Author Topic: Car battery transplant: Grand Wagoneer battery into a Dodge Shadow? (Read 3784 times)

Snowdog · « **on:** April 16, 2009, 11:54:56 PM »

I've got a Dodge Shadow with a 4 cylinder 2.2L (I think) engine that has a dead battery. I also have a Grand Wagoneer with a 5.9L V8 with a good battery but on it's way to the junkyard.
Here's the question, is there any risk of damage to the electrical system or starter system if I put a battery with a greater amp capacity into a car that can get by with a lesser sized battery?

Thanks!

Sergeant Bob · « **Reply #1 on:** April 17, 2009, 12:01:08 AM »

The only real considerations are whether it will fit, and the type of connections the battery uses. If those two things are compatible, there is no reason you can't use it.

Nick1911 · « **Reply #2 on:** April 17, 2009, 03:46:09 AM »

Quote from: Snowdog on April 16, 2009, 11:54:56 PM

is there any risk of damage to the electrical system or starter system if I put a battery with a greater amp capacity into a car that can get by with a lesser sized battery?

No risk of damage that I can see.

Physical constraints will probably stop your plan cold, though.

Snowdog · « **Reply #3 on:** April 17, 2009, 05:28:39 AM »

I suspected it would be kosher but just found myself having one of those feelings that something was being overlooked... something stupidly simple.

They're both top-post designs and the base in the Shadow doesn't look like it would hamper the installation of a larger battery.

Thanks for the help!

charby · « **Reply #4 on:** April 17, 2009, 11:20:45 AM »

12 volts DC is 12 volts DC no matter what size of the package.

Brad Johnson · « **Reply #5 on:** April 17, 2009, 12:27:43 PM »

As long as it will physically fit and the terminals are in the right place, there's not problem at all.

Brad

RocketMan · « **Reply #6 on:** April 17, 2009, 01:34:48 PM »

Granted, 12Vdc is 12Vdc, but will the charging circuit of the Shadow support the charging current requirements of the larger battery from the Wagoneer?
Larger batteries typically draw greater initial charging currents. You may blow a fuse or three.

Gewehr98 · « **Reply #7 on:** April 17, 2009, 01:39:52 PM »

That won't even bother it. It just won't charge at the same rate as a vehicle with a higher-output alternator.

It's not as if the Shadow's dumping amperage into a dead short, RocketMan.

RocketMan · « **Reply #8 on:** April 17, 2009, 01:42:27 PM »

If the Shadow's charging system has decent current limiting features built in, yes. If not, well...

Chances are he'll be fine. At most, he may have to up a fuse rating.
I need to go back look at battery tech. I don't remember if internal cell resistance is affected by cell geometry. It's been awhile.

Nick1911 · « **Reply #9 on:** April 17, 2009, 01:44:48 PM »

Quote from: RocketMan on April 17, 2009, 01:34:48 PM

Granted, 12Vdc is 12Vdc, but will the charging circuit of the Shadow support the charging current requirements of the larger battery from the Wagoneer?
Larger batteries typically draw greater initial charging currents. You may blow a fuse or three.

I don't think this would be an issue. The charging circuits are built to withstand the maximum alternator output.

Consider if you left your lights on, and drained the stock battery completely flat. A friend jump starts you. At this point, your battery is mostly flat.

The voltage regulator senses lower then 14.4v, and applies power continually to the armature. At this point the stator is putting out maximum power into the battery. This continues until the voltage regulator senses 14.4 volts, then it starts modulating power to the armature to maintain this voltage level.

With this understanding in mind, all that will really change is that the alternator will have to put out maximum power a little longer to charge a flat battery. Standard starting, running, and driving should remain mostly unchanged.

coppertales · « **Reply #10 on:** April 17, 2009, 02:06:28 PM »

With every car I have ever owned, when the original battery died, I installed the highest amp battery I could find. Never a problem. As stated above, 12 v is 12 v. A 20 amp alternator will just take twice the time to charge a 200 amp battery vs the original 100 amp battery. But, you are never going to have to completely charge the battery after a start up anyway. If the battery is completely dead, you remove it for a charger....It is the physical size and terminal layout that is the controlling factor here.....chris3

RocketMan · « **Reply #11 on:** April 17, 2009, 02:16:42 PM »

Keep in mind that most vehicle charging systems are voltage limited, not current limited.
Again, he'll probably be fine, but...just sayin'.

Tuco · « **Reply #12 on:** April 17, 2009, 02:33:24 PM »

Car Batteries are full of strong acid, btw.

If it doen't fit quite right, rig SOME way to keep it in place. You don't want a battery flopping around loose in there.

I've used chain and bolts, but not too tight! Battery housings will crack.

A paste of water and baking SODA works nicely to clean off terminals and that fuzzy blue corrosion. Use a 1" paintbrush. And wear safety glasses.

Brad Johnson · « **Reply #13 on:** April 17, 2009, 02:53:19 PM »

Quote from: RocketMan on April 17, 2009, 02:16:42 PM

Keep in mind that most vehicle charging systems are voltage limited, not current limited.

A higher-amp battery won't cause the alternator to start charging more. The alternator is inherently limited to its max output no matter what the battery size or current capacity

For automotive charging purposes the battery's current rating is irrelevant. All a high-current battery will do is increase the current capacity in the case of higher demand on the battery. The only time battery current capacity would be a problem is if the alternator could supply more ampherage than the battery could safely absorb. (In other words, hooking a car alternator to a 12v R/C NiCad pack probably isn't the best idea.) An automotive alternator's output hasn't the slightest hope of exceeding the current carrying/absorbing capacity of most automotive batteries.

