Electrical diagram review

Hi all,

I've got 2006 Dodge Sprinter 2500 144". I'm planning on adding an aux battery that charges off the alternator via isolator. I have pretty minimal usage requirements (lights, low power fridge, fan, laptop) that will likely only be running on/off throughout the day, if at all. I'm not so well versed in these sort of power setups but after a lot of research I think I've got a plan. I drew out a diagram to organize everything. Any feedback/suggestions/warnings/etc are welcome! Just trying to avoid blowing up the whole rig...

I've listed out the specific products, wire gauges, cable lengths, etc in the diagram. If there's anything I can add to clarify or make this easier to understand let me know!

Thanks!!!

Like the functional simplicity. A DC to DC charger might be a little better for getting a complete charge on your house battery. They are more expensive but there are some brands/models that also include an MPPT solar controller if you plan to add some panels in the future. We like/sell the Kisae DMT1250.

All the best,
Hein
DIYvan

It is a simple design, but likely will not really work properly. In fact if you do it that way, you will be very unhappy. Sorry to tell you this.

In most vans, the single largest power consumer are the refrigerators, and that is where solar panels really help.

The house battery capacity is fairly low - that setup will run the fridge and indicated loads for less than 24 hours before needing multiple hours of driving to catch up. At least double the battery capacity.

The system will benefit greatly from 300 watts of solar panels or at a minimum a battery to battery charger. If you search on the poster "orton" he routinely suggests putting a small inverter on the starter battery, and using either a 120 vac - 12 volt charger, or a combo inverter charger to charge the house battery. This is a far superior option to an isolator based approach. Since your computer use is fairly modest, then this is sufficient for all similar loads.

I would avoid "all in one" products like the kaises. Stick with individual components as much as possible.

Your wire sizes are too small - where you indicate 14 awg should instead be 10 awg and the 2 awg should be 2/0 (also called 00 ) If the design is changed to instead use an inverter at the starter battery and a charger at the house battery, the wire size can drop to 10 awg instead of 2/0. One of the benefits of this is that you can use one wire size for the entire project and it will be much easier to install.

Consider to replace the master switch with a 50 amp breaker so it provides both switching and safety.

Perhaps purchase just about any other brand of inverter than the one you show. For example outback,

Sorry, don't mean to be critical, just help save you from wasting your hard earned money.

Take a look at these guys for components. Most of it is fairly decent and reasonably priced. Even their most econo / cheapo product offerings will work reasonably well.

https://www.solar-electric.com/marine-rv.html


Harry

The 1.5 amp you list for the laptop is at 120vac ... so the draw from the battery will be ten times that: 15 amps.
(plus inverter inefficiencies).

True, it may not be asking for full power all of the time, but that depends upon what you're asking the laptop to do.
You might be able to find a suitable 12vdc-to-laptop adapter, and cut out the middleman (but keep an inverter for other duties).

AGMs don't like being drawn down below 50% state-of-charge (SOC).

You didn't specify your fridge's actual draw/useage/size ... so its daily needs could be anywhere from 24AH to 48AH.

With careful load management, i manage to get by with only a 67 AH AGM, but that's with 200 watts of solar and a 40 liter Engel: 2A intermittent, except in a 35 C situation when it was running 3A at a significant duty cycle (on/off time). But the sun giveth.
I'm also equipped for shore power (which handled the fridge overnight).

--dick

I suggest doing a power consumption budget. Only then will you know if your battery and charging sources are correctly sized.

autostaretx said:

The 1.5 amp you list for the laptop is at 120vac ... so the draw from the battery will be ten times that: 15 amps.
(plus inverter inefficiencies).

True, it may not be asking for full power all of the time, but that depends upon what you're asking the laptop to do.
You might be able to find a suitable 12vdc-to-laptop adapter, and cut out the middleman (but keep an inverter for other duties).

AGMs don't like being drawn down below 50% state-of-charge (SOC).

You didn't specify your fridge's actual draw/useage/size ... so its daily needs could be anywhere from 24AH to 48AH.

With careful load management, i manage to get by with only a 67 AH AGM, but that's with 200 watts of solar and a 40 liter Engel: 2A intermittent, except in a 35 C situation when it was running 3A at a significant duty cycle (on/off time). But the sun giveth.
I'm also equipped for shore power (which handled the fridge overnight).

--dick

Click to expand...

Unless the OP is running a workstation notebook with say a modelling/render program plus a discreet GPU at full speed, he will never see it consume 15A dc (inverter load). Surfing and netflix are in the range of 2-3A dc.

I do the former on a slightly aged 2.8 GHz (3.45 Boosted) machine and peek at ~14A dc full out....

HarryN said:

The house battery capacity is fairly low - that setup will run the fridge and indicated loads for less than 24 hours before needing multiple hours of driving to catch up. At least double the battery capacity.

Click to expand...

autostaretx said:

You didn't specify your fridge's actual draw/useage/size ... so its daily needs could be anywhere from 24AH to 48AH.

Click to expand...

I was looking at the 10801352 - 37QT PORTABLE ARB FRIDGE FREEZER. The website says the current draw is 0.85 amps/hour*
*Average power consumption tested at 37.4°F cabinet temperature, 78.8°F-87.8°F ambient temperature range, test duration of 66 hours and supply voltage of 12V DC
https://www.arbusa.com/portable-fridge-freezers/classic-sii-range-fridge-freezers/
I'm assuming that's an average and may be higher but thought this fridge would have really low impact on overall battery usage. I was just assuming 0.85 * 24 would be the rough usage for a day. Thoughts? I am reading this incorrectly?

