Wire Sizing Between Batteries?

Allen,

Wire must be sized for the expected load.

It should be fused to protect it and the connected equipment form
damaging current in the case of failure.

The cranking current of a 4-108 at shirtsleeve temperature is hard to
measure, but the peaks are around 500-600 ampere for 70-100 miliseconds
then dropping to 300-400 between peaks. If the fuse is in the cranking
circuit, I'm surprised it is still intact.

Stater motors are not very voltage sensitive. Most engines can crank on
a #2AWG wire and not have a problem.

Do not try to set up to crank from the house battery, just be sure that
the only load on the start battery is the engine. It is a waste of time
and effort and will only cause you problems.

This is what I do <www.southpointechandler.com>, in my area of the world.

If you want to discuss this more, I'm here alot.

Matt Colie


bushman wrote:
> I am ready to install new batteries. I have not found a reference for wire
> size - between - batteries. I have six T105 six volt batteries. What size
> wire should be used to series and parallel them? The boat has 2/0 with a
> 250amp fuse running to the battery selector switch. I am not sure how much
> my started draws (Perkins 4-108) but I would like to size to start from
> either the starting or house batteries or both. One more thing that does not
> look right is that the Neg wire on the starting battery is size one or two
> connected to the house bank Neg only. Shouldn't there be a jumbo size wire
> directly to the engine block at the starter?
>
> Thanks as always. I couldn't have come this far without you folks.
> - Allen
>
>
 >> Stay informed about: Wire Sizing Between Batteries? 

Thanks Chuck and Matt
I think I am OK with the size wire from the batteries to the boat or engine
but what is the load on the wire that joins the two 6 volt batteries in a
pair in series? I have three pairs joined in parallel so I'm guessing that
each pair would have one third my max load and the wires joining them would
need to be sized for accordingly. I generally like to go a size larger. You
never know when I might get stranded somewhere and can sell the copper off
to get me to the next island. The 250 amp fuse on the starting battery has
never blown. The Perkins generally fires on the first revolution but one
time I lost prime and had to crank for half a minute or more at a time and
the fuse held.
- Allen

"witheld" <nobody DeleteThis @netspam.net> wrote in message
news:rcGih.1260$oh.402@newsfe04.lga...
> Allen,
>
> Wire must be sized for the expected load.
>
> It should be fused to protect it and the connected equipment form damaging
> current in the case of failure.
>
> The cranking current of a 4-108 at shirtsleeve temperature is hard to
> measure, but the peaks are around 500-600 ampere for 70-100 miliseconds
> then dropping to 300-400 between peaks. If the fuse is in the cranking
> circuit, I'm surprised it is still intact.
>
> Stater motors are not very voltage sensitive. Most engines can crank on a
> #2AWG wire and not have a problem.
>
> Do not try to set up to crank from the house battery, just be sure that
> the only load on the start battery is the engine. It is a waste of time
> and effort and will only cause you problems.
>
> This is what I do <www.southpointechandler.com>, in my area of the world.
>
> If you want to discuss this more, I'm here alot.
>
> Matt Colie
>
>
> bushman wrote:
>> I am ready to install new batteries. I have not found a reference for
>> wire size - between - batteries. I have six T105 six volt batteries. What
>> size wire should be used to series and parallel them? The boat has 2/0
>> with a 250amp fuse running to the battery selector switch. I am not sure
>> how much my started draws (Perkins 4-108) but I would like to size to
>> start from either the starting or house batteries or both. One more thing
>> that does not look right is that the Neg wire on the starting battery is
>> size one or two connected to the house bank Neg only. Shouldn't there be
>> a jumbo size wire directly to the engine block at the starter?
>>
>> Thanks as always. I couldn't have come this far without you folks.
>> - Allen
 >> Stay informed about: Wire Sizing Between Batteries? 

Allen,
The strap between the two 6volt batteries should be the same as the
cable on both ends. More is no value(except as a cash reserve?) and
less is probably not much of and issue except as voltage drop. It will
be in -relatively- open air and if it gets hot enough to smoke it should
get your attention before it causes real trouble.

The fact that you are successful with three parallel pairs is quite
remarkable. The stacks (pairs) should not be counted on to share load
equally. It is actually very hard to make batteries do that.

