Batteries and Charging Basics
Van Electrical Systems - All about Batteries, Solar, Charging and Electrical Distribution
Van Electrical System Overview
The electrical system was the most complicated and expensive part of our Sprinter van build, but it doesn’t have to be. The complexity and cost of your van electrical system will be dictated by your needs and budget. If you tend to be at RV parks with dedicated shorepower, you may only need a small 12 volt (V) battery, a converter and some plugs and outlets. If you spend more time off-grid you will need a larger battery bank and a way to charge it. You will also likely want an inverter to power small household-type appliances from your battery.
With so many choices, how do I get started on my van electrical system?
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Simple Van Electrical System
Let’s start with a simple system, such as the hardware that you might find a small camp trailer. Most electrical devices will be designed to run on 12V DC (Direct Current), which is provided by an automotive-style lead acid battery. A plug on the outside of the trailer allows you to plug in to 120V AC (Alternating Current). The trailer’s converter reduces the voltage down to 12 volts and converts the AC into DC power. The 12V DC keeps your battery charged and allows your devices to be powered from the shorepower.
While simple and inexpensive, these systems provide very limited stored energy for being off-grid. We have seen camp trailers go dark after just one night-out as the battery is not large enough to handle the loads.
If off-grid is what you’re looking for, you want to start with a decent-sized battery, or two. For background on different types of battery chemistry (lead-acid, AGM, lithium ion, etc), read this excellent article from the Battery University.
Lithium battery Complexity
Batteries and Amp-Hours
One measure of the ability for a battery to handle a given load over a given period of time is measured by the metric “amp-hour.” Say your overhead lights pull 1 amp when running, and you want to run your lights for 6 hours. 1 amp x 6 hours equals 6 amp-hours drawn from the battery. A typical single 12V Absorbed Gas Mat (AGM) battery would store around 100 amp-hours of energy. So I could run my lighting for 100 hours then, right? Not exactly. Most AGM battery manufacturers recommend you do not drain the battery below 50%. Permanent loss of capacity occurs with this style battery below 50% state of charge. If you follow the manufacturer’s recommendations, you would get roughly 50 hours of running your 1-amp lights.
Not knowing how big of a battery we would need, we sat down and made a list of everything electrical we wanted to run in the van. You can find that write-up on our systems planning guide. Spoiler alert: our number came up around 45-55 amp-hours per day. If we had a single 100 amp-hour AGM battery, we could get one day out of it. Any longer and we would dip below the recommended 50% state of charge. (This assumes you are not charging the battery by solar or other means.) Knowing we want 3-4 days off-grid, it meant we require a minimum of 150 usable amp-hours.
Battery Weights and Sizes: AGM vs Lithium
Let’s skip to our realization. To get 150 usable amp-hours from an AGM battery, we would need TWO 150 amp-hour batteries. The FullRiver DC-150-12 have the following specs: 7.17″W x 12.87″ L x 10.75″ H, with a weight of 93.9 lbs (EACH!)
So yes, nearly 200 lbs of battery with a large physical footprint as well.
This is where we first became interested in lithium ion phosphate (LiFePO4) batteries. The first advantage of LiFePO4 is the fact that you can drain them down to 20% capacity, compared to the 50% of an AGM. That’s “free” capacity. A single 200 amp-hour (rated) battery would provide 160 usable amp-hours. The footprint would be much reduced at: 5.5″W x 19.25″ L x 9.6″ H (only ONE needed). Did we mention the weight yet? 55 lbs; versus 188 lbs for AGM.
So 10 more usable amp-hours than the AGM scenario and 1/3 of the weight and much less floor space needed. These are some of the things you should be thinking about in order to determine roughly what size and type of battery you may need for your van electrical system.
Lithium Battery Advantages
Besides power-to-weight, there are some other advantages of lithium batteries. The typical resting voltage of a lithium battery is 13.25 volts, versus around 12.8 volts for a flooded battery. When you turn on a large load like a coffee pot, the lower internal resistance of a lithium battery means a 75 amp load may only dip the battery voltage by 0.2 volts, where it might drop the voltage over 1 full volt on a flooded battery. Many inverters on the market shut down at 11.8 to 12 volts to prevent damage to the battery. This means you may not be able to power high-draw devices on a flooded battery without tripping the inverter.
