f150 won't start on just 1 battery

[pstephens46]

I ll try that , don't know if I'll have enough cable to go directly to the battery

Helpful to use another person. Just as soon as you start, the wife will haul ass to Sam's or some other 3hr shopping destination.

[gsdanno1]

I ll try that , don't know if I'll have enough cable to go directly to the battery

[boscoe99]

Try these procedures and let us know what you observe.

[panasonic]

just re did : Batt1 cranking, positive 4.6 volts +/- , negative 1.2 volts +/- . Batt 2 cranking , positive 4.6 volts =/- , negative 1.2 volts +/- . there wer several non engagements of the solenoid , which has gotten worse throughout testing this afternoon and evening , probably from lack of voltage . In the morning ,I'm going to try and visually isolate the positive cables at the switch . I just can't see them through the wiring mess in the console. I was able to physically grab them at the switch to clean them , but wasn't able to follow them with any certainty. Thanks again to everyone , I didn't think I'd have another 5 page + thread !

OK I know you are frustrated, I would be too. So looking at your numbers above that's a big voltage drop, BUT, it is not clear that the batteries where fully charged when you did the test. So.

Where the batteries fully charged when you did the test?

Are you sure that the readings where Volts and not Millivolts?

My advice would be to charge the batteries fully and carry out the voltage drop test again, yes again. Test got to be done correctly or the results are going to be invalid.

Also as another member suggested several times, take a set of boOster cables and known good battery, disconnect the boat wiring from the starter and hook up the battery directly to starter. If it turns over normally on the single battery then you know your starter is NOT the trouble. Can you do this?

[gsdanno1]

I've done every test everyone has recommended and posted results , I am no closer to solving the problem than I was last week

[gsdanno1]

I did that , posted results in post 46 , it dropped to 10.4-10.8 volts

[TownsendsFJR1300]

I will repeat myself , at the risk of being crude.
you have a load tester.
it is called a starter.
use it.
hook the meter leads to the + and - terminals.
crank it.
should not drop below 11v.
if that passes do a drop test on the batt leads.
the hull wireing is irrevalent.

Going direct to the starter absolutely will work fine BUT the OP is NOT doing that.

He's going thru the broken system so he will be chasing his tail..

If the hull wiring / accessory is draining his "good" battery as he won't check it, it certainly will kill / ruin a battery...

[rodbolt17]

I will repeat myself , at the risk of being crude.
you have a load tester.
it is called a starter.
use it.
hook the meter leads to the + and - terminals.
crank it.
should not drop below 11v.
if that passes do a drop test on the batt leads.
the hull wireing is irrevalent.

[TownsendsFJR1300]

Load testing the batteries was mentioned before to make sure they are good may be a very good idea.

Just because they were on a charger does NOT mean they will pass a load test. They have a surface charge which is much different than having the amperage to put a load on it..

Your voltages reported, at going thru your system is bad.

RodBolt mentioned using the starter as a load tester(which I do as well). That NORMALLY works fine BUT YOUR current set up/ISSUE is NOT good for doing that test. So in your case, NO, it's NOT "that simple".

*I asked earlier about running a known good battery to the engine(by pass EVERYTHING) and see what happens.. NO RESPONSE, I gather not done.

I'd clean up that mess of spaghetti wiring as well, that may be drawing down / killing your batteries over time..

You'll be chasing your tail for quite awhile unfortunately...

[gsdanno1]

they were load tested in October , boat hasn't run since then , batteries were on charger when n all the balancer work was being done. as much cranking as I've done on it today , they wouldn't be able to recover as quickly as they have been , especially 1 , as that was the one I cranked the most. Additionally , this problem has been plaguing me since the last set of batteries , thought I had it sorted by cleaning the terminals at the power posts , but obviously not. Going to recheck the cables on the power posts tomorrow and wire wheel them to make sure I didn't forget those this morning

[99yam40]

just re did : Batt1 cranking, positive 4.6 volts +/- , negative 1.2 volts +/- . Batt 2 cranking , positive 4.6 volts =/- , negative 1.2 volts +/- . there wer several non engagements of the solenoid , which has gotten worse throughout testing this afternoon and evening , probably from lack of voltage . In the morning ,I'm going to try and visually isolate the positive cables at the switch . I just can't see them through the wiring mess in the console. I was able to physically grab them at the switch to clean them , but wasn't able to follow them with any certainty. Thanks again to everyone , I didn't think I'd have another 5 page + thread !

battery not fully charged or not being able to stand up to the load maybe.

Load testing the batteries was mentioned before to make sure they are good may be a very good idea.

Cells/batteries do go bad

[gsdanno1]

in looking back over everything I've done so far , I may have another separate issue as it concerns the switch wiring. I don't think it will affect the issue I'm having but I believe there is one accessory wired to a battery post on the switch , as opposed to the field/common terminal . I will change that tomorrow . I have the bilge pump wired directly to a battery , bypassing the switch , not that it's a big issue as my boat is on a lift.

[gsdanno1]

just re did : Batt1 cranking, positive 4.6 volts +/- , negative 1.2 volts +/- . Batt 2 cranking , positive 4.6 volts =/- , negative 1.2 volts +/- . there wer several non engagements of the solenoid , which has gotten worse throughout testing this afternoon and evening , probably from lack of voltage . In the morning ,I'm going to try and visually isolate the positive cables at the switch . I just can't see them through the wiring mess in the console. I was able to physically grab them at the switch to clean them , but wasn't able to follow them with any certainty. Thanks again to everyone , I didn't think I'd have another 5 page + thread !

[gsdanno1]

I did ,readings were all over the place , I'll try again and see if I can get something steady enough to write down

[panasonic]

Reading back through the replies I don't think it was clear that you needed to be cranking the engine over with the meter hooked up like you had it. You are trying to see if there is a voltage drop in one or both of the starter cables WHEN they are under load. You do it FIRST with no load to get a baseline reading, then do it again while cranking the engine to put voltage pressure through the cable. I hope that helps you out.