12v Battery - All You Ever Wanted To Know

[RonSmithJr]

OK, I was able to determine that the 12V battery had died, and replacing it (back in Sept.) fixed the problem.
However now I seem to be having problems with the battery again. Is it possible the battery has gone dead again so soon?

Alternately I checked the fuse for the battery, a 30 amp fusible link. It looks odd to me, but I have not been able to find any picture anywhere of what the fuse looks like when it is undamaged, so I am not certain if the fuse is the problem. Anyone have a picture of a good 30 amp fusible link (Mitsubishi I-miev 2012) they can share?

 

[eldenh]

The system uses a 120 amp fuse link on the right side of the positive connector to recharge the battery.

 

[JoeS]

... Is it possible the battery has gone dead again so soon?...

Not so much dead (yet), but over-discharged. How often have you been using your i-MiEV?

I plug in a wall or solar float charger whenever I know I won't be using the car for even a couple of days, as it keeps the 12v battery from being cycled. Even a drop down to 12.20v means the 12v battery is down to 50%SoC. There is lots of information about lead-acid battery life vs. depth of discharge, all of which points to NOT wanting the battery to discharge much at all! For example, check out the DoD vs Cycle Life graph on this site: https://www.mpoweruk.com/life.htm

 

[RonSmithJr]

I tested the battery and it is fine, i.e. fully charged.
The 30 amp fusible link I am talking about, that looks odd to me, is left of and below the steering wheel (practically on the floor).
What is it supposed to look like when it is good?

 

[Adoepner]

I can confirm that a group 51r 12V battery will fit in the place of the OEM 151r. I could buy an AGM 51r for fractionally more than a FLA 151r. To get the 151r fit with reasonable clearances, I relocated the fuse/relay box that is beside the battery to the left (in a LHD NA model) by 1/2”.

 

[jray3]

I don’t watch Transport Evolved often, but when I do it sometimes sparks a thought.
Nikki alleges that the lack of high starting/charging currents allows EV starting batteries to sulfate up and not break loose that sulfate through vigorous exercise. I’ll buy that theory and posit that the excellent service life of my original battery (preventative replacement after 6 years and 80k miles when OBC failed) was due not in spite of but possibly because of my frequent use of MR BEAN as the jumpstarter of a big diesel truck with parasitic loads. That little flooded battery saw maximum amps many times, but not deep cycling.
https://m.youtube.com/watch?v=pu30bchGu50

 

[CZeroOwner]

I believe I have found the PID with the current to the 12v battery charger. Using garygid's notation it is:

3844 = amps to the 12 volt battery charger on the high voltage side
3844 as D4/100 = amps @ about 360volts

I have included this in OBDZero at the end of the list in the OBD screen. I would really appreciated if someone could check if this is correct.

While I'm at it I am fairly sure I have found the ambient air temperature:

2864 = air temperature in oC
2864 as D4-50 = temperature in oC

This is also included in OBDZero as AirSensor on the OBD screen.

David

 

[stoatwblr]

Battery location:

https://www.dropbox.com/s/uuaq0797acnsrqh/2015-04-08%2019.45.55.jpg

Thread necromancy.....

Is there a writeup on how you ran the cabling back to that position by any chance?

The current (2021) crop of LiFePO4 batteries all seem to have internal BMSes in them so that's one less thng to worry about and I have a webasto I've had for a long time and want to mount in the battery position

 

[stoatwblr]

I still have only experienced battery memory on NiCd, but everyone seems to think that all batteries have memory

It's extremely harmful to store LiIon in deep discharged state (they occasionally ballon or even catch fire) or keep them float charged - they seem to prefer being stored at about 75-80%

NiMH don't like being continually floated or left discharged, but what kills 'em in short order is being reversed - which will burn LiIon

BMSes have come a long way in the last decade. They needed to

 

[PV1]

Of course, each battery chemistry has different care practices, but only NiCD requires full cycles each time to avoid capacity loss. This is due to the physical crystal growth and dissolution that occurs when the battery is cycled.

