12, 24, or 48v Van Preferred Power Systems?

[mercedesstern]

There are other opinions.

"In regards to the voltage limit, the DC limit is 60 V under dry conditions, and 30 V under wet conditions as specified in UL 1310, [4] intending to protect against the inability of let-go shock effects. This limit was selected with the intent to protect 95% of the population including children."

Shock Threshold

The UL 1310 standard is specifically for power supplies, where the user can attach wires to screw terminals under wet conditions. This is a different use case than a 48V wiring where electrical contacts are not exposed or could be touched accidentally.

 

[EBS-P]

However, if you’re just going to sit at a spot for a good while then you need to consider adding a generator

Why are not talking about this option more? Weight wise it’s probably the lightest option. Yes you would need to carry gasoline. how many days a year are you needing to run the AC more than 5 hours?

 

[EBS-P]

Is the battery connected to chassis? Then you have a potential dangerous situation.

Explain why?

 

[AH64ID]

Why are not talking about this option more? Weight wise it’s probably the lightest option. Yes you would need to carry gasoline. how many days a year are you needing to run the AC more than 5 hours?

That’s our plan, though we mainly foresee needing it for stationary winter use while skiing. The 7,680W battery may surprise us, but the plan in to drag along the Honda 2200 for those trips.

For summer, it’ll be rare that we’re off-grid and need the A/C more than a few hours a day… plenty for the 400W of solar. Our main A/C use will be at our remote lot with power, so it’s not an issue.

I’d love to find an EU1000 for van use, but not sure I want another engine to maintain and we need the EU2200 for the 5th wheel A/C.

 

[calbiker]

Explain why?

What's safer, a floating chassis or battery ground tied to chassis (hot chassis)? In the case of a hot chassis a person needs to get in contact with the positive polarity of the battery to get shocked. If chassis is floating then a person needs to contact both positive and negative polarities of the battery to get shocked. That probability that happens is far more remote. Working on the battery is also safer. I've seen tools get dropped, making contact with positive potential and chassis. The tool gets arc welded.

 

[AH64ID]

What's safer, a floating chassis or battery ground tied to chassis (hot chassis)? In the case of a hot chassis a person needs to get in contact with the positive polarity of the battery to get shocked. If chassis is floating then a person needs to contact both positive and negative polarities of the battery to get shocked. That probability that happens is far more remote. Working on the battery is also safer. I've seen tools get dropped, making contact with positive potential and chassis. The tool gets arc welded.

Are any of the second alternator options not Case grounded? Every one I have seen is case grounded, making it a moot point if you want a second alternator to charge your house bank.

 

[calbiker]

The UL 1310 standard is specifically for power supplies, where the user can attach wires to screw terminals under wet conditions. This is a different use case than a 48V wiring where electrical contacts are not exposed or could be touched accidentally.

UL 1310 has nothing to do with our discussion. The link I posted shows your human body resistance value is not correct when protecting 95% of the population including children. Wet conditions are common in a rv, coming in from the rain, take a shower, spill some water, etc.

 

[mercedesstern]

UL 1310 has nothing to do with our discussion. The link I posted shows your human body resistance value is not correct when protecting 95% of the population including children. Wet conditions are common in a rv, coming in from the rain, take a shower, spill some water, etc.

I read the article you linked. The experiment was to determine the resistance of the human body at voltages below 60V. They did not make conclusions about safe voltages, they only refer to this UL standard (the part you even quoted) for that, which limits power supplies for wet conditions to 30V (UL 1310).

Wet conditions exist in vans, per instance they do under a shower, but proper techniques make sure, that higher voltages are not dangerous. A proper 48V supply in a van should not have exposed screw terminals where you can attach stripped wires, like these UL listed power supplies allow. We have higher voltages in a lot of places where humans are close, it is wet, but not dangerous. It's not the voltage limits that makes things safe only, but sufficient insulation, grounding, wiring and safety devices do depending on voltage and use case.

 

[mercedesstern]

Are any of the second alternator options not Case grounded? Every one I have seen is case grounded, making it a moot point if you want a second alternator to charge your house bank.

You need a battery charger between alternator and battery anyway. You could build a floating ground of your 48V system and a grounded alternator by using an isolating DC/DC charger. On the other hand a floating ground is a good idea, since a high voltage potential can be building between the 48V system and the chassis.

 

[Midwestdrifter]

You need a battery charger between alternator and battery anyway.

Second alternators with external regulators are designed specifically to directly charge a battery bank.

The vast majority of them have their cases bonded to the negative terminal. Though I have seen isolated units for marine applications in the past.

