A series resistor to limit the current to about 1 amp should not cause the
battery voltage to rise too far. The wattage the battery will be expected to
dissipate will only be about 1*14= 14W at this level it should not get warm.

This is not going to overheat or boil a battery of say 75 or more AH. Limit
the current to a lower level if the battery is smaller.

A car bulb makes a good dropping resistor as the resistance rises if the
current rises and they are meant to dissipate power.

This is constant current charging, not constant voltage as from a typical
car alternator. Constant voltage charging can harm any battery if it is too
high as the current will remain at a high level for too long and the battery
will overheat, not good on any sealed battery.

Alec




wrote in message
...
On Wed, 14 Nov 2007 16:05:00 -0800, wrote:


Well, you might be right about the common cable and the cheaper
route/solution being the flooded battery, but I can find a 30 amp
isolator for $140. But if you must have that overpriced Guest stuff,
yeah, you'll pay $300 for it.


Math lesson #1: $140 $50


BTW, agm's are not quickly ruined by having over 14 volts on them. We
use hundreds of Lifeline agm's where I work and the bulk charge spec.
for them is 14.2-14.4 volts. Float charge should be kept at 13.3 or
under. And once fully charged, can be equalized at 15.5 volts for 8
hours when neccessary. As stated in their documentation: "Regardless
of what some rumors portray, AGM batteries are not as sensitive as
once believed. They often get confused with Gel Batteries, which are
very sensitive to voltage and they need a special charger."


Confused? I'm not the one who thinks a $140 work-ariound is superior to a
$50
Solution. :')

And here's a little tip: An AGM battery can be effectively charged at 13.5
volts. A flooded battery needs more than that just to begin charging.
There is a
difference in internal resistance. And for purposes of this thread, the
essentially unregulated voltage from a 10 hp Honda outboard IS enough to
quickly
ruin an AGM battery. That's the subject under discussion. I stated that
AGM's
can be damaged by voltages above 14.

Math lesson #2: 15 volts 14 volts


I'll repeat: A new flooded battery will solve the issue for about $50


Eric

On Nov 14, 9:06 am, wrote:

Yeah, and a 30 amp galvanic isolator to protect that $150 AGM battery
will run you about $300 or more! If the Honda outboard in question has
electric start, you will need one that will handle 100 amps, as that
is about what the starter motor draws, and the same cables from the
motor to the battery are used for both starting and charging.

I'll repeat: A new flooded battery will solve the issue for about $50.