Suggestions for a DC to DC converter (/charger) ? (5 Viewers)

[e9999]

^^ if you ran the meter at 40A for an hour and it is fine, it'll likely do equally well for much longer too, it should take much less than an hour to have it reach max temp.

 

[FrazzledHunter]

^^ if you ran the meter at 40A for an hour and it is fine, it'll likely do equally well for much longer too, it should take much less than an hour to have it reach max temp.

I didn't notice it being hot. It's advertised at 75A.
From their website:
"Amps: 75A continuous, 140A peak, 0.01 A resolution from 1 ~ 140"

I might buy a 2nd one to simultaneously monitor the input and output of these DC-DC chargers.
I've done that, obviously just not at the same time, but I think I have a pretty good idea how the system is working.

REF:
Powerwerx Watt Meter Plus, DC Inline Power Analyzer, 75A Continuous, 8 Gauge, SB50 Powerpole Connectors - https://powerwerx.com/watt-meter-plus-power-analyzer-8-gauge-sb50

 

[ntsqd]

Any of you looked at the power meters sold for use in RC? The "Watt's Up" meter and it's clones. Some of the pop-top camper world are using them for monitoring their camper's power system.

 

[e9999]

^^ a question that comes to mind about this 75A continuous claim is that they use 8ga wires. I would have thought that 75A is too high for most 8ga wires.

 

[veiloctane]

here is my dual battery setup on my HDJ81 im using Ctek d250s and smartpass

i plan on running 2x 175W mppt solar panels

 

[ntsqd]

^^ a question that comes to mind about this 75A continuous claim is that they use 8ga wires. I would have thought that 75A is too high for most 8ga wires.

Wouldn't that be dependent on the length of the wire(s)?

 

[sdnative]

Wouldn't that be dependent on the length of the wire(s)?

Not necessarily. Wire size requirement is dictated by both voltage drop and ampacity limit.

8ga barely meets 75A ampacity limit, but could very well be undesirable for voltage drop for all but the shortest runs.

Here is a handy calculator:

Interactive Wire Size Calculator

Battery Chargers, Inverters, Solar Components, and Wiring Supplies for Boats, RVs, and Off-Grid Applications.

baymarinesupply.com

 

[e9999]

yes, there are really 2 main issues with wire sizing, as stated above: excessive voltage drop (too much length for a given gauge and current) and excessive temperature. Conceivably, the former could possibly result in the latter as well to some extent, but not necessarily, that would depend on the load. The latter on its own, though, is clearly dangerous as it may result in a fire or direct damage to wiring and possibly equipment. Note that the current limit depends on the type of insulation since that is the wiring component most readily affected (melting/burning). Your 8 gauge may be OK to 50A with one type of insulation and to 60A with another. A good source will differentiate between the two. It should even depend on the ambient temperature. Unfortunately, I doubt that your typical chinese supplier will usually splurge on the best plastic insulation. All possibly seen as hair-splitting, admittedly, until your wiring components start melting like happened to me because of stupidity, as described above (I think).

 

[ntsqd]

According to the formula here: Three percent voltage drop - https://www.ancorproducts.com/Resources/Three-percent-voltage-drop 8 ga will carry 75A at 3% or less VD for for a max of 7.5 inches. That may be all that the meter mfg needs. Granted, it probably isn't enough for most uses, but in the intended use of the meter it's more than enough.

 

[e9999]

^ I don't know about the particulars of that specific bit of wire, but it looks like you are not considering the overall point (ampacity) about excessive temperature in your assessment. It is a separate (although related) issue from excess voltage drop. It simply means that the current is such that for that given insulation material, the temperature generated by the current in the wire will not exceed the melting / burning temperature of the insulation. This is primarily a localized effect and it would not matter much whether the wire is 1ft or 10ft long. I may not be explaining this clearly, so for better illustration, bear with me and let me take this to a silly extreme: imagine that the insulation is made of a much more easily flammable material than the usual plastic. Say paper soaked in gasoline (!). It may then take only 10A, say, for the 8ga wire to see its insulation start to burn because it does not take much heating to do so, and the temperature generated by the 10A in the wire is enough for that to happen. Then the ampacity limit for that wire / insulation combo would be 10A, even though it is 8ga and may be very short. Yes, yes, silly and unrealistic, but the same idea, it's not directly a voltage drop issue, it has little to do with how long the wire is (unless there is significant cooling at the ends of that wire). And note that ampacity should really be strictly defined under steady-state conditions. You can certainly exceed the ampacity rating for short periods of time because the temperature may not have risen enough yet to cause a problem, there is thermal inertia.
But, again, as I said, I don't know about that particular meter wires, I'm talking generalities since we are discussing wire sizing, and the 8ga wire may just fine for that particular meter application, I would hope so.
And, while we're at it, a formula about a 3% voltage drop limit is just a broad rule of thumb, in reality 3% may or may not be too much, it depends on the specific equipment requirements. Your load may be perfectly happy with a much lower voltage, so take that with a grain of salt.
Interesting stuff, all that.

 

[ntsqd]

Historically the insulation on RC car wire is silicone, so I'm expecting this to be the same. Granted, the finest chinesium silicone insulation may not be quite as good as domestic silicone insulation.....

That resource, of course, assumes that you're using their wire with a 105°C rated insulation. If a wire's resistance that results in a 3% VD is enough to heat the wire to the point of melting or igniting the insulation then I'd think that something's been overlooked.
SDNative's link above shows this, 80A for a single conductor outside of engine spaces:

Which is far less conservative than the Ancor link.

EDIT: A quick survey of the first three sites with relevant info on the topic showed that silicone insulation should be good to at least 200°C and two of the three said it maxed out (short term use OK) at 250°C.