I am surprized that a 250amp fuse will crank a 4-108. It must be a
better starter than the one I measured. Take good care of it.

Fair Wind and Smooth Sea
Matt Colie

bushman wrote:
> Thanks Chuck and Matt
> I think I am OK with the size wire from the batteries to the boat or engine
> but what is the load on the wire that joins the two 6 volt batteries in a
> pair in series? I have three pairs joined in parallel so I'm guessing that
> each pair would have one third my max load and the wires joining them would
> need to be sized for accordingly. I generally like to go a size larger. You
> never know when I might get stranded somewhere and can sell the copper off
> to get me to the next island. The 250 amp fuse on the starting battery has
> never blown. The Perkins generally fires on the first revolution but one
> time I lost prime and had to crank for half a minute or more at a time and
> the fuse held.
> - Allen
>
> "witheld" <nobody DeleteThis @netspam.net> wrote in message
> news:rcGih.1260$oh.402@newsfe04.lga...
>
>>Allen,
>>
>>Wire must be sized for the expected load.
>>
>>It should be fused to protect it and the connected equipment form damaging
>>current in the case of failure.
>>
>>The cranking current of a 4-108 at shirtsleeve temperature is hard to
>>measure, but the peaks are around 500-600 ampere for 70-100 miliseconds
>>then dropping to 300-400 between peaks. If the fuse is in the cranking
>>circuit, I'm surprised it is still intact.
>>
>>Stater motors are not very voltage sensitive. Most engines can crank on a
>>#2AWG wire and not have a problem.
>>
>>Do not try to set up to crank from the house battery, just be sure that
>>the only load on the start battery is the engine. It is a waste of time
>>and effort and will only cause you problems.
>>
>>This is what I do <www.southpointechandler.com>, in my area of the world.
>>
>>If you want to discuss this more, I'm here alot.
>>
>>Matt Colie
>>
>>
>>bushman wrote:
>>
>>>I am ready to install new batteries. I have not found a reference for
>>>wire size - between - batteries. I have six T105 six volt batteries. What
>>>size wire should be used to series and parallel them? The boat has 2/0
>>>with a 250amp fuse running to the battery selector switch. I am not sure
>>>how much my started draws (Perkins 4-108) but I would like to size to
>>>start from either the starting or house batteries or both. One more thing
>>>that does not look right is that the Neg wire on the starting battery is
>>>size one or two connected to the house bank Neg only. Shouldn't there be
>>>a jumbo size wire directly to the engine block at the starter?
>>>
>>>Thanks as always. I couldn't have come this far without you folks.
>>>- Allen
>
>
>
 >> Stay informed about: Wire Sizing Between Batteries? 

Thanks again Matt
I will upgrade wire and fuse with the new starting battery and take it off
the battery selector switch. That will shorten the run from 10 feet to less
than 3. I think I will buy 2 more 6 volts and have second house bank on the
selector switch. I will leave the wire from the switch to the starter in
place with a disconnect so that I can still crank from the house bank if
needed.

Looks like we will miss our Christmas Day sailing this year. We have made it
a tradition to go for a sail each year. However this year we are working.
- Allen

