MrNatural22
?SW sunshine =⚡️⚡️lit up thru the darkness✌️
I’ll let you know when it gets there. Started at 10am today.
Maximizing Alpicool AC/DC 26Q/25L fridge run-time..
- Thread starter fred333
- Start date
MrNatural22
?SW sunshine =⚡️⚡️lit up thru the darkness✌️
Update on 12v run time for the fridge third day running on the 12v 100ah LiFePo. 75hrs.I’ll let you know when it gets there. Started at 10am today.
This is the current battery state on the fridge display Victron CC, BMS and Ali meter.
What does the 54w reference?
And is there a way to connect your (fully-charged) 100Ah battery directly to the fridge (i.e., without ANY potential for incoming charging anywhere in the circuit) and just use the fridge's incoming voltage indicator along with an external voltmeter to take daily (or hourly) voltage measurements?
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Something in your screenshots just caught my eye that might be key here: "Three days ago", you began with a battery that was charged to 14.4V—that's, as's been mentioned previously, a whole two volts more than my lithium's even capable of charging to. So, coupled with the fact that I'm seeing my battery's capacity dropping ~1 volt/day, that might give your battery two additional days of run-time for the fridge right outta the gate.
The question now is: once your battery reaches 12.6V—which is my battery's starting/fully-charged state—how many days will it run? If your battery only runs for two days before reaching the 20 percent level, then that means: 1) you're only getting two additional days (still short of my week target); and 2) the additional days are due to your battery's higher charging point of 14.4V rather than mine's 12.6V.
Depending on your response, we might be getting somewhere....
The question now is: once your battery reaches 12.6V—which is my battery's starting/fully-charged state—how many days will it run? If your battery only runs for two days before reaching the 20 percent level, then that means: 1) you're only getting two additional days (still short of my week target); and 2) the additional days are due to your battery's higher charging point of 14.4V rather than mine's 12.6V.
Depending on your response, we might be getting somewhere....
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MrNatural22
?SW sunshine =⚡️⚡️lit up thru the darkness✌️
That 14.4v is what the battery was at when I began.
The 54w 4.3a is the max draw when the compressor starts. It drops to 43w and 3.24a when running.
The fridge IS connected directly to the battery on a cig plug adapter.
the neg is connected after the shunt so I can monitor usage.
Lifepo is charged to full at 14.6v. 3.65 v per cell x 4 cells = 14.6v. They rest after a few hours at 13.4v - 13.6v.
Apples to oranges ? > ?
You do not have a LiFePo battery.
You have an NMC battery that has 3 cells at 4.2v = 12.6v.
My LiFePo is now at 57.1% SOC 13.1v
That’s 3 full days + 8 hrs. 80 hrs so far?
Pretty sure at 10 am tomorrow (4days) it will still be operating.
Not at all. We're veering off into Misunderstandingland.
A fully charged battery is a fully charged battery. Period. Peak voltage doesn't matter. A 1000Wh battery is independent of voltage, i.e., it will give 100W for 10 hours or 500W for 2 hours, etc. It doesn't matter what the operating voltage is except that it will deliver the POWER between the full and empty voltages.
By your logic, he should only start his battery when it is almost empty at 12.6V, but he must stop at 10V because that's where the chemistry says to stop, but you get to operate from 12.6V (full) to 9V (empty).
While you are misinterpreting things, you are scratching at the surface of something important. Your battery operates at a lower voltage. Thus it must operate at a higher current to produce the same power. Lower voltage + higher current = less efficient than higher voltage + lower current. This is the same point I was making about how a fridge operating at 24V can be more efficient than at 12V - less resistive losses at higher voltages.
Here's an example:
100W /12.8V = 7.8A (his LFP battery)
100W / 11.25V = 8.9A (your NMC battery)
100W/ 25.6 = 3.9A (a 24V LFP battery)
He is comparing his 102Ah * 12.8V = 1305Wh battery to your 1100Wh battery. He has 18.6% more battery capacity than you do. Trying to point to 12.6V vs. 14.4V as a significant portion of the difference in run time is a red herring.
