Jumping 12 volt battery

[TaxmanHog]

Assuming the jump pack has sufficient watt-hour capacity and no logic controls that prevent it from working, ie. attached to a stone dead vehicle battery and damaging the jump pack, that it can work for a limited amount of time.

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[Heliian]

Just like trying to run an ice with a flat battery, it might not work either. The alternator supplies a charge but still needs the load of a battery to run the computers and ignition.

 

[RickLightning]

when I bought our second used 2014 Nissan LEAF, the owner was about to tell me that the deal might be off because he suddenly realized that he could not get the car to even come on, much less drive anywhere...

I already 'knew' enough about the 12v vs Drive battery of electric vehicles, and correctly identified that it was simply that the 12v battery was dead.

I pulled my 2014 Ford Focus up to it, attached the jumper cables to the Leaf's battery, and then to the Focus's battery, and 'voila, the Leaf could now be turned 'ON'.
Now, for the second part...

I detached the jumper cables, and got into the Leaf to take it for it's test drive... nope, no go.
The Leaf would not go into 'gear'... after a few minutes of 'wondering' what could be amiss, I realized that it was just that the 12v battery still did not have 'enough' juice to get everything in place to get the care going... so, back to 'jumping' the Leaf from the Focus, although this time it was more about 'charging' the Leaf's battery, versus just getting it to turn 'ON'... all is well that ends well, and it did.

That Leaf was a terrific car, and it was sold several years later at a HIGHER price than I'd paid for it.

Exactly.

 

[RickLightning]

From the Mach-E forum. No reason to think the Lightning is different:

The Mach-E has a huge inrush current (>200 amps) when you connect the battery (lots of capacitors charging), which means that you need a very beefy battery charger or jump pack to "boot up" the modules. If the battery charger or jump pack is too small, it will boot loop trying to initialize modules and the lights will just flash on and off since the car is using more current than can be supplied.

If you are stuck without a big enough battery charger, you will have to completely disconnect the 12V battery from the car while charging it (need a 10 mm socket). After the battery is fully charged, then reconnect it to the Mach-E. You will get a big spark and then hopefully everything comes to life.

Many jump start attempts have failed on the Mach-E due to the high inrush current and inadequate jumper packs being used.

 

[Fryballin]

From the Mach-E forum. No reason to think the Lightning is different:

The Mach-E has a huge inrush current (>200 amps) when you connect the battery (lots of capacitors charging), which means that you need a very beefy battery charger or jump pack to "boot up" the modules. If the battery charger or jump pack is too small, it will boot loop trying to initialize modules and the lights will just flash on and off since the car is using more current than can be supplied.

If you are stuck without a big enough battery charger, you will have to completely disconnect the 12V battery from the car while charging it (need a 10 mm socket). After the battery is fully charged, then reconnect it to the Mach-E. You will get a big spark and then hopefully everything comes to life.

Many jump start attempts have failed on the Mach-E due to the high inrush current and inadequate jumper packs being used.

This is very helpful. The Noco GBX55 that I posted a picture of at the start of the thread has a peak current rating of 1750 amps which should be more than enough to handle that inrush current and much more. It also has a 46 watt hour lithium ion battery which may prove useful if needing to leave the jump box connected in order to drive the EV.

 

[On the Road with Ralph]

The quality of the responses on this thread varies a lot. Here are the basic facts:

A jump box of at least 700-800 peak amps ought to be enough to start a Lightning, even if the 12v battery is essentially dead. It accomplishes that feat NOT by charging the 12v battery, but by augmenting whatever power it is able to deliver with the juice from the jump box. It does this by being connected in parallel with the 12v battery. While I have a jump box myself, I have never needed it for the Lightning. However, I did use it to start a previously owned Ford C-MAX Energi PHEV whose battery went flat in the desert heat.

The 12v power is being used for essentially three things on start-up: 1) Basic vehicle electronics; 2) Power-up of the various drive modules (that include a fair number of capacitors that must be filled); 3) Pulling down the primary contactor that engages the high voltage battery. Added together, this power requirement is not trivial, but it is certainly less than starting a V8 ICE engine, especially if it is cold or very hot.

Once the HV battery is engaged, essentially all power in the vehicle comes from it. The HV battery - through the DC-to-DC converter - will attempt to recharge the 12v battery; in the meantime, accessories and electronics will get their power from the HV battery (again, via the DC-to-DC converter). Even if the 12v battery is completely "dead" the Lightning should continue to run after it is started. It is unclear to me what real world event would render the 12v AGM completely dead; it simply might not be able to hold much of a charge. Such a low SOC would be announced to the driver about 87x through the cockpit displays before it became fatal.

