Power supply dilemma for wiring noob

[f250ben]

Hello guys! This is my first post on expedition portal. Super appreciate all the info, this place is great. I'm brainstorming my future power setup and I need help. This is not my forte, and I'm a bit overwhelmed with all the info about dual battery systems, solar, yeti's, group31 aux batteries, and the works. I want to figure out a GENERAL layout of my future wiring setup, so I can do it correctly as I add aux power draws in the near future.

I have a 2003 Toyota 4runner, on the beginning of what I plan on being a somewhat extensive build. As fun as the money cannon approach would be, that's not going to be mine, because the dollar store was all out of money cannons when I checked ? . I'm on a budget, and not doing all work at once. This is more a staged thing. We do one thing, go on some trips with that, take notes on what we'd like to happen next, wait for the next bonus, then do that.
I just added a RTT, and I very much expect the highest priority add-ons for the wife will be camp lights off the side of the roof rack, some lights and a fan in the RTT, and possibly a fridge at some point this year or next. I hate doing things twice, and I HATE wiring. And its confusing to me, and I don't understand a lot of it. So if we're going to wire stuff up, I want to do that in a manner that allows for futher add-ons over the next couple of years, WITHOUT having to rewire the rig every time.

Aux items planned in the next 12 months:
-camp lights on side and rear of rack, like rigid a series (prob 2 on each side, and 1 in the rear
https://www.rigidindustries.com/led-lighting/480343
-power supply run to RTT (no converter necessary), running 3 circuits: strip lights, some type of 12 volt van, 12 volt power strip with USB and 12volt plugs
-budget fridge like a whynter model. Probably would stay in the vehicle almost all the time.
-would love to run some additional 12v accessory circuits, 1 to rear of vehicle, and 1 to center console/dash for constant-on power WITHOUT modifying factory wiring.


Long term wishlist aux items:
-aux offroad lighting-no idea what
-winch
-CB or CB+HAM setup
-front and rear dashcam setup
-probably something entirely unrelated that I haven't thought of

BIG QUESTIONS:
-Do I need a dual battery setup for this?
-Are there other alternatives to dual battery that would work for me or would be much cheaper? Single deep cycle, ark pak or goalzero aux power box, etc? As far as I can tell, they're all compromises in some form that I'm not keen on.
-What is the best, simplest way to set all of this up?
-I know I want an bluesea fuse panel for all aux circuits. Basically running everything listed here. I also know I want to run a switchpros setup for switches. Can I set that up, powered from vehicle battery for now, then later add a dual battery setup as I add larger power draws, and run new power to the bluesea from my second battery, WITHOUT re-wiring all of the individual circuits?
-Would I need a second aux panel of some sort JUST for the RTT setup?

BIG WANTS:
-Wiring things once. I do NOT want to rewire stuff multiple times as my setup grows, if I can avoid it at all.
-No solar, not interested, and doesn't really fit with my planned use for racks/gear mounting and storage etc.
-Setup that fits my longterm plans, and is somewhat flexible.
-Being able to start adding aux systems now, without spending 1-2 grand on the ENTIRE fancy, expensive dual battery, multiple aux panels system I imagine I'd end up needing.
-Some sort of staged diagram where I can add systems/wiring in stages, in a manner that fits the overall plan.

I'm going to do a simple diagram, with where I want things, then will post back with that. I'm sure it will be quite incomplete, but it's as far as I've gotten.

 

[luthj]

Yeah, you have a tough order of wants/needs. No solar, but you want to run a DC fridge? You want to add a winch, and for it to be future proof?

We need to know more about your usage case. How often and how long do you drive? How long does the vehicle need to sit with the fridge running? What voltage does your alternator output? This will determine if you can make due without a pricey DC-DC charger. How often do you expect to replace battery(s)? Some folks are okay with replacing a dual purpose starting battery every year or two instead of installing a dedicated deep cycle with proper charging. What is your desired fridges power consumption (A-HR or watt-hr)?

