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Hey my Chrysler 300c 2005 has a battery voltage of 12.5 but when I turn the key it goes down to 9.5 or below and it will crank very slow but wont start and when i stop turning the key the battery voltage goes back up to 12 does anyone know or might know an answer i have no idea what’s going on
 

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Hey my Chrysler 300c 2005 has a battery voltage of 12.5 but when I turn the key it goes down to 9.5 or below and it will crank very slow but wont start and when i stop turning the key the battery voltage goes back up to 12 does anyone know or might know an answer i have no idea what’s going on

:eek:What do you think?
 

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If it drops voltage under load, that battery is dead. You can take it to get it tested, but you'll be buying a new battery. Make sure you get the right one for the 300C as it's a fairly hefty unit and smaller batteries don't seem to cope very well for long.
 

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Another elec thread like this................... here we go. The answer will be the same as previous, that is "battery or leads/connections, what has been checked, how old is battery.

Firstly - what size/type engine? Because V6 won't drop voltage as much as V8 will.

People talking about electrics "love to compete" as I have found. They ignore facts/physics/elec theory, and it isn't helpful, so ignore anyone who tells you your battery needs to read a gazillion volts to start with.

My battery is perfect. When you turn the key on, it reads 12.5 volts (EVIC display). THAT IS NORMAL; in fact, a point or two under that is ok, as 12.5 is normal not under load, ign on gives slight load. Ok, straight away, everybody "But mine/my mates higher......" well, good for them. The Century battery site here says "a fully charged and stabilised battery will read 12.5 volts or over." That is good enough for me. If others think it isn't good enough, then................ I can't help with that, call Century. I quote the site because other forums here were telling people "If your battery EVER reads under 13.6, throw it away......" so they were ditching lots of PERFECTLY GOOD BATTERIES. The other reason I quote Century, is that no one listens to elec facts from people with trade/elec teaching experience. They all want to argue with "but mates said" - (mates that aren't elecs/can't fix the problem).

When I crank mine, it drops to 10 volts until it starts. That is NORMAL. If yours is a V8, higher draw, so 9.5 volts is probably normal. The slow cranking isn't. (Ijust went and cranked mine then to confirm. After sitting overnight, 12.5 volts ign on, 10 when cranking.)

So, there are 3 possibilities. Battery, connections, starter.

How old is the battery? Is it fully charged (if constant small trips/many starts, it may not be)? Has it been load tested?? In the US a battery load tester is about $15, cheap as chips, cheaper than the fuel to drive and get battery load tested at a shop. They are primitive and simple, but will work. Get one of those and try it, it will TELL you if your battery is no good. Battery HAS to be fully charged. And if it comes up as no good, then disconnect it, and check at battery terminals, to ensure it is battery and not bad terminal connection. Test at the battery, not at the jump point in engine bay. Electrically, they should be same point, but that is the point of testing as close to battery as possible.

Check battery connections in the boot (trunk). Either pull them off and clean, or test with a multimeter. They MUST be tested under load, otherwise pointless. I can tell you how to do that (or read many other threads where been discussed before) but load test battery first.

Finally, starter - if starter is drawing too much current, could be the problem. But check two things above first.

In the old days, we would say "Slow to crank? Try starting with gear lever in "N" rather than "PK";" as the Pk contacts get pitted/worn/dirty, wheras the "N" ones NEVER get used; but in these cars that is all elec signal voltages/very little current, and they hardly ever give trouble, but you could try that and see if any difference, just to eliminate it/takes 2 seconds.

Load test your battery first. Info about battery age/is it fully charged would help next time. :)

Good luck.
 

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If it drops voltage under load, that battery is dead. You can take it to get it tested, but you'll be buying a new battery. Make sure you get the right one for the 300C as it's a fairly hefty unit and smaller batteries don't seem to cope very well for long.
Sorry mate, don't agree. ALL batteries drop some amount under load. Unless I misunderstood what you said.

The load testers (common/cheap) ones have a static 100 amp test load. They measure the voltage drop and have a "CCA field" . An 800 CCA battery (see pic) can drop to 10.8 volts and still be within spec for that size battery. Their whole function depends on measuring that voltage drop under a set load.

