36V Commuter Battery is Dying - Rebuild or Replace?

[JL0256]

Hey everyone,

Hoping to tap into the collective wisdom here again. This time, the question is about my trusty old commuter bike, not my main 52V ride.

It’s a simple 36V hub motor setup that I use for quick trips around town. The original 10Ah battery is on its last legs—it used to last me a full week of short commutes, but now I'm lucky to get three days out of it.

So I'm at a crossroads: is it worth finding a place to rebuild the pack, or should I just cut my losses and buy a new replacement battery outright? I'm trying to figure out the best bang for the buck in terms of reliability.

Also, how's the compatibility with aftermarket batteries these days? My current one has a pretty basic cradle mount. Am I likely to find something that's plug-and-play, or will I probably need to get creative with mounting and connectors?

Since I know the benefits of higher voltage from my other bike, I'm tempted to upgrade this one to 48V. But I'm guessing the stock 36V controller won't handle that without going up in smoke. Is that a correct assumption? I'm not looking for crazy speed, just a bit more help on the hills.

At the end of the day, I just need a solid, reliable solution that gets me back to charging once a week and will last at least another 3 years.

Any advice or real-world experience would be a huge help. Thanks

 

[6zfshdb]

Welcome to the forum!
If you post more information on the battery type and brand of bike, you may get more specific recommendations. Pictures are also a great help.

I've faced this issue with several of my batteries in the past.
Rebuilding can be a cheaper option and there are places around the country that rebuild batteries. However it may be difficult to determine the quality of the components & construction used. Cheaper cells, BMS and construction methods can lead to trouble down the road. Shipping can also be an issue since you have to get the battery to the shop.

In my case, I look for quality replacement batteries, UL rated if possible, and just eat the extra cost. To me, it's worth it for the peace of mind.

 

[JL0256]

Welcome to the forum!
If you post more information on the battery type and brand of bike, you may get more specific recommendations. Pictures are also a great help.

I've faced this issue with several of my batteries in the past.
Rebuilding can be a cheaper option and there are places around the country that rebuild batteries. However it may be difficult to determine the quality of the components & construction used. Cheaper cells, BMS and construction methods can lead to trouble down the road. Shipping can also be an issue since you have to get the battery to the shop.

In my case, I look for quality replacement batteries, UL rated if possible, and just eat the extra cost. To me, it's worth it for the peace of mind.

Thanks for the warm welcome and for sharing such a detailed and thoughtful reply.
Your points about rebuilt batteries make a lot of sense. I was mainly thinking about cost, but you’re absolutely right—cell quality and the BMS are total wildcards. The “paying extra for peace of mind” approach really hits home for me, since reliability is exactly what I need for this bike.
For more context, the bike is just a basic commuter from a few years back (nothing name-brand), and the battery is a standard 36V 10Ah dolphin-style pack.
Also, mentioning the UL rating is a fantastic tip; I'll definitely keep an eye out for that when searching for a replacement. Since you have experience with this, do you happen to have any replacement battery brands or vendors that you personally trust or would recommend?

 

[6zfshdb]

Thanks for the warm welcome and for sharing such a detailed and thoughtful reply.
Your points about rebuilt batteries make a lot of sense. I was mainly thinking about cost, but you’re absolutely right—cell quality and the BMS are total wildcards. The “paying extra for peace of mind” approach really hits home for me, since reliability is exactly what I need for this bike.
For more context, the bike is just a basic commuter from a few years back (nothing name-brand), and the battery is a standard 36V 10Ah dolphin-style pack.
Also, mentioning the UL rating is a fantastic tip; I'll definitely keep an eye out for that when searching for a replacement. Since you have experience with this, do you happen to have any replacement battery brands or vendors that you personally trust or would recommend?

There are many reputable battery suppliers, and I'm sure others will chime in here with recommendations.
In my case, most of my replacement batteries were purchased from Grin Tech in Vancouver:

Batteries - Ebike Parts - Shop

Here are all of Grin's battery packs currently for sale, including Reention case downtube batteries, rear rack eZee packs, and some small bottle-shaped batteries for lighter builds. For a higher-level description of the battery options, view our <a href="/getting-started/battery-options.html">...

ebikes.ca

They stand behind their products and I've found them great to deal with. Be aware though that it's a Canadian company and there may be tariff issues which can affect the price.

One possible solution for you might be their Ligo modular series:

LiGo 10x Battery Pack

LiGo 10X, Air Travel Friendly 36V Stackable Battery Pack and Mounting Hardware. Click here for full product info page

ebikes.ca

Four modules will give you a 36V, 11AH battery that can be mounted dolphin style and taken apart to travel by air if necessary.

