My first BUDGET e-bike attempt, please help

I have recently been trying to make my e-bike dream a reality, I purchased a 48v 1000w rear hub motor from YXM corp off eBay (item number: 130328433770) I have had no problems installing it however there is one final problem, all together the kit cost me $319 and i now have everything but they batteries. i have around $180 to spend on batteries. Clearly this isnt enough for a lifepo4 battery and im starting to think that SLA's are my only option. As it is my first e-bike i am not really too keen on spending $700 on ping batteries straight away as i am only 17 and cant afford that just yet haha I have seen some alright SLA's (again, on eBay) for my $180 budget, they are 4 - 12v20Ah which would give me the required 48v and a decent 960watt-hrs. Just curious as to the range i can expect from this sort of set-up? If anyone has any suggestions as to how i can maximize range and top end speed without spending more than $200 i would be very grateful to hear from you!

Hi Joe, welcome to the forum. I understand your issue with spending that kind of money for a battery. But i'm still going to repeat (as others are bound to anyway) what the main difference is between a Ping battery and SLA. A 48V 20AH Ping weighs about 20 pounds and 48V 20AH of SLA will weigh close to 60 pounds. Plus the LiFePO4 will perform much better and last about three times as long (or more).

Depending on your speed and distance goals you might be better off with 12 AH of SLA at about half the weight (and maybe less money) with the idea of getting a Ping (or?) when you can afford it.

Let us know your bike type, speed and distance goals, type of terrain, etc. and someone will probably make some better recommendations.

Good Luck with your project.

Thanks for such a prompt response Rassy! My bike is a front suspension Saracen N-Zyme. I will be using it mainly for distances under 20km on medium gradient terrain, As I have bought the 1000w motor so I would like to utilize the speeds of around 45-55kph if possible with SLA's.. Maybe you're right about the weight to amp-hour sacrifice and I hope to upgrade to lifepo4 within 12-18 months.

Because of Peuketts (sp) effect, your SLA's only give you about 60 percent of the battery rating.
So 20AH gives you 12AH usable power. Lipo gives you almost all of it's power.

When I used 7AH SLA's, work was 8 miles away. I could get there doing 20mph but the batteries were dead by then and I had pedaled my ass off. If I slowed down to 15mph, I got to work with dead batteries and only pedal moderatly.

If you want SLA untill you can afford Lipo then buy 7ah for about $20 each

If you buy a CA or braindrain you'll be able to see how many amps your using and see the effect of your pedaling. It's hard to budget your power if you can't see what's happening.

When I went from SLA to Lipo I told my girlfriend she was no longer my first love, my new battery was!
That sums up the differance betweeen the battery types.

Hiya Joe... Ya can also look in the Garage:
http://spreadsheets.google.com/ccc?key=0AtT_x6_Q73cmdHBINWR5R283VzVQNVhEeVlBTE9XY2c&hl=en

Pick out the folks that are riding similar powered motors at the kinda speeds and range yer interested in and ya can see the sorts of battery packs they are using... Even if they are riding nickel or lithium flavoured batteries the pack size in Whs (V x Ahs) will give you a rough idea of the amount of energy storage you would need to accomplish your desired objectives... There are a lot of factors at play:
http://endless-sphere.com/forums/viewtopic.php?f=3&t=15069&start=0

Good luck
Lock

I would say 4* 20Ah battery is way too heavy for an ebike. I have 14Ah SLAs and they are more than I would be happy to put onto a bike already. I promise you that once you pick up the parcel with 4 20Ah SLAs inside you will not be keen to strap them on a bike. If you can find a way to put the batteries in the frame it will be much better. All that weight on top of a rear carrier is not nice.

Also don't be tempted to buy the very cheapest LiFePO4 pack you can find on ebay. Many people who have, have not had much success. Better to stick with a recommended supplier. Best of luck with getting it sorted.

Listen to the good advice you have here on this post, one thing I will caution you too, SLA's can dump current like crazy, but also break the rear rack before you notice it. We had a 18AH and two 7AH SLA's in series on my dad's bike (our first E-Bike project) not realizing how much of a chance we were taking (the high battery can drained into the lower battery and fry it in the process ) and thought it weighed 34lbs, we thought it was pretty nice.

Then one day I realized that unless I was on the throttle constant, that the E-Bike was actually MUCH slower than just a plan pedal bike because of the extra weight and resistance created by the DD motor!

I would grudgingly say get 12AH SLA's since you have to fit a budget atm, but if your at all able to do so, just save up that $180 and get a good LiFePo4, you can get one for less than $700, but you might have to do some soldering building it out of individual cells or like many of us, use Dewalt batteries with a special circuit board made by kfong on this board. I have about $550 - $600 into my battery set-up, and it's got a lot more in "sweat - equity" but, it can be done.

