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New alternator specs
powermaster 47294 150 amp

idle 109 amp
cruise 138
top end 162
volt reg.set point 14.8

my two worries are
predamaged rv battery never stops drawing a load and burns up a $144 alternator(i'll have a toggle hooked to the solenoid) 
and 150 amp alternator cooks the batteries 

should i be worried or not?
My new 2.0l 4 cyl Ford has a 150 amp and it just charges the starting battery only which is a special size Ford model which looks to be a little bit smaller than a group 24.
There is one important spec listed here, that is the 14.8v setpoint.

It basically, when cold, spinning at high rpm, tested at 150 amps output, and the voltage regulator is seeking to bring system voltage upto 14.8v

So anytime the batteries can accept everything the alternator can make, and still be below 14.8v, the alternator will be maxed out and will get HOT.

The trtick is to not idle, parked to recharge but to move, 25MPH+ as the underhood airflow keeps the ambinet temperature the alternator is subjected to down, and the extra rpm turns the alternator fan faster, sucking more of that underhood air through it.

I can;t get the casing of my 120 amp alternator when maxed out, at 65MPH to exceed 136f, but if I get off freeway and sit at a red light max amperage falls to ~50, and temperature skyrockets to the 170 range in less than a minute.

220F is the max.

The voltage regulator controls the output of the alternator. It will send more field current to the rotor in order to produce mroe amperage when there are large loads, like depleted batteries and headlights and blower motor sucking up much of potential max output.

Exactly how the VR decides what voltage to seek can be affected by alternator heat, and many will simply heat up and decide to then only seek 13.6v or so, and 1/3 the amps flow at 13.6 compared to 14.7, into depleted batteries over thick copper.

This heat induced voltage dropping does indeed reduce the workload on alternator, keeping it cooler, at the expense of the battery state of charge once the engine is turned off.

Manual control of the alternator's voltage regulator is my approach, but I spent 14 years allowing my engine computer decide to seek either 14.9 or 13.7v regardless of logic or state of charge of the battery.

An alternator with an Internal voltage regulator, well it appears from the specs yours lists, to always seek 14.8v.

So if your batteries are indeed full, the alternator will make only 1.5 to 2.5 amps to hold a pair of golf cart batteries at 14.8v. Long drives through the desert in summer with full batteries held at 14.8v is hardly great for the battery.

But anytime the batteries are less than full 14.8v sought by the VR, is going to recharge the batteries as fast as possible.

So much depends on the state of charge of the batteries. Babying the alternator can be accomlished by going for undersized wiring between alternator isolation device fuse and house battery bank, but unless one is Idling parked in the heat simply to recharge this strategy is likely goinng to greatly underperform when one is driving 1 hour to the next campsight and wants the well depleted batteries to at least be 85% charged on arrival.

A pair of flooded GC-2 batteries, healthy and depleted to 50%, can likely accept 60 to 80 amps for about 20 to 30 minutes before reaching 14.8v. This is an estimation as I have not actually tested GC-2's

My group 27 Northstar AGM can take 65 amps for that long before reaching 14.7, but it is a low resistance AGM with a huge CCA figure.

If you plan to idle/parked to recharge I would recommend opening the hood and having a powerful fan like a 250CFM bilge blower aimed at back of alternator. if you are driving through the desert with Hot fully charged batteries, well 14.8v is a bit much and there will be some overcharging and extra water usage.

otherwise the 14.8v setpoint, when cold, will likely do a pretty good job.

Now once it gets hot, will it still seek 14.8v?

That is Unknown.

A digital voltmeter with voltage sense leads on house battery terminals, is extremely enlightening, especially with a digital Ammeter reading the amperage into house batteries.

I have the product above showing me amperage into the battery, but Use separate voltmeters that have a dedicated voltage + sense lead. The above meter can show voltage or amperage or toggle between the two.

