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hi everyone jeff cote here with

boatingtechtalk.com

we are at the pys studios doing some

questions

and here we have a question from yannick

a fellow boater

uh yannick says jeff i have two 8d

batteries for the starter bank and two

8d batteries for the house bank

an ad battery weighs about 160 pounds

so give and take maybe i'm going to do

some math in my head

maybe about 60 kilograms

probably 70 kilograms it's heavy it's

about this big

it's about so this long about this wide

and about this high it's a it's a beast

they're really hard to put in the boat

and take out a boat

they're basically big truck batteries

not my favorite thing to put in a boat

or remove from a boat

but a lot of us have ad batteries on

board

okay would it be advisable to rewire one

of the starter batteries

into the house bank so the house bank

would now have

three ad batteries

that is good stuff

okay all right well first of all

the question would be there's so many

there

is this is a question with full of

landmines

there is so many so many potential

pitfalls for doing this

one is the fact that the batteries

assuming all the batteries are the same

i they're all identical so they were all

deep cycle batteries

right so even though two batteries were

on the starter

the person who bought those batteries

bought all deep cycle batteries

and that would be the first qualifying

you can never

ever ever ever have a starter battery

run house loads continuously if you do

that

you're gonna probably have some

fireworks on your boat and i mean

your batteries may very likely explode

no joke

it happens i get service calls every

summer

of an unfortunate boner that had a

starter battery installed on a deep

cycle

sort of circuit so they installed a

starter battery for households

and by doing that what happens is the

battery is not meant to be cycling

all the time and that battery is a hard

time and really because a starter

battery is like a sprinter

a sprinter and a marathon runner are

both athletes

but they have completely different

builds they don't look alike at all

completely different starter battery and

a deep cycle battery are not the same

it's like a sprinter and a marathon

runner

and unfortunately a sprinter should and

cannot really run a marathon really well

and if you do that repeatedly it's very

possible that that starter battery

might over time lose a lot of its

electrolyte and you might not know

and that electrolyte eventually is going

to also as you're

cycling that battery really hard the

plates are going to warp

and eventually there's going to be less

electrolyte and the plates are going to

be exposed yes

these are all things that do happen and

eventually what guess what happens when

two plates that have touch in a battery

not an electrolyte because they've

warped

and the battery as it's charging guess

what's in the battery

full of hydrogen so now you have a

battery bank

with lots of hydrogen in it and

eventually those two plates

might touch and when they touch what

will happen a spark

i can tell you that when that happens

it's an unforgettable moment

in your boat ownership life so great

question from yannick

never ever ever have a starter battery

run deep cycle loads so assuming that

we've got four batteries

two on the starter and two on the house

that are

all the same make they're all deep cycle

batteries okay

sure then theoretically you could take

that house battery

you can move it and bring it to which

was on the starter you can move it to

the house

now the challenge is you never ever

again want to put batteries in parallel

if they don't have the same sort of

cycle life

right batteries age over time

and they age differently depending on

what their purposes are

so again if the batteries are completely

brand new and you had one cycle

no problem two cycles no problem ten

sure but if you've been using those

batteries for two or three years

no go can do it it's like buying you

know it's like having a flat on one of

your tires in your car

and then instead of buying a whole new

set you're at the dealer and say you

know what actually i'm just going to buy

a tire of one

i'm not going to buy a set i'm going to

have a brand new tire on one wheel and

the other wheels will have old tires you

can't do that and you can't do that with

batteries so that's another caveat

is all the batteries would pretty much

have to have the same age and in this

case they would have to be

almost brand new that you could actually

put a third battery that was in a

different bank

to go into your house bank okay that's a

lot of ifs so the short answer is

obviously

probably not right but the other issue

and there's a follow-up question to this

question he says

the starter bank is about 10 feet from

the house bank and i would intend to use

two watt tin

wire to bring the third battery in the

bank that's where it also gets more

complicated

ideally so this is the third qualifying

sort of

reason why not to do this having a

battery bank that is in parallel but not

at the same place

is fraught with perils it's just no good

no good if you've got an inverter

charger for example that is monitoring

thermal runaway and you have your

battery banks in

two places where where are you going to

put the temperature sensor to measure

thermal runaway

right this thermal runaway is what

caused batteries and laptops to catch on

fire

and even happen in boeing you know they

have a thermal runaway it happens

and if you've got one temp sensor where

are you gonna put it are you gonna put

it on one of the batteries or two of the

batteries

it gets complicated so ideally you want

your bank to be in one single location

so yannick unfortunately i would advise

against doing that

i would suggest if you want a larger

bank and yes i am suggesting you to

spend more money i

would wait it out and eventually just

change my

two-way ds for maybe l16s you know

higher batteries and change the

configuration but i would not

advise and of course people do it i mean

my advice is just advice

i would not advise on actually putting

two battery banks

in parallel over long distances it's

just not a good idea

and yes you can get away with it until

you don't and maybe you'd be the unlucky

one so my advice

is keep your batteries separate and

especially considering that

one of them might be a starter battery

which can never use this deep cycle

and if they're of any age a year or more

if one of those batteries

is basically cycled differently you

can't mix and match so those are three

strikes

why i would not do this setup but again

your boat

your way thanks for asking thank you for

watching this pys video

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