Battery Isolator

[Dire Straits]

Hey Guys
Need help on deciding what isolator to get for my boat. I have a 3 battery setup with 2 cranking batteries and 1 house deep cycle battery. I have twin SX200 yamaha outboards.
does the isolator need to have a certain amp rating, etc.?

[boscoe99]

Define what you mean by "isolator" please.

[Dire Straits]

A isolator is a electrical device that divides direct current (DC) into multiple branches and only allows current to flow in one direction in each branch.
The benefit is to guard against a weak or dead battery from draining the charge of a strong battery in a muti-branch configuration.

[rodbolt17]

why buy an isolator?
your engines came from the factory with battery isolators, just add the lead between the engine and the house battery.

[Dire Straits]

Thanks Rodbolt

If your not carefull you'll learn something everyday....

[rodbolt17]

I giggle every time I have to bypass one of those high dollar VSR type isolators and hook up the engine isolator.
almost all V6 vamahas,the v8 and the F150 and up have a built in isolator.
its there all that needs to be done is a lead of the correct wire gauge and a fuse.
the old 3.1L motors had the lead made into the battery cable harness.

[boscoe99]

A isolator is a electrical device that divides direct current (DC) into multiple branches and only allows current to flow in one direction in each branch.
The benefit is to guard against a weak or dead battery from draining the charge of a strong battery in a muti-branch configuration.

I just wanted to make sure that I understood what you were wanting to do. Yamaha uses the term isolator lead to get current to a second battery. I thought you might have been talking about that lead. Early Yamaha isolator leads do not have circuit protection (fuse or circuit breaker). You will need to add at least one to the Yamaha isolator lead for an SX motor.

The electronic device known as an isolator has an inherent deficiency insofar as it uses diodes which result in voltage drop. When starting with 12 ~ 14 volts it is not desireable to lose any voltage as this will slow down the current flow.

The problem with the Yamaha isolator lead is that in a number of cases it can cost more than a different component which offers the same benefit. Plus, you don't have to install and route another cable from the motor to the battery.

The isolator device for the most part has been replaced by a device known as an automatic charge relay (ACR), voltage sensitive relay (VSR) or combiner. When ever the engine is producing certain voltage the device will automatically parallel two or more batteries so that each will be charge while the motor is running. Stop the motor and the device disconnects the start battery from the other battery(s).

I have used and can recommend the Yandina combiner. It works and works well. Installation is a snap. Three wires. One wire to the positive post of the start battery, one wire to the positive post of the house battery and one wire to the negative wire of either battery. It costs less than the Yamaha isolator lead and is a hell of a lot easier to install.

Combiner 100 Sheet

[Dire Straits]

Thank-you for that info. Would you know what the alternator amp output is for a 2002 SX200TXRA ?

[boscoe99]

Maximum generator output is 35 amps. However, a good bit of these amps are needed to run the motor. Maybe 25 amps are available to recharge a battery or two.

[Dire Straits]

Thanks fot the info.!!

Dave

[Skyking711]

First Yamaha. f90 4 stroke. Second Battery

Hello
I'm a newbie to Yamaha 4 stroke motors and If I break it, the wife will not be happy..

Wanted to add a second battery and was planning on using the Blue Sea Systems Mini 65A Add-A-Battery Kit. which includes the M-ACR. (a bit expensive but worth it for my family users)

Two questions:
Would this M-ACR be redundant for this motor.

What wire size is the OEM harness? I can not find the gauge size listed in any lit. (or, what size jumper wire w/ be reco'ed for the second battery. 4?)

Thanks in advance for your help

[boscoe99]

Yamaha refers to their second battery isolator as a "multi charge monitoring system". Unfortunately, the F90 does not offer this feature.

What will work just as well is a Yandina battery combiner. It comes complete with terminals that are simply connected to two batteries. One terminal for each positive post and one terminal for a negative post. Of course the two batteries will have to have a common ground connection.

The Yandina combiner by the way is cheaper than buying just the Yamaha isolator lead. Cheaper than buying the Blue Seas System. Easier to install IMO and as I mentioned, just as effective.

Connect just the main motor to the starting battery. Connect the second battery to everything else in the boat. The Yandina of course will be connected between the two batteries. Any time the main motor is running it will recharge the starting battery first and as soon as the starting battery is recharged it will start charging the second battery as well. Turn off the motor and the batteries are electrically separated from each other. You can run the second battery to depletion without having to worry about the starting battery being charged and able to start the main motor.

Yandina Marine Electronics

The Combiner 100 will be more than capable of supporting any Yamaha outboard motors electrical generation system.

[99yam40]

interesting device, but with what they say on the web site "connects two batteries together when either is receiving a charge", I am not sure it would wait for the 1st battery to be charged up before connecting them together unless the voltage was so low while charging the 1st one

[boscoe99]

interesting device, but with what they say on the web site "connects two batteries together when either is receiving a charge", I am not sure it would wait for the 1st battery to be charged up before connecting them together unless the voltage was so low while charging the 1st one

It is a voltage sensitive relay. It will not parallel two batteries unless and until one of them has risen to the set point voltage of the relay. Literature says that it is 13.3 volts for the C100 combiner.

Let's take the starting battery. Before start it will be approximately 12.7 volts if it is fully charged. The relay in the combiner is open. After starting the motor the battery voltage will be slightly less than 12.7 volts. Once the generator starts feeding voltage to the battery the battery voltage will rise. Once the battery voltage reaches 13.3 volts the relay will close and parallel both batteries. The generator output of course will rise to more or less 14.5 volts. Both batteries will then be charged at the same time by the generator.

If the motor is turned off, there is no more 14.5 volts being provided to the batteries. The voltage will start to decay to the normal full charge voltage of 12.7 volts. Once the voltage has dropped to 13.2 volts, on its way from 14.5 volts to 12.7 volts, the relay will open. Both batteries will be isolated from each other. The house battery will provide all electrical loads that are needed while the start battery remains fully charged at 12.7 volts.

Start the motor and the whole process repeats itself.

It is a pretty nifty device be it called a combiner, an active charge relay (ACR) or a voltage sensitive relay (VSR) or whether it is done by the Yamaha rectifier/regulator. Same device doing the same job with different names. I won't have a boat without one.

[boscoe99]

Oh, what's interesting to me is that Yamaha even sells one of the devices. Competes with the sales of their isolator leads for those model motors that can use the lead.

2014 Yamaha MRP Catalog

SBT-DUALB-AT-08 MARINE DUAL BATTERY