Ideally you would make a list of the power consumers, the amount of time they run in a day, and their power consumption. This would let you work out the size of battery(s) you need, and what charging options can meet your needs. The more details the better.

My take.

Get an aux battery, or replace your starting battery with a large deep cycle (capable of starting duty). Sizing may be difficult or impossible in the stock location.

What voltage does your alternator output? This will determine if you can make due without a pricey DC-DC charger.

Connect the winch to the starter battery. You won't be using it with the engine off. All your other engine-on type loads (driving lights radio etc) can be wired to the starting battery. A small fuse/distribution block for these loads would be simplest. Another block would be used for Aux battery loads (if needed).

There is a substantial variance in power consumption with DC fridges. Size, brand, ambient temp makes a difference. Low side would be 20-60AH a day, high side would be 50-80AH.

Sizing your wiring for future expansion, and ease of adding loads/charger is not difficult. The batteries and/or charge devices are about the only items that you need to select for future-proofing.

Lead acid batteries used in deep cycling applications do not last long if they don't get fully charged regularly. This means regular long-ish drives, solar, shore power etc. Dc-DC type chargers that boost alternator voltage help, but they don't solve the problem of short drives. A shore power charger that gets connected once-twice a week can do the job for vehicles with alternator only charging. Of course this varies depending on depth of discharge. A smaller engel fridge uses very little power in moderate temps, so even alternator charging can be sufficient to get decent life from a battery.

 

[f250ben]

Ok this is helpful. I’ve also been doing a lot more reading since my first post.
To clarify,
1) I’m only considering a fridge that would run on 12v. Whynter does make a 12v optioned model.
2) don’t remember exactly how I explained it in my first post, but it’s pretty probable that the fridge and winch will be next year. IE. not immediately.

Your questions:
- Vehicle would probably not sit more than a full day without some form of driving. Most of the camping were doing is small state parks. Shore power is always available. Well do bigger trips where the vehicle is independent for days at a time, but we’d be driving during those trips and they probably won’t happen more than once every year or so.
-Not really wanting to replace batteries yearly if I can help it.


When listing power consumers and length of time, time away from shore power etc, should I be looking at average scenario, or most extreme case I can imagine applying to us?

Can I run some heavy gauge wire to the rear of the vehicle for a blue sea auxpanel for small draws, connect to main battery now, and move that power over to aux battery whenever I add one, and I need it for increased capacity?

That’s my inclination right now.

Now-Run power for aux panel in rear-just USB’s and some lights inside hatch for now, with heavy gauge wiring that can handle fridge down the road

Now-Run power through roof for rtt aux panel, with Anderson disconnect and aux panel box inside rtt
This will run strip lights in rtt, usb and 12v charging ports, and a small fan. Small fan is the biggest question for me. From what I can tell they pull 1-3 amps per hour. Is that a lot and could I run one of those on my stock battery only for 8-10 hrs?

Later this year-Eventually add a switchpros box to remain powered off of main battery.

Whenever I want a fridge or winch added:
Add second deep cycle battery with acr. Redirect power for both aux panels to aux battery. Hook up fridge to rear cargo aux panel and winch to starting battery.

Before the next long trip after that:
Run a marine shore plug for charging deep cycle battery without popping hood.

Does this chain of events make sense/sound like a solid plan?


Sent from my iPhone using Tapatalk

 

[luthj]

Your approach is reasonable. Given your small initial consumers, you can start with just a hookup to the starter battery. Drawing your starter battery down 5-15% of its capacity between drives (hopefully at least an hour long at the deeper discharge) is generally acceptable. I would reccomend a quality dual purpose battery for this type of use.

Here is a calculator for wire sizing. http://circuitwizard.bluesea.com/
Size your wiring so that critical loads (fridge for example) have a 1-2% voltage drop (from the battery). And non critical loads are 3-4% allowed drop. For a fuse block feed use your expected load on that block. 15-40A is a common range. Fridges are sensitive to voltage drop, especially during start up. So design around a 1-2% drop at around 5A for the fridge circuit. Remember this includes both positive and negative runs, from the fridge to the fuse panel, and panel to battery. This may mean 8 gauge or larger for the fuse panel feed, and 10 gauge for the panel to fridge. You may find that a good chassis ground has a much lower resistance than running a long cable all the way to the engine compartment.

