Feedback Please

[chicagoandy]

Hello, I'd love to get some opinions on the following electrical system for my Ford Transit, High Roof Extended Wheelbase.

Key usage pattern will be "Family adventure wagon", with a Sleep4/Seat4 configuration. Long road trips primarily in the SouthEast and SouthWest, but also Canada and the far-north.

Key electric Loads:
1. Air Conditioning. 24v UndermountAC Minisplit. 16,000BTU. Pulls 1,100 Watts on high.
2. Water Heater. 120V Bosch 4 Gallon Hot Water tank. 1440 watts @ 120V
3. Fridge - Isotherm Cruise 195. 4 amps @ 24V.
4. Microwave Oven: GE Combo Convection/Broiler/Microwave: 1050 watts @120V
5. Induction Cooktop: TBD. Two burners @ 1800 watts.
6. Radiant Heat Flooring: 24V Heating Film 50cm wide 130W/m² 3m = 195 watts
7. Starlink 24V ~70-80 watts
Other standard loads including lights & chargers.

Batteries
4X 12v 280AH, 13,440 Watt Hours
2S2P, 24V
SOK Heated: https://www.us.sokbattery.com/product-page/12v-280ah-lithium-battery-built-in-heater-and-bluetooth

1 Victron Battery Balancer

Solar:
4X Rich Solar 250 watt panels
2P2S
1,000 watts.

Charge Controller: Victron SmartSolar 50/100

Charger/Inverter: Multiplus II 3Kva 24V

Shorepower: Standard 30Amp connection

Alternator Charging:
Dual Ford Alternators
Dual Ford Batteries
Sterling "Saturn" 12V to 24V 120A Input | 60A output
Connected via CCP (170amp Max)

12V|24V to 24V 120A input | 60A output Battery to Battery Charger w/ reverse charging feature

12V|24V to 24V DC to DC Chargers 120A input and 60A output model - E-Marking | BB1224120 Auto detects either 12V or 24V input. Remote control BBR - Optional remote - Buck Boost design, offering high efficiency (95-98%)- Simple installation and setup- Current limiting 4 stage battery charger-...

sterling-power.com

12V Stepdown:
Victron Orion 24V to 12V converter.

CerboGX, a rasberri Pi for HomeAssistant.

I expect most charging will be done via Alternator and Solar, with infrequent opportunities for shorepower.

Does any of this feel grossely mismatched?

 

[green mountain boys]

I am no expert but, if you plan to spend much time charging via alternator you need to be careful not to overload the alternator. Alternators at engine idle speed do not put out many amps. If the alternator is rated for 100amps that is probably measured at something like 3000 rpm. At a 700rpm idle you will get much less output. Just something to keep in mind that many people do not know or overlook. It caught my eye because it looks like you have significant loads and maybe you are going to rely heavily on charging by the alternator.

 

[chicagoandy]

I am no expert but, if you plan to spend much time charging via alternator you need to be careful bot to overload the alternator. Alternators at engine idle speed do not put out many amps. If the alternator is rated for 100amps that is probably measured at something like 3000 rpm. At a 700rpm idle you will get much less output. Just something to keep in mind that many people do not know or overlook. It caught my eye because it looks like you have significant loads and maybe you are going to rely heavily on charging by the alternator.

Yes, great point. The Ford Transit alternators are 250 amps, and the second alternator is tuned for low RPM. I think we should be good on that point.

 

[green mountain boys]

Yes, great point. The Ford Transit alternators are 250 amps, and the second alternator is tuned for low RPM. I think we should be good on that point.

That is good. I would suggest doing some testing to see how the alternator performs. Check the output and the temperature under various loads and ambient temperatures.

 

[Dave in AZ]

Yes, great point. The Ford Transit alternators are 250 amps, and the second alternator is tuned for low RPM. I think we should be good on that point.

Nice, dual high output alternators, sweeet! No problems.

Your fridge must be a typo, 195A...

Rest all looks decent, of course you cant cook and airco at same time without exceeding battery BMS max current probably? All that stuff together adds up, don't feel like looking up battery max draw. But it looks great, what a nice setup.

What the heck..ok, 200A max discharge on the 12v battery. 2s2p for 24v, 2 in series gives 24v 200A, and 2 more in parallel, so 400A possible flow I think, at 24v. Like 9600w lol. I dont think there is any wire for that, but with 2/0 awg you can get 200A, 4/0awg more. If you pull your 24v dc airco load directly from battery busbars, you wouldn't have to load up initial battery cables as much...

