Wire gauge recommendation

[johnm1]

To get the most efficent charging to my batteries, with cost kept in mind, what wire gauge should I use between the batteries and charger?

I have a pair of 6v gc batteries.
They're about 12-15 feet from the charger.
I have a Boondocker 75A charger.
Currently have 6awg wire with very good crimped battery lugs.

Thanks

[johnm1]

I kind of figured y'all would say the 6 gauge was on the small side so I have no problem going up in wire size.

However, some of you have me concerned about the Boondocker 75A charger hurting my batteries. Short of "junking" the charger for something smaller, what should I do? Can I somehow limit the current out of the Boondocker? Would adding 2 more batteries help?

BTW: what happens when you put too much current into the batteries? Can I keep the same set up (with larger cables) and check water level more often or does something else happen to them that I can't control?

[Almot]

Kayteg1 wrote:
Other issue will be allowable charging current for the batteries.
Rule of thumb would be about 20 amp, so 75amp might be killing current.

Here is the rule: 0.2C for flooded = 0.2*225 = 45A.
It "could" accept a higher current when hungry, though not a good idea.
75A is a bit too much.

[MEXICOWANDERER]

http://www.skycraftsurplus.com/14awgdlo2kvblack-1-1-1-1-1-1.aspx

Sixty feet minimum purchase.

Use the "excess" to correct the laughingstock wiring from the alternator to the charge divider solenoid, then from there to the house batteries. Spud a length from batteries to chassis negative.

This takes care of ALL your OEM garbage grade wiring. You won't believe how much FASTER your batteries will charge from the converter OR the alternator.

WAIT! Someone out there is already screaming "Too big of wire between alternator and chassis and house batteries!" Please give me a few years to go back and "correct" the hundred plus rigs I have successfully done this on.

[westend]

Can I use the frame as the negative path in place of the battery to charger cable? Is this considered beneficial/safe/recommended/worth the effort ... etc, etc.?

Yes, you can and the frame will have less resistance in most cases. The downside is that you'll also have to establish a ground to frame from the battery. Also, you'll now have two additional ground connections. For most, that isn't an issue but for some purists it is additional failure point.

I'd suggest to just replace what you have with 4 ga welding cable and call it a day. I can buy good 4 ga for around $1/ft. I do my own terminations. If you don't crimp cables, you could pull the 6 ga, measure the lengths, and have Genuinedealz.com make new cables with terminations already prepared.

[johnm1]

Thank you - I wasn't sure what you were referencing. I think (hope) I'm starting to understand this a bit more.

Can I use the frame as the negative path in place of the battery to charger cable? Is this considered beneficial/safe/recommended/worth the effort ... etc, etc.? If yes, I could easily take the negative 6awg wire and pair it to the existing 6awg positive and get some short "large" gauge jumper wires to go from battery to frame and frame to charger. Not as good as the 00awg but it's closer than what I've got right now.

About moving the charger/converter. I'm sure I could but ... I'd have to get/make an enclosure for it since the circuits are exposed (it's a drop in for the WFCO unit) and I'd need to run a 120V wire & outlet to the front, where there is no 120V anything. In the long run, I think it'd be easier to run new battery cables ... my opinion.

[grizzzman]

grizzzman wrote:

johnm1 wrote:
grizzzman - would you please explain as I don't understand what you mean by "the numbers don't lie".

Sure look at my earlier post. I crunched the voltage drop number's for you. Have a look.

[grizzzman]

johnm1 wrote:
grizzzman - would you please explain as I don't understand what you mean by "the numbers don't lie".

Sure look at my earlier post. I crunched the voltage drop number's for you. Have a look.

[RJsfishin]

Yes, the #s do lie when you have a 75 amp charger that will never see more than 45 amps.

[johnm1]

grizzzman - would you please explain as I don't understand what you mean by "the numbers don't lie".

[grizzzman]

johnm1 wrote:
Ok, a lot of the ideas and thoughts never occurred to me. Like I didn't know I could just add another run of 6 gauge wire. I think that'd be fairly easy to do. Can I run the battery neg to the frame with larger (or doubled) wire and use that as the ground to the charger? Would I gain anything by doing that?