"Matt Colie" <mattcolie.DeleteThis@nospam.net> wrote in message
news:%Uijh.124$WD1.113@newsfe03.lga...
> Allen,
> The strap between the two 6volt batteries should be the same as the cable
> on both ends. More is no value(except as a cash reserve?) and less is
> probably not much of and issue except as voltage drop. It will be
> in -relatively- open air and if it gets hot enough to smoke it should get
> your attention before it causes real trouble.
>
> The fact that you are successful with three parallel pairs is quite
> remarkable. The stacks (pairs) should not be counted on to share load
> equally. It is actually very hard to make batteries do that.
>
> I am surprized that a 250amp fuse will crank a 4-108. It must be a better
> starter than the one I measured. Take good care of it.
>
> Fair Wind and Smooth Sea
> Matt Colie
>
> bushman wrote:
>> Thanks Chuck and Matt
>> I think I am OK with the size wire from the batteries to the boat or
>> engine
>> but what is the load on the wire that joins the two 6 volt batteries in a
>> pair in series? I have three pairs joined in parallel so I'm guessing
>> that
>> each pair would have one third my max load and the wires joining them
>> would
>> need to be sized for accordingly. I generally like to go a size larger.
>> You
>> never know when I might get stranded somewhere and can sell the copper
>> off
>> to get me to the next island. The 250 amp fuse on the starting battery
>> has
>> never blown. The Perkins generally fires on the first revolution but one
>> time I lost prime and had to crank for half a minute or more at a time
>> and
>> the fuse held.
>> - Allen
>>
>> "witheld" <nobody.DeleteThis@netspam.net> wrote in message
>> news:rcGih.1260$oh.402@newsfe04.lga...
>>
>>>Allen,
>>>
>>>Wire must be sized for the expected load.
>>>
>>>It should be fused to protect it and the connected equipment form
>>>damaging current in the case of failure.
>>>
>>>The cranking current of a 4-108 at shirtsleeve temperature is hard to
>>>measure, but the peaks are around 500-600 ampere for 70-100 miliseconds
>>>then dropping to 300-400 between peaks. If the fuse is in the cranking
>>>circuit, I'm surprised it is still intact.
>>>
>>>Stater motors are not very voltage sensitive. Most engines can crank on
>>>a #2AWG wire and not have a problem.
>>>
>>>Do not try to set up to crank from the house battery, just be sure that
>>>the only load on the start battery is the engine. It is a waste of time
>>>and effort and will only cause you problems.
>>>
>>>This is what I do <www.southpointechandler.com>, in my area of the world.
>>>
>>>If you want to discuss this more, I'm here alot.
>>>
>>>Matt Colie
>>>
>>>
>>>bushman wrote:
>>>
>>>>I am ready to install new batteries. I have not found a reference for
>>>>wire size - between - batteries. I have six T105 six volt batteries.
>>>>What size wire should be used to series and parallel them? The boat has
>>>>2/0 with a 250amp fuse running to the battery selector switch. I am not
>>>>sure how much my started draws (Perkins 4-108) but I would like to size
>>>>to start from either the starting or house batteries or both. One more
>>>>thing that does not look right is that the Neg wire on the starting
>>>>battery is size one or two connected to the house bank Neg only.
>>>>Shouldn't there be a jumbo size wire directly to the engine block at the
>>>>starter?
>>>>
>>>>Thanks as always. I couldn't have come this far without you folks.
>>>>- Allen
>>
>>
 >> Stay informed about: Wire Sizing Between Batteries? 

Allen,

It sounds like your plan is:
Have a dedicated starting battery,
have two banks of house battery on a selector switch and
an available cross-connect from house to start.

If I have that right, you have a good plan.
The cross connect switch should be the kind of Bosch switch you can take
the key out of and never close (but it is nice to know it is there).

Do you have a plan to charge all three banks?

I bet you can figure out how to push off and go out for at least a
little while.

We often use to sail Christmas Day. Even along the upper east coast, it
wa seldom too cold to sail and way too early to be frozen. I am on the
Great lakes now and the boats come out in October (fresh water freezes
too easily).

Where are You?