You could strap a thousand batteries together (parallel, of course) and it wouldn't make any difference. The alternator would still hum merrily along at it's rated output, though a 100amp alternator charging that massive bank of cells would barely be a trickle on a per-battery basis.

Brad

Nick1911 · « **Reply #14 on:** April 17, 2009, 03:13:10 PM »

Brad: Exactly. And stated must better then my attempted exclamation.

An alternator at full excitation will only output a certain amount of power. It matters not the capacity of the battery absorbing that charge.

RocketMan · « **Reply #15 on:** April 17, 2009, 03:26:11 PM »

Quote from: Nick1911 on April 17, 2009, 03:13:10 PM

An alternator at full excitation will only output a certain amount of power. It matters not the capacity of the battery absorbing that charge.

There you go. That's the part of the equation I was missing. Thanks, Nick.

Brad Johnson · « **Reply #16 on:** April 17, 2009, 03:39:46 PM »

Quote from: Nick1911 on April 17, 2009, 03:13:10 PM

An alternator at full excitation will only output a certain amount of power.

Something about that statement is... well... :D

Brad

RocketMan · « **Reply #17 on:** April 17, 2009, 03:58:37 PM »

fistful would call that a "sex positive alternator."

mtnbkr · « **Reply #18 on:** April 17, 2009, 04:04:17 PM »

Quote from: RocketMan on April 17, 2009, 03:58:37 PM

fistful would call that a "sex positive alternator."

Would that make the British Lucas Electronics version a "sex negative alternator"?

Chris

don · « **Reply #19 on:** April 17, 2009, 06:06:41 PM »

the amount of current that the battery draws from the alternator is a function of the battery not the alternator. If the alternator could put out an infinite amount of current it matters not,the battery will draw only so much and that depends on the resistance of the battery. If the resistance of the battery were low enough it could conceivably draw enough current to damage the average alternator.

Nick1911 · « **Reply #20 on:** April 17, 2009, 06:08:35 PM »

Quote from: don on April 17, 2009, 06:06:41 PM

the amount of current that the battery draws from the alternator is a function of the battery not the alternator. If the alternator could put out an infinite amount of current it matters not,the battery will draw only so much and that depends on the resistance of the battery. If the resistance of the battery were low enough it could conceivably draw enough current to damage the average alternator.

That's actually a great point.

The questions is, is there a relationship between battery capacity and internal resistance?

Brad Johnson · « **Reply #21 on:** April 17, 2009, 07:16:53 PM »

In strictly technical and very nitpicky terms, yes. In simple everyday terms, no.

Sure, plate materials, electrolytes, and conductors all play into both but for everyday purposes the two are pretty much exclusive. On one end of the spectrum there are deep-cycle batteries that will power stuff forever but won't support much in terms of load. On the other end there are batteries that can deliver hundreds of amps on demand but have limited capacity. Most automotive batteries are a reasonable comprimise between capacity and delivery.

Brad

Hawkmoon · « **Reply #22 on:** April 18, 2009, 10:58:54 PM »

Quote from: RocketMan on April 17, 2009, 01:34:48 PM

Granted, 12Vdc is 12Vdc, but will the charging circuit of the Shadow support the charging current requirements of the larger battery from the Wagoneer?
Larger batteries typically draw greater initial charging currents. You may blow a fuse or three.

Ummm ... no, they don't. The amount of current draw while starting is determined by the size and compression ratio of the engine, and the efficiency of the starter motor. Either the battery has enough Moxie to do the job, or it doesn't. If the battery has more Moxie than needed, it just means the alternator has to work LESS hard to recharge the battery after starting, because the battery hasn't been drawn down as much.

If it fits physically, the battery with the highest amperage rating is always better than one with a lower rating.

Quote from: RocketMan

Keep in mind that most vehicle charging systems are voltage limited, not current limited.
Again, he'll probably be fine, but...just sayin'.

Also incorrect.

The voltage regulator shuts down the alternator when the battery voltage reaches the operating range, but alternators have a maximum output capacity, in amperes. For example, police vehicles, fire vehicles, ambulances and such all have high output alternators because they need to constantly replace all the "juice" consumed by things like auxiliary lights, sirens, radios, etc. The voltage regulators are still set for the same threshold, but te alternator is capable of cranking out higher amperage within the prescribed voltage range.

Hawkmoon · « **Reply #23 on:** April 18, 2009, 11:07:32 PM »

Quote from: Nick1911 on April 17, 2009, 06:08:35 PM

That's actually a great point.

The questions is, is there a relationship between battery capacity and internal resistance?

Alternators are typically trashed when a REALLY dead battery is jump started, and then disconnected and left for the alternator to recharge without first recharging the battery with an external charger.

don · « **Reply #24 on:** April 19, 2009, 12:30:18 AM »

Hawkmoon is correct. Alternators produce AC electricity which is rectified, changed to DC, by diodes in the alternator. If too much amperage goes through the diodes they will fail. A dead battery can pull enough amps to fry the diodes. This assumes that the vehicle is jump started; however, most batteries are not completely dead. The instructions for my car say not to jump start it.

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Author Topic: Car battery transplant: Grand Wagoneer battery into a Dodge Shadow? (Read 3784 times)