The 12v compressor fridges are fairly efficient overall, but whytner is on the lower end for these types. If you can find some real work measurements of duty cycle and power draw that would help a lot. In general if you are going to leave a fridge running for more than a day without driving a significant amount, you need solar, or shore power. If you have shore power, a quality multi-stage charger in the 15-20A range can recover a decent sized bank overnight if used once or twice a week in conjunction with alternator or dc-dc alternator charging.

The winch does not make much sense to wire to Aux, just because it is an engine-on type of load. It also needs really beefy cables, which can make combining with a low-current branch circuit (like your fuse panel) annoying.


You should do your electrical power "budget" for each usage case. Parked, daily use, camping use etc. Design for your most likely worst case (not absolute worse case), and you should have enough overhead for low charging situations.

 

[f250ben]

This may seem like a silly follow up question. But how do I calculate load and amp hours for a combination of multiple devices with different usage profiles?


Sent from my iPhone using Tapatalk

 

[john61ct]

Actually measure the usage is best.

Some cycle more or less over time, so say you use for four hours at a time, get a per-hour average number for your per-day budget spreadsheet.

AH per 24 hours @12V as the common unit, be sure to measure from the battery side of any inverter loads.

 

[dwh]

This may seem like a silly follow up question. But how do I calculate load and amp hours for a combination of multiple devices with different usage profiles?


Sent from my iPhone using Tapatalk

Roughly the calc looks like this...

82 watts ÷ 12 volts = 6.83 amps × 3 hours = 20.5 amp*hours.

Of course you have to insert the numbers for your actual loads and use times. Run the calc for each load and then total it all up.

Also keep in mind that the voltage varies - a fully charged lead-acid will be around 12.8v, but halfway drained closer to 12v. That's not terribly important for small loads, but it matters when talking about a fully loaded 2000w inverter.

 

[f250ben]

OK. Again, helpful info. The more questions I ask, and the more I read, the more I realize exactly how foreign electricity is to me.

Keep in mind this is a theoretical exercise right now.

So what I'm going to do is:

4 different usage profiles based on
1) camping with access to shore power
2) camping independant of shore power, but driving every day
3) camping for multiple days with no driving
4) running a few basic accessories with normal commute.

So I guess I actually need to calculate power USAGE, and power CHARGING profiles for each of those scenarios.

Usage needs to be based on accessories I plan on running. I can break that down by sub panel to calculate wiring guage etc, but I can also look at a total list sorted by load to see which accessories are going to overall strain the system the most.

Am I thinking about this correctly?

 

[john61ct]

Yes, but making it more complex than necessary.

Personally I design for long-term boondocking, assume no shore power at all.

So maximum efficiency, minimum use of electricity for non essentials.

Fill up the roof with solar, can't have too much.

Bank sized to get me through 3+ days of cloudy weather.

Generator + mains charger for occasional supplementary use.

Then if there are some luxury items that require shore power or running the generator, they are later / low priority in the list.

 

[luthj]

The OP has mentioned roof racks etc, so permanent solar is not a good option. Portable panels may fit his needs. Given his initial needs, and plan to upgrade later, a large bank is probably not needed up front.

There are two main approaches to this. The first is to overbuild the system for you needs, both charging and battery capacity. The second is to thoroughly analyze you usage case(s), and design for minimal overhead (can be cheaper).

So what I'm going to do is:

4 different usage profiles based on
1) camping with access to shore power
2) camping independant of shore power, but driving every day
3) camping for multiple days with no driving
4) running a few basic accessories with normal commute.

So I guess I actually need to calculate power USAGE, and power CHARGING profiles for each of those scenarios.