While detrimental to calendar life, a lithium ion battery won’t lose a bunch of capacity to memory if it is shallow cycled a few times between 85-100% for example. Lead acid, on the other hand, keep it full and never use more than half of the capacity.

My electric toothbrush, though, has a design life of a year or two with its NiCD battery, which I’ve stretched out to a decade by not following their recommendation of leaving it charging on the base when not in use. I run it until it stops, and then charge it. Yes, it has replaceable heads.

 

[JoeS]

It's extremely harmful to store LiIon in deep discharged state (they occasionally ballon or even catch fire) or keep them float charged - they seem to prefer being stored at about 75-80%...

stoatwblrm, you are correct that we should avoid storing our lithium traction battery at either SoC extreme; however, I believe the recommended storage level for most Lithium chemistries is actually closer to 40%SoC (for example, ref: https://batteryuniversity.com/article/bu-702-how-to-store-batteries). This topic for EV primary batteries has been discussed extensively on just about every EV forum (including this one), so perhaps we should keep this thread focused on our i-MiEV 12v lead-acid battery. Thank you.

 

[barrylevine]

Both of my i-MiEVs have this quirk where if the car is locked, and I go to retrieve something out of it with the simple process of unlock doors with key fob, open a door, close it, and lock the car with the fob, I'll have a dead 12 volt battery within a week. If I unlock the doors with the fob, open a door, start the car, shut it off, close the door, and lock it with the fob, the car can sit for a month+ and be able to start without a jump. Whatever drains the battery, having the car fully cycled before locking the doors lets it power down successfully.

I'm in the process of dealing with a what was a dead 12V battery, and I thought it a good idea to check in the forum to learn a few things. I've a 2016 i-MiEV, and have always locked the doors with the fob. Mostly though, not going back to open the car and lock it with the fob again.
Recently, not driving much at all, but occasionally retrieving items from the car and relocking with the fob... and maybe with the i-MiEV sitting undriven for a week or more at a time (and with the original 5-year-old battery as well), this quirk revealed itself. The battery seems to take a charge now though, reads 12.6V on my multimeter.
So, Question 1: Is there any more info on this battery-draining quirk?
Question 2: I've seen some posts here about the relatively easy and longer life i-MiEV 12V batteries have. In my ICE cars, 5 years was pretty much the limit (likely imposed by the need to start an ICE in Boston winter weather). Do the i-MiEV's tend to do better?

 

[Lic]

I installed lithium-titanate battery for 12v system. This battery could be charged up to 16v. I am wondering if it possible to charge it up to 15v or even 16v when car is charging main battery and charge it in regular way when car is in ready. I see 2 ways how to do it. First - connect 240v/12v to 16v power supply to charging inlet and to 12v battery. When I will charge car - lithium -titanate will charge too. Second - find out if there is line which measure voltage in 12v line and make car think that voltage of 12v is low (may be drop voltage by 2 diodes) and bypass those diodes when car is in ready. What do you think?

 

[pbui19]

I installed lithium-titanate battery for 12v system. This battery could be charged up to 16v. I am wondering if it possible to charge it up to 15v or even 16v when car is charging main battery and charge it in regular way when car is in ready. I see 2 ways how to do it. First - connect 240v/12v to 16v power supply to charging inlet and to 12v battery. When I will charge car - lithium -titanate will charge too. Second - find out if there is line which measure voltage in 12v line and make car think that voltage of 12v is low (may be drop voltage by 2 diodes) and bypass those diodes when car is in ready. What do you think?

had to look up titanate battery. Please share model, price and where it was purchased. What's the goal to get higher than 14.1 charging voltage ? more capacity ?

 

[pbui19]

So, Question 1: Is there any more info on this battery-draining quirk?
Question 2: I've seen some posts here about the relatively easy and longer life i-MiEV 12V batteries have. In my ICE cars, 5 years was pretty much the limit (likely imposed by the need to start an ICE in Boston winter weather). Do the i-MiEV's tend to do better?

we learned in the early days with our 2014 to always lock with pushing the lock button or turning the mechanical key, the 12-v was drained several occasion locking with the fob. So it's a habit now, I thought it had something to do with arming the alarm system.

