Battery packs - How can I get one cheap, or make one myself?

[olliemontague]

Hi all, this is my first post.

I've read a fair bit about electric bikes now, and am keen to get started with trying to convert one myself. The only thing that is stopping me is the high price of batteries. I've found conversion kits minus battery for around 100 dollars, which seems reasonable to me, but a decent battery pack seems to cost at least 200 or 300 dollars for something decent - and even these only have a few hundred cycles in them.

Can anyone recommend the best place to get a 24V 10Ah (or similar) battery pack that will last me a decent amount of time, and that will be compatible with most conversion kits?

Alternatively, can anyone give me some advice as to whether it's a good idea to think about constructing a battery pack myself? I've noticed you can get LifePo4 battery cells individually pretty cheap on ebay. Is it feasible to get a few of these, whack them together with some battery management hardware and then hook it up? If anyone could direct me to a 'make your own LifePo4 battery' tutorial that would be great!

Thanks in advance

Ollie

 

[neptronix]

Welcome.

Read about what it takes to get lipo going if cost is a concern. If you are willing to accept the risk that it entails, then you're golden.

I started out on lipo and don't regret it. On the other hand, i pay renter's insurance now... juuuuuusssstttt in case

 

[mike662]

Hi olliemontague,

Welcome to the forum! I know what you mean about batteries. The thing about them that I don't like is you never know what kind of cells you're going to get in a pre-made battery and you could end up dishing hundreds of dollars for something that won't last very long. So in my opinion, it's best if you take a couple of weeks to read through the stickied threads in the battery technology forum. This way you will learn what types of batteries are best for what applications, how to assemble your own packs, how to get the best performance/range (pick one ) out of them, etc. This way, you will not only be able to build a battery that matches your ebiking needs, but also do it at a fraction of the cost of a pre-made one and be able to fix things for cheap in case anything goes wrong, rather than replacing the whole battery.

I spent the past few weeks reading about lipo's and if you can accept the small risk that they may get into thermal runaway, then you can build an amazing pack with easily replaceable cells for around $200-$300. The technology used in them is much safer than it was 1 or 2 years ago, so as long as you don't overcharge, over-discharge, or smash the lipos you're golden. For many people, monitoring the overcharge and under-discharging is the only "hassle" of using lipos. But IMO, I trust my brain more than any electronic BMS.

Otherwise, go for LiFePO4. They're more expensive initially, weigh slightly more, are larger, and will give you less performance in the area of acceleration/top speed, but they do last a little longer than lipo and are as plug-and-play as batteries get.

I'll probabaly start a "rebuild" thread for my ebike that I'm upgrading, and in it I'll explain what I did with my battery system. So if you're looking at running an easy, cheap 20s2p lipo (that's ~74V, 10ah) solution, then be on the lookout for my thread. But to get you started, I'll list the items that I bought (a so-called "shopping list", which you can search for a specific shopping list for the type of pack you want to build to see if anyone has done the same before) but I'll leave you to figure out what everything is for and what to do with it all as that is too much to explain properly in one post.

Here's what I bought:
- 2 Meanwell (cloned) chargers which will be connected in series to charge to ~82V: http://www.ebay.ca/itm/160459985996?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649#ht_3835wt_905

- 5 of these to balance the cells while bulk charging: http://www.ebay.ca/itm/260753810568?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649#ht_3453wt_905

- 11 of these for a 20s2p configuration (bought 1 extra as a backup): http://www.hobbyking.com/hobbyking/store/__15521__Turnigy_5000mAh_4S1P_14_8v_20C_hardcase_pack.html

- and this to hold the batteries in (no room on my frame and it keeps them out of the cold): http://www.ebay.ca/itm/170647357372?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

- I'll still need some extra things like wire and connectors to connect everything together, but I haven't decided upon that yet

Well, I wish you luck on your search for the best battery ever!

 

[cassschr1]

If you build your own, by the time you get done, you will easily have have spent more building them than buying lipo to begin with. Been there done that.

 

[hjns]

If you build your own, by the time you get done, you will easily have have spent more building them than buying lipo to begin with. Been there done that.

I agree. The initial costs for a balanced charger, bulk charger, wire to create a harnass, connectors, shrinktube, and the lipos themselve, are high. I am in the process of doing it all myself, and find myself spending a LOT of money on this stuff. Definitely not the cheapest way. Flexible? YES! High power? YES! Lightweight? YES. So for me it is worth it.

