Missing something?

[MillerEbike]

Hope I can get a little direction.. I purchased a RBIKE.. a basic inexpensive ebike (36v, 250w rear hub motor and a 8.8AH battery) cost about $650, I like it but can tell I will want more power and it does not do the 25MPH as advertised.. of course.. To experiment I decided to purchase a conversion kit for my wife's Trek bike.. I got a Voilamart 36v 500w front wheel kit and purchased a 36V 14.5Ah New Frame LG cells inside ebike battery pack. Did the install but found that my 250w RBIKE has more power than the 500w kit with a battery almost twice the size.. ? Any ideas on this would be appreciated. Just a little more info.. the 500w Voilamart kit just has a throttle with an LED gauge.. so no ability to set the assist level. Not sure if the system has the ability to put out more power. Would getting a LCD display give me the ability to tap into more power? Also, under power only the bike with go about 14mph... seems slow for a 500w system. Thanks

[Kocho]

Could it be speed limited? Might be possible to reprogram it somehow.

Also, note that your two batteries have identical voltage and both should hopefully be capable of providing enough current to read the 500W. Did you measure their voltage off the bike to make sure they both charge similarly? The bigger battery will give you more range and max power longer, but for short bursts I would not expect much difference, if any. Did you try the 500W kit with the smaller battery? Did you try swapping the controllers too (provided they are external and not built in the hubs)?

[MillerEbike]

Thanks Kocho.. not sure if the controller that came with the 500w kit can be programmed as there is not a USB port or anything. The controller on my RBike is hidden in the frame somewhere so I would not be able to test/swap. You mentioned that the bigger battery would not necessarily give more power burst.. that gives me a little to go on as I assumed the larger the Ah the more powerful but not the case.. just lasts longer. I guess the real way to get more power is to switch to a higher voltage system...that helps me out. Figuring this thing out still (:

[Kocho]

To get more Ah at the same voltage, they either use higher Ah-rated cells or add an extra cell in parallel to each group of cells. In the 10Ah pack I guess you have 10 groups in series, each group made of 4 cells in paralle in the smaller battery, i.e.10s4p. The bigger battery may be 10s5p. 5 cells in parallel can provide 25% more current than 4. If the BMS is more powerful on the bigger battery, then you could get more power too, not just more range. But if they have the same BMS (limited to the same max current) you would not see the extra power. Does the battery have a label about what current it is rated for? For instance, my 52V battery, which has 14 groups of 5 cells is rated for 30A continuous and 60A peak.

Look at the ratings for the 36V Luna batteries as an example too.

https://lunacycle.com/36v-ebike-battery/

The 15 mph you are seeing is suspiciously close to the European 25 kmh speed limit for ebikes. I wonder if your kit came programmed with that limit... If the 500W bike climbs better than the 250W one, that would most likely be the case. But hard to compare different kits, because the motors could be wound for power or for speed or may or may not have internal gears ...

[MillerEbike]

Thanks for the info... the 500w kit climbs slower than my 250w RBike.. the 500w motor may be more tuned for a higher volt battery. I did not see any BMS rating on the battery but here is the info on the battery used for the 500w bike: The RBike (250w) did not have any specs on it. Anyways, thank you for your help.. ok with the function of the 500w kit but will look at a higher volt system for my next bike (:

36V14.5Ah New Frame ebike battery pack LG battery cells with charger

1. Rated capacity: 14.5AH

2. Voltage: 36V

3. Charging Voltage: 42V

4. Discharge cutoff voltage: 27.5V

5. 5P10S Li-ion 2.9Ah LG LGEBMG11865 50pcs battery cells

6. Continuous discharge current: 25A

7. Pulse/Max discharge current 50A

8. Max charging current : 5A

9. Charging temperature: 0~45

10. Dischargeing temperature: -20~55

11.Operating voltage:28V~42V

12. Diamesion:

13.Weight of battery pack About 3.9 kg

[Kocho]

25A is way more than the 500W motor should pull at 36V (the pack can supply continuously almost 1,000W, pretty much double the rated 500W of the motor, accounting for the fact that a 36V battery charges to 42V and then reduce that by a couple of volts, maybe 4, of sag at full load...). The controller or BMS might be limiting it. 500W should feel powerful and with the correctangle gearing on flat ground with 500W the bike xould reach over 20mph if not limiTed or defective.

Have you measured if your battery actually charges to about 42V? If it charges substantially lower before it stops, it might indicate cell imbalance or a faulty charger or BMS in the battery.

[MillerEbike]

Thanks for info.. you were right about the 20mph... Harry brought up a blue wire (slow wire)... the kit came with it connected, once I disconnected it I have about twice the power! Looks like my wife's bike outdoes mine now... time to build a new one and let my daughter have mine (: Appreciate your help!

[max_volt]

Looking at the rbike website the R6X (48V 750W) will do the fed max of 20 mph so whomever quoted 25 was exaggerating.

[MillerEbike]

Yeah and mine is the smaller version (250w 36v) is does about 14mph but still happy for the money I paid.. nice looking/riding bike but want more power (:

[HarryS]

On the amazon ad for this kit, the controller pictures show two blue wires marked "4 - lower speed wire", That's usually a speed limiter. If they're connected separate them. If they're not connected, then connect them. See what happens.

[MillerEbike]

Man, thanks so much! The blue wires come connected.. I disconnected and the bike runs under own power at least 20mph, no speedometer on the bike but I can tell based on my RBike. Again Harry, appreciate your input!