12 Volt Lead Acid Battery Replacement

[VitaminJ]

Well I got struck by the 12v curse today, Leaf is nonresponsive. I tried jumping it and then switching on the windshield wipers, thinking that triggers the 14.4v DC converter to kick on, but nothing happened. Charging the 12v battery on the bench at the moment, probably going to replace it with a LiFePO. I have about 30 suitable Lipo RC batteries, but the voltage doesn't quite match up, too high for a 3S and too low for a 4S.

[LeftieBiker]

Just keep in mind that the issue isn't high current drains, but problematic charging behavior by the car. Even a Lithium battery will get low eventually and have to be recharged, unless the 'capacity theory', which says that higher capacity accessory batteries will be charged adequately by the car, is correct. In either case, a better SLA battery and a maintainer would be much cheaper, and potentially more reliable.

[IssacZachary]

Anyone putting voltmeters and ammeters on their Leaves? (I'm still not sure if the correct term is Leaves or Leafs.) That would be the way to see if it's the Leaf's charging system or the battery that's goofy.

The most fool proof energy storage would be an ultra capacitor battery with balancers. There are guys doing this on their ICE vehicles and turning out just fine. But it wouldn't hold a lot of charge and could go dead quicker than even a lead acid battery if there were too much drain. At least going dead wouldn't hurt it at all. And yes, the insane amperage that an ultra capacitor can put out isn't necessary in a BEV, but it's the longevity that catches my attention at millions of cycles instead of a few hundred (lead acid) or thousand (lithium).

[LeftieBiker]

The most fool proof energy storage would be an ultra capacitor battery with balancers.

It's the BMS that makes lithium packs less reliable. Perfectly good sets of cells get ruined by a malfunctioning BMS. I wouldn't want to test that with ultra-capacitors...

"LEAF" is actually an acronym made up by Nissan, so the plural is "Leafs." As for voltmeters, the problem with installing one is that they are all made in China. Some are accurate, others wildly not. If you get one that tests good, it could at least provide a benchmark.

[IssacZachary]

It's the BMS that makes lithium packs less reliable. Perfectly good sets of cells get ruined by a malfunctioning BMS. I wouldn't want to test that with ultra-capacitors...

Thanks! Leafs it is!

Now that you mention is, my brother-in-law, who's always wanted to build his own BEV and has a degree in electrical engineering, told me once that it would be much better to bottom balance lithium cells and then manually check them with a good digital multi-meter once in a while than to add a top balancing BMS. The same may be true with the ultra capacitors.

[LeftieBiker]

I have a Vectrix VX-1 maxiscooter that was converted by the previous, original owner from the horrible OEM NiMH pack that sank the company, to 18 pairs of Leaf cells. It has no BMS. As long as the cells check out ok in the Spring (there are measuring/balancing leads) voltage-wise, I shouldn't have to worry about a failed BMS, or anything else but heat and low voltage, all season.

[Stanton]

If you really want to "get the lead out" for the 12v battery, why don't you just replace it with a LiFePO4 made for that purpose (BMS included)? There's a whole thread on it http://www.mynissanleaf.com/viewtopic.php?f=37&t=11999

[VitaminJ]

The Leaf already has a voltmeter on the 12v battery, you can see it in Leaf Spy.

[LeftieBiker]

The Leaf already has a voltmeter on the 12v battery, you can see it in Leaf Spy.

That's true. It would be convenient, though, to have one that can be read instantly, without having to connect LeafSpy.

[joeriv]

For about $12 you can get a battery analyzer that plugs into the 12 volt accessory port. I bought the Innova 3721 on Amazon and it works great.