12v10ah sla batteries

[Rasman]

specifically, this one:
http://www.tayna.co.u...id-Battery-P3622.html
4 of these will be used together in a high current application so will require charging regularly, but - assuming I don't run them completely flat - how many charge cycles can you expect to get from this type of battery?

[ChuckFickens]

moist specs for lead acid batteries state 300 - 500 typically

from a personal viewpoint, they are very similar to the batteries used in little UPS's (battery backups for computers) and they typically last about 18months to two years in my experience.

[ChuckFickens]

Errrr...


Most specs...... not moist!

[Rasman]

That's good news. Thanks Chuck.

[beso]

The number of cycles is inversely proportional to the depth of discharge.

A small number of deep discharges will wreck them especially if they stay discharged for any length of time.

For regular cycling they should be maintained above 80 %.

In practice the optimum size of the battery is determined by the expected frequency of discharge against the cost and other disadvantages that accompany the size and weight of a large battery.

Where size, weight and multiple cycles are all important a different technology such a s lithium ion batteries are a better solution.

[Rasman]

Maintaining 4x12v sla batteries above 80% isn't realistic given the current drain for the Ebike project I have in mind. So I agree with you beso, lithium ion is the way to go (despite the huge cost)
The thing that confuses me is that it's a 1Kw motor, 25A controller and supplied with 4 12v 10Ah sla wired in series to give 48v with a top speed of 30MPH and an expected range of 15 miles.
I want more from this, so would this configuration of lithium cells do the job or will I burn something out?

http://oi55.tinypic.com/34g4oky.jpg

[Rasman]

Just trying to extend to range, 45 miles at 30MPH?

[beso]

So long as you supply it with 48 volts the system should perform the same.

When connecting batteries in series (positive to negative of the next as your diagram shows) you add the voltage of each battery. When in parallel (all positives together and all negatives together) the voltage stays the same but the amphours increase.

Either way the total stored energy (volts time amphours) is the same.

The voltage sets the maximum speed. The total energy (volts times amphours) sets the maximum range.

The internal resistance of the Lion cells might be lower and allow them to do more current. However the controller should have a current limiter circuit built in to protect itself and limit the maximum power. Check with the manufacturer to be sure.

BTW. One kilowatt is a very powerful electric bike. Is that legal in your country? In Australia we have a pathetic legal limit of 200 Watts. A one kilowatt bike would need to be approved and registered as a motor cycle.

[beso]

This site has some specs including DOD vs Cycles for SLA batteries.

http://www.home-ups.co.za/Batteries_pk.html

Also note the discharge rates shown. The capacity of the battery depends on the rate of discharge. Most SLAs are rated at the ten hour rate (ie the current that will fully discharge it in ten hours). If you are discharg in in one hour the capacity will be well below that on the nameplate.

[Rasman]

Thanks beso