Side note: You don't want to leave a lithium-ion jump box connected to the Lightning once it is restarted. The charge curves for li-on and AGM are VERY different, and the DC-to-DC converter is only expecting to "see" an AGM. At some point (tho' probably not immediately), the li-on jump box would be damaged. For the reasons I described in the previous paragraph, the SOC of the 12v battery is irrelevant to whether the truck continues to run once started, and I am doubtful that the 12v battery is needed to ballast the overall system.

If the 12v battery goes below a certain SOC when parked (especially for extended durations), the Lightning will autonomously attempt to recharge it from the HV battery. I am not sure the parameters for this protective feature are fully understood outside of Ford.

It is unclear if the 12v AGM battery supplied as original equipment is correctly sized. In a recent OTA update, Ford has dialed down the frequency of wake-ups the truck does to review its health and report its status; this is a clear effort to reduce 12v power drain. Also, in extreme weather - VERY cold and VERY hot - a less-than-100% healthy 12v battery might lose charge and, in fact, be permanently damaged. As a generally rule, it is best to leave the Lightning on its charger - even if not charging - when it is parked, especially if outdoors.

If I have inaccurately described anything here, I am happy to be corrected. But I am pretty sure that everything I have written is true.

 

[John Becker]

The quality of the responses on this thread varies a lot. Here are the basic facts:

A jump box of at least 700-800 peak amps ought to be enough to start a Lightning, even if the 12v battery is essentially dead. It accomplishes that feat NOT by charging the 12v battery, but by augmenting whatever power it is able to deliver with the juice from the jump box. It does this by being connected in parallel with the 12v battery. While I have a jump box myself, I have never needed it for the Lightning. However, I did use it to start a previously owned Ford C-MAX Energi PHEV whose battery went flat in the desert heat.

The 12v power is being used for essentially three things on start-up: 1) Basic vehicle electronics; 2) Power-up of the various drive modules (that include a fair number of capacitors that must be filled); 3) Pulling down the primary contactor that engages the high voltage battery. Added together, this power requirement is not trivial, but it is certainly less than starting a V8 ICE engine, especially if it is cold or very hot.

Once the HV battery is engaged, essentially all power in the vehicle comes from it. The HV battery - through the DC-to-DC converter - will attempt to recharge the 12v battery; in the meantime, accessories and electronics will get their power from the HV battery (again, via the DC-to-DC converter). Even if the 12v battery is completely "dead" the Lightning should continue to run after it is started. It is unclear to me what real world event would render the 12v AGM completely dead; it simply might not be able to hold much of a charge. Such a low SOC would be announced to the driver about 87x through the cockpit displays before it became fatal.

Side note: You don't want to leave a lithium-ion jump box connected to the Lightning once it is restarted. The charge curves for li-on and AGM are VERY different, and the DC-to-DC converter is only expecting to "see" an AGM. At some point (tho' probably not immediately), the li-on jump box would be damaged. For the reasons I described in the previous paragraph, the SOC of the 12v battery is irrelevant to whether the truck continues to run once started, and I am doubtful that the 12v battery is needed to ballast the overall system.

If the 12v battery goes below a certain SOC when parked (especially for extended durations), the Lightning will autonomously attempt to recharge it from the HV battery. I am not sure the parameters for this protective feature are fully understood outside of Ford.

It is unclear if the 12v AGM battery supplied as original equipment is correctly sized. In a recent OTA update, Ford has dialed down the frequency of wake-ups the truck does to review its health and report its status; this is a clear effort to reduce 12v power drain. Also, in extreme weather - VERY cold and VERY hot - a less-than-100% healthy 12v battery might lose charge and, in fact, be permanently damaged. As a generally rule, it is best to leave the Lightning on its charger - even if not charging - when it is parked, especially if outdoors.

If I have inaccurately described anything here, I am happy to be corrected. But I am pretty sure that everything I have written is true.

Any downside to keeping a 12 volt maintainer or AGM charger plugged into the truck's 120 volt outlet and connected to the 12 volt battery at all times? That way, when the truck is "on," the 12 volt battery will always be charged or charging.

 

[On the Road with Ralph]

Any downside to keeping a 12 volt maintainer or AGM charger plugged into the truck's 120 volt outlet and connected to the 12 volt battery at all times? That way, when the truck is "on," the 12 volt battery will always be charged or charging.

The 120v outlets require that the Lightning be powered on; it seems to me self-defeating to do that in order to maintain the 12v battery SOC.

Let me repeat from my previous post two things:

1) The SOC for the 12v battery only becomes problematic when parked for extended periods of time; extreme heat or cold will acerbate the situation. If the 12v SOC falls below a certain level (it is reported to be 40%, but the actual parameters may only truly be known by Ford), the vehicle will automatically provide power from the HV battery through the DC-to-DC converter to recharge the 12v battery.

2) The entire issue of 12v battery drain can be avoided by just leaving the Lightning on a Level 1 or 2 charger when it is parked.

