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Posted: 9/26/2018 10:20:01 PM EDT
[#1]
Quote HistoryQuoted:
If the battery has 8 volts with the car off, it is done for. With the car running, and only outputting 12.5 volts, you might need an alternator too. It should be reading 14.4 to 14.6 volts when the vehicle is running. Methinks you've got multiple issues. Wouldn't a dead battery measure less than 12 volts? If I jump it, and let the Mercedes run for an hour or so, won't it charge my battery back up? Assuming nothing else is screwy. |
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Posted: 9/26/2018 10:22:58 PM EDT
[#2]
Quote HistoryQuoted: Just highlighting my ignorance here. Wouldn't a dead battery measure less than 12 volts? If I jump it, and let the Mercedes run for an hour or so, won't it charge my battery back up? Assuming nothing else is screwy. |
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Posted: 9/26/2018 10:25:09 PM EDT
[#3]
Quote HistoryQuoted:
A fully discharged battery should read ~11 volts. 8 volts probably means you have a dead cell. You won't fix that. |
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Posted: 9/26/2018 10:25:21 PM EDT
[#4]
Your jumper cables are getting hot because you're using jumper cables.
Toss those things in the trash and get a box for crying out loud! |
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Posted: 9/26/2018 10:27:31 PM EDT
[#5]
Quote HistoryQuoted:
Your jumper cables are getting hot because you're using jumper cables. Toss those things in the trash and get a box for crying out loud! |
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Posted: 9/26/2018 10:28:41 PM EDT
[#6]
Quote HistoryQuoted: Just highlighting my ignorance here. Wouldn't a dead battery measure less than 12 volts? If I jump it, and let the Mercedes run for an hour or so, won't it charge my battery back up? Assuming nothing else is screwy. A bad battery won't take or hold a charge, and a bad alternator won't charge the battery. That's why you need to test them separately. Seriously, just remove the battery and drive it down to the parts store in your Civic. Let them charge and test it for you, and make them replace it if it's defective. After the battery has been charged or replaced, drive the Mercedes to the parts store so they can test the alternator, as long as it's within a reasonable distance. Even if you got the Mercedes running now, just letting it idle might not be enough to charge it, and you run the risk of getting stranded if you do try to drive it. |
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Posted: 9/26/2018 10:31:06 PM EDT
[#7]
Can I test the alternator wit my multimeter myself?
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Posted: 9/26/2018 10:32:14 PM EDT
[#8]
Quote HistoryQuoted:
The cables in my Civic are cheap. Have better one's in the Pilot, but the wife has it now - carting kids around |
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Posted: 9/26/2018 10:33:45 PM EDT
[#9]
Quote HistoryQuoted:
If the battery has 8 volts with the car off, it is done for. Quote HistoryQuoted:
If the battery has 8 volts with the car off, it is done for. With the car running, and only outputting 12.5 volts, you might need an alternator too. It should be reading 14.4 to 14.6 volts when the vehicle is running. Methinks you've got multiple issues. The completely dead battery was drawing a significant amount of current through your jumper cables, making them hot. Quoted:
Can I test the alternator wit my multimeter myself? Under normal conditions you should be seeing something in the mid-13 to low-14 volt range with the engine running. 8 volts on a battery probably means at least 2 dead cells. In some circumstances, a deeply discharged batteries can be recovered, but it's unlikely. Putting a lot of stress on them in a discharged state just as you have been doing is the worst possible thing if there was any hope of that happening. ETA: Reread the posts, the car only reading 12.5 volts while running could well just be because of the defunct battery. Or, it's possible that the battery is defunct because the alternator is bad... new battery and then test the voltage to see what the alternator is doing. Some auto parts stores can test alternators also. |
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Posted: 9/26/2018 10:34:38 PM EDT
[#10]
All jumper cables need this mod.