 

[veloman]

You want to get rolling asap, right?

Get a plug and play LifePo4 pack/charger. Building a pack is for hobbyists, not people who just want something cheap. I am running 1.7c (peak amps)on 11ah of 36v LifePo4 and can easily go 25+mph. Later on you can think about other cheaper/powerful chemistrys like Lipo. $500 for an entry level kit with LifePo4 battery is a fair price and WORTH IT. Pedal bikes costing $100 don't move themselves, you're going to pay for power assistance. It seems everyone I talk to is taken aback by the cost of a decent ebike. Yes, $800 is what I spent building my bike, but it's more than worth it. Step into a bike shop and see what standard, quality bikes cost nowadays. What's a reliable car cost? A quality ebike is an investment, it just may seem hard since the total cost is nearly all up front. Imagine if when you buy a car you had to also pay 98% of the fuel cost for it's lifetime in addition to the price of the car.

Check the Used section on this forum for a LifePo4 pack - that's your best bet.

 

[amberwolf]

Even though I am probably one of the master repurposers and cheapskates around here, I'd still say you are much better off buying a premade pack. If cost is a concern, go with a Ping. Otherwise, go with a Cell-Man A123 pack.

Yes, you can build a pack yourself, but unless you already know just about everything there is to know about the batteries you intend to use to build from, you're probably going to end up buying the cheapest stuff with the best "promises" of specifications, and it probably won't do anywhere near what you expect it to, and be wasted money.

I've repurposed and reused lots of stuff, and am in the process of attempting an experiment with old used laptop cells, which I'm not expecting a lot from. :lol: Several poeple on ES have made working packs this way, and also from toolpack cells, but it's a fair bit of work, and unless you can get the cells for next to nothing and are prepared to spend a while learning about what you wnat to do with them first, and then more time actually testing and building, it may cost you a lot more than you expect.


It is possible to get both toolpacks and laptop packs for free, if you ask around at various places that recycle them, eventually you'll find one or more that will let you take them. But it could be a while before you get enough of them with enough good cells of the *same kind* to build a pack from.


If I had any money, I'd've bought a Ping bakc when I started this project, rather than using recyled old SLA. It would probably still be working for me even now if I had, unlike most of the SLA I've used.

 

[dogman dan]

Batteries are a dilemma if you haven't much cash. The cheaper choices are sometimes not so cheap, per ride.

Most likely the bargain of the lot is a 10 ah 36v lifepo4 from pingbattery. Currently close to $400 when you add the shipping to USA. And then you have the problem that it's capacity isn't so much, and it will only run the smallest ebike hubmotors. So you are limeted to about 15 amp controllers and smaller wattage motors.

A ping like I have, twice the size can do a lot of distance with 20 amp controllers and is very practical. But it costs more, Around $575 shipped.

So what can you do if your budget is only about $200. Not much. Either way youll have very limited range and half the lifespan of a nice pingbattery.

Sla's are one option. Really good ones will cost you, especially if shipped very far. Hunk a lead ya know. But this could be a usable option if you have a ride that short. Not much good if your plan is to pedal a lot, and use the motor only on a hill. Too much pedaling with 30 pounds of lead on the bike. About 6 miles of usable range. You really need to avoid discharging them all the way. Sla's about 50 bucks each or more for really good ones, 12 ah, plus about 30 for the charger.

Lipo may be the more practical route. A mere 5 ah lipo pack will put out the same watthours as you dare to discharge from 12 ah slas. Two 5s lipo batteries connected in series is 36v. Two 6s packs can be used for a bit more zip, and a fraction more watthours. You can get a pair of 6s 5 ah packs for as little as $100, and the cheapest of chargers for about $50. But I will recomend a slightly better charger, so you can charge faster. So even if you spend $120 or so on a good charger, you can be going on about $250 max. You'll have a very light battery, so you can still pedal a gearmotor to the hill, and just use the motor when you must. Later, as you get some money, adding more capactiy to the battery is pretty easy, at about $100 a pop.

Lipo does have some hazards, but they are not so hard to deal with. Just charge em in a safe place, and follow the rules at the bottom of each of my posts.

What would be the best thing to do? I still think save up for a larger pingbattery. A lot of $$, but it's going to give you a really practical bike with the range to actually go somewhere.

 

[cassschr1]

Somebody should sticki this thread,don't ya think. Lots of good info right up front. And its the truth.