Matt


bushman wrote:
> Thanks again Matt
> I will upgrade wire and fuse with the new starting battery and take it off
> the battery selector switch. That will shorten the run from 10 feet to less
> than 3. I think I will buy 2 more 6 volts and have second house bank on the
> selector switch. I will leave the wire from the switch to the starter in
> place with a disconnect so that I can still crank from the house bank if
> needed.
>
> Looks like we will miss our Christmas Day sailing this year. We have made it
> a tradition to go for a sail each year. However this year we are working.
> - Allen
>
> "Matt Colie" <mattcolie.DeleteThis@nospam.net> wrote in message
> news:%Uijh.124$WD1.113@newsfe03.lga...
>
>>Allen,
>>The strap between the two 6volt batteries should be the same as the cable
>>on both ends. More is no value(except as a cash reserve?) and less is
>>probably not much of and issue except as voltage drop. It will be
>>in -relatively- open air and if it gets hot enough to smoke it should get
>>your attention before it causes real trouble.
>>
>>The fact that you are successful with three parallel pairs is quite
>>remarkable. The stacks (pairs) should not be counted on to share load
>>equally. It is actually very hard to make batteries do that.
>>
>>I am surprized that a 250amp fuse will crank a 4-108. It must be a better
>>starter than the one I measured. Take good care of it.
>>
>>Fair Wind and Smooth Sea
>>Matt Colie
>>
>>bushman wrote:
>>
>>>Thanks Chuck and Matt
>>>I think I am OK with the size wire from the batteries to the boat or
>>>engine
>>>but what is the load on the wire that joins the two 6 volt batteries in a
>>>pair in series? I have three pairs joined in parallel so I'm guessing
>>>that
>>>each pair would have one third my max load and the wires joining them
>>>would
>>>need to be sized for accordingly. I generally like to go a size larger.
>>>You
>>>never know when I might get stranded somewhere and can sell the copper
>>>off
>>>to get me to the next island. The 250 amp fuse on the starting battery
>>>has
>>>never blown. The Perkins generally fires on the first revolution but one
>>>time I lost prime and had to crank for half a minute or more at a time
>>>and
>>>the fuse held.
>>>- Allen
>>>
>>>"witheld" <nobody.DeleteThis@netspam.net> wrote in message
>>>news:rcGih.1260$oh.402@newsfe04.lga...
>>>
>>>
>>>>Allen,
>>>>
>>>>Wire must be sized for the expected load.
>>>>
>>>>It should be fused to protect it and the connected equipment form
>>>>damaging current in the case of failure.
>>>>
>>>>The cranking current of a 4-108 at shirtsleeve temperature is hard to
>>>>measure, but the peaks are around 500-600 ampere for 70-100 miliseconds
>>>>then dropping to 300-400 between peaks. If the fuse is in the cranking
>>>>circuit, I'm surprised it is still intact.
>>>>
>>>>Stater motors are not very voltage sensitive. Most engines can crank on
>>>>a #2AWG wire and not have a problem.
>>>>
>>>>Do not try to set up to crank from the house battery, just be sure that
>>>>the only load on the start battery is the engine. It is a waste of time
>>>>and effort and will only cause you problems.
>>>>
>>>>This is what I do <www.southpointechandler.com>, in my area of the world.
>>>>
>>>>If you want to discuss this more, I'm here alot.
>>>>
>>>>Matt Colie
>>>>
>>>>
>>>>bushman wrote:
>>>>
>>>>
>>>>>I am ready to install new batteries. I have not found a reference for
>>>>>wire size - between - batteries. I have six T105 six volt batteries.
>>>>>What size wire should be used to series and parallel them? The boat has
>>>>>2/0 with a 250amp fuse running to the battery selector switch. I am not
>>>>>sure how much my started draws (Perkins 4-108) but I would like to size
>>>>>to start from either the starting or house batteries or both. One more
>>>>>thing that does not look right is that the Neg wire on the starting
>>>>>battery is size one or two connected to the house bank Neg only.
>>>>>Shouldn't there be a jumbo size wire directly to the engine block at the
>>>>>starter?
>>>>>
>>>>>Thanks as always. I couldn't have come this far without you folks.
>>>>>- Allen
>>>
>>>
>
 >> Stay informed about: Wire Sizing Between Batteries? 

Yes that describes what I have in mind. I like that switch. I have a
xantrex?? 40 charger that will do 3 banks. I am not sure how the solar is
wired but it needs improving. I left the switch on the starting battery and
it killed it in 24 hours. Solar charges it when on the house. I believe I
have some current flowing with all the breakers off. This is just going to
take time to get it all mapped out.
As for Christmas sailing. I just finished 48 hours at work and Jackie is
doing 16. No big loss as we seem to see bad things on Christmas day. Dead
manatee, Fuel Spill, Sunk boat, Dead newborn dolphin with mother holding
its head up out of the water, Uncle got sick and had D-day flashback when a
stinky diesel went by. He spent 6 hours circling in a small landing craft in
diesel smog. He said he was so happy to get on the beach?????
Oh I did find a reference to fuse size for the starter from Casey. He says
to match the fuse to the wire size, looks like 0000 with a 400amp fuse. (if
I remember right.)
Thanks again - Allen


