@ dilkes

I personally both prefer and have more experience with the packs designed for portable solar power stations due to their lower cost per real Ah capacity but they require more work on your end then a high quality motorcycle/ATV/sport battery. It should be noted that the solar station packs and cells are rated in their true lithium chemistry amp hours (of which 80% is useful on a lithium battery which should not be discharged below 80% capacity for maximum service live) where as the motorcycle/ATV/sport batteries are rated in equivalent Ah to a lead acid battery were the conversion factor between the two is 1.8 or in other words a motorcycle/ATV/sport LiFePO4 battery with a 36Ah rating is actually a 20Ah battery it is just that because the Lithium battery can be safely discharged deeper into its cycle a 20Ah lithium battery has the same useful capacity as a 36Ah lead-acid battery and since the buyers of motorcycle/ATV/sport batteries are used to buying lead-acid batteries and the LiFePO4 batteries are new for that application they are rating them in their equivalence to lead-acid batteries rather then in their actual capacity numbers so you must do the conversion to the lower number for comparing pricing when shopping to build an e-bike battery pack.

The solar power packs (and you can even buy the prismatic cells used in them individually) use screw top terminals and are available in cell sizes ranging from 10Ah to 200Ah with the 20Ah size being the most commonly available size on the smaller end of that size range (10Ah prismatic cells are available but not very common) and work great for e-bike applications.

I buy mine here: http://www.batteryspace.com/12-8v-li...-to-200ah.aspx

Specifically I buy these ( $124 ): http://www.batteryspace.com/LiFePO4-...thout-PCM.aspx

And install four of these ( 4 x $7 ) myself: http://www.batteryspace.com/Smart-LE...e-Current.aspx

Which gives me the same as this ( $179 ) and saves me a few dollars by installing the balance circuits myself: http://www.batteryspace.com/LiFePO4-...Balancing.aspx


That takes care of balancing and I rely on the motor controllers minimum cut off voltage to protect against over-discharge and trust the battery charger to protect against over-charging. Which has worked out great for me. Now on the other hand a quality motorcycle/ATV/sport battery will have a full battery management system built into it that not only balances the cells but has internal protection against over-discharge and over-charging built right into it in a full BMS usually with a water tight sealed case with just two terminals to hook up too so much simpler and easier for the end-user and with potentially better battery protection if your controller and charger aren't up to snuff in doing their end of that job but the cost will be higher. An EarthX brand name (what I have experience with) 36Ah lead-acid equivalent (20Ah actual) battery will cost $340-$360 so you end up paying twice or slightly more the price for the same capacity compared to using the solar cells instead but everything is there all ready to go and all sealed up tight as a drum and after all is a US battery rated for a service life of 4,000 cycles over 8 years with a BMS that continuously balances the cells during both charge and discharge rather then just top end balancing and has over-discharge and over-charging and short circuit protection built in BMS. So there is some extra quality there compared to the solar power cell set-up that are rated for 1,000 to 2,000 cycles with top end charging balance only and over-discharge and over-charging protection must be provided externally and there is no short circuit protection and the plastic case is not sealed and and just a container to hold the cells together. But with the solar pack it is also possible to easily remove and condition or replace individual cells in the pack if their is a problem rather then having to replace the entire 12V pack itself in entirety (this is also a significant advantage over most ready built e-bike packs which are one complete unit that does not allow for easy isolation and conditioning or replacement of an individual cell so a single bad cell can render the entire pack useless).

As to charging ~ Yes, I charge all my 12V packs at 12V either separately or in parallel sometimes on the bike and sometimes off and then hook them up in series to power the bike. With the screw terminals that both the prismatic solar pack cells and the motorcycle/ATV/sport cells use this is an absolute breeze and you just need ring terminals with a light coating of dielectric grease and some nuts/bolts to fit the threads and a little wrench to fit them, or you can even make up some plug wire harnesses with a plug on the batteries and a plug on the bike and a plug on the charger and when you unplug the battery from the bike and plug into the charger the plug is already wired in the plug end to switch from series to power the bike and parallel to charge the batteries.

Both the 12.8V prismatic cell solar power packs and the motorcycle/ATV/sport packs can be charged using either conventional lead-acid 12V battery chargers or dedicated four cell LiFePO4 pack chargers although the solar cell packs will usually have a slightly longer service life if charged with a dedicated LiFePO4 chargers. Higher quality motorcycle/ATV/sport packs due to their internal BMS charge control circuitry don't care which they are charged with.

The MAIN benefit I find to using multiple four cell 12.8V LiFePO4 packs wired together in series to power my e-bikes is because I have the ability to charge almost anywhere I can get my hands on a 12V car battery charger or even just a car and a pair of jumper cables and in a pinch I can make do without having to have a specific charger.

The MAIN benefits I find to using the prismatic cell solar power industry LiFePO4 packs is their low cost for good quality cells and their repairable nature where with the screw top terminal individual cells the packs are made of there is no soldering of cell tabs and it is quick and easy to break a pack down and find the bad cell(s) and individually re-condition them with a single cell charge/discharge cycling unit or completely replace individual cells if necessary due to their standardized modular design.

For some applications the motorcycle/ATV/sport batteries can also be useful just be sure to get the high end quality ones otherwise you will end up paying more for the same or lower quality then the solar packs. And the only reason to go with these instead of the solar packs is because your application is such that paying more for higher quality makes sense so if you go that route for darn sake get the good ones.