Using Lipo batteries for an Ebike?

[PaulC]

I have to replace the NiMH cells in my Giant LaFree ebike 24v battery pack with Lithium cells, so I have been reading the Technical and General forums to see what approaches people have taken.
The prevalent approach is to either buy a battery pack of LiFePO4 cells with a BMS (e.g. Ping batteries), or recell the existing pack with the same configuration (Please note, I am in NZ so competent recellers of ebike batteries are scarce)
However I have noticed that some people have taken the option of using RC-type Lipo battery packs with a smart balance charger.
So my questions about this option are:
Q1: what are the reasons for doing this? Power? Cost? Other?(FYI, I am in the electrical business so I know about Watts, Amps, Volts, overcharging LiPos, etc)
Q2: the smart charger (e.g. an iCharger) will need to be plugged into the balance sockets of the Lipo batteries at charging time, but I assume the batteries are inside a weatherproof case. How do people manage accessing the balance sockets without having to disassemble / reassemble the weatherproof case each time?
Thanks
Paul

 

[Deleted member 4366]

Charging lipos is much more complicated than normal e-bike batteries and are considerably more dangerous. If you want to leave them in situ for charging, you need to make extension leads, which add to the dangers. I used to use lipos myself, when they were the only way to get a high power ebike battery, but I wouldn't recommend them now.

I think what you read is now out of date. Ping batteries were popular 7 years ago, but they have mainly disadvantages now because of their weight. Modern ebike batteries have moved on a lot in the past 5 years, so they're a much better solution. There's loads on Aliexpress to choose from. You should be able to find a cell-pack that will fit your existing case or use an external one, and run the wires through your existing case to the terminals after removing the old cell-pack.

 

[Nealh]

For safety stick with lifepo4 or lion cells with bms for a sealed battery, lifepo4 for longevity but heavier & lion cells a bit lighter.
With greater choice of cylindrical cells, lipo isn't really the no1 choice today, I have lipo's they get used now and then but for ease of use it's the lion packs now.

Lipo can be cheaper to buy as cell packs, then you need dc balance charger and a mains psu for power as well as series or parallel leads to connect them up and lipo alarms to monitor discharge. With lipo's you have to act as the bms for charge and discharge and can be a faff.
Most lipo users use a easy access triangle bag or pannier/rack bag so no hard case, charging wise any series connection is broken so that they are charged in parallel.

 

[anotherkiwi]

I use LiPo still but am eyeing up a 20700 Li-Ion solution for easier charging, good capacity, high Amp output and better availability.

I find LiPo easier to charge because it takes so little time with the right charger - less than an hour. LiPo is a good solution price wise if you can find the capacity you need on special offer, I can't at the moment. I will continue to use them while they are in good nick as a range extender.

 

[danielrlee]

I find LiPo easier to charge because it takes so little time with the right charger - less than an hour.

I second that. Sort of. 'Easier' is probably the wrong word. Maybe 'convenient' is what I mean.

I always planned to build a large 3kWh pack from 18650 cells for my next build (enduro bike), but I'm currently spoilt with 20 minute charging using RC LiPo and a 3kW charger that I'm not sure I would want to change.

 

[PaulC]

Hi all,
thanks for getting back to me with information about LiPo batteries and their benefits / risks.
AnotherKiwi - what do you do about ease of access to the balance lead on your Lipo batteries?
Thanks
Paul

 

[anotherkiwi]

I take them off the bike at every charge, they are either 20Ah 2x4S 10 Ah parallel + 2x6S 10 Ah parallel in an "aluminum" briefcase or as a 10 Ah small battery in a plastic Skip washing powder box.

I had an incident where I wasn't careful and pulled the JST balance plug off removing from the charger

 

[Nealh]

For any one wanting to use a soft pack 18650 set up in a top rack bag or pannier set up then Enerpower power packs from Germany with heat shrunk bms protected packs with xt90 and a 30a inline fuse. The one that caught my eye is the 10s 6p LG MJ1 pack using 10a 3500mah cells.

https://www.ebay.co.uk/sch/harvestmoonglory/m.html?_nkw=&_armrs=1&_ipg=&_from=