Scott, I am reviewing the entire thread on this. Earlier you had recommended an 80-100A breaker/switch. Her you are suggesting just a 40A breaker. I am going to come right off the battery terminals, about 15" to the back of the pedestal and there mount the breaker and a 30A converter 12-24V. Then from the converter take the cable to the AC200 which is 6 feet or so away. I am thinking of adding a 12-120V inverter in the same location and running a second cable from that to the AC200. That means I would be drawing from the battery the amps for both the inverter and the converter, all of which will hide behind the pedestal. I have a fan to cool the entire area. So is the 40A breaker going to be enough or do I need to up that to an 80A breaker/switch?
And Scott rather than bother you in two different places in this thread…I am looking at installing a Dometic 1000RTX Air con. It draws 18 A in the eco mode, and I can cool down the cabin using the vehicle AC and then just keep it cool in the eco mode so that I don’t end up way over the AMP max load. But I am fascinated about putting the AC200 outputs of 10A and 25A together. That would keep me safer for variation. Do you think that will work? It means changing the present 12V circuits I have to the lower AMP outputs, but that is not hard in my set up. I also want to consider getting the add-on battery for the AC200 but that would just give more backup rather than Amps. But I am not sure how the two units connect if I am using the dual charge idea that this thread is supporting.
Connecting those two 12V output ports in parallel is a reasonable idea to consider. However, no one in these forums can reliably predict what will happen.
Since batteries are routinely connected in parallel, one might assume that this idea must also work, but that is not true. The difference is that these DC ports are “regulated” sources—meaning that they have circuitry that continuously adjusts the current flowing in order to try to maintain exactly 12 volts at the port connector. When such devices are connected in parallel, there is no guarantee that the current drawn by the load will be split between the ports in any particular ratio (e.g. 10-to-25, or half-and-half). The split that actually occurs depends on the details of the design of the two regulated sources, and even on the resistance in the wiring you use to connect them.
You either have to experiment yourself (and trust that the Bluetti will protect those 12V ports from over-current damage), or you have to find someone else who has done this experiment (and trust that your results will be similar). Analysis cannot tell you with confidence what will happen.
Karl, The 80-100 amp breaker suggestion you are referring to that I made earlier was in reference to a 12-48 volt converter at a higher amperage draw rate. You are referring to a 12-24 volt converter that will draw no more than 250 watts which is a completely different scenario than the higher draw the thread is about hence the difference circuit breaker amperage recommendations.
I have no idea if you can combine the aviation output 12 volt connector with the 10 amp 12 volt output.
Thanks Scott. I should have read the feed two more times and perhaps I would have picked that up. Advice appreciated. I’ll do pictures and update for the forum when I get this done
Karl Dortzbach
443 570 3668
Hey Landi. Thanks for the detailed warning. Your words make sense. I wish someone would try this. I’m a bit fearful that if the Bluetti doesnt protect them I would have a really big paperweight☹️ I am searching for a way to get AC out of the Bluetti even if not in a boost mode I may just try the 25v output and see what happens. But it still means having to purchase the 1000RTX in the hope it will work. The tech support is suggesting it will. I can’t figure anything else to do but try
Karl Dortzbach
443 570 3668
Thanks all to those who have put into this forum so much help. I have just finished the Transit 12-24V 30A converter taken off of the CCP. It immediately put out 200w and then stopped…I think because the Bluetti was full. I have the fan hooked up now. Question now Scott and all…I want to put an inverter between the converter and the fan to power the Bluetti brick. Do I need more than a 1000w inverter, pure sine wave?
the assembly sits nicely between the pedestal and the shower wall. I will have a deck over it to channel the air. I have pics but cannot figure out how to upload them to this post
you are going to need some very thick cable to run a 1,000 watt inverter and that should be connected directly to your battery, I would size the inverter to be double your expected load.
OK I can change the feed from the CCP to perhaps a #4? I have #8 in now. Would that be enough to run both the converter and the inverter? The CCP has a 60A fuse, and the fuse/shut off now that is in front of the converter is 50A
Karl,
The two tasks of choosing an appropriate wiring size for a circuit, and choosing the appropriate amperage range for the fuse/breaker to protect that wiring are best done using the clear procedures and calculators available on the web. This skill is well within your abilities, and once you have it you will enjoy the ability to carry our electrical projects without asking for the opinions of other people.
I suggest starting at these two web pages:
In short, the minimum wire size is determined by the voltage drop you are willing to tolerate (e.g. 3%) at the maximum current you expect in the circuit. The minimum fuse/breaker size must be a comfortable margin (e.g. 125%) above that maximum current (to prevent nuisance trips). The maximum fuse/breaker size must be less than the current at which your wiring will exceed its temperature rating (and thus might catch fire)—the ampacity of the wire.
thanks Landlocked. These are great reference tools. They don’t handle every question, but they are essential for me.
Landlocked and Scott, The wire guide is very straightforward. But the part I am unsure about is the actual maximum draw if I use both the inverter-PV input and the converter-AC brick input on the same circuit. It seems that the brick draws 400 W at max (33A) and the converter 12-24 can only draw the maximum that the Bluetti accepts or 12A. So it would seem that the maximum draw on the circuit would be 45A. The CCP feed I am using is fused for 60A so if I am correct on the maximum draw, then I should be fine. Am I understanding this correctly? But the converter input is only reading 200 W on the AC200 screen. That makes 8.3A draw. Perhaps it goes up when under acceleration? But it draws from the battery not the Alternator so???
You’re right. Estimating the maximum current drawn from the vehicle (CCP) for this complex setup is not trivial.
