Automatically switching charge of 2 batteries while on the water

[macds]

I've been doing some reading, and cant seem to find what Im looking for. So here's what i'd like to do.
One battery for starting the engine, running lights, guages, horn (21' Starcraft fishing boat, so this is no problem for one battery). One battery to run an inverter. NOW... I dont want to have a manual switch involved in this. What I want is that once the starting battery reaches a set voltage, say 13v, THEN my charging system begins to top up the second battery. IF the starting battery drops to say 11.5 volts, then the charging system automatically cuts the 2nd battery, and begins charging the starting battery again. Is there anything out there that does this? Can i build it myself using Diodes between the two batteries. Basically what im building is an if/or switch for 12vdc. Ideas?

Thanks

Stu

 

[Boatist]

Re: Automatically switching charge of 2 batteries while on the water

I think below is what you are looking for.
If it is a small outboard motor then I would not use it to charge a second battery.
If your motor has 20 to 30 amps output this should work.

What do you need AC for from an inverter?

You can build a battery isolator using Diodes but if you want voltage sensing then eaiser to just buy one of these.

See link below.

http://www.iboats.com/Boat-Parts-Ac..._category.f--searched.1--**********.361947248

 

[macds]

Re: Automatically switching charge of 2 batteries while on the water

That seems like what im looking for, except for the "When the engine stops and the voltage on the sensed battery drops to 12.8V the relay opens and isolates the two banks" part. I dont want to have to shut engine down for it to switch back to charging the main battery. Otherwise I think its what I need.
The engine is a 165 mercruiser with 60A alternator, so thats not an issue. I want to run the inverter to run a small ac fridge and MAYBE microwave. (So it will be a 3 battery system, 1 starting battery isolated, and 2 deep cycles wired in parallel for the inverter... so approx 12vdc, 1400mca, 210Ah on inverter). Any other ideas?
Also came across this... http://www.yandina.com/acrobats/C70Manual.pdf
seems to make sense to me?

Stu

 

[Monte1961]

Re: Automatically switching charge of 2 batteries while on the water

small generator comes to mind.

 

[macds]

Re: Automatically switching charge of 2 batteries while on the water

I dont really want to run a genny, that takes more space, and is one more mechanical thing to maintain on board.

 

[Tailguner]

Re: Automatically switching charge of 2 batteries while on the water

I had the same question and talked to a blue sea engineer. In short nothing on the market right now that will do what you want unless you installed invertor/charger systems that the big boats have according to them. The best i can tell you is to install a battery isolator before the battery selector switch so that all batteries are being charged no matter which battery is selected. Thats what i did and no problems so far.

 

[Boatist]

Re: Automatically switching charge of 2 batteries while on the water

The way it works is Your alternator charges the starting battery all the time.
When the voltage climes above 13.7 volt on the starting battery it switches in the next battery on in your case your bank of 2 deep cycles battery.
It continues to charge the starting battery. When You shut down the engine your starting battery will drop below 12.8 very fast and the switch will open so your deep cycle bank can not run down the starting battery.

 

[macds]

Re: Automatically switching charge of 2 batteries while on the water

I see, so the deep cycle banks CAN only be wired to the inverter, and when the starting battery is totally charged, then it ill charge the deep cycle bank, and still keep the deep cycle bank isolated from the starting battery?
What if i just wired diodes between the inverter bank and the starting bank, so that the alternator would charge all 3 batteries when running, then when not charging, the starting battery could not back feed into the inverter circuit? That way, batteries are charged together, but only the inverter batteries could be run down no matter what. No switches or anything, and cheap. Check out

http://www.princessauto.com/trailer...truck-electrical/8235673-90a-battery-isolator

 

[Tailguner]

Re: Automatically switching charge of 2 batteries while on the water

Battery isolators like the one in your link do not "switch" over charging from one battery to the other both batteries would be charging at the same time while engine is running regardless of state of charge of either battery

a 3 battery bank isolator would work good for you and your situation. the isolator would charge all 3 batteries (banks) at the same time while engine is running and also isolate them from one another to prevent any of the batteries to drain down another when engine is off

the battery isolator is the only way to charge all the batteries regardless of switch position that i know of. I went one step further in that I purchased a 3 battery marine isolator for my system. Here is how i have it hooked up:

from the alternator to the battery isolator
sense wire from alt to batt 1
batt 1 on isolator to batt 1 on perko switch [starting battery]
batt 2 on isolator to batt 2 on perko switch [back up starter battery]
batt 3 from isolator to my (2) 6 volt batteries that only powers the stereo and amps [stereo only batteries]

the 6 volt batteries are not connected to the perko switch as i have a simple battery cut off switch to disconnect power to the stereo when not in use at the 6 volt batts so that stereo clock and memory dont drain the batteries when not in use

so in effect all battery banks are being charged regardless of the perko switch position while the engine is running. This allows me to have a back up starting battery as well as a battery bank for the stereo. Now the boats alternator will not fully charge the 6 volts after a long day of stereo play but then i just plug a standard battery charge to them when at home.
the benefit of the system is any battery that gets low can not draw down any other battery. The alternator output is not high enough to cause any overcharging of the batteries either.

 

[Boatist]

Re: Automatically switching charge of 2 batteries while on the water

The link I supplied for the VSR will charge your starting battery and your 2 battery bank at the same time.

