How-to Charge a Camper Van Electrical System with the Alternator

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In a Camper Van or Motorhome, you’ve already got a generator built-in. It’s called your alternator. The engine spins the alternator which charges your starting battery which powers all of the electrical devices that your vehicle needs on a day to day basis. Spark plugs, ECU, Fuel Pump, Air conditioner blower, radio, and much more. The alternator’s job is to keep that battery full.

Now, you’re converting a van into a camper van and plan on installing ‘house’ batteries to run all of your household stuff like, lights, fans, refrigerator, computers, and such.

For most people, their goal is to power these ‘house’ batteries off of solar, which is great! But when the weather gets cloudy and the charge gets low, it’s nice to be able to charge your batteries on a road trip from point a to point b. This blog post is going to talk about the various ways to charge your house batteries from the Alternator:

Why You SHOULDN’T Use the Alternator to charge your house battery bank:

Something to keep in mind: an alternator is a mechanical device with lots of moving parts. These ‘parts’ will wear out as you use them. The harder you work your alternator, the sooner it will fail. If your alternator stops working; so does your engine until you replace your alternator. This is why, over time, I’ve migrated to a mindset of opting for slower alternator charging (fewer amps) and a way to turn off alternator charging so that the solar panels can do their job, even when driving down the road.

Charging DIY Camper House Batteries with an Isolator

An isolator simply connects your house battery bank to your starting battery. When you turn off your engine, the isolator, “isolates” the two battery banks so that when you use your lights, fans, refrigerator and such, you won’t kill your starting battery, leaving you stranded.

The isolator is simply a pass-through of power and it largely unregulated for the most part in terms of the voltage and amperage that gets sent to the house batteries. The voltage and amperage going to the house batteries is dependent on the voltage regulator and amperage output of your alternator.

How fast will a Battery Isolator Charge a House Battery Bank from the Alternator?

In order to find out how fast our house batteries can charge from the Alternator, we need to know how big of an alternator we have. From there, we can estimate that ABSOLUTE BEST CASE SCENARIO we can anticipate a charging amperage of 70% of the nominal alternator output.

So, if we have a 220 amp alternator… that would mean the most amps we could see coming into our house battery bank is 154 amps. Now… based on real world info gathered from readers of this site, the actual charging rate of a 220 amp alternator is closer to 100 amps.

This means that if we were pushing 100 amps into our house battery bank over the course of an hours drive, we will have refilled 100 amp hours into our house battery bank.

This is also a very rough figure because as the batteries get closer to full, the slower they will charge.

So, to answer the question: “How fast will my house battery bank recharge while I’m driving?” You could VERY roughly calculate 50% of your alternator size in amps times the number of hours you are driving, and this will tell you how many amp hours will be pushed back into your battery bank.

Pros of Charging Camper House Batteries with an Isolator:

  • It can charge at a rapid rate, over 100 amps in certain cases.
  • Isolators are less expensive than battery to battery chargers
  • Isolators have the capability to jump-start a weak starting battery in emergency scenarios.

Cons of Charging Camper Batteries with an Isolator:

  • Higher charging rates can lead to premature alternator wear and potentially alternator overheating.
  • It’s likely that your alternator does not put out high enough voltage to charge Lithium batteries to 100%
    • Lithium Batteries generally need to be charged at 14.4-14.6 volts once they get near 100%
    • Vehicle Alternators generally put out 13.5V to 14.5V depending on their quality, design, and age.
  • Large wire size, potentially up to 2/0 wire, should be used due to minimizing voltage drop (Less than 3%) while accommodating high charging rates.
  • Varying alternator sizes and vehicle setups make predicting charging rates with accuracy, difficult.
  • If the Isolator is not specifically designed for Lithium, it’s connect/disconnect parameters will be too low for use with Lithium batteries and may not disconnect the house and starting battery bank properly when the engine is off.

Charging DIY Camper Batteries with an Li-BIM

The Li-BIM (Lithium Ion Battery Isolation Manager) is a popular isolator designed specifically for use with Lithium Batteries. It has higher voltage open/close parameters that allow the isolator to open and close at more appropriate times depending on if the alternator is charging the house battery bank or shore/solar is able to charge the starting battery.

