I was going to build a DIY battery for another bike but rated continuous power of the new battery will be around 300w, it's a budget bike but I also wanted the option to upgrade the battery in the future which would allow for a higher power output. I already have allot of spare parts laying around for a 48v system because I already have a 48v bike and I could easily swap parts and batteries between bikes if they're both 48v (and I've heard high voltage systems tend to have a higher efficiency).

 

What I actually wanted is something like a 48v controller that can put out 500-1000w max but also has the function of setting a motor limit of 250w. Does anybody know if you can get them and if it adds much to the price? I'm not too bothered if it peaks at 250w because my current ebike seems to accelerate pretty well at that output and It can cruise along at 15mph using only using 150w.

???

 

Your motor is rated for 250 W nominative/continuous? It is continuous rated motor Watts which make a bike legal or not. 48 V is the maximum authorised voltage so you have no issues there.

 

Controllers are rated in Amps so you can have a 15 Amp or a 25 Amp 48 V controller. Your call, whatever you want as long as the above two criteria are met and your motor cuts out at 25 km/h you can chuck as many Amps at the motor as the battery and motor can handle without bursting into flames or melting. My Lipo is capable of giving 100 Amps x 37 V = 3700 W if the controller was capable of 100 Amps...

I was going to build a DIY battery for another bike but rated continuous power of the new battery will be around 300w, it's a budget bike but I also wanted the option to upgrade the battery in the future which would allow for a higher power output. I already have allot of spare parts laying around for a 48v system because I already have a 48v bike and I could easily swap parts and batteries between bikes if they're both 48v (and I've heard high voltage systems tend to have a higher efficiency).

 

What I actually wanted is something like a 48v controller that can put out 500-1000w max but also has the function of setting a motor limit of 250w. Does anybody know if you can get them and if it adds much to the price? I'm not too bothered if it peaks at 250w because my current ebike seems to accelerate pretty well at that output and It can cruise along at 15mph using only using 150w.

You sort of can. If you get a 'torque simulation' controller from BMS battery, it gives constant current at each of the three settings. I have a 250w/36v version. It gives 4/6*/16A on low/med/high settings when using PAS.

 

(I think it was 6A. Could have been 8A)

 

I would guess that the higher wattage versions give higher current proportionally.

 

 

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The controller for the 48 volt 350 watt Bewo can be set from the display programme setting mode from 7 amps to 25 amps. This controller and the display + the connecting cable are available as spares . You may have to research any suitability issues for different motors.

???

 

Your motor is rated for 250 W nominative/continuous? It is continuous rated motor Watts which make a bike legal or not. 48 V is the maximum authorised voltage so you have no issues there.

 

Controllers are rated in Amps so you can have a 15 Amp or a 25 Amp 48 V controller. Your call, whatever you want as long as the above two criteria are met and your motor cuts out at 25 km/h you can chuck as many Amps at the motor as the battery and motor can handle without bursting into flames or melting. My Lipo is capable of giving 100 Amps x 37 V = 3700 W if the controller was capable of 100 Amps...

 

 

The spare motor I have and the motor/kit on my main bike are rated for 1000w but I've had no issues with the police on the roads... that's because I don't go any faster then 15mph and tend to keep my power draw below 300w anyway which doesn't draw much attention (the bike can cruise at 15mph using 100-150w or even as low as 60w with a backwind), plus it increases range and puts less stress on the batteries and other components (none of my ebike parts even get warm). I only really use the extra power and speed if I feel like I'm in danger for some reason (like pulling out of a busy junction). I reckon the police would only take action if you're riding like an idiot and/or you're making it blatantly obvious that the kit is overspecced.

The controller for the 48 volt 350 watt Bewo can be set from the display programme setting mode from 7 amps to 25 amps. This controller and the display + the connecting cable are available as spares . You may have to research any suitability issues for different motors.

 

 

Do some motors not work with certain controllers? it's a 3 phase motor with 3 hall sensors, one of the hall sensors need replacing which is why I have a spare motor... the original seller sent me a replacement, but I'm pretty confident now that I can replace the faulty hall sensor on the original motor

Do some motors not work with certain controllers? it's a 3 phase motor with 3 hall sensors, one of the hall sensors need replacing which is why I have a spare motor... the original seller sent me a replacement, but I'm pretty confident now that I can replace the faulty hall sensor on the original motor

 

 

You can get controllers that will run without sensors. Most of the ones I use are like this, less to go wrong.

48 V is the maximum authorised voltage so you have no issues there.

 

Actually its 60V to stay within SELV (Safety Extra Low Voltage). 48V is a standard as it also keeps the boost charger voltage (typically 57.6V boost, 54.5V float) within SELV as well.

I am talking about a legal requirement to meet EN 15194 - 48 V maximum legal voltage.

Got you. It's 60V for CE.

Just a thought but another factor in the the equation is the wattage that the battery is able to supply. If you exceed the batteries ratings, you could be in for a world of hurt.

 

I am new to ebiking so could have missed a trick(or two)

Just a thought but another factor in the the equation is the wattage that the battery is able to supply. If you exceed the batteries ratings, you could be in for a world of hurt.

 

I am new to ebiking so could have missed a trick(or two)

 

Not generally an issue...lithium ion batteries are capable of at least 50A discharge which at 36v equates to over 1,500W. The speed controllers usually have power devices inside which are rated considerably less. So in essence that battery is one of the strongest links in the chain, certainly in terms of current capability.

Not generally an issue...lithium ion batteries are capable of at least 50A discharge which at 36v equates to over 1,500W. The speed controllers usually have power devices inside which are rated considerably less. So in essence that battery is one of the strongest links in the chain, certainly in terms of current capability.

That's not correct. Most lithium ion batteries are limited to about 1.5C, meaning that a 10ah battery will be limited to around 15A (around 600w) by its BMS. This is to protect the cells from damage.

 

Lipo has a much higher C rating.

 

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Thanks for clarifying guys. I would guess that its down to the amount of cells in parallel , which will determine what the max draw rate is.

 

Poor(er) quality batteries, would provide less without damaging the underlying battery cell.

Modern Samsung cells in the 15ah HL/08 and newer Dolphin/09 batts have 28a bms protection so nearly 2c rating and some 3c now.. Lipo's very in quality on ES the experienced guys who test their cells reckon that for cheap cells sold by HK then to take the ratings with a pinch of salt and allow about a 1/4 of their rating, even so my 10c multistars hold up well and sag rates seem to be 0.3 -0.6v under load.

Thanks for clarifying guys. I would guess that its down to the amount of cells in parallel , which will determine what the max draw rate is.

 

Poor(er) quality batteries, would provide less without damaging the underlying battery cell.

Yes, that's how it works, and that's why we use the the 'C' rating, because it relates the capacity (Ah) to current (A).

 

The ratio is the same, no matter how many in parallel. The max discharge varies with the total capacity.

 

So a 10Ah battery at 1.5C will give 15A. 20Ah will give 30A.

 

Lipos have massive C ratings in comparison. 50C and more, so they can deliver massive current from small capacity batteries.

 

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