How do I shore charge a two battery parallel system

[melbourne]

hi everyone.

so I bought my first real boat about a month ago and it has two 12volt batteries that are wired parallel.The battery system has the 1,2,or 1+2 switch.

I understand that under power whichever battery the switch is thrown to is the battery being charged including both batteries if 1+2 "both" is selected at the switch.

How do I manually charge this dual battery system at shore??

(i believe i have the wiring for an isolator but it is not hooked up.

do i connect the charger to a single battery and throw the switch to both??

Where should the battery switch be when i am cranking the engine, running on the river, and just running house lights and electronics?????

thanks everyone.....

 

[arks]

Re: How do I shore charge a two battery parallel system

The battery system has the 1,2,or 1+2 switch.

That's a good start. Are both batteries identical? Sometimes this setup will have a deep cycle for the house and a regular one for starting.
As far as the isolator, I'm not well versed on how they work so I'll leave that for someone else. This reply is from my experience without isolators.

I understand that under power whichever battery the switch is thrown to is the battery being charged including both batteries if 1+2 "both" is selected at the switch

That is correct, but your alternator doesn't have enough juice to fully charge both batteries at the same time. Best way is to run for awhile on each.

How do I manually charge this dual battery system at shore??

Least expensive way is one at a time with a 5-10 amp charger. If it's not marine rated do NOT put it in the cockpit or bilge. A good marine charger is a worthy investment but even then, don't put the plug in the bilge. Some marine chargers are designed to charge multiple batteries at the same time.

do i connect the charger to a single battery and throw the switch to both??

No. As mentioned, it won't fully charge both batteries.

Where should the battery switch be when i am cranking the engine, running on the river, and just running house lights and electronics?????

Under normal conditions, crank with 1 battery only- not the deep cycle if you only have 1- it's for cabin lights and radio when at anchor. Run on battery 1 until it's fully charged (1-2 hours) then switch to battery 2 so it will charge.
The ONLY time you need to switch to "BOTH" is when both your batteries are low and neither will start the engine. By selecting "BOTH" you'll have all the remaining power from both batteries directed to starting.
It's saved me more than once when anchored.

 

[Bondo]

Re: How do I shore charge a two battery parallel system

Ayuh,.... Basically,... I Agree with you Arks,....
But,...

You've made a couple of Assumptions,...
Now, If Melbourne does only have a little Outboard,...
Your answers are pretty much Dead On...
If he has an I/O, or an I-B,....
He has Plenty of power available to charge Both batteries at the same time, with the switch on Both...
I do it All the time with my Barge... My Alternator puts out about 80amps...
Also,....
While there will be a Slight difference with the charge Rates,....
I charge my batteries(2 of the same batteries) while at the dock, with 1 charger(set to 10amps) hooked to 1 battery, with the switch on Both batteries...
No Problems...

 

[melbourne]

Re: How do I shore charge a two battery parallel system

Thanks for the responses. I have some answers to your questions. I need to figure out how these answers fit into my questions.

are the batteries identical??...

Battery 1: Exide Deep Cycle Nautilus Gold (NG-27)
675 MCA
550 CCA
182 RC
105 Amps per Hour

Battery 2:
Exide Dual Purpose Nautilus (NG-24)
625 MCA
500 CCA
120 RC
70 Amp Per Hour.

which battery should i crank with, run with, house power without running??

The alternator on my 150hp 4stroke yammi puts out 35amps. Will this be enough juice to charge both batteries when the engine is under power??

 

[melbourne]

Re: How do I shore charge a two battery parallel system

BTW, I have the Schumacher "Ship n Shore" 10amp Fully Automatic Battery Charger.

I believe I bought this charger close to 15 years ago from the old, old style walmart in Canton, Ga.

 

[grego]

Re: How do I shore charge a two battery parallel system

Get new charger!! if you are charging two starting batts,while "down time" you need a 2 amp-6 -10 amp charger. "set charger to two amp charge"for storage or ready for next day, set switch to both,or "two". this charges batts at a 1 amp charge per batt. if both are good. always set to both or "two to start engine" Deep cycling batts should always"trowling moter"be charged at a low amp or get a charger that does both. "recomneded". I have set up a jump cable that I can hook-up to trowilng batt while I am going place to place to charge up my trowling batt.

 

[Silvertip]

Re: How do I shore charge a two battery parallel system

Deep cycle batteries should definitely NOT be charged at a low charge rate. They need to be fully charged as quickly as possible.

 

[pvanv]

Re: How do I shore charge a two battery parallel system

The Deep Cycle battery is intended for light-to-medium loads (thicker plates), while a Start or "Dual Purpose" battery (thinner plates) is good for the high amperage loads of starting. So the Deep Cycle battery is for House and Trolling, and can tolerate deeper discharges while a Start/Dual tolerates start amps better. Small outboards don't draw a ton of amps when starting, so you can use a Deep Cycle for small OB's.