The most unique thing about this isolator is it attempts to combat alternator overheating by providing time based ‘cycling’. This means that when the engine is running and the isolator is allowing the house battery bank to charge, the Li-BIM will allow charge for 15 minutes, disconnect charge for 20 minutes to allow the alternator to cool, reconnect for 15 minutes, disconnect for 20 minutes, and this cycle will continue the entire time the engine is running. This takes some stress off of the Alternator.

How fast will the Li-BIM charge my house battery bank from the Alternator?

Since the Li-Bim allows charging for 15 minues and then disconnects for 20 minutes, this means that it is only charging for 42% of the time.

Now, Using the same specs from earlier. If we have a 220 amp alternator that is charging our house battery bank at, say, 100 amps; this means that it would be pushing 100 amps into our battery bank, 42% of every hour we are driving. This would give us 42 amp hours into our battery bank for every hour we are driving.

Pros of Charging Camper House Batteries with the Li-BIM Isolator

  • It can charge at a rapid rate, potentially over 100 amps depending on the vehicle.
  • It is an isolator with voltage connection/disconnection set-points specific for Lithium Batteries.
  • The Li-BIM has the capability to jump-start a weak starting battery in emergency scenarios.
  • The time-based charging ‘breaks’ allow the alternator to cool between high amperage charging rounds.

Cons of Charging Camper Batteries with an Li-BIM Isolator:

  • Higher charging rates can lead to premature alternator wear.
  • It’s likely that your alternator does not put out high enough voltage to charge Lithium batteries to 100%
    • Lithium Batteries generally need to be charged at 14.4-14.6 volts once they get near 100%
    • Vehicle Alternators generally put out 13.5V to 14.5V depending on their quality, design, and age.
    • Although the Li-BIM is designed specifically for lithium, it cannot and does not boost voltage in any way.
  • Large wire size, potentially up to 2/0 wire, should be used due to minimizing voltage drop (Less than 3%) while accommodating high charging rates.
  • Varying alternator sizes and vehicle setups make predicting charging rates with accuracy, difficult.

Charging DIY Camper Batteries with a B2B (Battery to Battery) Charger

A battery to battery charger takes the voltage and amperage that is being put out by the vehicle alternator and regulates the amperage down to a modest pre-set level and boosts the voltage as necessary to fully charge any batteries.

This decrease in amperage lowers the strain of your alternator greatly and also gives us a solid number from which to work with when being able to accurately determine how many amps the charger will operate at.

The boost in voltage is INCREDIBLY important for being able to charge higher voltage lithium batteries from alternator that can’t quite put out that much voltage. If the power from the alternator is hitting the DC-DC Charger at 13.8V and the Batteries need to be charged at 14.6V, the DC-DC Charger will boost the 13.8V from the alternator to the 14.6V the batteries require. On DC-DC Chargers, this voltage is also programmable so it will work for Lithium, AGM, Carbon Foam, Salt Water, or whatever other battery type you throw at it.

How fast will a DC-DC Charger charge my house batteries from the Alternator?

Each DC-DC Charger has it’s own charging rates. For example, the Victron Orion 12|12 – 30 will charge your house battery bank at 30 amps. This means, that if you drive for an hour, you will push 30 amp hours back into your battery bank.

Pros of Charging Camper House Batteries with a B2B (Battery to Battery Charger.

  • Can regulate amperage making system planning easier and decreases wear and tear on the alternator.
  • Can deliver a specific programmable ‘charging profile’ to the batteries.
  • Can boost sub-optimal voltage to a level needed to charge batteries to 100%
  • Some models of DC-DC Chargers can be run in parallel, providing more amps if necessary.

Cons of Charging Camper House Batteries with a B2B (Battery to Battery Charger.

Final Thoughts: Isolator vs DC-DC Charger

Since the introduction of the Victron Orion 12|12-30 DC-DC Charger, I have been all aboard the DC-DC charger train. The biggest selling point for me is the voltage boost. Having a device that will boost the voltage of an underperforming alternator to the 14.4-14.6V it takes to charge lithium batteries like our Battle Born batteries, is the main selling point for me. As much as I would like 100+ amps coming to my batteries, sometimes it’s risk vs reward and getting towed to the shop or performing a parking lot alternator change due to an overworked/overheated alternator, just plain sucks, IMO; but please use your own judgement when making this decision for your own camper.