 

[e9999]

it seems to me that if there is a criterion labeled as something based on a given voltage drop it is much more likely than not to be exactly only that, disregarding other considerations like the insulation temperature limit. This appears to be the case in your 3% online page, where I see no reference at all to the insulation material applicable. So, either the insulation does not matter at all (unlikely) or this is just a separate criterion disregarding that issue altogether (likely).

Anyway, not to belabor the point any longer, on the more practical side, I would simply use both criteria together to size wire. Check the ampacity based on the insulation material and the likely ambient temperatures / containment situation (conduit etc), and also the allowable voltage drop based on your equipment, and use the most conservative answer so there is no problem either way.

Or even more practical still: run the needed current through the meter, hold it in your hand, and if it's not too hot to hold, you're probably good. If something melts, well, it wasn't good enough...

 

[ntsqd]

I suspect that so long as you stay above the 10% VD limit that you don't have enough resistance to heat the wire hot enough for the the insulation's melting or ignition points to be a concern. Note that I'm not talking about the connections and their various maladies, just the wire.

There is probably a formula out there that predicts the wire temperature based on it's size, material, surrounding environ, and the amperage of the circuit.

Within the limits of my knowledge of it I conform to the wiring guidelines of the ABYC in all of my 12 VDC constructions. There's some dry reading..... it's better than counting sheep.

 

[e9999]

It is indeed probably fair to say that for most routine applications and reasonably sized components, you're more likely to end up in trouble with the connectors than with the wire itself.

 

[LandLocked93]

Followed this best I can...disreagrd if not applicable but just for mentioning sake, shunt wiring is tiny as it does not carry the actual current being measured. 16ga is sufficient for any length w/i a vehicle.

 

[e9999]

^ there are many different kinds of shunt circuits including bypass and protection circuits, but normally when you talk about using a "shunt" to measure a current, it means the entire current is going through the shunt resistor so you can measure the corresponding voltage and calculate the current. So, not sure what you mean.

 

[LandLocked93]

^ there are many different kinds of shunt circuits including bypass and protection circuits, but normally when you talk about using a "shunt" to measure a current, it means the entire current is going through the shunt resistor so you can measure the corresponding voltage and calculate the current. So, not sure what you mean.

We're saying the same thing I think.
The shunt itself does carry full load current. I'm speaking of the 2 tap wires used for measuring the voltage off the shunt. They are tiny and carry voltage in the 100mV region (think 150mV equates to max current on mine, 100A) with current if any in the microamp range.

The one piece units do the same thing inside. You just cant separate the display from the rest of the unit, so it seems like all the current passes thru the measuring wires.

edit:and as you know, those taps are directional depending if you're measuring charge or discharge. In my case, I use a 4P/DT switch at the dash panel to flip the direction (some people call it polarity tho it isn't strictly speaking) to measure voltage and current (E & I for the purists) charge or discharge at any given time.

 

[MCtree]

I've run it at 40A for hours and hours cooled with the fan. I've used the charging watt meter on my Goal Zero 1500X mostly. 380W input to the Goal Zero equates to 40A input to the Victron 12-24/15 as measured with my watt meter.

@FrazzledHunter,
Could you share your settings on your Orion? I'm having a heck of a time to get mine running properly.
See here: Another Victron to Ecoflow thread - https://forum.ih8mud.com/threads/another-victron-to-ecoflow-thread.1336967/

Also... I'm curious as to what your shut-down parameters are on the Orion. If I select a shutdown voltage, the Orion turns itself off. But then where there is no load, the input voltage creeps up to where the Orion turns itself back on again,

 

[FrazzledHunter]

@FrazzledHunter,
Could you share your settings on your Orion? I'm having a heck of a time to get mine running properly.
See here: Another Victron to Ecoflow thread - https://forum.ih8mud.com/threads/another-victron-to-ecoflow-thread.1336967/

Also... I'm curious as to what your shut-down parameters are on the Orion. If I select a shutdown voltage, the Orion turns itself off. But then where there is no load, the input voltage creeps up to where the Orion turns itself back on again,

Sure glad to. The quick answer (scenario 1 below) is this:

• Input voltage lock-out:12.5V
• Voltage to resume: 13.2V

TL;DR

However I have 2 scenarios:

1. With the Victron connected to the starter battery what I am trying to do is have the Victron turn off immediately after engine shutoff and resume immediately after engine start. The Victron Values below are for this case.
2. If I’m connecting the Victron the 2nd battery to intentionally drain it then the Victron’s values are different and vary with the battery and the DC charger’s ability to recharge it.
   1. In this case for my AGM battery I set the lock-out to 10.5V and the resume to be 12.0V

I don't know if the values apply to every LC but I think the approach applies universally which is to establish voltage floor, ceiling and nominal values. First thing you need to do is measure what you're LC is doing. It will vary by temperature and how long it's sat without running.

• Temp: 65F
• Floor voltage - the battery voltage after the LC sits a day or two
  • 12.25V
  • This will be lower in winter and the longer it sits
  • I have started the LC at 11.5V; do not know the V at which LC will not start.
• Ceiling cold start voltage
  • 14V
  • This will be higher in winter
  • I have observed it as high as 14.5V; do not know if it ever gets higher.
• Nominal warmed up voltage
  • This is the value to which you need to pay careful attention
  • 13.6V
  • I have observed this NOT to change much with temperature

My current Victron settings at cold start:

• Mode: Power Supply
• Input Voltage: 14.0V
• Output Voltage: 24.0V
  • This was no load; it will drop significantly under full load to approx. 19V but will maintain power in watts to approx.. 380W
• Input voltage lock-out:12.5V
• Voltage to resume: 13.2V