F150 not charging batteries properly?

[pstephens46]

Have a 2005 F150 TXRD. 460 hours. I replaced both batteries in August 2015. They will not stay charged even after a couple decent runs in same day. Have not added any new electronics. My voltage gauge reads about 13.3 at idle, little higher on plane. My buddy's 2010 F150 reads 14.4 volts at idle and higher rpm. I was hoping to get an idea where to look first?

[boscoe99]

At 13.3 volts the motor should keep a battery charged during use, unless you have other stuff connected to, and drawing current from, the battery.

First thing to check would be electrical connections. From the motor to the battery. The rectifier/regulator may be outputting 14.5 volts or so but it is possible for voltage to be lost along the way. AKA volt drop.

Start by measuring the output voltage directly from the regulator. If it is 14.5 volts there, but not at the battery, then there is a wiring issue to be solved between the R/R output and the battery. Lots of connection points along the way that can be problematic.

If the output of the R/R is substandard then a check of the output of the lighting coil needs to be performed. Low voltage out of the stator will result in low voltage out of a perfectly good R/R.

[pstephens46]

Thanks Boscoe, Ran engine and checked voltage coming out of R/R. 13.8 at idle. Also 13.8 at battery while running. Ran the Yamaha software on it didn't indicate any problem. Is 13.8 substandard? Wonder how effective or reliable the YDS software actually is?

[TownsendsFJR1300]

My 06 F150 has slightly higher voltage, but your in the ballpark..

What voltage does the batteries drop to after what time?

Cranking voltage?

If the batteries pass a load test, sounds like perhaps a bilge pump or something is drawing them down (constant draw). I'd be checking the bilge pump float switch, ascertain the pumps are NOT running (with no water in the bilge). Its something fairly heavy to draw down the batteries so fast...

Also, once your back at dock. measure the batteries voltage. Then disconnect over night. See if they drop overnight. They likely won't.


Read posts 18 and 19 here, it should help:

http://www.600riders.com/forum/fz6-e...tml#post601549

[bajakeith]

Sir, May I approach the bench

what kind of batts did you replace with and do you know for certain the place does a high volume of biz ?? as in battery sales..I have had boats brought to me with brand new looking batts that had sat for a few seasons and sulfated,, but looked damn good.. any how with a good DVM and a few simple tests (5 mins) should show the issue of batt's or Da boat.. OUTBOARD"S like cranking batterys not deep's or AGM or "optima"

[pstephens46]

I normally set the battery switch to both. Finally occurred to me to start with 1 and then start with 2 to figure out who is the weakling. 2 would barely turn the motor over but still showing 12.2 volts. Load tested at car parts place after charging. Good batteries..... So one battery is draining at a much faster rate with selector set to both. Maybe the perko switch is bad? Cranking volts dropped to 8.2 on #2 and 11.5 on #1.

[bajakeith]

Woo Roo

always use fresh batts of the same make,size,style.. and don't use a outboard as a battery charger,,the charging system is designed to "maintain state of charge" NOT to bring back a discharged battery up to fill charge 12.6 or greater

[boscoe99]

I normally set the battery switch to both. Finally occurred to me to start with 1 and then start with 2 to figure out who is the weakling. 2 would barely turn the motor over but still showing 12.2 volts. Load tested at car parts place after charging. Good batteries..... So one battery is draining at a much faster rate with selector set to both. Maybe the perko switch is bad? Cranking volts dropped to 8.2 on #2 and 11.5 on #1.

Something is not adding up. A load test applies a certain amount of current (load) to a battery while the voltage is being monitored. The voltage should not drop below 10.5 volts. The fact that when you are cranking the motor the voltage drops to 8.2 is indicative of a battery that has failed from a load test perspective. Not sure why the battery would test OK at a parts place and not test OK when cranking the motor. This assumes that you measured the 8.2 volts directly on the terminals of the battery.

Swap the position of the batteries and see if the problem moves with the battery.

[boscoe99]

always use fresh batts of the same make,size,style.. and don't use a outboard as a battery charger,,the charging system is designed to "maintain state of charge" NOT to bring back a discharged battery up to fill charge 12.6 or greater

Not sure what you mean. The output available from a Yamaha F150 to recharge a battery is 21 amperes. This is a good bit of current. Much more than a lot of external battery chargers provide.

21 amps to a battery that is half charged should be more than adequate to fully recharge the battery in fairly short order.

Either the current produced by the electrical system on the motor is going to recharge a battery or it is going to be shunted to ground and wasted in the form of heat. Mox nix to the charging system. It does not know or care to know where the current goes.

[TownsendsFJR1300]

Yep, 8.2 volts on the one IS an issue.

11.5 drop, CRANKING, (just on the dash gauge) is about normal on my F150...

Sounds like perhaps the 8.2 is pulling down the overall voltage and your not charging fully due to that bad battery.


In addition to the above, just disconnect the 8.2 and run JUST the other battery. Keep an eye on the voltages and drain.

I'll bet its WAY better as you won't have that "bad battery" drawing from the good one and drawing (and not saving) the charging voltage from the engine.

[TownsendsFJR1300]

Any updates????

[pstephens46]

So I played with the leads to swap batteries. I found that the #2 position over a few hours, would drain the battery to a weak status. Bought a $40 switch and it seems to have solved the problem. Tested by leaving switch to "both" position for a few hours last night and 9 hours today. Thanks for all the input! Once again, this forum saved me a ton of money!

[TownsendsFJR1300]

Thanks for the update, just curious!! Safe boating!