12V LiFePO4 and NOCO Battery Discussion
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Matt: stay focused on the issue at hand. I almost moved the NOCO discussion to a new thread but thought the topic was worth discussing in this one.. Edit: this is now in the LiFePO4 and NOCO dedicated thread.
The measurement of the 12v battery should be made at the battery itself, as anywhere else (e.g., auxiliary outlet) the measurement is not accurate due to intermediate losses.
What I have done to every 12v battery in each of my cars is attached a fused pigtail terminating in a small Anderson PowerPole connector which I use for measuring the battery voltage or for attaching various chargers to the battery. Many chargers come with such a fused pigtail with an SAE connector on one end and circular terminals on the other.
Before I forget, DO NOT use an unadjustable float charger (e.g., Battery Tender) on the NOCO as their upper voltage limits often exceeds the NOCO's max voltage spec. If using a regular battery charger, make sure it has settings and specs that allow you to set it so the max voltage of 14.6v is not exceeded; if you don't already have one like that, then you might again consider one of the NOCO chargers designed for LiFePO4 even though I had originally thought you might not need to.
I'm now kicking myself for having suggested that you might live with the NOCO you had already bought. My i-MiEV has never seen sub-zero (°C).
Remember, you're facing three problems, all low-temperature related, if you install the NOCO LiFePO4 battery:
1. The NOCO BMS won't allow it to be charged below -10°C per NOCO's manual. I think that stops you right there from using the NOCO in the car in those temperatures. We don't know what NOCO's protective scheme is for their battery, even though they do say it recovers when it's back within its operating specs. Trying to keep the battery itself warm is possible (e.g., the superb Battleborn LiFePO4 batteries now come with their own built-in heating element) but not something you could easily add on.
2. The i-MiEV dc-dc is suspected (but we don't know that yet) of putting out a voltage in excess of 14.6vdc at low temperatures - WE NEED TO MEASURE THIS
3. The NOCO may open its connection to the battery (we don't know that) if it experiences temperatures below 10°C or a voltage above 14.6v (when either charging or driving) in order to protect the battery, but that could destroy the i-MiEV's dc-dc - a $5000 expense! I'M AWAITING RESPONSE FROM NOCO
Let's stay focused: first measure the voltage at your old FLA battery at a low temperature (~0°C) with the i-MiEV in READY to at least put the second concern to bed.
In the meantime, I now think you'd be better off replacing your existing old FLA with an inexpensive new FLA or AGM and save your NOCO for next summer - this may be your safest, least-expensive, and most reliable option.
The measurement of the 12v battery should be made at the battery itself, as anywhere else (e.g., auxiliary outlet) the measurement is not accurate due to intermediate losses.
What I have done to every 12v battery in each of my cars is attached a fused pigtail terminating in a small Anderson PowerPole connector which I use for measuring the battery voltage or for attaching various chargers to the battery. Many chargers come with such a fused pigtail with an SAE connector on one end and circular terminals on the other.
Before I forget, DO NOT use an unadjustable float charger (e.g., Battery Tender) on the NOCO as their upper voltage limits often exceeds the NOCO's max voltage spec. If using a regular battery charger, make sure it has settings and specs that allow you to set it so the max voltage of 14.6v is not exceeded; if you don't already have one like that, then you might again consider one of the NOCO chargers designed for LiFePO4 even though I had originally thought you might not need to.
I'm now kicking myself for having suggested that you might live with the NOCO you had already bought. My i-MiEV has never seen sub-zero (°C).
Remember, you're facing three problems, all low-temperature related, if you install the NOCO LiFePO4 battery:
1. The NOCO BMS won't allow it to be charged below -10°C per NOCO's manual. I think that stops you right there from using the NOCO in the car in those temperatures. We don't know what NOCO's protective scheme is for their battery, even though they do say it recovers when it's back within its operating specs. Trying to keep the battery itself warm is possible (e.g., the superb Battleborn LiFePO4 batteries now come with their own built-in heating element) but not something you could easily add on.
