Lipo for the Wife-E-bike - userfriendly...

[hjns]

Hi all,

I just wanted to have some expert input on an idea.

Background

• I closely follow the 12s2p LiPo pack kit including 12-channel BMS "Lite" Board thread, and I am anxiously awaiting a working model. However, it got me thinking...
• I am not an engineer, but I know how to use a soldering iron. I also have experience with RC helis.
• In the meantime, my wife's E-bike (250W, 15A, 36V10Ah LiIon), that she uses every day, has insufficient range when cycling in the hilly area around Basel.
• Therefore, I would like to make a Lipo/PSU pack that will give her sufficient range to last a busy day (max 50km/30miles, some hills of 15%, slight pedaling) and still maintain the connect-one-connector-and-charge-and-walk-away usability. We charge the current LiIon battery every night.

Proposed methods (open for suggestions)

• Use lipos; 3 or more 37V 10S1P 4.5Ah zippy lipo's in parallel. Total number of packs to be decided based on actual performance. I imagine 3 or 4 bricks (13.5Ah or 18Ah) should do it, I will try 3P in reality with that bike and see after which (arbitrary) distance the lipos are discharged lower than 3.6V. If the distance is sufficient, than the pack will be 10S3P, otherwise it will be 10S4P (or more).
• Add a simple battery tracker that will blink if voltage drops lower than 3.6V on one cell (in case of a missed overnight charge). This will replace a complete LVC system, because I am not sure if the controller has an LVC. BTW, the price is not $90 but $39 at HK.
• Add a switching PSU that accepts 220V AC (standard in EU) and that can deliver a charge with the HVC at 41.5V. Would this watertight 240W model HLG-240H be ok? Specs say that it may deliver 6.7A, so total charge time would be approximately 3 hours.
• Put the Lipo's and PSU in one package, with allmost all wires completely hidden. On the outside, one connector for the controller, one connector for the 220V AC, and one connector for the paralleled balance wires so that I can check the individual cells on a monthly basis. If necessary, I will then balance/charge using a dedicated 10S balanced charger.
• Cover the whole package with a sheet of carbon fiber, with easy access to the connectors, add a handle, and paint in a nice way.

Proposed results (open for suggestions)

• An 18Ah lipo pack/PSU combo at the same weight as the current LiIon pack, that flashes if one cell is lower than 3.6V, which can be directly connected to 220V, and which will automatically turn off when the pack has reached 41.5V.
• Slight improvement in performance due to higher available voltages
• Total price for an 18Ah pack would be ($40 (LVC) + $120 (PSU) + 4x $82 (Lipo)) still less than $500.

edit: I found a 36V 9.7A 350W mean well on Ebay for $43, so that brings costs down to less than $450...

So, what do you think?

 

[o00scorpion00o]

LiPo isn't exactly user friendly!

If I were you I would check out cell-man's A 123 LiFeP04 packs, they got bms and are simple to use!


Mark

 

[jimw1960]

If you only need 15 amps, Lipo seems like a bad choice. A 48v/15Ah ping battery would do the job for about the same money, less maintenance, easier plug-and-play usability, longer life, and better safety. Lipo is only worth it when you need POWER.

 

[999zip999]

For a simple plug and play and the needs of your 250w-15amp. combo a Piing is a great match 36v15ah. A lot less chance of a lipo fire ball. Easy bms led lights for balance. And Li ping support. Check the thread lipo fire on chicks bike or take out some extra insurance. How are you and your wife getting along ?

 

[dogman dan]

Lipo is really best for somebody willing to do a minimal tlc with them, just making sure the golden rules are never broken.

The c rate means nothing to you, when all you are needing is less than 1000 w.

The cycle life penalty, some say half that of lifepo4 is there, but you aren't using the c rate.

So you are left with a battery not a heck of a lot smaller or lighter than a pouch cell lifepo4 such as a ping. People will say it's a LOT smaller and lighter. But compared to pouch lifepo4, it's not smaller and lighter by much.

So double her range with a 36v 20 ah pingbattery, which is pretty plug and play. With his 5 amp charger upgrade, you still get to charge resonably fast at about 200w. So about 3-4 hours to fully charge. Not really that slow.

The fire danger is not nearly as big a deal as some say. You'll have to protect the ping from pouch damage too. But doubling the lifespan would have me interested. It's not for a 3000 w bike. If it was, then you'd want lipo.

 

[liveforphysics]

With Method's HVC/LVC boards, in theory it should work out OK.

However, in practice, I can't see myself giving a woman with no battery experience an RC LiPo pack on a good conscious.