The lower internal resistance of the lithium battery also results quicker charge times. As a flooded battery passes about 80% full, the internal resistance increases and it “pushes back” on your charging source. This slows charging, which means you are wasting precious limited sun-hours when charging on solar. In our experience, the lithium battery charges at the full rating of our solar panel right up to 100% state-of-charge. There is a limited, or no “asborb time” on a lithium battery. (Ours is set to 2 minutes, whereas a flooded battery is often 1-2 hours). This means a much fuller battery in much less time.
Charging on Shorepower
“Shorepower” is the term used to describe hooking your camper to grid-power, usually a powerpost provided at a campground. Depending on what country you’re in, 120V or 240V AC enter via a port on the side of the RV. The converter or inverter charges your battery and reduces the voltage to 12V DC to run your devices. If you have access to shorepower often, you may not need a robust battery bank or alternate charge sources. Your electrical system will be simple and inexpensive. That said, we never go places that have shorepower. If we needed to, we could plug our Magnum inverter/charger into an extension cord and into any standard outlet to charge. We have never used shorepower to-date, but you might find it useful for your needs.
Charging Batteries by Solar
One way to extend your time off-grid is to have a way, or multiple ways, of recharging your batteries without the use of shorepower. The two most common ways include solar and the ability to charge using the vehicle alternator, when running. You can also use a generator.
We wanted a robust solar system to keep our batteries charged without having to run the engine. Normally you would size your solar array based on your electrical needs. When you have a van and only so-much roof real estate, you just install as much panel as you have room for. We went with a single LG 300 Watt panel because they have a very strong extruded aluminum frame that offer flexible mounting options and have proven to withstand life on top of moving vehicle. The panel width would allow mounting between the stock roof rails on our Sprinter. The length was about right to cover the rest of our roof that wasn’t already occupied by the Maxxair Vent Fan.
The Solar Roof Rack
We purchased some CNC-cut feet (eBay link) that fit into the factory roof rails and used 80/20 extruded aluminum (cut to 46″ width) as cross bars. The panel bolts to the 80/20. The entire setup is very low profile, only has two wires total (one positive and one negative). At times our panel has provided more than the full rated power.
The Solar Charge Controller
We are using the Victron 100-30 MPPT bluetooth-enabled solar charge controller to reduce the 39V DC that our panel produces into voltage and current the battery can accept. We can’t say enough good things about Victron. The hardware is high quality and the ability to monitor and update settings on your solar system from a smartphone is just brilliant.
Since April 2017, our battery has been charged nearly 100% by solar. We have other ways of charging, but have only used that system once. We are completely impressed by how the solar system has performed.
Charging Batteries by Alternator
A second common approach to charging your batteries is to use the vehicle alternator. In the old days you would use a battery isolator/combiner to charge your auxiliary bank. That approach does not work well in modern vehicles. This is a very complicated matter that you can read about here. In short, the best way with today’s modern vehicles is to use a battery-to-battery charger. These get mostly around the limitations of vehicle smart alternators with regenerative braking features, and provide a hands-off automatic approach to keeping your batteries charged.
If we had to make a recommendation for most people, that’s probably the best OEM-like solution. But it has some down-sides we did not like. For one, solar charging has met 100% of our needs so far. Charging by alternator puts additional wear and tear on the vehicle’s electrical systems and the harder you work the alternator, the further you decrease your fuel economy. If the fuel economy difference were not noticeable, then auto manufacturers would not be spending the extra money to equip your car with features meant to reduce alternator usage. It matters.
Using an Inverter to Provide Power to an Inverter/Charger
The approach we are using is not conventional and it’s not necessarily one we would recommend to most people. It’s not automatic at all. We consider it our “emergency backup charging source,” in case we are on a trip and loose access to solar due to conditions. In 4 years of travel, we have only needed it once. We are using a small 600 watt inverter, fed from the vehicle electrical system, which converts the 13-15V DC produced by the alternator into 120V AC. The 120V AC travels through a small 14 gauge wire to the rear of our van where it provides “shorepower” to the inverter/charger, which charges our batteries. That was a mouth-full, let’s take a closer look at that.
We are using a Magnum 1000W combination inverter/charger in our van. It converts 12V DC battery power into 120V AC so we can run things like a microwave. It also has a battery charger built-in, so when plugged into 120V shorepower, it charges the batteries. What we have done is take the 120V signal from the 600W inverter connected to the vehicle electrical system and used it to feed the inverter/charger, which thinks it’s just connected to shorepower.
