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hi youtubers

jeff cote here we've got another ask pys

from richard

richards from maryland and he's got a

calendar 36

i also have a catalina 36 this happens

to be in 1989 mine is in 1990 so

lovely boat by the way now that i'm

biased

um so this uh boater is asking jeff i'm

changing my alternator from a 50 amp

alternator to 105 amp alternator

how will this affect my agm batteries oh

great question well first of all

your alternator charging changing

the size of an alternator can affect

really the speed at which you're going

to recharge your batteries

but it's not really going to change the

charging profile

so an alternator most alternators are

going to have what are called an

internal regulator and they're going to

output

14.4 volts okay so you've got 14.4 volts

and that's not necessarily what your agm

battery wants

so if you want to worry about your agm

batteries what you end up doing is

getting what's called an external

regulator

you basically make your alternator smart

and then you can actually dial it in and

say i want you to charge an agm profile

firefly profile

gel profile lithium profile whatever it

is but then you can start tweaking it

if you don't have an external regulator

you can't do any of that and you're just

getting vanilla

14.4 volts on a 12 volt alternator

period

and that's what it's and that's what our

cars are doing that's why when we start

our cars we look at

the nominal voltage is around 14. that's

because we're actually measuring

the output of the alternator we're not

actually measuring the battery we're

measuring the output of the alternator

so by changing from a 50 amp to 100 amp

alternator

it's not so much that it's going to

affect your agm batteries right

mind you agm have a higher charge

acceptance rate which is called

car so they're going to be able to take

a better faster charge than a flooded

lead acid battery bank

but the key is now here's the things i

would

look for a is my wire size going to be

able to handle

now 100 amps coming from my alternator

right that's the first thing because

remember most of us have

the alternator connected directly to the

starter solenoid post

so there's a little wire it's probably

two feet three feet four feet

and that positive post on the alternator

is just connected to the starter

solenoid

but if that wire is made for handling a

50 amp alternator

i can guarantee you that the engine

manufacturer never ever

oversized that wire they chose that wire

exactly for that 50 amp alternator so

when you choose your alternator you go

from 50 to 100

that wire now is half the size it should

be so make sure that that wire can

handle the 100 amps

and if you're worried about the agm

batteries having the right charge

then the way to do that would be by

installing an external

regulator that you can customize or

change

or choose a charge profile and that will

give your agm batteries

exactly what they need from the

alternator effectively

transforming your alternator into a

smart

battery charger that is powered from

your engine

and not shore power so that was a great

question richard and thanks for asking

thank you for watching this pys video if

you've got further questions please ask

it below or contact

us on our contact form on our website

and don't forget to subscribe thanks