Hi Mike. All "lithium" cells these daze are "lithium-ion" as compared to lithium metal, lithium-air, etc.

Lithium-ion cells may have a liquid lithium-salt electrolyte or a solid polymer composite separator (termed Lithium-Poly or LiPo etc.) LiPo's are attractive because of high energy density - light weight packs - and super high charge/discharge rates (high power density) but LiPo tech is tricky stuff and when things go wrong they can go really wrong. LiPos are in common use now in RC toys.

Most of the world runs on lithium-ion cells with an electrolyte. The anode is usually carbon so all these different flavours of "lithium" batteries come down to the cathode composition. Early daze might have been lithium cobalt oxide (LiCoO2) but these cells have been largely abandoned as they have a nasty propensity for "thermal runaway" at fairly low temps... as overheated cells break down they create their own oxygen for a self-feeding fire...

So Lithium-manganese came into common use... and then LiFePO4 with similar or better safety characteristics to manganese but longer cycle life. AFAIK most commercial ebike packs these daze are LiMn (including your A2B pack), but there are new varients of Mn and Fe coming into use too.

Stuff like manganese nickel oxide (LMN) and manganese cobalt etc combos like Li(Ni-Mn-Co)02 ... speculation that LiFePO4 will soon be eclipsed by LiMnFePO4... there's a lot of research going on into all these combinations of cathode materials and electrolytes with different results affecting energy and power densities and cold/hot temp performance and cost.

And ya have your nano-phosphates too, like A123 and Altair and Valence...

So I'll guess that most 2012 commercially available bikes will still be LiMn, some LiFePO4, and a few starting to promote LMN etc

Lock

Mike,

If you are riding the A2B Metro the integrated battery in the down tube is manufactured by Sanyo and the secondary battery that mounts on the rear is manufactured by Samsung. The Velociti battery is also made by Samsung (no battery in the down tube).

Both battery types are Lithium Manganese. Both Scooteretti and Ultra Motor recommend recharging your batteries every 30 days or so. In the case of the A2B batteries you need to keep in mind that your BMS microprocessor is constantly on whether you are using the bike or not. Although power consumption is minimal, if kept uncharged for long periods of time it will completely drain the battery causing permanent damage.

Before putting the battery in storage or after 10 recharges it is recommended to leave the charger on longer than normal. On the A2B's Ultra Motor recommends 12 hours and on the Scooteretti's we recommend 12-14hrs every 12 recharges and before putting into storage, then recharging every 30 days if not used until the light on your supplier charger turns green (a few hrs).

hope this helps,

William

Thanks for info, Lock and William. That helps a lot. One more question William. You mention that the "BMS" microprocessor (I don't know what that is) is constantly on, whether I'm using the bike or not, but I'm wondering if that affects the rear battery as well on my Metro, since that battery appears to have it's own off-on switch?

Hi Mike,

Indeed, if you have the optional secondary battery there is a BMS located in that pack as well which is drawing a slight amount of power. So you're definitely want to make sure you charge both the batteries!

The second battery on the Metro is exactly the same as the one on the A2B Velociti 24's.


Here is a Wikipedia link which explains what a BMS is:

Link click here.


regards,

William

My ideal Li battery pack would come with a plug to easily disconnect the cells from the BMS for long-term storage. The cells really only need the BMS for LVC (low-voltage cutoff), HVC (high-voltage cutoff) and balancing. If the pack is not being charged or discharged regularly, the cells themselves have very low internal resistance, so extremely low self-discharge rates compared to lead-acid for example... The cells themselves could "sit on the shelf" for years w/no problem. Cells are normally shipped and stored partially discharged.

Lock

Lock,

I would agree with you. In design and manufacturing the thought process is most likely keep it simple for the average consumer hence no switch to turn off the BMS. Cells on their own as you mentioned indeed can be kept on the shelf for extended periods of time unlike SLA's.

We haven't measured the actual % loss due to the BMS, but with connecting up the UltraMotor chargers we have them running for almost 45min - 1hr each month so indeed there is a fair amount of discharge. Leaving them for several months without a charge is something I would want to avoid.


William

Thanks again William. This has been most helpful.

I think almost everything you can say has been said ;-)

In short, LifePo4 batteries are good to go and can take even cold easier.

Would be interesting to know your controller low voltage cut off, I don't even know it on my GIO W500.

It could be that with 16 cells Lifepo4 we could be totally safe :-)

Cheers

Dirk

I am looking for some guidance from our very knowledgeable group. I happen to own a bike (similar to the Daymak Gatto or Mobility Unlimited Volare) that has the batteries "built-in". In fact there are 2 separate battery compartments with each housing 2 x 12V 20ah SLA batteries and all 4 of course in series to give the 48V. I need to replace these (again!) and am seriously looking at Lithium this go round. The challenge I have is finding something with a form factor that will work in this bike (and at a reasonable price).
Details are:
Size of each battery compartment (L x W x H) ====> 181 x 157 x 166 mm
Typical size of a 12V SLA (L x W x H) ==========> 181 x 74 x 166 mm
so 2 fit nicely in each compartment with a little room to spare on the width.

So for lithium solution:

• I think I need to populate both compartments to get enough juice
  
• I haven't seen any configs of say 24V x 20ah or 48v x 10ah that I could physically fit in here and I could connect in parallel or series.
  
• I do recall having seen somewhere a supplier who was packaging a 12V lithium battery in something the same size as a 12V SLA, but can't find the reference (and I think it was pricey).
  
• If I had the wherewithall, I suppose I could build my own from individual cells, and maybe make two that would fit - but not sure I'm up for that
  

I'm looking for guidance from some of the gurus out there. I really don't want to buy more lead, but right now, that is my default position (or a new bike!)

Thanks for any suggestions.

I do recall having seen somewhere a supplier who was packaging a 12V lithium battery in something the same size as a 12V SLA, but can't find the reference (and I think it was pricey).

Maybe thinking of the 12V "bricks" from Elite:
http://www.ebikerider...


Dimensions for each brick: 178 X 76 X 165 mm


Mr.Ping has made custom packs upon request before to suit odd shaped battery spaces... but the cells etc that Elite offer are far superior...

Lock