I forgot to add our typical camping modes. It's a mix of dry camping (can't really call it boondocking since we're in a campground with amenities - just no power to hook into) and campgrounds with power. We can be at either for a short 2 day weekend but up to 2+ weeks at a time (this is where the gen comes into play). Lots of shade so solar isn't really viable, but I'm going to really pay attention this year at the available sun spots for a portable panel setup. We are very frugal with power usage. All LED lights, have a portable propane heater to take the chill off before bed and after waking up (not while sleeping). And, when we get home, the RV gets plugged into a 30A outlet and charged until we go out again.

Lastly, I went with the 75A charger because, that's what Randy (at BestConvertor) recommended based upon what I told him which includes that I may add 2 more 6v gc batteries (for a total of 4).

Thanks all!

The numbers don't lie johnm1

[grizzzman]

rjxj wrote:
I have about the same distance to my batteries and went to 4 g wire. I'm not sure you could get 2 g in the lug but they do make adapters. You say "get the most efficiency" so you probably mean that you are off the cord a lot boondocking? If you are plugged in a lot and there is a little more voltage drop than you might like it wont matter over time. If running a generator only than voltage drop is very important. Did you do a voltage check at the converter terminals and at the battery terminals.

This unit is a TH , It is on the "cord" between trips. But he boondocks 3-4 days at a time but also goes for longer trips (this is when his need for efficient charging comes into play). So any voltage drop will slow charging.

[johnm1]

Ok, a lot of the ideas and thoughts never occurred to me. Like I didn't know I could just add another run of 6 gauge wire. I think that'd be fairly easy to do. Can I run the battery neg to the frame with larger (or doubled) wire and use that as the ground to the charger? Would I gain anything by doing that?

I forgot to add our typical camping modes. It's a mix of dry camping (can't really call it boondocking since we're in a campground with amenities - just no power to hook into) and campgrounds with power. We can be at either for a short 2 day weekend but up to 2+ weeks at a time (this is where the gen comes into play). Lots of shade so solar isn't really viable, but I'm going to really pay attention this year at the available sun spots for a portable panel setup. We are very frugal with power usage. All LED lights, have a portable propane heater to take the chill off before bed and after waking up (not while sleeping). And, when we get home, the RV gets plugged into a 30A outlet and charged until we go out again.

Lastly, I went with the 75A charger because, that's what Randy (at BestConvertor) recommended based upon what I told him which includes that I may add 2 more 6v gc batteries (for a total of 4).

Thanks all!

[azrving]

I have about the same distance to my batteries and went to 4 g wire. I'm not sure you could get 2 g in the lug but they do make adapters. You say "get the most efficiency" so you probably mean that you are off the cord a lot boondocking? If you are plugged in a lot and there is a little more voltage drop than you might like it wont matter over time. If running a generator only than voltage drop is very important. Did you do a voltage check at the converter terminals and at the battery terminals.

[Golden_HVAC]

You could add a second wire for much less money, just run a second #8 or #6 wire next to the wires already going to the battery. Then each #6 wire would carry a maximum of only about 30 amps, and you cold barely measure the voltage drop.

Your 75 amp charger probably will never put out 75 amps. As soon as the batteries see 14.4 volts, the charge rate starts to fall off, and you will see it is 45 amps within 15 minutes and 35 amps after the first hour or so. This is what I see with my 4 golf cart batteries, and my Trace M1512 inverter/charger. IT is rated at 70 amps charging, and the wire size is 000 to accommodate the 150 amp load the inverter can put on the batteries.

I actually will usually set my charger to max charge rate of 60% (42 amps) so the battery will not get warm during charging.

Have fun camping!

Fred.

[grizzzman]

Kayteg1 wrote:
What Instructor is quoting apply to household wiring, where there is not much heat allowed.
You might be surprised that on lot of cars starter wire is #6 and carries 400 amp. But then starter is short duty and some heat on the engine is not a problem.
When running #3 wire is always an option, I wold just touch the wires and connectors during charging. Or better yet, get one of those infra-red thermometers. By buying one with laser pointer you will have new toy for the cat as well .

True..... But when boondocking and gen charging any voltage drop (wasted as heat) slows down the ability to charge effectively, and fools the already anemic converter into dropping the voltage to soon.