Is there a way to increase alternator output??

[Mitch Alsup]

Originally Posted By: Loobed
I have a 105 amp one now.


105 Amps at 13.5V is 1415 Watts or about 2 HP (of electricity) so the alternator is probably consuming 3-3.5 HP from the motor when the battery is in need of a charge. But ONLY when the battry is in need of a charge.

Most of the time, the alternator is putting out 10-ish Amps even with you playing the stereo loud, another 30 Amp to drive the headlights/taillights while driving at night.

 

[L_Sludger]

I saw an ad for a an alternator fuse that was supposed to increase idle alternator voltage. What happens with Toyota and NipponDenso alternators is that when they are old (180,000 miles maybe), at hot idle the output voltage is pretty low, something like 12.5 volts which is below fully-charged battery voltage in fact. Raising the speed brings the voltage up to a more livable 13ish. The fuse was supposedly a diode that would make the alternator think it's not putting out enough voltage and raise the load to accomodate.
I'm pretty sure I got all of the hows and whys dead wrong in this post, but it's just what I saw.

 

[mechtech2]

Alternators produce less voltage when hot than cold.
Sometimes by a natural phenomenon of resistance, and sometimes by design.
This keeps a hot summer battery from overcharging, and gives more juice in winter when you need it.

 

[440Magnum]

Originally Posted By: mechtech2
Alternators produce less voltage when hot than cold.
Sometimes by a natural phenomenon of resistance, and sometimes by design.
This keeps a hot summer battery from overcharging, and gives more juice in winter when you need it.


That function is built into the regulator. A temperature sensor dials down the charging voltage when the battery is hot. Modern cars actually have the sensor in the battery tray. But as far back as '71, the first electronic regulators (Mopar) had a temperature compensator circuit built into the regulator so that at least it went by under-hood temp.

 

[wrcsixeight]

While that function is built into the regulator, It is also true that a cold alternator is capable of producing higher amps than a hot one.

My alternator's rectifiers were withing 2 inches of my exhaust manifold. A heat shield between the 2 improved Idle speed amperages by 5 amps when hot. But still, hot idle speed amps are still pathetic with my alternator. I have thought about adding a cold air feed tube for the alternator

 

[440Magnum]

Originally Posted By: wrcsixeight
While that function is built into the regulator, It is also true that a cold alternator is capable of producing higher amps than a hot one.



True. A hot piece of straight wire has higher resistance than the same piece when its cold. Just the nature of metals.

 

[meep]

Back to the OP, he doesn't need a larger alternator output due to the reasons mentioned above.

He is correct that he needs a 2nd battery, deep cycle, to handle his duration loads.

As mentioned above, the 30 minute drive home will not suffice for charging a deep-cycle battery however, because there's not enough time involved. THAT case would be better served by using a hybrid deep cycle/starter battery that would accept the charge more readily.... but really no matter how it's done, that deep cycle battery is going to prefer a couple of hours on a charger every night.

If this were going to be a long-term situation, like as a part of my job or something, I'd source a weed eater 4-stroke and direct drive it to a SMALL alternator or permanent magnet motor and basically make a crude low-cost generator that sips fuel. A radiator cooling fan motor would probably be about right. Regulate the output using the rpm...

Or buy a small 1kw inverter genset and run a small battery charger directly wired into the vehicle. quiet, efficient on gas. if you are creative, that genset could find a home under the hood, with the pull start through a wheelwell or something.

M