Alternator suggestions

[bruceb58]

Re: Alternator suggestions

Ok..one last question for the evening.

Your drawing shows breakers between the ACR and the batteries. Not sure if you put those in or not. Any chance those are opening and closing because of high current making it look like the combiner is opening?

I think I would move the alt output wire. There are a few tradeoffs on which battery I would put it on though.

 

[drewpster]

Re: Alternator suggestions

Yes, after awhile the combiner will stop cycling and stay closed. But the house battery will still draw quite a bit when I get to shore after running the engine awhile. I can tell by the shore charger. House batt draws allot, start not as much.

 

[drewpster]

Re: Alternator suggestions

I'm not sure I sized them correctly but I used two manual reset 50amp DC breakers in each of the ACR cables. ABYC requires it for safety. Not sure I really need them in cables under 10 feet in length. (ACR cables are maybe 4ft long, so 8 foot total) I read somewhere later that you don't need it under ten feet total run length, but they are there anyway.

 

[bruceb58]

Re: Alternator suggestions

Yeah, I left those out on mine but I just have the ACR wired directly to my dual battery switch.

I read somewhere ahile back that it is not uncommon for combiners to cycle if one battery is very low but I would think that would be in the thermally protected combiners. What is surprising to me though is that it is cycling the way you have it wired. Looks like the alternator is driving the house battery.

 

[drewpster]

Re: Alternator suggestions

Exactely my point, I'm not sure what going on. The only explination I have at this point is maybe the regulator is seeing a rise in voltage when the fresher start battery is combined with the weaker house battery and reducing the voltage output of the alternator causing the combiner to open.

 

[bruceb58]

Re: Alternator suggestions

Not sure if that can really happen. The float voltage of the fully charged start battery is going to be lower than the charging voltage at the house battery...at least it should be! In any case, the alternator should be putting out a high enough voltage so that the combiner stays connected.

You really need to get your meter out when all of this is happening and make some meaurements at various places.

I know you don't have one but it sure would be nice to throw a scope on your alternator output to see if your diode bridge is all intact.

Might be worth pulling the alternator and taking it to a rebuild shop to see if they can see anything wrong. I wouldn't bother with an autozone/kragen type store. they will tell you its working if its only 2/3 working.

 

[briannh1234]

Re: Alternator suggestions

It seems to me the thing is working correctly. 55 amps isn't a whole lot of amps.

Someone suggested pulling the house battery and having it checked out to make sure the battery is good. Seems worth a try and not to expensive.

Another option I've seen car stero folks do is mount 2 alternators. Keep the current 55 amp one for the starting battery. Mount a second 100 amp one for the house battery. Ends the alternator "sensing" circuit problem.

Good luck.

- Brian

 

[drewpster]

Re: Alternator suggestions

Brian thanks for the suggestions. The house battery has not been checked. In fact both batteries are on the bench right now. The boat is out of the water for the season getting a paint job. A second alternator is not my first choice because I don't think I have the room for it and I believe I can do what i want to with one. I am going to do some more testing with a DVM as was suggested by bruceb58, but I think a charging system upgrade will do wonders. The fact is the outdated alternator and regulator I have is 1960s technology. The regulator does nothing to compensate for charging a deep cycle battery. And even if the system is working as designed there is no getting around that fact.

 

[Boatist]

Re: Alternator suggestions

If it is 1960 I dout the alternator is 55 amps, more likely 35 amps or a gererator.

I really do not understand the wireing, for your starting battery to charge the engine and parallel switches must be closed. At that point the whole load is on the starting battery and alternator. House battery will charge thru your ACR but when you shut the engine off unless you change switches the entire load will be on the starting battery.

Another question: Does your alternator have a internal or external regulator?? If it external which battery is it connected to.

If you trun all three switches on then the acr is shorted out and will do nothing and your will have no battery isolation at all but both batteries will charge.

 

[Boatist]

Re: Alternator suggestions

Bruse
I like a battery isolator better because it is so simple and it works. Mine been installed since 1980 and never had a battery that did not last at least 6 years. It is just 2 diodes. There no mechanical relays, there no spark generatiors, there is no worry of blowing alternator if one battery is not making a good connection. To blow the alternator you would have to disconnect both batteries.

That big voltage drop is at most 7/10 of a volt hardly a big drop. In reallity I have tried to measure that voltage drop by measuring across the diode with a metter and also messured voltage from each side of the diode to ground without seeing any difference. I have never seen it be a problem but easy to adjust if you have a external regulator. Internal if it is a problem just get a different voltage regulator.

