Lipo setup for 24v system?

[Jay64]

My brother is trying to build an electric bike with his daughter and called me asking about what lipo setup would work. I'm just getting into lipo myself, so I had to take a look at it. 3.3v looks like it would be just under with 7s and just over with 8s. Which route would be the better one to go with? Anyone sell any 7s or 8s packs? or would he just have to go with 2 4s packs in series?

 

[dogman dan]

6s charges to 25v max, so 7s that charges to 29.2v would be good. My old 24v nicad packs charged to 28v. Better one volt more than 4v less.

I'm talking about RC lipo from hobby king. charges to 4.2v per cell and a sensible stopping point is 3.65v.

However, you can't easily buy 7s packs, and some chargers don't have a 7s charge setting. I run my 24v mower on 6s lipo, and it does fine since there is nearly no sag. Lots of others do similar and run 6s. Will work fine at 6s, if the lvc is low enough. I run an old 24v think electric bike on 6s also, but that bike never rides far enough to lvc.

 

[miuan]

However, you can't easily buy 7s packs, and some chargers don't have a 7s charge setting.

battery
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=21364

charger
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=7523

Both of them available for purchase. I'd buy 4 batteries and solder them in parallel.

 

[neptronix]

No great match really in the 3.6-3.8v nominal cell world. You might want to give lifepo4 a look, it matches the voltage of 24v lead acid very well.

6s has a lower nominal voltage. 7s has a higher nominal voltage. not much in between.

 

[Jeremy Harris]

I built a 7 S LiPo pack for the 24V bike I picked up cheap on ebay for my MiL. I used two 3S 5Ah packs and two 4S 5 Ah packs, which works fine, as it's a low power, pedelec, ebike.

The original 24V lead acid batteries would have been around 29 to 29 V hot off charge, pretty close to the 29.4 V that the LiPo pack comes off charge at.

 

[Jay64]

However, you can't easily buy 7s packs, and some chargers don't have a 7s charge setting.

battery
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=21364

charger
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=7523

Both of them available for purchase. I'd buy 4 batteries and solder them in parallel.

How would that charger work without a power supply?

 

[RyanTo]

I just did a 6s4p pack as a backup battery for my 24v ezip skyline. It makes the skyline's light indicator read "half" when I fully charge the lipo pack to 25.2V. It does work, just a little lower then a 24v li-ion battery fully charged.

 

[dogman dan]

Well there you go. Not having money to spend lately, I don't roam the HK site much these days. Perfect for 24v, or 14s 48v. Thanks, now you got me wanting to buy more lipo.


I run two of those chargers on a 350w 12v meanwell. Mine don't have a lilo setting, so they don't go to 4.1v, only 4.2.

I just looked, and my turnigy 8s chargers do have a setting in the menu for 7s. Some chargers don't. Likely the better chargers, like hyperions, will also have the 7s setting functional.

But like I said, having near zero sag, I found 6s lipo worked much better on my mower than 26.5v fully charged lead.