Booster Battery experiment

[trex]

you'll need some sort of BMS to limit the spikes and to make sure that the battery cuts out on low voltage (even with just one FET) and should also arrange your cells to 2P to balance the load.
There should be a good market for all in one 4V booster packs!

 

[KirstinS]

Well if I hook the Voltmwter up and monitor the voltage whilst riding then the BMS and LVC is, well, me I think !

I did have 8 cells in 2s2p but 1p died (4 cells at 3.7v 9ah) leaving the other 4 cells but one is bad meaning pack won't charge up properly

 

[manalog]

Hi Kirstin,
Im doing the same experiment as you, but with a 11V 10AH Booster, I have been commuting on it for more more than a week now no problems, range is 50miles.

Buy a Voltage monitor they are only £3 and hook it up to your Booster to monitor its overall Voltage and cells. I set mine to alarm at 3.4V.
See my thread for the wiring http://www.pedelecs.co.uk/forum/electric-bicycles/14841-8fun-kit-mod-48v.html. Thanks to your experiment I now have a pedelec I always wanted. By the way, Im also offering you some Samsung 2600 Li ons, they are ex Laptop batts if you are interested.

 

[KirstinS]

Thanks ! But credit is d8veh for walking me through it all

Glad yours is working so well! I certainly am missing mine at the moment

Sent you a pm

Sill bit unclear - if I wire in the voltmeter I have to the main + and - of the booster will I get total voltage ? Or just booster voltage ?

 

[Deleted member 4366]

I think that the best way to connect a voltmeter is directly across the booster pack, so that it starts at 12.6v, and when it gets down to 10v, time to stop. If you get one of those lipo alarms, it'll monitor individual cells, which is safer. If any cell goes down to 3v, it'll sound the alarm. You can make an extension lead to mount it on the handlebar, where you can see and hear it.:
1S-8S RC Lipo Battery Low Voltage Alarm Buzzer Indicator Meter Checker Tester UK | eBay

 

[KirstinS]

Hi, many thanks to d8veh for cells. I shall solder up packs tonight

Just to check the middle wire of the 3 on a 2s balance lead should go in between each s , right ?

 

[KirstinS]

This first pack I am soldering up as the previous one came ready made BTW !

 

[Deleted member 4366]

I thought you wanted to use a 3-cell booster pack for an extra 12v?

I'm not sur what you're saying above, but this is how I'd do it:
Solder 6 cells together with all their tops the same way up, so you have 1S6P
Do the same for the next two packs
Lay the three 6P packs end to end with the cells all pointing in the same direction,

Use thick wire (at least 14G) to join the top of one pack to the bottom of the next. Now you have 3S6P
Join the thick wire to the top and bottom of the whole arrangement to make the main power wires
Take your balance lead and join the first (-ve) wire to th bottom of the first pack
Join the second wire to the bottom of the second pack and the third to the bottom of the final pack
Join the fourth wire to the top (+ve) of the last pack
Make sure that the balance wires are the right way round for your charger to charge the right way.

Good luck to you and all who sail in you.

 

[KirstinS]

Well I was going to replace my 7.4v pack. But why not go higher

Thanks again , will report

 

[manalog]

Thanks ! But credit is d8veh for walking me through it all

Glad yours is working so well! I certainly am missing mine at the moment

Sent you a pm

Sill bit unclear - if I wire in the voltmeter I have to the main + and - of the booster will I get total voltage ? Or just booster voltage ?

I think you will only get the booster voltage.
If you wire in a balance wire and connect to a voltage monitor as D8veh has suggested you will see the pack overall voltage then cell1, cell2 and so on. The alarm is a bit unreliable you need to look at the voltages but it does give you a warning, mine is set to 3.4 volts but the alarm sometimes goes off at 3.85V during a climb on full throttle so my booster pack never go below 3Volts on any of the cells I hope.

 

[Deleted member 4366]

The alarm is a bit unreliable you need to look at the voltages but it does give you a warning, mine is set to 3.4 volts but the alarm sometimes goes off at 3.85V during a climb on full throttle

Are you sure your cells aren't sagging down to the alarm limit rather than the alarm being unreliable? Maybe you need to add another cell to each group in the booster pack

 

[manalog]

Are you sure your cells aren't sagging down to the alarm limit rather than the alarm being unreliable? Maybe you need to add another cell to each group in the booster pack

This could be the reason for the alarm but once I hear the alarm I switch off and just use pedal power. I might add another 3s2p and see what happenss.