I routinely use 3x 17Ah SLA at around 45 pounds for CrazyBike2, which is a pretty heavy bike by itself at around 80 pounds, plus a 15-20 pound motor+gearbox, and got about 30-35 Wh/mile out of it. It's front suspension only, hardtail. It took that weight without breaking the frame, but definitely breaking rear wheels on potholes and such, too often to deal with easily.

I'd say that 4x 20Ah batteries on any normal bike frame is pushing it, especially if you end up mounting them A) higher up in the frame and/or B) distributed any other way than 2 in front and 2 in back.

I tried mine in a few ways in back before moving them to the central frame, and it basically made the bike truly rideable to put them there instead of all in back. If I had had 4 of them (I do now) I'd've probably put two on the front end (not on the wheel) as low down above the fork crown as I could, so it would clear the fork/wheel and be fixed to the frame. Then two in back in front of the cargo pods (like I started with), or just two where they are right now in the central frame. Then I'd have better bike performance when loaded with cargo in back, and a lot less broken rear wheels.

20Ah batteries are also fairly large, and finding places to put them on a bike frame is challenging at best.

As others have mentioned, keep Peukert's Law in mind, that the faster you pull the power out of the batteries the less power you will get. If you actually use the potential that 1kw motor has, a lot, you'll not have a lot of range even with big SLAs, and with small ones you'll have much less than you expect, since it's not a linearly shrinking range vs smaller batteries with the same power draw from the motor.

You won't know for sure what Wh/mile rating you'll have with the bike until you've built it, but you can guesstimate based on it's weight, gearing, desired speeds, and terrain, with some of the various calculators around the web. The higher that rating ends up, the less range you'll get.

Weight is a big factor when it comes to starting from a stop or climbing any slopes (even small ones, especialy if they are long). At some point, having bigger heavier batteries is going to have *worse* performance than smaller lighter ones.

FWIW, I don't much enjoy most bikes that have more battery weight than the rest of the vehicle weight. My first successful ebike (meaning it was actually useful) was DayGlo Avenger, with 3x 12Ah batteries plus a couple radiator fan motors and metal baskets and stuff, and it was quite heavy. I've forgotten exactly how much it weighed, but I think that the motor+battery system all told was at least as heavy as the bike itself.

CrazyBike2, my next successful ebike, is 150+ pounds, with at least 1/3 of that being the motor+battery system. It performs a lot better than DGA did, but it would be far better with something other than 45 pounds of SLA on it.

Lithium is fairly expensive. NiMH and NiCd less so, but still significantly more than SLA. If you just want to get the bike going, SLA is a good learning system if for no other reason than that they are cheap and they are pretty good at taking abuse as you learn.

Seems to be the general consensus, and i agree, that the 20Ah batteries would be a little too heavy!

I would love more than anything to go lithium, if i were to get a lithium in the future what size would i be looking at? and how much is that likely to cost me? i can afford to put $30/week to this project as a maximum so do you guys (and girls) think that i should save my $180 a wait 17 weeks until i can afford lifepo4?

Me and my friend are going on an 8 day cycle trip (with overnight charging possible) in Mid-April and the thought of speeding past them on the hills without them realizing how is really cool

suppose what i really want most is just a way to try it out without investing the big bucks straight away, ive never had more than $500 in my account at any one time so these numbers are very daunting but im really getting into the hobby (unfortunately haha) Thanks for all your responses so far, it was great to wake up today with such insightful and helpful comments Joe.

Ooooh waiting 17 weeks at age 17 is way too hard. And 20 ah sla's are way too heavy. So get some sla's. 12 ah should get you the distance you need, but maybe not quite at full throttle. With sla's you lose a lot of your cycles if you drain them too deep. So if the pack will go 12k you need to keep it down to 8 or 9.

Don't buy em on ebay. There is a history of scammers who sell you old recycled sla's on ebay. Mabye still good to keep a computer running a few minuites during a power outage, but not good for a bike. Look for them on line at places that sell wheelchair and mobility scooter batteries. Shipping sla's is pricy, so buy close to home as possible. The sla's will last long enough to save up for a ping or other lifepo4 if you treat them nice.

Nothing wrong with starting out with sla's, they'll teach you to ride without wasting your watts.

Good advice from Dogman. 4 * 12Ah is enough weight wise for sure and they are a bit smaller so it would be easier to fit them somewhere other than just on the rear rack. I bought 4 * 14Ah SLAs just to try something while waiting for some batteries. With them strapped to the rear carrier it was not a pleasant riding experience I can tell you. Keep the weight as central and low as possible, it will help massively.

Check the yellow pages (phone book of businesses) for a local supplier of electric weheelchairs. Call them and ask where the local deep-cycle SLA supplier is. In my town its a national chain called "Batteries Plus".

