Alternator rating = rotor speed, not engine RPM. Crankshaft pulley to
alternator pulley ratio is usually like 3:1. So 2k engine RPM = 6k
alternator RPM = max power. Probably varies by model/mfg. Yeah, idle is
usually gonna be a little bit less. A high-output alternator is the
better choice. You can screw around with pulley ratios for more power at
idle, but you run the risk of over-driving the alternator at higher
engine RPM. IIRC, ~18-20k RPM is ungood for it.
My '11 Silverado has a 145A alternator. Dual rectifiers. Maybe triple. I
forget. Idle=600 RPM. Still produces at least 110A based on my clamp-on
ammeter and a bad battery that always pulled about 90A. Probably bad
cells. Made it 7 years. New battery pulled around 100A for 10 minutes or
so to top it off. The typical commute of 15-30 minutes should be ample
time to maintain a battery that's in decent shape/age. The law of
averages, that's what the auto mfgs aim for. Most people don't need 180A
at idle, just like most of our customers don't need 1Gbps, or 100Mbps,
all the time.. or ever.
On 7/11/2017 9:05 PM, Adam Moffett wrote:
My '04 Hyundai Accent has a 90 amp alternator. ....though I never did
figure out how many RPM's they assume when giving you that rating. I
read some conflicting facts on that.
Anyway, I have 1000 watt inverter and I've had approx 600 watts on it
while idling for several hours. I can't prove whether the alternator
kept up or the battery was slowly draining.
------ Original Message ------
From: [email protected] <mailto:[email protected]>
To: "Animal Farm" <[email protected] <mailto:[email protected]>>
Sent: 7/11/2017 8:49:23 PM
Subject: Re: [AFMUG] OT: Road Trip Battery
If you install the isolation diodes, then yes. But that only
prevents a dead starter battery. If you have 3-4 devices all using
50 watts, and you have a 50 amp alternator, you only have 600 watts
total. The air conditioner blower is going to take probably 200
watts, the onboard electronics perhaps 100 watts. So maybe 300
excess. I wouldn’t count on even that much. I have seen aux
connectors fused at 15 amps so that is 180 watts.
My dell has a 90 watt power supply. So two of those running non stop?
*From:* Jaime Solorza
*Sent:* Tuesday, July 11, 2017 6:32 PM
*To:* Animal Farm
*Subject:* Re: [AFMUG] OT: Road Trip Battery
Not at all...Pep Boys and others sell a simple to install dual
battery inverter and heavy duty fuse system. A good quality inverter
would work well and no big thing to install. I use this for wiring
up inverters for vans and buses to a solenoid to start inverter when
vehicle is started. Prevents draining battery..
Jaime Solorza
On Jul 11, 2017 6:14 PM, "Sterling Jacobson" <[email protected]>
wrote:
I've got a cross country family trip from Utah to New York coming
up and I want to wire up a secondary battery to my Toyota Minivan.
I know, maybe I'm crazy, but I want to be able to run all our
electronics on the trip, including maybe a computer for serving
up video (another topic).
I want it on a secondary system so I get more power and don't
kill the main car battery.
From what I gather I would need a sealed battery to avoid fumes
(mostly).
I would need a some sort of control system so the battery can
charge from the alternator, but not drain the main battery.
I need high gage wire between the batteries/alternater along with
fuse, and also between secondary battery and large inverter for
AC power.
Probably not possible to shove another battery under the hood of
the mini-van, but I haven't checked.
Is this a silly idea?
