Our coach has one starting battery.
I spent some time with the search function, and everyone seems to have multiple starting batteries (admittedly with some pretty big engines, too). With a cold engine, I always have to use the boost to turn the engine over. I tested the battery with a load charger, and it shows about 13 volts. Terminals and cables are clean, tight, and corrosion-free.
Is my battery weak? Is this normal for one battery? Did I lose one somewhere? Should I have a bigger single battery? I am OK with the situation, but I feel like it should not be that way, and would like to know, when my furnaces deplete my house batteries, I could still get going.
What say you?
Matt B
Matt,
I personaly would install a second battery. Not sure but the second battery may be better for your starter. Others will hopefully confirm my "gut" feeling.
I use just one 8D flooded battery (available at Sam's Club $150) down to temperatures of 40 degrees. Lower temps than that I would need to use the boost for a few minutes. No problem at -2 degrees when in Flagstaff, AZ. I make it a practice to not spend time in area where the temps are below 65 degrees but, that's just me.
Regards,
Jon Twork
Quoting Matt:"Is my battery weak? Is this normal for one battery? Did I lose one somewhere? Should I have a bigger single battery?"
It all depends on the size of that single battery and the size of your engine. If it's an 8D, it should be sufficient for even the C8.3's. You haven't indicated which engine you have. If you have an M-11 or larger, you might want to have two batteries; again the battery size makes a difference. Like Jon Twork, I use a single 8 D flooded battery, but I routinely switch the boost on just before starting the engine and turn it off immediately afterwards. We have had few issues in 7 1/2 years of using one starting battery.
Don is right on. WHAT single battery to you have.
As he said, if an 8D, and it is in good condition, and it is charged up (your coach did not come with provisions for charging of the chassis battery from the factory), and the connections are clean and tight, that is perfect to start your Caterpillar 3116.
Brett
We have a Cummins C8.3 engine. Our starting batteries are a pair of series 34 Optima Red Top AGM batteries. At 24F, without preheat from a block heater, they would not turn the engine at all. The engine would not turn even with the boost switch on. After that test, we always use the block heater for subfreezing temps.
We started using the same method as Don Hay regarding starting. We turn on the boost before starting and turn it off when the engine is running. The starter is "snappier."
When hooked to shore power, I leave the boost switch on. We have AGM batteries for starting and for house batteries. I chose to use AGM batteries for both banks so that it would be appropriate to leave the boost switch on and charge them together while on shore power. The converter/charger is set to charge AGM batteries.
I do have the Cat 3116, but I have not gone over to look at the battery type yet. Brett, when you say the coach does not have a provision for charging the battery, I am assuming you mean when the coach is not running. Does the alternator charge the battery when it is running? What parasitic loads are usually on the starting battery of a coach like mine?
Would it make sense that the battery is compromised, but the typical load battery tester does not place enough load on it to reveal the weakness?
Matt,
Yes, the alternator, through the diode-based isolator does charge both battery banks.
The converter or inverter/charger did not.
And, your engine is a perfect load tester. Verify that all connections at battery and engine (including ground) are clean and tight.
Check with a digital voltmeter at the battery and again at the large starter lug. If voltage at the battery drops below 11.5 VDC while cranking the engine, battery is bad (or not charged). If voltage while cranking is more than .3 VDC higher at battery than at starter large lug, your connections may be dirty or loose. An alternative is to check between chassis battery positive lug and starter positive lug. Over about .3 VDC while cranking means clean/tighten connections.
As, as suggested, turning on battery boost/combine will add the power of the house batteries to aid in starting. It will also allow the converter, through the house batteries to charge the chassis battery.
Brett
Matt,
My coach never was spinning the starter very fast from the first day I purchased and I thought that was just the M11. All the batteries tested good and I cleaned all the connections which helped very little. I then meet Dave M. at Extreme and he showed me where he added another ground from the engine batteries to the frame. My engine starts the best it every has after adding that ground and some of my flaky dash issues went away. James T. thought they were ground issues, but they still persisted after I cleaned the grounds. Adding the extra ground cured them.
Brett would know if your model coach would benefit from the extra ground.
Thanks,
On any system, to determine if an additional ground would be of value, put a digital voltmeter on ground lug of engine and negative terminal of chassis battery. If voltage reads over about .3 VDC when cranking, consider an additional ground wire and/or clean and tighten existing connections.