The same load testers have a field on them that "tests starter" and that field tells you "how much voltage drop is acceptable" when cranking. They have an allowable volts drop of approx 2.5 volts between "resting voltage/load test voltage/starter drop cranking voltage." Saying ""No drop under load" makes every "starter test field" on the load tester (or even the CCA test) void. Again, see pic below. The only you tube vid I can find is confusing, as no one seems to use that starter test/hardly mentioned in the manual for it.

Have a look at the attached pic. If a load tested battery falls within the "800 CCA" field it will test around 11.2 volts. Take that figure and then crank the engine, the "allowable voltage" it can drop to is 10.2. Normal standard. Hence an almost 2.5 volt drop (from resting/no load) is allowed/normal.
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All my old car manuals here - "no load test" for a HK starter motor is "10.6 volts" from a fully charged battery. And that is no load, cranking would drop more. My Triumph Stag spec is "while cranking, 9 volts" and lock torque (never seen in service, check only) drops it to 7 volts. Again, with correct, fully charged battery. That's the spec - from new.

As I said above, my car drops from 12.5 with ign on to 10 while cranking, always has............... and that is normal for the 3.5 V6 for the 15 years I have had the car.

Sucking 300 amps out of a battery WILL drop the voltage level of the battery while providing it. If it doesn't - your battery must be big enough to be on a trailer behind your car. :rolleyes:o_O

I concur that the 300c standard battery is a huge unit, and thankfully, Chrysler have a huge battery compt; unlike other makers that have tiny batt housings that force having those smaller case batteries that squeeze the optimum "plate to acid" ratio; and hence why those small "premium" batteries in many small cars only last 3 years, wheras we get 5 to 7 out of ours. Ya canna change the laws of physics (although marketers try and tell us they can, look at the failure that was the Century gel "torque starter"; tech before it's time.

Cheers mate. :)
 

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Thats interesting stuff OzKen. I normally attempt to charge a suspect battery and it only ever gets one shot at redemption, i think I've only ever had one battery in 45 years deviate from "if it wont crank, toss it". Hence my blanket rule. I dont think I would bother measuring the voltage drop, the no crank situation is enough for me 😁
 

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Thats interesting stuff OzKen. I normally attempt to charge a suspect battery and it only ever gets one shot at redemption, i think I've only ever had one battery in 45 years deviate from "if it wont crank, toss it". Hence my blanket rule. I dont think I would bother measuring the voltage drop, the no crank situation is enough for me 😁
Fair enough mate.

But (seeing not much other info here) I would hate to see this guy bin his battery because "a volts drop" and he has a "lots of small trips/left something on/battery not charged"....................... and his next battery does same thing with same use.

Also - slow cranking can just as easily be dirty terminals as it can be dud battery. Again, knowing what his use is/how old battery is/have recently disturbed terminals would help.

As an radio electro/mechanical fitter, I worked with (and taught, on the elec side) everything from electron theory up to advanced electronics (missile and gun radar and computer) so just trying to share a bit to help out.

:)
 

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Too much writing. Remove battery. Thoroughly clean battery and connections. Fully charge battery. Load Test battery (1,000 CCA tester minimum recommended). If the OP has to ask for clarification on what I just stated, then find a trusted pro. Battery tests good? Begin moving up the 'food chain'.

'Thank you very much and Good Night!!!"

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Too much writing. Remove battery. Thoroughly clean battery and connections. Fully charge battery. Load Test battery (1,000 CCA tester minimum recommended). If the OP has to ask for clarification on what I just stated, then find a trusted pro. Battery tests good? Begin moving up the 'food chain'.

'Thank you very much and Good Night!!!"

View attachment 178301
Was trying to help.

Have NEVER had an elec problem I couldn't fix both at work/at home in 50 years of being an elec, and on every type of elec gear using the principles above.

But explaining how to do it/how to exactly find where the problem is, is "too much writing".

Ok, point taken, won't make that silly mistake again.
 
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