Booster Battery experiment

[KirstinS]

Hi all

I'm going to try use a booster battery pack solution to get increased speed from my 8fun kit. There is so much info on ES that I got totally lost.

I hope this thread can help others choose to do this (or not if it fails utterly). If it works then Its very cheap as I've spent £63inc shipping (excluding the ku63 as I didn't actually need it - I now have 3 controllers )

Happily d8veh came to the rescue and provided a shopping list so I now have (and see picture)

An 8 cell Panasonic 18650 pack welded by supplier into 2s4p for 7.4v and 9ah. This is an exact match for my 9ah 36v bottle battery

A charger

Some balance leads

A wattmeter (waterproof)

A ku63 controller (restriction optional)

What I don't have is the first clue about soldering the balance leads to the pack do I can charge it .

Help please ?! I can solder I just have never used balance leads or balance charged

Also watt meter is to check cells are decent natch and not fake.....but not sure how to isolate the booster pack. Or maybe just keeping track of total voltage is enough ? ( main and booster nominal is 44.4v )

Thanks !

 

[Deleted member 4366]

Balance leads:
I need to check which way round the connector goes if you can wait a couple of days til I get home. The idea is that one wire goes to the flat end of the first cell ( group of 4). The next goes to the other end which is the same as the flat end of the second cell because they're joined, and the third wire goes to the domed end of the second group. So, one wire each end and one in the middle. You then connect the balance connector to the charger and it should show the cell voltages at about 4v ready for charging.

Sent from my GT-N7100 using Tapatalk 2

 

[KirstinS]

Thanks vm d8veh- i can wait no probs

I think I have the wrong leads anyway though as mine have 4 wires and may be for 3s ?

 

[KirstinS]

I've ordered some 2s to be sure

 

[banbury frank]

Hi Are you trying to turn your 36 volt battery into a 48 volt if so you need a 48 volt controller and a 48 volt charger you will increase the range and the top speed

Looks Good to me

Frank

 

[KirstinS]

And the welding looks like this






And frank , going for 44.4v (main plus booster ) got two chargers. One each pack

 

[KirstinS]

Here is finished booster pack (bar a bit if reinforced tape and tidying up)

 

[Deleted member 4366]

Here is finished booster pack (bar a bit if reinforced tape and tidying up)

View attachment 5722

The main wires will be giving 15 amps or more, so should be as short as possible and 14g if you can get some. It's difficult to see from the photo what you used. Thin wire will waste power and prevent current getting through.
14 AWG Black Red Silicone Wire 2m Lipo Battery Cable | eBay

 

[KirstinS]

Thanks - i used an old 8fun power cable so should be fine for 15a

I intend to replace bulket connectors and will shorten too. Not quite sure where to mount yet so will leave as is for testing purposes.

 

[KirstinS]

Finally I got my main battery working again (mostly thanks to d8veh)

So I loosely hooked up main to booster pack . Main on 37.8v (not fully charged obviously ) and booster on 8.2v (also not quite fully charged)

Got 46.2v from both together

No load speed test (its late and pouring with rain) gives 19.8mph on the cycle computer. Should get bit more in full charge

For comparison no load at 37.8v was 16mph. My cheap cycle comp tends to underestimate by 1/2 to 1 mph vs a GPS

This is using the 8fun controller at present which is restricted. I hope when I change it over to ku65 with the restriction disconnected I may get a bit more

Real world test tomorrow with full Charge and 8fun controller

 

[Deleted member 4366]

Don't get a KU63 just yet. When I was in China I met a guy who said that he can get me 18amp controllers with nice LCD display that shows volts and current. I'm just waiting for a price.

 

[KirstinS]

Hi d8veh

Too late - already have the ku65 in hand! No worries - just hope the real world test goes well

Here it is - controller and extra wire inside the water bottle. Booster battery in the black pack under seat (just for now)

 

[KirstinS]

Yeeeehhaaa!! !!!

I have never been so happy to arrive at work.everything worked a dream. Bike is much faster top speed and accelerates faster. I took it easy and used in bursts, also was very gentle over first mile or do

Even so it did 19.5 on throttle and easily assisted up to 20mph. Speedo never dipped below 17 unless stationary except one small hill which I did at 15mph (usually around 10mph)

Shaved several minutes off commute as well. Brilliant

4 personal bests without trying and 16.4mph average . Normally around 12/13

 

[KirstinS]

I think I killed the booster pack !

Wired in a ku65 last night

All fine but power dropped off after 15 miles commute (7.5m each way)

Now one of the series packs of 4 cells seems dead . 1s reads 3.42 and the other 0. Ad each cell in that S also reads 0

What went wrong ??

Main pack seems fine and reads 36.3v

 

[Deleted member 4366]

You've got no BMS on the booster pack. You must monitor its voltage until you're sure you know how it behaves. The main pack at 36v is nearly empty. Your booster pack cells must be a bit sub-standard - probably fakes. If you pm me your address, I'll send you some more cells, but they're only about 1500mah or less, so you'll need maybe eight in each string to make sure that it doesn't go down faster than the main battery, which means that it'll be twice as big as before. I'm wondering whether your controller is giving a higher current than 17 amps, which would account for your lower range.

 

[KirstinS]

PM sent - many thanks

I did monitor before and after each ride. Had been fine till today - never went above 4.18 or below 3v

If a cell fails does it take the ret of the series with it ?

I've gone back to eBay seller advised of the cell failure and how I used and charge the batteries. I then politely asked what may be done about it. You never know.....wont hold my breath though.

 

[manalog]

Hi KirstinS,
I'm doing the same Experiment (48V version) after reading this thread, I'm wondering how you are getting on. Are your Batts up and running again? I know D8veh has offered you some spare batts, if you need some Samsung 2500s PM me I have some spare.
Gerry

 

[mountainsport]

Balance leads:
I need to check which way round the connector goes if you can wait a couple of days til I get home. The idea is that one wire goes to the flat end of the first cell ( group of 4). The next goes to the other end which is the same as the flat end of the second cell because they're joined, and the third wire goes to the domed end of the second group. So, one wire each end and one in the middle. You then connect the balance connector to the charger and it should show the cell voltages at about 4v ready for charging.

Sent from my GT-N7100 using Tapatalk 2

Hi d8veh,

When you get back can I borrow your brains for a little bit?

MS.

 

[Deleted member 4366]

Always happy to help, but if you post a new thread, anybody will be able to help.

 

[KirstinS]

Sorry, I've been away for a couple of weeks.

So, the short answer at first it worked fantastically. But then i killed 1s of the pack. So I removed it and my booster pack became a tiny 3.7v

And today I killed that too as one of the cells just would not charge beyond 3.65v even after 12hrs

So essentially two things happened
I think

1) I was ripped off with fake cells by Chinese seller

2) I failed to use the voltmeter when using the bike. Although I tested before and after every ride as well as before/after/during charging

D8veh cells are due to arrive in next few days. Many thanks indeed !

I bought the wire to solder up the packs already.

This time I will wire in voltmeter - although I'm not sure how to isolate the pack voltage from total voltage?

Thanks