Im young and not using this bike for commuting really, suppose i was to full throttle it (as all men love to do!) on 12Ah SLA's, whats a reasonable speed & distance i can expect without killing my batteries so much they only last like a week sorry for all the amateur questions p.s i contacted them and managed to find a supplier of 48v12Ah for $130 free shipping. Is this a good deal?

Not sure about range (maybe 8-10 miles at full throttle?)... but most local battery suppliers sell 12V/12AH batteries for about $40 each. If someone is offering them for $130 (total) shipped, I would question the quality. But if you want to save a few bucks... go for it!

From what I have read and been told, if you buy online, buy Power Sonic batteries. They are used by many and I have looked at the datasheets and they have significantly higher discharge rates than other SLA batteries. I use 7ah batteries, but I am only expecting and needing a 10 mile range, 5 miles one way with a top off during work.

My whole day is seeming to revolve around battery hunting

BrandonB: I managed to find some power-sonic's - 48v 12Ah for $150 incl. shipping. weight = 15.4kg (34lbs)

The bike is quite light at only 14kg (30lbs) and i dont weigh a huge amount, 70kg (154lbs). I dont mind pedaling at the same time (mid-effort, just before breaking a massive sweat) .. how much is this likely to improve my battery life compared to if i was only using the throttle? I think i might get the SLA's for now just to get the bike actually moving and in the mean time just be saving like mad for the lithium. Did anyones else go straight to lithium on their first build?

Maybe I missed it if this was mentioned already, but if you do settle for lead acid batteries for the time being, you need to charge them right after the discharge. You can't ride somewhere and let them sit half discharged for a few hours because they might not even last 12-18 months.

I saved and waited a few extra months until I had enough for lithium. My bike feels like a tank w/ 9kgs of battery weight. I couldn't imagine anymore than that.

Yes... SLAs are very sensitive. But it's not uncommon for people to start out with SLAs. This is definitely the case in our shop. Lots of people get scared off by the high price tag of LiFePo4 -- even when we try to convince them it's much (much) better.

Truthfully, it's probably better to start off with the cheaper option until you determine if (and how) you'll use the bike. Some people get all excited and want top-of-the-line everything -- thinking they need the biggest / baddest setup. Then after a few months they get bored, don't use the bike much, or realize they didn't need so much power / range. Why waste $500-$700 on something you don't need??? Start out with SLA to determine your riding habits and expectactions... then when you're ready to upgrade... you'll know exactly what to look for...

I was getting about 6 miles full throttle out of 3 12 ah slas, and 8 miles out of 4. But that was using them 100% which quickly murdered them. I had a lithium battery coming and didn't care. You will be best off to just spend for 3 12 ah sla's and ride em about 4 miles per trip if you go full throttle. You will be able to feel the motor slow down. Don't wait for little lights on the handlebars to warn you. They only tell you it's too late already.

It's real important to get the right type of sla's. The ones you want are going to cost about $40-$50 apiece. Cheaper ones are not likely to be the type for high discharge rates. Ones intended for wheelchairs is what you need. Not ones intended for power supplies or lights. I used to buy em at wallmart, for the kids electric cars. If you don't have a charger, they are pretty cheap on ebay.

joeworrall said:

how much is this likely to improve my battery life compared to if i was only using the throttle?

Click to expand...

Depends on how much of the time you are starting from a stop and/or going up hills, and/or going fairly fast (over 15MPH-ish). Those are where you really use up power, and if you help significantly by pedalling, you could cut your startup power usage in half, or better.

UPDATEUPDATEUPDATEUPDATE:

Think most of you will be happy to here that i borrowed some money off my dad and went for the LiFePO4!!!!!!!
Its 48v10Ah which is plenty big enough
YAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAY thank you so much for all your suggestions and time. much appreciated

Congrats Joe. I think yer Dad is a cool guy too... you know, even though he is really really old now. hehe
Play safe
Lock

Try to find or fabricate a rack to carry the batteries lower. Two on each side like panniers should help with carrying all the weight vs having it all on top of the rack. I found 1/2" metal electric conduit an easy way to beef up weak racks with extra legs to the frame. You need a strong rack for sla's.

Good choice, read that you plan to do a bike trip. Lead acids would have been impractical for that trip. You may be passing your friends early on but will be last because the pack would be out of power and you would be pedaling a very heavy bike and hating it. I hope those packs come with a BMS, read up on taking car of them on the battery section. Get a feel for how the bike will work out for long distance and how it pedals without power before the trip. Some hub motors have a lot of drag due to cogging when not powered, this still might not be practical and a regular bike would be a better choice on that bike trip you plan depending on the distances travelled. Not being able to charge and keeping up with your friends on a dead ebike would be a drag. Congrats on your new ebike.

kfong

The battery comes with a BMS and a 5ah fast charger + bag. the motor is gearless, dont know if thats what you meant by cogging
There is overnight charging facilities at the places where we are staying, the trip should be about 40 miles each day, obviously i wont be using the throttle until im exhausted