 

[EBS-P]

Look a 48v battery will only supply an AC and an inverter/converter. I’d would to chassis with appropriate breakers/fuses to interrupt faults. I’d rather have the breaker/fuse sense the fault than myself.

 

[AH64ID]

You need a battery charger between alternator and battery anyway.

You definitely do not need a battery charger between the second alternator and the battery bank, in fact you should have nothing between the alternator and the positive bus but fusing.

 

[zanzabar]

unfortunately Volta arc flashed out of business.

Actually, they did not. The founder was bought out by PE, they changed the name to Voltagen, still same folks up in Holland MI.

 

[Happy29]

I'm not well versed in 48V systems, I do see a weak point in assembling four 12V batteries in series. Cells can get drastically out of balance from one battery to another. That means over time one battery may have 90% SOC while another has just 75%. A 48V battery has just one BMS. The 48V stitched together system has four independent BMS's. The 48V battery can keep all cells balanced, while separate batteries are unable to balance all cells to the same SOC.

This can be mitigated with a small active balancer that keeps the string balanced continuously. Internal BMS handles internal 4S and active handles external 4S.

Amazon.com

 

[Happy29]

48V appliances will appear if 48V becomes a rv standard. It makes sense to have a 48V cooktop or fridge.

What voltage are current appliances in a 48V rv? 120Vac? No more dc powered loads?

I have 48V inverter and air con. Induction is 120V and everything else is 12V. Wakespeed W48-12X bidirectional DC-DC converter handles the 12V loads. Builder f'd the 2nd alternator. Ditched it and added more solar. 1600W total. I'll add Victron 48V DC-DC charger due out this fall '26. Maybe.

 

[Rocksnsalt]

Actually, they did not. The founder was bought out by PE, they changed the name to Voltagen, still same folks up in Holland MI.

Yes this was pointed out in post 31, and I acknowledged and thanked @Boxster1971 for the information.
But thanks for reiterating it.
I’d still call defaulting on loans and being taken over by the lender a bit of an arc flash if AI is correct:

 

[calbiker]

This can be mitigated with a small active balancer that keeps the string balanced continuously. Internal BMS handles internal 4S and active handles external 4S.

Amazon.com

Yes, that device or something similar should keep the 4 batteries balanced. It's a bit scary that over 20% of customers gave a one or two star review. A lot of failures with excessive heat. The device is not ready for prime time yet.

 

[Happy29]

Yes, that device or something similar should keep the 4 batteries balanced. It's a bit scary that over 20% of customers gave a one or two star review. A lot of failures with excessive heat. The device is not ready for prime time yet.

That excessive heat is from one or more of the 4 circuits moving up to 10A! That's a VERY out of balance battery bank. Best to separate the packs and use a bench top power supply to bring each into balance first, the rejoin and re-connect the active balancer. It's for maintenance of a balanced bank, to keep it there, not to bring wildly out of balance batteries into balance. People misunderstand why it's getting hot. It's not a failure, it's trying its best to do it job to the MAX!

 

[Tim Hodgson aka "E350"]

For mere mortals like me, please see post #48 in this thread.

 

[StogieMan]

Or just get native 24 or 48v batteries to avoid any issues and stop trying to re-invent the wheel. Who wants to putz around with trying to balance cells? Just another thing to worry about and at the end of the day you’re going to loose that battle. This is just like the stubborn folks that still like to daisy chain batteries instead of using busbars. Avoid the issues from the get go and do it the right way.

I just spent three hours this past Saturday trouble shooting a customers van. Guess what the problem was? They installed two Epoch 460 AH V2 batteries daisy chained in parallel with equal length cables in a master/slave configuration. The slave stopped getting charged but the master was and completely drained the slave battery. I must’ve spent an hour just trying to get access to the batteries. I needed direct access to the dip switches to get them out of master/slave mode in order to be able to wake up the BMS and put a charge on that battery. Sold the customer on a Victron Class-t Power in which solves the daisy chain problem and also provides a class-t fuse for each battery for safety. He also paid for my time that could’ve been avoided from the start.

If you read most battery manufacturers manual, they recommend paralleling them with a busbar. Again, is daisy chaining done often? - absolutely. Is it best practice? - heck no! Even though Victron likes to sell their battery balancers and say that’s its ok to do, they too talk out of both sides of their mouth and recommend against daisy chaining batteries in their Wiring Unlimited bible and this is what it says:

3.2. Large battery banks

If a large battery bank is needed, we do not recommend that you construct the battery bank out of numerous series/parallel
12V lead acid batteries. The maximum is at around 3 (or 4) paralleled strings. The reason for this is that with a large battery
bank like this, it becomes tricky to create a balanced battery bank. In a large series/parallel battery bank, an imbalance is
created because of wiring variations and slight differences in battery internal resistance.