New Camper Build Planning - Considering NPR (USA) - Feedback Welcomed
- Thread starter luthj
- Start date
luthj
Engineer In Residence
Huh? There are extensive conversations about it. Asking an expert is a good option, if you are just googling for adverts, yeah most companies are just posting details on what they sell. Same goes for influencers on Youtube etc. Again, if you want to make blanket claims like that, I suggest you actually explain yourself. Cause right now you sound just like the "non one" you are griping about.
I agree most folks just default to DCDC vs alternator direct, but there are plenty of discussions of it.
DCDC/Alternator charging has some overlap with solar, but it is limited. They serve very different core purposes. DCDC is really only useful when driving significant amounts, and solar is only useful when there is good amounts of direct sunlight. So doing a direct comparison doesn't make any sense. Instead they compliment each other. It is very rare for a full-time overland vehicle to have just one or the other. 90%+ have both solar and alternator/DCDC charging available.
Dedicated second alternators are a bit different in that they can often output more than 3kw, which allows for short idle periods to charge a battery. In which case they are closer to a generator than a typical DCDC. Though high power DCDC chargers are somewhat available.
I have noticed a bit of a trend with your posts. You love to criticize (at least it seems like criticism) the generalized "other" or the entire industry for not considering your very specific needs and budget requirements. To be honest this reeks of hubris. You are building a custom overland vehicle, a niche one at that. Expecting everyone to have your needs in mind, and provide solutions for your specific specs is silly.
Do you have experience using these vehicles? Have you built more than 1? I personally would be much more reticent about proclamations such as yours in that case.
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Alloy
Well-known member
I haven't decided for sure what route I am going, but I did spot this 48V option which can be made to fit the second alternator spot on the Ford 7.3l gas engine. 4-5kw of output is pretty darn good, and with a 9-12kwhr battery pack should meet 98% of our usage when combined with ~1-1.4kw of solar.
48-Volt Elite Alternator (LiFePO4) for Ford T-Mount Housing W/ 6-groove pulley - Externally Regulated
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On my truck the dual (390a total) alternators take up the spot used for aftermarket golf, air compressors/alternators. Rather than a DC-DC I'll be installing a 1000w inverter.
Spend $550 for 30 amp charging a few hours a week. Hard to justify that.
luthj
Engineer In Residence
Huh, what are you talking about?
Lets see
4 AWG wiring kit $100
Alternator $250
Victron DC-DC charger $200
Here is $550 without labor
Charges at 30 amps
Drive time five hours a week
At a basic level, charge added (in amp-hours) is:
Amps × Time
So:
30 amps × 5 hours = 150 amp-hours (Ah)
What that means in practice
- Ideal / theoretical: 150 Ah added
- Real-world: usually 120–140 Ah, because:
- DC-DC chargers taper current as batteries approach full
- Charging efficiency is ~85–95%
- Voltage and temperature can reduce sustained output
If you want to think in energy (watts)
Assuming a typical 12V battery system:
- 30A × ~14V charging ≈ 420 watts
- 420W × 5h ≈ 2.1 kWh
Quick sanity check examples
- 100Ah lithium battery at 20% → nearly full in ~3 hours
- 200Ah lithium battery at 20% → ~80–90% full after 5 hours
For me
Less money, less complexity, almost no labor
Add a parallel battery to your battery bank - charge before leaving home
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Alloy
Well-known member
If there's a 50/100Ah 12V Lithium house battery you'll need a 48-12 DC-DC for that. Given the 14+ volts needed to charge Lithium a 3 way battery switch on the output of the DC-DC would allow charging of the FLA starter battery in an emergency.
LOL there is a lot of confidence here for someone who hasn’t yet had a trip yet.
Adding a dc/dc does cost more $$$ than not adding one at all but that is more whataboutism than real decision making. How do you rationalize the cost, weight, infrastructure, and space that the “spare” battery occupies once it is depleted?
Moreover, what vehicle doesn’t have an alternator? Victron’s original Orion 30 amp admittedly is pretty poor (I have one and wasn’t impressed). Their XS 50 amp model is much more effective and changes your math quite a bit, especially when solar output is added into the mix.
There is no single, ideal solution for mobile energy storage and production. Ideally, multiple solutions should be available to account for commonly encountered phases of a trip: enroute, at camp, latitudes and seasons of travel, etc.
Outside the box thinking is great and is responsible for a lot of the innovations we depend on but sometimes, it is responsible for enthusiastic but short-sighted “solutions.”
luthj
Engineer In Residence
That literally has nothing to do with the setup I am discussing, and even then there are a bunch of assumptions that only apply to what appear to be your usage case.
The hubris is quite stark actually.
I am discussing a second alternator with a 5 kilowatt output. And using a $80 DC/DC charger to keep my starter battery topped up when parked.
Well I try to avoid making blanket statements like yours specifically because everyone's uses case is unique. There are a number of usage cases we're spending $500 on a 30 amp DC/DC installation is a excellent value. And there are others where it doesn't make sense.
Regardless most of the time when I use my vehicle I am full timing for years at a time. There is no "home" to return to. So all my plans are based around allowing me to operate the vehicle for an extended period in a wide range of climates and conditions. Spending 50 bucks a night just to plug in and enjoy the noise for my neighbors it's not a great trade-off compared to spending a few thousand dollars on a robust electrical system with multiple charge sources.
I have spent thousands of nights vehicle dwelling in climates that range from Sub-Zero to 100f. I have also designed/consulted on a dozen systems for various individuals including full-time overlanders ranging from Africa to Australia. Well I generally don't bill myself as an expert in all aspects, I have a good appreciation for the range of usage cases.
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luthj
Engineer In Residence
Yeah there's a few different considerations. I'll probably have a 50 amp hour LFP standby battery on my 12 volt bus. A dedicated 48 to 12 for the 12 volt bus. Adding a current limited direct connection between the starter battery and the house 12 volt bus could be used for trickle charging the main battery. There are a couple ways to do it. A really simple method is to use a diode and 10 watt 12v incandescent light bulb. Which supplies between 1500 milliamps max of trickle current to keep the battery topped up.
For the 12 volt bus I'll probably set the charger to about 13.5 volts. The standby battery won't be charged to full, but we'll have enough capacity available to handle the occasional surge. It'll also keep the monitoring system alive if the main 48 volt bus goes down for some reason.
It's also possible to direct connect the two 12 volt batteries together for a jump start scenario, however there is some consideration for peak current and cable size. So it's not quite as simple as adding a switch, at least with a smaller battery like that.
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