Brett
The battery has only one marking, a small C62B melted into the top. The dimensions of the battery are 8 1/2" high, 7" wide and 13" deep, which makes it similar in size to a group 43 or group 27F. It has screw terminals, not slug terminals. The space for a battery is up to 14" high, 14" deep and 9" wide. The space nor the battery is anywhere near the size of an 8D (20 3/4 x 11 1/8 x 9 7/8).
I will check voltage drop when I am relieved of puppy supervision duty.
I put a meter on the battery and "cranked" the engine, though it would not turn over. Voltage at the battery dropped from 12.5 to 11.5ish. I did not check the voltage at the starter. So do you think it is a bad battery, or a too-small battery?
An 8D would be dandy, but it would require fabricating a new battery tray and retainer, and at least one new cable. I would like something that would fit in the existing tray, if it would be adequate.
Ideas?
You will want either a single 8D starting battery or two group 34's to start your Caterpillar 3116.
And when voltage dropped from 12.5 to 11.5 VDC was the engine turning over? normal speed, slowly, not at all?
11.5 under high load would suggest to me that before you spend $$ that you clean and tighten connections both positive and ground, and only then look at spending $$.
You could also verify this by putting a voltmeter from positive terminal of chassis battery to large positive lug of the starter and determining voltage drop. Repeat clean place on engine block to negative terminal of chassis battery.
Brett
Cleaned the ground connections. One connection to the frame was really grimy and really hard to get undone to clean. Could not get the hot on the starter loose to clean it - lots of hoses and stuff in the vicinity, and I could not budge the nut with an 8" handle. It may not be clean, but it sure is tight. Started and ran the engine for about ten minutes and shut it off. Battery showed 13.5 volts, after this short charge time. I attached the load tester to the battery and gave it a load for two ten second intervals. The battery was down to 11.5 volts. Sounds like a battery needing replacement? I have it plugged-in right now, with the boost switch on. I will test the battery again in the AM, and do the voltage drop test if I can get a helper.
We are on the road later this week, so if the battery is faulty, I am inclined to replace like for like, or the biggest that will fit in the allowable space, and indulge Brett's sage advice when time permits.
Hey Matt,
Can you take a photo of that extra ground? It would be very helpful.
Thanks.
My 96 U295 has one 8D starting battery, and when I first bought it it was a little "sluggish" starting. I put a new Interstate 1350CCA in, and it still seemed weak. THOROUGHLY cleaned all connections, and the thing jumps to life the instant you turn the key. Brett is the mastermind here, but IMHO, connections is the 1st place to look, then battery, charging, etc.
Hey Matt,
Can you take a photo of that extra ground? It would be very helpful.
Thanks.
[/quote]
I doubt that mine is an extra. The difficult one went from a post on the side of the starter (with four other wires) to the top center of the crossmember at the front of the engine (rear of the coach). It is about finger-thick and attached to the top of the crossmember. There was just enough clearance to get the bolt and wire out. Were the bolt another 1/16" in length, it would have been captive.
I suspect a fresh battery would improve the situation, but I am surprised that my coach has such a small battery compared to what the rest of you have. This one is about a third the volume of an 8D, so I would suppose it to be about 1/3 the cranking power. The tray is not much larger than the battery, and it all looks stock to my untrained eye.
Matt B
I think you mean Brad, not Matt. (Or Dave M., who helped Brad....)
Michelle
Hey Brad,
Can you take a photo of that extra ground? It would be very helpful.
Thanks
George,
If it does not sleet tomorrow I will take a picture and post. Sleeting in Central Texas is just not right. Where is global warming when you need it?
Thanks,
A lot of good ideas here on the forum about extra ground cables and checking voltage before and during cranking.
When we bought our U300, we installed three Autozone Duralast 27 series batteries @ $80/each to replace the 3 original starting batteries. It spins like a top even down into the teens. On our fire trucks, also Detroits, we had an 8D on each side with a switch in the cab. We always started in the "both" position and got instant starts (on the first turn of the crank) in all temps. Even Ford pickups have a battery on each side for their diesels. A single 8D may be large enough to start most of the smaller diesels, but remember a low cell or just plain age can reduce the amperage available and along with it, cranking RPM.