Lets see, all your 120vac loads add to 4300w, or 210A pull at 24v to inverter at 85% efficiency. And all your dc, assuming you meant 195w for fridge, is just 66A. So dang, you actually could wire it to flow 280A if needed probably!

That area, battery to busbar to dc load vs inverter load is the area I'd be really looking at, in case you do want to run a lot of those loads at once. Looks like your batteries can support, so the cables will be limiting factor? But 24v sure helps there too! Yeah, very nice!

 

[Rocketman]

Good list…

Here is a few things you may (or may not) want to consider/add…

1. The Victron smart BP65 (battery protect). Used so the 24v stuff cannot drain the battery below ____v (user setable). This way the batteries never go into critical low voltage and go to sleep. Some batteries are difficult to wake up.

2. Bus bar for 24v - if it fits… look at the Victron PowerIn and add fuses (see YouTube).

That’s all I can think of…

Also, make a plan showing all the wiring and fuses and post it for review. (Make any fixes and keep that copy in the van for troubleshooting!)

Good Luck

 

[chicagoandy]

Nice, dual high output alternators, sweeet! No problems.

Your fridge must be a typo, 195A...

Rest all looks decent, of course you cant cook and airco at same time without exceeding battery BMS max current probably? All that stuff together adds up, don't feel like looking up battery max draw. But it looks great, what a nice setup.

What the heck..ok, 200A max discharge on the 12v battery. 2s2p for 24v, 2 in series gives 24v 200A, and 2 more in parallel, so 400A possible flow I think, at 24v. Like 9600w lol. I dont think there is any wire for that, but with 2/0 awg you can get 200A, 4/0awg more. If you pull your 24v dc airco load directly from battery busbars, you wouldn't have to load up initial battery cables as much...

Lets see, all your 120vac loads add to 4300w, or 210A pull at 24v to inverter at 85% efficiency. And all your dc, assuming you meant 195w for fridge, is just 66A. So dang, you actually could wire it to flow 280A if needed probably!

That area, battery to busbar to dc load vs inverter load is the area I'd be really looking at, in case you do want to run a lot of those loads at once. Looks like your batteries can support, so the cables will be limiting factor? But 24v sure helps there too! Yeah, very nice!

195 is the fridge model number. It pulls 4A at 24V. Not a concern for max current, but a concern for total energy over time.

I neglected to mention I'd use a Lynx Distributor for the busbar, and planned on landing the AC on that. So I'd need big cables from Battery to Lynx...

 

[MisterSandals]

Key electric Loads:
1. Air Conditioning. 24v UndermountAC Minisplit. 16,000BTU. Pulls 1,100 Watts on high.
2. Water Heater. 120V Bosch 4 Gallon Hot Water tank. 1440 watts @ 120V
3. Fridge - Isotherm Cruise 195. 4 amps @ 24V.
4. Microwave Oven: GE Combo Convection/Broiler/Microwave: 1050 watts @120V
5. Induction Cooktop: TBD. Two burners @ 1800 watts.
6. Radiant Heat Flooring: 24V Heating Film 50cm wide 130W/m² 3m = 195 watts
7. Starlink 24V ~70-80 watts
Other standard loads including lights & chargers.

You need to add daily usage numbers (hours) on these to get a daily Wh number.

This will allow you to size your solar in conjunction with alternator. Probably not a consistent number?

Finally get a Wh number for your needs from battery when not charging. And number of days you want to store power for if cloudy and alternator not being used.

A max AC draw will help you size an inverter.

All your wiring and fuses will be based on solutions to the questions above.

 

[chicagoandy]

You need to add daily usage numbers (hours) on these to get a daily Wh number.

This will allow you to size your solar in conjunction with alternator. Probably not a consistent number?

Finally get a Wh number for your needs from battery when not charging. And number of days you want to store power for if cloudy and alternator not being used.

A max AC draw will help you size an inverter.

All your wiring and fuses will be based on solutions to the questions above.

A Daily usage numbers is not practical. I have zero knowledge on the load of a water heater, for example. I also have zero knowledge which setting (low, medium, high) for the Air Conditioner I'll be using, or what a typical runtime will look like in the southeast.

The reality is that :

1. 1,000 on a roof of a Ford Transit takes up all the available real-estate with the typical roof-racks. Short of a complex system of actuators (which can always come later), I do not have options to expand the solar.