If you're a DIY'er, with a little work, you can also use cordless tool batteries to power a bike. They can be carried in a rear rack bag or pannier or mounted to a downtube:

Two 18V or 20V tool batteries wired in series will work with most 36V controllers. IMO, it would be risky to try using a 48V battery with a 36V controller.

 

[PedalUma]

Pictures are also a great help.

I need to see the patient for a diagnosis.

 

[harryS]

Our first ebikes came with dolphin case batteries ten years ago. In my opinion, a very rugged case. Bulkier than the current Hailongs but better made.



Ebikeling sells a big 36V17.5Ah model. They're a popular kit vendor. I have two of their motors, but never bought their batteries. FTH also sells Dolphins. You also see them on aliexpress. Sometimes called the Atlas case in China.

You can buy any battery with a cradle though, and install that in place of the dolphin.

 

[PedalUma]

Find out what is inside. I purchased a Cab Franc for a dinner party tomorrow. I know the grapes and terroir. I know the vintage. I know what is inside. You can read the stats of a wine such a alcohol percentage, acidity, and residual sugars but do not really know anything about it. Do not buy a battery by the stats.

 

[JL0256]

There are many reputable battery suppliers, and I'm sure others will chime in here with recommendations.
In my case, most of my replacement batteries were purchased from Grin Tech in Vancouver:

Batteries - Ebike Parts - Shop

Here are all of Grin's battery packs currently for sale, including Reention case downtube batteries, rear rack eZee packs, and some small bottle-shaped batteries for lighter builds. For a higher-level description of the battery options, view our <a href="/getting-started/battery-options.html">...

ebikes.ca

They stand behind their products and I've found them great to deal with. Be aware though that it's a Canadian company and there may be tariff issues which can affect the price.

One possible solution for you might be their Ligo modular series:

LiGo 10x Battery Pack

LiGo 10X, Air Travel Friendly 36V Stackable Battery Pack and Mounting Hardware. Click here for full product info page

ebikes.ca

Four modules will give you a 36V, 11AH battery that can be mounted dolphin style and taken apart to travel by air if necessary.

If you're a DIY'er, with a little work, you can also use cordless tool batteries to power a bike. They can be carried in a rear rack bag or pannier or mounted to a downtube:

View attachment 202280 View attachment 202285

Two 18V or 20V tool batteries wired in series will work with most 36V controllers. IMO, it would be risky to try using a 48V battery with a 36V controller.

Thank you so much for taking the time to write such a detailed and thoughtful reply. I also didn’t think about things like possible import costs, so I’m really glad you mentioned that. It definitely gives me a clearer picture of what to expect and what to keep in mind moving forward.

Thanks again for being so generous with your knowledge. I think I'm more confident about choosing an alternative battery after taking your advice.

 

[JL0256]

Our first ebikes came with dolphin case batteries ten years ago. In my opinion, a very rugged case. Bulkier than the current Hailongs but better made.

View attachment 202307

Ebikeling sells a big 36V17.5Ah model. They're a popular kit vendor. I have two of their motors, but never bought their batteries. FTH also sells Dolphins. You also see them on aliexpress. Sometimes called the Atlas case in China.

You can buy any battery with a cradle though, and install that in place of the dolphin.

Thanks a lot for sharing your experience and the extra details. It’s really helpful to hear from someone who has used this type of case for so many years.

 

[Slaphappygamer]

Here is another place that I've been looking for batteries at. I've seen this be recommended a couple of times. They only have 48v and above packs, but may have the cradle batteries that you are looking for. I was looking at a "raw" pack. There is a 52v 13.5ah (P45B cells) battery that will fit inside the frame of my ride1up 700 series.

 

[6zfshdb]

I'm not sure where you're located but I deal with Bicycle Motor Works here in eastern PA. They are local to me so I can pick up and deliver without having to ship anything.

https://www.bicyclemotorworks.com/

They are a great resource and may be able to help you with rebuilding or replacing your battery. Talk to Matt at 484 793-2541

 

[JL0256]

Thanks a lot for sharing your experience and the extra details. It’s really helpful to hear from someone who has used this type of case for so many years.

I'm not sure where you're located but I deal with Bicycle Motor Works here in eastern PA. They are local to me so I can pick up and deliver without having to ship anything.

https://www.bicyclemotorworks.com/

They are a great resource and may be able to help you with rebuilding or replacing your battery. Talk to Matt at 484 793-2541

Thank you for your suggestion, I will take a look.

 

[Beeps]

I used Hi-C battery rebuild service in Denver CO. A 36v 13ah flat battery was upgraded to 17ah,giving much better range. No problem shipping the old one there using UPS,turn around time was about 2 and a half weeks. Highly recommended.