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103 Responses

  1. Hey Nate, thank you for all of your knowledge you share with us.

    Quick question, I noticed that on your youtube sprinter builds you use the ground under the drivers seat for the Orion Isolated dc-dc charger. Have you had any issues with that ground? I have been told that it needs to be connect directly to my starter batteries negative terminal but my sprinter doesn’t have any extra mounting points. Thoughts?

  2. Hey Nate! We are looking to wire our Orion-TR Smart 12/12V-30A Isolated Charger to the alternator but our 2021 Ford Transit has a 175 A CCP on the seat, but there is no ground. Based on the wiring diagram we purchased, we are unsure where to run the black wire from the Orion to.

    Does that need to be grounded to the chassis? If so, should that wire be the same length as the red wire going to the alternator?

    1. The negative should indeed go to a ground location as close to the starting battery or CCP as possible, but the wire lengths do not need to be identical; just ‘as close as feasible’.

  3. Hey Nate,

    Thanks for your inputs mate, very appreciated!

    Quick one, can the Victron Orion B2B “ISOLATED” model work well in an scenario where the start battery negative pole is earthed? Or only the “NON-ISOLATED” can work well in that case?

    Thank you!

  4. Hi Nate, I’m designing my system around your wiring diagram for a 400ah battery bank (only have 200ah to start) with all your recommended Victron components. I’m installing the Orion 12/12 30 charger, but it’s the non-isolated model as opposed to the isolated model in your diagram. Would I run the positive wire from the Orion to a connection on the positive bus bar of the Lynx Distributor and just not have a corresponding negative wire coming off the Lynx? Or, should I run that positive wire directly to the positive terminal of my lead battery instead? For the ground wire out of the Orion, can I connect that to the load side of my Shunt which will have a ground wire coming off to chassis already?
    Thank you so much for all you do!

    1. @Nate Yarbrough, do you recommend the isolated over the non-isolated? Any reason to choose one over the other?

  5. Hey Nate, I just bought 2 wiring diagrams and ordering the Lynx Adaptor next. Few questions, does the 2nd Lynx Adaptor go between the main cut off and the Lynx Distributor? Your wiring diagram should 9 cables going into the Lynx Distributor but it only had 4 connections, help? The WFCO AC-DC distribution panel is out of stock, do you recommend another product or source?

    1. The other lynx Adapter goes between the Shunt (from the BMV-712 Battery Monitor) and the Lynx Distributor. The lynx distributor does indeed have 9 connections. 4 positive and 4 negative with an additional stud on the negative busbar that I use for equipment grounds.

  6. I’ve got what is probably a pretty stupid question… but here goes anyway… is there any reason I can’t just use a regular old battery charger?.. .Scenario.. I have a 2,000 watt inverter, that was connected to the starting battery in my old Town & Country… plan on switching it over to the 97 e350 that I am building out for when I am working on the road. I have 1 marine battery (nothing fancy, just something i bought at Auto Zone) that I use right now for emergency computer use when I am on the road and don’t want to set up the generator (usually gets me through 1 full deadline cycle)… I plan on getting a second marine battery, similar to the first, to have in the new (to me) van, and I keep reading all this about B2B chargers and isolators, and I can’t help but wonder, since i am going to have the 2000 inverter permanently connected to the van’s starting battery, and the inverter housed inside the van, couldnt i just plug my regular battery charger (
    Schumacher SC1280 6/12v Rapid Battery Charger/maintainer) into the inverter, and use it to charge the marine batteries while i am driving? that seems easier, and cheaper than buying, for example, the 240-Watt 12-Volt DC to DC Solar On-Board Battery Charger for $118… I’m sure there is a reason I can’t (shouldn’t) do what I outlined, but I can’t figure out what it is!

