Date: Thu, 9 Apr 2020 15:04:02 +0000
Reply-To: "ddbjorkman@verizon.net" <ddbjorkman@VERIZON.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: "ddbjorkman@verizon.net" <ddbjorkman@VERIZON.NET>
Subject: Re: Alternators
In-Reply-To: <SN6PR10MB28948911CDF00F942FF5EB51A0C00@SN6PR10MB2894.namprd10.prod.outlook.com>
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Thanks guys. Something I forgot to add, and you have touched on is HP consumed by the alternator.I was just curious. Interesting point on the ability of the belt to turn the alternator. As far as I can tell, the 90 amp one in the bus is doing fine. I'll just have to leave the big crockpot at home :-).
Dave B.
-----Original Message-----
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
To: vanagon@GERRY.VANAGON.COM
Sent: Wed, Apr 8, 2020 7:14 pm
Subject: Re: Alternators
Your points are accurate. David has an inline upgrade so there are other alternator options out there.
For the Vanagon though the major limitation to how much "power" you can have available is the wiring. Power hungry circuits need to have the working path upgraded all the way back to the alternator. Of the add ons I see that can cause the most grief include high wattage headlamps and other auxiliary lighting. The factory AC with that large radiator fan is also a large consumer and though needs to be given for add on oil coolers that also need fans. All these loads add up.
For auxiliary batteries thought needs to be given for that load, especially for larger sizes. For uncontrolled charging (relay to alternator) figure 30 to 50% of the A/H capacity of the battery. For larger batteries DC to DC charge controllers should be considered. One problem with uncontrolled charging is that you can charge the house battery too fast damaging it over time.
Regarding the set voltage of the regulator is not mistake or weakness the 13.8 volts is the choice of the OEM. The ideal voltage for a battery is like dancing on a pin head. 2.3v/cell is just about the gassing voltage. With some drop and the voltage dropping a bit more as the alternator and wiring heat up this becomes an ideal compromise for straight voltage charging of low or no maintenance batteries. This allows for bulk charging without off gassing. High voltages especially over long drive times will tend to oxidize the plates and overtime will drive the tin out of grids and into the electrolyte. This causes the charging voltage to drop increasing current. These are the batteries that when placed on a real charger never make voltage and eventually overheat as the chargers never shut off. Most heavy duty vehicles and industrial equipment operate at this lower voltage as the tend to run for extended periods. Cars often go to 14.2 as they are typically used for commuting and shopping trips. Long drives are the exception.
As for driving the alternator, the current produced is limited by the windings resistance. As such at full load if you consider resistance matching for power delivery much of the power being used to drive the alternator is given up as heat. Efficiency is probably less than 70% at 740 watts/HP, you probably need 2HP to drive the stock alternator. Tough ask for that belt set up. I have fitted high output alternators. Most of those actually produce less current at low rpms.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Alistair Bell
Sent: Wednesday, April 8, 2020 11:34 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Alternators
Hey Dave,
I might get some argument about some of the points I’ll make, but’s here’s my thinking.
1. I’m not sure of any owner added electrical load - with the important exception of a LiPO aux battery system - that would make me wonder about the 90A stock alternator being too small.
2. The skinny belt and poor wrap around on pulleys limits how much power you have from engine to drive a larger alternator. I once heard from an electrical tech saying simple vee belt good for up to 120 A. If you did put a 120 A alternator in the van, thats nominally a max of 1700 watts (at 14 volts) of power thru the wee vee belt. Over 2hp!
3. Cleaning joints and or replacing wiring from alternator to starter to battery, not to mention battery to fuse panel, is probably well overdue on a lot of our vans. The point really should be number one.
4. I’m very happy with the stock 90A alternator but with an adjustable volt reg. We can debate what the best voltage setting at alternator should be, based on driving habits, time of year, agm or flooded battery etc etc.
I set mine at 14.5-14.6 at alternator. I get about 14.5 at battery. Voltage drops, maybe 0.2 or so , when alternator hot.
I’ve been using the same reg since 2001 or so. It’s been in two vans I’ve resoldered new brushes in it a couple years ago.
I recommend one for anyone who is comfortable with the idea of adjustment and fine tuning.
Alistair
> On Apr 8, 2020, at 6:51 AM, "ddbjorkman@verizon.net" <ddbjorkman@verizon.net wrote:
>
> Hi all. The gent on his way home with charging problems brought this to mind. At what point, with extra gadgets and gizmos and batteries added to the Westy electrical system, would one want a higher amp output alternator? How many amps? Which ones are best?
> Dave B,