For this situation, start by calculating the maximum power the two Bluetti charging inputs will accept. One input’s max power is the rated output power of the brick. The MPPT’s max power is the max current it accepts (12A) multiplied by the input voltage it sees (24V in your design).
Once you know the max power into the Bluetti, you have to start estimating (guessing) the additional power that is lost (by making heat) due to inefficiency in the three power conversion devices in your design:
- 12V-to-24V converter
- 120V AC charging brick
- 12V-to-120V AC inverter
This is not trivial because you’ll probably find that none of those manufacturers publish efficiency figures. I do not have enough experience to suggest typical efficiency values, but others in these forums probably do, especially folks like Scott who has measured power flows in a similar installation.
Once you have a calculation of the total power drawn from the vehicle, you can calculate the max current drawn from the vehicle by assuming a worst case (minimum) vehicle voltage you will encounter, e.g. when the alternator is off and the vehicle battery voltage drops to 12V (?).
If your vehicle power source (CCP) is switched so that power is drawn only when the engine is running, then the worst case vehicle battery voltage is probably much higher (13 or 14V?).
Here is an example calculation (not counting the fan), using hypothetical numbers.
P1 (power delivered by AC brick) = 400W
Eb (efficiency of AC brick) = 80%
Ei (efficiency of inverter) = 70%
vehicle power flowing into inverter = P1/Eb/Ei = 400W / 0.80 / 0.70 ~= 710W
P2 (power delivered to MPPT) = 12A * 24V ~= 290W
Ec (efficiency of 12-to-24V converter) = 75%
vehicle power flowing into converter = P2/Ec = 290W / 0.75 ~= 390W
Total vehicle power supplied ~= 1100 W
V_battery_min (worst case vehicle voltage) = 12.0V (?)
Worse case vehicle current = Total vehicle power supplied / V_battery_min = 1100W/12.0V = 92 amps
Thanks Landlocked. That helps explain why the AC200 was only showing an input of 200W out of the 12-24 converter that feeds the PV. Even the hypothetical numbers would make it seem unlikely that I can feed that AND the inverter-brick from the same 60A switched circuit. It looks like I need to come from the upfiter switches to the inverter-brick OR somehow add a second CCP that the transit forum describes This is formula stuff which shows the impact of efficiency loss. It helps a lot.
Just for fun, I’ll mention that those simple energy balance calculations do not account for power dissipated in all the wiring (as heat). Of course, the general goal is to choose wire sizes large enough to avoid significant power dissipation (heat). Hopefully Ford chose well. I wish the Bluetti cables I’ve seen were just a wee bit larger (cooler).
And I have just seen a feed on a transit site that allows me to add a second CCP 60A point to the pedestal. That will ease my pain since I already know the way into the pedestal, as hard as it is to work there. But it will give a second 60A location. I have also seen a feed that puts two (actually three) 60A CCPs in parallel to feed a single circuit. Just two
would be enough to cover my configuration and because the distance is so small it helps on the wiring size. But is there more loss or something else I don’t know about by simply putting those two CCP feeds together? Of course I would need a 100A switch/breaker. You had mentioned the loss in the potential heat from undersized wires. And even though I am not too savvy on electric, I did wonder why the Bluetti cables are so light weight. As Scot has said, it is in the distance…something that the chart indicates. But the chart starts at 0-6 ft, and the chart by extrapolation would seem to indicate that even an 8ga wire would hold easily a 50A load if the wire is only a foot long.
This is both an easy question and a difficult question.
It’s easy to comment on the functionality of two identical fuses (fed from the same battery) in parallel. That will operate as you expect. Each fuse will carry roughly half of the load current.
It’s probably irresponsible for me to comment on the safety of your proposed configuration under all possible fault conditions, since I do not fully understand the existing electrical system and the additions you propose. I can suggest three general concerns to keep in mind.
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Try to determine if the “line” side of the two CCP fuses are directly tied together, for example by two wires that lead to one larger fuse or lead directly to the battery. If instead your two CCP fuses are fed from two different upstream fuses/breakers, then you have a potential “backfeed” situation when one of those upstream fuses is blown or is removed for maintenance. Backfeed (in low voltage systems) is not necessary dangerous, but can be quite confusing.
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Attach a permanent label on both CCPs stating that their load side is a 120 amp circuit, not the 60A implied by the fuse. Some future owner may not understand what you’ve done, and may wire some accessory to one of the CCPs using wire with only 60A ampacity, which would be a fire hazard.
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Be sure all your load-side wiring either has 120A ampacity or is protected by an appropriate branch fuse. For example, the wire feeding your fan needs its own fuse sized for that small wire.
thanks. These warnings are helpful. I could easily have rushed past them. The first should be answerable by a good schematic, which I assume I can get out of a ford transit forum. I might find the answer by looking but also recognize that just looking isn’t always the answer in a case of disappearing wires in a vehicle. An added precaution that seems wise is to be sure that the CCP and the receiving terminal on the converter is well insulated. I weld with 120A (I know that is 120V also). I think I will tear into this next week after I get some additional parts
I have just finished a week trip from Baltimore to Maine and back. The 12-24 converter was fine, but not enough to power up the Bluetti with solar under trees and in cloudy skies unless i just let the engine run for hours…which I did.
I am rethinking. Cannot I just use two of the charge bricks and take them off of one inverter (a 1500W or a 2000W?) The inverter can connect direct to the battery, and have a fuse/switch.
My concern is what happens to the generator and vehicle battery? is this much of a draw going to create damage? What is the solution? Using two bricks would give me over 1100w input