Charging is a separate issue. A "real" marine charger is a wise investment. The cheap automotive or older ferro-resonant types often leak AC into the DC side, promoting corrosion of any metal that is in the water. Also, most modern Marine chargers are the 3-stage type, that have the better charging profiles. They charge faster, and top the batteries up more completely.

You will also want to match the charger to the battery chemistry. Flooded and Gel batteries can generally use the same charging profiles, but an AGM requires a charging system that has the correct profile, or it will have a dramatically shortened life. Some of the better marine chargers have a switch to set the chemistry type.

In any event, you can charge two batteries in parallel from a single charge source by setting the battery switch to "2" or "Both". They should be the same chemistry, and ideally, similar group size and age for best results.

 

[Fl_Richard]

Re: How do I shore charge a two battery parallel system

What happens when you throw twins into the mix?

 

[arks]

Re: How do I shore charge a two battery parallel system

What happens when you throw twins into the mix?

Well, my 2-engine Silverton has 2 starting batteries. Each is wired to their own "1-2-BOTH" switch, which gives me the ability to use either or both batteries to start either engine. It's a nice setup.
For me, it gets complicated with my house batteries. I have 2 more (in addition to the starting batteries). One is for 12 volt lighting and accessories, and the other is dedicated to my generator. I'm in the process of tieing them together like the starting batteries (with 2 separate switches) so I can have the same flexibility. I'm also adding another 2-bank marine smart charger.

 

[waterinthefuel]

Re: How do I shore charge a two battery parallel system

Deep cycle batteries should definitely NOT be charged at a low charge rate. They need to be fully charged as quickly as possible.

That is not true. All batteries should be charged at the lowest rate possible, ESPECIALLY DEEP CYCLE BATTERIES. Slow steady charging helps to extend battery life. A fast charge can damage the battery and/or reduce it's life. That was told to me by an electrical engineer.

Size the charger so it will recharge the battery in an 8-10 hour period.

Recharging slowly and keeping your battery well maintained are the best ways to extend the life of your battery.

http://answers.yahoo.com/question/index?qid=20080427192154AAuKZle

SUPER FREAKIN' WEBSITES ABOUT BATTERIES HOLY COW!

http://marine-electronics.net/techarticle/battery_faq/b_faq.htm#6

http://www.windsun.com/Batteries/Battery_FAQ.htm#Battery Charging

The best method is to slowly recharge the battery at 70? F (21.1? C) over a 10 to 20 hour period (C/10 to C/20) using an external constant voltage (or tapered current charger) because the acid has more time to penetrate the plates and there is less mechanical stress on the plates.

Silvertip I highly recommend that you read those websites. Your views on battery charging are way off.

You certainly do not need a specific deep cycle charger. A charger is a charger, a deep cycle charger does nothing special but empty your wallet at the checkout counter. A regular, automotive smart charger is best.

 

[pvanv]

Re: How do I shore charge a two battery parallel system

Silvertip is correct.

A cheap automotive charger has no place on a boat. Period. It could be used, temporarily, on a trailered boat, on shore, in a situation where no other charge source is available, but that is all.

The reasons to avoid cheap car chargers are these:
1- They are not designed for a saltwater splash environment, so they suffer a short life on a boat.
2- They are not capable of providing the correct charge profiles needed for the different battery chemistries (AGM vs flooded, etc).
3- They usually have simple bridge rectifiers, with minimal filtering, and leak tons of AC ripple to the DC side, causing tremendous corrosion to any grounded/bonded metal that is in the water. I have personally seen a lower unit chewed up by use of a cheap charger, and it is not uncommon. In a worst-case scenario, this can actually make the water near the boat "hot" so that swimmers are zapped when near the boat.
4- They are bulk-only chargers, and will provide neither a rapid nor full charge, and can cook a battery and cause excessive gassing if left on too long, since they are usually unregulated.
5- They are a violation of ABYC and other standards. A good marine surveyor should condemn any vessel that is so equipped.

The only charger that should ever be on a boat is a marine-rated, 3-stage charger. Period.

The reasons for a good marine-grade 3-stage charger:
1- They are designed for the damp marine environment, and have a commensurate lifespan.
2- They are available (some are switch-selectable) for different chemistries (AGM, Gel, Flooded), which have different charge profiles.
3- They provide very pure DC with minimal AC leakage ripple, so are much safer for underwater metals and nearby swimmers.
4- They provide 3 stages of charge (Bulk, Absorption, and Float) for long and reliable battery life. Flooded batteries live the longest and best if they are never left "hungry" for a charge. They should be charged as soon as possible after discharge. A good 3-stage charger provides the correct charge profile, with rapid bulk charge first, before going into the Absorption and then Float parts of the charge profile.
5- They are approved by ABYC and other standards, so your boat won't fail a survey -- and have the insurance cancelled.

