Jump-starting from Prius 12v battery--wimpy?

Most probably yes, I started my dead Prius last winter with 12V motorcycle battery removed from my bike

 

D cells would be a better bet.

 

I have successfully used the battery from my 12V DeWalt cordless drill without any fuss or theatrics.

 

I have used motorcycle batteries to jump a prius. I also used a lithium radio controlled airplane batty to jump start several different vehicles. The little high output lithium batts can fit in your pocket and jump start a v8 pick up truck! Problem is they tend to catch on fire while charging.

 

Sounds perfect to me

 

Fire! A minor inconvenience. Better than rubbing two sticks together.

 

With all this discussion about jump-starting vehicles and the recent cold snap experienced by much of the country, I did want to mention an issue we see quite frequently on our end. Whenever any battery is discharged to the point that a vehicle needs a jump-start, that battery should be fully-recharged with a battery charger as soon as possible. Just as you would go right to a gas station after using a one-gallon can of gas to get you off the side of the road, you should make the same effort to fully-recharge your battery as soon as possible after using a jump pack or jumper cables.

Most vehicle charging systems are designed to maintain batteries near a full state of charge, not recover deeply-discharged batteries. Asking that task of a charging system can lead to a cycle of dead batteries and jump-starts, until either the battery or charging system fails.

Jim McIlvaine
eCare Manager, OPTIMA Batteries
OPTIMA® Batteries (optimabatteries) on Pinterest

 

The question is if Prius is different from regular car in this respect (also), since the charging of its small 12 V battery is performed and controlled electronically by DC/DC inverter rather than an alternator.

 

I use the same one. I hope Jim responds.

 

Battery tenders are fine, as long as they get the chance to fully recharge the battery in a reasonable length of time. If it takes two days to get back to full with one, there will still be damage that could have been avoided with a higher capacity charger. Look at the tender's charge output (The Jr. puts out 0.75 amps) and divide it into your battery's capacity in amp-hours. The result may convince you to get a larger maintainer. I have a 2 amp one that will recharge a full-sized battery in less than a day, to supplement my BT Jrs. (I also have a real battery charger.) Your car's electrical system can usually get the battery *most of the way* back to fully charged, if you turn off unneeded accessories and make sure the engine runs for at least 15 minutes, above idle, after being jumped. Driving on the highway is best.

 

I only use the battery tender mentioned above to maintain a charge when the car is left for weeks at a time. I have a regular charger, but that seems like over-kill for what I'm using it for. If the battery dies, I'll use the real thing.

 

Yep! Right on!

 

Fred, in the interest of full disclosure, Optima sells batteries and chargers. Rather than pitch you on one versus another, I'd prefer to describe what to look for in general. Most chargers will work just fine on our batteries, but units that are microprocessor-controlled are preferred, particularly those with AGM-specific settings. Some chargers have confusing “gel” or “AMG/gel” settings and we don't recommend using those settings on our batteries, as they may not fully-charge non-gel batteries and could damage them over time. We also don't recommend a charging rate that exceeds 10 amps.

The math of simply dividing charger output (2 amps for example) by battery capacity (38 amp hours) does not account for the fact that most chargers taper amperage throughout the charging cycle. You may want to add 10-20% onto that math for fully-recharging a battery. Modern chargers will regulate amperage and voltage, so your battery doesn't get overcharged, but you should pay closer attention to units that do not.


I can tell you exactly what happens to your alternator after you jump-start a vehicle with a deeply-discharged battery, because I did exactly that with the help of Brady Basner from Powermaster Alternators. First, we established baseline measurements- the battery was at 13.0 volts before starting, alternator temperature was 115° at idle with an output of 22 amps. We took a 10-minute drive, where the alternator was at 14.0 volts, 14.4 amps and 158°. We then discharged my battery down to 7.9 volts and jump-started the truck.

Immediate measurements showed the alternator temperature went from 158° to 219° and the alternator output went from 14.4 to 104 amps. After a 10-minute drive, the alternator temperature was 299°, the output was 84 amps and the battery had a surface charge of 12.11 volts, but actual voltage was much less. We essentially cooked the alternator and the battery was still deeply-discharged. You can do that in an emergency, but it is best to fully-recharge the battery with a battery charger as soon as you can.

Jim McIlvaine
eCare Manager, OPTIMA Batteries
OPTIMA® Batteries (optimabatteries) on Pinterest

 

A note to company representatives: notice that DianneWhitmore and OptimaJim do not just shill their product. They try to give good advice, and cope with unhappy customers as well, and you know, that actually sells more than just trying to sell.

 

I've gotten into the habit: if I need to get into the the car for anything OTHER than driving it, I go in through the passenger side, to avoid that brake cycling thing.

 

Hey, I like that idea. I remember doing that on my new (to me) '04 and I wanted to test the voltage of its (dying, as it turned out) 12V battery. Running the brake pump would have affected the test result, poor thing!

 

. I think that if you are in business that is the only true way to go, you will prosper because you are a real person.