ThumperPup

i used to have this unit here for my old cadillac incase the battery died
Schumacher Electric 750 Peak-Amp Jump Starter:
750 peak Amps for jump starting vehicles in emergencies with a 12V DC power outlet and 2A USB port
Built-in light and a 150psi air compressor
1-year warranty
Model# XP750W

When i tried to use it to bump up my tires the other day it did/t work anymore
So I figured it lasted me 2 years did the job all the time no problems
But i don/t own the Cadillac that has the big batter and the huge v8 that it needed to power

so can i go with something that handle a 400 peak watt or 500 peak what or do i need to go larger like the 750 again for the ES ?

gilden

I have a Lexus ES 350-2008. The battery was replaced 2 years ago at the Lexus shop, manufacturer recall.
Now I am told it's dead and must be replaced. What is the warranty on a battery like that?

christcorp

First mistake would be having it done at the Lexus shop this time around. You pay a lot more for it. And replacing a battery is something even a 12 year old can do. You'd save a minimum of $50 easy getting a battery from a auto zone type of place.

But to answer your question, most batteries have a 1 or 2 year warranty. Some better ones have more and they pro rate the price.

ThumperPup

Ok please back to the Main topic can anyone answer what's a good cranking amp for a jump box ?

christcorp

For the average $20 - $30 difference in price, I'd stick with the larger booster. Gives you more options. Including helping the family member, neighbor, stranded motorist, etc... The one I have is 1200 peak amp and about 600 cold cranking amps. I use it for all my cars if needed. My lexus as well as my Ford F250 with a 460cu (7.5L) engine. Also my Rav4, Explorer, and suburu.

Point is, the jump starter can never be too big. But it can definitely be too small. And if I only cared about starting my Lexus when I was out in the cold weather, (Which I get plenty here in Wyoming), then I'd simply buy a good pair of jumper cables. There's always someone around to help give a jump start. I have a jump starter so I can help others; plus I want a tire inflator as well as the AC power inverter if I need it. And when you see that the price difference between the smaller and larger models is relatively little. A 1000 peak / 500 amp starting can be bought for $80. The smaller 600 peak / 300 amp starting is $50. That's for the same brand, just 2 different models. For the additional $30, it's a no brainer.

Lefoyxxx

They all run off of a small motorcycle battery. A good set of jumper cables is a better bet. The best of them will put out 200 amps at best. I have tested them.

christcorp

Can't say that I really agree with that. Not 100%. Just partially. First, there are definitely plenty of jump starters out there that put out more than 200 cranking amps. The thing about jump starting a dead battery is; "How dead is it". For a small car, it usually takes around 200-300 cranking amps to start it. 400-500 for a medium to large care. So when you've accidentally left the dome light on or similar, and your battery starts to turn the motor, but not enough to start it, then a portable jump starter may just be the solution.

When you connect a jump starter to your battery, the car's battery is going to take most of the current from the jump starter. But, your car battery may only be down to around 150-200 cranking amps, and the addition of the jump starter is enough to start the car and let the alternator take over.

In simplest terms, if your car batter is totally dead 100%, then a small jump starter probably won't start it. But that will depend on the weather, temperature, and the size of the jump starter. You can actually buy jump starters that truly have 900 cranking amps. You will pay for it though.

But just like jumping a car with jumper cables and another car, the best way to do it is: Connect the cable between the car battery and the jump starter, (Or 2nd car if just using cables); and let it sit there for about 5 minutes if it's to another car. 1-2 minutes if it's a jump starter. You're basically trying to charge the dead battery up enough to start the car. It's unlikely you're going to start the car with the jump starter by itself. Not unless you got one of the mega-jump starters.

Think about it. Your alternator, which runs ALL of your electrical power, plus chargers your battery, only has an output of 130 amps on the lexus es350. When a car's battery is dead, it takes a while for the alternator and the car driving, to give the battery a good charge. But between the starter needing about 133 amps to spin; then throw in the load of the motor that the starter is trying to spin, that is why you need for the lexus we are talking about, about 300-400 cranking amps. If you're buying a jump starter, realize that you're "Assisting" a weak battery. You're not trying to actually start the car 100% using the jump starter.

ThumperPup

since my jumper box still works and the only thing that stopped working was the air compresor i decided id just buy a 12v compact compressor the one i got says it will inflate a car tire in under 5 minutes my jumper box is 750 Cold cranking amps i think

christcorp

They normally mention "Starting" amps. Sometimes even "Cranking" amps. Usually, "COLD Cranking" amps is only on batteries. Simply means at what temperature.

Chances are, your jump starter is 750 "Peak" amps.Which would be around 200-250 "Cranking" amps. Which is still fine to "Assist" a weak battery on most cars. Manufacturers are very misleading when they talk about jump starters and amps. "Starting or Cranking" amps is usually around 1/3-1/4 of "Peak" amps. Sometimes, they'll mention "CCA" "Cold Cranking" amps. That's a little less. Around 1/5 of PEAK. Here's a good example where it's all pretty well listed.

Basically; 3000 peak amps. 800 starting/cranking amps. 650 cold cranking amps. But it has 2 batteries; weighs 47 pounds; and costs $350.

http://www.ebay.com/itm/12-Volt-3000-Peak-Amp-Jump-Starter-w-FREE-Battery-Charger-6-12-Volt-6-2-Amp-/141115183336?_trksid=p2054897.l4276

Lefoyxxx

I stand by my statement. If you can get more than 200 amps out of a small 19AH battery you are a magician. I have tested them with my load tester. Have you? What they claim and what you get are quite different.

christcorp

You can't use amp hours as a measurement. A typical car battery is around 60Ah. Some more. Yet, you can easily get 1000 SSA. (Short Circuit Amps). Obviously, that will only last a few seconds.

