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Old Feb 06, 2016, 11:48 PM
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3S Lipo to act as car jumper for battery not working.

There are several discussions of people using large 3S LiPo to jump start a car battery that has gone down because the lights were left on, etc.

I took the old SEL Pb acid out of my jumper kit and replaced the battery with 5 sets of 3S LiPoly in parallel. I have about 35 AmpHour in the set at 12.6 voltDC.

I used my Harbor Frieght battery tester as a load (it pulls 45 amps out of a new car battery during its 10 second test time). When I hooked it to the LiPoly setup, the voltage went instantaneously from 12.6 vDC to zero volts when I threw the load switch. Recovers to 12.6 vDC when I release the switch. Is the internal impedance of my collection of 3S LiPo's so low that it cannot support a resistive load of 0.3 ohms that my battery tester gives out when switched on?

Anybody got any ideas of what I am doing wrong?

I see all these car jumper kits on Amazon with LiPo packs that cannot be bigger than 3S at 15AMPhour. They all claim to start at least 4 times over a dead car battery with the kit. How do those systems do it?
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Old Feb 07, 2016, 02:28 AM
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You have something wrong in the voltage measurement. The IR of those packs surely isn't that low. If the packs are in a decent condition, it will be close to 1mohm. Quite a bit smaller than 300mohm of the tester load. Are all the cells in packs at 4.2v? Did you measure the lipo voltage from the balance lead?

Even one, say 2Ah 3s pack should be able to recover a car battery (just limit the charge amps with some series resistance, it might otherwise damage the Li-Pos)
Electroboom in YT revived a car battery with a couple of alkalines so much energy isn't needed at all to give the car battery a few percent of charge to be able to start the car.

E: I googled that battery tester. It seems to have a voltage meter. But check your connections and measure the voltage from the balance lead with a DMM while doing the test with the automotive meter.
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Old Feb 07, 2016, 08:55 AM
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Test the 3S batteries seperately.
If OK, reinstall and test for the poor connection. You most likely have a connection break under a load.
A digital voltage meter is your best friend though if you know your way around a 12v test light that would work just fine.

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Old Feb 11, 2016, 04:43 AM
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The problem I see with this setup is that a jump starter should always be ready, but LiPos dont like to be left fully charged for extenden periods of time.
So a 4s A123 might be the more suitable approach if you aim for maximum durability.

But as your system is already set up, I would compromise on a storage voltage of 3.9V/cell, which should still be enough to start the car, but also allows the packs to live long.
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Old Feb 11, 2016, 09:03 PM
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I use 4s lipos for starting my vehicles when the battery is dead, the extra voltage helps turn the starting motor much better than 3s. Even with high c, large capacity packs, starting a car with 3s is hard on the pack and the starter from the low/sagging voltage. Ive started my 3.6L V6 Caravan with a 4s 2200 mAh 50C pack, Im sure Im pulling a monster load through the pack but it starts in seconds and never gets warm. I'd be worried if it cranked more than a few seconds though!

Making a good connection is a must, having a poor high resistance connection is bad and will either not start the motor or melt the connector.

Some may say that I'm stupid and 4s is too much and may fry the electronics. I'm not so sure about that, I doubt the electronics wouldn't have any headroom built in for a few volts over 14.4V. Plus, the voltage will sag as soon as its connected from the load of the dead car battery.