Diesels start (and run) by compressing air anywhere from 16 to 21 times, depending on the brand. The principal that when a gas is compressed it produces heat is responsible for the ignition (explosion) of the diesel fuel when it is sprayed (injected) into the superheated air. If the engine turns over slowly on the starter, some of the compression (and heat) is lost past the piston rings resulting in lower temperatures for the fuel to try and ignite in. The magic number here is at least 410 F degrees (do the math between cold morning @20 degrees ambient and 410°). Anything lower than 410° and "no start", just white smoke.
Battery cables: excellent idea to make sure the chassis (frame) is well grounded as well as making sure the engine is ALSO well grounded. The starter needs clean non corroded surfaces where the positive cable connects. This goes for the cable also. Starters are usually very easy to get at. You may want to remove it and have it along with it's solenoid checked at your local auto electric shop. Never too many ground cables!
I would not become dependent on using the "boost" function to start the engine. In the case the house batteries are down, you would be SOL.
If you have any doubts, take your rig down to the local auto electric shop. This is their business. They can troubleshoot your whole electrical system and make sure your next trip is worry free or at least the feared first cold morning startup.
Good cranking,
Pierce & Gaylie
93' U300
are made by Interstate (Johnson Control Industries) for Autozone. Nice thing about them is that you can get them replaced almost anywhere. There are about 3 or 4 battery manufacturers in US.
an update on my progress:
Yesterday, I cleaned and tightened the ground wires with no change in symptom.
Today, I tested the battery with a smart charger - 13+ volts and 100 percent charge. Then I cleaned the hot connections at the starter (who said that it was easy to get to???) No change, engine won't turn over, and voltage drops to 11 volts at starter and at the battery when the start button is pushed. No significant difference in voltage at the two points. Engine crank moves, but not enough power to make it spin. Enough for today. The battery cable nuts froze to the rear bumper while I was working!! Thirty-two degrees and 30 MPH wind and freezing rain.
Tomorrow, if the weather permits, I will take a jumper cable and double the engine ground, as a quick double-check to see if it a ground problem.
oldMattB
Strange: The following is the only battery I found with your code number.
You better go with an 8D
It should keep you happy.
Regards,
National Battery C62B Replacement Battery (C62B)
Model Battery Qty Terminal Volts AH L W H Lbs
C62B C62B - F1 6 3.5 5.28 1.34 2.56 1.37
This is a maintenance-free sealed lead-acid battery (SLA) with expected life between 3-5 years. The battery has no-spill design and is multi-functional for both cycle and standby use. It can be operated in any orientation. Commonly used for emergency lighting, UPS (Battery backup), fire alarm and security systems, lighting systems and many other applications. This replacement battery has a 1 year warranty and is guaranteed to meet or exceed OEM specifications and performance.
Matt,
Does your engine have a block heater? I will assume it does and that you've had the block heater on for at least a couple hours before cranking. If this is the case, I would hold the starter suspect (assuming the battery is a good one). I'm certain others with far more experience will add to the possibilities.
Also, remember that an appliance, motor, whatever, will be damaged if the voltage is low while attempting to operate it. This includes the starter. (if this coach has been operated with one battery for many start cycles...the starter could be damaged. You also shorten the alternator life by having it work hard to recharge a very low battery. An appliance (motor) will require a certain amout of power to operate...watts=power=amps x volts. The watts (power) is a constant requirement for the appliance (motor) to operate. If volts are low then the amps are increased to meet the wattage requirement. This increased amperage is usually what damages the appliances...causes fires (wires are spec'd for certain amperage, and the like.
I am having trouble believing that Foretravel would put in such a small battery compartment for a starting battery. My '91 GV has two 8D's, one for starting and one for house. My Cat 3208 starts just fine on one battery if it is not weak. You should have a block heater. If you are plugged into shore power turn it on. If not, start the gen set and then switch it on. It will make a tremendous difference in the ease of starting.
After what you guys have shared, I have trouble believing it as well. The battery holder is welded steel, and looks factory. There is no room for anything much larger than what it has. I could go wider than 14 in a battery, if I modified the battery tray, but I would still be limited to about 8 inches deep. There is no way an 8D would fit in the existing space. The battery is mounted to the passenger side, just inside the hood/ grill/ grate-thing on the back.