Why Use This Method?
It’s simple, effective, cheap, and gets around the smart alternator limitations in the same way that the DC to DC charger does. Unlike the DC to DC charger, it uses small AWG 14/3 wiring, as opposed to the very large 1 to 4 gauge wire that would be needed to provide 12V and 50-60 amps to the rear of the vehicle. It also means that whatever charge settings are set for shorepower are also used when alternator charging. (In other words, one less device to program.)
Downsides of our “Emergency” Charging System
Downsides of our approach? On paper, it’s inefficient. Inverters are usually only 80-85% efficient, so you have that loss twice. Does it really matter when it’s our emergency backup? Nope. Other downside is it is far from automatic. If we ever do need it, we have to open the passenger door, open the seat pedestal door and turn on the inverter. We also have to turn it off when we shut off the vehicle, otherwise it would drain our auxiliary battery until the inverter hits its pre-programmed low voltage drop-out (to save from killing the battery).
Now we have the start of an off-grid van electrical system. We have a battery with good capacity and we have ways to charge it to keep us off-grid even longer.
Inverter – Converting 12V DC to 120V AC
An inverter takes the 12VDC from our battery and converts it to 120VAC so we can plug in small household appliances. We use our inverter to power an induction cooktop, an electric tea kettle for morning coffee, a microwave and to charge a laptop.
The inverter is dependent upon your battery to provide the rated power for the duration it is on. If you plug in a 1500 watt space heater to your 2000 watt inverter connected to a 100 amp-hour battery, you will be pulling 125 amps from your battery. (Factor in the 20% inefficiency of the inverter and you may be at 150 amps.) You would hit 50% battery capacity in 20 minutes. As a result, your inverter should be sized taking in to account the items you plan to power from it as well as the battery capacity you have available.
The Inverter We Chose
We determined that with our “small-ish” battery capacity of 200 amp-hours, it would be somewhat pointless to have a 2,000 watt inverter. At those power levels it would only power hungry devices for a short period of time. We chose a 1,000 watt Magnum inverter. It runs everything we need to run without killing our battery in short order. We will caution you though, you have to be careful when selecting things like microwave ovens and induction cooktops. They must fall under the 1,000 watt rating of the inverter. In fact, our 600 watt microwave pulls 926 watts when running. The only way to now what a device truly uses is to plug it into a kill-a-watt meter and calculate the actual amp/watt draw.
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Summary
We hope this gave you a bit of background on the possibilities when it comes to batteries, charging and conversion of electrical power. For more detail on the Karavan electrical system, including wiring diagrams, click here.
Thank you very much Ken, I really appreciate the response and now I can put it all together.
Thanks again
GOD’S PEACE IN CHRIST
BRIGITTA AND JERRY
I just saw your video on the alternator charge. I’m going to set up a similar system myself. I had a question about why you thought you needed a pure sine wave inverter instead of a modified sine wave inverter. I’ve been wondering if I can get away with a modified sine wave inverter myself and wanted to know if you had any insight on that.
Also, a remote switch for the inverter that runs off the alternator/van electrical would make it a little easier to turn the charging on and off, for example when you’re driving the vehicle. I’m not sure if the samlex inverter you have offers the remote option, but just something to think about.
Yes, a remote switch would be very easy to do. You could even extend the existing switch that is already built in to the inverter and run it to the dash. If I used mine more often I would do just that, however I have only needed it once in 1.5 years. (Solar has taken care of all of my needs.)
I’m not positive that a pure sine inverter is required, but I can imagine that the Magnum inverter/charger may not like a modified sine wave and I would be worried about reducing its service life. If you try it be sure to report back! Thanks for the comment!
Hey Ken! I have learned so much from your videos. I had a question related to how you wired the AC outlets after they came off of the Magnum Inverter/Charger. Did you use a subpanel (Blue Seas), and are the outlets GCFI or not? Would love some guidance in this area. Thanks
Hi Brent, the method you described would be typical. I did a version of that. On my Magnum MMS1012 inverter there’s a blank where an outlet would exist on the 1012-G model. Remove one or two screws and you’ll find the wiring compartment for hooking up the 120V outlets. To save space, I put a Blue Sea 15A breaker inside that space and labeled it “15A AC output breaker inside.” From the breaker the wiring goes to the first outlet, which is a GFCI-type. The two outlets downstream of the first one are regular AC outlets but they are tied to the GFCI terminals of the first breaker, which makes them GFCI just as well. You find your house wired that way too.
