Today is a great day - got my new charger and cables installed

kaz911

Active Member
Jan 24, 2011
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In Transit -> London
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Hi Guys and Girls :)

today was a great day. I replaced my SR 310's "standard" battery cables with some that are the RIGHT size for the 50 Ah Mastervolt ChargeMaster charger I put in.

The original cables put in by SR does really more damage to the batteries than good and are really too small for a 30 Ah factory charger.. And the charger was "okay" but I did not like the overall quality of it.

So today all my charge cables was replaced with AWG 2 (33.5 mm2) cables suitable for LOW voltage drop over the total of 9 meter cable (4.5m up - and 4.5 m back again). Circuit breakers got replaced with 50Ah versions and the "3rd" battery bank wires was put in as well despite I do not have a 3rd battery bank yet. :)

And in went a MasterVolt 3 Bank ChargeMaster 12/50 which is a really heavy duty charger.

And the result (pictures will follow later ) - pure joy....

Before when opening and closing the engine hatch while the old charger / cables was in - you could see the effect right away (with shore power connected) - battery voltage would drop - and lots of amps would be sucked out of batteries during the hatch open/close operation and recovery would take HOURS until batteries was back to full.

Now - I can hardly SPOT on my tracker WHEN the hatch was opened.

So if you want to do YOUR boat a favour! - Check your charger and charger cables for being sized right for your boat. Rule of thumb - minimum 10% of Ah should be the charger capacity. 15% is better....

So if you have like me 300 Ah in total battery capacity - your charger should be absolute minimum of 30A. And cables should be the right size as well. But that is slightly more complex to calculate.

But the total LENGTH of the cable has a big influence on the size of cable you should use. Else you might end up with my situation where the factory installed cables was so small that the 30A charger would NEVER EVER be able to deliver much more than 16A total. And charging from fully depleted back to "full" took almost 7 days...

So today is a great day and I know tomorrow will be as well :)
 
Wow, never thought about the charger wires going to the batteries being too small - but you are right - they are much smaller than the actual battery red/black wires going to the engine! That being said, I don't think our OEM chargers have attachment points that could even work for larger wire…

Looks like a new charger would be needed to utilize the larger feed wires to the batteries! Looking forward to some pics :grin:
 
Interesting. I don't recall this (charger cables being too small) being discussed much. Obviously you have a bank of batteries quite far from your charger and it sounds like the original install wasn't quite right. Electronics is not my strong suit, not by a long shot, but your write up is a good one. Thanks for taking the time to post.
 
I’ve never thought about it, but you are quite right. I am thinking of upgrading my charger, and if I do, cables would be part of it I guess. Thanks for the write up and bringing this to everyones attention!

Matt
 
Great Kaz,

Can you come and do mine for me now

I put 4 x6v deep cycle house batteries in last year, and bought a dedicated charger just for them........Umh it's still sitting in the garage.

My plan is to use the existing charger to charge the 2 start batteries, and run the 3rd output that was doing the house battery over to the generator battery that currently is not charged.

Then run the 2nd charger solely for the house setup.

Also replace the battery master switch setup from 2 to 3, so the house actually runs its own seperate circuit.

Now, the only issue is I'm suffering boat replacement fever, so it's whether I actually get this done before I sell it !


Sent from my iPad using Tapatalk HD
 
Well - voltage drop at big amps is a BIG issue for your batteries - and there are 3 ways of solving it..

1. Put sense cables from batteries to chargers. But I have not found any Marine chargers that supports sensing cables. Sensing cables can be thin as they are only measuring voltage and not transferring any Amp's. Then you can stay with smaller cables and still be within legal limits. But that would also mean your charger had to output a higher voltage

2. Redesign the DC circuit - put electrical operated battery switches and breakers in the engine room. <- BEST SOLUTION... Then you can cut out many meters of DC cables and use lighter and cheaper cables. That is my project for next year.... as it is quite expensive to do right. (2 x Mastervolt Mastershunt + Mastervolt DC500 distribution points + 2 x Blue Seas or BEP electrical battery switches .. $2000'ish) - I think that would remove about 100-150 lbs of cables! It can be done cheaper if you are not a gearhead like me...

3. Replace the cables... SR actually puts in the right 30 Ah breaker for the 310 30Ah charger. But then they put in 5mm2 (AWG 10) cables from charger - all the way back to control panel with breakers. On my 310 that is 4.5 meters. The return path is fine as that is AWG 4/0 (big very fat battery cable) as that is used for starting your engine - so it needs to transfer 200 Ah or more.

So in my case when battery was supposed to perform at 30 Amp - the voltage drop was enough to take voltage down by 0.88 volt. So if your charger thought it was charging with 14 V - at the batteries it would measure as 13.1. Even if the voltage drop is only 6% of total - it is 14v - 12.5v = 60% of your charge differential at worst case.

voltage_drop_SR_5mm2_30ah.JPG

That then means the battery wont absorb at the factory designed rate. That leads to much shorter battery life as the battery would never become really fully charged and it (for LA batteries) would sulphate the battery quicker. (http://autoeducation101.wordpress.com/2013/03/21/sulfation-kills-lead-acid-batteries/)

But even with my 50 Ah charger and AWG 2 cables - my voltage drop is 1.64% @ 50Amp but it is going to be very rare I need to charge with 50 Amp on one cable as the system is reasonably balanced between port and starboard as both banks are used as starter and house batteries. So the best compromise for me was AWG2 cables.

But if you run a 3 bank system with 1 house bank - the house bank will always take the big hit when you are on DC power without engines. So the cable from the charger to the house battery really need to be the right size.
 

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