That little 20Ah battery you mention, (Rounding up for convenient math), means it can draw a constant 20 amps; or 240 watts on a 12 volt battery, for a complete hour. Which means, 40 amps for 30 minutes. Mathematically, that means 80 amps for 15 minutes. 160 amps for 7 minutes. 320 for 3 minutes. And 640 amps for about a minute. Of course, this would create a lot of heat and the battery wouldn't last a full minute drawing 7000+ watts. But mathematically, that's what it could do.

Hell, I've used car batteries to do emergency arc welding. Disconnected from the car of course. Jumper cables and some welding or brazing rods.

Jump Starters are designed to be a booster. Meaning, the battery in the car that won't start is WEAK. Not totally dead. If you have a totally dead battery, and assuming that it isn't shorted, you're going to need to either replace the battery or at least get a jump start from another vehicle. You're going to need the 60-80 amps coming out of the good car's alternator to do a quick charge on the battery in the car that won't start. Point is; even a new car battery is only around 60-80 Amp Hours. Even most alternators are only around 75-100 amps. (yes, you can get 300 amp alternators, but we're talking about standard cars).

But remember; you're not trying to draw 60-80 amps for an HOUR out of a battery. You're trying to draw 300-500 amps (Depending on the temperature), for about 2-3 seconds. But a motorcycle battery isn't quite the same as a jump starter battery. They may be close in amp hours, but there's circuitry in the jump starter to ensure the battery doesn't get completely shorted trying to start the car. A jump starter replacement battery is cheaper than a motorcycle battery.

I'm not saying that jump starters are the end all cure for cars. The generally won't start a car that has a completely 100% dead battery. They are designed to "Boost" the weak battery. But with the proper circuitry, you can even take a 20 Amp Hour battery, and get 500-600 amps out of it. Albeit for a very short period of time. But that's what starting a car is doing. If your starter and fly wheel are spinning for 5, 10, 15 seconds and the car hasn't started yet, you have much bigger problems.

Lefoyxxx

I am an electrical engineer. The point is that these little boxes are very limited. I bought one a few days ago made by Schumacher that claims 1200 peak amps. To the layman that looks great but it means nothing in practice. I tested it with my load tester and could get 220 amps for a few seconds before the voltage plummeted.

In contrast, the new Interstate group 24 I just bought delivered 300 amps for 15 secs with voltage dropping to 10.

christcorp

And that can be completely accurate. Depending on the limiting circuitry in your jump starter. There's no doubt. Even schumacher advertises their 1800 peak amp as only putting out 280 cranking amps and about 220 cold cranking amps. Which as an assist to a weak battery, is probably enough. But the limiter in the schumacher is probably designed to not allow the battery from being drained too quickly. Then again; the schumacher 4424 model advertises 4400 peak amps; 500 cranking amps and 415 cold cranking amps. The cost is about $350, but that's besides the point.

There are some others however, who probably don't put as much limiting; thus protection; on their battery, The JNC660 happens to be one that I've used and am impressed with. Only weighs 18 lbs. It boasts 1700 peak amps and 425 cranking amps. Which would be about 330 cold cranking amps. And this is definitely possible. Depending on how much you want to limit and protect the battery.

I bet, if you took the battery out of your Schumacher, and put that through your load tester, you'd get more than the 220 amps you found. A traditional 12v 18ah battery like the PS-12180, which is used in everything from motorcycles, to golf carts, to electric cars, tools, generators, etc... can definitely put out a lot of amps for a short period of time. It is the most common 12 volt non-strictly automobile battery on the market. I even have one in my UPS system.

Matter of fact, Universal Power Group; who makes the UB12180 battery, which is a direct replacement for the PS-12180, that they use in monster wheel chairs, even rates the battery by itself at 280 "Cold Cranking Amps". (Which would be about 350 cranking amps). With the right protection, you can raise the CCA for a short period of time.

You are definitely correct in much of what you say. But in the world of Jump Starters, you have to look at the jump starter manufacturer; the limiting/surge circuitry they use; as well as the battery that's in the unit. Not counting industrial jump starters (Which actually use automobile batteries), you can get jump starters with batteries in there from 5ah all the way up to 35ah.

Lefoyxxx

Put your money where your mouth is. I have disassembled many of these boxes. You will find a small lead acid battery in the range of 20AH, a trickle charger, and various other stuff like an air compressor or invertor. I have never found any kind of current limiting device in any of them in the jump starting circuit.

A lot of current for a short time ( a few seconds) is of no value. This short circuit current is what is written on these devices. It is deceiving advertising


I will take the battery out if the wager is high enough. I will video the test.

christcorp

How long do you need in order to start a car? If you need more than a couple seconds to start a car, then a jump starter is definitely not going to help you. I freely admit that. But even my 1966 mustang, sitting in the garage most of the winter, with the battery just sitting there, fires up in LESS than 2 seconds. "Assuming the carbs are primed". I've never had a car, especially modern day, that took more than 2-3 seconds to start. All of my cars start in such short time, that I couldn't even count it in seconds. And I live in some pretty cold climate.