"Matt Colie" <mattcolie DeleteThis @nospam.net> wrote in message
news:fyxjh.933$nK1.94@newsfe06.lga...
> Allen,
>
> It sounds like your plan is:
> Have a dedicated starting battery,
> have two banks of house battery on a selector switch and
> an available cross-connect from house to start.
>
> If I have that right, you have a good plan.
> The cross connect switch should be the kind of Bosch switch you can take
> the key out of and never close (but it is nice to know it is there).
>
> Do you have a plan to charge all three banks?
>
> I bet you can figure out how to push off and go out for at least a little
> while.
>
> We often use to sail Christmas Day. Even along the upper east coast, it
> wa seldom too cold to sail and way too early to be frozen. I am on the
> Great lakes now and the boats come out in October (fresh water freezes too
> easily).
>
> Where are You?
>
> Matt
>
>
> bushman wrote:
>> Thanks again Matt
>> I will upgrade wire and fuse with the new starting battery and take it
>> off the battery selector switch. That will shorten the run from 10 feet
>> to less than 3. I think I will buy 2 more 6 volts and have second house
>> bank on the selector switch. I will leave the wire from the switch to the
>> starter in place with a disconnect so that I can still crank from the
>> house bank if needed.
>>
>> Looks like we will miss our Christmas Day sailing this year. We have made
>> it a tradition to go for a sail each year. However this year we are
>> working.
>> - Allen
>>
>> "Matt Colie" <mattcolie DeleteThis @nospam.net> wrote in message
>> news:%Uijh.124$WD1.113@newsfe03.lga...
>>
>>>Allen,
>>>The strap between the two 6volt batteries should be the same as the cable
>>>on both ends. More is no value(except as a cash reserve?) and less is
>>>probably not much of and issue except as voltage drop. It will be
>>>in -relatively- open air and if it gets hot enough to smoke it should get
>>>your attention before it causes real trouble.
>>>
>>>The fact that you are successful with three parallel pairs is quite
>>>remarkable. The stacks (pairs) should not be counted on to share load
>>>equally. It is actually very hard to make batteries do that.
>>>
>>>I am surprized that a 250amp fuse will crank a 4-108. It must be a
>>>better starter than the one I measured. Take good care of it.
>>>
>>>Fair Wind and Smooth Sea
>>>Matt Colie
>>>
>>>bushman wrote:
>>>
>>>>Thanks Chuck and Matt
>>>>I think I am OK with the size wire from the batteries to the boat or
>>>>engine
>>>>but what is the load on the wire that joins the two 6 volt batteries in
>>>>a
>>>>pair in series? I have three pairs joined in parallel so I'm guessing
>>>>that
>>>>each pair would have one third my max load and the wires joining them
>>>>would
>>>>need to be sized for accordingly. I generally like to go a size larger.
>>>>You
>>>>never know when I might get stranded somewhere and can sell the copper
>>>>off
>>>>to get me to the next island. The 250 amp fuse on the starting battery
>>>>has
>>>>never blown. The Perkins generally fires on the first revolution but one
>>>>time I lost prime and had to crank for half a minute or more at a time
>>>>and
>>>>the fuse held.
>>>>- Allen
>>>>
>>>>"witheld" <nobody DeleteThis @netspam.net> wrote in message
>>>>news:rcGih.1260$oh.402@newsfe04.lga...
>>>>
>>>>
>>>>>Allen,
>>>>>
>>>>>Wire must be sized for the expected load.
>>>>>
>>>>>It should be fused to protect it and the connected equipment form
>>>>>damaging current in the case of failure.
>>>>>
>>>>>The cranking current of a 4-108 at shirtsleeve temperature is hard to
>>>>>measure, but the peaks are around 500-600 ampere for 70-100 miliseconds
>>>>>then dropping to 300-400 between peaks. If the fuse is in the cranking
>>>>>circuit, I'm surprised it is still intact.
>>>>>
>>>>>Stater motors are not very voltage sensitive. Most engines can crank
>>>>>on a #2AWG wire and not have a problem.
>>>>>
>>>>>Do not try to set up to crank from the house battery, just be sure that
>>>>>the only load on the start battery is the engine. It is a waste of
>>>>>time and effort and will only cause you problems.
>>>>>
>>>>>This is what I do <www.southpointechandler.com>, in my area of the
>>>>>world.
>>>>>
>>>>>If you want to discuss this more, I'm here alot.
>>>>>
>>>>>Matt Colie
>>>>>
>>>>>
>>>>>bushman wrote:
>>>>>
>>>>>
>>>>>>I am ready to install new batteries. I have not found a reference for
>>>>>>wire size - between - batteries. I have six T105 six volt batteries.
>>>>>>What size wire should be used to series and parallel them? The boat
>>>>>>has 2/0 with a 250amp fuse running to the battery selector switch. I
>>>>>>am not sure how much my started draws (Perkins 4-108) but I would like
>>>>>>to size to start from either the starting or house batteries or both.
>>>>>>One more thing that does not look right is that the Neg wire on the
>>>>>>starting battery is size one or two connected to the house bank Neg
>>>>>>only. Shouldn't there be a jumbo size wire directly to the engine
>>>>>>block at the starter?
>>>>>>
>>>>>>Thanks as always. I couldn't have come this far without you folks.
>>>>>>- Allen
>>>>
>>>>
>>
 >> Stay informed about: Wire Sizing Between Batteries? 

