Modern Vespa

My 2019 Primavera's battery has died over the winter. I could replace it with an AGM, but I'm thinking this may be a good time for a lithium battery. Any comments, or recommendations for a good lithium battery? I don't want to pick a battery at random from Amazon and have it be a piece of junk.

Lithium works fine. I'm using Noco brand in two of my bikes (HD and MP3 500) and works very well, in other bike I have a Antigravity, is very good but the price point is so high.

Noco brand looks good if I can find one in the US. Autozone possibly has them. Do you know if they come with spacers to fit in my Primavera (original battery was YTX7L-BS)?

I purchase my Nocos in amazon

From what I see, if is Noco is a NLP5 (based in your comment about the actual one YTX7L-BS), but you can confirm in the Noco web page https://no.co/lithium/powersport

And yes, it come with a group of modular spacers.

Note: I have no commercial relationship or business interest in Noco, I am just another user.

You can get a Mighty Max LiFePO4 (as sold by Home Depot and many others) for ~$55, e.g. https://www.mightymaxbattery.com/shop/lifepo4/ytx7l-bs-lithium-battery-replaces-honda-250-cb250-nighthawk-1991-2009/

I ordered and installed the Noco NLP5 battery yesterday. It went in easily enough, though the ring terminals on the scooter had to be drilled for slightly larger screws on the new battery (as was mentioned in some of the reviews for the battery). The scooter started with the first push of the start button. I also bought a Noco Genius 1 charger with the battery. One thing I don't like about the charger is that it uses a connector different from the SAE connectors on my other charger accessories.

Battery charger charging profiles are different between LFP and LA batteries, so different connectors are a good idea to prevent you causing damage to your other Lead Acid batteries. The LFP battery is actually OK with a standard charger, despite some FUD on the interwebs - but not the other way round.

This charger is supposed to work with any battery. It has a switch to select wet cell, AGM, or lithium.

Very good.

I use the Genius1, Genius2 and Genius5, depending of my rush or if I have more that 1 bike charging at same time, works fine for regular and LFP batteries, and Noco have a "adapter" from the proprietary connector to SAE one (I use it as I have the SAE installation in place before in all bikes).
https://www.amazon.com/dp/B005DUMADC?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_5

Having seen the winter scenery in Minnesota , albeit through the medium of Amazons Fargo , one thing to consider with Lithium batteries is they don't like cold , so probably worth removing it in the very cold months.

The cranking power of lithium's is legendary, plus the size and weight saving is significant.

My issues with lithium batteries in scooters is that they solve problems I don't have, and introduce complexities I don't need, at a higher cost.

I get 3+ years out of cheap-ish Amazon batteries that typically degrade gradually and give plenty of opportunity for leisurely replacement, a lithium jumper pack easily solves the worst-case dead-battery scenario, and that's completely fine.

What complexities? And the cost is now very similar to AGM.

A standard charger will work with a LFP battery. Very few riders venture out in temperatures lower than -20C (~0F).

These and other sites suggest special "wake up sequences" begin in the mid-40°Fs.

https://www.batterystuff.com/kb/articles/battery-articles/lifepo4-lithium-iron-powersport-batteries-cold-weather-performance.html

https://www.fullspectrumpower.com/blogs/full-spectrum-news/10662405-lithium-batteries-in-cold-weather

Anecdotally, not clear if the set of chargers and tenders I have now will work well with them.

And they're more than twice the price ($80 vs $35). Will they last 5-7 years when the regular ones last 2-3? Do I want to spend up now to find out later? Not really.

More power to others who feel differently though.

I'm going to echo the other comment, what use case does lithium help with? AGM starts the scooter fine, and lithium batteries don't like the cold and can be a fire risk. The AGM are cheap and fairly reliable if you tend them in the offseason.

LFP batteries are NOT a fire risk. You're thinking of the NMC batteries that used to be used in cars (and still often are in the US). Those really are a fire risk!

Here's a good run-down:

You're partially right. LFPs are much LESS of a fire risk, but they are more risky than lead acid. LFPs are much more thermally stable and combustibility is much lower than NMC.

Overcharging, short circuits, physical damage, etc are still fire risks. I'd says poor build quality of the battery or a person overcharging are the biggest risks. I work in medical devices where we design lithum charging circuits for LFPs, so I have some insight here.

So, yeah, much lower if you can get a LFP and I would definately avoid the NMC (agree with you there). But lead acid is hard to beat if all you're trying to do is start a scooter engine for the price.