etrailer article

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etrailer article

Postby John61CT » Fri Apr 09, 2021 9:44 am

for critique and discussion

Targeted for "dump trailers" but same principles apply for House bank deep cycling.

Obviously LFP batteries are very different from lead ones, so probably best to save those for later.


_______
How to Charge a Trailer Battery

https://www.etrailer.com/faq-how-to-cha ... ttery.aspx
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Re: etrailer article

Postby Tom&Shelly » Fri Apr 09, 2021 1:12 pm

They don't mention how much energy you need per dump (unless I missed that when skimming the article). Bet you could run a teardrop for a few days to a week on that much energy!

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Re: etrailer article

Postby featherliteCT1 » Fri Apr 09, 2021 7:47 pm

They are right on about the inability of a standard 7 way plug to charge a depleted battery.

The typical dump trailer battery is not a deep cycle battery so I would think draining a “starter” battery flat or near flat would quickly destroy the battery. I think the typical battery is probably something like a 1000 cold cranking amp heavy duty farm equipment battery.

I do not think that the depicted AC to DC “starter” battery charger (or any other off the retail shelf charger for that matter) would properly charge a deep cycle battery.
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Re: etrailer article

Postby Tom&Shelly » Fri Apr 09, 2021 9:27 pm

featherliteCT1 wrote:They are right on about the inability of a standard 7 way plug to charge a depleted battery.


With all due respect, I haven't heard anyone on the forum present a credible case for that. Lot's of incorrect information (mis-stated units, wildly over-estimated voltage drops, etc.) though...

No offense intended, but just saying...

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Re: etrailer article

Postby John61CT » Sat Apr 10, 2021 6:08 am

Yes just like running a winch or for any high-amp load like water heating, or an all-electric galley

it would be false economy to use anything but a battery from a known good top notch maker designed for deep cycling.

Of course how many overnights needed per year has a huge impact, calendar life vs cycle lifespan.

And a high-CAR chemistry or big bank pulling 120A charge current will be completely different from a small bank's 30A one.
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Re: etrailer article

Postby Socal Tom » Sat Apr 10, 2021 6:46 am

Tom&Shelly wrote:
featherliteCT1 wrote:They are right on about the inability of a standard 7 way plug to charge a depleted battery.


With all due respect, I haven't heard anyone on the forum present a credible case for that. Lot's of incorrect information (mis-stated units, wildly over-estimated voltage drops, etc.) though...

No offense intended, but just saying...

Tom

Before I permanently installed my solar panels I tracked the charging I got from the 7 pin plug on the drive home. It wasn’t a ton, granted the fridge was also on, but IIRC it was around 5 amps per hour, so maybe 150 watts over the 3 hour drive. For a 100 AH battery it’s not enough to charge a 50% depleted battery, if your just using a small 50;AH battery it might be ok.
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Re: etrailer article

Postby Tom&Shelly » Sat Apr 10, 2021 7:24 am

Socal Tom wrote:
Tom&Shelly wrote:
featherliteCT1 wrote:They are right on about the inability of a standard 7 way plug to charge a depleted battery.


With all due respect, I haven't heard anyone on the forum present a credible case for that. Lot's of incorrect information (mis-stated units, wildly over-estimated voltage drops, etc.) though...

No offense intended, but just saying...

Tom

Before I permanently installed my solar panels I tracked the charging I got from the 7 pin plug on the drive home. It wasn’t a ton, granted the fridge was also on, but IIRC it was around 5 amps per hour, so maybe 150 watts over the 3 hour drive. For a 100 AH battery it’s not enough to charge a 50% depleted battery, if your just using a small 50;AH battery it might be ok.


OK Tom, so now you're talking about how long it takes to charge, not whether it can be done. But the system was charging, so with a long enough drive, the battery would be fully charged. (It would take about 10 hours at 5 amps for a 50% depleted 100 AH battery. Of course, the math isn't really quite that simple, even though I did the calculation that way before, for the sake of a quick estimate--the current drops as the battery becomes charged--I'm expecting a bit more than 5 amps from our TV when the battery is way down, but I haven't tried it yet.)

What bothers me are the blanket statements, on this forum and others, that 7 pin charging simply doesn't work. It does.

If you'd replaced the 7 pin charging system with a separate, larger wire and Anderson connectors, or whatever, all you would gain back would be the loss through the 10 gauge wire over about 20 feet. That's about a quarter volt at 5 amps, or 1.25 watts of loss through the wire.

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Re: etrailer article

Postby featherliteCT1 » Sat Apr 10, 2021 8:22 am

No offense taken. :) :)

Thanks for your comments. It was a mistake for me to say ”They are right on about the inability of a standard 7 way plug to charge a depleted battery.”

My mistake was to over generalize. I should have said that a 7 way plug will not meet my particular charging needs.

Below is the explanation of why the 7 way connector on my truck will not “adequately” charge my 225 amp hour lead acid, deep cycle battery, located in my trailer. I am only going to explain why my particular 7 way plug will not work for me.

