Hi Folks,
I've been doing some 12V battery research.
Safety first:
Current Lithium batteries really do not do well when charged below freezing.
Imagine it is 5 degrees below freezing. With our I-MiEVs,
the 12V battery turns on some systems, and brings the main battery online.
Pretty quickly circuitry tells the main battery to send some
electrons to the high-voltage-to-12V charger.
With a Lithium 12V battery this is bad, and in fact, one below-freezing charging session
can damage the battery to the point that it is not safe.
FLA and AGM batteries are fine with being charged at below freezing temps.
There are heating options that make it possible to use a Lithium starting battery:
A) Use a continuous parasitic trickle charge to keep the battery warm.
I read that some Teslas do this, and it can be a significant drain on the battery.
OR
B) Use a 12V or 120V heat mat/wrap and insulation to warm the battery before starting.
And convince my wife that she has to start warming the battery thirty minutes
before she can go - not gonna happen.
C) For one company to get UL listing, they have a circuit in the battery
that turns it off below freezing. That's going to save the battery, but
you won't be able to start the car.
NOTE:
Lithium-Titanate batteries are almost ready for prime time;
one suppler said they would have them this year.
These batteries are good down to at least -20F, and possibly lower.
They have a higher cycle life and some other benefits compared to
current Lithium batteries.
The Factory I-MiEV battery tray is 7.25" wide x 5.25" deep, with a rim about .25" high.
It has two protrusions underneath that locate it to the frame.
The tray would be easy to modify for different battery sizes.
Overall there's room for about an 8" wide x 6.5" deep battery.
Note that some 151R batteries are bigger than others.
When buying an alternative battery:
) Make sure you get the positive terminal on the right side.
) Check the post height of a battery, relative to the top. Some batteries
have posts below the top of the battery, and the I-MiEV factory positive terminal,
with all the extra stuff on it, won't fit without an extender.
) Check overall battery height, with posts. Shim as needed
underneath, and maybe over the top,
so when the battery is installed the post height is close to the factory height.
So for now, back to AGM.
Some better options:
) Odyysey PC680, $130, 15.4#, 24 reserve minutes, USA, 3yr warranty
) XS Power S680 is $140, 15.4#. 28 reserve minutes. China. 3yr
) Braille B2317RP is $193, 17#, 45 reserve minutes. USA, 1yr
) Braille B3121 is $230, 21#, 75 reserve minutes. USA, 1yr
There are many other AGM batteries out there. If you find a great one, please post!
The Brailles are pretty high spec.
I think the short warranty is because they are marketed to the racing world.
The B2317RP looks like it would be adequate.
The B3121 stores more energy per dollar and might last longer.
If you just want an inexpensive flooded lead acid battery,
the Bosch 151R is about $105, 19#, has a 3 year warranty and
is listed as maintenance free.
I like batteries that last a really long time -
fewer battery issues, better for the environment.
For now, the 21# Braille looks like a good choice.
Actually, I think our 12V battery is doing pretty well right now;
am guessing it sat on a car lot for a long time and
has been rejuvenated a bit by daily use.
Thanks and good health, Weogo
