Homemade jump starter?
 

So I am wondering if anyone has made a jumper battery pack. I know guys have made actual batteries but what about something small to jump a bike with?

I am thinking li-ion cells but not sure how to go about it.

I'm reasonably sure you could ask Tweety and he could give you the specs you would need as well as the most efficient method of construction as an item of this type is right up his alley. There're several Utube postings that reference the repair of cordless/battery power tool battery packs that may give you some ideas. The cells are not too expensive on places on the net, ie. Ebay, Amazon ect.






The Dragons Tail runs through my backyard!

Out of curiosity, what are the circumstances for jumping the bike? On the track or out in the city or adventuring around the world? I'd imagine just having cables would be a simple solution for most people... otherwise a second LiFePo4 battery to lug around. They're light, small, hold charge for a looooong time and discharge quickly so they work well for things like starters (long draw situations they have more competition). The trick would be to charge it again after you've used it, which could get tedious if it's a regular thing.

Seven, the reason I want one is that I have a propensity for battery trouble. For example, last winter my poor vtr had to sit outside for 12 hours while I was at work in Manhattan in sub zero temps. Even a good battery has trouble with that sometimes.

I would have to roll it inside and let it warm at like 3am (when I want to leave).

In my world, a small LiIon jumper would be useful and I modded my underseat a big storage so could keep it on me.

I just couldnt remember where on here was a tutorail or thread on making a small battery (I think it was for race applications). What was that thread called?

I have a little boom box that I made using LiFePo4 batteries, and use this charger on it:

Smart Charger (1.5A) for 12.8 V LiFePO4 battery Pack (4 cells) - CE / UL listed

It's worked well so far. Just plug it in until the light turns green then you're good to go for the next jump start.

7, I was hoping for one with alligator clips to actually jump the bike. That looks like it may charge it over time so the bikes own battery could recharge. The retail ones with cranking amps are mad expensive, thus the DIY.

You could probably just use something like this with some alligator clips to supplement the stock battery in a dire straits situation:

Customize LiFePO4 26650 Square Battery Pack:12.8V 3300 mAh (42Wh, 7A rate) w PCB

The old thread was this one, but most of the information won't be as useful as the A123 Battery cells are harder to source now (DeWalt isn't using them in their packs anymore) and just buying an existing pack at your specifications has less chance of overheating the cells:

https://www.superhawkforum.com/forum...-update-22066/

Edit: Oh that first link was just for charging the battery once you've used it. Traditional battery trickle chargers are pretty hard on LiFePo4 packs so you need a dedicated charger...

Hmmm, yeah, the $70 thing is why I was hoping to diy. There are a bunch of purpose built ones for around that price.

Thanks seven.

I found this. 8 Cell A123 18650 Motorcycle Start Battery 13 2V2 2AH 12V New A123 Battery Pack | eBay

Its 8 cells which is overkill for a jumper but at $45 shipped I may just get it. Also found a bunch of A123 cells for cheap (almost too cheap) on ebay.


May order that pre-made but really want a 4 cel unit

These seem to cheap to be true http://www.ebay.com/itm/4x-3-7V-CR12...1#ht_617wt_781

Oh and they are low amperage

That's only a 2.2Ah pack... Which might be enough but maybe not for a V-twin in the cold. The one I'm running in my bike currently is a 4.6Ah. I think the varying cell sizes are throwing me off...

Those are Li-Ion not LiFePo4 ;)

Maybe four of these?

LiFePO4 18650 Rechargeable Cell: 3.2V 1200 mAh, 18A Rate, 3.84Wh, UL Listed, UN38.3 Passed (NDGR)

What would stop these working for a jumper? 4X GTL 3 7V CR123A 123A CR123 16340 Lithium 2300mAh Red Rechargeable Battery | eBay

I think I'm in over my head here, but I think those are way low in their ability to discharge quickly. They look like 4A each. A stock battery has about 180A from what I can tell. For reference the A123 cells have about 70A continuous discharge (each). I'm sure there's a basic formula for combining continuous discharge, but the ones you posted look way too low... But like I said I'm no expert either...

My guess is you get what you pay for when it comes to batteries... they're not really a niche market or anything...

No way seven, your part of the plan now, part of the team. You gotta burn that midnight oil to help figure this out. (LOL).

This is like a race team, driving through the night to get to the track.

You mentioned large underseat storage for the battery, would it stay in there while the bike is parked in the freezer or bring it in with you so it stays warm? Do the Lithium batteries struggle if they are cold like a lead acid battery does?

Do you run a battery tender? If I was doing what you are planning I would install a battery tender hook up to the battery, and make an appropriate wire from your jumper battery so it's just plug and play.....but, if you're keeping it under the seat, lifting the battery flap to hook alligator clips is easy enough.

Actually, lead acid batteries thrive in cold. This is why you can save duracells by putting them in the freezer.

The hard part is turning the frozen oil and cold motor. I would have no problem bringing it with me, I have just struggled enuff to want this to prevent future headaches.

Kinda like why I have a backup R1 RR and an extra set of wheels in case of blown tires. (try fixing a tire at 6*F roadside in NYC, its worse than you can imagine)

I leave the bike on a float charger when at home & my garage only goes down to around 50*. I am thinking of running super thin oil this winter.

I have been running zero wieght in the racebike and you actually gain HP by doing so (dyno tested). But figure the vtr would be ok with thin stuff in cold weather.

Hey SmokinJoe, just be sure the jumper wires are of a large enough size to handle the load other wise you will be looking at 2 red hot wires that just smoked off their insulation.


You will also need to insulate the battery clamps at both ends of the cables as well because these will get red hot as well especially when your cranking the starter!


Use several layers of shrink tubing on the clamps should keep your digits from getting burnt.


SIRR1

Thanks SIRR. I just ordered this thing since I dont think I coulda built one myself for cheaper. I just gotta figure how to charge it.

8 Cell A123 18650 Motorcycle Start Battery 13 2V2 2AH 12V New A123 Battery Pack | eBay

That is a good price. There's no way that you could make a pack for that money. Now that 123 Systems is Chinese owned it makes sense that they could source the cells at a low enough amount to sell the pack at that price. It will be interesting to know how the pack works for you. Looks like all you'll need to do is bolt the Anderson connector to the exsisting battery and when needed just plug the pack in and start. I'm hoping that the maker used a cell with the proper short duration max discharge rates to handle the heavy draw that the starter will pull, especially with very cold oil. Might be better to have the pack in the warm, although under load the cells do heat up on there own. Data shows a -30C (-22F) as the low end operating range.
Here is what I believe is in the pack you purchased.
APR18650M1A Cell
If the wire leads and the busses hold up it looks like the pack ought to be good, and at that price it's worth the gamble.
I don't know if anyone else is using 18650 cells for a starter pack. Would like to see a Shorai or other commercially available pack opened up to see what cells are inside.
Looking forward to a review.