I wondered about relocating the battery. I would have to go about half way forward for an open space (in front of the water tanks).
If I was reassured the setup worked when proper, I would know to look for repairs. But it seems everybody is running one or two 8Ds or some comparable setup, which suggests to me my fully-charged, apparently good battery is the problem. Is it just too small to be adequate?
I do have a block heater, but have never used it. We have only been on the road for one night below 40 or so, and it was a surprise. With the "emergency" switch, it started with no problems on that one 20-degree night. How long does it need to be on to be effective?
Starter works fine with the emergency switch on, though I suppose it could be weakened.
oldMattB
I was just looking at Barry's specifications for a 1994 U240. It lists a 1600 CCA gel cell for the engine battery, and a 408 reserve minutes gel cell for the coach battery
Do you think these are both 8Ds, and do you suppose my coach was rewired? I have two 8Ds (I think that is what they are - they are big ones) for house batteries. The house batteries are just ahead of the driver's rear tire.
oldMattB
Matt,
You have one of the better coaches Foretravel ever built. Get the right battery in there and it will perform for you the way it was intended.
Try this for size:
Heavyduty Truck Batteries - Workaholic - 1400 CCA (http://www.interstatebatteries.com/cs_eStore/Products/RT/PID-8D-MHD(Commercial).aspx?dsNavigation=Aro%7e0%2cNs%7eproduct+Type%7c101%7c1%7c%2cN%7e2147384908&Title=Workaholic+-+1400+CCA)
I am trying. The 8D is four inches deeper and 7 3/4 wider than the existing tray, and 2 1/2 inches deeper than the space in the engine compartment, were I to custom-make a tray to take all the available space. There is a tube, I think the intercooler tubing, in the way on the engine side, and the fiberglass frame of the engine door on the outside.
oldMattB
Matt, my 93 U225 had all of the batteries in the compartment on the passenger side in front of the rear tires. I had two series 27 lead acid starting batteries and one 8D house battery. I installed a 4D as a backup in case my other batteries conked out but never had to use it. I just had to make sure I charged it monthly. I know the battery compartment would accommodate two 8D's, maybe three 8D's or one 8D and two series 27 starting batteries. My coach had two heavy duty red battery cables and two black coming out of the chassis into the battery bay. The red/black pair toward the front are for starting and the two toward the rear are for the house.
I too don't think Foretravel installed that battery tray. It sure sounds like someone has messed with your setup. Even my little 230 hp Cummins used two starting batteries. I think it came with two Red Tops.
My '94 Cummins 5.9 too. Mine had two Red Tops which I replaced with two Interstate MTP-27s.
But I am
almost positive that I have two 8D gel coach batteries. But I am not planning on opening that compartment for about 3 weeks. I check and know for sure than. Had to take one of them out when I changed the air cleaner, and boy it sure seems like there were two. I remember being very happy that we only had to take out one.
Quote from Matt: "No change, engine won't turn over, and voltage drops to
1. volts at starter and at the battery when the start button is pushed. "
Matt,
Turn on your block (engine) heater the night before, or at least 5-6 hours before trying to crank the engine next time, especially with the temperatures you mentioned.
And turn you Boost switch ( "emergency" switch) on the night before you plan on leaving provided you are on shore power. It will charge your chassis battery up. But if you have a Trik-L-Start, you don't need to turn on the Boost switch.
Good advice all.
I went back and looked at the coach again. I have two 8Ds in parallel in front of the driver rear axle. I do not see any extra cables. The mount in the battery compartment really looks stock - similar patina on the metal, similar welds to those elsewhere, including a couple that probably could not have been done on an assembled coach. All of the cables, including those to the engine battery have the same type ends, shrink tubing, comparable gauge for application, etc. Aside from not working, the workmanship is quite nice.
There is not enough room among the two 8Ds for an additional big battery, and I like having the two 8Ds for house batteries. I found a Group 30H that will fit in the existing space that claims 1205 Cold Cranking Amperes compared to the 1400 on an 8D, so that might be a possibility.
We will be on the road soon, so all of this will be sorted out later.