So love your website! Thanks Ken!
I am looking at a very modular van build with super simple electrical. And I know nothing about any of this. As such, I am considering a goal zero battery setup. Like the Yeti 1400 along with a couple suitcase solar panels I could charge with.
Any thoughts on this system? I know it’s not the best quality etc but I figure it will provide power for minimal stuff for a couple days.
thanks again!
Perfectly acceptable in a small system. These packaged units take all of the work out of getting an electrical up and running. The downside is the tend to be more expensive per unit of power vs a hand-built one and they tend to be smaller in capacity and not necessarily upgradable. But that said, there are many people out there using them.
Thanks for the complements and following along! -Ken
Hi Ken, I have seen the shower and water system. What are you using for toilet system? Composting,casstte or another system?
Thank you
Hi Juan, I am using this porta pottie: https://amzn.to/3qr2A8t
I didn’t think composting would work well for us since we travel intermittently. This solution works great for us.
-Ken
HI Ken!
You mentioned if you ever had the need for real “shorepower” you could plug your Magnum into an extension cord plugged into a campground/driveway outlet. I was wondering how you ground the Magnum Inverter/Charger to the chassis on the AC side as to avoid the “RV hot skin” condition. I plan on holding off on solar for the moment (and do not want to charge via the alternator) because we are mostly taking 2-3 day trips with 200 Ah of lithium but want to be able to charge via shorepower if needed on longer trips. Thank you again for your copious amounts of Sprinter build knowledge.
Hi Andy,
This issue is unresolved at this point. There’s a 9-page thread on the Sprinter forums right now weighing the pros and cons of a chassis ground. https://sprinter-source.com/forum/showthread.php?t=72005 I would really like to know the answer to this. It wouldn’t take more than 15 minutes for me to run a ground to the body but I haven’t done it yet because I don’t fully understand the consequences. Take a read and let me know what you think. Thanks for the message and the kind words!
Hi Ken,
Can’t thank you enough for taking the time to design this webpage and your videos….you’ve inspired thousands of people I am sure. My wife says your voice is “zen-like” and has actually joined in on this project due to your soothing instruction. My daughter is almost 4 so we’ve gone with a similar rock and roll seat like yours on rails and almost identical layout. My questions are the following if you have time to answer. What size (max wattage) is your induction cooktop and how has it worked with the sized inverter & battery ah? Mine is a max 1500watts but would prefer to go with the same inverter size as you have and cook at a lower wattage. Is your Isotherm 130 Cruise Fridge the elegance version? DC only or AC/DC version? Your 80/20 schematic makes it too easy and just want to make sure I get the correct one as the fridge dimensions do differ slightly depending on the 130 style. Has 200ah been plenty for your needs?
Hi Ryan, thanks for taking the time to leave a comment. Awesome that you’ve got a wife interested in the project…makes it that much more rewarding. Did you end up importing your seat from Uberbus? Very few people have managed to do it.
My induction cooktop is rated to 1500W also. When I turn it on it lets me choose the power setting before it actually starts pulling juice. I think most of them turn on, overload the inverter, then shut off. I turn it on, select a setting of up to 5.5 (out of 10), then it starts going. Setting 5.5 pulls about 940 watts, if I recall correctly. The Magnum inverter has a 5 sec surge capacity of 1750W, 30 sec surge of 1600W, 5 min @ 1200W and 30 min @ 1050W (from the specs), so I believe that gives me a little leeway. It, my microwave and my tea kettle all seem to pull a little under 1% of my battery capacity per minute when run at 1000W. The microwave and tea kettle are generally only on for 2-3 minutes. I haven’t cooked extensively on the induction yet (I’m about to start), but imagine it will hit the battery a bit harder since you’re cooking for longer. For my needs and the amount of solar I can get in the western states, I have never needed more capacity. Of course everyone’s needs are different. My fridge is the 130 Elegance and mine is DC only. I saw no reason to get AC/DC because my van has literally never been plugged in. I hope that helps! Feel free to shoot a message my way if you have any other questions. -Ken
Very grateful for all the information you have shared, thank you very much!
I’m in the planning phase and I’m struggling to find one solar panel that is 300w from the popular RV solar suppliers. I don’t believe you’ve published which solar panel you’ve purchased besides a “300 watt Panasonic”. Would you mind sharing the product and where you purchased it?
