High Output alternators?

[joe_julie81]

How common is it to swap the standard alternator out for one with high output, like 140 amp? I would like to hear from someone who has, about what performance improvement you're seeing in terms of how long to recharge truck and camper batteries, and linking the two in the process. Also, what might it cost to do this alternator swap?

[HMS_Beagle]

There are two other nuances to this problem. One is that the truck alternator is set up to sense the voltage on your engine start battery, and will cut the voltage back based on it's state of charge. Since it is always nearly 100 percent on a healthy battery, you will typically find the alternator running at 13.5V or so - healthy for it but not the fastest charge for your camper battery. There are no great ways around this - you can upsize the wiring to the camper (#6 wire is sufficient), that will drag the start battery down closer to the camper battery and make the alternator work a little harder. The best way to overcome this is with a 2nd alternator dedicated to the camper, and remote sensing the camper battery's voltage. Not undoable (common on boats) but complicated.

The second nuance is that while the alternator is rated at 135 amps (or whatever) this is the cold rating, a more or less fictitious number. When it is hot - and it will be very shortly if it is producing 135 amps - the output drops to about 60 percent of the cold rating.

In spite of all that, it is the charge acceptance of the lead acid chemistry that still gets in the way the most. Spend your money on solar arrays - cheaper than a fancy alternator, better for your batteries, and works even when the truck is shut off and the camper in storage.

[time2roll]

Get a clamp-on ammeter and measure the alternator output when the house battery is low. If you are close to the rating an upgrade might be worth while. I am thinking you will be 50 to 70 percent of capacity within a few minutes and more capacity will not help.

[RoyB]

The battery guru's have established the safest way to charge batteries to get the best operating performance along with the best long life.

This is done with using the smart mode voltages you hear about being 14.4VDC, 13.6VDC, and 13.2VDC and this will basically need to feed your batteries at different DC VOLTs changes and certain periods of time to safely charge your battery and not destroy it. I am only talking about the standard flooded cells batteries.

This normally requires you to have a DC OUTPUT capacity of 17amps to 20Amps of DC current and only do your different charging DC voltages for a specified time frame. This will charge your deep cycle batteries safely to its 90% charge state in a three hour time period or to a 100% charge state in a 12 hour time period. Doesn't matter how many DC amps you have available to feed the batteries. These smart mode DC voltages will work with 17-20AMPS DC current for each battery in the battery bank for those specified times.

The only way to make the batteries draw more DC current is to raise those DC Charging voltages but then you will start running into doing damage to the battery cores starting with the boiling out of the fluids... Then the batteries get rather hot and may explode on you....

Having four batteries in your battery bank you only need to have around 80AMPS of DC current available to feed each battery the 17 to 20AMPS DC current that has been identified by the battery experts for the most safe way to charge batteries without damage to their cores.

I am old enough to remember what happened in the 50s when it was normal for a gas station to charge you car batteries in a quick 30 minutes by using maybe 50VDC as charging voltage with a capacity of a couple hundred amps DC current. Those large battery cables would actually jump when this was first applied and the batteries would immediately start boiling out fluids and getting rather hot. Most of them survived the 30 minute quick charge charge but some did not and would explode. I witnessed one such explosion and the top of the battery case blew up into the air some 20-30 feet and battery acid was sprayed all over the motor compartment and on the fenders etc of the car... Not a pretty sight...

In my Air Force days in the late 50s all of the truck mechanics had special enclosures to sit the batteries in while they were being charged to prevent the explosions from doing damage to the personnel...

Glad we don't do this anymore...

You can have all of the DC AMPS in the world but your DC Charging voltages will determine how much DC current is going to be used. I think it actually turns out a lower DC Voltage for a much longer time period does a better battery charge than the higher DC voltage will do for you in quickest time frame of three hours to 90% charge state or 12 hours to 100% charge state...

This is what PROGRESSIVE Dynamics states in their operating manual on how long it takes to charge a battery using the DC VOLTAGEs listed below:
"Progressive Dynamics ran this test on the amount of time it took a PD9155 (55-amp) converter/charger set to three different output voltages to recharge a 125 AH (Amp Hour) battery after it was fully discharged to 10.5-volts.