Maybe this is something to add to the "what does this switch do" box of Foretravel mysteries.
oldMattB
Pat, if you have two 8D's in the battery compartment, are your two red top starting batteries also there or are they in the engine compartment?
On a 1994 U240, the starting batteries are in the engine room.
1993 U240, they are in the battery compartment in front of the passenger's rear tire.
Brett
Mine has batteries on the driver's side in front of the rear tire, and no room for even one 8d in the engine room. Not sure what I have anymore...
oldMattB
Does it make sense that Matt would have only one starting battery from the factory?
Not one "small" one, no.
Will e-mail a friend who has a 1994 U240 and ask him to check what he has.
Brett
Wish I had a head scratchy little guy!!! The 8D on my '94 U225 is right smack in front of the air cleaner, and the only way to change the air cleaner is to pull the 8D battery. And you know how heavy they are! and my chassis batteries are behind the wheels too, on the other side!
And does it make sense that Matt would only have one chassis battery. With a used coach - anything is possible. I have read of people using a 8D as a start battery. Who knows!!!
George,
Here are the pictures of the extra ground I ran on my coach. I do not know if this will help Matt much and I do not mean to take over his post by any means. I used 2/0 AWG as my extra ground wire which was purchased from NAPA. The picture looks as though the wire is close to my mud flap, but just a bad angle.
Thanks,
This is all so interesting - so many variations on production vehicles. On my '94 the air cleaner is on the driver's side, and if I remember correctly is within 4-5 inches of the engine bay door. No room for a battery between it and the bay door, and no room for anything much larger between it, the oil reservoir, and the other stuff in there. There is not 20.75 inches of space. I must have had a house battery and start battery in the bay. Maybe my current "engine" battery was originally for a trailer - electric brakes, inverter, or the like, and was converted to a start battery. All of it sure looks factory - matching cables, welding, materials, etc.
So the additional ground is simple - big fat wire from negative terminal to frame. The negative wire from my "starting" battery goes directly to the ground post on the starter, then to the engine block, then to the frame. I don't know my wire gauges, but it is as thick as my thumb, probably at least 3/4 inch with insulation. For getting the juice to the starter, it looks like a good setup - between battery and starter, both positive and negative, there is probably not six feet of very fat wire. My hot wire looked like it went directly to the hot on the starter, along with the wire from the house batteries (switched by the emergency switch).
oldMattB
But you have a Cat with a side radiator, while I have a Cummins with rear radiator. That changes our configurations greatly.
Not to muddy the waters, but you need to check each connection where they are crimped on the batt cables (no matter how good they look I found 5 bad connections at the crimp on mine), the way you do this as Bret said one meter lead on the connection on one side the other lead on the wire directly past the connector. Test must be done under a load the voltage you are reading is what you are losing through that connection. A quick test is to attempt to start your coach then go touch all the battery connections both + and - from the battery to the starter if you find one hot it's bad(assuming your starter is OK). Also you need to check starter draw(amps) In short if you are not real comfortable using a volt ohm meter you need to enlist the services of a Hd truck shop with a good electric tech, other wise you will be pulling your hair out this time next month. You also need to look in the books that came from Foretravel with the coach that will tell you what battery(s) is supposed to be in the coach for starting. If you don't have the books you can call F/T tech assistance with your SN or build # I'm sure they can tell you.
On the 92 U240 (at least mine) the batteries are as Brett said, passenger side forward of rear wheels sitting in a tray large enough for 2 8D batteries...one for chassis and one for coach. The 8D starts the 3116 with no problem.
Yes, U240 battery configuration changed between 1993 and 1994 with the move to walk around queen bed/different radiator configuration.
Brett
We have done a good bit of driving since my last post. If I try to restart the engine within about five minutes of stopping, the start battery will do it. More than five minutes, it will not turn the engine over, and I need the boost switch. I think the battery is just too small for the job. Connections, crimps, grounds would all make a difference, but not from one minute to the next, would they?
oldMattB
Batteries take on a "surface" charge as I remember which is why you wait a while to check one after charging. That may be what is happening to you. It really does sound like your battery is too small for the job.
Stop at an Auto Zone or Checker and get it load tested and you will know for sure if it is the battery or not. All of the items you mentioned WILL make a difference. Some will make it a BIG difference.
