Building Li-Ion battery pack

[senoritoriver]

Hi this is my first post! I recently got into the idea of an electric bike. My only problem is that battery packs are sooo expensive. I figured i could save some money by making my own pack. but as i've been reading, its hard finding a good charger, and balancing is a concern too. This will be my first time making a pack and i want to make sure i do it right. I'm wondering if i can make a pack with 3.7volt 3600mAh Li-Ion batteries. I want a pack that puts out 48 volts and atleast 12Ah. How cheap can this be done? Thanks

 

[motomech]

Little man of the river :lol:

Bueno...I mean ok,

With the price and quality of the Lipo[RC]packs these days, a bigger bang for the buck would be Lipo.
Buts it's not for everybody, but it seems like it might be you. You got be willing to spend time reading and learning, devote time to setting it up, time in care and feeding, pretty much like it was a baby, but instead of puking and pooing, it catches on fire[if mis-handled].

Seriously, four bricks of Hobbyking 6S 5000 mAh will get you 44.4V 10 Ah for around $200, a decent to very nice charging set-up for $150 to $200 and $ 50 misc. and you are in. Easy to expand later.
try reading some about it and consider it as an option

 

[amberwolf]

If you really want to build your own from laptop or toolpack cells, or similar, you are going to want to search ES for the various threads on how to do this, it's drawbacks, advantages, and cautions, as well as which kinds of cells are usable for your purposes. There are some really good threads about it, with arguments both ways on good or bad, so you can decide what you want to do.

 

[senoritoriver]

Building the pack seems fairly easy. but things like the PCB board and wiring a charger scare me away :| A wiring diagram would make this seem so much easier

 

[999zip999]

Buy a ping battery and learn about how it works and enjoy a bike. and then build a battery in your spare time as it takes some time to build a hobby battery or a battery as a hobby.

 

[amberwolf]

Building the pack seems fairly easy. but things like the PCB board and wiring a charger scare me away :| A wiring diagram would make this seem so much easier

The actual wiring for each different charger/etc. will be different, so unless you already have stuff to post pics and info of, we can't tell you which wires go where exactly. THus, there is no single wiring diagram to give you. First you have to decide what you want to build, and then what components you're going to use for it, and *then* we can help with a wiring diagram if the suppliers of the parts didn't give you one.

But in basic idea, they all wire the same: + of charger to + of battery, - of charger to - of battery. If you're using a BMS or monitoring system that actually cuts off charge current when full, then there's probably at least two - pads on it, one for battery and one for charge (and maybe discharge), so you'd use the second for the charger and the first for the battery.

Then there will be a number of "sense" or "balance" wires, and one of those will go to each cell-groups-interconnect point, where the + of one group connects to the - of the next most positive. Exactly which wire goes where depends on which BMS or monitoring system, so you'd have to show us which one it is before we could tell you how to wire it. There are diagrams for some of the popular ones in various threads about this kind of thing already, here on ES, but you'd have to search for them.


FWIW, "PCB" usually just means "printed circuit board", which could be literally any board in the battery or controller or charger, etc. So you have to specify which PCB you are referring to when asking how to wire it up.

 

[mistercrash]

If you plan on using Li Ion cells like the 18650, I strongly suggest you get a few used Makita tool packs from DoctorBass. The Makita tool pack contains 10 18650 Sony Konion cells. Usually you get at least 8 good cells from each battery pack, sometimes more. IIRC they are 10C discharge, chargeable at low temperature (down to -10°C), they don't need a BMS, nominal voltage of 3.7V and 1.5Ah. Read this thread
http://endless-sphere.com/forums/viewtopic.php?f=14&t=28285
read it and find out how to get the cells out of the Makita packs, how to group them by voltage, how to equalize each group before you can match the cells in parallel clusters and how to put them together as a complete battery pack.
In your case, you would need to build a 14S8P battery, that's 112 cells. So you would need to contact DoctorBass and reserve 14 Makita packs from his next shipment. The finished pack would be around 155 mm long by 115 mm wide by 140 mm high and weigh a little less then 12 pounds.
From my own experience building a battery with these cells, I suggest a good charger like the Hyperion 1420i and a nice power supply made from two server PS. Instructions found here on how to do it.
https://sites.google.com/site/tjinguytech/my-projects/diy-24v-47a

My battery is a 14S16P which I balance charge every night using the PS I built and the Hyperion 1420i charger. It's been working flawlessly and the battery always ends up perfectly charged and all cells perfectly balanced. You would be spending something like $200 for the charger and what you need to build a power supply but you will have that charging just about anything else you might get in the future.

