Battery charger needs 8ga wire - ok to use a pair of 10ga?

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mcaswell

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Oct 28, 2008
154
none none LA
I'm installing a Truecharge 40 (replacing the original Guest 30 amp charger that is behaving strangely), and the manual recommends 8 gauge wire to the batteries. My crimper will only do 10 gauge, so I was thinking of running a pair of 10 gauge wires instead of the single 8 gauge (it's a short run... just 2 or 3 feet). Is this ok?

--Michael
 
Stu Jackson

Stu Jackson

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Feb 26, 2004
23,353
Catalina 34 224 Maple Bay, BC, Canada
Yes it is

because the total area of the two #10s (10,500 Cir. Mil area) exceed the single #8 (16,5800). Source: WM wiring sizing table, page 427, 2008 catalog. or any other handy wire sizing table.

We did the same thing with our fridge wiring, we paralleled two #12s instead of the #10 that was suggested by distance.

Get a better crimper, too.:)
 
Ron20324

Ron20324

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Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
Like Stu did, you can get away with it for some circuits, but I'd say NOT okay for the charger. You will be facing two problems. One, you will have to place a fuse - which SHOULD already be in place- near the battery and rated for the smaller 10 guage wire (probably 30-amps, like shore power cords). Two, that fuse would have to be rated lower than the 50-amp fuse the owners manual calls for the TC40. Even the TC40-amp output would/could exceed the rating of the 10 guage's 30-amp fuse. If you're only talking three feet, do it right and have someone make the cables for you. You only need a ring terminal on one end to attach to the fuse block. The TC end is a lock-crew clamp.

My B323 came with 6 guage wire on my TC20, so was sufficient when I moved up to a TC40. Problem was, all of that 6 would not fit in the lockscrew terminals on the TC. I had to cut some strands off to get all of them in. The larger size wire was a good thing considering how far the charge cable had to run. The first time I had drained the batteries and the TC40 put out high power, it blew the 25-amp fuses I had left in from the TC 20. Thank heavens there was a West store in Rock Hall.
 
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S

Steve Dion

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Dec 2, 1999
15,184
Hunter Vision-36 Rio Vista, CA.
Assuming that it is okay (and I really don't have an opinion) will you be able to get the lug/s on the wires and will it fit into the charger case?
 
GuyT

GuyT

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May 8, 2007
406
Hunter 34 South Amboy, NJ
Enough wire

Look - you can run 10 gauge at 40 amps all day long and not have any issues.
You dont even need to parallel wires - like you said it is a SHORT distance (2-3 ft.) and more importantly it is OPEN AIR which means that you can run extra current without significant temperature rise.
If it was me, I would only run one 10 gauge wire for 40 amps but you are more than safe with paralleling 2 ten gauge wires - that is the equivalent of a 7 gauge.

Some people go overboard(no punn intended) on wire size.
 
Don12364

Don12364

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Dec 2, 2003
1,637
Hunter 376 Warsash, England --
From AWG copper tables six feet of 10 gauge (there & back) will cause a voltage drop of 0.24 volts and will dissipate 9.6 watts of heat at 40 amps - probably more if the charger output is unsmoothed and has a large AC content.
At 40 amps the 8 gauge wire will drop 0.14 volts and dissipate 5.8 watts of heat.
If it is a modern 3 stage charger then you can ill afford to loose the quarter volt of single wire 10 gauge so you are quite correct in your surmise that you need thicker than 10 gauge - like the book says.

How you do it is up to you but doubling up on the cables is not seen as good practice. However your wiring will probably be very obvious so unlikely to cause confusion to later owners of your boat.
Go for it with two cables per side. i.e. 4 in all.
 
Rick Webb

Rick Webb

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Jun 2, 2004
3,650
Hunter 23.5 Fort Walton Yacht Club, Florida
How About Using the Crimper on the Bench at West Marine?

Sounds like a simpler solution to me
 
Ron20324

Ron20324

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Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
Steve Dion said:
Assuming that it is okay (and I really don't have an opinion) will you be able to get the lug/s on the wires and will it fit into the charger case?
Click to expand
The charger end of the wires does not get any lug. Strip the wire and stick it in a hole and secure it with a locking screw.
 
Timo42

Timo42

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Mar 26, 2007
1,042
Venture 22 Marina del Rey
This seems to be the genesis of one of those "what was the P/O thinking" moments.:doh: Someone down the road is going to be looking at a bundle of wires, possibly melted after the fuses blow and he doesn't notice the second wire and replaces the 30 amp fuse in one branch with a 50 amp because thats what the manual calls for and the short recurs and melts the wire and maybe several others that it is in contact with, shorting them too. Which causes a major amount of damage to electronics, smokes out the interior, causing the eventual downfall of western civilization.:eek: Ok maybe I am exaggerating a little. But I have seen similar scenarios in auto stereo installations, sometimes I have to tell the poor schmo that it is going to cost more than the truck is worth to fix it. I would do it right the first time, a little bigger wire than spec won't hurt anything, but a little smaller... Tim:D
 
S

Steve Dion

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Dec 2, 1999
15,184
Hunter Vision-36 Rio Vista, CA.
Can you stuff two 10ga wires in a hole made for one 8 ga? It is starting to make less sense every minute.
 
M

mcaswell

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Oct 28, 2008
154
none none LA
Actually, it turned out to be a non-issue... Hunter graciously had installed the original charger with 8 gauge wire (I expected to find 10 gauge), so I was able to use what was already there.

--Michael
 
RAD

RAD

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Jun 3, 2004
2,330
Catalina 30 Bay Shore, N.Y.
Keep it simple,go to Home Depot or any electric supply and ask for #8 lugs with screw terminals then go to West Marine and get # 8 wire and do the job right
 
M

mcaswell

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Oct 28, 2008
154
none none LA
RAD said:
Keep it simple,go to Home Depot or any electric supply and ask for #8 lugs with screw terminals then go to West Marine and get # 8 wire and do the job right
Click to expand

Thanks... this is good to know for future projects.

Interestingly, I was not able to find a crimper that will do 8ga. All of them that I saw (and the one I have) will only do 10ga-22ga. Then there's that heavy duty lug crimped that looks like you whack it with a hammer, but it only does 6ga - 4/0.

Is 8ga the unwanted stepchild of wire gauges?

--Michael
 
Ron20324

Ron20324

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Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
It might depend if you have the lug with the insulation, or the bare metal one. You could make the crimp with a round-nosed chisel or some-such punch. Someone posted a crimp picture he had done in a vise. Maybe granny's false teeth and a hammer?
 
RAD

RAD

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Jun 3, 2004
2,330
Catalina 30 Bay Shore, N.Y.
Also you can solder instead of crimp, although it says solderless nothing says you can't
 
Chuckbear

Chuckbear

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Jan 3, 2009
821
Marine Trader 34 Where Ever I am
RAD said:
Also you can solder instead of crimp, although it says solderless nothing says you can't
Click to expand
Soldering wire and connectors on a boat is not a good idea. Solder will break easily. Chuck
 
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