Dual charging PV and 110V

Product Discussion BLUETTI AC Series
185

Hi Karl,
You should indeed run the energy balance calculations we discussed, to estimate the worst-case current drawn from the vehicle battery/alternator.

Someone in these forums has probably measured the AC power flowing into a AC200 charging brick. That (x2) tells you the inverter output power. The inverter manufactuer should tell you the (best-case) efficiency; reduce that by a bit for margin. Then DC power flowing into the inverter equals AC power flowing out divided by efficiency.

The second step is to estimate the worst-case (lowest) voltage at the vehicle battery terminals, while the engine alternator is running. I am not qualified to suggest a value. I think that when the vehicle battery is nearly full the alternator voltage is ~~14V. When the vehicle battery is hard-charging the voltage at the terminals is lower—perhaps 12V or less. (Others can give you more specific numbers.)

The third step is to estimate the voltage drop from the vehicle battery terminal to the DC input to the inverter. That can be made very small if you use large cable and have short runs.

Once you know the worst-case (lowest) DC voltage at the inverter input terminals, then you can calculate the worst-case (largest) DC current flowing into the inverter for the inverter input power calculated earlier.

Finally, we get to the hard part. Let’s say that you calculate the worst-case DC input current drawn by the inverter is 120 amps. The vehicle alternator will do its best to supply those 120 amps AND supply the worst-case loads of the vehicle’s electrical equipment.

The hard part is guessing whether the alternator in your vehicle will survive that situation. I use the work “guessing” very deliberately. I think you’ll find that there is no document that states the worst-case power drawn by the vehicle. And there is no document that states the maximum continuous current the alternator can produce under worst-case thermal conditions (slow driving on hot summer day). Without those specifications, adding electrical accessories to a vehicle is always a calculated risk to the alternator.

186

Again thanks Landlocked. I think I have just enough skill and knowito be dangerous :worried:. I’m going to have to think through your answer and find some one to walk me through it. Some of the “hard” parts of your answer seem like a logical warning. It makes simple sense to not try using the two charge blocks while idling the engine and using the AC in the summer. But of course that is going to be a likely scenario… a hot muggy day stuck in traffic following a night where the Bluetti has been drained.

Further it is hard to find someone with the measurements for things like charger inputs and particularly the limitations of the generator. I don’t know where to start getting that data. I am hoping that someone on this forum knows the answer to the charger brick input. There seems to be the suggestion that the Bluetti will Draw as much power as possible up to its own limits. I do appreciate that it is unlikely to know the limits of a alternator…but it must be available somewhere or Ford wouldn’t make a heavier duty alternator I might have to fish on a forum there

Karl Dortzbach
443 570 3668

187

I want to pick up with a 9-month update, I ended up getting a pure sine 2000W inverter and connected it just behind the driver pedestal/battery. I connected it to one of the many terminals available in the connection box rather than use the CPP which was much too light duty. I connected with 4AWG cable, and I was able to charge my AC200P using two bricks. for a 8000 mile trip, BUT the charge system continuously tripped the breaker switch I used (150A). The wires were a little warm but never hot. It was not satisfactory. I have just changed the wire to 2AWG and a 250A breaker switch, Doing so immediately produced about 800A of charge input and took the SoGen from 85% to 100% in about 15 minutes with the engine at idle, I think Landlocked is correct that I will be taxing the generator, but I am not doing a continuous charge, The Ford dealer top mechanic felt that I could safely run the standard alternator and power a 2000W inverter without excessively taxing the alternator (I let him know I would be powering the two charge bricks). He also said that the alternator doesn’t tend to just go out at once, it usually gives some advance notice–that is a little reassuring but if I am on the road again for 8,000 miles, then I don’t want to be on the other side of the continent when I start getting warnings. But it seems a reasonable risk.