HarryN said:

The system will benefit greatly from 300 watts of solar panels or at a minimum a battery to battery charger. If you search on the poster "orton" he routinely suggests putting a small inverter on the starter battery, and using either a 120 vac - 12 volt charger, or a combo inverter charger to charge the house battery. This is a far superior option to an isolator based approach. Since your computer use is fairly modest, then this is sufficient for all similar loads.

Click to expand...

I need to research this more. Thanks for the tip.

HarryN said:

Consider to replace the master switch with a 50 amp breaker so it provides both switching and safety.

Click to expand...

Why 50 amps? The peak draw of the fuse block is 100A.

HarryN said:

Sorry, don't mean to be critical, just help save you from wasting your hard earned money.

Click to expand...

It's OK! That's why I posted. Taking criticism is easier than uninstalling/returning parts.

OrioN said:

Unless the OP is running a workstation notebook with say a modelling/render program plus a discreet GPU at full speed, he will never see it consume 15A dc (inverter load). Surfing and netflix are in the range of 2-3A dc.

Click to expand...

I think the diagram I put together is the most complex thing I would do on my machine.

dwighttttt said:

I was looking at the 10801352 - 37QT PORTABLE ARB FRIDGE FREEZER. The website says the current draw is 0.85 amps/hour*
*Average power consumption tested at 37.4°F cabinet temperature, 78.8°F-87.8°F ambient temperature range, test duration of 66 hours and supply voltage of 12V DC
https://www.arbusa.com/portable-fridge-freezers/classic-sii-range-fridge-freezers/
I'm assuming that's an average and may be higher but thought this fridge would have really low impact on overall battery usage. I was just assuming 0.85 * 24 would be the rough usage for a day. Thoughts? I am reading this incorrectly?


I think the diagram I put together is the most complex thing I would do on my machine.

Click to expand...

Let's do this in watts and watt-hrs to make your life easier.

Fridge ~ nominal (12 volts) x (~ 1 amp average draw) x (24 hrs) = ~ 300 watt-hrs consumption per day (can double on hot days)

Fan ~ nominal (12 volts ) x ( ~ 1 amp typical draw) x (24 hrs) = ~ 300 watt-hrs per day (also can double on hot days)

Lights - nominal (12 volts) x ( ~ 5 amps) x (8 hrs / day) = ~ 400 watt-hrs per day

Entertainment ~ 200 watt-hrs per day

Total = ~ 1200 watt-hrs per day of consumption.

____________
In a good size 31 XT AGM battery, you can routinely use ~ 50% of rated capacity, so:

(125 amp-hrs) x (12 volts) x (~50%) = ~ 750 watt-hrs of capacity

This is vs our estimate of 1200 watt-hrs of consumption per day, so at least 2x is suggested. 4x is better in case of cloudy days, but it depends if you are mostly having fun for a long weekend and minimal risk, vs living off grid in a difficult situation.

__________________________

In this area, the expected production of a solar panel on top of a van is roughly:

Expected power production per day = (50%) x (official rated capacity) x (6 hrs per day of useful production)

Your consumption plan is ~ 1200 watts-hrs, and using my initial estimate of 300 watts of panels:

(50%) x (300 rated watts of panels) x (6 hrs) = 900 watt-hrs, so actually just a tad short.

(50%) x (450 watts rated of panels) x (6 hrs) = 1350 watt-hrs - so potentially enough on a typical day but not by all that much. In the winter you could be short.

This of course assumes that the bulk of the power is from solar, which is not always the case.

Assuming that you buy a 1 kW inverter to pull power from the starter battery, and feed it into a 400 or 500 watt charger, then as you drive, it will take roughly:

- (1200 watt-hrs) / 500 watts = ~ 2.5 hrs of bulk charging

Plus another 2 hrs of finishing stage charging to complete

Combined with the solar though, a good 1-2 combo.

dwighttttt said:

I
Why 50 amps? The peak draw of the fuse block is 100A.

:

Click to expand...

Fuses and breakers are used to protect all aspects of the system, wire, components, etc.

The 4 awg wire needs to be protected and 50 amps is a good target for that size.

Unlike AC transformers, typically in DC the losses are fairly high, so the components are used at less than their capacity. The only reason I suggested as large as 50 amps is to supply the 600 watt inverter, otherwise 20 amps is enough and potentially you could again use 10 awg wire unless the wire runs are long.

OrioN said:

Unless the OP is running a workstation notebook with say a modelling/render program plus a discreet GPU at full speed, he will never see it consume 15A dc (inverter load). Surfing and netflix are in the range of 2-3A dc.

Click to expand...

Up until yesterday i'd fully agree with you ... but yesterday i almost burned my arm as i rested on my whimpy I5-bearing laptop's adapter ... and the adapter was **hot** (and rated at 1.5 amps).
I had a couple of NASA animations playing (i.e. "just web browsing"), but something sure got it toasty (the laptop's fan had come on full-tilt, too, so that supports a "cpu being busy" model)

Today it's not anywhere near that warm.

I do the former on a slightly aged 2.8 GHz (3.45 Boosted) machine and peek at ~14A dc full out....

Click to expand...

I was too preoccupied to chase down the hardware for measuring what was going on...

--dick