Regards,
Jon Twork
I didn't mean to indicate that I disagree with this - I know it to be true. I just doubt that the factors would in such a predictable way on a timetable. (insert smiley face thing here)
oldMattB
Matt, my moneynis on a bad battery.
Kent,
Let me hold your money until the answer is discovered. I am impartial and can make sure the right person gets your money. Hey! What else are friends for?
Matt,
Just got an e-mail back from my friend with a 1994 U240. Here is what he said:
My coach came with two MK AGM 8D for the house. I have two Optima red top batteries for the engine. The house batteries are just behind the driver side rear tires. The engine batteries are in the engine room between the engine and the rear bumper.
I don't know George, can I really trust you with my two quarters? And if you held them, what would I have to rub together!!!
I thought this thread of mine needed a capstone.
Short description of problem: A single starting battery with clean connections that tested good under load routinely failed to start the coach. I did not want to convert one of my two house batteries to a starting battery (possibly the original configuration.)
Solution: I replaced the battery with two marine AGM batteries wired in parallel. Each has 800 CCA, and has screw terminals to match the cables present. I was able to take advantage of the battery type and mount them on their sides, which handily fit into the existing battery tray in the engine bay. The positive terminals are higher than the metal structure, so shorting risk is minimized. I chose to orient the negative terminal up for ease of wiring and quick disconnection for other service needs. I used the original mounting bracket and screws, after I installed bolt rings into the existing holes to extent the threaded rods an inch or two, to accommodate the additional height (actually width, but turned sideways!) The threaded screws are angled, to keep pressure on the battery against the mounting tray, and away from the cables.
With the batteries direct from the store shelf, the coach started eagerly.
I have attached photos - they should be self-explanatory.
Paying our great forum back... I hope this helps someone.
Matt B
Batteries ; --- I was A boat dealer for 27 years , sold A few batteries . In A good year we would sell 800 plus , in A bad year maybe only500 . The reason that I mention all this is --name brands-- the most trouble name was INTERSTATE . They have A warrenty all right , but being honest ,or stright up ,was next to nothing . I saw that company stick it to my customers time and time again . I ate many , many batteries just to keep my customers . The company had more reasons to not be honerable about warrenty . Then the pro rated thing . Example ; If you bought A battery ,paid say $120.00 , with A 2 year warrenty . Ok you had it for 22 months , it has A bad cell . Now 2 months left what would you expect to pay ??? how about $149.00 . Well INTERSTATE always had this thing like " that battery has A retail price of $180.00 " Net results you can't win . Are INTERSTATE batteries bad ? ,no not at all ,most are good ,but you will have some nail bitting in A warrenty issue . I would recomend buying batteries at a place that you know will take care of you . Dont be name brand blind .
Matt,
What size cables did you use? They look a lot lighter than the originals. That might give you problems down the road as the batteries age.
I used 4 gauge cables, the largest I could find with factory-installed ring terminals. I figure they will handle half the load of the other cables, and for a short distance, so hopefully they will be fine. They are actually starter cables.
These are great... Select your length.
Battery interconnect cable #2/0 AWG x 18" Red (http://www.solar-electric.com/43110.html)
I am thinking that you will be replacing your starter sometime in the near future. I believe that your coach was probably set up with 4/0 starter cables. By using 2 gauge cable you have reduced your ampacity from 378 amps to a measly 178 amps.
That I would believe, will make it very hard on the starter but, again maybe you don't move around that often.
Regards,
Jon Twork
I see that I misread the data.
You are using 4 gauge cable so the difference is 378 v/s 136 amps. Worse yet.... What was I thinking.....
Regards,
Jon Twork
I firmly believe that tomorrow holds the possiblity for new technologies, astounding discoveries, and a reprieve from my remaining obligations. www. WERV2.com (UnderConstruction)
I am Jon on this one, using the 2 gauge wire, (can not call it cable), is begging for a expensive problem including the starter failure, solenoid burning and hot wire. not to mention lousey starts. :( :o :(
Using the boost switch is needed.
Give it some time, have good investments, it will all work out,
Use the correct cable and your investments do not need to be so great. :)
Cheers
I'm confused...isn't 2 gauge larger and able to carry larger currents than 4 gauge?