I have one of those dash-board solar panel charging the iMiev, but then have to be sure to park in the sun. The 12v in the i definitely has an easier life: no cranking, no high temperature. But being lead, it still die. Replaced mine, once so far, with a cheapy HarborFreight SLA (~$60 ?)

 

[barrylevine]

Thanks for your reply. I've been getting in the habit now of using the door lock button. But I hadn't considered using the door key. However, being a bit absent minded at times, I think now it would be better to habitually use the key (then there's no chance of inadvertently locking them in the car!)
Going to wait on the battery - new ones are rather pricey, and it seems to be holding charge quite well, reading 12.5V if sitting for a few days off the car charger. (But wait until the zero degree mornings!) Harbor Freight doesn't seem to be carrying anything that looks like a possible cheapo replacement these days. I'm keeping an eye open also for a low-priced Miata battery, since those will fit, albeit with lower height.

 

[Lic]

I installed lithium-titanate battery for 12v system. This battery could be charged up to 16v. I am wondering if it possible to charge it up to 15v or even 16v when car is charging main battery and charge it in regular way when car is in ready. I see 2 ways how to do it. First - connect 240v/12v to 16v power supply to charging inlet and to 12v battery. When I will charge car - lithium -titanate will charge too. Second - find out if there is line which measure voltage in 12v line and make car think that voltage of 12v is low (may be drop voltage by 2 diodes) and bypass those diodes when car is in ready. What do you think?

had to look up titanate battery. Please share model, price and where it was purchased. What's the goal to get higher than 14.1 charging voltage ? more capacity ?

I used toshiba scib battery modules from honda fit electric. I bought it used from ebay. Goal is to save main battery energy. If you will have 15v in 12v system dc-dc will not feed 12v system at all.

 

[PV1]

So, Question 1: Is there any more info on this battery-draining quirk?
Question 2: I've seen some posts here about the relatively easy and longer life i-MiEV 12V batteries have. In my ICE cars, 5 years was pretty much the limit (likely imposed by the need to start an ICE in Boston winter weather). Do the i-MiEV's tend to do better?

Not that i have. Actually, after replacing the 12 volt batteries in both cars, I haven't really seen this return. Both cars have been sitting a lot lately and both started right up when needed.

I forget how long mine lasted, but I got at least 7 years out of them. My old Cavalier battery lasted 10 years.

 

[JoeS]

...I forget how long mine lasted, but I got at least 7 years out of them. My old Cavalier battery lasted 10 years.

The problem nowadays for all cars is that they have various car systems drawing a miniscule amount of current from the 12v battery, gradually depleting it. With our i-MiEVs it's the alarm, doorlocks, and Remote, to name a few. It's this repetitive down-and-up cycling that affects the life of the lead-acid battery. The older they get and the longer we go between drives, the more liable we are to experience a hiccup. Pity that our i-MiEV doesn't monitor the 12v battery and automatically wake up to activate the dc-dc when it goes low.

That's still not bad, as, when parked, my old Tesla draws anywhere between 0.4A and 1.7A from the 12v battery depending on the display settings, and the newer Teslas with Sentry mode and cameras are far worse - the saving grace being that the car monitors the 12v battery voltage and wakes up the big battery's dc-dc to recharge that 12v battery whenever it drop to ~12.2v. That's why I always attach a float charger (actually, a small Meanwell power supply set to the AGM manufacturer's recommended float of 13.7vdc) to the Tesla's 12v battery even if I'm not using it for only a day. My Tesla 12v is now going on six years... (knock on wood!), significantly better than average for Teslas.

 

[Mitsi]

lighter socket has fuse (around 10Amps) so can't be used to charge or boost battery. But I think you can use it to measure voltage in 12v line.

How about limiting the current to <10A ?
How would I do that? Resistor?