For the back story I haven't been riding for a few years and haven't done a resto for even longer.  So I am getting back into the loop, I hope.  And hoping to enjoy a lot of green lane rides and trail rides in the years ahead
If this topic has been well covered then please delete this post.  If it is covered elsewhere perhaps I can be oriented in that direction, but my searches appeared to show replies to various 'builds' here and there and didn't supply the answers I was seeking, but again perhaps I missed something.

- so is there any major disadvantage that outweighs the advantages of using a 6v lithium battery in the these older charging systems or is it more beneficial to use a gel / AGM Pb battery.  Eventually I would need to acquire a 6v lithium charger and maybe a tender also
thanks for all your incredible input (this forum is truly amazing!)

I wouldn't even attempt to charge one of the most unstable and dangerous types of batteries (lithium) with the crude half-wave rectification charging system that more or less relies on a wet cell battery for a crude voltage regulator. 

MarkT cheers, I read in some of your previous posts about the 'unclean' voltage produced by these early magnetos, and you do hear of some of the LiPo batteries getting hot and puffing or worse, so for now, I'll head for the true and tested

That's enlightened me Mark, haha. Thanks.
I'll keep that in mind.
Things i didn't know or was too afraid to ask.
Is that those button batteries that catch fire & keep burning--till ya house is burnt down.
Got me worried now as to what i have around here with one.
Google says cell phones--which are a flat shape. Now i'm worried lol.
Have 4 AA recharbables on charge io forgot for a month--now ya made me look.
Think they are just a stack of button batteries.
Maybe i'll destroy an old one just to look.
I was replacing batteries in a kids toy ages ago & had trouble getting the fat button batteries out because they'd gone all swollen & forced the end out which worried me.
Weren't rechargable in that. Or am i on the wrong track--wrong type.

Laptops and cell phones and many other devices have lithium ion batteries... including most modern Electric Vehicles.  They are lightweight batteries and usually clearly marked.  Consumer Electronic devices like phones and computers have fairly robust charging protection circuitry and are generally pretty safe.

Vehicles like electric bicycles and scooters...  and sometimes cars...  with lithium ion batteries have a far worse safety record.  Do a Google search.

Combining water and lithium results in a violent reaction (fire and/or explosion) so trying to put out a lithium fire with water makes it worse.  Fire departments generally do not have the equipment to fight lithium fires.

Many years ago I saw a small prototype RC car lithium ion battery pack catch fire during charging at a race.  It burned through a 2 inch thick wooden picnic table top and did significant damage to the concrete slab under the table before it burned out.

 

A friend of Gr8auntiepat's is a loss adjuster for an insurance company and won't leave anything charging, or dishwasher, washing machine etc on whilst she is out of the house...........! 

My brother in law is the same way about not leaving anything unattended on a charger and he won't leave anything but the refrigerator on when they aren't home.   He charges things like their lithium battery e-bikes outside well away from the house. 

LiPo4 - safe
Not Li-ion - not safe

also button bats are all Li - charge them and they make a good blasting cap for dynamite

3 completely diff. designs

cliff

p.s. adding another diode or 2 to the battery kills .7 volts each to limit charge power.
I use 1/2 of a full wave for this on my LiPo4

Lithium-iron phosphate batteries are "safer"...  not completely safe.  But then what is completely safe?  Many EV batteries use that technology.  Overcharging, battery temperatures over 140 degrees... which can happen where I live very quickly parking the bike in the sun in the summer...  freezing temps...  and physical damage or a short circuit can result in catastrophic damage to the battery and whatever is near it.  Vehicles like Teslas have battery cooling systems and robust charge filters/sensors/controllers.

And if a fire does start somehow you still have the problem of not being able to use water to fight it. 

 

Lithium batteries are quite energetic if they have a problem. I fell off a log crossing into a stream and phone eventually died. Figured I'd drill a hole into it like you do hard drives to make it unusable, but was glad I put it on a cinderblock in the middle of my driveway. Smoke poured out furiously, very toxic smelling and the flames shot into the cavity in the cinderblock, scorching it and the driveway. Hard to believe you can get such a reaction from a small device. Don't think I'll do that again, lol.