2. The i-MiEV dc-dc is suspected (but we don't know that yet) of putting out a voltage in excess of 14.6vdc at low temperatures - WE NEED TO MEASURE THIS
3. The NOCO may open its connection to the battery (we don't know that) if it experiences temperatures below 10°C or a voltage above 14.6v (when either charging or driving) in order to protect the battery, but that could destroy the i-MiEV's dc-dc - a $5000 expense! I'M AWAITING RESPONSE FROM NOCO
Let's stay focused: first measure the voltage at your old FLA battery at a low temperature (~0°C) with the i-MiEV in READY to at least put the second concern to bed.
In the meantime, I now think you'd be better off replacing your existing old FLA with an inexpensive new FLA or AGM and save your NOCO for next summer - this may be your safest, least-expensive, and most reliable option.
Mitsi
Member
JoeS said:
:lol: Me stay focused? OK, so I tried this morning at about 3C and the FLA was sitting at 6.3V (deaders). Wouldn't go to ready, so I boosted with the Noco booster for a few seconds and she fired up. Took the booster off and she remained steady ready. Measured 14.6V at the battery, sometimes flickering down to 14.5V. Measured 14.5 at the cigarette lighter socket.
Wouldn't it be nice if we could just drop a little 10A solar panel in the windshield and plug it in to the lighter socket and be done?
Oops, "Stay focused, Matt." :shock: :lol:
Will measure again when below zero.
Cheerios, Matt
Matt, are you now talking about applying a charger to your existing FLA? The lighter socket inside the car is disabled (open circuit) when the car is OFF. Best to connect any charger directly to the 12v battery.Mitsi said:
As you might have gathered from the OBC/dc-dc discussions and weird problems with i-MiEVs over the years, it's best not to risk a 12v undervoltage and simply have a good solid 12v battery in place. Cheap insurance.
Good information! The voltage at 3°C being 14.6v is not as high as I had feared (but is right at the upper limit of the NOCO LiFePO4 battery). The proof of the pudding will be voltage readings at -10°C - -20°C.Mitsi said:
10A solar panels are NOT little, but even a 2A panel with regulator should work, but you'd have to attach it directly to the battery. In my mild climate I regularly use a 1/2A solar panel through a regulator to float the 12v batteries of cars that are hibernating.Mitsi said:
That said, I think your FLA battery is dead and you should replace it ASAP as we are fearful of what it might be doing to the dc-dc (think $$$$). Try finding any old Group 151R battery to stick in there. Edit: for example, I saw one at Walmart the other day for US$150, but you should be able to do much better.
So, I exchanged a number of emails with NOCO tech support. They were nicely responsive.
Here's what I first asked them -
a) When your battery is subjected to an overvoltage from a charging circuit which exceeds 14.6vdc, what is the response of your battery BMS? Specifically, does it open the circuit going to your cells and does that result in an open circuit seen by the charging circuit? If not, then what does it do?
b) What is the exact voltage at which your BMS OVP kicks in? It can't be exactly 14.6volts (because that is your recommended charging voltage) but is some higher number - what is it, exactly?
In my vehicle application there is a possibility that the charging voltage might be exceeded in some specific circumstances and I need to understand your battery's response to this so I can incorporate the appropriate protection for both my vehicle and your battery.
Whoops, I was going to cut-and-paste their response, but realize that I should perhaps ask their permission to publish it here. Let me just paraphrase what they said -
The battery BMS will disable charging when any cell reaches a particular overvoltage, which could happen somewhere between 14.6V and 15.6V (worst case). They said that under this fault condition, the battery cannot be charged until the battery voltage returns to an acceptable level but that the battery can still be discharged during this fault condition.
My take on this answer is that our dc-dc is not going to get much above 14.6v so we don't need to worry about ever getting close to their upper limit. Matt (mitsi) will still try to do some low temperature tests to verify this.
They also wanted to know what vehicle this is going into. So I told them it was an i-MiEV, with the battery fed by a dc-dc converter, gave them a bit of background information, asked them if they have a relay disconnect, discussed upper limits of LiFePO4, and followed up with two more questions:
1) With ambient temperature dropping below -10°C, does your BMS suddenly open-circuit the battery connection to the vehicle?
2) Is the possibility of my dc-dc being able to supply a current higher than 24A to your discharged battery a concern, recognizing that the dc-dc voltage is normally 14.4vdc?
