Probs with VN alt in a Hilux,Flat battery

[crwlx4]

Just hooked up vn 85 Bosch alternaters to some Hilux`s,The lux`s have external regultors I replaced that with a relay and Ran the charge wire straight to the battery,The prob is that the battery`s keep going flat when sitting for a while ,Is running the charge wire straight to the battery the prob?

[PanthaVS]

you got a multimeter?

generators/alternators run what is called a "constant voltage" charging system.

Whilst the engine is running test the output voltage of the alternator across the battery terminals (as if checking the battery voltage).

You should see approx 14volts.

Higher than 14 = Regulator isnt working.
Lower than 12 = no charge coming from the alternator.

[crwlx4]

The alternaters are fine,Its when the vehicles sit for a few days with out starting,Then battery will drain flat.I`m not much of a alternater person but with the charge wire going straight to the battery Was thinking that maybe the alternater will suck a little power while sitting and I was missing a relay or something to go in between.

[PanthaVS]

there's no relay in between, the alternator is direct connection (Via a fusable link)

Disconnect the negative battery terminal and test the "current draw" when the car is sitting there (Not running)

If you dont have any alarms or exotic equipment, then the draw should be minimal... something like 20mA (confirmation required???) as this will be the stereo memory backup.

if you have a large current draw, then disconnect the alternator, from the battery and test again. this will tell you if its the alternator thats the culprit, or something else.

If you have the same (small) current draw, then i would assume the alternator is fine and your battery is fluffed... (Lead acid batteries can only sustain 2-3 dead flattenings, then they won't hold charge)

[crwlx4]

I`ll give that ago,I`ve actually disconnected the charge wire before and the battery didn`t go flat probably just luck,maybe i should check that no power is running through the whole car loos wire touching or something

[kopper69]

Im fairly sure that if the regulator goes in the alternator you will constantly be drawing power from the battery and will run the battery flat when the car is off.