Solder, Propane torch, Channel lock pliers, Something metal and diameter of a pencil, Slide the grip cover back exposing the clamp to wire connection. Use channel locks to squeeze the crimp together, then ise the steel round thing, place ot over the overlapping crimp, squeeze the ever fucking shit out of it. This tightens the clamp to wire connection. Use propane torche to heat that connection and start feeding in as much solder as it will take to silver the entire connection. Feed the solder into the end of the cable wire stands, keep feeding it until it comes out and tins the strands on other end of the crimp connection. Do this for all four clamps. This will greatly improve the jumper cables performance. |
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Posted: 9/26/2018 10:38:20 PM EDT
[#11]
Peoples doesn’t think elextristy be like it is......but it do
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Posted: 9/26/2018 10:51:33 PM EDT
[#12]
Quote HistoryQuoted:
Can I test the alternator wit my multimeter myself? I would replace the alternator first as the battery was new and in good condition. It may be fine. Cars don't like sitting, next time unhook the battery and trickle charge it periodically. |
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Posted: 9/26/2018 11:00:19 PM EDT
[#13]
Yep, a very dead or damaged battery will require a lot more electricity to flow, and coupled with thinner jumper cables can create a lot of heat.
Voltage at the battery on a running car should be roughly 14 volts, non running car over 12. At least 11 volts at the battery with a terminal disconnected if the care was running recently. Good luck with it. |
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Posted: 9/26/2018 11:05:28 PM EDT
[#14]
My limited experience with alternators has been around 13.8V at idle, up to around 14.5V at higher RPM.
That's just a ballpark, but it should definitely be higher than 12.5V at idle. |
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Posted: 9/27/2018 7:25:34 AM EDT
[#15]
Bottom line, take the battery somewhere and have it tested. I think it is garbage myself. Yes, your alternator should be outputting more than 12.5 volts, but you obviously have a high current (higher than normal) situation going on and typically with high current draw comes a voltage sag. The alternator is likely "giving it all she can, captain" under these circumstances. Replace battery first, then see if the alternator is ok.
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Posted: 9/27/2018 7:31:18 AM EDT
[#16]
Ground on the engine block to reduce current flow. This is jumping a car 101.
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Posted: 9/27/2018 7:33:26 AM EDT
[#17]
Also, get a flost charger for the battery if your going to let it sit for months at a time.
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Posted: 9/27/2018 7:45:25 AM EDT
[#18]
Quote HistoryQuoted:
You need bigger cables. Have some made out of 00 cable. |
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Posted: 9/27/2018 7:52:56 AM EDT
[#19]
Quoted:
WTF did I do? I am jumping my 1984 Mercedes 300d from my Honda civic. Battery on the Mercedes is super dead. Verified polarity. Mercedes tries to turn over, but not getting enough juice. I checked the cables for good connection and noticed they are more than warm Not an expert, but I have used jumper cables many times. Never noticed this before. Is this because the Mercedes is a beast and pulling lots of current from the Civic? |
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Posted: 9/27/2018 8:00:20 AM EDT
[#20]
Jumper cables work best if you connect them up right and let the jumper car run a while, go have a coffee, take dump , whatever then come back and start up the dead vehicle. What you want to do is charge up the dead battery and start the car off that. The more drained down the dead battery is the longer this will take. Of course if the battery is shot, it's not going to work. Jumping with cables or boxes won't do much if there are underlying problems.
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Posted: 9/27/2018 8:10:20 AM EDT
[#21]
Quote HistoryQuoted: Battery is only a few months old. I put it in, and haven't driven the car |
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Posted: 9/27/2018 8:16:11 AM EDT
[#22]
Former 240D owner here:
As already mentioned your cables are probably not the proper thickness and you're getting resistive heating. Also, did you buy the right size battery? On my 240D it was HUGE because the SOP is to actually keep the starter cranking to aid in cold weather startup until it really fires off. Mine could be a cranky bitch in really cold weather. Make sure you have the idle/choke turned properly too when it's cold or has been sitting. I think my battery weighed more than the engine did. 
Also, check all your grounds on the terminal and elsewhere for corrosion. |
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Posted: 9/27/2018 8:18:06 AM EDT
[#23]
Quote HistoryQuoted:
Also, get a flost charger for the battery if your going to let it sit for months at a time. |
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Posted: 9/27/2018 8:29:52 AM EDT
[#24]
Poor connections are probably causing the heat.
