8N - What is draining my battery?

Soundguy · May 22, 2006

( good set-up on the one wire GM alternators. He gave me a "12.7 volt, low cut in" model they sell to a lot of street rodders who do a lot of cruisin'. It "auto-excites" at 975 RPM Had to use my original pulley on their reman alternator.) Mine is on a diesel with very little power demand once started, so that helps. Battery stays at 12.2 to 12.7, and the tractor starts instantly, even cold starts well at 7 degrees, so there's little demand on the starter curcuit too. By having the relatively low voltage output of 12.7 )

The low rpm cut in is a good option for 1 wire alternators... however.. I'm not fond of tweaking the charge voltage down..

I believe they are doing this so that there will be very little parasitic load ont he engine from an alternator charging at high current. Due to ohms law, a charge voltage of 12.7v is going to yeild very very low charge current for a battery that nominally sets at 12.6v fully charged. Since you have to have a difference in voltage potentials for current to flow, that leaves you .1v differential from a charged battery to max charge votlage/capacity from the alternator.. In other words, the alt will pretty much just maintaint hat battery, and offset ignition usage. the low voltage is also a bit kinder to points based ignition systems.. all good ideas for street racers.. not necescarilly great ideas for a tractor chargeing system.

( it won't overcharge even if run "wide open )

The standard built in 14.4 or 14.7v regulator use dint he 10si and 12si alts won't overcharge either... 14.x is an acceptable charge voltage range for a lead acid battery using 2.1v cells...

Alternators are extremely efficient at producing power.. most can charge at as little as 300 rpm, and can reach max charge by 1000 rpm... due to voltage regulation, you won't be charging any 'better' at 1000 rpm, vs 4000 rpm..

Soundguy

Soundguy · May 22, 2006

( good set-up on the one wire GM alternators. He gave me a "12.7 volt, low cut in" model they sell to a lot of street rodders who do a lot of cruisin'. It "auto-excites" at 975 RPM Had to use my original pulley on their reman alternator.) Mine is on a diesel with very little power demand once started, so that helps. Battery stays at 12.2 to 12.7, and the tractor starts instantly, even cold starts well at 7 degrees, so there's little demand on the starter curcuit too. By having the relatively low voltage output of 12.7 )

The low rpm cut in is a good option for 1 wire alternators... however.. I'm not fond of tweaking the charge voltage down..

I believe they are doing this so that there will be very little parasitic load ont he engine from an alternator charging at high current. Due to ohms law, a charge voltage of 12.7v is going to yeild very very low charge current for a battery that nominally sets at 12.6v fully charged. Since you have to have a difference in voltage potentials for current to flow, that leaves you .1v differential from a charged battery to max charge votlage/capacity from the alternator.. In other words, the alt will pretty much just maintaint hat battery, and offset ignition usage. the low voltage is also a bit kinder to points based ignition systems.. all good ideas for street racers.. not necescarilly great ideas for a tractor chargeing system.

( it won't overcharge even if run "wide open )

The standard built in 14.4 or 14.7v regulator use dint he 10si and 12si alts won't overcharge either... 14.x is an acceptable charge voltage range for a lead acid battery using 2.1v cells...

Alternators are extremely efficient at producing power.. most can charge at as little as 300 rpm, and can reach max charge by 1000 rpm... due to voltage regulation, you won't be charging any 'better' at 1000 rpm, vs 4000 rpm..

Soundguy

Farmwithjunk · May 22, 2006

I'm inclined to agree with the idea of NOT using a 1-wire alternator on a gasser. But with the relative low battery demand of an easy starting DIESEL, you don't need much to keep the battery at needed level. I was having overcharge problems with the old alternator. As of yet, we still haven't figured out why, but I went through 3 voltage regs. in a year. Along with EACH one of them, a battery. When the battery went south, alternator would max out and fry. (Somewhere, as of yet not known from where, I was getting stray 12V to field on alt. All wiring was original, and still matched diagram. Had several of us puzzled....)The 1-wire solved the problem, or at least ELIMINATED the problem.

Farmwithjunk · May 22, 2006

I'm inclined to agree with the idea of NOT using a 1-wire alternator on a gasser. But with the relative low battery demand of an easy starting DIESEL, you don't need much to keep the battery at needed level. I was having overcharge problems with the old alternator. As of yet, we still haven't figured out why, but I went through 3 voltage regs. in a year. Along with EACH one of them, a battery. When the battery went south, alternator would max out and fry. (Somewhere, as of yet not known from where, I was getting stray 12V to field on alt. All wiring was original, and still matched diagram. Had several of us puzzled....)The 1-wire solved the problem, or at least ELIMINATED the problem.

Soundguy · May 22, 2006

On a 3 wire job, leaving the #2 wire off will cause overcharging, or an excessive votlage drop on the #2 line will also cause an over charge / higher charge issue. I've seen people hook their #2 wire up on the wrong side of a resistor and get some pretty high charge votlage out of the alt .. which cooked the battery.. then kille dthe alt.

Also.. an insuficient charge line will overwork the alternator.. event he 1 wire jobs, due to the voltage drop on the line while charging.. .. it creats the same issue as having a voltage drop on the #2 ( remote sense ) line.. etc.

Soundguy

Soundguy · May 22, 2006

On a 3 wire job, leaving the #2 wire off will cause overcharging, or an excessive votlage drop on the #2 line will also cause an over charge / higher charge issue. I've seen people hook their #2 wire up on the wrong side of a resistor and get some pretty high charge votlage out of the alt .. which cooked the battery.. then kille dthe alt.

Also.. an insuficient charge line will overwork the alternator.. event he 1 wire jobs, due to the voltage drop on the line while charging.. .. it creats the same issue as having a voltage drop on the #2 ( remote sense ) line.. etc.

Soundguy