If you really didn't trust the truck to protect itself, you could connect a 12v trickle charger, suitable for an AGM battery, and power it from a wall outlet near the parked Lightning. But if the parasitic draw is so great that it requires that solution, you have a more serious problem that needs to be identified and fixed. Let me note that aside from the known, programmed drains, the Lightning's electrical system is pretty well sandboxed and is not likely to lead to fully discharging an otherwise healthy battery.

 

[John Becker]

The 120v outlets require that the Lightning be powered on; it seems to me self-defeating to do that in order to maintain the 12v battery SOC.

Let me repeat from my previous post two things:

1) The SOC for the 12v battery only becomes problematic when parked for extended periods of time; extreme heat or cold will acerbate the situation. If the 12v SOC falls below a certain level (it is reported to be 40%, but the actual parameters may only truly be known by Ford), the vehicle will automatically provide power from the HV battery through the DC-to-DC converter to recharge the 12v battery.

2) The entire issue of 12v battery drain can be avoided by just leaving the Lightning on a Level 1 or 2 charger when it is parked.

If you really didn't trust the truck to protect itself, you could connect a 12v trickle charger, suitable for an AGM battery, and power it from a wall outlet near the parked Lightning. But if the parasitic draw is so great that it requires that solution, you have a more serious problem that needs to be identified and fixed. Let me note that aside from the known, programmed drains, the Lightning's electrical system is pretty well sandboxed and is not likely to lead to fully discharging an otherwise healthy battery.

That makes sense. It seems like I've been hearing a lot of problems about the 12 volt batteries running too low. From what I can tell, and unlike an ICE vehicle, the 12 volt battery is not routinely recharged when the vehicle is running or "on." That's why I'm wondering if it might be prudent to keep it charged like an ICE vehicle's alternator would. Or am I wrong about this and the 12 volt battery stays charged by the HV battery when "on"?
This is from a Ford SVE bulletin:
"While ignition status is off, DC-DC is normally off and 12V battery supports the 12V loads.
While ignition is off, if 12V battery reaches 40% state of charge, then vehicle waits 48 hours , before the DC-DC transfers 300 Watt-hours of energy to recharge the 12V battery. The HV power comes from either HV battery or wall power while on plug. If the 12V battery state of charge reaches 30%, then this HV to LV energy transfer happens immediately with no delay.
Note:
• This system was designed to recharge 12V battery while the vehicle was left parked for many days
either on or off plug or occasional drain from customer usage. The 12V battery will wear out if this
energy transfer is completed daily due to aftermarket loads draining the 12V battery down to 40% or
lower.
• Vehicle has 35 Amp-hour AGM 12V Battery"

 

[On the Road with Ralph]

That makes sense. It seems like I've been hearing a lot of problems about the 12 volt batteries running too low. From what I can tell, and unlike an ICE vehicle, the 12 volt battery is not routinely recharged when the vehicle is running or "on." That's why I'm wondering if it might be prudent to keep it charged like an ICE vehicle's alternator would. Or am I wrong about this and the 12 volt battery stays charged by the HV battery when "on"?

When the vehicle is "ON" the DC-to-DC converter is enabled and part of its output will ALWAYS go to restoring the SOC on the 12v battery. How much charge it retains is entirely dependent on the health of the 12v battery.

There have been numerous posts on the 12v battery and its possible entanglement with problems with certain vehicle electronic systems, especially those associated with OTA updates. As I mentioned when I first posted on this thread, I think it is possible that the 12v battery may be slightly undersized, thus making the whole system a bit more vulnerable than it should be in the case of a low 12v SOC.

Your long quote from a Ford SVE bulletin describes how the Lightning deals with extended-duration parking/storage/lack of use. I'm not clear on how long it would take a healthy battery to be drained to 40% (or 30%); my guess is something like 10 to 14 days. Again, the simplest solution is to just leave the Lightning plugged into a Level 1 or 2 charger when parked.

 

[John Becker]

When the vehicle is "ON" the DC-to-DC converter is enabled and part of its output will ALWAYS go to restoring the SOC on the 12v battery. How much charge it retains is entirely dependent on the health of the 12v battery.

There have been numerous posts on the 12v battery and its possible entanglement with problems with certain vehicle electronic systems, especially those associated with OTA updates. As I mentioned when I first posted on this thread, I think it is possible that the 12v battery may be slightly undersized, thus making the whole system a bit more vulnerable than it should be in the case of a low 12v SOC.

Your long quote from a Ford SVE bulletin describes how the Lightning deals with extended-duration parking/storage/lack of use. I'm not clear on how long it would take a healthy battery to be drained to 40% (or 30%); my guess is something like 10 to 14 days. Again, the simplest solution is to just leave the Lightning plugged into a Level 1 or 2 charger when parked.

Great! Thank you for helping me to understand.

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