To which they responded (I've paraphrased their answer) -
There are no relays in the battery. At -10°C the BMS will disable charge but discharge will still be allowed, and that charging will not be possible until the battery warms up above -10°C. They allowed as occasionally exceeding 24A should be okay if the battery gets very low. They thought the NLP30 should work fine in our use case, the biggest concern being the longer-term parasitic load of an unattended vehicle which we are well aware of.
Recall, also, that their battery maximum discharge current is spec'd. at 80A!
Edit 12/18/21: I also note that they don't say specifically what they do in the overvoltage, undervoltage, or under-temperature conditions, other that the battery is protected by the BMS and cannot be charged or won't be further discharged and that it doesn't have a relay to suddenly disconnect the battery from the i-MiEV
MY CONCLUSIONS
The NOCO LiFePO4 should work just fine in everyday use in a moderate climate and I'll continue using it in my i-MiEV. If I leave the car unattended for more than a few days, I'll use a small 13.4vdc power supply as a voltage maintainer to counteract our vampire load.
For what I consider low temperatures (below 0°C and especially -10°C and below), I simply wouldn't chance it and personally would not use the NOCO in those conditions. The overriding concern is protecting our very expensive i-MiEV dc-dc.
Here's what I first asked them -
a) When your battery is subjected to an overvoltage from a charging circuit which exceeds 14.6vdc, what is the response of your battery BMS? Specifically, does it open the circuit going to your cells and does that result in an open circuit seen by the charging circuit? If not, then what does it do?
b) What is the exact voltage at which your BMS OVP kicks in? It can't be exactly 14.6volts (because that is your recommended charging voltage) but is some higher number - what is it, exactly?
In my vehicle application there is a possibility that the charging voltage might be exceeded in some specific circumstances and I need to understand your battery's response to this so I can incorporate the appropriate protection for both my vehicle and your battery.
Whoops, I was going to cut-and-paste their response, but realize that I should perhaps ask their permission to publish it here. Let me just paraphrase what they said -
The battery BMS will disable charging when any cell reaches a particular overvoltage, which could happen somewhere between 14.6V and 15.6V (worst case). They said that under this fault condition, the battery cannot be charged until the battery voltage returns to an acceptable level but that the battery can still be discharged during this fault condition.
My take on this answer is that our dc-dc is not going to get much above 14.6v so we don't need to worry about ever getting close to their upper limit. Matt (mitsi) will still try to do some low temperature tests to verify this.
They also wanted to know what vehicle this is going into. So I told them it was an i-MiEV, with the battery fed by a dc-dc converter, gave them a bit of background information, asked them if they have a relay disconnect, discussed upper limits of LiFePO4, and followed up with two more questions:
1) With ambient temperature dropping below -10°C, does your BMS suddenly open-circuit the battery connection to the vehicle?
2) Is the possibility of my dc-dc being able to supply a current higher than 24A to your discharged battery a concern, recognizing that the dc-dc voltage is normally 14.4vdc?
To which they responded (I've paraphrased their answer) -
There are no relays in the battery. At -10°C the BMS will disable charge but discharge will still be allowed, and that charging will not be possible until the battery warms up above -10°C. They allowed as occasionally exceeding 24A should be okay if the battery gets very low. They thought the NLP30 should work fine in our use case, the biggest concern being the longer-term parasitic load of an unattended vehicle which we are well aware of.
Recall, also, that their battery maximum discharge current is spec'd. at 80A!
Edit 12/18/21: I also note that they don't say specifically what they do in the overvoltage, undervoltage, or under-temperature conditions, other that the battery is protected by the BMS and cannot be charged or won't be further discharged and that it doesn't have a relay to suddenly disconnect the battery from the i-MiEV
MY CONCLUSIONS
The NOCO LiFePO4 should work just fine in everyday use in a moderate climate and I'll continue using it in my i-MiEV. If I leave the car unattended for more than a few days, I'll use a small 13.4vdc power supply as a voltage maintainer to counteract our vampire load.
For what I consider low temperatures (below 0°C and especially -10°C and below), I simply wouldn't chance it and personally would not use the NOCO in those conditions. The overriding concern is protecting our very expensive i-MiEV dc-dc.
Mitsi
Member
Happy New Year JoeS and iMievers!!!
