Battery charging

[TBroccoli]

If you have your battery switch in position one, is the altinator charging both batteries?

[TBroccoli]

I guess it makes sense to run on both. Thanks poodle.

[Morgan's Cloud]

I guess it makes sense to run on both.

Not too long ago there was a discussion on this on that 'other board'.

It got kind of confusing determining what the eventuall outcome was.

My mechanic says to never run on 'both' or 'all' position .

What are the facts on this topic :confused:

S

[TBroccoli]

I figured to run on both so both would always be charging. I would think to switch to 1 or 2 when sitting at the beach with the radio blasting. Someone explain proper use and why..

[jeffnstef]

It seems to me that if you keep it in both you will be charging both all the time unless you happen to be disscharging for some unforseen reason and then you will be left with two dead batterys !

I would think that you should alternate between batterys to keep both fresh and then when you have killed one while you are passed out with the radio blasting you can switch to the fresh one when you come too.

[TBroccoli]

So, back to the original question. I'm gonna go with MP unless someone else wants to join in. The only battery being charged is the one the dial is pointing to. 1 , 2 or both. Thanks, Tom

[gcarter]

A number of companies make battery "isolators" which allow both batteries to charge simultaniously. These devices contain large diodes (a one-way device) in the alternator output lines to the batteries. The only draw back, if there is one, is it drops the alternator voltages by one volt.
:wavey:

[Ranman]

I am not an expert on this and there has been some good discussion on this board concerning dual battery setups (unfortunatly, if forgotton most of it), but here's what I vaugly remember the issue to be.

The problem wiuth running on "both" or "all" is that batteries are not all the same (even identical make and model). By leaving the switch in the all position, the stronger battery will be giving up its charge to the weaker one. This continual flow from one to that other somewhow puts a strain on both. The accepted method I've heard is to run battery 1 on odd days (8/23/2004) and battery 2 on even days (8/24/2004). Maybe someone can link us to the old thread.

[gcarter]

Randy, this is one of the really strong points of isolators. Your only using the selected battery, but both batteries (or banks of batteries) get charged together.
You almost never see a twin cruiser or FBSF without one or two. They're quite small and cost between $50.00 and $100.00. :smash:

[Ranman]

George,

I understood isolators to have that exact advantage. This is a subject I plan to research somewhat this winter. Would you provide an example of a quality isolator for reference? In the mean time, I'll use the even/odd method. Thanks.

[tmdog]

I never try to charge 2 batt. at same time I go along with Ranman. Only time I swit5h to both is if I anticipate a starting problem and that is to prvide an extra jolt.

[gcarter]

OK, all;
Here's a couple, but first my personal experience is with Guest isolators. I had very good results with them. Basically a wire (12 GA or so) is added to the alternator output in addition to the existing one. This wire is terminated at the input post of the isolator. The two output posts have wires going to the positive posts of the two batteries, bypassing the battery switch, thereby allowing both batteries to be charged simultaneously. The battery switch still functions as normal. Only the battery or batteries selected can be used. You probably wouldn't find a larger twin engine boat w/ multiple batteries w/o them.
BTW, I know charles makes fine products, but I've had terrible experience with their built in automatic battery chargers.

http://www.marinco2.com/showProduct.asp?p=2401A

http://www.charlesindustries.com/main/ma_batiso.html

IMO, no one with two batteries should be without an isolator. There will always be a time when you forget to sharge one of your batteries. :lightning :lightning

[MOP]

If you don't have an isolator the old rule of thumb is to run the #1 batt on odd days and run the #2 batt on even days, that has worked for many years.

Phil

[Morgan's Cloud]

Well,
To satisfy my curiosity I went and checked with my mechanic this morning (Merc and OMC certified , all engines).
He claims that some of the older engines did'nt like it and there was occasional problems. The new engines don't mind and there is no problem running the engine in 'both' position.
(Battery isolaters or different batteries have no affect)

He did finish by admitting that he is old school (like me) and always only runs on one battery at a time .... :biggrin:

ps , we were referring to inboards/sterndrives in our talk .. don't know how outboards factor in .

S

[Garyw1]

Don't want to stir this up , but, if you run in the BOTH position the alternator will "READ" the highest charged battery and stop charging, (reduce output voltage and amperage). Then the weaker of the two will, 1 never recieve a full charge, 2 draw the stronger battery down to its level. As stated in one of the earlier posts on this thread, an isolator, (or 2 engines) is the way to go. Tom if you want, contact me directly and I'll let you see how I set mine up.
The reason for the problems on some of the older engines was a 1 wire alternator (no senseing wire) that wouldn't charge properly because the isolator wouldn't let current pass back to the battery terminal on the alt.

[MOP]

S Quote!

He claims that some of the older engines did'nt like it and there was occasional problems. The new engines don't mind and there is no problem running the engine in 'both' position.
(Battery isolaters or different batteries have no affect)

It has noting to do with old or new engines, like stated earlier it is the fact that no two batteries are alike. While one is seeking charge the other is being over charged shortening its life span. Never run on both just use it for extra start power, let it run a few minutes so engine will restart easily then shut down and go to just one battery for restart don't switch while running you can damage the alternator.

Phil

[Morgan's Cloud]

Phil ,
He said something about a situation where one battery had a lower charge than the other but I can't remember exactly what it was , except that it would'nt harm the alternator ..

Nonetheless, I will continue to only use one battery at a time and NOT touch the battery switch while the engine is running :boat:

[Ranman]

don't switch while running you can damage the alternator.

Phil,

Can you quantify this statement?

[gcarter]

Hmmmm.......wouldn't switching through the "OFF" position be the same as disconnecting a battery while your car is running? I think we've all done that at one time or another, like when you might change a battery while your car is running.

[David O]

Good article on Creating a Reliable Battery System

http://www.westmarine.com/webapp/wcs/stores/servlet/WestAdvisorDisplayView?storeId=10001&langId=-1&catalogId=10001&advisor=creatingabatterysystem.htm

[TBroccoli]

Guys,
thanks for all the input. Good article David O. I may purchase an isolator in the near future. For now, I will use MOP's theory.

Thanks again, Tom

[MOP]

Phil,

Can you quantify this statement?

If the circuit is broken it can and does blow the diodes in the diode bridge, it has been known to blow ignition packs. The sudden Off-On may damage EFI computers also, with cheap switches you are jolting sensitive electrical items. Most switches are marked if they can not be switched with engine running, good quality switches have a larger wiper that will contact the next terminal lug before leaving the other preventing lose of contact. Read the box when buying, just don't buy the cheaper switches that tell you not to switch while running.

Phil

[Ranman]

Most switches are marked if they can not be switched with engine running, good quality switches have a larger wiper that will contact the next terminal lug before leaving the other preventing lose of contact. Read the box when buying, just don't buy the cheaper switches that tell you not to switch while running.

Good information. Is it safe to assume that your every day big red Perko switch is indeed a good quality switch?

[MOP]

Randy it is easy enough to check, take a volt meter hook to any positive feed after the switch then try the switch. If the needle stays constant no dip while switching it should be just fine. I have a cheap Perko that will need shut down once I install dual batts, right now its just a shut off I don't like leaving the juice on when not in use.

Phil