 

[Deleted member 4366]

I think that you're saying the configuration incorrectly. 3s2p means 6 invidual cells (units) in your booster pack. You start with a bottle battery with 10S4P configuration. For a 20% increase you add a 2S4P pack to get 12S4P, but if the boster pack sags too much because the cells are inferior discharge, you add two or 4 extra cells to get 2S5P or 2S6P booster pack.

 

[KirstinS]

Made the new pack using d8veh cells

I decided against 48v as carries risk blowing things up. And I quite happy with performance at 44.4v

So made a 2s6p 7.4v pack which lives in saddle pack. Xt60 connectors to controller ad balance leads.

I have ordered a female 2s balance lead socket as it occurred to me the balance leads (2 of 3 wires anyhow can be used to plug into the permantley fitted voltmeter extension. Seems like a neat solution ?

Interestingly I've noted the ku65 controller I have will do 18mph hot off charger at 36v dropping slowly to 14 when nearly empty. So just changing that on an 8fun system makes a pretty big difference. The cost is reduced range

 

[manalog]

I think that you're saying the configuration incorrectly. 3s2p means 6 invidual cells (units) in your booster pack. You start with a bottle battery with 10S4P configuration. For a 20% increase you add a 2S4P pack to get 12S4P, but if the boster pack sags too much because the cells are inferior discharge, you add two or 4 extra cells to get 2S5P or 2S6P booster pack.

Hi Dave,
My Booster is 11V at 10AH and I am adding another 11V 5AH to bring total capacity of my Booster to 11V 15AH. In total including the Main Battery I am running 13S 10AH.

I am just reading some post and realised it looks like I am well over the 48V limit!!!! I thought by adding an 11V Booster I will be running my motor at approx 48V. Mind you I have not had any issues with overheating and my controller (original 8fun) is in my saddlebag. I'll watch out when we eventually get some good weather. No wonder Kirstin decided not to go above 7.4V.
Cheers,
Gerry

 

[manalog]

Made the new pack using d8veh cells

I decided against 48v as carries risk blowing things up. And I quite happy with performance at 44.4v

So made a 2s6p 7.4v pack which lives in saddle pack. Xt60 connectors to controller ad balance leads.

I have ordered a female 2s balance lead socket as it occurred to me the balance leads (2 of 3 wires anyhow can be used to plug into the permantley fitted voltmeter extension. Seems like a neat solution ?

Interestingly I've noted the ku65 controller I have will do 18mph hot off charger at 36v dropping slowly to 14 when nearly empty. So just changing that on an 8fun system makes a pretty big difference. The cost is reduced range[/QUOTE

Hi Kirstin,
The KU65 is interesting, I would like to know how you get on once the Booster is installed.
Cheers,
G

 

[KirstinS]

Ok, well d8veh supplied cells tested this morning- the grin is back does 24.5 no load hot charger. Did 22.5 in real world unassisted dropping to about 21.5 after first mile or two

4 personal bests on Strava of 5 segments (tool it easy on the first one)

7 miles later I have 7.95v on booster, started at 8.25v

Recharge at work took 2.5 hours

Already the pack is behaving normaly in a way tr previous never did. More and
More convinced I was sold fake cells

Will post pics of pack later - quite a neat solution given size (it's 12 cells vs previous 8 cells)

 

[Deleted member 4366]

I was thinking about booster batteries again, and remembered about the batteries I repaired. They were the type that goes behind the seatpost and had a small square BMS on top of the cells. These BMSs had 13 pins for 10 cells. The last three pins were joined together presumably because there's two redundant chanels, which are fully functional regarding max and minimum voltage control. This means that you could wire in your booster pack to the BMS as long as you use cells of similar spec to the originals. The BMSBattery chargers are adjustable, so you could turn the voltage up to 50.4v to have a fully plug-and-play booster pack.

Who's going to be first to try it?

Here you can see the connector with 13 wires.

 

[Deleted member 4366]

I had a thought about these booster batteries. Some BMSs don't cut off at minimum voltage so you're relying on the controller LVC, which is correct for 10S. If you go up to 12 or more cells, it'll be too low, so I'd recommend a real-time voltmeter to see what happens when your battery's flat. Stop if you reach 36v or you could damage your main battery. Most batteries have LVC in the BMS, but it's best to check that it's working.
http://www.ebay.co.uk/itm/DC-15120V-Wat ... 0896178943