12 Volt Lead Acid Battery Replacement

[Stanton]

Quick calculations: you could store 4 in a row (parallel), and 4 in a line (series) in that enclosure, with room for the BMS. Using 16 20Ah cells you could store about 1kwh (16 cells * 20Ah * 3.2v = 1024kwh), or 320Ah. That is almost a 10x increase over the Lead Acid hazard. I run many accessories off of my 12v system so I see many benefits. Though the cost would be almost $500 for all needed parts and cells.

You could buy a good 12v Lithium "drop in" replacement battery (with a built-in BMS) for that kind of money. Not to mention that capacity is way overkill: I have a 20 Ahr 12v LiFePO4 battery in my car and have never had a "dead" 12v battery (and I run a lot of ACC).

[chivalryx]

Wanted to thank all the posters for all the tips and info. I took the plunge and swapped out my lead acid for a 20ah prismatic LiFeMnPO4 battery. Should meet my needs. I found the easiest swap was using:

4 gauge battery cables like these:
http://www.canadiantire.ca/en/pdp/motom ... p.html#srp

Battery with case like one of these (option for BMS if you don't want to check it periodically):
http://www.batteryspace.com/lifepo4-pri ... d-dgr.aspx

Water resistant tape to cover any gaps or holes in the case since I'm a little paranoid.

Just screw one end of the cable onto the LiFePO4 battery terminals (a round metal washer helps hold it tight), and screw the other end of the cable between the car's battery post clamps (threaded the screw through the cable terminal end), and done! Took like 10 minutes.

My only difficulty now is how to keep the battery in place since it's so small. For now some foam inserts work, but it's not optimal. Any tips from early adopters would be appreciated!

Chiv.

[Stanton]

My only difficulty now is how to keep the battery in place since it's so small. For now some foam inserts work, but it's not optimal. Any tips from early adopters would be appreciated!

I simply put a block of wood under my case (which I turned on it's side) so I could use the original clamp/tray. I was able to screw it down tight enough to where I've had no issues for > 2 years now.
Congrats on "getting the lead out"!

[chivalryx]

My only difficulty now is how to keep the battery in place since it's so small. For now some foam inserts work, but it's not optimal. Any tips from early adopters would be appreciated!

I simply put a block of wood under my case (which I turned on it's side) so I could use the original clamp/tray. I was able to screw it down tight enough to where I've had no issues for > 2 years now.
Congrats on "getting the lead out"!

Thanks Stanton. Will give it a try!

[Kristis]

Does anyone know the dimensions of original battery?

[Stanton]

Does anyone know the dimensions of original battery?

From the datasheet for the "stock" 12v battery:

9 3/8 x 5 1/16 x 8 15/16 (inches)
19.8 lbs and 45 Ahr

Note: I replaced mine with a 20 Ahr LiFePO4 at about half the weight (and smaller to the point where I turned it on it's side).

[IssacZachary]

Any suggestions for a good battery replacement for Colorado high mountains where -40*F/-40*C temperatures can occur?

I was thinking the Winston 90ah battery. It's rated to -45*C charge and discharge.

Or a capacitor pack made from 6 3,000F ultra capacitors made by Maxwell's Boostcap. Those are rated to -40*F/-40*C.

[LeftieBiker]

Keep in mind that the power demands on the 12 volt battery are modest. It just has to be tolerant of deeper cycles (but with lower current demands) than typical starting batteries are, and of being chronically undercharged. I suggest you get a mid-priced marine-type compromise battery, and a Battery Tender or Battery Tender JR, if you have a place to plug one in. My OEM battery is still original, and after 4+ years, with one near-dead episode after the first year, it's still working because of the $30 Battery Tender JR. I use.

[IssacZachary]

Ah! Thanks! I wonder if I ought to have it checked from time to time and can it good. Yes, a battery tender sounds like a great idea. Also a Kats battery warmer. Maybe a flexible solar panel and charging circuit. I do have the little solar panel on the top of the rear hatch.

[LeftieBiker]

That little solar panel may actually help...if you can park the car so the panel is in direct sun for 5+ hours a day. I suggest you check the resting voltage, by leaving the hood unlatched a couple of hours (to avoid having to open a car door), then putting a voltmeter on the 12 volt battery terminals. 12.6 volts or more and you're fine. 12.5 volts and the situation is marginal. below 12.5 volts and the battery tender is a good idea. I used the hardwire connection that came with the tender, but made it longer with a two wire 120 volt appliance cord, IIRC. I then connected it to the positive battery terminal, a bolt on the inverter stack for ground (the assembly that looks like a valve cover, specifically), and ran it into the charging port compartment, through a small hole I drilled. Now I plug in whenever I think the car will be plugged in longer than it will be charging, which in my case is most times.