I discovered totally by accident and maybe some one can explain... If you attach to the receiving cars battery posts only, the battery must charge before it will start. However if you attach the neg to the receiving cars engine it will start right away. Wouldn't know why it would matter but it does. So I usually hook it up Neg: engine1->engine2 Pos: batt1+->batt2+ |
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Posted: 9/27/2018 8:35:24 AM EDT
[#25]
Bad connection at the clamps will do it.
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Posted: 9/27/2018 8:51:40 AM EDT
[#26]
Quote HistoryQuoted:
Battery is brand new, but I haven't driven it in a few months. I jumped it yesterday and let it run for 30 minutes. I measured 12.5 volts across the battery while running and assume that meant the alternator was charging it Measures 8 volts while car is off Quote HistoryQuoted:
Quoted:
Cheap Wal-Mart cables, total junk. If they're good cables, buy new battery for dead car, cell shorted out. Edit: If you're jumping it every day maybe you should get a new battery, ya think? Measures 8 volts while car is off |
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Posted: 9/27/2018 9:20:28 AM EDT
[#27]
Quote HistoryQuoted:
Also, this. Quote HistoryQuoted:
Quoted:
Also, get a flost charger for the battery if your going to let it sit for months at a time. |
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Posted: 9/27/2018 10:01:05 AM EDT
[#28]
Throw some dirt on it, it'll be ok.
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Posted: 9/27/2018 10:06:15 AM EDT
[#29]
Quote HistoryQuoted:
If the battery has 8 volts with the car off, it is done for. With the car running, and only outputting 12.5 volts, you might need an alternator too. It should be reading 14.4 to 14.6 volts when the vehicle is running. Methinks you've got multiple issues. |
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Posted: 9/27/2018 10:08:49 AM EDT
[#30]
Reistance
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Posted: 9/27/2018 12:02:55 PM EDT
[#31]
Quote HistoryQuoted:
So I usually hook it up Neg: engine1->engine2 Pos: batt1+->batt2+ Also it's best (for the running vehicle) to jump with a similar type of vehicle. A 4 cylinder car's battery, alternator and computer may not be happy with or willing to allow it to provide the current needed to crank over a V8 or diesel engine. I saw this at a car show where someone tried to jump a late model (Hemi) challenger from a 4 cylinder Willy's Jeep. The challenger wouldn't even try to crank. |
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Posted: 9/27/2018 2:40:41 PM EDT
[#32]
Quote HistoryQuoted:
Throw some dirt on it, it'll be ok.
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Posted: 9/27/2018 3:03:47 PM EDT
[#33]
Quote HistoryQuoted:
Pulling more current than the wire thickness is rated for at that length. Good jumper cables are fucking thick and heavy. Pick up a jump pack. Best money ever spent. |
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Posted: 9/27/2018 3:10:58 PM EDT
[#34]
Quote HistoryQuoted: Battery is brand new, but I haven't driven it in a few months. I jumped it yesterday and let it run for 30 minutes. I measured 12.5 volts across the battery while running and assume that meant the alternator was charging it Measures 8 volts while car is off |
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Posted: 9/27/2018 3:11:23 PM EDT
[#35]
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Posted: 9/27/2018 3:13:15 PM EDT
[#36]
Quote HistoryQuoted:
Too much current for your cheap cables. |
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Posted: 9/27/2018 3:13:32 PM EDT
[#37]
Mercedes battery is dead Jim, it's sucking all the current, not letting it get to starter motor.
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Posted: 9/27/2018 3:14:59 PM EDT
[#38]
Quote HistoryQuoted:
anything can be used to jump a battery if your brave enough..... https://www.AR15.Com/media/mediaFiles/137927/ak_battery-684888.JPG |
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Posted: 9/27/2018 3:16:12 PM EDT
[#39]
Quote HistoryQuoted:
Resistive Heating |
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Posted: 9/27/2018 3:19:44 PM EDT
[#40]
I have a homemade set that were put together from arc welding cables. They never get warm.
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Posted: 9/27/2018 3:20:57 PM EDT
[#41]
Pissed off electrons.
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Posted: 9/27/2018 3:33:48 PM EDT
[#42]
Quote HistoryQuoted:
Pissed off electrons. |
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