 

[senoritoriver]

http://www.hobbyking.com/hobbyking/store/__9176__Turnigy_5000mAh_6S_20C_Lipo_Pack.html
to use these battery packs, what else would i need? what type of charger would be best, and what is the best way to connect the batteries? Ive seen nickel tabs, and copper wires used

 

[chilledoutuk]

ok as your new to this i recommend you get a pre made Y adapter that will connect two of those packs in series.

http://www.hobbyking.com/hobbyking/store/__18603__HXT4mm_Battery_Harness_14AWG_for_2_Packs_in_Series.html

If you want to run two of these packs in parallel and two in series then you could use two of these connectors

http://www.hobbyking.com/hobbyking/store/__18604__HXT4mm_Battery_Harness_14AWG_for_2_Packs_in_Parallel.html

You would need to change the connector on your controller to one of these also.

http://www.hobbyking.com/hobbyking/store/__9283__HXT_4mm_Gold_Connector_w_Protector_10pcs_set_.html

With regards to charging ideally an icharger capable of at least 6s charging is the best solution but at hobbyking they are out of stock.
The only charger they have in stock that's any good at the moment is the cell pro 10s

http://www.hobbyking.com/hobbyking/store/__14743__Cellpro_10s_260W_10A_Balancer_Charger.html

The cellpro as a charger is arguably better than the icharger but it only can charge it doesn't have any discharge or cycling ablity like the icharger does.

 

[motomech]

http://www.hobbyking.com/hobbyking/store/__9176__Turnigy_5000mAh_6S_20C_Lipo_Pack.html
to use these battery packs, what else would i need? what type of charger would be best, and what is the best way to connect the batteries? Ive seen nickel tabs, and copper wires used

Most consider this to be the best charger at the moment,

http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=23362&hilit=charger+li+po&start=30

 

[senoritoriver]

so lets say i used 4 packs wired in series and parallel to get 44.4volt at 10aH, how do i charge the 4 packs? do i have to wire them to a new charge link?

 

[chilledoutuk]

The easiest and cheapest way would be to charge all 4 packs in parallel after disconnecting the series connections (thats very important by the way) using a 6s charger.

and parallel charging board like this would work.

http://www.hobbyking.com/hobbyking/store/__15237__Parallel_charging_Board_for_6_packs_2_6S_T_Connector_.html


You could use a charger like the imax b6 ac its not super accurate but it is cheap.

http://www.hobbyking.com/hobbyking/store/__15237__Parallel_charging_Board_for_6_packs_2_6S_T_Connector_.html

the iCharger 106B-plus would be my preferred choice as its much more accurate and very versatile as a charger but you will need a power supply for it though

 

[senoritoriver]

what is the benefit of having a charger with discharge? (and to keep my batteries happy it seems like the charger/balancer would be best.)so to charge i would need a power supply, and a charger/balancer? And is there a way to charge without reconnecting the batteries in parallel?

 

[www.recumbents.com]

See:

http://www.endless-sphere.com/w/index.php/Building_a_LiPo_Battery_Pack

 

[senoritoriver]

So with the range i need, im thinking 10ah might not be enough. i need atleast 20 miles on a single charge. after some research, and pricing, my original idea came out to around $600 for everything. that leaves me around $200-$400 for improvements . so i need a 48v battery pack, bulk charger, balancer/charger, and possibly a power supply depending on the chargers, with connectors.(full set up) for hopefully around $500

 

[dogman dan]

Just get a damn pingbattery. Lifepo4 has twice the life expectancy of RC lipo from hobby king. Lowest cost per expected cycle on earth, if you buy from a trusted vendor with exemplary service after the sale such as Li Ping. My first ping lasted 3.5 years and took me 7000 miles. It would have made 10,000 but I screwed up and finally killed it.

This one. http://www.pingbattery.com/servlet/Detail?category=48V+LiFePO4+Battery+Packs&no=12&param_referer=http%3A%2F%2Fwww.pingbattery.com%2Fservlet%2FCategories%3Fcategory%3D48V%2BLiFePO4%2BBattery%2BPacks%26gclid%3DCNimncDl-K4CFQcFRQod3TTMwg&searchpath=177

With shipping, and a recomended 5 amp charger upgrade, it will be about $150 over your budget. But since you need range, you need a 48v 15 ah, and you need a chemistry you can run till it's 100% discharged and the bms shuts it off if you need to.

Believe me, for a no hassle commuters battery you can't beat the ping. The 48v 15 ah ping will take you nearly 30 miles if you ride 18-20 mph. 22 miles at 25 mph

Only if you needed the cheapest possible 5 ah battery would I recomend you get RC lipo. Then you would need the discharge rate of RC lipo. Or if you wanted to discharge at high amp rates to go 60 mph.

Get lifepo4 for a long range commuter.

 

[senoritoriver]

Could i just use this charger: http://www.hobbyking.com/hobbyking/store/__11170__Turnigy_4x6S_Lithium_Polymer_Battery_Pack_Charger.html each charging port will be connected to 2 battery packs wired in parallel. then when i put the pack back on the bike, and reconnect the series connections. would this work? or will i need a power supply also?