Allen,
Well, at least it sounds like you missed the Christmas sail for a good
cause.

It sounds like you have a good shore charger.

If by left the start battery switched on, you mean the engine power was
left on, I am surprised that the engine support killed the start battery
.. The engine instruments should not draw that much power.

If you think you have a drain with all breakers open, I suggest you
locate it.
Expensive way - pull a battery terminal from a battery in the active
bank and put a millammeter in line. If it shows current when there
should be none, start detaching things until it goes away. Watch out
for automatic bilge pumps - if one switches on while the meter is inline
, it may smoke the meter.
Cheap way - come up with a small light bulb that you can clip into the
circuit. It will no give you a value, but if it lights, start
disconnecting things until it goes out.

A solar panel needs to have a charge isolator (a set of diodes) to keep
one bank from ble3eding back into the others. This device might be in
place if the alternator is charging three banks. If you have the
isolator, you do not need the blocking diode in the panel and that diode
will cost you charging voltage.

Fair Wind and Smooth Sea
Matt Colie


bushman wrote:
> Yes that describes what I have in mind. I like that switch. I have a
> xantrex?? 40 charger that will do 3 banks. I am not sure how the solar is
> wired but it needs improving. I left the switch on the starting battery and
> it killed it in 24 hours. Solar charges it when on the house. I believe I
> have some current flowing with all the breakers off. This is just going to
> take time to get it all mapped out.
> As for Christmas sailing. I just finished 48 hours at work and Jackie is
> doing 16. No big loss as we seem to see bad things on Christmas day. Dead
> manatee, Fuel Spill, Sunk boat, Dead newborn dolphin with mother holding
> its head up out of the water, Uncle got sick and had D-day flashback when a
> stinky diesel went by. He spent 6 hours circling in a small landing craft in
> diesel smog. He said he was so happy to get on the beach?????
> Oh I did find a reference to fuse size for the starter from Casey. He says
> to match the fuse to the wire size, looks like 0000 with a 400amp fuse. (if
> I remember right.)
> Thanks again - Allen
>
>
> "Matt Colie" <mattcolie RemoveThis @nospam.net> wrote in message
> news:fyxjh.933$nK1.94@newsfe06.lga...
>
>>Allen,
>>
>>It sounds like your plan is:
>>Have a dedicated starting battery,
>>have two banks of house battery on a selector switch and
>>an available cross-connect from house to start.
>>
>>If I have that right, you have a good plan.
>>The cross connect switch should be the kind of Bosch switch you can take
>>the key out of and never close (but it is nice to know it is there).
>>
>>Do you have a plan to charge all three banks?
>>
>>I bet you can figure out how to push off and go out for at least a little
>>while.
>>
>>We often use to sail Christmas Day. Even along the upper east coast, it
>>wa seldom too cold to sail and way too early to be frozen. I am on the
>>Great lakes now and the boats come out in October (fresh water freezes too
>>easily).
>>
>>Where are You?
>>
>>Matt
>>
>>
>>bushman wrote:
>>
>>>Thanks again Matt
>>>I will upgrade wire and fuse with the new starting battery and take it
>>>off the battery selector switch. That will shorten the run from 10 feet
>>>to less than 3. I think I will buy 2 more 6 volts and have second house
>>>bank on the selector switch. I will leave the wire from the switch to the
>>>starter in place with a disconnect so that I can still crank from the
>>>house bank if needed.
>>>
>>>Looks like we will miss our Christmas Day sailing this year. We have made
>>>it a tradition to go for a sail each year. However this year we are
>>>working.