Your approach is good. Charging can be hard to calculate accurately, as each battery is slightly different, and even a few tenths of volt affects charge rates. Note that lead acid batteries charge current tapers down rapidly as they approach fully charged. There is a difference between 99 and 100% charged. 100% charged must be obtained every 3-10 charge cycles if the battery is to avoid premature decline. I have some experience with these systems, which has helped me develop an expected range for charging from alternators. With battery type/size, wiring sizes, and alt voltage I can probably help you with an estimate.

Case 1 is pretty easy. A properly sized shore power charger for 3-5 hours a day will take care of your needs, with a longer overnight top up once a month.

Case 2 is dependent on your alternator voltage and drive times (and cable sizes). A battery 2 battery (B2B) charger may be needed.

Case 3 is the hardest if you have a fridge. You either need a larger battery bank (150AH or more) or you have some solar. Portable etc. about 200w of panels moved to face the sun will probably work.

Case 4 will likely require no additional upgrades. Your factory battery should be up to the task, but do the math anyways.

I wrote the following guide up for electrical system budgeting. The section on calculating solar harvest is helpful as well.
https://sprinter-source.com/forum/showthread.php?t=58448

 

[f250ben]

The OP has mentioned roof racks etc, so permanent solar is not a good option. Portable panels may fit his needs. Given his initial needs, and plan to upgrade later, a large bank is probably not needed up front.

There are two main approaches to this. The first is to overbuild the system for you needs, both charging and battery capacity. The second is to thoroughly analyze you usage case(s), and design for minimal overhead (can be cheaper).



Your approach is good. Charging can be hard to calculate accurately, as each battery is slightly different, and even a few tenths of volt affects charge rates. Note that lead acid batteries charge current tapers down rapidly as they approach fully charged. There is a difference between 99 and 100% charged. 100% charged must be obtained every 3-10 charge cycles if the battery is to avoid premature decline. I have some experience with these systems, which has helped me develop an expected range for charging from alternators. With battery type/size, wiring sizes, and alt voltage I can probably help you with an estimate.

Case 1 is pretty easy. A properly sized shore power charger for 3-5 hours a day will take care of your needs, with a longer overnight top up once a month.

Case 2 is dependent on your alternator voltage and drive times (and cable sizes). A battery 2 battery (B2B) charger may be needed.

Case 3 is the hardest if you have a fridge. You either need a larger battery bank (150AH or more) or you have some solar. Portable etc. about 200w of panels moved to face the sun will probably work.

Case 4 will likely require no additional upgrades. Your factory battery should be up to the task, but do the math anyways.

I wrote the following guide up for electrical system budgeting. The section on calculating solar harvest is helpful as well.
https://sprinter-source.com/forum/showthread.php?t=58448

luthj, this is great. You're correct, I do have an RTT on my roof rack, as well as the need to occasionally completely clear the roof rack for hauling lumber. Short story, I can't dedicate permanent roof space to a solar panel.

Not planning on overbuilding, its more expensive, and given my lack of experience, I'd probably waste more money on top of that.

I'm really trying to work through this analysis on the front end, so I can make more educated decisions as I actually start adding individual components. There's no need for any of this if I just want to add a light bar, or some camp lights. Or run a fan in the RTT for a night. BUT I know I'll end up adding a fridge and bigger power consumers, and we want the ability to do an occasional bigger trip where we will be offgrid for multiple days. I'd spend the rest of my life offgrid starting tomorrow if I could. But family, wife, baby, job, bills, etc. So we're happy getting out every chance we get, and planning bigger trips for once a year or so.

Your thread on sprinter source is also SUPER helpful. I'm going to sit down this weekend, and run some calculations and try to work through all of this. I know I'm going to end up with the general conclusion of exactly what you said. I'll need a big power bank or solar to run multi-day off grid. Shorter stuff is more manageable, but a larger battery will be necessary somewhere in there.

If I can get it to a point where I have my own calculations (that I actually understand) supporting the knowledge of which components my stock battery will support, which components will require big picture bank upgrades, and which components or trips will require additional charging sources, then I'll have a general plan I can keep in mind, as I actually start adding individual accessories and components.