Hi Bryan, my panel is a 300W LG panel, model # lg300n1c-g4. This technology is a couple of years old now, so i believe LG has a panel the exact same size now making 350 or 365 watts. I purchased mine locally in Sacramento, CA at AE Solar. My recommendation is to go to your local solar installer *in person* and talk to them about a panel. My experience has been that a call just isn’t enough to motivate them to go into their warehouse to look for a single panel. Others have emailed me back and said this has worked for them. If you can’t get one solar place to look in their shop, then try another. They typically order panels by the pallet and almost always have leftovers from jobs. It’s a matter of finding someone that isn’t too lazy to look!
Great write up Ken. Just wondering, do you think your system has been used to it’s capacity or do you think you’ve overbuilt it? If you lived in Colorado where it’s cold half of the year, would you be worried about the inability to charge the Lithium batteries?
Thanks
I think my system is sized about right. For a long time I never had any significant discharge of the battery when on a trip. Now that I’m occasionally using a microwave and an electric induction cooktop, my power use has gone way up. It’s not until now that I feel like I’m really getting my money’s worth. If you only plan to run a fan, a refrigerator, an Espar and some lights, I probably could have made-due with half the battery power.
Hi Ken!
When using a microwave/cooktop is your discharge significant based of the size of your battery bank? Or do you feel like your battery bank is ample enough to run those appliances when needed?
Everyone’s use case is different but I live and travel on the west coast where there is lots of sun. My battery hits 100% most every day, the exception being rainy days or I’m parked directly under a tree and don’t go anywhere. I use my electric tea kettle every morning for coffee and of course for running my fridge, lighting, recharging devices, etc. The induction cooktop can use a good amount of battery power and quite frankly I don’t use it much because I enjoy cooking outdoors much more. I’d say if regular induction cooking is desired you may want a bit more battery capacity. I could use mine more with my electrical system but choose not to cook inside.
What did you use to mount the A-Series Toggle Circuit Breaker?
Great job!
Hi Tim, I used a PVC Canex box from Home Depot. It’s not quite deep enough…I had to grind a bit of the circuit breaker’s threaded post off the back to get it to fit.
Ken,
Moving on to the next step of electrical system development. I am going to be building the system based on your eloquent design and informative instructions. Thank you.
Question 1:
As we would like to keep van as utilitarian and multipurpose as possible and since it serves more time as a truck to haul farm and building supplies, I am imagining building an electrical component box out of 80/20 almost identical to yours…… with one big difference. I would like it to be removable plug connectors. Do you think this could work?
Question 2:
Our van is constantly carrying 18 -21 foot sea kayaks and surf skis on it’s roof. I have come up with a good system for that but it involves walking on my Front Runner Roof rack. Do you know of a good solid roof rack appropriate solar panel that is strong enough to walk on?
Question 3:
Where is your shore power connection node? Do you just run an extension cord out a door or do you have a plug in point on outside of vehicle?
Again, thank you so much for sharing your knowledge in such a professional manner.
Cwolfe
Hi, to start, thank you for the kind words. Here’s one thing to consider…the inverter is often larger than the lithium battery itself. Can you get away with a Morningstar 300W inverter? They are small and could likely be hard-mounted nearly flush with the wall (using appropriate ventilation of course) and perhaps not need to removed with the battery box. Just a thought.
Anderson power products makes 100 amp (and possibly larger) quick connect terminals. These are often used on vehicle recovery winches. Depending on the size and location of your inverter, I would think this could totally be viable.
I do believe they make solar panels you can walk on. I haven’t researched it though.
For shorepower, I currently have a plug that I would run to an outlet if I needed shorepower. I have only done it once to test it. I’ve always said if I found I needed shorepower more often then I would go to the trouble to put a shorepower outlet under the van so a cable does not have to go through the door. (It’s easily done.) But because I’m not sure I’ll ever need it, I have not put in the effort. There are plenty of sealed marine 120V shorepower inlets available. I hope that helps!
Not sure if anyone had mention, the inverter converts 12v source current to step-up to 120vac output – (10 to 1 ratio). Example, 1200 watt-hour (120vac) would dran 10amps per hour which would draw 100amps per hour from battery sounce. Depending on your electrical load – think of have 2 lithium-ion in series and in parallel…
Just a thought. By the way, Thank you for you wonderful how to instructions – very professional.