2. 13.k kWh is a lot of battery for a Transit. It is grossly excessive for everything that's not an Air Conditioner... and and also insufficient to run the Air-Conditioner as much as you'd like in the American Southwest.. I live in the SouthEast. Again I have no basis for actual runtime estimates. I'm not sure that I want to expand the battery beyond 13.5kWh, unless someone can recommend some highly space-efficient options. (cost efficient would a be a plus too....)

3. B2B charging is one area where I do have options. I've landed on the Sterling 12V 120amp unit that outputs 24v@60 Amp. The Ford transit limits the (CCP2) Customer Connection Point to 170 amps. There is a Ford fuse at 170 amps that you REALLY don't want to blow, but there is also some people who have bypassed this fuse and pulled directly off the battery. Conceptually, I could add a second B2B charger to bring the total load up to 170 amps. However, sterling doesn't make a smaller 24V charger. Victron's new Orion doesn't is only 12v. So that's not going to work. Possibly I could add a Renogy 50 amp DC2DC charger to get 170 amps, but I'm not sure how I avoid blowing the Ford 170 amp fuse.

That leaves "DC-AC-DC", or just running a large 2,200 watt inverter off the alternator and feeding the Multiplus. I'd need a transfer switch for when I want to plug into shorepower. I can use the Multiplus current-limiting features to stay under the Ford 170 amp fuse.

My gut tells me that where I am, with 1,400 watts coming off the Sterling while driving plus another 1,000 watts when it's sunny, I've got enough options to make it work, and I stay comfortably away from the Ford limits. I'd love to hear if anyone thinks I'm off track here.

In terms of Max 120vAC draw, my gut feel is that I'm fine. Again, I don't think there's actually any options for going larger on the inverter. At least not in the Victron ecosystem, or without adding a second one which the Transit doesn't have space for. 3KVA is the largest Multiplus that runs at 24V/120V. I would need to switch to 48V, which would be a big-change. That leaves me with 3,000 VA and the ability to surge up to 5,000 VA. That means I can run both the cooktop and microwave at the same time, and if the water heater kicks in I'll be into the surge capacity. Given that the cooktop typically won't typically be running at full power, that's probably ok. Let me know if you're aware of a better charger/inverter I should be looking at?

For wire size I intend to follow the mfg's instructions, which for the Multiplus is AWG-1 for short runs and a 300amp fuse. Again, we're in a transit so these will be short. UndermountAC.com recommends AWG-2 and a 200 amp fuse. As long as I stay under 15 feet, these align with the BlueSea charts here: https://d2pyqm2yd3fw2i.cloudfront.net/files/resources/reference/20010.pdf

I do see value in drawing up a proper circuit diagram, and will spend some time on that.

I really do value some feedback here, so please let me know if you think I'm off-track.

 

[Reed Cole]

A Daily usage numbers is not practical. I have zero knowledge on the load of a water heater, for example. I also have zero knowledge which setting (low, medium, high) for the Air Conditioner I'll be using, or what a typical runtime will look like in the southeast.

The reality is that :

1. 1,000 on a roof of a Ford Transit takes up all the available real-estate with the typical roof-racks. Short of a complex system of actuators (which can always come later), I do not have options to expand the solar.

2. 13.k kWh is a lot of battery for a Transit. It is grossly excessive for everything that's not an Air Conditioner... and and also insufficient to run the Air-Conditioner as much as you'd like in the American Southwest.. I live in the SouthEast. Again I have no basis for actual runtime estimates. I'm not sure that I want to expand the battery beyond 13.5kWh, unless someone can recommend some highly space-efficient options. (cost efficient would a be a plus too....)

3. B2B charging is one area where I do have options. I've landed on the Sterling 12V 120amp unit that outputs 24v@60 Amp. The Ford transit limits the (CCP2) Customer Connection Point to 170 amps. There is a Ford fuse at 170 amps that you REALLY don't want to blow, but there is also some people who have bypassed this fuse and pulled directly off the battery. Conceptually, I could add a second B2B charger to bring the total load up to 170 amps. However, sterling doesn't make a smaller 24V charger. Victron's new Orion doesn't is only 12v. So that's not going to work. Possibly I could add a Renogy 50 amp DC2DC charger to get 170 amps, but I'm not sure how I avoid blowing the Ford 170 amp fuse.