 

[bruceb58]

Re: Alternator suggestions

Boatist,

You should easily be able to measure the diode drop.

0.7V is a big deal when it comes to charging batteries.

I am curious, which battery do you connect your remote sense to?

In the diagram, the parallel switch is never closed unless the starting battery is low and the house battery is needed to help start the engine.

Battery isolators do work and your batteries will last a long time...they just have drawbacks as do combiners.

My father had isolators and blew out is alternator when the connection at the isolator failed. The way my combiner is wired up, the alternator is just connected down to the starter solenoid where the main battery cable attatches. If the battery is not connected, the boat won't be starting.

Bruce

 

[Boatist]

Re: Alternator suggestions

Bruse
Then your saying he charges his bank 2 house battery first then uses the combiner to charge the starting battery last. Never seen it done that way, most want the starting battery charged first then charge the house battery. I see no conection to the starting battery from the alternator output.

Most just let the starting battery charge normal then use the combiner to charge the house battery when the starting battery reaches it normal charge.

Your dad isolator must have been some cheap junk as I installed 6 isolators all had 3/8 inch bolts for the alternator connection and never seen any corrosion on any of the three terminals. Battery connections do corrode if not care for.

My Regular sinces the voltage before going to the isolator so it is off the alternator output. Both my batteries run at 13.9 volts which is right where I would like them to be. Only have to check water level once a year in the spring.

 

[bruceb58]

Re: Alternator suggestions

Once the combiner sees the threshold, it will combine batteries immediately. On my boat, the combiner is always combined when the engine is running. This is how they are supposed to work.

My preference would be for the poster of this thread to move his alternator output to the starting battery. It will work the way it is but it is not fool proof. Also, if the combiner fails to connect for some reason, the start battery is the default battery to get the charge.

With my dad's it was the terminal connection, not the isolator. My point is that it is neither the combiner or the isolater method that can guarantee that the alternator can not run open loop.

If I had your set up I would move the voltage sense line to after the isolater. You are charging your battery at 2.31V/cell or less which is in the range that causes sulfation. You will also fail to fully charge your batteries. It is probable that you don't need the full capacity of your batteries so tthe fact that they don't get fully charged is proabably never noticed. It would be interesting to take a hydrometer reading of your batteries when you believe they are fully charged.

Check out this site which describes lead acid charging voltages:

http://www.batteryuniversity.com/partone-13.htm

 

[drewpster]

Re: Alternator suggestions

In the diagram above the house battery switch and the start battery switch remain closed. During charging the ACR sees charging voltage and closes. When the ACR closes the alternator voltage is sent to both batteries. It works the same way as a isolator with less resistance.
When the engine shuts down the ACR sees resting voltage and opens, isolating the two battery circuits.
The problem I am having relates to the amount of charge the alternator supplies and the way it supplies it. The charging profile of a start battery that has had a discharge at high rate for a short period is different from the charging voltage of a deep cycle battery that has had a discharge at a low rate for a long period. Hence to charge the batteries, I need a charge that will top off two batteries with different charging profiles.
Since I do not have, and cannot afford a super dooper mega multi-output charging alternator/regulator setup, I am forced to what the rest of us have to do. Use a low RPM high output alternator that will keep the start battery charged, and at very least, give me enough deep cycle charging to keep my at anchor do-dads working long enough to get me back to the dock to do some smart charging with the VAC charger. And hope that I can keep the batteries from sulfating so I do not have to by new ones every year.
Sound reasonable?

 

[drewpster]

Re: Alternator suggestions

[Most just let the starting battery charge normal then use the combiner to charge the house battery when the starting battery reaches it normal charge.]
Does not happen that way with isolators or combiners. Both batteries get charging voltage equally. The amount of charge they get depends totally on the profile of the regulator. They get the same regardless of how they are paralelled.

[I installed 6 isolators all had 3/8 inch bolts for the alternator connection and never seen any corrosion on any of the three
Why 6 isolators? Having a problem with them burning up?

 

[drewpster]

Re: Alternator suggestions

 

[Boatist]

Re: Alternator suggestions

Why 6 isolator? I installed one on my boat in 1980. Another in my truck to charge my camp trailer battery in 1974. Another in My 57 Chev also to charge camp trailer battery about 1960. One in my Dad truck to charge his camp trailer batteries. One in my dad Boat. Last one in my friends truck for his big 5 wheel trailer. Everyone has worked perfect.

My main point in my first post and in this last post is: Even with a 200 amp alternator you can not charge a big discharged deep cycle in 15 minute trip back to the dock. It takes hours even at 14 .8 volts.

Good Luck