hillyterrain said:
I'm going mad, I keep reading the forum and settle on a certain technology and then I keep reading and find out why certain people don't use it and jop to the next chemistry and so on ..
Basically it depends on:
--your budget,
--your limitations in knowledge/abilities/willingness to learn,
--your system requirements for current/capacity/etc.,
--your available vehicle space to place them and weight limits,
--your patience with personally monitoring charge/discharge or buying the right kind of reliable monitoring system to do it for you, or getting something that is not *as* critical to do that for. (it matters with all of them, just a lot more with certain ones).
The general consent seems to be that A123 is top of the line, but you never know whether or not you actually get genuine cells. Looking at OSN or victpower they state no price on their website, how does one actually purchase genuine A123 cells?
Depends on the kind you want--becuase A123 does not sell directly to the public, (and they dont' actually really exist as such anymore, either), you can't actually know *for certain* that any cell you buy as A123 actually will be. Some places, like EM3EV (cell_man here on ES) almost certainly have the real cells, in good quality, and some other places *might* have good ones, whether genuine A123 or not (like OSN)--but it is a crapshoot with most of those places in China, other than EM3EV.
As for a consensus that it's top-of-the-line, well, that entirely depends on your needs. If you don't need super high currents out of it, NMC like LG Chem and EIG would do just as well, and be lighter, too. And at least for EIG, you can buy them directly from the manufacturer, guaranteeing genuineness. (it'll cost ya, though)
My place is old and all wood, I think if one cell burns the entire place would burn to the ground. Would charging in a metal container in the bathtub make things safer?
Any chemistry can catch fire if something goes badly enough wrong during charge or discharge, or the wrong chain of events happens over time. Personally I keep my (repaired/salvaged origin) RC LiPo in my kitchen oven, closed, and it's in vented ammocans on the bikes. Some of what's in the oven is also in it's own ammocans, and it's spaced out as much as I can get it in the small space. Dead cells or unknown stuff is out in the BBQ grille away from the house. Just in case.
(I don't honestly think anything will ever happen, but I have four dogs taht can't escape by themselves if it ever did, so not gonna risk it).
Generally, it ought to be ok as long as you pre-test all your packs to weed out anything questionable, use *good* monitoring equipment that you trust, at cell-level, build your pack up so in the event of a fire it will only take out the pack itself, (even better if it only takes out the subpack that starts it, but that makes your main pack even larger to give that spacing, insulation, and firewall material room).
You also need to size your pack so you have a significant percentage more Wh than you actually need, so you never have to worry about running it too far down--and use LVCs at cell level so that nothing
Correct me if I'm wrong and please explain to me why one would choose the Turnigy over the Zippy (LiFePo4) or the other way around.
It sounds as if you are under the impression that Turnigy is one chemistry, and Zippy is LiFePO4--that's not the case. Turnigy and Zippy are just two "brands", as it were.
In case you're actually asking about which one of those brands has better LiFePO4 cells, AFAICT neither has any good ones. You would want Ping, A123, or *maybe* the Sunthing (IIRC) packs for LiFePO4. *Don't* get Vpower/Volgood/etc packs--they do work (usually) but they suck to have to fix whenever tab welds break or cells die and take the string with them, etc.
(see my threads on repairing them for examples).
But I got the impression balancing is really important for this one and you shouldn't buy packs that are already paralleled and you cannot simply extend the pack after it got some use as you could with the LiPo, is that correct?
Balancing is important for *all* chemistries, though when they are "new" many types may not need balancing--as they age they will, though, as some cells lose capacity before others, or get higher Ri, etc. Some require an external balancing setup, and some like NiMH and NiCd do it via the main charger leads in an internal chemical process (making a lot of heat).
You can always parallel more sub-packs or whole main packs together for more capacity, evne if it is just by their main leads, letting each main pack's BMS take care of balancing or LVC/HVC/etc. Doesnt' matter what kind it is, other than NiCd or NiMH (those you don't really wanna do taht with).
What about LiMn? Seems like many commercial ebikes use this one, any cheap build-your-own-kit vendor for those?
Dunno--no experience on them yet, but they are a good option from what I have read on ES.
NMC is another good option, but as it is somewhat newer it is harder to find cheap sources of reliable cells or packs. EIG and LG Chem are the only two large-format (20-40Ah pouch) cell providers I can think of right now. The EIG pack I have is nice, and even with accidentally going to 0V on the 3s lighting pack I was able to recharge it and use it normally, with no problems, no fire, etc. so far, in nearly a year I guess i has been since then. I would not have even attempted that with RC packs or other LiCo cells.
(I'd've scrapped them, and I re-use just about anythign that still has life in it!)
how to avoid the LiPo to burn down your house / skin while charging and riding?
It's not so much avoiding them as using them appropriately, with the right precautions and proper charging and knowledge.
Linked thread in wiki
http://www.endless-sphere.com/w/index.php/Picking_out_a_battery:_what_you_need_to_know