Can you fry an alternator

[agallant80]

My question is can you fry an alternator by having too big of a bank behind it? I realize that it will take long to recharge a 300 amp bank but will it fry the alternator?

 

[theoldwizard1]

Re: Can you fry an alternator

The short answer is no.

 

[bruceb58]

Re: Can you fry an alternator

Should be fine.

Putting in a bank of golf cart batteries? Motor homes do this all the time and the alternators are basically the same with possibly a higher output.

 

[agallant80]

Re: Can you fry an alternator

Should be fine.

Putting in a bank of golf cart batteries? Motor homes do this all the time and the alternators are basically the same with possibly a higher output.

I have 2 80AH battries in bank2 and one 80AH battery in bank2. Just wanted to make sure if I left the switch on ALL while the engine was running that I would not fry anything.

 

[bruceb58]

Re: Can you fry an alternator

On a Bayliner we had, we did that all the time.

 

[theoldwizard1]

Re: Can you fry an alternator

I have 2 80AH battries in bank2 and one 80AH battery in bank2. Just wanted to make sure if I left the switch on ALL while the engine was running that I would not fry anything.

Standrad operation when cruising. Just make sure when you turn off the engine, you disconnect the cranking battery.

 

[NYBo]

Re: Can you fry an alternator

I prefer sauteing them in a little olive oil.

You can certainly shorten the life of an alternator if you try to recharge deeply discharged batteries. The higher current draw leads to higher operating temperatures.

 

[UncleWillie]

Re: Can you fry an alternator

I have 2 80AH batteries in bank2 and one 80AH battery in bank2. Just wanted to make sure if I left the switch on ALL while the engine was running that I would not fry anything.

Three 80AH batteries paralleled, is equivalent to one 240AH Battery.
Your three batteries are actually small compared to commonly used group 27 batteries that are typically ~100AH.
Two would equate to 200AH, against your three at 240AH. Only a 20% difference.

Understand that 100AH batteries do not draw 100 amps when charging, and that a 65 AMP alternator will not necessarily produce 65 amps when charging the batteries. These numbers are ratings and NOT like the 12volt number associated with the batteries.
You may find that the three batteries charge in close to the same amount of time as one, and not over stress the alternator at all.
Yes the alternator will be working harder, but not anywhere near as hard as the numbers would lead you to believe.

Go for it.

 

[jhebert]

Re: Can you fry an alternator

You can certainly shorten the life of an alternator if you try to recharge deeply discharged batteries. The higher current draw leads to higher operating temperatures.

Yes. This is absolutely true. How well a particular alternator will tolerate being operated at the maximum possible current it can deliver for an extended period of time is going to be a function of the design of the alternator. An alternator will have to dissipate more heat at maximum current. If its cooling is not adequate, you could overheat the alternator and damage it.

In general, it is also not a good idea to charge batteries in parallel.

 

[bruceb58]

Re: Can you fry an alternator

In general, it is also not a good idea to charge batteries in parallel.

Of course, if you are using an ACR, this is exactly what is happening.

 

[jhebert]

Re: Can you fry an alternator

Of course, if you are using an ACR, this is exactly what is happening.

Yes, but, with an automatic combining relay, the second battery is only added in parallel after the first battery has reached full charge.

 

[bruceb58]

Re: Can you fry an alternator

Yes, but, with an automatic combining relay, the second battery is only added in parallel after the first battery has reached full charge.

The Blue Sea ACR combines at 13.0V after 2 minutes. The first battery won't necessarily be fully charged yet.

 

[jhebert]

Re: Can you fry an alternator

The Blue Sea ACR combines at 13.0V after 2 minutes. The first battery won't necessarily be fully charged yet.

Yes. The Blue Sea ACR also un-combines if there is 12.75-Volts present for 30-seconds or if there is 12.35-Volts present for ten seconds. If the second battery is at a very different charge level than the first, the Blue Sea ACR will oscillate on and off every 10 to 30-seconds until it escapes by raising the charge on the second battery.