Well it's been a little warm in T.O., but finally last night we hit -11C and I tested at about -8C this morning surprised to find that our FLA battery still had enough juice to start her up after sitting in the cold for two days. (PS. I've sprayed the top of the battery with WD-40 to reduce any moisture conduction causing charge depletion. My battery cover is removed to allow quick access.)
Testing first from the inside, through the lighter port, I saw the voltage jump from 10 up to 14.38V as I started her up. I quickly popped the boot, jumped out and measured 14.58V at the battery posts. So far no higher voltages for lower temps. Maybe it will get really cold here, like -20 or -30, and I will report again.
Cheers, Matt
PPS: Hey Joe, what about these DC-DC battery chargers? Could get a little hybrid battery system going. How about 12V battery self-warmer for below -10C. :idea:
Well it's been a little warm in T.O., but finally last night we hit -11C and I tested at about -8C this morning surprised to find that our FLA battery still had enough juice to start her up after sitting in the cold for two days. (PS. I've sprayed the top of the battery with WD-40 to reduce any moisture conduction causing charge depletion. My battery cover is removed to allow quick access.)
Testing first from the inside, through the lighter port, I saw the voltage jump from 10 up to 14.38V as I started her up. I quickly popped the boot, jumped out and measured 14.58V at the battery posts. So far no higher voltages for lower temps. Maybe it will get really cold here, like -20 or -30, and I will report again.
Cheers, Matt
PPS: Hey Joe, what about these DC-DC battery chargers? Could get a little hybrid battery system going. How about 12V battery self-warmer for below -10C. :idea:
Mitsi, welcome back after the holidays!
Interesting concept spraying the top of the battery with WD-40. I prefer to keep the top squeaky clean rather than put that stuff on as to me it is a bit messy and tends to attract dirt.Mitsi said:
Wow, thank you so much for taking this measurement. So, at -8°C we see only 14.58vdc from the dc-dc, which still puts it into the safe range with the NOCO LiFePO4 battery. I'm amazed that the i-MiEV came to life with only 10v on the 12v battery.Mitsi said:
Um, you didn't provide a link to what you were looking at. The word "c h a r g e r" is one of those that automatically triggers a link and often messes up the context of our posts. Any heater that uses the 12v battery may well deplete our small i-MiEV 12v overnight and especially if we try it on a NOCO; however, plugging a heating pad into the wall (like an ICE block heater) would certainly work.Mitsi said:
NOCO UPDATE
I installed the NOCO 7.8Ah LiFePO4 battery on December 6. The longest I went without driving the car has been three days, and have never attached my float charger (Meanwell power supply set to 13.4vdc).
Removed my OBDLink MX since it consumes 60ma. I'll be plugging it back in during longer trips as I like to see the CaniOn energy consumption efficiency information while driving.
The results are ho-hum. The quiescent voltage of the NOCO with the car turned off has been exactly 13.40vdc after the car has been sitting in my ~55°F garage overnight. After turning on the car to READY, the battery reads ~14.5vdc (set by the dc-dc). All measurements are right at the battery.
No drama.
I installed the NOCO 7.8Ah LiFePO4 battery on December 6. The longest I went without driving the car has been three days, and have never attached my float charger (Meanwell power supply set to 13.4vdc).
Removed my OBDLink MX since it consumes 60ma. I'll be plugging it back in during longer trips as I like to see the CaniOn energy consumption efficiency information while driving.
The results are ho-hum. The quiescent voltage of the NOCO with the car turned off has been exactly 13.40vdc after the car has been sitting in my ~55°F garage overnight. After turning on the car to READY, the battery reads ~14.5vdc (set by the dc-dc). All measurements are right at the battery.
No drama.
Mitsi
Member
I have tested at below -10C and the voltage from the dc-dc did exceed 14.6V to about 14.8. But I guess that's a moot point if the Noco won't allow itself to be charged at those temps anyway. In the end I decided to use a Noco "Repair & Maintenance" charger on the old battery. It has a repair cycle which does some magic, probably pulse charging and heating the battery, to return a sulphated or settled battery to operation. I also hooked it up to maintain the battery charge while parked. So far, so good. Maybe will use the Noco battery in summer or use it for something else. I did get a battery heating jacket which fits nicely on the current SLAb, but I haven't used it yet. I'm hesitant to use it without a thermostat regulated power cord, to shut it off when temperatures are above freezing.
