hello,

is it normal for the battery too show 11.6 volts when the engine is off and key is on the ON position?

car starts and the voltage shows 14.1- 14.2 and slowly goes down to 13.8 as i drive normally with lights on ect.

Usually my wot voltage are always 13.4 - 13.7 with twin walbro 450 pumps but recently i have seen voltage dip 12.7 mid WOT

im trying to diagnose if i have a bad battery.

thanks

 

Normal resting voltage for a fully charged healthy lead acid 6 cell battery is 12.6V. For a LFP battery you should see 13.6V. Anything less means it is on the way out. You should not just assume that replacing the battery will fix the problem. You could also have a problem with your alternator, voltage regulator or charging circuit which caused the battery to fail.

 

where is the voltage regulator located?? ya i have dry cell battery which is showing 11.5 with the ignition switch at ON postion.

i did put on a used altinator which made no difference infact the volatges dropped even faster too 13.6 with the car ideling for 5 mins...usually with my old altinator it always stayed around 14.1- 14.2 and then go down to 13.7-13.8 with normal driving light ac ect on.

FIY with the alitnator now when i start the car my ecu shows voltages of 14.2 and eventually when i drive around it drops too 13.7- 13.8, so clearly the altinator is doing its thing... the battery at resting with only car at ON position is 11.5-11.7 volts.

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Do you have an auxiliary amp wired into the car?
Are your lights on when your key is on?
Is your radio on when the key is on?

With the key on, computers and other tings will wake up and begin drawing power.

 

my 450 walbro pump tunes on when the key is on the ON position, the lights are off when car is unlocked, i dont have radio only a digial dash where the radio os supposed to be.

today i took car out and the car started at 14.2 volts then settled to 13.8 and stayed there... with AC off and no lights on.

it's just when the second 450 walbro turns on on e85 and ful boost i sometimes see voltage drop of 12.80 mid wot but it get back up too 13.30- 13.40 volts till red line.

i have NO idea whats going on.


my altinator is working excellent, only thing i can think off is my pumps are drawing too much power and my 45 amp battery isn't big enough 🤷

 

So the computer will vary the alternator output voltage while the engine is running based on the measured electrical load.
There will be a drop at when the key is turned on because of the fuel pump taking some surface charge.

You can put a volt meter on the battery and start the car.
at idle with all electrical loads off you will get a voltage.
Turn on all electronics. Headlights, Heater fan, radio(not loud)
Check voltage again. should get closer to 14.7
If it goes up then everything is fine.

Each computer will do its own thing now a days from car to car.
There no golden rule. except that voltage goes up with electrical draw

 

my relocated pc680 was disconnected and hasnt charged in 2 weeks. shows 12.4 v with the car off, 12.1v key on (fuel pump/acd primed, wideband heating, door light on)

 

i have a digital dash from link which shows me the voltages,

when i start the car my voltage that the ecu sees are 14.2 and then drop too 13.8 - 13.7 with everything on even.

it's just when both 450 walbro pumps turn ON on e85 full boost (2150fic injectors) my voltages drop too 12.8 mid WOT then go back up to 13.6.

i dont understand why it does that... if altinator is working okay and keepup with the voltagea why am i gettting voltage drop mid WOT i see in my logs.

what can i do so my voltages are always 13+ with full boost on WOT running e85.

will going to a bigger amp currently a 45 amp bettery to a 60amp battery help the volatges stay above 13+?

 

What's the battery voltage at rest? (no key on)

 

11.8 is what my ecu is showing on rest and key switch on position... obviously the 450 walbro pump keeps running, also multiple gauges.

 

I would buy a new battery and retest if the battery is a year old or sat while in a discharged state.

Sadly, these cars are getting older and the farther you get from stock the more likely you are to have draw when off. This will hurt the battery over time. Twin 450's or any large fuel pump are going to draw some voltage.

I'm using an odyssey battery in each of my cars and disconnect them after use, then charge them. I still replace them after 1-2 years if I hear the car start to crank slow or they have low voltage. I consider them a wear item.

I also use a Boost a pump . It has a voltage regulator built in. Not saying you need this, but even when its not boosting the amperage may help with voltage loss.

 

ya buying a new battery would be a sensible thing to do for starters.

that being said last night my AC compressor pully broke and the ac compressor was stuck and grinding also which got me thinking that a failing compressor could have caused the issue and not lettiing the altinator spine as much as it wanted to 🤷

i have replaced the compressor , the belt and just to be sure a new adjuster bearing, will test again with e85 and full boost.

if thats not it then put new battery and test again.

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