  7. I’m planning on putting a second alternator in my van dedicated to charging the 24v 600Ah battery bank in my trailer. I’m looking at Sterling equipment – two 35a 24v chargers that have a built in 12-24v converter. When I hook this into my system, I would assume that there would need to be a switch to choose EITHER alternator charging or solar. Is there any way to simply have the system automatically select the one that is providing more power?

  8. Finally received my batteries and have everything together for the install. Quick question for you. I am running my alternator feed from the vehicle battery to an isolated Orion DC to Dc. I’m connecting the 4awg to a terminal block, then downsizing to 6awg near the unit to fit in the Orion’s terminal port. I want to utilize the multiplus’s second battery or vehicle battery feature. My plan was to connect the leads from the multi plus to the incoming terminal block, which when plugged into shore power would do just what I need it to do and charge the vehicle battery.

    1) see any issues doing that?
    2) Do you know if the multiplus will support two battery types? (House is lithium)

    1. 1: Use 6 AWG wire for your alternator to Orion connection even though there may be a bit more voltage drop than you are used to.

      Here’s why… If there is more voltage drop than normal… it’s not a big deal because the entire purpose of the Orion is to boost voltage. As long as the voltage is hitting the Orion at greater than 8V (Which would be nearly 50% voltage drop if your alternator is putting out 14V), the Orion will boost the voltage back up to where it needs to be (13-14.whatever)
      CAN you use bigger wire? Sure, I guess… but since 6 AWG wire won’t fit into the terminal… you have to start using junction studs or busbars to make the connection from the bigger wire to the smaller wire which is messy, adds additional points of resistance and failure and ultimately unnecessary for the reason I gave above.

      2: The multiplus starter battery trickle charge will charge at the same charging profile as the house battery bank. You could use another (Smaller) orion between the multiplus and the starting battery to introduce a proper charging profile if desired.

  9. Hi Nate, Thanks for all of your information; much appreciate it. I’m using the Orion-TR 12|12-30 to charge from my alternator. If I’m running both positive and negative cables from the unit to my start battery, is there any reason to have a chassis ground from my batteries to the van’s body?


  10. Hi Nate, thanks for all of these great articles! I’ve just started watching and reading and I’ve got a pretty good overview of what I need to do, but so far, I haven’t been able to figure out where my on board propane generator gets added to the system. Are there available inputs on the Victron charge/inverter? Do I need additional equipment to protect the system if the generator is running while the solar is active or, say, if shore power were to come back on while the generator was running?

  11. Hi,I’m using a Victron Battery to Battery 30amp charger what size fuse do I use in the Victron Linx? Is 60 amp to large?
    Joe M.

  12. Hi Nate,
    my Motorhome currently has a +Positive wire coming from the alternator/Truck Battery back to my house batteries and was connected to the positive terminal on one of the batteries directly. I am replacing my lead acid batteries with lithium ion batteries and using the Victron Distributor as pictured in your plan, can I use the new Victron Energy Orion-Tr Smart 12/12-Volt 30 amp 360-Watt DC-DC Charger in place of the Victron Orion Smart 12|12 – 30A? And If so can I use the positive wire coming in currently and hook that into the Victron Distributor? Do I need to run a second line for the negative from the alternator or cannot be connected to the ground?

    1. You would need to run a new wire as the OEM wire is likely too small to handle the full 30A for the Orion. Make the new truck to trailer connection with an Anderson connector.

  13. I plan on using the Orion 12|12-30 DC-DC Charger and the Victron 100/30 smart mppt charger. They both are rated at 30a. If I have a 200ah battery with a max charge current of 50a will I damage the battery? And further more if I had a 25a Victron ac to dc charger and happened to have all three charging at once ( not likely but it could happen) would this push 85a Nd be a problem?


    1. They all won’t charge at the same time, but you should monitor while charging through your BMV-712 for the first few times to make sure. If that’s a lithium battery, though… the BMS should limit charging input before the battery gets damaged, though (if it is a good quality battery/BMS).

  14. Hi Nate,

    I am building a trailer and have purchased the wiring diagram for your “Budget Friendly” system using the Renogy products and was wondering if you have done any research or heard anything about the DC-DC MPPT Charger Renogy came out with? I was looking at purchasing the Rover Solar Controller and the 60A DC-DC battery charger but thought this new product might work since it seems like it is both of those combined into one product.