 

[leffex]

I just bought a 48v, 10ah bottle li-on -mn . up to 1000charges 2year and after that 70%.,goingto use it 80%DOD to keep it longer. will give me of 30minutes riding full speed or 1-2 hours at 50%

420dollars shipping included. 2a,charger included.ie 6hour charge.

aliexpress.com

 

[SamTexas]

If you plan on using Li Ion cells like the 18650, I strongly suggest you get a few used Makita tool packs from DoctorBass. The Makita tool pack contains 10 18650 Sony Konion cells. Usually you get at least 8 good cells from each battery pack, sometimes more. IIRC they are 10C discharge, chargeable at low temperature (down to -10°C), they don't need a BMS, nominal voltage of 3.7V and 1.5Ah.
...
My battery is a 14S16P which I balance charge every night using the PS I built and the Hyperion 1420i charger. It's been working flawlessly and the battery always ends up perfectly charged and all cells perfectly balanced.

The Konion cells you bought don't need a BMS (according to you), but you always balance charge your pack. So which is which?

Of course your cells are perfectly balanced, otherwise you wouldn't have spent money on the expensise 1420i charger, would you?

 

[senoritoriver]

After all the research i've put into lipo, it seems like they are designed for a different purpose. they have high discharge rates for short bursts. but i need range and ease of use. so lifepo4 seems like a better option for me. Safer, still pretty cheap, and long lifetime. the ping battery also looks good. I've spent a few weeks trying to find a way to cut corners on cost and i really ended up back where i started. hub motor kits. I found one i like with the specs i want, and the battery i want, and it'll still cost under $1000. i'm just gonna take some time to raise a little more money, and just get what i need.

 

[999zip999]

So with all the time we spent togethere what have you come up with ?

 

[senoritoriver]

Sounds like something my dad would ask! i came up with a cheap ebike kit and a ping or a kit from conhismotor.com although i havent seen reviews on conhismotor anywhere which worries me

 

[mistercrash]

If you plan on using Li Ion cells like the 18650, I strongly suggest you get a few used Makita tool packs from DoctorBass. The Makita tool pack contains 10 18650 Sony Konion cells. Usually you get at least 8 good cells from each battery pack, sometimes more. IIRC they are 10C discharge, chargeable at low temperature (down to -10°C), they don't need a BMS, nominal voltage of 3.7V and 1.5Ah.
...
My battery is a 14S16P which I balance charge every night using the PS I built and the Hyperion 1420i charger. It's been working flawlessly and the battery always ends up perfectly charged and all cells perfectly balanced.

The Konion cells you bought don't need a BMS (according to you), but you always balance charge your pack. So which is which?

Of course your cells are perfectly balanced, otherwise you wouldn't have spent money on the expensise 1420i charger, would you?

Sorry but I don't get what your saying. Are you accusing me of something? The konions don't need a BMS yes, not only according to me, according to a few people that use those cells. Some may use a BMS with those cells but I was told it wasn't necessary. I chose the 1420i charger, which is not what I call an expensive charger, more expensive then others maybe but it's a very good charger. And I got it because it also serves to charge my lipos and NiMh for RC helicopters and trucks my son and I have. Since I have the 1420i, why not balance charge my pack? I can keep track of how each cell is doing and make sure that the pack is in good shape.
Cells can still be out of balance even with the ''expensive'' 1420i. Again, sorry but I don't get your post towards me, might be some language barrier here but it sounds to me like you're quoting me to just discredit what I posted which is simply my experience with the konion cells up to now.

 

[SamTexas]

Ok, let me rephrase it: You said your Konion cells donot need a BMS, implying that they self balance, correct?

If that's not what you meant, forget the rest of this message.

Ok, so you said they self balance. You actually recommend them to people. But you balance charge them every night. Why?

Have you actually ever created an imbalanced pack, bulk charged it and proved to yourself that they ACTUALLY self balanced? I have, many times and they don't self balance.


http://endless-sphere.com/forums/viewtopic.php?f=14&t=34638#p506818

Many people on this board will tell you that Lithium-Manganese (aka spinel) will self balance when charged in series. My real life experience says otherwise. I deliberately created an unbalanced 3s1p pack (3.7V, 3.8V and 3.9V) and bulk charged them overnight using a 12.6V charger (4.2 * 3 = 12.6). This was what I got in the morning: 4.08V, 4.18V and 4.34V. No, no fire, no explosion.

 

[parabellum]

Many people on this board will tell you that Lithium-Manganese (aka spinel) will self balance when charged in series. My real life experience says otherwise. I deliberately created an unbalanced 3s1p pack (3.7V, 3.8V and 3.9V) and bulk charged them overnight using a 12.6V charger (4.2 * 3 = 12.6). This was what I got in the morning: 4.08V, 4.18V and 4.34V. No, no fire, no explosion.

1)Now wait few weeks or/and do few charge discharge cycles (80%DOD) and report results.
2)Do the same with other chemistry, report results.
3)Then learn and make conclusions on your "real life experience"

Those cells balancing works little different way.
Read this tread again for more understanding. :wink:
http://endless-sphere.com/forums/viewtopic.php?f=14&t=27702&start=15
specially LFP and flathill posts
EDIT