When You start your motor Your starting battery will reach 13.7 volts in less than 5 seconds at which time the VSR will connect the other battery bank. So after 5 seconds all three batteries are charging. When you shut your engine back off if your second bank of batteries is not fully charged then the VSR will drop in a few seconds and banks are isolated again.

Now if you want to use a battery isolator that will work also but how well it works depends on if you have a 1 wire alternator or a 3 wire alternator.

If you have a 1 wire alternator then the alternator will set it's output to what the voltage regulator is set to.
If the voltage regulator is set for 14 volts then going into the isolator will be 14 volts. The 2 battery outputs would be 13.3 volts.
Now this will still charge your batteries but slower. Usually batteries charge at 13.8 volts to 14.8 volts so they would charge faster.

If your alternator is a 3 wire alternator and it is wired so the field winding comes off the starting battery then it would work better.
Since the regular is working off the starting battery and if it the same as before then going into the isolator will be 14.7 volts and the isolator will drop .7 volts so the batteries are charging at 14.0 volts.

Alternators with internal Voltage regular can have many different regulators. I would say most are between 13.8 volts to 14.8 volts.
Some new type regulators the output voltage changes based on temperature. When the alternator is cold it may put out 15.0 volts then as it warms up may drop to 14 volts. On hot days this helps the alternator to run cooler and also less likely to boil the batteries.

With 1 wire alternators the VSR works better.

With 3 wire alternators wired up right then I like Battery isolators better. This is what I use on my boat.

This is a long post but a little more information.

Battery isolators usually have a diode for each output. Usually rated 70 Amps ot 130 amps. To foward bias the diode takes about .7 volts. So with 14.0 volts in you get 13.3 volts out.

With a 1 wire alternator the voltage is regulated at the output of the alternator so 14.0 volts out the battery gets 13.3 volt. If it is 14.8 volts regulator then battery gets 14.1 volts.

3 wire Alternator regulators have a sense wire that feed back to the voltage reglator. This will usually come from the battery through the ingition switch so on these 3 wire alternators. So with the 14.0 volt regulator it puts out 14.0 volts then goes through the battery isolator and is dropped to 13.3 Volts but this is feed back to the voltage regulator and it increases the current through the field winding until alternator puts out 14.7 volts then through the isolator is 14.0 volts.

 

[barbosam]

Re: Automatically switching charge of 2 batteries while on the water

Check out the BEP battery switch clusters. I use the 716H-100AVSR. I have seen the BEP clusters installed on a lot of boats, big and small, with a lot of success. It does exactly what your looking for.

http://www.bepmarine.com/home-mainmenu-8/productcategory-205/clusters-manual

Boatist already provided a link to the iboats store for these items but i figured I'd throw in a link to the BEP site because they have many more available than what is listed on the iboats store.

 

[macds]

Re: Automatically switching charge of 2 batteries while on the water

I have a 1 wire setup, using the standard mercruiser alternator that come on a '74 165 (60A).
Im wondering if I could use a newer gm 3 wire 120 amp alternator and wire it in?

 

[Boatist]

Re: Automatically switching charge of 2 batteries while on the water

Yes you can use the GM 3 wire 120 Amp alternator but it has to be wired correctly. With 120 amps you will have to change all your output wires to handle 120 amps. The isolator will need to be at least 150 amps. Also you will need to find out if it has an internal voltage regulator or an external regular. Older ones are usually 65 amps or less and a external regulator.
Newer ones common at 100 amps with internal regulators but still need to be wired correctly. Another problem when changing a alternator it can mount much different and the belt may not line up. Also when you double the current output you double strain on the drive belt so it will have to be a lot tighter to prevent it from slipping. When you tighten the belt way up it puts more strain on the alternator bearing and your water pump bearings and crank shaft bearings. The higher output alternator may need a wider V belt or it could need a much wider mullti grove belts.

It would be much cheaper for you to call around to the alternator rebuild shops and get a higher voltage regulator to compansate for the Battery isolator voltage drop. Kragens or Auto Zone are just going to laugh at you but any good alternator rebuild shop should be able to help you.

I have changed both my external Voltage regulator on my boat and a Diode Triode inside my trucks alternator but I got both parts from a bebuild electral shop. Both parts were less than $20.
To do in your self you need to know hpw to pin the brushes up.
Also any time you go inside good idea to check front an back bearings. If good just relube. It not then repace.
When putting back together make sure all the screens are in place.
Of course the shops will do it all for you for a charge.

Before going to all this trouble check and see what your voltage output is with a good metter. Measure at the battery with the engine at 1000 RPMS and water cooling.

If I was you I would just use the VSR. Your starting battery would normally be recharge from starting in 5 minutes so that would give you 30 amps each for your 2 battery bank. Even with a 120 amp alternator batteries will likely not recharge any faster as the voltage regulator will regulate the output voltage to the same voltage. The batteries after a few minutes would likely take less than 20 amps each unless they are very large batteries If you have a Big Inverter using a lot of the current from the alternator then it may make a big difference.

 

[smoothoperaider]

Re: Automatically switching charge of 2 batteries while on the water

Here is a link to a "smart" switch system with VSR that my be exactly what you are looking for. I used this switch system and all of my wiring harness, switch panel and most other electrical came from this site for my complete rebuild. All has been relatively user friendly during installation and seems well made. I have not run it enough yet to give you a good review on performance.

http://www.ezacdc.com/Scripts/prodView.asp?idproduct=291