I recommend you watch this excellent presentation at

http://www.youtube.com/watch?v=3P-wqckJ2nM

It will show you how a highly regarded battery manufacturer applies the initial charge to their batteries: they connect them in series--actually it looks like a very long string of batteries in series--and charge them. In this way, the same current is applied to all the batteries as they are charged.

If charging batteries in parallel was a better method, you might infer that manufacturers would use parallel charging; they don't.

 

[jhebert]

Re: Can you fry an alternator

To return to the initial question, can you fry an alternator, I assume "fry" means to overheat. It is certainly possible to overheat an alternator. In fact, damage from overheating is probably the most likely case of damage. Too much heat will:

--melt passive components like wire insulation or adhesives

--cause permanent damage to active components like semi-conductors by breaking down their internal structure

--cause permanent damage to active components like semi-conductors by melting their silicon-based semiconductors

Heat is created in an alternator in proportion, generally, to the current being produced. If that heat is created for a long enough time, it will cause a temperature rise in the alternator and its components. Too much temperature rise, and bad things happen.

 

[bruceb58]

Re: Can you fry an alternator

If charging batteries in parallel was a better method, you might infer that manufacturers would use parallel charging; they don't.

The reason they charge in series is that lower current is used. I have a friend who works for a battery manufacturer. Way easier and cheaper to have 120V feed a series array of batteries for charging purposes.

I know a lot of people that have battery banks for their solar storage. They have a huge battery arrays with batteries in series and parallel.

At least in my BlueSea setup, if I have a battery that is half discharged, the ACR connects and stays connected. It never cycles. Maybe if you have a low current outboard charging it, this may happen but with my I/O alternator. I don't see it happening.

For a house bank in a boat, I actually agree that a series setup is the way to go. 2 6v Trojan high capacity batteries is a way better solution than 2 12V in parallel to get the same capacity.

 

[jhebert]

Re: Can you fry an alternator

For a house bank in a boat, I actually agree that a series setup is the way to go. [Two] 6v Trojan high capacity batteries is a way better solution than [two] 12V in parallel to get the same capacity.

I like your thinking. That is a good solution.

 

[UncleWillie]

Re: Can you fry an alternator

... 2 6v Trojan high capacity batteries is a way better solution than 2 12V in parallel to get the same capacity.

Two 12v 100AH Batteries in Parallel yeilds ONE 12v 200AH BAttery.
Two 6v 200AH Batteries in Series yields ONE 12v 200AH Battery.

There is no difference.
Place both batteries in a box and there is no test you can do to determine which one is in series and which is parallel.

 

[jhebert]

Re: Can you fry an alternator

Two 12v 100AH Batteries in Parallel yeilds ONE 12v 200AH BAttery.
Two 6v 200AH Batteries in Series yields ONE 12v 200AH Battery.

There is no difference.

The difference will be when charging. When charging two 6-Volt batteries wired in series with a 12-Volt charger, both batteries will receive the same charging current.

When charging two 12-Volt batteries wired in parallel, there is no way to know which battery is accepting charging current or how much charging current.

 

[bruceb58]

Re: Can you fry an alternator

The difference is when you have one weak cell. A weak cell will drop the series voltage but won't affect the capacity as much as one weak cell in a parallel configuration.

I do know that the Trojan T105 6 volt is one of the most used batteries for RV's house 12V battery. I might shoot Trojan an email to get their explanation for which way is better.

 

[agallant80]

Re: Can you fry an alternator

Ok so back to the original question. When I said fry I was refering to damaging the alternator weather it be melting something, over heating it or burning Diodes out. Bank 1 is just a starting battery Bank 2 is 2X group size 24 batteries. I do have a charger when I am on shore power or the generator so my primairy method of recharging would not be alternator unless I spend the night on the hook, did not fire up the generator and drove around with the switch in the ALL position. Happens a few times a season.