    Any thoughts or advice you have would be greatly appreciated.

    Thanks for all of your time and work you have put into the diagrams and videos. It is greatly appreciated and very helpful.

    1. Yep! I don’t like it. The max solar voltage input is only 25V which is way too low (in my opinion) for an MPPT to properly function. This low of a voltage input will also SEVERELY limit the ability to use more than 2 panels in the array as you are FORCED to wire in parallel only.

  15. Hi Nate,
    First thank you for doing all this – your blog and videos are extremely helpful!!!

    I have a Winnebago View (24v) Sprinter chassis. I have 300ah lithium batteries and have ordered the Victron Orion-Tr Smart DC/DC charger. I’ve reviewed your wiring diagrams, but do not see any connections to the ignition. Isn’t this required for the charger to stop when the engine is not on?


    1. Not always. It generally works without it. Consult with the user manual as there are a few different configurations for ignition signal wires depending on your individual setup.

  16. Hi Nate
    Great stuff! For a 2008 Sprinter 3500 could i connect a Orion Tr-Smart 12/12-30 to the auxillary battery under the drivers seat. The house bank is 420 Ahs AGM. Thanks, Vic

  17. hi Nate! thanks for all the informations and help you give here.
    I’m planning to install a 280Ah lifepo4 battery on old van, using a Victron Orion 12|12–30, but I’m still worried that it could be too much for the small 55Ah alternator.
    do you know if I can configure the orion to reduce the charging amperage is necessary?
    thanks in advance

  18. Very straightforward answers. Thanks.

    I see comments about adding a second alternator. It seems that the only advantage would be lack of wear and tear on the primary alternator. All other considerations still apply. Are there any other advantages from adding an alternator?

  19. You mention that an alternator might not be able to charge lithium batteries to 100%, but will it still get them to 80 or 90%? I have a brand new Promaster with the 220A alternator?

    1. @Nate Yarbrough, Thank you, Sir. Another question: using your B-to-Battery charge calculator, with 220A alternator, 300Ah of lithium, you recommend a 60A B-to-Battery charger, but all I can find with Victron is their Orion TR Smart at 30A–is there a 60A charger out there?

  20. Thanks for your videos and guides. We just bought a van and I’m trying to get a handle on exactly what kind of budget I need to move forward with my build. My plan was to have 2 panels on the roof lined up on the passenger side, two fans and decking over the drivers side to be used to transport a kayak and have a walkway for cleaning and maintenance on the panels.

    After using your calculator the spreadsheet recommended 300ah of battery storage and 600watts of solar. Needless to say I don’t think I can fit what I want on the roof and have 600 watts of solar up there. The spread sheet doesn’t take into account charging the house banks with the alternator. We don’t plan to spend more than a few days in a spot without driving so about how much does the battery isolator offset the solar needs?

    1. The calculator doesn’t and can’t take that into effect because I don’t have any data on how much each person will drive on a daily basis. The sun is predictable… driving habits are not. So; just fit as many panels as you can with an end goal of 600w and if you can’t fit that much, just know that you may need to supplement with running your engine or a generator.

    2. @Nate Yarbrough, Hi, so a 60amp renogy dc to dc charger for 300ah batteries is too much amps to run off my promaster? I do have solar panels but using for night time driving/charging of course. Appreciate any info, thanks Mike

  21. Question, it seams like in your wiring diagrams that the only thing that you have on the line side of the disconnect switch is the battery bank. Is there a compelling reason that you also don’t have the alternator, shoreline and the solar not on the line side of the mains power switch as well?

    1. The way I have it designed in my diagrams makes it so that we can use fewer parts/pieces and keeps the physical footprint smaller. If you wanted some things on one side of the switch and some on the other, it just starts to really add up in the additional parts required.

  22. Hi Nate,
    After using the alternator calculator, it was recommended that I use a 60A b2b charger. This sounds like a dumb question in my head, but is there a risk in using a b2b that is rated for less amperage, like the Victron 12/12-30?