One puts one battery cable through the ring sensor. No shunt required. Mine is on a positive cable, whereas shunts usually go on the (-)
[-] The following 4 users say Thank You to sternwake for this post:
  • Blacktank (07-09-2018), rvpopeye (07-09-2018), frater secessus (07-10-2018), TWIH (07-20-2018)
i'll have a toggle on the solenoid hot wire so i can turn the house battery charging off when starting and idling and turn it on when at speed

solar is in the plans just listed as luxury at the moment,new batteries too but lets kill this one first,2 year old rv fake deep cycle the prior owner said went dead fast and was flat and well low on water when i got it,doubt the solenoid charging system was working
(07-09-2018, 03:32 PM)Mr.LooRead Wrote: My new 2.0l 4 cyl Ford has a 150 amp and it just charges the starting battery only which is a special size Ford model which looks to be a little bit smaller than a group 24.

this is a 1977 chevy with glass fuses so we will see
I bought two Powermasters for my little car-
They saved a few lbs, but were worthless as they failed.
They didn't appear to be (re?) made very well- You could see red substance covering the windings that rebuilders use.
And it used some crazy set point internal regulator, that functioned horribly.
What's on it now? The one that it came from the factory with in '96, with a billion miles on it.

IF you need a different alternator than the factory specified, and my guess is, since you're asking here you don't, get an OEM one from a junkyard. Aftermarket automotive, especially performance aftermarket, is next to junk.

But it's painted a pretty Black!
Sometimes dweller in 237k miles '07 Grand C-van w/ a solar powered fridge and not much else
[-] The following 1 user says Thank You to MN C Van for this post:
  • TWIH (07-20-2018)
I would still recommend a digital voltmeter on dashboard reading house battery voltage, just to see what your alternator's voltage regulator is actually trying to do, and when. So many people start a cold vehicle, take a voltage reading and assume that is the voltage always held/sought, and this could not be farther from reality.

The 12v fake deep cycle low on water is going to start whistling taps and jump off a cliff once you start asking it to work.

I've got a fairly high quality flooded marine USbattery group 31on the floor of my workshop, it uses a shit ton of water and only gets shallow cycled, perhaps 10 to 12 of the original 130Ah capacity at most 5 nights a week. But itr gets upto a 14.7v for a Few hours via 100w of solar every day.

If I were to ask 50Ah from it in a few hours it would likely fall to 10.5v quickly, and fail shortly after, which would be very inconvenient for me, at the moment.
Some alternators makers that claim a higher output compared to the alternator it is based upon, sacrifice low rpm performance to get that higher rating, which might never be realized in actual use anyway.

I think that base alternator is rated at 120 or 140 amps yet powermaster claims 150.

The best Automotive alternator for the rechargeing of well depleted House batteries would have external voltage regulation . A one wire alternator is internally regulated and the hotter it gets the lesser the voltage is will try and seek. It will get significantly hotter trying to recharge a bank of deep cycle batteries compared to the very slightly discharged starting battery they were intended to recharge.

Hard worked alternators need to be kept cool, but temperature influenced voltage regulation will throttle output as the alternator temp climbs. It will contribute to not having enough juice that night and also to premature battery failure, when driving to recharge is the main recharging source employed.

On the opposite end, if one were able to force the alternator to max output every time the batteries were discharged enough, they could easily overheat the alternator and significantly reduce its lifespan.

The ability of an alternator to dissipate the heat it generates, by heatsinking on the bridge rectifier, and the ability of the alternator fan to move air through the alternator, play huge parts in how hot the alternator gets, and which alternator makes for a better choice when there are depleted house batteries in the charging loop.

I believe the GM CS-144 is the more desirable Gm alternator.

Especially when it has this fan design as opposed to the flat faced fan:
[Image: tff-8112nk_ml.jpg]

The CS-144 is internally regulated though, and Ideally one wants external regulation for best recharging performance. They can be converter to external regulation, though I do not know exactly how.

not sure which GM vehicles come/came with the CS-144, but the junkyard pull is a very good recommendation.

