Steps to figure out if you can upgrade your e-bike's battery to a more powerful one?

[ebikebob]

Hi, wife isn't super enthusiastic about my chances of converting a regular bike to an e-bike.
My best bet to keep everyone happy is to buy a pre-made e-bike and then try to do a small mod. The only one I want is to upgrade the battery.
For example, many of the bikes I am perusing have a 36 V battery, but I would like to change to a 48 V battery, at least 12A battery.
I have no idea how to know if a bike would accept such a mod. Even if I could physically attach a battery, would the controller limit its potential speed anyway or not accept a "foreign" battery at all?
Is it pretty much just trial and error and we thank the guy who went through the door first, figuratively speaking?

 

[Ebiker01]

Well, another cheapo on the forum... just work harder or convince your wife that it is a real NEED to buy a proper 3000$ ebike with a 48v system and at least a 600wh battery !

If not , you'll buy that 599$ 36v ebike then it will break down, and you will be back here crying...

Advantages of a proper ebike :

-Health
- LOTS OF $ saved (as in thousands over 2-3years)

If 1 kw is 0.13$ , charging a 600wh pack costs 0.08cents !
Then add a chain and a cassette in 2-3years .
THAT IS if buying a PROPER ebike.

You could also install a few solar panels @ home and save even better.


- reliable and safe (meaning you won't get stranded on tbe road when that 36v Archer amazon ebike breaks down...)
- good resale value 2-3years later .

 

[harryS]

Which bikes are you wanting to change the voltage? Many of the better bikes would see the higher voltage as system error and lock you out.

Economically, even if you had a compatible bike, you're paying $400-700 more for a battery that might have cost you an incremental $200-300 for the 48V bike in the first place.

 

[ebikebob]

I see, well then the question becomes: there are batteries that are 48 V * 10 A and others that are 36 V * 13A. Same Wh, but how would performance differ between the two? I keep thinking that a 36V * 13A battery would "feel" weaker when turning the throttle, all things being equal.

 

[tomjasz]

Unless you share some motor specs we're not able to help sort. Don't buy a 36V system wanting a 48V. I happen to like my MAC motors that can be run on a range of voltages.

 

[harryS]

The WH will determine your range. Performance is a matter of motor winding, voltage, and gearing. If everything stays constant, a motor spins faster/harder on higher voltage.

Sounds like you want to go fast. Buy a $200 1500W rear motor kit. Put it on a donor bike with good brakes. You can reach 30 mph on 48V. That's not fun for me. I gave up motorcycling years and years because of too many near misses in city traffic. Why get back into that with a bicycle. It's enough to worry about getting doored at 14 mph.

 

[AHicks]

Not following the math. A cheap e-bike is 900 - 1000. A 48v battery is 500, and you won't know for sure if it's going to work until you've ridden it long enough to know that the electrical and electronics are going to hold up to it.

Why not just get a RAD (1399. or so) or something similar for the same money? Bonus will be a warranty and some decent resale?

 

[ebikebob]

Thank you everyone. I can't buy a radpower bike where I am, unfortunately or I would have bought the radrunner. I currently have an old Giant e-bike that was 36 V 10A and the acceleration is woeful. It's a throttle bike mainly and it simply can't move after a red light turns green without serious pedaling, which is already heavier than an ordinary bike. The top speed is about 15 mph and here people can go about 20-25 mph and nothing is enforced. I am always the slowest vehicle on the road, and usually about as fast as a city rental non-electric bike. There are grandma ebikes beating me. My Giant branded motor is a 250W rear hub, and that's all I know. It is from 2014. Do I need a 48 V motor and 48 W battery to feel like my bike is responsive enough? Otherwise there are many 36 V on paper similar spec'd bikes that I have neglected because I figure I'd be getting the same performance.

 

[AHicks]

Only pure curiousity, but why are you not able to buy a Rad?

 

[FlatSix911]

A lot of tough love on this thread... and probably good advice to buy what you need to start.

 

[harryS]

I see you are in China, ebikebob. That's where Rads are born, at about 33% of their final price here. Is it because they are outlawed because of motor size?

Does the Giant run on a lithium pack? Maybe yours is worn out.

 

[Old Salt]

Converting a regular bike to an e-bike is not too difficult. Choose something with a strong frame, such as a mountain bike, cruiser, fat bike, or hybrid. Make sure your donor bike has good brakes. Band and coaster brakes are not good on a powered bike. V-brakes can be used, although I prefer hydraulic disc brakes. Conversion kits are available through the big on-line shopping websites. If you want a really bad ass bike, check out Sick Bike Parts' 3Kw / 48V kit. I recommend at least a 48V 40 Ah battery for it. Do your research. The bike should provide a comfortable ride without the kit installed. You will also want to upgrade the tires to some with a higher puncture resistance, and longer wear. Those that come with the bikes are low cost, and you'll be lucky to get most than 500 miles on them. This advice comes from converting bikes to gas power for the past ten years.

The motor, controller, and battery voltage must match, at least until you get some experience with electrical power. Getting a battery with a higher Ah value will increase your range. Getting a motor and controller with a higher power rating can increase your speed, acceleration, and/or load carrying capacity. Increasing the battery voltage, decreases the current required to deliver the power to the road. This decreases the power losses in the system, boosting the performance and range. All components, including the wires have resistance. The power loss increases proportionally to the square of the current.

I had a Schwinn e-bike with two 10Ah 24V SLA battery packs. Without pedaling, I was only able to complete a 13 mile (21Km) round trip using the two battery packs. Keep that in mind when evaluating either your conversion or a pre-built electric bike. Give yourself 25wh per Km or 40wh per mile of travel. Your best bet is to try before you buy a pre-built, ensuring that you completely drain a fully charged battery.

The round trip distances I need to cover are high at 50Km (31 mile), 100Km (63 mile), and 250Km (154 mile) round trips. This is why I've used gas powered bikes until now. To cover these distances I need batteries with 1.15Kwh to 5.75Kwh power storage capacities. At 24 volts this is a battery from 50Ah to 240Ah. At 48V the Ampere Hours are half that. This means multiple battery packs, or carrying a charger. I'm working on it.