Adding a Down tube Battery as a Spare


Well-Known Member
Northeast Pennsylvania
As my enjoyment of ebiking grows, so does the length of my rides. On some outings, I push 70 miles, which is close to the limit for the two batteries I usually carry. My batteries are aging and over 4 years, have lost almost 8% of their original capacity. On long rides involving slope or headwind, I find I'm getting close to running on empty. I would like to extend the length of my rides but the current battery configuration is a handicap.

My bike uses a 10# rear rack battery and I carry the spare in a pannier. The bike is already rear heavy and carrying a third battery in a pannier would not be practical. Instead, I bought a Hailong 52V 20 AH "dolphin" style battery and mounted it to the down tube. It was surprisingly easy to do with kits from Grin that use the bottle cage bosses.


For rides that don't require extended range, I remove the dolphin battery and use this adapter. It holds a bottle cage and a mount for an emergency cordless tool battery:


For transport, I leave the battery mount n place and protect the contacts with a vinyl cap:


With three batteries, I can now extend my range to well over 100 miles without adversely affecting the balance of the bike.
How did you do with the longevity and overall quality of the Hailong battery?
How did you do with the longevity and overall quality of the Hailong battery?

It's on it's 3rd season and has held up well. After 34 charge cycles, a bench test shows it still has 97% capacity.

It was a bit pricey with the unexpected tariff since I bought it from Grin Tech in Canada. IMO, it was well worth the $$ though for the quality Panasonic 18650 cells & nickel ribbon construction.
Hmm. If Grin Tech tells it, it is probably a good purchase. Have discovered them recently, and the prices are affordable. I don't want to underspend and risk safety, though, but I see 2 companies now recommending them, so maybe it is worthy. Thanks for the response.