Makita M18 LXT battery jump starter

not likely.... hmmm

 

Nice to see someone trying this. There was another recent thread where someone was asking about using an 18V tool battery as a jump pack in his Prius. Just about everyone except me said the car would explode. Not sure if he ever tried it. His plan (I think) was to connect it through the cig lighter / power outlet, which would be fused at about 15A, protecting the tool battery in case the car tried to take too much.

Similar to your confidence in this working, I think it should be just fine in the Prius, with virtually no risk. The 12V battery will keep system voltage from spiking, and hopefully the tool battery would contribute enough voltage to power on the HV electronics.

However, I have doubts about something that small being able to actually start a regular engine. Being designed for use in a power tool, I'll guess they put out not much more than 20A (?), and most starters want 200+ Amps. So it will boost, and not cause damage (same reason as the Prius), and might be just the little extra the engine needs in some cases. But in many cases, it would not work. At some point, the internal resistance in the tool battery will limit the current.

Do you have specs on max current for the battery pack, or a plot showing how the voltage drops with current output?

 

My impression was that the lithium jump starter packs use some sort of capacitor? I have a lithium jump starter pack from Amazon that is not much bigger than a tool battery, and I was very surprised to see that it was able to start my V8 E350 Ford van with an almost dead battery. I guess I'll have to look up how these packs work. Cool idea with the tool battery adapter!

Posted via the PriusChat mobile app.

 

There IS a capacitor in the pack. The 12volt battery charges the capacitor.
When you start the car, the capacitor discharges its amperage into the dead battery/car.
I read an article about how they work a few years ago. I KNEW the little 12v 4 or 5 amp battery
couldn't power the starter of a car.

It works the same was a "start capacitor" works for a house ac unit.

 

I don't know the details, but yes, a capacitor makes sense as the way to do it. Any battery will be limited at some point by the need to have a chemical reaction occur to release the energy to drive the circuit. The associated heat and internal resistance will be limiting. With a capacitor, the charge is right there ready to go when released.

Without needing to know the design details, just considering that a jump pack is designed to release high current for a few seconds, vs. a tool pack is designed to release up to ~20 Amps for many minutes, will give you an idea of feasibility for starting an engine.

BTW, a start capacitor in an AC unit (and similar single phase AC motors) is actually completely different. It is an AC capacitor (vs. a polarized one) and the sole purpose is to create a current that is 90 degrees out of phase from the incoming current, so the motor can be started. Without it, the single phase coming in just goes back and forth, causing the motor to hum but not move. If you were to manually get it started, it would keep going. More info on that:
Single Phase Motor Starting – Voltage Disturbance

 

It may not be exactly the same way for a house ac Air Condition, but the principle is the same.
The way the AC man told me it so the house doesn't get that huge draw when the compressor kicks in.
The capacitor is starting and running the compressor for a second or two before
running off of the house ac(alternating current).
Yes, I know there is a LOT more to it, but I try to keep it simple. It's good enough.

 

The dbPower Lithium jumpstarter I just took apart certainly doesn't have a capacitor unless it's in the little black thing that's part of the plug-in charging leads (it also has the LED display in it to indicate reverse polarity, too-low battery voltage, etc.) -- and there's not much room there for a capacitor of any decent size. OTOH, I did just see a jumpstarter on the Home Depot site that specifically mentioned a capacitor.

 

Yes, that is simple. But it is completely wrong. Just so you and others know. Incorrect knowledge has a way of getting out there and propagating. Not really relevant to the thread. Did you ask your AC guy where he got his EE degree?

I spent a little time on google trying to find you an explanation that is both simple and accurate, but could not find one. I'm sure it's out there somewhere. I did find a ton of info that was simple but also completely wrong. Common these days, when the ability to publish seems to have little relation to accuracy.

 

i doubt that little battery woyld turn over an engine. for prius, maybe you can find an ebay 12v tool battery

 

Whhhaaatteeevverrrrrrr

 

that's no way to end a debate

 

I was NOT debating..... And I'm not going to be nit picky either

 

i could see that. i was thinking automobiles

 

I think the easiest is:
- DC: capacitor can store energy
- AC: capacitor change the phase or filter frequency