Well, some asked for it, so I'm doing it--Lithium Drop in replacement for Aux Battery

[glhs272]

Ive fitted a Shorai Lithium iron to my Roadster and it seems to be fine so far. 12v battery service required, can it be replaced with lithium? | Speak EV - Electric Car Forums

How long have you had it in place? I would like to see something better than the lead acid setup currently in my Model S. I could care less about a few pounds. I just don't want to have to replace the 12Volt battery every 18-24 months. Would like to see 10+ years of life out it.

 

[FlasherZ]

I saw some pretty crazy voltages when I was monitoring the 12V post - 15.1V in the case of my car when I looked at it about 2 years ago... I'd be a bit concerned with a replacement, unless it were intelligent enough to handle a wide range of voltage. Typical voltage of a normal 12V alternator is about 13.8V or so.

 

[dhanson865]

Well, After digging through my Frunk, replacing the 12v battery with the lithium is not going to be dooable, as how the MS manages that battery.
Having one as a spare is dooable.

I have been monitoring my 12v battery, So far mine has been solid, however, I have been monitoring the voltage of that battery for the last month while driving.
Now, fully charged 12v lead acid battery should read abotu 12.8-13v. The voltage of the battery while the vehicle is in use, has been between 13.6-14.9v. That is VERY high for a AGM or Gel Cell battery, and can cause pre-mature failure.

Now, I understand their is power being taken from the battery, and I know I cannot tell how many amps are being transferred to the battery so I cannot come to a full conclusion. I have tested the voltages using the terminals behind the nose cone, and am getting the same voltages when the car is parked and idle. That might be part of the battery failure problem as well, though, without more information, of which I cannot easially get, I cannot make a definitive conclusion.

13.5 volts is what a charger puts out to maintain an already fully charged 12v battery
14.9 volts is what the charger puts out to recharge a partially chaged 12v battery

neither one of those or any range in between is the actual voltage of the 12v battery. Disconnect the 12v from the car and check the voltage with a meter and you'll get something below 13v on any car battery that wasn't just sitting on a charger for 48 hours.

as a comparison this is what I measured on the last AGM battery I bought

voltage recap

out of box 12.52
after 18 hours on charger 12.94
after connection to car but car off 12.72 (SKS load)

If you see anything above 13.2 volts on an AGM battery you've got it hooked up to a system that is trying to charge it or your meter is in need of calibration.

 

[islandbayy]

Since someone resurrected this thread, thought I would just chime in. I did NOT switch to a Lithium flavor of battery for the 12v. After learning much more, and some own "home" experiments etc...

One of the MAJOR factors in this decision, is due to charging of the Lithium battery. I'm not going to go into major details in this thread as it's been talked about to death already, however, Lithium batteries have a "happy place" in terms of Temps they like to be kept at, especially during charging.
They must be above freezing (33*F, 1*C or higher) or the lithium cells will internally electroplate resulting in permanent capacity loss during charging. And they like to be kept below 113*F. Charging or having high state of charge at or above this starts to exponentially increase rate of degradation.
While a Lithium drop in in a more, southern or temperate climate might do "Fine" like some roadster owners are experiencing, here in Wisconsin, where we are below freezing for a nice portion of the year, let alone those further north of us..... Would require a 12v battery heater. This would consume battery power, needing the contactors to be closed from the HV pack to charge the Lithium battery more, wasting much needed winter range. I decided against this.

As for those using Shorai batteries , that are anything other then the most recent, I warn much caution. They had a MASSIVE recall on the batteries due to faults causing meltdowns. No fires due to the chemistry used, however, a meltdown can get fairly ugly in a confined space such as, in a car.

 

[JRP3]

Lithium Titanate chemistry is really the most appropriate lithium chemistry for this application. Good to at least -30C, 10,000 cycle life, but good luck finding them. Only Altairnano, (NanoSafe), and Toshiba, (SCib), make them, (that I know of), and I don't know if they sell them to individuals. Honda used the Toshiba SCiB in their FitEV, which they only leased, so even a wrecked one may not exist in the wild. The Mitsubishi iMiev was supposed to use them initially but that seems to have changed at some point. They operate at lower voltages so you'd need 6 cells if you were making a 12V battery. I've been trying to find some but no luck so far.

