car jump starters, any advice on which one?

[Russianwolf]

since I don't fully trust the battery in my truck (I think the guy I bought it from didn't put the right amp battery in it as it cranks slowly sometimes, or the alternator is not charging it fully), I'm looking at one of the portable jump starters to carry with me when I use it. Anybody have one that they would recommend? I don't want to spend a mint, but I want one that works.

[scorrpio]

I researched those things recently cause I wanted to give one as Xmas gift to a family member. The 'glove compartment' variety devices that plug into your lighter socket are generally too weak. And you need to recharge them after every use.

And more substantial devices that are essentially a car battery in a portable casing, tend to be costly. In fact, most of those will cost more than a battery replacement. If I had concerns about my battery going dead, I'd probably just go and buy a spare car battery to keep in the trunk.

[LCHIEN]

Car Batteries are rated in capacity (Amp-hours) and cranking capacity(CCA or cold cranking amps).
To start a car you don't need a lot of capacity, you only draw current for a few seconds) but you do need a lot of CCA.
If you have a large engine with high compression, it will take a lot mroe amps than a small engine with low compression. Those car booster/jump packs generally have a small battery in them to help you start your car but they are not designed for bigger motors. RW, i think your talking about that Jeep you bought a few weeks back?

Anyway, your best bet would be to buy a decent battery with suffucient CCA. Before you do that, make sure all the battery connections are clean and tight. Some corrosion or a loose terminal knock you right out of contention. a starter motor needs well over 100A to start a car.
2/10th of an ohm on a 12V battery circuit will assure you can't get over 60A through it to a dead short.

[wreckwriter]

Quick and dirty alternator test: if you can access the back of the alternator look for a little button sort of thing (its actually the rear of the shaft mount). Using a steel screwdriver, touch the "button" with the car running. If its magnetic, the alternator is charging. If its not, its not.

This only detects total failure so its not foolproof but it gives you a starting point.

[sacherjj]

I think for the price of one that isn't really a total waste, you might just get a decent battery. The cheapest route would be to strap a battery in the truck bed and charge with a 12V charger, then you have a "jump" if needed.

[LinuxRandal]

You could even go to wallyworld, or one of those kiosks at those clubs, and input your info to get some battery numbers (things like 65-4) and search engines to cross reference your battery. I would also advise either use of your local autoparts stores (many will check your alternator output for free) or going to the library and learning how to do it your self with a dvom (digital volt, ohm, meter).



Another possiblity is a draw! The easist way to check for that, is with a cheap test light. Disconnect the negative battery cable, place the test light, between the terminal and the cable end, and if the light is lit, you have a draw. Then you start pulling fuses to determine where the draw is. (some vehicles, like Saab, this is a PITA, as you have to discharge the battery before doing a draw test).

[onedash]

I think most parts stores like advance auto, napa will test your battery and alternator for free.

[just4funsies]

I have a "suitcase" style jumper box that has left me high and dry TWICE. It is now being used as a doorstop, until I need it for a boat anchor...

[Thom2]

Another possiblity is a draw! The easist way to check for that, is with a cheap test light. Disconnect the negative battery cable, place the test light, between the terminal and the cable end, and if the light is lit, you have a draw. Then you start pulling fuses to determine where the draw is. (some vehicles, like Saab, this is a PITA, as you have to discharge the battery before doing a draw test).

This used to hold true many years ago, and still does on some older models that have radios without a clock memory. However, in this day and age of fuel injection, there is a constant draw on the battery regardless of whether the car is running or not. You'll always see residual current draw due to the computer and memory for various devices.

I sell the booster packs that are being discussed and quite frankly there's only one that we sell that I myself would feel comfortable with if I had to depend on it. That said, the unit we sell retails for approximately $160 and we sell several hundred a year to the repair shops that use them on a daily basis. For that kind of money, you can surely pick up a spare battery (or 3) to use in a pinch.

just some FYI, HTH

Thom
purveyor of fine auto parts

[LCHIEN]

I've bought a HF car battery tester that will (briefly) load the battery to like 75 Amps and measure the drop in output voltage to determine the CCA cranking ability of the battery. Not veyr expensive, they go on sale all the time and cost around $20 or so IIRC. The digital is not much advantage over the analog.

