Cycle loosing power

[BikerToCycler]

So i have a 48v 1000w kit, cheap bought off ebay.

I got a good quality new dolphin style 48v 10.4ah battery which has 25A continous rating paid £240 direct from china, however the bike seems to reach a limit where it suddenly looses all power to the led display/motor until i release the throttle and it comes back.

Further to this sometimes the motor trips the battery safety and i need to plug it in to restart the battery which is not an option if i am out, i was riding solo throttle and think i was stalling the engine causing the cut out.

Just looking for some of the forums wisdom on what could be a solution to these problems.

 

[BikerToCycler]

I should add, all problems occur when riding. If Wheel is free spinning i can run the motor and never had a problem.

Seller blamed the 25A rating on the battery but i though
48x25 1200w was enough

 

[Deleted member 4366]

How many amps is written on your controller?

I doubt very much that your battery can give the current that your controller tries to drag out of it. When the controller switches off and then comes back on again, it's probably because, the battery has sagged below the controller's LVC. When it goes off and won't come on again, it's because you've gone below the battery's LVC.

 

[BikerToCycler]

The controller has nothing written on it at all just a plain silver box.

I was wondering if it could be speed limited but it doesn't seem to have a problem when the wheel is just spinning in the air.

The not coming back on i can reproduce by putting full power on while holding the brake it instantly turns the battery off so i think i need to avoid trying to go full power too quick

Should i look at buying a better controller or a BMS that can handle 30A as suggested by the battery maker

 

[Alan Quay]

The controller has nothing written on it at all just a plain silver box.

I was wondering if it could be speed limited but it doesn't seem to have a problem when the wheel is just spinning in the air.

The not coming back on i can reproduce by putting full power on while holding the brake it instantly turns the battery off so i think i need to avoid trying to go full power too quick

Should i look at buying a better controller or a BMS that can handle 30A as suggested by the battery maker

As d8 says, sounds like the battery is not up to the job. 25A from a 10Ah battery is a lot to ask unless it has special cells, which is doubtful.







Sent from my HTC One_M8 using Tapatalk

 

[BikerToCycler]

Thank you all for the help the cells are advertised as samsung 26F cells although i will try to take it apart to test.

I bought on aliexpress and so i will be able to make a claim and receive a refund if the batteries are not what they are claimed and or the battery does not put out 25A continuous.

I am having a problem getting the housing off and don't want to damage it anybody had experience taking apart this style of battery

This is the same item as the one i bought
http://s.aliexpress.com/MNN3EFFr

 

[BikerToCycler]

2600 mah 3.7v 5.2 A are the specs for the 26F i found online.

13s4p would get me the 48v and 10.4ah

So that gives 5.2x3.7/48 x13x4 i think this is how you calculate this?

Thats 20A and so this is definately my problem the motor seller told me the motor and controller are rated 25A

Now to talk to the seller, thank you all for the help any suggestions of someone in UK who can build batteries? I would give it a go but don't have a battety spot welder and would love a triangle bag with ~20ah 48v

 

[Nealh]

Apparently Woosh sell a 10.4ah 30a rated bottle battery or search for Insat Intl in London on the forum as they come highly recommended, several pedelecers have used their services.

 

[BikerToCycler]

One last bit of advice, seller is offering a free 30A bms but i dont think this will solve the problem as the cells have 20A peak output. Am i correct?

 

[tommie]

In this case i`d cut my losses with the chinese, they`ll probably tell you to return it for a refund or similar - just check the carriage cost for that alone!!?

Best bet is to get it re-celled at Insat, they use premium cells and you can discuss with them your needs.

 

[BikerToCycler]

Aliexpress offer a guarentee of partial refund if not as described i have had an offer of £30 from him but i asked for £50 i think at £180 the battery is a bargain as its actually really well made just 20A instead of 25A continous as he described

In terms of recell do you mean just get them to add an extra 13 batteries in 13s5p? Will it fit or will they replace all my brand new 26F batteries i can image that to be expensive

 

[Deleted member 4366]

Upgrading the BMS won't help because your controller will switch off instead. Put a voltmeter on the battery wires to see what happens when you take full power.

The maximum discharge current for a Samsung 26F cell is 5.2 amps. You have 4 in parallel, which makes 20.8 amps max. 1000w controllers are normally around 25 amps. That's your problem in a nutshell.

 

[BikerToCycler]

I am learning on the go and i worked them figures out too although i thought 5.2 is the safe current not max as it can go full power just not sustain it and eventually cuts, the seller knew very little about batteries and kept saying the cells are not important its the BMS which i knew was BS either way i now have managed to get the partial refund so will get a 750 w motor for my next build which will go perfect with this.

Thanks for the help i will try contribute to this forum as i learn more and start building better bikes.

 

[Deleted member 4366]

It'll work OK if you cut the controller's current down.

Show some pictures of your controller, and, if possible, open it up to show what's inside. It should be very simple to modify.

 

[BikerToCycler]

http://imgbox.com/kKQtxygK
http://imgbox.com/Bhq1tuWI
http://imgbox.com/KVfbR0FM
http://imgbox.com/Ja5jzZGO

 

[BikerToCycler]

It'll work OK if you cut the controller's current down.

Show some pictures of your controller, and, if possible, open it up to show what's inside. It should be very simple to modify.

 

[BikerToCycler]

So had a read around and seen another of your posts mentioning you shaved the shunts. So googling found out what a shunt is. Located mine and shaved (20% of the shunt) hoping for 25>> 20

Resistance before shaving was around 3ohms after was 4.5 so i shaved abit too much maybe but the readings were not very reliable anyway.

So i test by holding break and pushing full throttle the bike nearly shot through my neighbours bedroom wall!! How reducing the Amps results in such crazy power gain i am unsure. However it now hasnt cut out i will test it out and hopefully it stays working

Thank you for the help

 

[Deleted member 4366]

Excellent result then. The two shunts are the same, so you could have cut one to reduce the current to 50%, then add solder to the other one to bring it back up to the minimum power that you would be comfortable with. Shaving or crimping the shunts works too.

Whatever power you have now, you're probably still pushing the battery harder than you should if you want it to live a long time, so consider reducing the current a bit further as long as you have enough power.

 

[anotherkiwi]

What LCD do you have plugged into the controller? There is means of reducing Amps out in the C configuration section of the common LCD-3's. My 15 Amp controller is tuned down to 12 Amps because I don't need the extra Watts for the time being (I'm quite fit) and I am looking for extra range from the battery.

 

[anotherkiwi]

So i test by holding break and pushing full throttle the bike nearly shot through my neighbours bedroom wall!! How reducing the Amps results in such crazy power gain i am unsure. However it now hasnt cut out i will test it out and hopefully it stays working

I would say that before, the controller was spending more time handling the lack of sufficient Amps from the battery situation than it was supplying what it did have to the motor.