  23. Hi, Nate,

    What are your thoughts on using the Sterling Power Battery to Battery 60 amp DC to DC Converter in your system rather than the Victron Orion 30 amp model that you spec. I understand that Sterling makes quality components, and this seems like it would double the charging input power to the house battery bank, but not sure if it would work well with your system or if there are other considerations that I am missing.


    1. If you are using Victron components (Multiplus Inverter Charger & Smartsolar MPPT), I highly recommend the Victron unit over the Sterling so that all of the components can ‘talk’ to each other for temperatures, voltages and such. Also… Victron is working on a firmware update so that solar and alternator can synchronize charging and charge from both sources at the same time. You will NEVER have that capability with the Sterlilng unit.

  24. Nate,
    I bought your 400-600ah wiring diagram and I’m thinking I should probably have two Victron Orion TR-Smart 12|12-30 so I can parallel them to get a total of 60amps. I’m going with 600ah batteries so I’m thinking I need more recharging juice during our excursions. Could you please let me know how to achieve the parallel connection with any recommended parts? I was initially thinking to have a separate bus bar for the line coming from the starter battery and to split off onto the inputs of the two Orions’. From there, the outputs of the Orions would land onto one pole in the Lynx Distributor with a 90 or 100 amp fuse. Have a great week!

    1. There are a few ways to accomplish that and without diving into a whole new diagram or something, the most straightforward way is to get a 2nd Victron Lynx so you have 4 additional spaces for devices and effectively ‘copy paste’ the orion charging leg of the system over one space.

      You can do as you proposed, but the fusing gets more tricky that what I can explain in a comment here.

  25. Hi, great work!
    I cannot find information about 24V (2S2P) installation.
    Do Orion TR-Smart 12|12-30 run on 24V instalation, if yes then how to connect it? Is there an option to boost voltage in Victron App to about 26-28V?
    Does it requires some kind of BMS?
    Thanx for the repy!

  26. Hi Nate,

    I hope you are doing well. What are your thoughts on the Victron Orion 50 amp Buck Boost DC-DC Converter? Can this be used as a charger as well?

    1. If you are using Victron components (Multiplus Inverter Charger & Smartsolar MPPT), I highly recommend the Victron unit over the Sterling so that all of the components can ‘talk’ to each other for temperatures, voltages and such. Also… Victron is working on a firmware update so that solar and alternator can synchronize charging and charge from both sources at the same time. You will NEVER have that capability with the Sterlilng unit.

  27. Nate, I tried using the Alternator Charging Calculator. But after the first result I kept coming up with the same Result, even with an input of only 40 amps. The calculator does not seem to be resetting properly.
    Recommended Alternator Charging Method60A B2B Charger
    Estimated Max Charging Rate (Amps)60
    Alternator Size (Amps)
    Battery Bank Size (Amp Hours)
    Battery Type

    What’s Most Important?

    Alternator Heath
    Is Self Jump-Starting Important to You?


  28. Hi Nate,
    Thx for your support.
    I came across the opinion that using Victron Cyrix-LI-ct battery combiner for alternator charging would be the safe option that won’t harm the alternator. What is your opinion? Any pros and cons of such option? My setup would be : alternator from the 80′ and the LiFePO4 on the other end.
    Take care!

  29. Hi Nate, really appreciate your guidance and instructional videos to get a grip on motorhome/van electrical systems. Awesome work.
    I have an older motorhome and am putting solar into it. The coach currently has an isolator. Can this be removed if I use the sterling B-B charger, or should I install the charger between existing isolator and the Lithium battery bank? Thanks in advance.


  30. What do you think about victron energy’s Cyrix-i battery combination because I don’t have much information about it yet

  31. Hi Nate,
    Good stuff. I recently decided to move away from the isolator that came with my truck camper. After paying $900 for a couple of 6-volt AGM batteries with a total of 300Ah I am motivated to protect my investment and get the maximum life from these batteries. So I added a 50 amp DC-DC Charger. This now provides a 3-phase charging profile that matches what my battery needs to charge it 100% and limit the current during the absorption and float phases of recharging. Otherwise there is no limit on the amperage going through an isolator and this could be detrimental to the battery life. In addition, some systems with lower Ah batteries would be getting overcharged even during the bulk phase. The DC-DC Chargers allow you to program the maximum amperage to eliminate this problem as well. The cost will be offset if I can get another couple of years out of my batteries. Keep up the good work Amigo.

