diy solar

diy solar

LiFePO4 heating pad for cold temperatures

Yes and the mV meter is calibrated in amps. Basic analog ammeter. No clue on how to get a digital circuit to log the information.
Correct.

But if you plug a different meter into it that correlates temperature with millivolts then you'll get a temperature reading from it, only the thing you're measuring won't be temperature.

But we don't care as long as it shows up on screen.
 
the shunt resistor has two voltages to measure drop
measuring a third voltage of the pack positive allows calculating power
 
No. The shunt does not "measure" voltage. It produces a voltage difference that a meter can read.

The shunt does not output current.
Ok, so you are getting aggressive.

A shunt doesn't measure anything.

My point - pretty clear from what I said - is that you cannot use a shunt to measure a source voltage. It allows something to measure the voltage across it, which indicates a current. You CAN NOT measure a voltage of a source you are trying to measure with shunt. Flat out. You CAN NOT do that. A shunt is meant to measure a current. End of story.
 
Ok, so you are getting aggressive.

A shunt doesn't measure anything.

My point - pretty clear from what I said - is that you cannot use a shunt to measure a source voltage. It allows something to measure the voltage across it, which indicates a current. You CAN NOT measure a voltage of a source you are trying to measure with shunt. Flat out. You CAN NOT do that. A shunt is meant to measure a current. End of story.
I'm not trying I measure voltage. We don't care about voltage for this.

You're confusing the "proper" application with the intended one.

All that matters is seeing that the heater is turned on. A high vs low mv reading from a shunt does that just fine.

If anything reading current is more valuable for a heater pad anyways, but that's irrelevant.
 
I'm not trying I measure voltage. We don't care about voltage for this.
Let's go back to where you started. You posted about a data logger that supports 4 thermocouple inputs. I asserted (and no one has said I was wrong) that thermocouples generate a VOLTAGE according to the temperature of the probe. That is as opposed to an NTC probe, which varies in resistance based on the temperature.

So that means your meter measures voltage. If that is not true, explain how it works with thermocouples.

That means - like I said - that if you want to have it log voltage, you only need to use a voltage divider to get the voltage to something the meter can interpret.

But you have decided that maybe it makes more sense to use a shunt - which by definition is only used to measure a current - to somehow convert a voltage (which you said you wanted to measure) to something your meter can log.

I dunno. Seems like you've talked in a complete circle, and tried to make something much harder than it needed to be.
 
If the temperature sensor produces voltage.... you want to log this voltage.

Then you need the temperature coefficient to convert voltage to temperature.
 
If the temperature sensor produces voltage.... you want to log this voltage.

Then you need the temperature coefficient to convert voltage to temperature.
In fairness, it's simpler than that. He already has a temperature logger that he likes. It uses thermocouples, which I believe uses voltage to indicate temperature. My understanding is that he wants to use one channel to log voltage. So he just wants to convert voltage to voltage, in a way that the logger can understand. I would probably come out as a temperature, but as long as you know what you are looking at, it doesn't matter.
 
Let's go back to where you started. You posted about a data logger that supports 4 thermocouple inputs. I asserted (and no one has said I was wrong) that thermocouples generate a VOLTAGE according to the temperature of the probe. That is as opposed to an NTC probe, which varies in resistance based on the temperature.

So that means your meter measures voltage. If that is not true, explain how it works with thermocouples.

That means - like I said - that if you want to have it log voltage, you only need to use a voltage divider to get the voltage to something the meter can interpret.

But you have decided that maybe it makes more sense to use a shunt - which by definition is only used to measure a current - to somehow convert a voltage (which you said you wanted to measure) to something your meter can log.

I dunno. Seems like you've talked in a complete circle, and tried to make something much harder than it needed to be.
I know what I said.

The resulting form of data from a shunt is millivolts.
The thermocouple logger accepts millivolts in a given range.

Heaters turn on, current goes up, millivolts go up, TC logger reads high.

I didn't talk in a circle at all because I never changed my statement.

Building a whole other circuit when I have a cheap shunt laying around is silly.
 
I know what I said.

The resulting form of data from a shunt is millivolts.
The thermocouple logger accepts millivolts in a given range.

Heaters turn on, current goes up, millivolts go up, TC logger reads high.

I didn't talk in a circle at all because I never changed my statement.

Building a whole other circuit when I have a cheap shunt laying around is silly.
Ok. I guess. The "other circuit" would only be two tiny resistors, but you can do what you want to.
 
Ok. I guess. The "other circuit" would only be two tiny resistors, but you can do what you want to.
Yeah.

But I have a shunt that already outputs the range needed.

While I have resistors laying around I have no idea if they're of sufficient values.
 
If you are trying to use a lifepo4 battery in freezing cold temperatures, battle born just released a 12v heat pad for keeping the batteries warm without melting the case. This pad should work for any standard lifepo4 battery. Just slap it under your batteries and connect it to 12v and you are done.

I think it is over priced though. It can be found here: Click Here for battle born heater pad


If you cannot afford the battle born pad, you can use a septic tank heater pad. It works in the same way but may possibly melt your battery case if you are not careful. You can avoid this by adding some protection or a way to distribute the heat across your entire battery bank. I would personally put the batteries in a insulated container, then add a thin sheet of conductive material like sheet aluminum over the pad so that the heat it produces can warm up your entire battery bank.

Cheaper heater pad source: Click here for heater pad
Would these work under a Bluetti AC200P?
Any reason I shouldn’t try it?
TIA
Woops
 
Would these work under a Bluetti AC200P?
Any reason I shouldn’t try it?
TIA
Woops
I use the second approach with the septic tank pads. Seems to work well so far, but they do draw some wattage, so long cold spells without sun could sap the batteries a bit.
 
Would these work under a Bluetti AC200P?

I suspect warming works better when the bare battery can touch the warmed surface. The case around a battery in a Bluetti or similar device might interfere with heat transfer but I assume it would work. Maybe watch a teardown to see where the cells are physically situated within the case?

For reference, it was 27F last night and a 16w pad kept my 100Ah batt at 59F without issue. It was 34F in the camper this morning. The BB GC2 pads are 30w and the tank warmers are 65w.

If you use a warmer with the Blu let us know the results.
 
Can anyone advise a source for the 12v or 24v temperature controller? The links previously in thread are sold out.
 
This is the one that I've used and it shows in stock.

I'm getting 'currently unavailable' for that one when I open it. Maybe because I am in canada.
 
Back
Top