Date: Thu, 9 Apr 2020 10:31:59 -0700
Reply-To: Alistair Bell <albell@SHAW.CA>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Alistair Bell <albell@SHAW.CA>
Subject: Re: Alternators
In-Reply-To: <SN6PR10MB28948911CDF00F942FF5EB51A0C00@SN6PR10MB2894.namprd10.prod.outlook.com>
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Dennis,
We’ve debated the volt reg set point a few times in the past, and I respect your position. I’d just like to support my higher set point argument one more time, with this....
I have my reg set at 14.5. I have had it as high as 14.6 but let’s say 14.5 for now.
- the voltage will drop as the alternator heats up. Down to around 14.35-14.4
- the voltage drops as electrical loads applied. in winter, headlights on, heater fan on, re fogger on, wipers on, the voltage can drop ( as measured on fuse panel) to the high 13s.
For my type of van driving in winter, mostly short trips, I want the high reg setting to help charge the battery after the staring drain, even with the high electrical loads you have in bad weather.
I’m not worried about overcharging the battery. In fact, during winter, I plug the van every 3 days or thereabouts, so that the on-board Charger can do an over night charge .
Now in summer...
I can see the issue of too high voltage at reg when going on longer drives. Most of our summer trips only involve a max of 3-4 hours uninterrupted driving. If we were to drive longer I think I might dial down the voltage.
The adjustment , really truly , take less than 5 min.
I have a bit of a complication in my battery set up. I have the standard group 41 starter battery, but I have a 200 Ahr AGM auxiliary battery. The higher volt setting of the reg, is in summer, not hard on the big AGM.
I’m trying to recall how old the starter battery is, I can’t recall exactly but I think it’s close to nine years. It is on its way out, has a mile wide but only an inch deep in capacity now.
I’d like to have more discussion about batteries, maybe LiPO, dc-dc chargers, BMS, etc.
I’d also like to have discussion about my other new hobby horses, less electrical draw and less van weight. Ironic as I’m always diddling with adding electrical things and bits of aluminum to the van.
:-)
Alistair
> On Apr 8, 2020, at 4:14 PM, Dennis Haynes <d23haynes57@hotmail.com> wrote:
>
> 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,
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