agm

[ranger175a]

Will my 85 yamaha 175 charge an agm battery.

[boscoe99]

Absolutely, positively.

Slowly maybe, but surely.

[TownsendsFJR1300]

AGM's are MOSTLY used in the Motorcycle world, lead/acid went out years ago(at least a decade in most bikes). From small bikes, to 200HP plus bikes.

AS Boscoe posted, shouldn't be an issue and IME with the bikes, charge up easily...

[rodbolt17]

AGM batteries are specifically not recommended by Yamaha for that motor.

[TownsendsFJR1300]

AGM batteries are specifically not recommended by Yamaha for that motor.

Interesting, do you know why or have an educated guess? Just curious..

[boscoe99]

Interesting, do you know why or have an educated guess? Just curious..

It is a great mystery.

For years and years Yamaha poo poo'd AGM's batteries for any of their motors. Even though AGM's are indeed a lead acid battery with the same charging characteristics. And even though many were using them just fine.

All of a sudden, what was forbidden (AGM batteries for certain motors) are now, miraculously, perfectly acceptable.

Another anomaly. Yamaha formerly specified rather large Reserve Capacity (RC) requirements for batteries being used with certain motors. Again, all of a sudden, those requirements no longer have to be met.

And finally, Yamaha is now saying that there should be maximum size limits on certain batteries.

Makes one wonder if Yamaha really knows what in the heck is going on. Or, is this coming from Mitsubishi?

[TownsendsFJR1300]

It is a great mystery.

For years and years Yamaha poo poo'd AGM's batteries for any of their motors. Even though AGM's are indeed a lead acid battery with the same charging characteristics. And even though many were using them just fine.

All of a sudden, what was forbidden (AGM batteries for certain motors) are now, miraculously, perfectly acceptable.

Another anomaly. Yamaha formerly specified rather large Reserve Capacity (RC) requirements for batteries being used with certain motors. Again, all of a sudden, those requirements no longer have to be met.

And finally, Yamaha is now saying that there should be maximum size limits on certain batteries.

Makes one wonder if Yamaha really knows what in the heck is going on. Or, is this coming from Mitsubishi?

Thanks Boscoe..

A thread I found very interesting re AGM's:

http://www.thehulltruth.com/boating-...es-yamaha.html

Seems there may be some issues with charging batteries other than lead acid batteries and some consequences..

[boscoe99]

Thanks Boscoe..

A thread I found very interesting re AGM's:

No AGM batteries for Yamaha??? - The Hull Truth - Boating and Fishing Forum

Seems there may be some issues with charging batteries other than lead acid batteries and some consequences..

Other battery types, such as a gell cell, can be a problem. For the battery, not the motor.

People tend to overlook the fact that the Yamaha system is a permanent magnet generator. At any given engine RPM it creates all of the electrical power that it is capable of producing.

If a battery has a low state of charge then more of the available current will flow to the battery. As the battery becomes charged, less current will flow to it. At some point, the battery is more or less fully charge with almost no current flowing to it.

Now since the system is creating a lot of electricity (all that it is capable of at a specific engine RPM), most of which is not needed, what happens to it? It is wasted in the form of heat. Current is shunted to ground to keep the output voltage more or less constant. This is why the smaller rectifier/regulators use cooling fins and the larger rectifier/regulators are water cooled.

The rectifier/regulator neither knows nor cares what type of battery is connected to it. All it knows to do is to maintain its own output voltage. Let's use 14.6 volts as an example. If the voltage is higher than this value then the R/R shunts current to ground (applies a load actually) which drives the voltage down. If the voltage goes below the set point voltage of 14.6 then less current is shunted to ground (less load applied) and the voltage rises.