Planning to purchase High Output Alternator

[Derskiier]

Hi Everybody,

I plan on purchasing a high output alternator for my subaru 3.0L conversion.

I have an auxiliary battery under the drivers seat and another one (large marine battery) under the back seat (I will post amp hours when I get over to my garage to confirm).

Last summer I took a big trip out West and I had problems keeping the batteries fully charged with the stock alternator. My biggest concern is running my electric truckfridge.

Who has experience with HO alternators?

I am considering a 180 amp HO alternator but found there are also 250 alternators available. This seems like a lot of amperage, but the nice thing about the 250 amp alternator is that the idle amperage is 180 amps.

https://www.dcpowerinc.com/fit/Subaru~Outback~2001~3.0L-H6/11225-250-xp.html

The idle amperage on the 180 amp alternator is 110 amps.

My thoughts are that if I am parked somewhere for a few days to a week and I need to charge my battery to keep the fridge running, that I could just start the van and let it run for a while and the idle amperage of the 250 amp alternator would do a great job of recharging the battery.

I believe the stock alternator is around 90-100 running amps.

Any thoughts or opinions?

Also what do you think of dcpowerinc? They seem like a good company, all USA made parts and made in their own shop. I feel like this would be a quality product.

[E1]

(Edit: stock 1.9L)

I just installed a 90 amp Bosch after losing two rebuilt NAPA 90A alternators in 40,000 hard miles. Both alternator failures have been voltage regulators.

But 90A is absolutely enough output to charge our starter battery and two 100aH AGM house batteries. We gain about half a volt in both house batteries even after only idling for about 20 minutes. The installer used large cable throughout the system so all available power would have as easier path to charging.

Maybe the Bosch won't last, either, but am hoping the rebuilts are the weakness as opposed to over-working them (gut says I'm asking too much of them). So I'm also thinking of up-sizing our alternator as well if the new one fails.
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‘84 Westy, 2.1L with Digijet, 5.43 R+P, GT Gears
"Adding power makes you faster on the straights.
Subtracting weight makes you faster everywhere."
— Colin Chapman

[bluebus86]

bear in mind the battery may not take the full 250 amps during charging, there are limits, specially as battery approaches higher charge state.
you may need to up grade to fatter cables for that kind of amperage if your pulling that much, over two times stock.

what laod is the fridge?
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[Ahwahnee]

[Butcher]

I could be wrong, but the stock alternator gets its power from the starter. All you need is to replace that section with a larger gauge. I certainly would get something that could handle 250a, but it does not have to run all the way to the battery. Make certain the alternator case is grounded too.

[bluebus86]

to put this in perspective, 12 volts at 250 amps is the same power (3000 watts) as 120 volts at 25 amps, My full sized home fridge and freezer is connected to a 15 amp 120 volt circuit, capable of delivering 1800 watts. the fridge uses about 1000 watts maximum of that, about 8 amps. Thus the 12 volt 250 amp alternator could power wise run three full sized home fridge /freezers at same time!
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Help Prevent VW Engine Fires, see this link.....Engine safety wire information

Stop introducing dirt into your oil when adjusting valves ... https://www.thesamba.com/vw/forum/viewtopic.php?t=683022

[E1]

[Derskiier]

Yea I feel like the 250 amp alternator is big! But my biggest concern is recharging the batteries quickly. The fridge runs great when the van is in transit and idle (with charged batteries of course).

After being parked for a day or two in hot weather I found myself having to drive around or let my van run for a REALLY long time to recharge the battery enough to keep the fridge going.

So my thoughts are that if I have something with a good high idle amperage that I could start the van and let it run and it would recharge the battery quickly.

I think I have a lot of research to do.

I need to figure out how much amperage my idle van pulls.

And I need to figure out how fast my current battery setup will charge with (X) amount of amps coming from the alternator.

Also, I may be incorrect, but I am concerned that with too high amperage of an alternator that my idle rpms may run very high? I am not sure if that is how the HO alternator obtains that amperage or if it is strictly internal within the alternator.

[E1]

There's many here better qualified on this but my first wonder is how many volts your alternator puts out... One of ours put out 13.6 and a newer one 14.5 and the difference in charge time was shocking.

Are you opposed to solar? Great reading here about that! If so, I still like portables for not parking in the sun!

