Jump start using SLAs?

[KevinL]

I was just thinking about spotlights and dead car batteries earlier today, and I was wondering whether it would be possible to jump start a car from a 7AH 12V spotlight sealed lead-acid in case of an emergency.

I'm aware that maintenance-free car batteries are one thing - heavily optimized for maximum cold cranking amps, and spotlight cells are optimized more for power delivery at lower currents. Would it be possible or is there anything that specifically recommends against this such as the risk of blowing the battery (and operator) into the next world, etc.

Another thread suggested using available cells to attempt to slowly charge the dead car battery, rather than use the cells directly, but that was in the context of "can a bunch of CR123s start a car".

 

[wptski]

KevinL:

I'd have to look it up when I get home but I have one of those JumpnStart units. I checked the CCA with a Midtronics Conductance tester thru the leads and just got over 200CCA. I took it apart to get right on the connections and got a bit higher, maybe 280CCA.

I took the battery info, found the battery manufacturer but never could find a Ah to CCA converstion formula. I'd say that 7Ah doesn't sound very big but I'd to check what's in my unit.

Years ago at work they used Ford tractors with welding unit attached to the PTO. A welder came on a job for me. Started the rig, reved it to whatever,etc. All of a sudden there was this big KaaBoom. Luckily we were on the other side of the rig. It blew the side off the battery and there was acid everywhere! He had been complaining about the rig and wanted me to vouch for him in case, he got in trouble. He was a bit of a trouble maker, who later on became Prez of out local!!

 

[VidPro]

a 12v gell cell fully charged MIGHT raise the voltage of a car battery enough to get you out of a fix.
Meaning if it was on the EDGE of starting anyways, and you gave it enough TIME to slowly transfer some of the juice from one to the other.
BUT
it did not work when i needed it both times, and i even stacked them i had like 24A of 6x2 starved electrolyte, sent to the lighter plug slowly hopeing to get enough juice in to the 70+A car battery.

I wouldn't want to count on it even in an emergency, if you had a higher voltage differential, and again enough time to transfer it a bit slower than jumper cables, it would work better.

just depends on the level of discharge of the car battery, and mabey if the car battery is toast (bad cell).

if you leave your lights on, and ketch it Fast enough, just resting the car battery for 15-30 minutes, can sometimes get it to start.
so its hard to test , when there may have been enough juice to begin with.

also different starter motors can take much more juice to get a start, a high compression v8 thing might take a 200A pulse, a little Geo 3 cylinder, might start off of a 7a12v a lot easier.

 

[BatteryCharger]

I have a few of those portable jump starters. Each has a 17ah SLA and claims something like 900CCA. I use them all the time, they have no problem starting even a cold 454 without any help from the main battery.

 

[wptski]

[ QUOTE ]
BatteryCharger said:
I have a few of those portable jump starters. Each has a 17ah SLA and claims something like 900CCA. I use them all the time, they have no problem starting even a cold 454 without any help from the main battery.

[/ QUOTE ]
They a really confusing on how they rate those units anyway and it's hard to get a straight answer on how much they are in CCA.

 

[BatteryCharger]

[ QUOTE ]
wptski said:
[ QUOTE ]
BatteryCharger said:
I have a few of those portable jump starters. Each has a 17ah SLA and claims something like 900CCA. I use them all the time, they have no problem starting even a cold 454 without any help from the main battery.

[/ QUOTE ]
They a really confusing on how they rate those units anyway and it's hard to get a straight answer on how much they are in CCA.

[/ QUOTE ]

I don't really care much about the CCA, just as long as they work. /ubbthreads/images/graemlins/smile.gif You have to remeber that most starters even on large V8s use less than 200 amps, anything over that in CCA doesn't really help anything. As for the 7AH SLA originally asked about, I think it might start a smaller engine. They make "compact" portable jump starters, which I believe use something close to a 7ah battery.

 

[wptski]

[ QUOTE ]
BatteryCharger said:
[ QUOTE ]
wptski said:
[ QUOTE ]
BatteryCharger said:
I have a few of those portable jump starters. Each has a 17ah SLA and claims something like 900CCA. I use them all the time, they have no problem starting even a cold 454 without any help from the main battery.

[/ QUOTE ]
They a really confusing on how they rate those units anyway and it's hard to get a straight answer on how much they are in CCA.

[/ QUOTE ]

I don't really care much about the CCA, just as long as they work. /ubbthreads/images/graemlins/smile.gif You have to remeber that most starters even on large V8s use less than 200 amps, anything over that in CCA doesn't really help anything. As for the 7AH SLA originally asked about, I think it might start a smaller engine. They make "compact" portable jump starters, which I believe use something close to a 7ah battery.

[/ QUOTE ]
What if it don't start the first time? Nothing wrong with a little extra CCA. Why do you think that they come in different sizes then?

 

[BatteryCharger]

[ QUOTE ]
wptski said:
What if it don't start the first time? Nothing wrong with a little extra CCA. Why do you think that they come in different sizes then?

[/ QUOTE ]

CCA has nothing to do with capacity. They come in different sizes for people who live in very cold climates, mostly it's just an advertising gimmic. A $30 k-mart battery will start just about any car, yet people still spend $150 on an optima because it says 800cca on the side. Some people really do need alot of CCA, but most don't.

 

[wasBlinded]

The amount of current a battery can supply is dependent on its construction as much as its total capacity. If that 7Ah battery is not designed for extremely high current, its unlikely it could start your car on its own.

Given enough time, it might be able to transfer enough of its juice into your big dead car battery to allow the car battery to start the car, but I wouldn't bet on it. That would be more likely to work if you could wire two of those 7Ah batteries in series to get 24 v, and use that to "charge" your car battery. It wouldn't hurt your car battery, but it might be hard on those little 7Ah batteries.