In addition, many modern marine chargers are designed for multiple battery banks. Some have independent (floating) grounds, and can charge batteries that are configured in series and/or parallel, as is often the case for boats that have start, house, and trolling banks.

 

[melbourne]

Re: How do I shore charge a two battery parallel system

A big Melbourne, Florida BO-YAAAA thank you to everyone that responded. "All" of the information, that everyone provided has been us very useful.

Thanks again everyone!!!!

 

[Fl_Richard]

Re: How do I shore charge a two battery parallel system

I have twin 150's and two batteries. The batteries are connected to the 1-2 both switch. I also have a On/Off switch connected to the port engine.

1-2 and both positions will start either engine. On/Off seems only for port. What happens if I run both engines with the switch in the both position. I've heard because of battery chemistry even with identical batteries one will fully charge and the other will not.

I often run in the both position as both battteries are usually discharged from sitting and my trips usually average a few hours of running. I feel this will charge both batteries close enough.... Am I damaging something?

 

[Silvertip]

Re: How do I shore charge a two battery parallel system

Waterinfuel -- I did read the links you posted and my original comment agrees with them and your links contradict what you indicated. The lowest possible charge rate in your view is apparently 1-2 amps. On-board chargers are typically anywhere from 5 - 20 amps per output and those chargers are very well regulated and charge profiles carefully engineered. The 20% of AH capacity charge rate is correct as the article states and the single and multiple bank on-board chargers do not exceed that rating. So using the articles technique, a 70 AH battery can be safely charged at a 14A rate (20%). So where am I so wrong?? I said charge the batteries the quickly as possible after being deeply discharged. That doesn't mean charging at higher than a safe charge level. It means don't leave the battery in a discharged state for a long period.

 

[pvanv]

Re: How do I shore charge a two battery parallel system

Waterinfuel, I agree 100% with Silvertip, and would add emphasis on never ever using a land-designed charger in a marine environment, for all the reasons I posted above.

Richard, your switch setup seems a tad unconventional, with a disconnect for the port motor (only). A previous owner may have done that for a particular reason. A little more investigation of the wiring may reveal a clue. I would be careful about that port motor disconnect, because if the port motor is running and you turn off that disconnect, you risk cooking the diodes in that motor's alternator circuit.

Still, charging in parallel is OK. Your 150's likely have decent alternators -- each with enough output to charge both batteries. As long as the batteries are matched -- same chemistry, similar size and age, and preferably same make, your charging should be pretty decent. There is no true panacea: Each battery, even off the same assembly line the same day, will have some slight variations. Usually not significant.

Typically, it's advisable to throw the switch to a setting other than "both" after the batteries are charged; The reason being that you keep a fully charged battery at the ready, should you happen to discharge the other one. Some people take that a step further, and charge one battery at a time. The "both" setting is often considered the "emergency start" position, used when neither battery (alone) can deliver enough power for cranking.

 

[Fl_Richard]

Re: How do I shore charge a two battery parallel system

Excellent news!!

Thank you Paul

 

[waterinthefuel]

Re: How do I shore charge a two battery parallel system

The OP never said he wanted to leave the charger in the environment. He simply asked how he could shore charge 2 batteries in parallel.

You could use an automotive style smart charger on a boat, absolutely. But you better do your damndest to make sure it doesn't get wet. If it's a salt water environment, just leave the auto charger in the garage.

If it was to be left on the dock or in the boat, if it's fresh water, it's fine. Salt, no way. We have 3 chargers that are digital automotive smart chargers used on a freshwater lake. They don't get wet, but they stay at the dock for weeks at a time and all work fine. Ideally though, I don't recommend anything but a sealed marine charger if it is to stay in a marine environment. However, as my dad discovered, that doesn't mean anything. His houseboat came with a built-in on board marine battery charger. It didn't last but a year or two in the enclosed cabin of the houseboat before it went to crap. He got a couple of decent digital smart chargers for all 12v batteries and has been using them for years. They're no more sealed than the man on the moon but they still work. And they aren't in an ideal environment.

 

[pvanv]

Re: How do I shore charge a two battery parallel system

Agreed that a land charger will work OK on land, but I still put emphasis on the true marine charger, unless the supposed "digital" charger is a true 3-stage.

DC is not a digital environment (except for ON and OFF), so that label may just be advertising hype.

 

[Wee Hooker]

Re: How do I shore charge a two battery parallel system

FWIW, if you have a trolling motor, I've found it's convienient to replace the clips on a charger with a trolling motor plug. This allows you to plug right into the boats TM receptical and charge your system that way vs digging around in the bildge. Works for me anyway.