Edit: Julez does have a good point. A123's can be stored without the cells degrading at full charge. If a lipo is kept at full charge, especially in a hot car it may not work when needed.
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Old Feb 14, 2016, 05:41 AM
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Hi, I do recovery work for a local garage, and we use a lipo jump pack, it is not much bigger than a wallet on pay day. It will not start a DEAD battery, where for instance the lights have been left on. It easily starts a partially flat battery, that would otherwise only make the starter solenoid click. 2.5 litre size diesels are easy. Many modern car systems record voltage spikes, and warranty claims that reveal spikes, may be refused. ... one evil recovery driver trick to fire up a difficult 12volt starter is to switch an old fashioned jump pack to 24 volts for a short period... don't do this on modern vehicles. Another tip.. when jump starting any motor, voltage spikes can blow all sorts of electric gadgets. To avoid this, switch on electric motors, like wipers or heater blowers, before jumping. I am so impressed with the little works lipo power pack, I plan to buy one myself, I can use it to charge the family cell phones etc. as well. Good luck with sorting your DIY. PS, a good feature is, I think, called a pass through, it means you can charge it , at the same time as using it to power something.
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Old Feb 14, 2016, 01:01 PM
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Quote:
Another tip.. when jump starting any motor, voltage spikes can blow all sorts of electric gadgets. To avoid this, switch on electric motors, like wipers or heater blowers, before jumping.
Wouldn't the battery alone absorb voltage spikes?
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Old Feb 14, 2016, 01:02 PM
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Quote:
Originally Posted by Julez View Post
Wouldn't the battery alone absorb voltage spikes?
I figure the same thing.
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Old Feb 15, 2016, 02:49 PM
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Jump start points on motors are frequently well away from batteries .. health and safety ?. What you are faced with is a red plastic cover over a live connector, the other negative lead just connects to a suitable earth point. From experience, strange things can happen... like remote locking activating, and if you haven't had the experience to leave a window down or wedge a door open... you could be locked out, with the key in the ignition, so clearly the battery is not absorbing enough, and the ECU data is recording that it hasn't.
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Old Feb 15, 2016, 10:44 PM
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Quote:
Originally Posted by VARSITY View Post
Jump start points on motors are frequently well away from batteries .. health and safety ?. What you are faced with is a red plastic cover over a live connector, the other negative lead just connects to a suitable earth point. From experience, strange things can happen... like remote locking activating, and if you haven't had the experience to leave a window down or wedge a door open... you could be locked out, with the key in the ignition, so clearly the battery is not absorbing enough, and the ECU data is recording that it hasn't.
That's what hammers are for! Do you know the voltage of the Lipo pack you have? Did these problems happen with the lipo or the 24V thing you talked about?
Ever had anyone attack you while doing repo? Thats the health and safety Id be worried about! Always wondered about that. Holy crap, 1000 posts! Dont know how that happened, it doesn't seem that many.
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Old Feb 15, 2016, 10:54 PM
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I have 4 -A123 2300mah in series that will jump a dead battery or even get a car started without a battery..
I think your lipos are bad.. check each pack and cell...
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Old Feb 16, 2016, 04:58 AM
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Quote:
Originally Posted by VARSITY View Post
Jump start points on motors are frequently well away from batteries .. health and safety ?. What you are faced with is a red plastic cover over a live connector, the other negative lead just connects to a suitable earth point. From experience, strange things can happen... like remote locking activating, and if you haven't had the experience to leave a window down or wedge a door open... you could be locked out, with the key in the ignition, so clearly the battery is not absorbing enough, and the ECU data is recording that it hasn't.
You are probably right, better safe than sorry. Modern electronics are up to all kinds of weird shenanigans, one can never know. My car is thankfully 27 years old, the only electronic system is the radio.
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Old Mar 21, 2016, 03:08 PM
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I just charged up the lipo jump start power pack , I hadn't noticed until today that it has an EC5 connector to the crocodile clips, I might have to borrow that at the weekends !!! The voltage is 11.1. All the strange electronic happenings were on 12v power, risking 24 v on modern stuff is too risky.
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Old Mar 21, 2016, 06:00 PM
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Interesting thread. Just stumbled on it. As mentioned they put batteries in strange places now a days. Mom had picked up a used Buick Enclave back around 2010. Last year the battery went and when I looked I couldn't find it, just the jump connections. Found out it was under the rear passenger side footwell. You have to pull back the carpet, take off a cover and then fish it out of there. Not a nasty job but not as fast as popping one out from under the hood.

I saw a claim once about boosting a car with a bunch of akaline batteries. Supposedly the trick with that was to use enough to put a charge into the car batt.. Connect them up and leave them a bit before starting the car. It was the internet so I was a bit skeptical but who knows.

Scott
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Old Mar 21, 2016, 07:32 PM
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It's not a recent thing, we had a Mercury Topaz diesel in the early 80s that had the battery in the trunk. The old VW beetles had it under the back seat. My partner has a 2001 Prius that has the 12V battery in the left rear corner of the trunk. Under the hood is still common but other locations are not unusual.
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