Alternator suggestions

[drewpster]

I need to improve from my current ancient alternator setup to new one that will actually keep up with my battery usage. I want to keep a single wet cell start battery and a single wet cell deep cycle house battery topped off. I don't have the room to add a generator so it will have to be stout alternator that can give a good charge from the main engine. I don't have a ton of money so I need to match a decent alternator to the system. Any Suggestions?

 

[ricksrster]

Re: Alternator suggestions

What make, model, and year is the motor?

 

[Silvertip]

Re: Alternator suggestions

Simplest = Small Honda genset.

 

[drewpster]

Re: Alternator suggestions

Chrysler m273 inboard v 8 is the engine. When you say small Honda genset are you talking about a small portable generator like you use on a jobsite? Or does Honda make a marine permanent install version?

 

[bruceb58]

Re: Alternator suggestions

My questions would be:

1) What size alternator do you have on their now.
2) What kind of loads do you currentlyhave on your batery?
3) What size is your deep discharge battery?

 

[Boatist]

Re: Alternator suggestions

You can buy an alternator that will put out 100 to 130 amps but it will not solve your problem. Yes it will keep the starting battery charged no problem but the deep cycle trolling motor battery a different story.

You alternator will have a regulator that will limit the voltage out to something below 14.8 volts and some as low as 13.8 volts. The problem is even at that voltage a discharged Group 27 or larger battery will take at least 12 hours to charge. It might start out charging at 30 amps but within about 10 minutes it will drop back to 10 to 15 amps and continue to drop as it charges. It just the way batteries are.

My factory Alternator is about 45 amps and it charges both the starting battery and Deep Cycle in a few minutes even after all day fishing but I do not have a trolling motor to discharge the deep cycle. Just a lot of normal marine electronics.

 

[Silvertip]

Re: Alternator suggestions

Yes -- Honda makes all sorts of small portable generators. But since you said you don't have room for one, I would suggest carrying one of the larger "Jump Start" units to provide an emergency source of power. A larger alternator would certainly help. Lastly, if you are running out of "house power" you might want to have the battery tested. A dying battery will not hold a charge so you may not actually have a problem. Or you may need a large house battery. Lots of things to consider before making major and expensive electrical changes to solve a non-problem.

 

[drewpster]

Re: Alternator suggestions

The current setup has a single prestolite alt w/old contact type regulator and a charging relay. I think but I am not sure that the Prestolite is 55 amp. This was the factory setup with a single start battery.
I have added, a deep cycle I think is a 220amphr with a pathmaker combiner and isolated all of the house loads through a separate panel. I have added lighting, stereo, and several other do-dads along the way. I like the lake at night so I use the battery allot. I have also been known to run a small fan, deck lights, fishing lights, and other assorted neat stuff. So I need good house power.
I have never had trouble starting the boat or running out of house power over a typical two day weekend, but have noticed when I get back to the slip that the deep cycle is pretty low on juice while the start would be fine.

I have also noticed the combiner struggling to stay closed while underway. I believe this is due to the system voltage dropping below the opening setting of the combiner when the house battery gets paralleled with the start battery. After awhile, up to an hour, of running time the combiner will remain closed. I think this is due to the house voltage coming up high enough that overall paralleled voltage is above the disconnect setting of the combiner. The house battery is the primary and is connected to the alternator directly. I have tried the system with the start battery connected in this way with only a slightly different result.
My conclusion is that when the batterys are paralleled during charging, overall voltage drops with the load of the two batterys. The alternator does not have the juice to quickly bring overall voltage up to keep the combiner closed and stable. Confused now? I am.
Any way you look at it the batterys are not getting topped off. I know it is difficult to bring the deep cycle up quickly, but I would like to be more confident the system is getting enough voltage while underway. I bet the lower voltage is putting a strain on things. And I have no confidence in this regulator and old alternator setup.
I would like to hear any suggestions aside from an onboard genset due to lack of room. I have considered a small carry on generator, but I'd rather do without the noise of one. I am more the quiet serene type.

 

[Reel Poor]

Re: Alternator suggestions

Have you checked the output capacity (voltage and amperage) of your charging system. It would be ashamed to replace the alternator and find out there's a problem somewhere else. :^

Your statement about the combiner not staying energized is one reason I prefer running an isolator.

 

[bruceb58]

Re: Alternator suggestions

Have you measured voltages at various places while the engine is at higher RPM? Measure the voltages at the alternator output and both batteries. When you make these measurements use the same ground point for alll of them. I suggest measure from the engine block.

Usually combiners "combine" when either voltage is over a threshold. I would think that the voltage being put out by the altenator would at least get you above this threshold but it is possible there are drops between the alternator and the battery or the alternator itself is not developing full output.

Another possibility is that there is so much current flowing through the combiner that it is hitting a thermal cutout. Some combiners have these and others don't. Many rely on a certain length of wire between the batteries and the combiner to provide enough voltage drop to prevent too much current from flowing through the combiner.

I think you would really benefit from a new alternator no matter what you find here. Since you are using a combiner, you can use a one wire alternator since you don't need remote sensing.

 

[bruceb58]

Re: Alternator suggestions

Your statement about the combiner not staying energized is one reason I prefer running an isolator.

I actually prefer a combiner for the main reason that once the start battery becomes charged, the alternator's output is so reduced that it won't charge the deep cycle at a rate it actually needs. That is, of course, assuming the sense from the alternator is seeing the start battery and not the deep cycle.

 

[bruceb58]

Re: Alternator suggestions

I went on to the Xantrex site which makes the Pathfinder combiner. Do you have the version that has the adjustable voltage connect and disconnect? If so, what do you have them set to?

