Is an 80 amp alternator enough to charge 6 golf cart batteries?

[thisoldhippy]

OK so with me putting a diesel in my coach! Do we think that an 80a alternator is enough/ I know the diesel only uses electric to start it. Planning on putting 6 golf cart batteries in it for the coach! Do we think that the 80a will keep all that charged?

[cosmic]

If the Golf cart batteries are good and not weak and losing charge it should be just fine. Are you going to put a gauge on the house batteries so you know when they are getting dangerously low?

[thisoldhippy]

Yes I can do that!!!

[ClydesdaleKevin]

80 amps while driving, even with a gas engine, would be fine for long trips, meaning trips of several hours.  Barely adequate if you plan on charging the batteries by idling the engine...you'd have to run the engine a LONG time to fully charge 6 golf cart batteries, especially if they are way down on charge.

How do you plan on charging them while parked?  Solar?  Just off of shore power/genny power and your converter/charger?

Solar is a huge undertaking, and pretty expensive, although if you go to my posts about solar you'll see that I figured it out with help from everyone here, and on the not so expensive side.

Your converter is your most vital component...and if its the original, it will NEVER charge a huge battery bank completely. I suggest the first thing you upgrade in your system is the converter/charger to something like a Powermax Boondocker...and get the highest amp unit you can afford.

As far as your alternator goes, again, get the highest amp output you can afford. 

Kev

[thisoldhippy]

Thank you I am pretty well locked into the alternator that I have due to the fact that it is also a vacuum pump on it as well! Still thinking out the solar and all that! The convertor is something I have really considered! It has the original in it! Probably time to up grade! I travel long when I go so that is not a problem!  Don't boondock that much at this point but plan on more in the future!

[Acuda4me]

If you are close enough to a big city, with some searching you can likely find at least ONE old school automotive alternator shop that will be able to take your original alternator and upgrade it to a higher amp output for better charging while driving. The kind of place you are looking for will be small, have alternator cases littering it floor to ceiling and have one old guy with a name like "Red" behind the counter. You will know you have the right place if you hand it to the guy, don't say a word and he says "'79 Winnebago?" This goes for carburator shops as well.

[thisoldhippy]

Tried that! It is a nippondenso alternator guy said there where no hop ups for them!

[ClydesdaleKevin]

Another on the cheap option is to carry a pretty high amp plug in external battery charger with you when you travel...just plug it into an outlet and hook the leads to your positive and negative cables on your coach batteries.  DON'T do this if you are using a Powermax...I don't KNOW if I fried my first one by using an external charger in combination with the Powermax, and Best Converter warrantied it, but I haven't dared since, and haven't had any problems with the replacement Powermax.


When using any charger, including your alternator, check you battery levels often and keep them topped off with distilled water.


Kev

[ClydesdaleKevin]

Duh!  D:oH!   Another great option, if you are concerned about the 80 amp alternator, is to make a bracket (or use the AC bracket) and mount another alternator to use for coach battery charging! Duel alternator setups aren't all that complicated to figure out.  Aligning the bracket/pulley, getting the right pulley with the same groove style as the original or another engine belt, and using a longer belt are the most complicated thing about it.  The wiring side is pretty easy, especially if you use an alternator with a built in voltage regulator.  You just isolate the existing alternator to only power the chassis, and run your new alternator wires to the coach batteries.


Kev

[thisoldhippy]

That is what I have been trying to avoid is dual alternators. 

[ClydesdaleKevin]

Absolutely nothing wrong with a dual alternator setup!  If I didn't have such a high output Lestek alternator on our rig already, I probably would have installed a secondary alternator to charge the batteries.  The Lestek puts out 180 amps...200+ in practical tests I've read online about them at the higher RPMs RV engines run at...way more than adequate.


Kev

[thisoldhippy]

Yes but with all the fabbing I'm having to do with the diesel swap. It just adds more!

[85winnerb]

If you are not going to boondock that often why do you need 6 6volts?

[thisoldhippy]

Don't really need them! It is just with me being a LOT weird and retired. I never know when I may decide to stay a couple of weeks out in the brush! Just want to be prepared!

[Oz]

Okay, now that all kinds of options have been discussed... back to the original question:

Is and 80 amp alternator enough to charge 6 golf cart batteries? 