Thank you JoeS for the attention and experimentation with the Noco battery. It has been educational. :mrgreen: Cheers all!
Thank you JoeS for the attention and experimentation with the Noco battery. It has been educational. :mrgreen: Cheers all!
JoeS said:
Just so you're aware, you have to explicitly set the things to sleep when idle
You can do it using ODBLink's software and it's a persistent setting
Personally I'm considering adding a switched 12v feed to mine for much the same reason as my one keeps losing its marbles if left plugged in for extended periods, then demanding bluetooth repairing (You can buy a ODB2 extension lead pretty cheaply, so no hacking of the vehicle harness is required)
NOCO Long Term Update - So Far, So Good
Been running the little 8Ah Noco LiFePO4 for about a year total (excluding the downtime using a very different 12v scheme when my OBC was out) in my daily-driver i-MiEV in our mild San Francisco Bay climate. Simply put, nothing has happened as the voltage sits at around 13.3vdc with power off and then jumps up to somewhere around 14.2v-14.4v (temperature dependent) when the car goes into READY. I use a small Meanwell power supply set to 13.4vdc as my 'float charger' whenever I leave the car unused for more than about four days.
https://www.amazon.com/gp/product/B091P9P92V
Note that my climate does not go below 0°C so the i-MiEV's dc-dc does not put out over 14.4vdc, which is within the Noco's spec'd maximum voltage limit of 14.6vdc.
Been running the little 8Ah Noco LiFePO4 for about a year total (excluding the downtime using a very different 12v scheme when my OBC was out) in my daily-driver i-MiEV in our mild San Francisco Bay climate. Simply put, nothing has happened as the voltage sits at around 13.3vdc with power off and then jumps up to somewhere around 14.2v-14.4v (temperature dependent) when the car goes into READY. I use a small Meanwell power supply set to 13.4vdc as my 'float charger' whenever I leave the car unused for more than about four days.
https://www.amazon.com/gp/product/B091P9P92V
Note that my climate does not go below 0°C so the i-MiEV's dc-dc does not put out over 14.4vdc, which is within the Noco's spec'd maximum voltage limit of 14.6vdc.
This thread was created on 10 February 2024 by extracting all (I think?) the 12v LiFePO4 discussions from the 12v Battery - All You Ever Wanted To Know thread.
BTW, my NOCO NLP30 8Ah 12v battery continues to work admirably in my daily driver and I haven't seen its voltage (as measured at the cabin lighter socket) ever drop below 13.0vdc.
Mind you, I don't sit there with the car in ACC for more than a couple of minutes at a time, as it's always either OFF or in READY (when the dc-dc then powers the car).
Recall the caveat that if the car is not driven for more than about four days I always plug in a 13.4v power supply onto this battery. If I were to take the car to the airport and leave it for a few weeks I would disconnect the 12v battery while there.
BTW, my NOCO NLP30 8Ah 12v battery continues to work admirably in my daily driver and I haven't seen its voltage (as measured at the cabin lighter socket) ever drop below 13.0vdc.
Mind you, I don't sit there with the car in ACC for more than a couple of minutes at a time, as it's always either OFF or in READY (when the dc-dc then powers the car).
Recall the caveat that if the car is not driven for more than about four days I always plug in a 13.4v power supply onto this battery. If I were to take the car to the airport and leave it for a few weeks I would disconnect the 12v battery while there.
FYI, I also tried this mod but with OVMS and hardwired dashcams, I kept getting the 12v battery going low enough that my car alarm would go off all the time, annoying the neighbours to no end. I had to switch back to lead acid and these keep dying every year, so I think my next step is to find a higher capacity battery, lithium or lead-acid.
I suspect that your dashcams only turn on when the car is in ACC or READY(?); however, your OVMS is attached to the OBDII port and draws how much current?
I had previously found that my bluetooth dongle IIRC drew about 60ma which, over 24 hours means 1.44Ah and if I were leave my car untouched over the course of five days that would pretty much flatten my 8Ah LiFePO4 battery. I have Anderson PowerPole connectors on every 12v battery and I'm in the habit of attaching a 12v power supply or float charger if a car is to sit for more than about four days.
