Battery Type for Electric Bike

[3wheels1life]

Hi everyone,

I will be building a 26" 24v 250w electric bike, and was wondering what type of battery is best?
I have some SLAs from a previous project (12v18ah) I'd like to use, but they're quite heavy. Is there a good way to mount the batteries so the bike doesn't tip over when parked (a problem I experienced before). 20 mile range would be great (using Golden Motor 24v 250w geared hub motor).
Apparently some people have used size "D" NiMH batteries for an ebike (which can be bought from China cheap). They put them in series, parallel, and solder the tabs together. Then they put a thermristor (I think that's the term), fuses, wiring, and shrink wrap the whole thing.
Is this dangerous (I know NiMH can be dangerous if not charged properly)..what else would I need to do to make a NiMH pack that is safe?

Thanks. Everyone here has really helped me.

-3wheels1life
-3wheels1life

 

[Eujangles]

One of the lithium batteries will be best as far a life cycle, discharge and weight go, so pretty much in every category.

Check out ebay seller Li-Ping for Lifepo4: heaviest of the lot, but reliable, massive lifecycle and you can find pretty good c rates

Check out bmsbattery.com for lifepo4 and LicoMn: cheap and light, but usually no higher than 2C

Check out hobbyking.com for rc lipo (but if you go this route, you will want to do a lot of research first): lightest of the bunch, massive c rating, but dangerous to use and maintain if you are not willing to put in the research and work. At just 24v though, you could keep it to only 1 large pack depending on what range you are looking for.

Try to get the batteries in the frame of your bike, the lower the better and it will not tip over.

If you are going to make your own pack, use a bms for sure.

Good luck!

 

[3wheels1life]

Thank you for your reply.
Where can I get a NiMH BMS?

-3wheels1life

 

[DAND214]

Thank you for your reply.
Where can I get a NiMH BMS?

-3wheels1life

I don't think you would want to use them.
Takes a lot of cells with little AH.

Dan

 

[amberwolf]

Apparently some people have used size "D" NiMH batteries for an ebike (which can be bought from China cheap). They put them in series, parallel, and solder the tabs together. Then they put a thermristor (I think that's the term), fuses, wiring, and shrink wrap the whole thing.
Is this dangerous (I know NiMH can be dangerous if not charged properly)..what else would I need to do to make a NiMH pack that is safe?

There's a recent thread (last few days) you should find and read that discusses that.

Basically, unless you are capable of designing somewhat sophisticated electronics, and building and testing them, I don't recommend attempting any form of paralleled Ni-MH or Ni-Cd cells.

It's possible to do it with less sophisticated methods but it is not as safe, and could result in fires or exploding cells (shrapnel!).

 

[arkmundi]

The battery is the most difficult/expensive component in the ebike equation. Suggest you use ES to research the many different options available to you from prebuilt to build-your-own, from BMS or no-BMS, to various chemistries for longevity, capacity and C-rate, and at various costs to you. Every successful builder on ES will have a different opinion, which you can gauge from their posts or query. ES was a great, but not the only, resource I used in making my own decision, for my own build of an A123 AMP20 prismatic LiFePO4 cell battery. Best!

 

[dogman dan]

In 24v, 20 ah will be plenty for 20 miles. Until you get some lithium, either lifepo4 or limn, you can use the lead. Carry the batteries in panniers, with one on each side of the back wheel.

Two kickstands might work, on a the center, the other near the rear axle. Or get a double stand.

 

[3wheels1life]

Thank you to everyone who replied. I appreciate your advice as I work on building another e-bike.

-3wheels1life

 

[RoadWrinkle]

Consider the weight to power ratio of SLA's. You are spending a considerable amount of energy just to carry the battery. Lithium battery's are less expensive in the long run because they are more efficient. LIPO can be one bad BMS away from a fire.

 

[mlt34]

If you aren't in a huge rush to get lithium on board, you can go ahead and use SLA's to get a feel for the new bike. Know that your performance will improve (power boost/weight reduction) if and when you switch to lithium. I highly recommend a Ping 24V battery in a triangle frame bag in the center of the frame. His batteries are really good quality and your low power application means the battery will last years and years.

 

[3wheels1life]

Hi Everyone,

Thanks for helping give advice.. looks like I will be using a 36v motor not 24v. I have 3 12v 18ah SLA batteries..how should I mount them so it doesn't tip over?
I have one in each pannier, where should I put the other one?

Thank you.

-3wheels1life

 

[mlt34]

Hi Everyone,

Thanks for helping give advice.. looks like I will be using a 36v motor not 24v. I have 3 12v 18ah SLA batteries..how should I mount them so it doesn't tip over?
I have one in each pannier, where should I put the other one?

Thank you.

-3wheels1life

panniers are a good idea. They keep the weight down low which is good for handling. You can either put the last battery on top of the rack, or even better would be in the front frame triangle between your knees (you can create a sling to hang it from the top bar - I've seen liberal amounts of duct tape used - or you can mount it more rigidly to the lower frame member with big cable ties or hose clamps).

The main thing is to keep it centered left to right (so probably not in one of the panniers that already has a battery) and to try to keep it as low as possible.

 

[3wheels1life]

Thank you to everyone who replied and gave advice.

On the subject of batteries, who is a good seller of LiFePO4 (ebay, etc.) I know Ping is.
Also, Is this NiMH pack (link below) a good pack, and is it possible to safely build one?
http://www.batteryspace.com/nimhbatteryandchargercombo36v10ah18asmartchargerfore-bike1.aspx

Thanks.

-3wheels1life