One additional question: can a B2B charger top up a deep cell with the starting battery? Can this be used as an additional charging source, maintaining a deep cell for days at a time without shore power?

 

[dwh]

One additional question: can a B2B charger top up a deep cell with the starting battery? Can this be used as an additional charging source, maintaining a deep cell for days at a time without shore power?

B2B refers to how it's connected, not how it operates. It actually charges the aux battery from the alternator.

When the voltage rises on the engine side (engine running, alternator producing), it starts charging the aux side.

Shut off the engine and the engine side voltage goes down, it stops charging the aux.

Some have a wire from the ignition to insure they won't work without the engine running.

So, no.

 

[f250ben]

B2B refers to how it's connected, not how it operates. It actually charges the aux battery from the alternator.

When the voltage rises on the engine side (engine running, alternator producing), it starts charging the aux side.

Shut off the engine and the engine side voltage goes down, it stops charging the aux.

Some have a wire from the ignition to insure they won't work without the engine running.

So, no.

Oh. Lol. I know that vehicle alternators have their limits in ability to completely charge a deep cycle. So I was hoping this was some type of device that could alternately, COMPLETELY charge a deep cycle with the vehicle system. Doesn't even make sense though.

Is there even a way a starting battery could completely charge a larger deep cycle battery? That's not even how batteries work right?

How obvious is it that I don't understand much about electricity? ?

 

[DaveInDenver]

Is there even a way a starting battery could completely charge a larger deep cycle battery? That's not even how batteries work right?

Sure, one battery could be used to completely charge another in theory. The relative sizes would determine the outcome. IOW, if you have one fully topped battery and another dead of a similar size you could completely flat the source while fully charging the other. You only have a fixed amount of stored energy so wasting it charging an aux and losing some in the process is counterproductive in this context.

There's no reason really to do that so most of the time cut off is going to be set to stop when the alternator stops. If the starting is smaller (fewer A-hr) than the house it will never fully charge it, though. Think of batteries as bottles of water. You have a starting battery that's 32 ounces and a house that's 1 gallon. If you dump the whole starting bottle into the house it will raise it some but it can't ever fully fill it.

Some DC-DC chargers have the ability to set a lower cut off with the expectation that you might want to fully finish a charge if being below 100% charged is sufficient to start an engine or perhaps you assume solar will kick in at some point. You set maybe 12.4 V as the kick out instead of +/- 13 V that would otherwise indicate the alternator stopped. There are use cases that you might carry a charged source to a remote location and go back with a dead battery. That's more or less what a jump pack is expected to do.

 

[f250ben]

Sure, one battery could be used to completely charge another in theory. The relative sizes would determine the outcome. IOW, if you have one fully topped battery and another dead of a similar size you could completely flat the source while fully charging the other. You only have a fixed amount of stored energy so wasting it charging an aux and losing some in the process is counterproductive in this context.

There's no reason really to do that so most of the time cut off is going to be set to stop when the alternator stops. If the starting is smaller (fewer A-hr) than the house it will never fully charge it, though. Think of batteries as bottles of water. You have a starting battery that's 32 ounces and a house that's 1 gallon. If you dump the whole starting bottle into the house it will raise it some but it can't ever fully fill it.

Some DC-DC chargers have the ability to set a lower cut off with the expectation that you might want to fully finish a charge if being below 100% charged is sufficient to start an engine or perhaps you assume solar will kick in at some point. You set maybe 12.4 V as the kick out instead of +/- 13 V that would otherwise indicate the alternator stopped. There are use cases that you might carry a charged source to a remote location and go back with a dead battery. That's more or less what a jump pack is expected to do.

I've literally learned more about batteries and power sources in this one thread than all the reading and research I've done combined.

Also thanks for taking the time to answer my questions! Totally get the "search first" responses to threads sometimes, but you get to a point where you have your own questions that are road blocks for you.

I think this thread has given me some really great tools to work with, to continue some planning and analysis of my needs and future build plans. Gonna work on that this weekend, then post back up with scribbly wiring diagrams, and probably more questions. And hopefully some good usable numbers.