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Dual Batteries and Alternator Power

747 Views 9 Replies 6 Participants Last post by  Paulmorabito
hi!
To start and for the next few years my power needs for my van conversion will be webasto heater and max air fan. Down the road I would love to run a hot water heater and an electric stove top.

As I gather funds Is it possible to run a max air fan and Webasto heater using the factory installed dual alternator and dual batteries?

Any reason why a separate system might be better over dual alternator and batteries thinking of long term investment and power needs??
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I can't speak to how feasible it is to run those two things now off the start bank because I'm not sure what sort of draws you would have with the heater. The Maxx Fan (especially if non low) is more likely to be okay, but a heater would be more of a load.

Any reason why a separate system might be better over dual alternator and batteries thinking of long term investment and power needs??
But as for your question above: why a separate "house" system may be better, I can think of a couple of reasons:

1) In my world, start batteries are sacred. Would I charge a phone or maybe run a marine fan on low off the start battery? Sure. But something like a furnace seems like it could catch up to you at just the wrong time (cold weather). What I mean is, you could run your start bank down so that you wouldn't be able to start. Having a house bank of some kind leaves the start batteries untouched, so they are always "safe."

2) A separate house bank means one can make it larger, charge it as one sees fit (you have full control vs. Ford meddling), etc. How large it might need to be and what type of system one wants vary according to needs, budget, inclination and the like.

The typical setup ("traditionally") would be a start bank that just starts the engine, then a separate house bank that just runs the house loads. Where the twain may meet is with a charger that takes alternator power and sends it to the house bank when you are driving; but those generally do NOT allow the house to use start-bank power (IOW, when the engine isn't running, there is a "wall" between the start and house banks), so start bank is still sacred.

I said "traditionally" because these days there are other options. Minimal loads, you install monitoring and keep an eye on things, etc.? Maybe just using the start bank for both and carry (and keep charged) a jump pack. Or, there are the all-in-one power banks (Jackery, Goal Zero, etc.) These are newer ideas and may be just fine depending on your use-case (tho the heater would still make me nervous running off the start bank).
 

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Discussion Starter · #3 ·
I can't speak to how feasible it is to run those two things now off the start bank because I'm not sure what sort of draws you would have with the heater. The Maxx Fan (especially if non low) is more likely to be okay, but a heater would be more of a load.



But as for your question above: why a separate "house" system may be better, I can think of a couple of reasons:

1) In my world, start batteries are sacred. Would I charge a phone or maybe run a marine fan on low off the start battery? Sure. But something like a furnace seems like it could catch up to you at just the wrong time (cold weather). What I mean is, you could run your start bank down so that you wouldn't be able to start. Having a house bank of some kind leaves the start batteries untouched, so they are always "safe."

2) A separate house bank means one can make it larger, charge it as one sees fit (you have full control vs. Ford meddling), etc. How large it might need to be and what type of system one wants vary according to needs, budget, inclination and the like.

The typical setup ("traditionally") would be a start bank that just starts the engine, then a separate house bank that just runs the house loads. Where the twain may meet is with a charger that takes alternator power and sends it to the house bank when you are driving; but those generally do NOT allow the house to use start-bank power, so start bank is still sacred.

I said "traditionally" because these days there are other options. Minimal loads, you install monitoring and keep an eye on things, etc.? Maybe just using the start bank for both and carry (and keep charged) a jump pack. Or, there are the all-in-one power banks (Jackery, Goal Zero, etc.) These are newer ideas and may be just fine depending on your use-case (tho the heater would still make me nervous running off the start bank).
Thank you so much for your input! I appreciate that!
 

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You are most welcome. One of the reasons it's hard to "know" is that there isn't one hard-and-fast right or wrong answer.

Another thing I may have alluded to but not directly is how often you drive. With even a single alternator (much less duals), you are going to be topping the start banks off really quickly when driving.

So even with a heater..... one night between two driving days? That might be okay. (Obviously it will run more or less depending on the outside temp and how warm you set the thermostat.)

I believe that @gregoryx used just his dual start batts (and dual alternators) at first -- and even though he has a big house bank now, he still has a switch where he can go back to that if for some reason his house bank goes kaput. Maybe now that I have tagged him he'll chime in and let you know if he ran a heater or similar on that setup.
 

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I believe that @gregoryx used just his dual start batts (and dual alternators) at first -- and even though he has a big house bank now, he still has a switch where he can go back to that if for some reason his house bank goes kaput. Maybe now that I have tagged him he'll chime in and let you know if he ran a heater or similar on that setup.
Indeed. I ran about two months that way - 2-3 short trips in that time.

Initial install was getting the CCP1 & CCP2 out to two circuit breakers (50A & 120A - 'cause I had a 120A laying around) and a big ground point to a busbar. Then install the inverter for any 120VAC loads. In our case, that inverter would be used later to charge the large house batteries and the CCP1 50A would feed the 12VDC "backup" power for the main house loads.

We ran the MaxxFan, lights, water pump... just basic stuff. Plus the inverter, which we used to make espresso at least. But no water heater. We didn't have the space heater installed yet, so didn't really test the power draw it has; pretty sure someone has documented that on this forum, IIRC.