Hi Mark, correct on the function of the inverter. Just note that 12 volt batteries “in series and in parallel” would make a 24V system. Thanks for the website visit!
Hi Ken , just starting on my Sprinter with all the upfitting to make it into a wonderful camper and you have helped me out tremendously thank you so much. My question : I had a second Alternator bracket installed at the factory and plan on keeping the systems separate , Off grid is my style as well . With two Lithium Batteries just being charged with the second Alternator would the power be adequate for the lifestyle you are leading and would a smaller Solar panel be adequate ?
Thank you
Hi, thank you for the kind words. I think it really depends on your use-case. If you tend to drive fairly frequently (perhaps every 2-3 days), solely alternator charging might be fine. The solar is really nice in that it’s charging even when you’re sitting, assuming of course that there’s sun. For west coast US travel there has been enough solar charging that I’ve never needed to use my backup alternator charging system. But of course all of this depends on how much you deplete your batteries every day. You could always add a solar panel later or perhaps a ground-deployable one if you wish.
Hi Ken, Great site / YouTubes, I’ve watched them all – more than once, and filling up my build notes. Thanks so much for sharing! I have not bought my Promaster yet and my build is getting more expensive than I wanted. I’m seriously looking at your backup charging solution but after reading through all the posts hear and on the backup YouTube I did not notice you mentioning the charge rate of this solution. I live in Chicago, so I will not have the same Solar performance as you. I will have either 3 or 4 Battleborne batteries that I would like to be able to charge while driving. You mentioned upgrading to a 1,000w sine inverter under the passenger seat. If I did this how long would you anticipate it would take to charge the house batteries? The standard solution of getting a second alternator installed + DC2DC charger adds up quickly.
Hi Eric, as configured my 600w inverter would do 50 amps, but it would likely get hot and shut down as you would pushing the inverter right to its limit. I limit the max charge rate in the Magnum inverter/charger (the unit on the charging end) to 35 amps, so the 600w one is running at about 70% of capacity. 35A*12V = 420W. The Magnum is capable of a 50A charge rate, so a 1,000watt inverter run at 50A (600w) would only be running at 60% of capacity. I hope that makes sense, and if not let me know!
As mentioned in the video, this is a good solution for an inexpensive backup charging solution. If you’re going to charge your batteries a lot via the alternator, the battery-to-battery charger is a better route to go.
Thank you for following along and for your support! -Ken
Thanks Ken, what is the math on 50 amps in terms of how long that would take to charge, say I had three 100 ah battleborn batteries (300) and I got down to 50%. Is the math really that it would only take three hours @ 50 amps to top off the batteries? Basically, I live in Chicago and our summers are very short, winters are long and spring is long and gray. That being said, I don’t care about the inefficiency of DC>AC>AC>DCC I just need to know what my re-charge times are with your solution. And if I can make sense of it, then I will initially go that route. I am spending $$ on Gasoline Hydronic system for heating and hot water and Gasoline for cooktop stove and an aux diesel tank for an marine oven. That said, I am trying to manage my expenses on solar since I do not get a lot here. Again, thanks for all the sharing!
Hi Eric,
The Mercedes body builder guidelines recommends pulling no more than 40 amps from the factory alternator. You can read more about that here: https://sprinter-source.com/forums/index.php?threads/51538/
As such, I follow that limitation. But to answer your question, if you had 50 amps per hour going into your batteries, you would generate 150 amp hours and fill your 300 amp hour capacity batteries from 50% to 100% in roughly 3 hours. Reality is it will take longer because you have to account for the losses in the charger, cabling, and if you were using AGM batteries you’d have to add at least an hour of float time, which isn’t applicable with lithiums. I hope that clarifies a little.
fyi…. it does not seem like your CMS system (workpress) sent out an email that you replied…. I just came back to look.
I’ll look into it; that is a feature this site hasn’t had in the past but it would be nice. Thanks for visiting!
Thank you for clarifying the charge time with your backup solution. I think for phase one and to help keep my costs down, it is a solid solution for me. Thank you so much!
