Lithium Battery

Lithium are very expensive, and they are very light-do you need the weight saving? If they get in trouble Lithium will burn of their own accord, this makes them a liability. AGM seems to be an improved flooded type. But still expensive. Hope this helps.

The latest versions will not allow themselves to discharge too low, those that have individual cell management are still quite expensive but are less fussy on the charge needed as they will control what is applied to each cell. Some are now aviation approved like those from Earthx and Airbatt which do sizes that fit motorcycles.  

Back in 2015 i had the voltage rectifier/regulator on my Mk3 fail when out on a ride, failed by outputting AC at quite high voltage into the system, killing the EI and heating the battery (AGM sealed type), so much so, that i removed it sharpish at the roadside while waiting for recovery. After the battery had cooled down, it looked like the insides had been sucked out, it was quite deformed. It didn't leak though. 

I was impressed by the containment of the AGM battery that got knackered so it was the same type i refitted to the bike when i had sorted a new rectifier/reg.

As Al says they (lithium) are expensive

I fully understand the benefits of a lithium battery on e-start bikes. Great cranking power versus weight.

But is there any benefit on kickstart bikes except weight? They usually have less Amperehours.

Lithium are the new “have to have” for campervans due to their light weight, fast charging and deep discharge rates. However they do need specific chargers as they are really fussy about charging and even with a specific charger they will not charge below 0 degrees. They also cost significantly more than an equivalent AGM or Gel battery, but will deliver significantly more charge cycles. Which is much the same reason why they are used in eBikes, power tools, etc.  For an old Norton, I am not sure, especially as you will not be using it as a deep discharge battery along with the low temperature charging, (if you keep your bike in a garage over winter when the temp could get close to or below freezing).

I have a Motobat AGM on my Dommi, which from Tanya was not a lot more expensive than a standard Yuasa flooded battery. It’s brilliant, holding 12.8v for months and it is pretty much maintenance free. In fact with the rubbish weather in Northern England last winter I never got the Dommi out and after 4 months with no charge it still had 12.8v, so no issues kicking the bike into life, even with a Mk 1 Boyer... 

It is AGM that gets my vote for your Commando. 

I have old type acid batteries on  3 bikes ,from  approx 10 years old , they all work for kickstart bikes .As long as they are not allowed to go flat or dry they give no trouble. The acid batteries on my Transit worked well for 19 years untill I scrapped the van. Campervan batteries are going to be run out flat sooner or later and need to be able to cope.