My great expectations that multiple solar panels would do the recharging has turned to be very illusory, Rarely am I in full sun when I am camped, ON the road I can use my inverter to power one brick and the roof-top solar to do the PV charge. But clouds and trees REALLY impact the useful charge of solar

1 Like
188

Older thread and its my first post and im not skilled in this forum and can’t figure out how to PM the primary people in this thread yet so Ill try here as others might have similar questions:

I recently purchased an ac200 max because of this thread, with the intention of doing exactly what is listed in this thread to charge my bluetti with one of these $200 step up 12 to 48v 20A convertors. Ive got the convertor currently in the mail and arriving soon. I will have a super short run (like 3 feet ) from batteries to convertor so going with 4G wire, and then maybe a 10 foot run from convertor to my bluetti so going with 10G wire. I plan on using a 150A blue sea breaker for on/ off capabilities. I have a few lingering questions.

  1. does it matter if I put the 150A breaker before or after the convertor? I assume I can put it after the convertor and before the bluetti, just wanted to make sure.

  2. I have not played around with the bluetti much- but how do I connect my 10g wire from the convertor to what everyone on here seems to call the aviation plug?

  3. has anybody found any of the larger companies that make a step up 12- 48v convertor besides besides sterling (victron, ect?). I could not find any, wondering if anybody else found something.

  4. any long term reviews from some of the original pioneers in this thread how their cheap convertors are holding up after a year or so of use?

  5. has anybody else done this an not used the fan at all and found if not necessary?

  6. are these convertors loud at all?

This thread has been SUPER helpful to me, and I would like to take the time to thank those of you that were hugely helpful like @Scott-Benson and and @jkennon and others like quitter and landlocked (it only lets me list two people, sorry)

189

@Quitter @LandLocked

190

1-Put the breaker before the converter
2-The aviation cable that comes with your Bluetti also attaches to MC4 solar charging cables. You could simply attach MC4 cables to your 10 G. 48 volt wires from your converter and from that point connect them the same as you would connecting solar panels to the Bluetti.
3-I haven’t found anything better than the cheap ones and the Victron units I found did not step up the voltage as much as I wanted. By cheap, I assume we are talking about the low $100 range.
4-I have several converters and have used them off an on for a couple of years with no issues at this point. But…I am only using them a few times yearly and not in constant use.
5-The fan may not be necessary, but I am sure the components will last longer with a small fan. A low power pancake computer fan works great and can connect directly to the 12 volt input line to your step up converter.
6-The Converters are silent.

191

Thnaks for the reply!

The “cheap” converters have gone up a bit since this thread was started and they are now $200 for the 20A version, but I guess I am still calling them cheap because that is half the price of the sterling.

And using the MC4 connector is great and super simple idea, thanks!

Cheers.

192

Out of curiosity- why would it matter if I had the breaker after the converter, it wouldn’t draw current from the house batteries if it was off, would it?

193

Breakers are meant to be between the power source and the item to be protected. If the object of the breaker is to protect the converter, then it would have to be installed on the incoming positive power lead.

194

Makes sense.

I will report back the results !

195

OK! well, things work, but there is a problem. I bought a 48V step up convertor. Package says 48V, email receipt the same, but wonder if I got a 72V by accident. Seems the same happened to @Scott-Benson when he ordered a 24v and got a 48v ste[ up. Anyways- it charges at 709w, which is pretty insanely awesome, if I wasn’t in fear of burring my van down! My ac200 max was dead yesterday, and I charged it for maybe 10 minutes with my van and it went from 0% to 10% in that time (ford transit, HD alternator).

I did not do the install myself, as I was having a bunch of work done on the van but I instructed the van people what to do. Welllll, they didn’t exactly listen to me as I told them where to put the step up, and what guage cable to use. They put the step up in the back of the van behind a wall panel, and only used maybe 10G wire from starter batteries to step up.

10 min is the max I ran it before general fear took over, but the wall panel did not feel hot and neither did the 10G cable.

So my question- should I be afraid, or just run with it? I really don’t care if the step up burns up and doesn’t work. Ill replace it with a 48v at that point (or maybe a commercial start/ stop option will become available by then). Im only going to use it sparingly anyways. What I dont want is an actual fire! is that a realistic option or would the breakers prevent that? Is 72V getting to the dangerous level of power?

Thanks in advance and sorry for the ignorant questions!

charging
charging750×1334 144 KB

196

Wayne, if 10g wire was used between the vehicle battery and converter, then I am rather concerned about fire safety.