>>>- Allen
>>>
>>>"Matt Colie" <mattcolie RemoveThis @nospam.net> wrote in message
>>>news:%Uijh.124$WD1.113@newsfe03.lga...
>>>
>>>
>>>>Allen,
>>>>The strap between the two 6volt batteries should be the same as the cable
>>>>on both ends. More is no value(except as a cash reserve?) and less is
>>>>probably not much of and issue except as voltage drop. It will be
>>>>in -relatively- open air and if it gets hot enough to smoke it should get
>>>>your attention before it causes real trouble.
>>>>
>>>>The fact that you are successful with three parallel pairs is quite
>>>>remarkable. The stacks (pairs) should not be counted on to share load
>>>>equally. It is actually very hard to make batteries do that.
>>>>
>>>>I am surprized that a 250amp fuse will crank a 4-108. It must be a
>>>>better starter than the one I measured. Take good care of it.
>>>>
>>>>Fair Wind and Smooth Sea
>>>>Matt Colie
>>>>
>>>>bushman wrote:
>>>>
>>>>
>>>>>Thanks Chuck and Matt
>>>>>I think I am OK with the size wire from the batteries to the boat or
>>>>>engine
>>>>>but what is the load on the wire that joins the two 6 volt batteries in
>>>>>a
>>>>>pair in series? I have three pairs joined in parallel so I'm guessing
>>>>>that
>>>>>each pair would have one third my max load and the wires joining them
>>>>>would
>>>>>need to be sized for accordingly. I generally like to go a size larger.
>>>>>You
>>>>>never know when I might get stranded somewhere and can sell the copper
>>>>>off
>>>>>to get me to the next island. The 250 amp fuse on the starting battery
>>>>>has
>>>>>never blown. The Perkins generally fires on the first revolution but one
>>>>>time I lost prime and had to crank for half a minute or more at a time
>>>>>and
>>>>>the fuse held.
>>>>>- Allen
>>>>>
>>>>>"witheld" <nobody RemoveThis @netspam.net> wrote in message
>>>>>news:rcGih.1260$oh.402@newsfe04.lga...
>>>>>
>>>>>
>>>>>
>>>>>>Allen,
>>>>>>
>>>>>>Wire must be sized for the expected load.
>>>>>>
>>>>>>It should be fused to protect it and the connected equipment form
>>>>>>damaging current in the case of failure.
>>>>>>
>>>>>>The cranking current of a 4-108 at shirtsleeve temperature is hard to
>>>>>>measure, but the peaks are around 500-600 ampere for 70-100 miliseconds
>>>>>>then dropping to 300-400 between peaks. If the fuse is in the cranking
>>>>>>circuit, I'm surprised it is still intact.
>>>>>>
>>>>>>Stater motors are not very voltage sensitive. Most engines can crank
>>>>>>on a #2AWG wire and not have a problem.
>>>>>>
>>>>>>Do not try to set up to crank from the house battery, just be sure that
>>>>>>the only load on the start battery is the engine. It is a waste of
>>>>>>time and effort and will only cause you problems.
>>>>>>
>>>>>>This is what I do <www.southpointechandler.com>, in my area of the
>>>>>>world.
>>>>>>
>>>>>>If you want to discuss this more, I'm here alot.
>>>>>>
>>>>>>Matt Colie
>>>>>>
>>>>>>
>>>>>>bushman wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>>>I am ready to install new batteries. I have not found a reference for
>>>>>>>wire size - between - batteries. I have six T105 six volt batteries.
>>>>>>>What size wire should be used to series and parallel them? The boat
>>>>>>>has 2/0 with a 250amp fuse running to the battery selector switch. I
>>>>>>>am not sure how much my started draws (Perkins 4-108) but I would like
>>>>>>>to size to start from either the starting or house batteries or both.
>>>>>>>One more thing that does not look right is that the Neg wire on the
>>>>>>>starting battery is size one or two connected to the house bank Neg
>>>>>>>only. Shouldn't there be a jumbo size wire directly to the engine
>>>>>>>block at the starter?
>>>>>>>
>>>>>>>Thanks as always. I couldn't have come this far without you folks.
>>>>>>>- Allen
>>>>>
>>>>>
>
>
 >> Stay informed about: Wire Sizing Between Batteries?