According to Kev, yes...  if you drive a long distance but not just idling.  Assuming the target is to be able to charge them on shorter distance trips and idling, how much more would be needed?

[DaveVA78Chieftain]

Are you asking:
Can I use the 80 amp alternator to recharge the house batteries while boondocking?  Yes however,
1.  The main engine would be a huge fuel guzzler.

2.  You will need to maintain the engine at around 2000 RPM (gas engine) to get real benefit from an automotive alternator.   This may cause overheating due to being stationary.  Oh, noise level would be high too.

3.  Compared to a 3 stage charger, an automotive alternator only operates in stage 2.  Even though the regulator maintains an average voltage of 14.1VDC the amperage rate drops off sharply as the battery voltage rises which results in long charge times (hours not minutes; no bulk charge mode).

4. Automotive alternators are designed for short duration high amp  charging to quickly replenish the energy used for engine starting.  They are not designed for extended periods of high amperage charging and can overheat (burn up) if used that way.  Six golf cart batteries represent basically 3 x 225 = 675AH.  Assuming 50% discharge max to maintain the livelihood of the battery, that's 337AH max available.   90% of 675 is 608.  It would take a  4.5 hours to restore the battery to 90% at the full 80 amp capacity of the alternator (608-337 = 271AH).  The regulator will then start ramping the current down which means it may take 4 more hours to reach nearly 100% recharge (337-271 = 66AH).  Oh, it also takes about 125% charge time to replenish to the full 100% level (takes 420AH to replinish 337AH).  Now think in terms of 2000 RPM for 4 to 8 hours to fully restore the 337AH energy used.   Engine RPM might be a little less for a diesel however alternator output is related to RPM.

5.  Most of Today's (70's and later) automatic transmissions do not really pump oil through the unit in Park.  Long idling time in Park can ruin the transmission.  The 727 used on the Dodge chassis is one of those that do not pump the oil in Park.   At a minimum, the transmission has to be placed in Neutral to maintain oil flow through it for lubrication and cooling.

Dave

[thisoldhippy]

Thank you for all the info! We live at least 100 miles from anywhere so most of our trips are longer! Odds of me ever using up all the power from the batteries is very small! I have a generator in the motor home. I just asked because I have sleep apnea so would like to be able to using my machine with the batteries when I pull over to sleep. Also thinking about solar for maintenance when boondocking. 6 batteries is probably overkill but better safe then sorry.

[gadgetman]

I always heard 5% min charge amps and 13 % max charge amps for proper charging. So if you have a 200 ah battery min would be  5 amps and take forever to charge it and 26 amps max. These figure are really to maintain battery life. 6 batteries is a lot to charge if they really do get down to 60%.


Its really simple, leave the 80 amp alt there, save fuel and stick on 500  watts of solar.................problem solved and now you are always ready for anything .....well except 24 hrs of darkness

[ibdilbert01]

Some things to help you cheat a bit and maybe make this work for you.

1. Sonnax Part 22771-9 (Modifies the 727 to pump while in Park)  http://www.sonnax.com/

2. Change the pulley size on the alternator to increase its RPMs at idle.

3. Use an after market alternator regulator.  (I'm using an incharge 3 stage made by Heart) 
Xantrex has one that measures the temperature of the alternator and will back off its output to keep you from burning it up.

I added a second alternator to mine, a 300 amp and with that we could run the overhead AC driving down the road on inverter.   Really didn't notice a loss in MPGs

[Oz]

I'm going to add a "cheap cheat" ammendment to the awesome post Tim just posted...

Increased idle speed:  Maybe you'd like that while camping but maybe not while sitting at a stop light...

I used this in the winter time to run my rig periodically in the off-season and at campgrounds or home after driving for an extended period of time (cool down period to avoid exhaust manifold problems):

I got a length of 2"x2" wood and put one end on the gas pedal and the other under the arm of the driver seat right armrest.  To "adjust" my idle in park or neurtral, I'd push down or pull up a little on the seat armrest.  Hey, it may not be high-tech but, it definitely worked!

[DaveVA78Chieftain]

Sonnax Part 22771-9 (Modifies the 727 to pump while in Park)  http://www.sonnax.com/

I believe the correct P/N is 22771-09.    P/N 22771-9 is a no find.

Dave