The voltage of the battery while the vehicle is in use, has been between 13.6-14.9v. That is VERY high for a AGM or Gel Cell battery, and can cause pre-mature failure.

Gel and AGM are different, 14.9 is too high for Gel but not for AGM during the bulk charging phase.
http://www.optimabatteries.com/en-us/support/battery-care/charging/

 

[JRP3]

One way to possibly use LiFePO4 would be to build an insulated battery box and use a 12V battery heating pad. That would increase your vampire load in very cold weather but maybe not by too much, especially if you park in a garage at night. One concern is that 14.8+ volts is a bit high for LiFePO4, 3.7V per cell, so it might be worth using a resistor to dump some charge. Could be part of the warming circuit in cold weather.

I don't think heat is much of a concern, I know people with 5+ year old LiFePO4 packs in hot climates that have shown no excessive degradation.

 

[JRP3]

Small format LTO cells: http://www.batteryspace.com/Lithium-Titanate-Battery.aspx
Larger format LTO cells may be available soon? http://www.ev-power.eu/LTO-Cells/ http://gwl-power.tumblr.com/tagged/LTO

 

[Perrin21]

How long have you had it in place? I would like to see something better than the lead acid setup currently in my Model S. I could care less about a few pounds. I just don't want to have to replace the 12Volt battery every 18-24 months. Would like to see 10+ years of life out it.

Just 1 day so far but i expect it will be fine. It gets very little usage on a 2.5 roadster.

- - - Updated - - -

Since someone resurrected this thread, thought I would just chime in. I did NOT switch to a Lithium flavor of battery for the 12v. After learning much more, and some own "home" experiments etc...

One of the MAJOR factors in this decision, is due to charging of the Lithium battery. I'm not going to go into major details in this thread as it's been talked about to death already, however, Lithium batteries have a "happy place" in terms of Temps they like to be kept at, especially during charging.
They must be above freezing (33*F, 1*C or higher) or the lithium cells will internally electroplate resulting in permanent capacity loss during charging. And they like to be kept below 113*F. Charging or having high state of charge at or above this starts to exponentially increase rate of degradation.
While a Lithium drop in in a more, southern or temperate climate might do "Fine" like some roadster owners are experiencing, here in Wisconsin, where we are below freezing for a nice portion of the year, let alone those further north of us..... Would require a 12v battery heater. This would consume battery power, needing the contactors to be closed from the HV pack to charge the Lithium battery more, wasting much needed winter range. I decided against this.

As for those using Shorai batteries , that are anything other then the most recent, I warn much caution. They had a MASSIVE recall on the batteries due to faults causing meltdowns. No fires due to the chemistry used, however, a meltdown can get fairly ugly in a confined space such as, in a car.

Please elaborate on this "massive Recall" I haven't found any info on a recall. Just 2 fires caused by shorting the terminals.

 

[islandbayy]

Just 1 day so far but i expect it will be fine. It gets very little usage on a 2.5 roadster.

- - - Updated - - -



Please elaborate on this "massive Recall" I haven't found any info on a recall. Just 2 fires caused by shorting the terminals.

for starters, there major retail outlet was batteries plus. Shorai set my shop (as we had warranty registrations) and my home (where I had another warranty registration set to) with recall notices to take back the batteries ASAP to batteries plus stores where we would be refunded with receipt. with a week of that notice, every batteries plus store had every shorai battery pulled from shelves and on the way back to shorai. that one was just the major one I remember. my friend that had one in his harley, that purchased elsewhere, shorai bought his back too. though directly, not as a return to the store. they worked good, but we did have early EOL on 3 of the ones we had bought (Customs and scooter shop and we put them in cycles and scooters).