth it to find the space and weight capacity for them.

Good to know (you're European 240). I'll keep that in mind. I don't believe it changes anything i've already said.
I'm not so sure about low frequency inverters being "naturally" more reliable or capable of higher (peak) power output.
You could design the HF inverter to handle same peak loads as well... but it wouldn't be so cheap anymore.
You can also make crappy LF inverter but as it is expensive approach in any case it looks like we have only (mostly) high quality manufacturers left.
 

DerpsyDoodler

Photon Sorcerer
I'm not so sure about low frequency inverters being "naturally" more reliable or capable of higher (peak) power output.
You could design the HF inverter to handle same peak loads as well... but it wouldn't be so cheap anymore.
You can also make crappy LF inverter but as it is expensive approach in any case it looks like we have only (mostly) high quality manufacturers left.
naturally speaking? 🤔
 

Short_Shot

Photon Sorcerer
I'm not so sure about low frequency inverters being "naturally" more reliable or capable of higher (peak) power output.
You could design the HF inverter to handle same peak loads as well... but it wouldn't be so cheap anymore.
You can also make crappy LF inverter but as it is expensive approach in any case it looks like we have only (mostly) high quality manufacturers left.
As I understand it, the higher surge is inherent to the design requirements of a low frequency inverter.

I'm not sure what specifically but high surge time from a high frequency inverter means you essentially have to build it to a much higher rated output in the first place.
 

MattiFin

Solar Addict
As I understand it, the higher surge is inherent to the design requirements of a low frequency inverter.

I'm not sure what specifically but high surge time from a high frequency inverter means you essentially have to build it to a much higher rated output in the first place.
I was thinking of these low frequency inverter "myths" and I think the underlying reason is the very expensive output transformer in LF design.
Expensive-->Transformer size is selected to support the needed watts but no more than that. But thanks to being heavy lump of metal you can overload it severely.

On HF inverter the (hf) transformer is relatively cheap and not the limiting factor to even start with.
 

Short_Shot

Photon Sorcerer
I was thinking of these low frequency inverter "myths" and I think the underlying reason is the very expensive output transformer in LF design.
Expensive-->Transformer size is selected to support the needed watts but no more than that. But thanks to being heavy lump of metal you can overload it severely.

On HF inverter the (hf) transformer is relatively cheap and not the limiting factor to even start with.
Doing it with a digital system is definitely much cheaper than analog, that's for sure.
 

childcarepro

Solar Enthusiast
I fully support that, redundancy is the key especially for long travels in remote areas.

Although like I said before if a cell was to go bad, shouldn't it show signs straight away? Or is it something that can happen anytime?
Technically there's a higher chance some other more complex components will fail before cells right? Like the BMS, MPPT, inverter, etc.
Of course, having 2 or 3 12V batteries like you're doing means redundancy even on the BMS side, so that's also covered and maybe in the case of 2 solar panels we could even go with 2 separate MPPTs
Agreed, BMS, inverter, SCC are all more likely to fail than a LiFePO4 cell, especially if the battery cell is protected by a BMS. Fortunately, nothing is as crippling when it fails than the house battery (you lose functionality, not the use of your coach). Hence my focus on maximum redundancy on the battery/BMS, including the chassis battery as a backup battery of last resort (using the battery boost switch).
 

filippomasoni

Solar Enthusiast
I just realized there might be another important advantage of having 2x 12V batteries instead of 1x 24V.

I read here (at par. Other BMS-Induced Peculiarities & Problems) that after a low voltage disconnect, the BMS turns off and there's no way of turning it back on other than with an AC charger that can do “dead battery charging”. What does that mean?
In the case of a single cell going below the low voltage disconnect, we can't turn it back on with an MPPT or with DC-DC charger? That would mean having to find an AC outlet, which could be a problem if we are in a remote area for example.

In the article, it says that alternatively the battery can be jump-started with another battery. So heaving a 2x12V battery would solve the issue or it can also be jump-started with the starter battery of the vehicle if it's 12V.
 
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