Here you can see the lines coming from CCP1 & CCP2 in the bottom right, the 4/0 ground line, and the fuse box for house 12VDC loads in the upper left.
Bumper Motor vehicle Automotive exterior Grille Gas



After we finished the bed and galley builds, then we installed the large house electronics system and switched around how those "truck side" electronics work - relegating the inverter to a charging-inverter (and backup to the house 120VAC by moving a plug) and the CCP1 source to the backup for 12VDC loads (on an A/B switch). The fuse panel was moved back with the house system (and supported through that A/B switch).

Motor vehicle Electrical wiring Automotive exterior Wood Trunk


FWIW, this is how it looks "in use" - all covered up.
Land vehicle Vehicle Motor vehicle Automotive tire Automotive exterior
 

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Discussion Starter · #6 ·
Indeed. I ran about two months that way - 2-3 short trips in that time.

Initial install was getting the CCP1 & CCP2 out to two circuit breakers (50A & 120A - 'cause I had a 120A laying around) and a big ground point to a busbar. Then install the inverter for any 120VAC loads. In our case, that inverter would be used later to charge the large house batteries and the CCP1 50A would feed the 12VDC "backup" power for the main house loads.

We ran the MaxxFan, lights, water pump... just basic stuff. Plus the inverter, which we used to make espresso at least. But no water heater. We didn't have the space heater installed yet, so didn't really test the power draw it has; pretty sure someone has documented that on this forum, IIRC.

Here you can see the lines coming from CCP1 & CCP2 in the bottom right, the 4/0 ground line, and the fuse box for house 12VDC loads in the upper left.
View attachment 179409


After we finished the bed and galley builds, then we installed the large house electronics system and switched around how those "truck side" electronics work - relegating the inverter to a charging-inverter (and backup to the house 120VAC by moving a plug) and the CCP1 source to the backup for 12VDC loads (on an A/B switch). The fuse panel was moved back with the house system (and supported through that A/B switch).

View attachment 179410

FWIW, this is how it looks "in use" - all covered up.
View attachment 179411
Awesome! And What I wanted to know! Thanks for your help!
 

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hi!
To start and for the next few years my power needs for my van conversion will be webasto heater and max air fan. Down the road I would love to run a hot water heater and an electric stove top.

As I gather funds Is it possible to run a max air fan and Webasto heater using the factory installed dual alternator and dual batteries?

Any reason why a separate system might be better over dual alternator and batteries thinking of long term investment and power needs??
So for my build, I have my house lights (9 LEDs total, 6 ceiling, 3 undermount) and my MaxxAir fan wired to the dual starter batteries, I have my Espar heater, Dometic CFX 75 fridge and 120v appliances wired to my Bluetti AC200max, the Bluetti AC200 Max is nice because you can expand it, i have a 400watt Solaria panel and the Bluetti DC charger enhancer plugged into the cigarette lighter near the rear door and my Bluetti hardly ever drops below 60%, however the downside of the Bluetti is that youre maxed out at 30amps when wiring a fusebox to the RV plugin,
the lights and maxxair have been connected to the starter battery for nearly 2 years with no issues, i personally would not run the webasto through the dual starter batteries, they use quite a bit more power than the fan and lights, but thats just me

i think youre definitely going to want a house battery system, Bluetti is super simple and plug and play, but just have a good idea of all your future power needs before you commit

hope this helps, good luck
 

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Discussion Starter · #8 ·
So for my build, I have my house lights (9 LEDs total, 6 ceiling, 3 undermount) and my MaxxAir fan wired to the dual starter batteries, I have my Espar heater, Dometic CFX 75 fridge and 120v appliances wired to my Bluetti AC200max, the Bluetti AC200 Max is nice because you can expand it, i have a 400watt Solaria panel and the Bluetti DC charger enhancer plugged into the cigarette lighter near the rear door and my Bluetti hardly ever drops below 60%, however the downside of the Bluetti is that youre maxed out at 30amps when wiring a fusebox to the RV plugin,
the lights and maxxair have been connected to the starter battery for nearly 2 years with no issues, i personally would not run the webasto through the dual starter batteries, they use quite a bit more power than the fan and lights, but thats just me

i think youre definitely going to want a house battery system, Bluetti is super simple and plug and play, but just have a good idea of all your future power needs before you commit

hope this helps, good luck
Super good information and thank you!
 

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hi!
To start and for the next few years my power needs for my van conversion will be webasto heater and max air fan. Down the road I would love to run a hot water heater and an electric stove top.

As I gather funds Is it possible to run a max air fan and Webasto heater using the factory installed dual alternator and dual batteries?

Any reason why a separate system might be better over dual alternator and batteries thinking of long term investment and power needs??
Yes, it certainly is possible to run off the OEM dual batteries. I have been running our van this way for 3 years and 30,000 miles of 3-7day off-grid adventures all over the Western States. See my build thread in the link below.

I recently added a stand-alone EcoFlow River and portable 250W solar because we have added a Starlink system. These both needed to be portable because we often park in the shade and need to locate the Starlink and PV with an unobstructed view of the sky. This experience made me really pleased that I didn't invest in a fixed in-place battery bank and rooftop solar.
 

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as Greg/Brit said. My maxxair is off dual house with a 150amp broker off ccp then distribution block for power and, fan. Water pump. If I don’t drive van my e once a week I’ll get notified that van is In sleep mode. This keeps power from start battery full to work. The beauty of ford smart tech. Lol
 
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