That combiner also uses a relay so you won't have the thermal disconnect that I mentioned in the previous post.

By the away, that is a nice combiner...did not know that they were available. A little pricey though!

 

[drewpster]

Re: Alternator suggestions

I am using the Xantrex Pathmaker 100amp 2 bank combiner. Yes they are pricey, that's why I have the smaller version. I have a manual override to parallel the batts for emergency starting if needs be and I do not think the charging amps will exceed 100, so I bought this one to use strictly for charging and isolating. I did not want to use an isolator because I knew the alt would be working overtime and I couldn't afford the volt drop across the isolator.

I can control low voltage "disconnect" setting, the charging "connect" setting and the high volt disconnect.

I have not checked the values as well as perhaps I should. So it has been trial and error so far in settings. Resting voltage just after engine shut down is about 13v according to my panel gauge so I set the combiner to open at about that voltage. I think the lowest it will go is around 12.8v. The low end seems to work fine there because I can hear the solenoid open a couple of minutes after shut down. The connect voltage ranges from 13.1 to 13.5 v. I set the dial in the middle.

Just after start up I can watch my panel gauge slowly rise to just over 13 v and I will hear the solenoid close. (slowly rise) Upon closing the gauge will fall. Not sharply, but it does fall. The the solenoid will open. (here is where I think the alternator is loosing its cookies) After e few seconds the voltage will climb slightly and the solenoid will close again. The on-off-on cycle repeats until at some point the voltage will stabilize and the voltage remains constant enough to keep the combiner solenoid closed.

I have to come to the conclusion the alt, the regulator, or both are not up to the job. Maybe?

I have a DC amp probe. (mag field type) Before I did all the mods I checked the alt amp output. The meter never got above 8 amps or so when charging after startup. I was just learing to use the amp probe and the battery was fresh so assumed everything was ok. I haven't checked it since I added all the stuff.

You think I should go with a one wire alt? Or go all out nuts and get one of those high output externally regulated jobs? (hmm... $200 vs. $500-$700 bucks) At night I just wanna listen to the radio, see the hooks I drop on the deck, keep other idiots on the lake from running over me, let the fan blow me to sleep, and still start engine in the morning. Too much to ask?

 

[bruceb58]

Re: Alternator suggestions

Use your voltmeter and do a few voltage drop measurements between everything to make sure all connections are ok.

I am going to change my mind on something I said before...I would sure make sure all your wiring was good before I plunked down a bunch of money on a new alternator.

Under what conditions were you measuring 8 amps? Both batteries combined and discharged?

When you are describing the voltage rising, the combiner clicking in and then the voltage dropping, what idle speed are we talking about here?

Also, don't put too much trust in your panel meter. Use a DVM.

 

[Boatist]

Re: Alternator suggestions

I prefer a battery isolator but since you already have the combiner may be you can make some changes to make it work better.

First Clean and check all your connections on the main battery.

Second make sure the belt is in the top part of the pulley and tight. If the belt get to the bottom of the pulley even if it is tight it will slip and may not make any noise. When putting full load on the alternator the belt has to be in great shape for it to work with out slipping.

Third make sure all the connections up to your combiner it self are clean and a large guage. If the pick line is small go up one guage.

Last check the output line of the combiner. If it is more than 10 guage then try 10 guage or a longer length this will reduce the current to the deep cycle battery some and maybe keep the combiner picked. If you down size then when the battery is very low fire it up and check the temperature of the wire with your finger. It should not get too hot to hold your finger on.

55 amps should be enough to charge both batteries if the belt is not slipping and the brushes are good and the alternator is in good shape. Things like a bad Diode triode inside the alternator will cause low output or a open diode in the rectifier block.

If you go to a larger alternator remember you will have more load on the alternator so will need a bigger tighter belt.

 

[bruceb58]

Re: Alternator suggestions

Good rule of thumb is an alternator 25% of your capacity or larger. The reason for this is that regular lead acid batteries can't really absorb more than 30% of their capacity in charge current unless you really boost the voltage.

Boatist...why would you think an isolator would be better? Becuase of the voltage drop across the isolator (even with remote sensing) the alternator is forced to operate at this much higher voltage in order to charge the sensed battery. Depending on which battery you end up sensing, you are either going to have an undercharged battery or an overcharged one.

 

[drewpster]

Re: Alternator suggestions

Here is my diagram. All cabling is new. I attached the ends and heatshrunk. All runs are short, under 6 feet. ACR is combiner. Battery cables are 1/0, Alt feed and ACR cables are 6ga. Regulator wiring is 10ga. All wiring is Marine grade tinned. Heatshrink is automotive grade fuselink.

The combiner cycles on-off-on regardless of engine speed. Regulator problems maybe?

 

[bruceb58]

Re: Alternator suggestions

Nice diagram.

I am concerned about the output connection of your alternator. If you have the engine switch closed, the house bank switch open and the parallel switch open, it looks like the alternator will not have a load on it.

I would have that tied directly to one of the batteries. If you ever ran this configuration with the house battery switch open, you may have fried some diodes.

 

[bruceb58]

Re: Alternator suggestions

What is that zap stop? Fancy name for a zener diode?

Does the combiner stop cycling once the batter gets charged up.

Looking more and more like your alternator. Sounds like you did a good job on your cabling.

 

[drewpster]

Re: Alternator suggestions

You are correct about the no load with switches open problem. The Zap stop on the alternator is a safety against that. I do not switch the batteries unless the engine is off. And only when I am at the dock and running the onboard charger. (i added a shore power system as well)

I struggled with where to connect the alt. This diagram is not mine, it's West Marine's so went with where they show it. It could easily be moved to bank 2 (house) positive.