[Russianwolf]

hmmm.... well then, I think maybe a dual battery setup with an isolator switch may be the ticket. That way I will have a fully charged battery under the hood at all times (assuming the alternator isn't lame).

the battery in question is pretty new, but is a economy battery the former owner worked for advanced auto or autozone and I think he did some things to just get it gone.) and I'm thinking it just doesn't have the CCA needed for my starter to turn my engine.

[wreckwriter]

You're getting into a lot of money Mike. You could replace the battery and alternator several times for what a dual iso setup is going to cost (money and hassle factor).

I had such a setup in a Camaro once, in the trunk, it was a major install....

[mpc]

A couple ideas:
1: bad diodes inside the alternator can make it draw a fair bit of current when the engine is off. I've seen this type of failure suck a battery down overnight; sometimes though it can take a few days. A freebie alternator check at NAPA, Kragen, etc. will catch this. Another diode failure won't kill the battery but it makes the alternator loose 1/3rd of it's capacity... ergo slow charging.

2: poor wires or poor connections at the battery posts. It doesn't take much to weaken a starter motor. Dirty engine block grounds also can strangle a starter. Often the starter "grounds" via some other method if the engine block ground is poor... like through the accelerator cable which burns it up like a fuse.

3: What type of tranny is in the vehicle? A stick shift, in neutral, has a fair bit of drag to it... especially if it's really cold outside. The oil thickens up quite a bit. Holding the clutch in reduces the load on the starter considerably. Auto trannies always drag down the starter a little bit; fortunately cold auto tranny fluid isn't as thick as cold stick-shift gear oil generally so ambient temp doesn't exacerbate the situation.

Take a look around and make sure any courtesy lights are going off when they're supposed to... glove compartment light/switch work, trunk light, radio backlight, etc. A friend's car had a flakey trunk switch that left the trunk light on half the time...

What is the charging VOLTAGE at the battery terminals? It should be around 13.8 volts; generally 13.5 volts to 15 volts is normal. If it's below 13 volts the battery is not getting a proper charge from the alternator. Test the voltage right after starting and after a long drive that heat-soaks the engine bay. Regulators tend to be temperature sensitive; when hot they output less voltage.

mike c.

[LinuxRandal]

This used to hold true many years ago, and still does on some older models that have radios without a clock memory. However, in this day and age of fuel injection, there is a constant draw on the battery regardless of whether the car is running or not. You'll always see residual current draw due to the computer and memory for various devices.

I sell the booster packs that are being discussed and quite frankly there's only one that we sell that I myself would feel comfortable with if I had to depend on it. That said, the unit we sell retails for approximately $160 and we sell several hundred a year to the repair shops that use them on a daily basis. For that kind of money, you can surely pick up a spare battery (or 3) to use in a pinch.

just some FYI, HTH

Thom
purveyor of fine auto parts

That is why I mentioned Saab, they actually have a proceedure to drain the radio memory as it's just a capacitor, then you can do the test. I stll am able to use this test on vehicles, and most of the ones I work on are post 85 fuel injection.

[Russianwolf]

okay, how about a Marine Battery Selector Switch? They aren't expensive, $30 or so + Cables + second battery. That way I can run off one or the other or both. And if I hide it pretty good, It can act as a starter kill switch too.

Nothing complicated to wire, the two positives from the batteries go to the switch and one lead out to the normal place. I'm leaning towards getting a better alternator also.

I'm going to have to buy a new battery for this thing anyway, but I'll keep the current one under the hood as a back-up.

This IS for the 1970 Jeep pickup I just got so there is no fuel injection or radio memory to worry about. just bare bones wiring.