That leaves "DC-AC-DC", or just running a large 2,200 watt inverter off the alternator and feeding the Multiplus. I'd need a transfer switch for when I want to plug into shorepower. I can use the Multiplus current-limiting features to stay under the Ford 170 amp fuse.

My gut tells me that where I am, with 1,400 watts coming off the Sterling while driving plus another 1,000 watts when it's sunny, I've got enough options to make it work, and I stay comfortably away from the Ford limits. I'd love to hear if anyone thinks I'm off track here.

In terms of Max 120vAC draw, my gut feel is that I'm fine. Again, I don't think there's actually any options for going larger on the inverter. At least not in the Victron ecosystem, or without adding a second one which the Transit doesn't have space for. 3KVA is the largest Multiplus that runs at 24V/120V. I would need to switch to 48V, which would be a big-change. That leaves me with 3,000 VA and the ability to surge up to 5,000 VA. That means I can run both the cooktop and microwave at the same time, and if the water heater kicks in I'll be into the surge capacity. Given that the cooktop typically won't typically be running at full power, that's probably ok. Let me know if you're aware of a better charger/inverter I should be looking at?

For wire size I intend to follow the mfg's instructions, which for the Multiplus is AWG-1 for short runs and a 300amp fuse. Again, we're in a transit so these will be short. UndermountAC.com recommends AWG-2 and a 200 amp fuse. As long as I stay under 15 feet, these align with the BlueSea charts here: https://d2pyqm2yd3fw2i.cloudfront.net/files/resources/reference/20010.pdf

I do see value in drawing up a proper circuit diagram, and will spend some time on that.

I really do value some feedback here, so please let me know if you think I'm off-track.

I don't think you're off track. Though relying on your gut feeling for things that can be quantified without much difficulty is a bit odd. While I appreciate that you are dealing with physical constraints of the van it would be unfortunate to sink a bunch money into this and then it doesn't end up being practical.

Victron does offer 12-24v chargers and converters, not sure what the issue is with them not being as new as their 12v options.

Using a separate inverter to power the multi-plus seems like it would be a bit of a hassle to operate or to setup so it you could turn it off and on with a relay if that's even possible. I suppose an ordinary voltage sensing relay between the starter battery and the inverter would at least make it so you don't have to worry about draining the starter battery if you forget to turn it off after driving.

One thing to keep in mind about flat mounted panels is that you'll almost never achieve full output, probably closer to 700w in good conditions, which requires you to be in the sun which will make your van hotter. Deploying some portable panels is worth consideration, maybe even a generator.

 

[chicagoandy]

Coming back to this thread, I have created some wiring designs.

As a reminder, this is going ontop of a Ford Transit. Dual AGM Batteries, Dual 250A Alternators. The 1,000 watts of solar I have is the most that can fit uptop.

Batteries are currently spec'd as 4X 12V 300AH from Epoch.

Feedback please?

 

[HarryN]

Just a quick scan - not full analysis.

The 2 awg from the CCP2 to the sterling is a little light for 120 amps.

The wire needs to be rated to meet both the voltage loss numbers from the calculator, and the ampacity chart.

Here is an example ampacity chart:

Cerrowire Resources - Ampacity Charts

Ampacity is the maximum current that a conductor can carry continuously under the conditions of use without exceeding its temperature rating. Cerrowire's ampacity chart helps calculate the load requirement for a circuit.

www.cerrowire.com

Based on the chart, it might be better to look at 2/0 ( 00 ) instead of 2 awg.

______________

The USB outlets will operate better if run from the 24 volt instead of the 12 volt, especially the higher performance ones.

With a 24 volt system, your goal should ideally be to run as much as possible from that voltage or 120 vac, and not 12 volt unless there is just no possible alternative. In a van, about the only thing that I can think of is the exhaust roof fan.

Conventional 12 volt outlets are really rated for 8 - 10 amp use, so don't get carried away with what they can really do.

See if you can find a 24 volt version of the heater if possible.

______________

Make sure to use an "official Ford approved ground point" and not just a random thing that others use for ground points in the Transit.

_________________

I have no experience with that battery brand but in general I am a big fan of using cylindrical cell based batteries in mobile applications. (example battle borns ) but you should be able to search on this forum and on line to look for results in mobile applications.




Good luck.

 

[HarryN]

As far as the inverter sizing, the 3000 / 24 will power one each, fairly healthy load at a time.

It is 2400 watts from a end device perspective, so similar to a 20 amp outlet in a home.