Analyzing the fire safety of this circuit involves several steps. First, the “temperature rating” of the wire used must be known—it’s generally printed on the wire covering.

Second, one must look up how much current that wire can safely carry, as determined by some electrical standard. The ABYC standard, which is used for boats, says that the maximum safe current in 10g wire in cool conditions (i.e. not in a hot machinery space) varies from 40 to 70 amps, depending on the wire’s temperature rating.

Third, one must measure or estimate the current flowing in your wire under worst case conditions.
If you have access to a “clamp current meter” then you can simply measure the current in the wire, under worst case conditions.

Otherwise, calculations of the current can be made. Those calculations can done with varying levels of complexity and accuracy.

Let’s start with a naively simple calculation. The Bluetti reports 709W of charging power. The nominal voltage of the vehicle’s electrical system is “12” volts. Using the formula I (amps) = P (watts) / V (volts) one estimates a current of 709W / 12V = 59 amps. The ABYC standard says that 59A in 10g wire is safe if the wire has a temperature rating of 105C or higher.

But what about the additional power warming up the converter? To calculate that we must know the efficiency of the converter, in the operating conditions of your circuit (as opposed to the advertised “peak efficiency” in optimal conditions). No one in this forum knows that efficiency accurately, but let’s make a wild guess of 79% efficiency. With that assumption, the power being drawn from the vehicle is 709W/0.80 = 900W. Thus the current flowing from battery to converter is 900W/12V = 75 amps. The ABYC standard says that no 10g wire can safely carry 75 amps.

We are still a bit way from an accurate estimation of current. Next up is that “12 V” assumption. With the alternator running, the voltage at the battery may be a bit higher (which is great, as it reduces the current flowing in your 10g wire). But what happens when you shut down the engine? If the design does not shut down the Bluetti charging, then the voltage at the battery can easily drop below 12 V. Let’s guess that it drops to 11V. Then we have 900W/11V = 82 A.

Next up is the fact that your long run from battery to “back of the van” produces significant “voltage drop”, i.e. if there is 12 V at the battery there may be, for example, only 10.5 V across the converter. Then we have 900W/10.5V = 86 A.

None of the above example current values are accurate of course, but I think it’s reasonable to say that 10g wire in your circuit is not obviously safe. I encourage you to confirm the actual gauge used, find its temperature rating, and find a clamp meter to measure the actually current flowing with alternator stopped.

197

In a properly designed circuit, the size of the circuit breaker is based on that maximum safe current for the wire that was used in the circuit (which depends on both gauge and temperature rating). When properly sized, the breaker does indeed provide effective protection against fire. However, if your wiring is in fact carrying current well over its rated maximum, then by definition your circuit breaker is oversized and is providing inadequate fire protection.

198

Wow., so much to unpack there! much appreciate the reply.

I pulled out some of the wall and re-checked the cable from starter battery to step up, and it said #4 windynation, so is not 10guage as I originally thought. breaker is 150a.

I ran the step up for 20 min yesterday just to test it out again. The cable from step up to starter battery was not warm even in the least. The cable from step up to bluetti was slightly warm, and the step up itself was warm but not hot. Also- the run from the starter batter (under driver seat) to back of van is maybe 6ft.

I guess im a little less afraid of a spontaneous fire!

Would others agree if im pulling709W that the step up is a 12v to 72v, not a 12v to 48v like i purchased?

thx!

199

Good! That makes sense. Max safe current of 4g wire is 125 to 180 amps, depending on temperature rating.

200

If it can be done easily, I would recommend mounting the step up converter closer to the batter and then running the stepped up voltage the longer run to the Bluetti. This higher voltage will has less loss over distance and will also require less amperage transmitted through the wiring over the longer distance.

1 Like
201

I purchased the 20 amp 12-48v step up converter, hooked it up to my transit ccp2 terminal with a 70amp circuit breaker, and voila, getting a consistent 700w to the pv/car charger on my AC200max with 1 B230 . Thank you so much for your work on this! Converter gets warm but not hot. CCP2 stays on until van battery management system shuts down the CCP2 terminal (90min or so)