I may very well be missing something, but this's the part that's confusing: If his battery's got ~18% more capacity than my battery, shouldn't his total run-time be ~18% more than mine? That is, my run-time, 54 hours, plus an additional 10 hours (i.e., 54 x 18.6% = 10) rather than an additional 300%-400%+ increase in run-time?
I guess I'm not understanding how the differing 12V battery chemistries and Ah ratings (i.e., 90Ah vs 100Ah) can so drastically change the amount of time each is able to run similar 12V loads....if it has little or nothing to do with their starting voltage capacities (12.6V vs 14.4V)?
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It likely has everything to do with his direct connection to the battery, where you're forced to go through the circuitry of the Apex unit.
His battery doesn't consume any power itself. Your Apex does. Your Apex powers additional circuitry to deliver 12V. Even a measly 5W of draw is 10% of your battery capacity/day. In addition to that, it's not 100% efficient. Consider also the USB ports are consuming a very small amount of power even when not used due to the 5 VDC conversion.
He has tested his battery and confirmed it actually has 102Ah @ 12.8V. You have to assume yours meets spec.
His battery doesn't consume any power itself. Your Apex does. Your Apex powers additional circuitry to deliver 12V. Even a measly 5W of draw is 10% of your battery capacity/day. In addition to that, it's not 100% efficient. Consider also the USB ports are consuming a very small amount of power even when not used due to the 5 VDC conversion.
He has tested his battery and confirmed it actually has 102Ah @ 12.8V. You have to assume yours meets spec.
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Re direct battery connection: See post 49.
Re confirming battery's to spec: Other than verifying the battery's topped at 12.6V at the beginning of all testing (as measured from the Apex's external, always-on 12V terminals), how else can I verify its 90Ah rating?
If that's a live terminal, it is going to range from 12.6V to 9.XV during the discharge. Have you confirmed the fridge will work at 9.X volts?
Operating at a lower voltage can be inherently less efficient, and the fridge may refuse to operate below a given voltage.
Yes, like many of these 12V portable "car" fridge/freezers, the Alpi' includes switchable—Hi, Middle and Lo—Battery Protection Modes that allow the user to set the voltage at which the fridge will auto-shut OFF to protect the battery and/or to insure the battery's got sufficient charge to start the vehicle. The Lo setting shuts the Alpicool MK25 OFF at 9.6VDC.
All my tests were performed at the Lo setting. That said, because I don't want to run the Apex's battery below ~15~20% remaining capacity, I've always stopped testing when the Alpi's voltage reaches ~10.1V; and the Alpi's never auto-shut OFF during my testing. Does that help?
MrNatural22
?SW sunshine =⚡️⚡️lit up thru the darkness✌️
Update:
Day 4 after running for 98 hrs@ 32deg F
Inside the trailer.
48w 3.69a during compressor cycle.
(Edit to show date and time)
Day 4 after running for 98 hrs@ 32deg F
Inside the trailer.
48w 3.69a during compressor cycle.
(Edit to show date and time)
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It helps ensure you're not using your full battery capacity. There's probably 15-20% left at 10.1V, so now you have a 880-935Wh battery.
MrNatural22
?SW sunshine =⚡️⚡️lit up thru the darkness✌️
In case there's any interest on these Alpicool/Massimo fridges I just came across this new offering from Costco
On the web site there are three sizes offered.
On the web site there are three sizes offered.
Sorry, snoobler, but you lost me here?
If I've used ~80%+ (i.e., 15-20% left at 10.1V) of an 1,100Wh battery, how do I have 880-935Wh+ left?
You not utilizing the full capacity of the battery means you've turned a 1100Wh battery into a 880-935Wh for your application.
So it's safe to use 100% of the battery's 1,100Wh/90Ah capacity (i.e., run it down to 0% remaining capacity)? Doing so, I'd estimate an additional .5 day of run-time, giving me a total of < three days. Still far short of my bottom line goal—a week.....and the reports of others who're doubling or tripling that with similar or ~20% larger battery capacities.
Bud Martin
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But at this point does your abttery actually has 90Ah capacity as I suggested before? You need to get some equipment to verify.
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Shallower cycling will get you more cycle life from the battery, but they can typically endure 300+ 100% discharge cycles before they degrade below 80% rated.
What do I need?
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