It is easy to test your appliances on a home 20 amp outlet, usually there is one under the sink for the disposal.

_________________

There is a 5000 / 24 quatro ( nominal 4000 watts ) if you really want to run multiple appliances. It is a real beast to lift but it will absolutely power some stuff.

 

[chicagoandy]

Thank you Harry. In their wisdom, Sterling put 8.9mm ports on their largest B2B chargers, so we're effectively limited to AWG-2. I will be keeping that run short, mounting the unit between the B and C pillar.

In terms of consumption, most of the kitchen loads will run at less than full-power most of the time, and high-power draws should be short. I also understand the 3kVA unit can surge to 3,000 watts for up to 30 minutes. (less when hot). I think that should be enough to get breakfast made...?

Or is your comment here based on the 20a vs 15a circuits? That decision was a quick choice to overbuild, as chasing circuit popping gremlins is just not fun.

 

[HarryN]

When a person builds a "product for sale", they do the research, build a prototype, and then test it for a while.

There are nearly always things that come up that are not expected, either because a data sheet had a little too much marketing in it, mis interpretation, or an integration interaction that was not expected. This happens if you purchase everything from one company or multiple companies.

When the design is based on running everything at ~ 50% of the max ratings, usually there aren't too many things that come up, but still some.

When you build something that is designed around running items at near their official ratings, then the margins are tighter, especially for hot or cold weather use.

So in a product, there tends to be at least a few rounds of prototypes and then a final product where everyone pretty much knows how it will all behave - until the customer gets it and then they start doing things that no one expected.

What you are doing it going through the data sheets, trying to make sure that your system components are not being run anywhere near their max conditions. Getting input and then building a one - off prototype based on the best info / guess that you can find.

There is only so much room in a van, so trade offs need to be made. That is life.

Will it be perfect and operate exactly how you imagine it - no, but it can be debugged and you are in the right general range of operation.

Will your wife and children find bugs and have comments on how it can be better - absolutely.

Welcome to building van electrical systems.

 

[justinm001]

You won't be able to use the microwave and both burners at the same time or even 1 burner on high, but could use 1 on low and 1 on med with the microwave. Just something you need to work around when cooking.

Starlink uses less power unless it's heating. I think more like 30w.

You should rethink your heat, 200w of electric heat at 100% efficiency is only 663btu. A person gives off 250btu. 200w is about a much heat a heated blanket uses. Something like a 5000btu diesel heater would be great.

Consider swapping the 30a cord with a 50a and just using 1 leg of it. With Victron not a big deal because you can power assist. But you'll be able to increase from 3600w to 6000w (80% of these). It'll let you charge batteries quickly and do everything you want comfortably when on shore.

 

[Q-Dog]

If this were a lightly loaded system I MIGHT be OK with 12 volt battteries, but with a heavily loaded system it is ineviteable the batteries will become unbablanced with each other in a 24 volt system. I would definitely use 24 volt batteries in this particular 24 volt system.

 

[chicagoandy]

If this were a lightly loaded system I MIGHT be OK with 12 volt battteries, but with a heavily loaded system it is ineviteable the batteries will become unbablanced with each other in a 24 volt system. I would definitely use 24 volt batteries in this particular 24 volt system.

I have the Victron battery balancer to keep them balanced. Is that not sufficient?

 

[chicagoandy]

You won't be able to use the microwave and both burners at the same time or even 1 burner on high, but could use 1 on low and 1 on med with the microwave. Just something you need to work around when cooking.

Starlink uses less power unless it's heating. I think more like 30w.

You should rethink your heat, 200w of electric heat at 100% efficiency is only 663btu. A person gives off 250btu. 200w is about a much heat a heated blanket uses. Something like a 5000btu diesel heater would be great.

Consider swapping the 30a cord with a 50a and just using 1 leg of it. With Victron not a big deal because you can power assist. But you'll be able to increase from 3600w to 6000w (80% of these). It'll let you charge batteries quickly and do everything you want comfortably when on shore.

Thanks! Yes, I have a gasoline "diesel heater" in the plan. I didn't list it here as it's not a material electrical load. Interesting thought on the shorepower, I actually don't think I'll get many chances to use even 30a, as we'll probably be totally off-grid more often than at a traditional RV campsite. Thanks for the review!

 

[Q-Dog]

I have the Victron battery balancer to keep them balanced. Is that not sufficient?

Just another complication. Don't need it with batteries at their native system voltage.