  32. Hi, and thanks so much for your tutorials. This is the part of van building where I’m most out of my depth! Your calculator recommends the Blue Sea add-a-battery kit. I am sure it works based on alternator capacity and hose battery type, and I would like the ability to jump my start battery from the house bank if necessary! However, I was under the impression that I absolutely needed a B2B charger if my vehicle has a “smart” alternator. 1) Is this true, and 2) how can I determine if my 2009 GMC van has a “smart” alternator anyway?!? Please pardon my ignorance here…

    1. I’m going to guess that your 2009 vehicle does NOT have a smart alternator. There should be a sensor of some kind on top of your starting battery if you have a smart alternator. In that case, you should be able to simply use an isolator like suggested.

  33. I’ve been following for a while now and your videos and tutorials are so good and easy to follow. Just one question. I have an Orion dc/dc smart charger, does that type of charger simply wire directly into the starting batteries and then into the house battery’s or do you have to run a wire to the alternator?

  34. I have the Battle Born / Precision Smart Isolator and it’s all hooked up, my Battle Born 100AH is below 13.4 which allows for a charge, but it says it does not charge when voltage above 14.4. I can clear say with a volt meter that 14.7-15 amps are coming in to the isolator, and therefor not going out of the isolator as the other side of the isolator registers my current battery voltage. I have a 2019. Anyone have this problem with the vehicle putting out too high of voltage??

  35. Isn’t the real danger of a depleted lithium battery bank that it might ask for too many amps from your alternator and shorten its lifespan or leave you stranded? I plan on 3 Battle Born batteries and if they’re run down to 20%, when I start my van, that battery bank will be able to accept the maximum amperage from my alternator, won’t it? What are the chances that overheats my alternator? 97 E450 Super Duty BoxVan with a 7.3 liter Power Stroke diesel for reference. I would like to be able to send the battery bank 150 amps for maximum recharge during a short drive, that’s a major selling point for lithium batteries. Thanks for all the great videos.

    1. Yes. That’s definitely the downside of charging with an Isolator. A battery to battery charger would decrease wear and tear on the alternator. I’ve got a diagram out now that features a battery to battery charger:

      But if you are wanting to send 150A, yes you will risk alternator damage depending on how long that load is applied. That is the tradeoff when trying to charge quickly. Remember, an alternator is a mechanical device. The harder you work it, the more wear it will endure.

  36. Hi Nate, I’m looking to put a 12v 800ah lithium Iron “house” battery bank in my not yet purchased RAM Promaster charging both it and my starter battery off of a single, beefed up, (Nations maybe) alternator. Later I’ll add solar panels as well. Is the single alternator doable while protecting both the house bank and starter battery from issues? What other “magic” devices will I need in a system like this?

  37. Nate, thank you for all you do. Your knowledge is impressive and I appreciate you sharing it with us.

    Do I need a battery to battery charger such as a sterling if I am using a Goal Zero Yeti with the Yeti Link? If my Yeti is at the back of the van (30 foot run to under the front seat…2019 sprinter 144 4×4), I see people recommending 8 gauge wire…does that seem small?


      1. Goal Zero makes a product called Yeti Lithium 12v Car Charging Cable, which connects a 12v car outlet to one of their Yeti power stations. What is your take on this arrangement?

  38. Thanks for all this info! The datasheet for the Victron LFP-Smart 12,8/100 battery states a recommended charge current of <= 50A, and a max charge current of 200A. I won't go into all the details, but to summarize an email from Victron, charging at rates higher than 50A may effect the life of the cells and above 200A may physically damage the battery.

    Since a battery isolator does nothing to limit the charging current, whereas a b-to-b charger regulates the charging current to a known safe amount, I don't understand the popularity of the isolator. Unless you know for sure that your alternator output will never exceed the recommended charge current for your battery, it seems risky.