By the way, the Missus and I were both raised in Oconomowoc...
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‘84 Westy, 2.1L with Digijet, 5.43 R+P, GT Gears
"Adding power makes you faster on the straights.
Subtracting weight makes you faster everywhere."
— Colin Chapman

[dobryan]

Something does not sound right about your batteries. They should not get depleted in a day or two of use. I have 2 110AH batteries (trolling motor ones) and can get longer than that. Do you have a way to fully charge the batteries? If they are of different construction/type then that will make a difference as well.

And solar is great.....
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Dave O
'87 Westy w/ 2002 Subaru EJ25 and Peloquin TBD

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[bluebus86]

pushi g too much current thru a battery can harm it, there is only so much ypu can push into it then it starts to heat up.

for your fridge, make sure your battery for it is in good health, an old or damaged battery may not have full capacity anymore, and hence die more rapidly. the real solution may be to add an extra battery for the fridge, if you double the battery, you should double the time the fridge will run. also consider if extra insulation may help the fridge run less.

third battery could be .ocated under rear seat, and combined with the second battery (camper equipment battery), you should get two days rather than one out of running the fridge. plus you will be discharging them less for a given time, and that equals longer battery life, as batteries dont do well with near complete discharges as they do with partial discharges.

the problem is battery capacity, so double the batteries will help fix that. heck you could even run a forth battery, then you could go for many days running the fridge. this may be more of a solution for you. you could even have a receptical for a temporary third or forth battery that you only carry on camp trips. if you have another car that will not be used while camping, you could take its battery and use it as a temporary fridge supply (hooked up and capable of being charged by van) when camping. talk about a low cost solution, then ypur only buying the cables and hook up parts


with enough batterries you could park for days with fridge running with no need to run the alternator. so think of increased battery capacity.


good luck, stay cool!
_________________
Help Prevent VW Engine Fires, see this link.....Engine safety wire information

Stop introducing dirt into your oil when adjusting valves ... https://www.thesamba.com/vw/forum/viewtopic.php?t=683022

[E1]

[SSWesty]

Ideally you need a smart regulator to match a high output alternator. In general stock regulators don't put out full amperage all the time so you need a regulator that is matched to the battery bank you are trying to charge. Regulators will spike amperage at startup then taper off, you need something controllable to bulk load batteries. If you buy a 5,000 gallon per hour pump and hook it up to a 1/2" hose you won't pump much water. It's kinda of similar with HO Alternators, you need have the right regulator and cable size to reap the benefits.

Your battery bank isn't that big so it seems either your alternator or regulator is underperforming. Here is a link to a marine regulator used on pleasure boats, this may give you a sense of how to get all the amps out of an alternator.

http://content.westmarine.com/documents/pdfs/BalmarARS5.pdf

[crazyvwvanman]

Read the detailed specs of whatever battery you are planning to use. Typical AGM batteries for example may specify a MAXIMUM sustained charging rate of 20%-30% of the amp_hour rating. So if you have a 100 amp_hour battery it only wants 20-30 amps max for charging. Double the battery size to 200 amp_hours and now it wants 40-60 amps max for sustained charging. Clearly by this our stock 90 amp alternator is already enough for most aux battery installs.

Marine Grade AWG #8 is rated to 80 amps carrying capacity.
Marine Grade AWG #6 is rated to 120 amps carrying capacity.
On long cable runs there may be a need for larger wire to keep the peak voltage drops to a desired level, especially for larger battery capacities.


Mark

[Butcher]

[danfromsyr]

those big Alternators are for high "demands" like a on board inverter or welder or AC or heaters or such.
as mentioned the battery will only absorb what it can willingly convert.
else you risk boiling it.
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[buggnuttz]

how about using a separate small generator to maintain house batteries.easy hookup and probably more efficient than running van motor to keep batteries charged
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owned 39 different VWs so far

[danfromsyr]

I have a 1979 norcold12v fridge in my 1980 ASI camper. far less efficient than a truckfridge.
with 2 deep cycle batteries I get low at about the 4th day depending on temps and use while sitting stationary at our August beach camping.
I've drug the small honda generator to top batteries back up and it's very efficient and quiet during the day hustle/bustle.
but with the efficiency of my 1.8T it's on par with the honda to run for a few hours fuel to charge. and I don't have to lug the additional weight/space of the honda..
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