14.4-VOLTS (Boost Mode) – Returned the battery to 90% of full charge in approximately 3-hours. The battery reached full charge in approximately 11 hours.

13.6-VOLTS (Normal Mode) – Required 40-hours to return the battery to 90% of full charge and 78-hours to reach full charge.

13.2-VOLTS (Storage Mode) – Required 60-hours to return the battery to 90% of full charge and 100-hours to reach full charge."

This is based on having 17-20AMPS DC current available for each battery in your battery bank...

NOTE That Progressive Dynamics doesn't even list using DC Charge Voltages around the 12.0VC range as this would take alot more than 100 hours to achieve a 90% or 100% charge state.


Not an expert here just a shade tree mechanic and have been charging batteries on my OFF-GRID camping experiences since 2008...

In my case if I just charge a battery for 30 minutes off and on during the day my batteries will start going down hill on their performance lines rather quick and eventually will fail... I always start each day off with at least a 90% charge state and never let my batteries go below the 50% charge state... The deep cycle batteries work well with this routine for me... After around 12-14 cycles of the 50% to 90% charge states I always have to do a full 100% charge state which takes a minimum of 12 hours or so using the current days smart mode charging DC voltages.

One needs to talk with folks like MEX from down south on his charging batteries experiences to get a good understanding on getting best results... MEX is a General Motors expert and is especially outstanding in the Alternator field...

I would love to have a high output Alternator setup but would still follow the same safe charging routine outlined above. I could just do this to more batteries in my battery bank at the same time frame...

Roy Ken

[HMS_Beagle]

The charging limit for most campers is not the alternator, it is the wiring from the alternator to the camper batteries. Start spending your money there. Second is the charge acceptance rate of the batteries. If they are standard flooded batteries you might get the to take 50 amps or so, for a short while, when they are really discharged, but the rate will then drop. Good AGMs will take more, about 0.5C (so 100 amps for a 200 AH battery bank) but again only for a short time and only when really low. This is built into the chemistry of a lead acid battery, there is nothing you can do about it. The want to be charged slowly over a long period - which is why solar arrays are such a good idea.

The alternative is LiFePo4 batteries, these can be charged very fast and right to the top at a high rate. The price may be an obstacle though.

[kohldad]

It's not the alternator but rather the wiring and connectors from the truck to the camper. I had the same camper and wiring (2ga) on my 2004 Dodge with 135A alternator and on my current 2015 Ram with 220A alternator. I can still get the same charge rate going into the battery, maybe a little less on the 2015 because of the wiring. I need to beef up the connector as that is the weak link in my current system.

It doesn't really matter how strong of an alternator you have, you will only get about 20A/hr charge rate on a single battery which is the most you should charge anyhow. I typically see about 10-15 A/hr rate but can also have the fridge on DC which pulls another 11A.

The biggest advantage of a higher rated alternator is you are running at a lower percentage of the maximum output which will make the alternator last longer.

[RoyB]

Stop by your local Rescue Squad stations and take a gander of their Emergency Vehicles DC systems. They got all kinds of high performance DC setups going keeping all of their emergency systems working...

When is the last time you saw one them sitting on the side of the with run down batteries haha...

Roy Ken

[joe_julie81]

How big of an alternator could / should I go, and at what cost?

[joe_julie81]

I didn't realize I already had a 135 amp alternator. I'm thinking about getting a 2 or 3k amp power inverter to hook to my truck batteries and running a heavy ext cord to the shore power of the camper, in lieu of a generator. This would replenish my camper batteries after sitting awhile running fans, furnace, lights, etc. I could crank the truck for 20 or 30 min occasionally with a high put alternator to replenish the truck batteries. Anything wrong with this thinking?

[GordonThree]

I often wonder what I could do with the factory 220a alternator that came on my Ram. Sometimes I'm tempted to beef-up the charge line running to my trailer, but that's next to pointless because of the computer controlled regulator.

[GeoBoy]

I don't see why you can't change out your existing alternator to a higher output one. My GMC came with a snow plow package that included a 220 amp alternator.

[ScottG]

Your truck already has a 135 amp alt. Not sure how you would add a second one and have it get along with the puter. Plus, trying to charge a couple of battery's with 150 ~ 200+ amps is going to boil them hard.