Best way for a beginner to build an ebike battery?

[Deville]

Hey guys,

So I have been thinking about it alot lately and I just cant seem to get the thought of building my own battery out of my mind, so I have decided its something I am going to do. I got a GM kit with external controller so I could build the bike up, understand how it works and now I am comfortable troubleshooting and repairing most potential problems that may arise, something I would not have got if I went with a manufactured ebike.

Now I want to be able to do the same with the battery. I have been searching and reading tons of topics about batteries here, Endless Sphere and at Pedelecs and although there is a ton of great information, most of it seems rather advanced for a guy like me that is new to it all. I seem to get a bit lost when it comes to BMS, cell balancing and all the different battery chemistries etc. Everything I read kind of gives me the feeling that lipo cells are probably not very safe unless I am totally sure what I am doing.

I'm running a 36v 12ah from GM now, so for my 1st battery build I'll be looking to build another 36v with 5 - 6ah. I feel this is a good starting point to learn the basics and after that I could advance to higher amps and volts and learn about different chemistries. Although I would love to build a 36v - 48v 20ah pack right away I'm not sure it would be the best choice for a first build...

I really just want to get a hands on understanding of battery packs, here is what I am after.

- I want to configure / connect the cells myself in both parallel and series , I am comfortable doing basic soldering and will buy cells with tabs if it's best.
- I want a plug and play battery just like the GM pack, one charger, one plug etc. I don't want to have to charge 2 packs for one battery etc.
- I want to understand how to incorporate a bms into the pack, and learn how to choose the right type for a given battery configuration.
- I want it to be safe, I'd like to think I have a fair bit of common sense but I also don't want to burn my house down or blow the pack up in my face.

I'm willing to shell out for some necessities such as a good balance charger, a bms, cells and whatever else I need but I would like to keep the cost under $300 for a good 5 - 6ah pack with my shipping costs.
 
Anyways, I know this is a lot to ask but if anyone could just give me some good tips, point me in the right direction, maybe a parts list or send me to a step by step battery build thread that doesn't involve serious technical skills and equipment that would be great.

I'm thinking about buying some Hobby King 5ah packs and working with those, or I have some 18v Dewalt battery packs but I think they are NiCd and only 2 - 3 ah.

Thanks for taking the time to read this, looking forward to any and all responses. 

[MAGICPIE3FOCUSPOWER]

It's cheaper to buy ready to run pack and modified to your own taste

I did mine 10 Ah 48V pack

[skylinenitro]

Or you can do cheaper Lead-Acids, so if they blow up, little lost.  You can do 48v 10ah with 4 batteries, no bms, no worries on special chargers, and they will not spontaneously combust.

Or 36v 10ah with just 3 batts, or 36v 20ah with 6 batts...

I have 2 packs on my bike, both lead-acid, 48v 17ah, and 48v 10ah.  If I run them together I get 48v at 27ah.

I normally run the 17ah pack alone and add the 2nd pack for extra range/tow ability.

Hope it helps, and good luck!  Just keep us updated

[MAGICPIE3FOCUSPOWER]

I hate lead batteries.
You have to use them all time or they will die, so for long term they are not cheap.

[skylinenitro]

Yeaaaaaa, and they are heavyier than a biscuit monkey.

I'm in your same boat, I want to build my own bms, but until I get a garage unit at my apartment, I'm limited to the kitchen table durning non-nomz times...

[MAGICPIE3FOCUSPOWER]

Yes I had several expensive Yellow Top batteries, they all died.
Because I forgot to use or trickle charge them.

O well I am happy with Lifepo4 now.....

Why building your own BMS?
It's better...or...?

[skylinenitro]

I want to build my own because I have a lot of the parts already, and I get cheep used lipos to use.

The issue is the lipos are used and some might die, so ill need safe protection from multiple faults.  Plus I don't have the cash to spend on a new bms...

[MAGICPIE3FOCUSPOWER]

Aaha yes then is a good option to to make your own stuff.
And increase your building skills

Yes I had some used Hyperion lipo's, they were almost round after one year storage.

[Deville]

Since I originally posted this I did a ton of research and reading and have decided to put the battery build on hold for now. Truth is, although I want to do it as a learning experience, I was also motivated to try and save some money in the process but it's really not alot cheaper to build your own pack then it is to just buy a ready made that comes with a warranty.

I almost bought Hobby King lipos to build a pack, so many times I was ready to commit to buying but never did. After reading about the amount of care required just to charge them, balance charges to buy etc etc. I said screw it. That seems to be going in the opposite direction of a plug and play solution like the GM batteries.

Then I started to consider NiCad due to the low costs, but like lead acid they are quite heavy and they just don't seem to have the C rates needed for ebikes, I don't know but either way I scrapped that idea to.

So I settled on Lifepo4 but I just cant seem to find any really good deals on them to justify building my own pack. Ideally I want to build a 20AH 48v pack but after spending literally hours upon hours looking for cells to buy it ended up that the price of buying cells, a bms, balance chargers, building or buying a case to put the pack in, anderson connectors, a key switch etc, etc. the savings are just not worth the time and effort for me, at least not now.

Eventually I will build a pack, but the prices need to come down a bit on Life technology first. For now I'll prob just buy a good 48v pack from somewhere reputable with a warranty and save myself the grief. 

Lead acid was never a consideration for me due to the weight, and poor cycle life. I'll update later if / when I ever do build a pack. I am still interested in hearing any advice, suggestions etc?

[StefaanC]

Look at http://www.yttrium-power.com/

[Hastings]

Don’t !
I do not think it is worth the trouble to build your own:  I had a lot of contact with Ping Li of Ping batteries one of the best builders as I had a lot of issues; some self-inflicted some not.
There are a lot of knowledge concerning performance envelopes of different cells and  of components in  BMSes where I needed advice and got it in a very satisfactory manner. Things that 
you  do not find on the net. Not to mention spares, most free of charge. I even had  offers of custom built batteries of other form factors (thinner, lighter to fit into the frame for better balance) So regarding batteries I rather pay  for function and  support