 

[Lynx_Arc]

I wouldn't recommend wiring 24 volts into a 12v system, unless you isolate (disconnect the battery from the car) you could blow some expensive electronics. Most cheap cables and cheap booster battery kits just help weak batteries out and wont do anything on their own to speak of. If a booster can supply 1/4 of the needed current it can make a considerable difference upon starting when a dead battery will only just crank the engine over once. Probably the best measurement of capacity comparative is to look at the size of a 12v battery and compare it to you 12v gel cell. Both are lead acid and should have similar output. When I buy batteries I get the largest one that will fit in the tray and usually it has the most CCA also. You can even buy a mid level battery that will outdo a high end one if you can squeeze in a larger battery in your tray than recommended.

 

[wptski]

Did a bit of reading and have probably did it before on the CCA/Ah question.

Deep cycle batteries are rated in Ah and car starter batteries are rated in CCA/CA in the USA, elsewhere, they use Ah. But there is Reserve Capacity also, how long a battery was last in minutes at 25A till the voltage goes below 10.5V. It may be as or more important than CCA!

I did find at Associated's site, they make battery chargers, testers, etc. A mention that 200CCA was equal to 33Ah. I also found that there is no conversion for CCA to Ah too! /ubbthreads/images/graemlins/grin.gif

EDIT: Found a link for the info on my Jump-n-Start, 20Ah.

 

[bobisculous]

I once had my Vector charging via the cigerette lighter. I turned the car off and my car stereo (a "non-stock" stereo) continued playing until I unplugged the light.
Not sure if that could start the car though...

This has just been some of my little, yet kinda humorous, background with SLAs.
"Why is my stereo still on? My keys are in my pocket!"

Cameron

 

[PeLu]

1. It is possible to jump start a car with a 1Ah lead acid TMF battery (which I mentioned in another thread), even larger engines.

2. Obsolete cars need much less current to start than modern ones. You can tell the difference by the fuel: Obsolete ones have this smelly stuff called petrol/gasoline, state of the art ones use this wonderful smelling Diesel fuel (for humorless people: this is sarcasm).

3. CCA is the the cold cranking current, it does not necessarly mean that a higher cold cranking current also means a higher (normal temp) cranking current.
For a jup starter, which is kept in the house, the CCA are meaningless, only the CA are of interest.

4. I'm living in a moderate climate here, but I also like it when the car starts at -25°C. So I bought a battery with relatively high CCA (but no Optima, as it costs some $300 here!).

5. You cannot charge one lead acid battery from another with the same nominal voltage (without any step up circuit). Try it and check the current.

 

[BatteryCharger]

[ QUOTE ]
PeLu said:
5. You cannot charge one lead acid battery from another with the same nominal voltage (without any step up circuit). Try it and check the current.

[/ QUOTE ]

You can to an extent. If you hook up a charged battery to a dead one, the charged battery will charge the dead one until the voltage is equalized. Also SLA batteries have a higher voltage than regular flooded car batteries, so they will do an even better job of charging them.

 

[PeLu]

[ QUOTE ]
BatteryCharger said:
[ QUOTE ]
PeLu said:
5. You cannot charge one lead acid battery from another

[/ QUOTE ]
You can to an extent. If you hook up a charged battery to a dead one, the charged battery will charge the dead one until the voltage is equalized.

[/ QUOTE ]

Have you tried it? I tried it and after a very short time (maybe a minute) the current went back to a very low value. You might heat up the empty battery (charging voltage goes down with temp).
Now, I do not have a real need for it, as I have a good intelligent charger (XPeak3) which runs from 12V.

 

[wptski]

Peter:

You've mentioned the Xpeak3 in other threads too. I've tried to search, just to see what it is with no luck. You have any links on it?

 

[eluminator]

I'd have my doubts about charging one 12v battery from another.

A float charger puts out around 13.5 volts, and they can take hours or days to charge a battery.

 

[BatteryCharger]

[ QUOTE ]
PeLu said:
Have you tried it? I tried it and after a very short time (maybe a minute) the current went back to a very low value. You might heat up the empty battery (charging voltage goes down with temp).
Now, I do not have a real need for it, as I have a good intelligent charger (XPeak3) which runs from 12V.

[/ QUOTE ]

Yes, I have tried it. Most of the portable jump starters include a cord with a cigarette lighter plug on both ends so you can do just that. After hooking up one of my 17ah jump starters inside a car with a dead battery the cord became quite hot there was so much current flowing.

 

[wptski]

[ QUOTE ]
BatteryCharger said:
[ QUOTE ]
PeLu said:
Have you tried it? I tried it and after a very short time (maybe a minute) the current went back to a very low value. You might heat up the empty battery (charging voltage goes down with temp).
Now, I do not have a real need for it, as I have a good intelligent charger (XPeak3) which runs from 12V.

[/ QUOTE ]

Yes, I have tried it. Most of the portable jump starters include a cord with a cigarette lighter plug on both ends so you can do just that. After hooking up one of my 17ah jump starters inside a car with a dead battery the cord became quite hot there was so much current flowing.

[/ QUOTE ]
You had better read your instructions! That cigarette lighter plug cord isn't made to start your engine with! It's for charging the JumpStart battery.

It could also be used to keep the KAL memory in your PCM while removing the battery too.

 

[BatteryCharger]

[ QUOTE ]
wptski said:
You had better read your instructions! That cigarette lighter plug cord isn't made to start your engine with! It's for charging the JumpStart battery.

[/ QUOTE ]

It's not for jump starting, but it is for charging a dead battery. That's what the instructions tell you.