The short answer is yes. Perhaps there is confusion among 2 gauge, 2/0 gauge (00), and 4/0 (0000) gauge.
According to information at http://en.wikipedia.org/wiki/American_wire_gauge (http://en.wikipedia.org/wiki/American_wire_gauge), current capacity is:
4 gauge 95 amps
2 gauge 130 amps
00 (2/0) gauge 195 amps
0000 (4/0) gauge 260 amps
Those appear to be values for sustained current. Values for brief usage, such as starting, would be higher. Good practice would be to consider OEM installations as minimum standards. Fatter, shorter wires are better for starting systems.
Okay, I will change the wires.
Yeah, I'm confused. I get that a thicker wire is better than a thin wire. It does not seem like two 8Ds at maybe around 1600 CA each would drop to 260 amperes total through a three-foot-long 4/0 as thick as my thumb. How long is a sustained current? The three seconds it takes to start my engine? Not being fussy, it just seems there should be a lot more to the story.
@Dave Remember only one battery is going through the 2-gauge wire, and the new setup has eliminated the need for the boost switch when starting. The engine starts in 2-3 seconds. God knows how much abuse the solenoid and starter experienced before the setup was changed. I hope the battery was stronger at another time, or the previous owner always used the boost switch. With a full charge, and testing good, the old battery would not turn the engine over.
If I correctly understand the chart from Wikipedia to which I referred, the 0000 cable would carry 260 amps indefinitely and not heat to more than 90C. The cable will not limit the current to 260 amps, but that is a maximum safe current for continuous use if the insulation and environment can withstand heating to 90C. I referred to the chart primarily to direct attention to the relative difference between "2 gauge" cable and "00 (2/0) gauge cable."
For starting the engine, the duty cycle is short enough that heating is usually not an issue. The current to the starter is indeed way more than 260 amps, but the maximum recommended engagement time for a starter motor is likely to be about 25 seconds, with lots of time for cooling between cycles.
It would appear that with that reasoning, you could start the engine once a week using a 16 gauge wire, that would provide plenty time for the cool down :o :o
Hmm. But if your first attempt failed, you should wait another week to try again. While you are waiting, you might as well install some 4/0 cables. (And you could also use the time to clean up the residue from the first attempt.)
BINGO ;D ;D I am just amazed how much traction this simple subject has gotten :)
I knew there was more to it. I have seen people jump-start a car with a coat hanger, and given the brittle metal used, probably has about the same ampacity as a 16-gauge stranded copper wire. Not recommended, but marginally effective.
Maybe we should call the 2/0 and 4/0 double-ought and quadruple-ought to avoid the cornfuzion.
I am proud to have started such a successful post!
I like that! It certainly does help differentiate 4 gauge from 4/0, which many of us,
ahem, present company included :-[, might not have recognized.
Michelle
What you really need to be looking at is the resistance in Ohms per foot. 0 gauge wire has approximately .001 Ohms in ten feet. If you figure that the instantaneous current is 500 amps then the voltage drop would be .5 volts, assuming every thing else is perfect and does not add to the overall resistance of the current path. Since 2 gauge wire has twice as much resistance then there would be a 1 volt drop from the battery to the starter. Bigger wire equals less voltage drop to the starter and the starter does not have to work as hard. You can also see why it is very important to keep all your wiring connections pristine to avoid additional voltage drops and greater harm to your starter. Most of us cannot shorten the wire but we can make the wire bigger.
John, with a starting motor (Inductive load) I would expect the "instantaneous" or "lock rotor" amp load to be much higher. See you have the 3208 Cat, that being a small engine that starts very quickly, you can get by with less battery than when using a larger engine.
As usual the text book info seldom takes into account all that affects the end result.
For the chaps that want to know the real voltage drop, simply use a good recording DC volt meter at the starting batteries, get the reading during a start cycle for max volt drop. Then put meter on the starter and get that volt reading. A very simple and relieable way of finding what is what with out all the guessing.
Another very accurate way to measure voltage drop is to put the positive lead of the digital VOM on the battery positive post and the negative lead on the starter large lug.
Have someone engage the starter. No more speculation needed-- you will now have the facts. And, if you have two batteries on parallel with a smaller gauge wire connecting the two batteries, do this test from each battery positive. Let us know what you find.
Brett