Glad to help. I forgot to add charging losses to my numbers, but if you tell the Magnum the maximum charge amps is 35 amps, the batteries will receive 35 but the second inverter may have to produce about 40 amps to get those 35 to the battery. Take care! -Ken
Hi Ken trying to go with your plans on electrical in my van, I got wiring 14/2, 12/2 16/2 and all those from h. depot and all of them are for low voltage (stranded) the onw that is used for garden lights, you thinks they are the one I should use?? thanks for all the information provided
As long as the wire gauge is matched to the maximum current and properly fused, should be fine. Be sure the wire is soft stranded. Solid core wire is a no-no in a vehicle that bounces around. A good marine wire should offer the best resistance to chemicals, heat, and corrosion. I hope that helps!
Hi Ken, hey thank you so much for the great detail and thoroughness of all your videos and write ups. I am really enjoying them and learning so much.
OK my question, and I am pretty new to all this, so is the Battle Born BMS smart enough that it can manage simultaneous Solar input and Shore power input? Your system isn’t really shore power vs a back up charging method from the Alternator, but I guess my basic question is can you have both these power/charging sources going simultaneously or do you need to shut off the one you are not using?
Hi John,
Yes, the BMS just looks at the whole of inputs and outputs and will trigger an open circuit if specific conditions arise. And to answer your question, if I’m charging (indirectly by alternator or by shore power) at say 35 amps and I flip on the solar, total will be about 54 amps, 19 amps of which is coming from my solar. No need to charge from just one source, as long as the combination of charging sources does not exceed the manufacturer’s recommendations. Thanks for the kind words and for the visit! -Ken
Hello Ken, I have read many of your thorough postings and watched videos. Thank you so much for your hard work. I am not very far from you, working my new 2020 Sprinter starting recently. If I may add one point for this posting: Some inverter/charge can split the incoming shore power and utilize the unused portion to charge battery. Xantrex can do that. This is very important feature, isn’t it? Do you know if all modern inverter/charger have the feature?
Hi Duo, not all inverters have the feature, but of course an inverter/charger combo like the unit I have does. When mine is plugged into shore power it does exactly as you say–it has an automatic transfer switch to feed all of the 120V outlets and uses the remaining power to charge the battery. It’s more compact than having an inverter, a separate charger and a separate transfer switch. -Ken
Hi Ken, you have become one of our key go-to’s in our Camper build, thank you! We really appreciate your attention to detail, sense of integrity and commitment to safety…thank you for sharing all you have so far! One question we’re wondering is about the 15amp breaker you chose to use for your solar panels. I notice you have two of the other switches (the red ones) for the rest of the system, curious why you didn’t use one for the solar…and I’m also wondering how you mount it – I’m having a harder time envisioning how such a circuit breaker (vs. a knob) would get mounted? I was thinking we might use a black two pole knob for the solar system off/on, but it’s twice as much, so maybe if I understood your thinking and mounting plan, it would help me choose the CB instead. Thanks!
Why thank you, that’s a big complement. My breaker choices were solely based on convenient packaging. To keep my electrical box compact, it made sense to take an electrical Canex box from Home Depot and use that to house my solar and DC breakers with the switch type (A-series). (I should mention that I had to grind a small amount off the studs on the back of the A-series breakers to get them to fit in the Canex box.). Once the current passes through the charge controller I had floor space available for mounting the 285-series surface mount breaker. I say it’s mounted to the floor but it’s actually screwed to a piece of wood that is sitting on the floor of the battery compartment. I would choose whichever breaker has the best packaging for your needs. Good luck!
Hi Ken,
I have a 2019 Sprinter that I built out a couple years ago. I relied heavily on your excellent videos and text. Many thanks!
For my electrical system, I have a 120 Ah lithium battery that is currently (Ha!) charged by solar alone. I use the van for winter ski trips a lot, and I’ve been finding it difficult to keep the battery sufficiently charged when it is cloudy and stormy for multiple days. Also, the place I park the van at home gets very minimal winter sun. I have no AC loads, so I don’t need an inverter, but I would like to be able to plug in to shore power at home. What arrangement would you recommend? Is there a particular charger or type of charger that would be best? And how would I wire it in to my system, which I built following your diagram.
Thanks so much!
Matt Noel
Hi Matt, I think these Victron battery chargers would be a good way to go: https://amzn.to/32vKl5k
I have not used this specific unit but Victron makes good quality stuff and it is programmable for lithium. I think this is probably the ticket for you.
As for wiring, it’s simple–just a 120V plug on one end and leads that go to either your battery or electrical buses.
Thank you for the kind words, enjoy your van! -Ken