Dual Battery Switch

[hollandcrew]

When you have a battery switch hooked up is it OK to change from 1 battery to the other with the engine running? Also what if the battery you are switching to is almost dead will this put to much of a bind on the charging system?
I have a 2004 90hp Yamaha.

Thanks for any input!
Al

[THOMAS70]

Most owners manuels recommend that you don't.

[uncljohn]

I know the more expensive battery switches have a feature to prevent you from turning the switch to the OFF position when running. That being said, I often will switch from my starting to my deep cycle once I get underway to top-off the charge, or vice versa. I've been warned against running on BOTH b/c the alternator on my engine (200 Yam 2-S) can't produce enough amperage to charge both batteries. But switching from one to the other should be fine.

[rj]

Dual battery switches operate on a "Make before break" principle
that means that the battery that you are switching to is conected before the connection to the battery that you are switching from is disconected-as long as your batteries are conected and have some charge (however small) left in them

,you can switch them while running

never switch to position that does not have a battery conected or to the Off position while running

when operating in the "Both" position the alternator & regulator will use the current from the hottest battery to determine the charge rate,,and will charge according to the needs of the hottest battery,,the lower of the two will not charge as fast or as completly as if the low battery was connected by itself

[BBCroaker]

Having worked on electrical equipment all my life I don't see it that way.(The alternator selecting the hotter battery)
Lookst to me like the lowere batt. would draw from the hotter batt. and then raise the current output from the alternator.
All the alternator sees is total current draw plus there is no seperation betwee nthe two when you have it switched to both.
Back to the original question.
You can switch between batteries while running but I never do it because of Murphy's law.

[MTPOCKETS]

Maybe a little electrical theory is in order here.

http://ffden-2.phys.uaf.edu/211.fall2000.web.projects/Jeremie%20Smith/page3.htm

The way I see it is like this. Once a battery becomes fully charged, the current flowing through it becomes a mere trickle. Therefore I see no reason not to switch over to the weaker battery after the running battery has been recharged, allowing the weaker battery to be topped off. I don't like to run in the "both" position because of the possibility of draining both down and placing a hefty load on the alternator. Hope this helps. [wink]

[hollandcrew]

Thanks for the input guys.
I have never switched with the engine running but, I have started from both batteries and charged from that position. It seems to me that the least charged battery within a few minutes was able to start the engine. I try to give both batteries a turn at some charge time during the day fishing.

*** Hope everyone has a great New Year!***

Al

[BBCroaker]

I usually run on one or the other and try to devide the time between the two equally.
I bought both of mine (Die Hards ) at the same time but prefer having bought them about 6mo.a year apart so both won't go at the same time.
I do like haveng dual batteries on board.

[Bob H.]

RJ is correct for the typical Perko switch. There are switches that can be switched while under power. I checked a few years ago and they were expensive. The rectifier will go if you don't have the proper switch.