    My 2019 gas sprinter has a 250A alternator, and I plan to have two 100Ah batteries and therefore would prefer to limit the current to 100A. How do I know my alternator would never put out more than that?

  39. 1. I am replacing a 685 cca Deep cycle marine battery, (house battery), with a 100Ah AGM battery. I used to charge the Dcmb through a Battery Isolator. Can I do the same with the AGM? I have a 2013 Ford F-150.
    2. I also bought a 20A MPPT solar controller so that if I am parked somewhere I can use one of my 100W PV panels to charge the AGM battery as needed.
    I would guess that the PV panels go to the Charge Controller and the Charge controller to the battery. And the Line from the Battery Isolator would go to the Battery also. Am I thinking wrong to do both at the same time? Do I need other equipment?

  40. Hi Nate,

    1. If my energy usage/day ~40Ah, and I’m driving every other day, could I get away with only B2B charger without solar and only a single 100A Battle Born Battery? (I have a used 2007 Sprinter with after-market alternator of unknown Amps).

    2. How many hours of driving does it take to fully charge a 100A BBB(Li) with…. a) 30A B2B ..vs.. b) 60A B2B?

    3. What would happen if I use the 60A Sterling B2B with only one 100A Battle Born Lithium battery? (basically can I get away with this even if it isn’t ideal for the battery?)

    4. Do I have to wire the Sterling B2B charger to an ignition wire or will it turn on automatically? (I’m intimidated by wiring to ignition).

    Thanks! These articles are pure gold!!

    1. Hey Alex! So, as much as I love Battle Born batteries; I don’t know that going that route in such a small system is what I’d recommend. Personally, for a system that small; I’d be going with a goal zero Lithium unit.

  41. Thanks very much for the great advice, I’m a marine electrical engineer with 35 year experience, 30 of that in the Navy, and am very impressed with your knowledge and pragmatic approach. I have found the product advice very useful. My question is, “most inbuilt BMS have a relatively low max charge rate. Is there a risk of a direct alternator connection through an isolator overloading these. Thanks

    1. The Battle Born batteries have a recommended max charge rate of 50 Amps per 100 Amp Hour battery; so It’s recommended to take your Alternator output, multiply that by 70% (since alternators don’t put out what they are rated for (basically)), and make sure your battery bank size is within that parameter.

      1. Nate, thanks for another great article. My Sprinter conversion is all electric /w 620W solar and a 60W Sterling B2B and a Victron Multiplus 3000 all connected to solid copper bus bars per your directions.

        You provide solidly reasoned advice and it is much appreciated.

        Happy trails.

  42. I am also wiring my BIM isolator from Battle Born. I can find nothing to show me where and how to wire the ignition wire and where is the +(red) wire with the manual switch going to to get the 12v( to the +bus bar or house battery.. and does the 2/0 red get hooked right on to the + pole of the van battery. I have a Ford Transit 250 with the battery under the drivers seat. Also want some info on how to get you a couple hundred$. I can do PayPal.

    1. The ‘IGN’ wire goes to any circuit that is ‘hot’ only when the van is clicked to the on position. You can make this attachment with an “Add-a-Fuse” connector:

      The 2/0 red does hood directly to the positive battery terminal of the van. Fuse it with a terminal fuse:

  43. I am wondering if you can go into more detail on the li-bim 226 isolator on where yo wore the ign to and the sign.

    1. I think that if you have a secondary alternator, you will be able to drive more power for longer to your house batteries than you could with a single alternator.

    2. I come from a car stereo background and there is a company called Mechman, they make high power alternators in my ford e150 I have a 350 amp Mechman alternator ( this is tested and true 350 amps ) it puts out 200 amps at idle for car stereo systems with 2000 to 3000 watts this is power needed, my van with my 2344rms watt stereo system runs at 14.6 to 14.8 volts that’s when I’m cranking the bass so that people think it’s thundering it runs at 14.8 to15.1 volts with stereo system off. So charging solar batteries from my alternator has no harmful or stressful problems caused to my vans electrical system, just FYI hope this helps some of you that feel you need to use your vans electrical to help your solar power and worry about messing up your vehicles alternator.

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