SLA vs LiFepro

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mf70
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Joined: 12/01/2006
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colin9876 (http://visforvoltage.org/user/colin9876) has sent you a message

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Hi Mark,
Reading ur post answer today (about the cells unbalanced), good answer.

I know ur a SLA fan even though most people have moved on to Lifepo, but wanted to say maybe ur right about Lead Acid still being a reasonable choice, because a number of people I know using Lifepo cells have suffered unexplained Bad cells recently - its a bit of a mystery. And an expensive one!

In reality Battery technology hasnt moved on that far! Particularly as SLA is good in high current situations, and fairly simple to charge whereas Lifepos need care and a minimum voltage that must be maintained!

Im curious how some of these new Lithium cars just coming out now will perform long term. I bet the battery packs will have problems within months not years!!

I would bet that they actually get pretty good service life, for one crucial reason; they will have sophisticated BMS programmed to coddle the pack. We see this right now with laptops. While battery packs fail, there's not the cascade of surprised customers we've heard of around here. There are two crucial caveats:

  • COST: an 18V pack for a laptop will cost $80.00 to $150.00. Probably half of that is the BMS circuits built into each pack. (BTW, I wonder why the BMS isn't part of the computer? Perhaps long term operation on unconditioned power can lead to BMS failure (voltage spikes can degrade some components), so the BMS is replaced on the same schedule as the batteries.)
  • Lifespan: Even with a gold-plated (literally!) BMS, I don't get much more than two years from a laptop battery pack.

You are right about my preference for SLA: As far as I am concerned, that is purely because of cost: both the guaranteed replacement cost and the thread of unplanned failure cost. I will leave the experiments with Lithium to the other less wallet-driven explorers.

I also have a cost-based reluctance to over-volting; I have seen enough magic smoke come out of my electronics already without tempting fate.

Mark

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