My alternator is rated 50 amps idle and 120 max output, that was only offered by mopar for 2 model years. It has a lifetime warranty from Kragen, now Oreilly autoparts.

I last used that warranty 2 years ago, but wound up using it ~6 times in the first 3 or 4 years pre 2007, due to crappy rebuilds and always asking it to recharge well depleted batteries before I had solar and a better idea of what batteries require.

If you have not yet purchased the alternator then you might be able to use something higher output at lower rpms and be more reliable.

MNcvan's experience with aftermarket alternators is hardly unusual, unfortunately.

When alternators are asked to feed additional depleted batteries, they have to work significantly harder, and they likely were designed around max profit with beancounters and marketers and lawyers all contributing to the shaving of pennies/quality everywhere possible. The engineers pointing out increased likelyhood of failure due to penny pinching, are shushed and derided as they have calculated the majority will fail just outside of any warranty.

They are basically reverse engineered around the warranty, for max profit.
Standard operating procedure in this day and age.

Certainly not every vandweller needs to jump through hoops to get their alternator to try and keep batteries healthy for as long as possible. other charging sources can return batteries to full. more modern vehicles will have hissy fits if their voltage is outside what the engine computer expects to see, and should not be tampered with.

What is important is that the owner of the vehicle/batteries, realize that just because an alternator is rated at 150 or 200 amps, does not necessarily mean that it is also taking great care of the batteries every time the vehicle is driven.

Battery charging is all about the voltage they are brought to and for how long they are there in the universal ideal quest of achieving 100% state of charge, or as close as possible to that ideal.

Alternator output is controlled by the voltage regulator. High amperage can raise voltage faster, but a 3000 amp alternator will not be able to recharge an 85% charged battery to full any faster than a 65 amp alternator, unless there is 65 amps of load on the 12v system other than the battery.

If the 3000 amp alternator is designed to only seek and hold 13.8v, yet the 65 amp alternator is seeking and aiming to hold 14.4v, the 65 amp alternator will charge the battery faster once it takes less than 65 amps to hold 14.4.

So, what voltage is any one wire alternator seeking? 14.8 would be good for battery charging, but those other specs at idle and cruise and Max, make no freaking sense.

What will it really seek and hold? a huge ??. A voltmeter with voltage sense leads answer that question.

How many amps are required to maintain that voltage, is also a great indicator as to state of charge. 50 amps to maintiain 14.7v, nowhere near fully charged, 1.5 amps to maintain 14.7v, likely fully charged or very close to it. Depends on the capacity, and the battery itself.

Ammeter + voltmeter and the observation of them, will remove much of the mystery of battery charging.

The ammeter and voltmeter on a house battery fed by an internally regulated alternator, will likely have the driver disappointed that voltage is not 14.8, but 13.7, and while 45 amps might be flowing if the voltage were 14.8, at 13.7v the amperage the batteries accept, might be as low as 12 amps. 150 amp potential, and 12 amps flowing into those depleted batteries, when 45 could be.

It is what it is, unless acted upon by an external voltage regulator Wink

There are also DC to DC battery chargers that will step up that 13.8v reaching house battery terminals, to 14.5.

Anyway just be aware that the engine driven alternator is likely not charging those depleted house batteries as fast as possible, or even acceptably fast, and that physics are not defied.
[-] The following 2 users say Thank You to sternwake for this post:
  • Blacktank (07-09-2018), TWIH (07-20-2018)
you sure like spending my money,got one on the way,predamaged battery just need to power a led light or two and occasional water pump,when the fridge goes in solar and good battery are a must
already have it in hand
failure is always an option and when they do people leave reviews,1 year warranty 

upgrading from a 10si to the 12si design the wire plug might be in a diferent location but other than that direct fit 

as long as it works and dont boil the battery i'm happy,oem is 10si 45 amp but in the above link he says there are 78 and 94 amp 12si versions so maybe i should of gone that way

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