Cranking battery specs used Bassport 250XS in lead acid and possibly Lithium

[Tim Sykes]

Hey guys,
When I got my ally I think the guy just stuck a cranking battery in it that was not right. What do most of you run as the cranking battery in lead acid? I do have 3 graphs too and propoles.


PS: I would also like to know if anyone is running a lithium battery as a starter as well and what AH it is

Thanks

 

[BigRWater]

I saw that some people on this and other forums were using lithium batteries for cranking these big outboards, and so I did some research again. I have not found any recommendations for cranking these big outboards. My motor has a 40 amp charging system. Supposedly the lithium battery can only tolerate such a high charging current for maybe ten minutes According to Mercury's web site your motor has a 60 amp charging system. I am not an expert, so I won't even guess how long a Lithium battery will tolerate 60 amps.

One guy told me that the lead acid batteries are factored into many of the charging system designs.

I have the smallest lead acid battery that the local battery store sells for cranking the big motor (it weighs a little under 30 pounds). With all of the electronics that I have on my boat these days, I could not find a lead acid battery that could crank and run everything else predictably.

I have a 100ah lithium 12 volt in my boat that I use to run everything else, except cranking the big motor, and the trolling motor is on a couple 36 volt lithium batteries in parallel.

I hope somebody who knows more than I know, has a different answer, because I already have the lithium 12 volt sitting in my boat.

http://www.mercuryracing.com/outboards/engines/optimax-250-sport-xs/

 

[SLOmofo]

So you have a lead acid to start and run the boat, this battery is being charged by the engine. Then also a lithium to run other 12 volt items that is not wired to the motor..not being charged be the engine. A battery's state of charge tells the regulator how much the charging system should put out. When the battery nears a full charge the (voltage) regulator limits the rate of charging. Different types of battery's require a different charging voltage limit. Lead acid flooded cell, AGM, Lithium....
Just think of how a toilet valve decreases the flow as the water gets to the full point. It's the same as the altenator output... empty= full output... close to top output limited. The alternator only puts out those 60 amps when the battery is discharged greatly enough. Otherwise the alt maintains the system at the voltage regulator limit.

 

[BigRWater]

So you have a lead acid to start and run the boat, this battery is being charged by the engine. Then also a lithium to run other 12 volt items that is not wired to the motor..not being charged be the engine. A battery's state of charge tells the regulator how much the charging system should put out. When the battery nears a full charge the (voltage) regulator limits the rate of charging. Different types of battery's require a different charging voltage limit. Lead acid flooded cell, AGM, Lithium....
Just think of how a toilet valve decreases the flow as the water gets to the full point. It's the same as the altenator output... empty= full output... close to top output limited. The alternator only puts out those 60 amps when the battery is discharged greatly enough. Otherwise the alt maintains the system at the voltage regulator limit.

Very good. Thanks.

Speaking of limits, with the lithium batteries I bought, the charging system must be AGM and Gel battery compatible. And insure the charger’s float voltage is 13.5V or less.

Here is a link to a product that might help some folks: http://www.cdielectronics.com/blog/regulated-rectifier/
And there is a battery/charger 101 pamphlet at the very bottom of the page.

 

[SLOmofo]

An aside. Here is the way I use two 12 volt batteries. It will charge both but if I want 24 for the trim it uses the up trim to switch to 24 on the trim circuit. At rest it's just a large 12 volt. Another pic is how the trim circuits can be 12v, 24v and variable voltage.

 

[BigRWater]

An aside. Here is the way I use two 12 volt batteries. It will charge both but if I want 24 for the trim it uses the up trim to switch to 24 on the trim circuit. At rest it's just a large 12 volt. Another pic is how the trim circuitsView attachment 12849View attachment 12850 can be 12v, 24v and variable voltage.

Nice. Thank you. I will show this to my boat mechanic.

 

[SLOmofo]

Glad to help, hope it works out. Just remember there is only one ground permitted...otherwise you will have trouble.