A while back, I researched the pros and cons of using the power lead on my 7 way connector to charge my battery.

I determined I could not practically use my 7 way plug for two reasons:

1. The OEM wire would not carry enough current for my needs, and

2. After my starter battery becomes fully charged after a few minutes, my “smart” alternator will not charge the deep cycle battery.

Note: I think, but cannot remember without taking the time to research this forum, that flboy did not have this shut down problem with his truck. Maybe he will chime in.

First, the power wire to my 7 way plug is 12AWG. 12AWG is rated for 40 amps. My fuse box also has a 40 amp fuse.

My truck is 20 feet long, so I assumed that the power wire was 20 feet long. Actually, I think the wire is longer due to winding around to get from the front to the rear of my truck. It is another 10 feet from the 7 way connector to the deep cycle battery in the front of my trailer.

So, the 12AWG wire run is about 30 total feet.

The Renogy wire size calculator I use says that 14 volts, at 30 feet of 12 AWG wire, with a 3% voltage drop, will carry 3 amp hours (5 amps if the run is only 20 feet).

When my battery is discharged about 20% = down about 44 amps, my solar charger inputs about 25 amps at 14.3 volts, until the battery is about 90% charged at which time the battery will only accept about 6 amps at 14.6 volts, and then the amp hours continue to decrease as the battery gets full. When the battery is full, my solar charger floats the battery at 13.2 volts. So, it takes many more hours to top off the battery from 90% to 100% full using my solar charger.

If I was using 12AWG wire to input 3amp hours into my battery, it would take about 7 hours to push 21 amps into the battery, at which time the battery would only be 90% full. I can only guess how long it would take to top off the battery … perhaps seven more hours? (I really do not know).

Second, my batteries will not charge until at least 14.1 volts are pushed into the battery. My battery will not charge at less voltage.

My truck’s “smart” alternator will charge both my starter battery and my deep cycle battery at about 14.4 volts, until the starter battery is full (which only takes a few minutes after starting the truck because after starting the truck, the starter battery is only slightly discharged), then the voltage drops down to around 13.3 float volts. So, the alternator stops charging both batteries after the same short time.

So, I installed a DC to DC “smart” charger rated at 20 amp hours with 2 AWG wire to charge my deep cycle battery.

Conclusions:

1. A 7 way plug with standard wiring will charge a battery; but the number of hours to charge the battery depends on wire size and wire length. This is a matter of simple mathematics.

2. Some alternators will shut down charging early.

Note 1: My truck alternator is rated at 165 amps but can only safely out put a continuous 50% of rated capacity, otherwise the diodes in alternator will overheat and fail. After considering all OEM potential loads from my truck, my 165 amp alternator only has about 20 spare amps available to charge my deep cycle battery (I determined this by bench testing using my hand held amp meter).

Note 2: I would think that if someone were using a 7 way plug to charge the deep cycle battery without a separate “smart” charger, the battery would be charged with “unregulated” voltage which, in the long run, would damage the battery.
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Re: etrailer article

Postby saltydawg » Sat Apr 10, 2021 8:36 am

There are a couple of issues with trying to charge thru the 7 pin. Yes voltage drop is a problem, but more of a totally charging the battery. We know a fully charged lead acid should be at 12.7 when fully charged but the amps drop off the volt drop is partially based on amps so the voltage drop should be less as it gets closer to full. So its more of short drives may not fully charge it.

The other issues can be the alt in the car ramping down the voltage as it sees the starting battery charged it lowers the voltage. This is more a new smarter alt ( ecu controlled ) problem.

In a dump trailer it should be a starting battery as the pump can draw lots of amps, not as much as a starter but more than a couple of lights and a fan. And its shorter duration, like run for 1 min not 12 hours.

I would feel fine charging a dump trailer battery thru the 7 pin, same I feel fine charging my brake battery thru the 7 pin.

When we are talking about tear drops we also run in to different battery types, ie agm has different charging requirements than FLA.

Lastly you should definitely not try to charge a lifepo4 battery thru the 7 pin with out a dc dc charger. Its a good way to kill your alt or if you dont have a fuse to melt a wire to the 7 pin.
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Re: etrailer article

Postby Socal Tom » Sat Apr 10, 2021 9:49 am

Tom&Shelly wrote:
Socal Tom wrote:
Tom&Shelly wrote:
featherliteCT1 wrote:They are right on about the inability of a standard 7 way plug to charge a depleted battery.


With all due respect, I haven't heard anyone on the forum present a credible case for that. Lot's of incorrect information (mis-stated units, wildly over-estimated voltage drops, etc.) though...

No offense intended, but just saying...

Tom

Before I permanently installed my solar panels I tracked the charging I got from the 7 pin plug on the drive home. It wasn’t a ton, granted the fridge was also on, but IIRC it was around 5 amps per hour, so maybe 150 watts over the 3 hour drive. For a 100 AH battery it’s not enough to charge a 50% depleted battery, if your just using a small 50;AH battery it might be ok.


OK Tom, so now you're talking about how long it takes to charge, not whether it can be done. But the system was charging, so with a long enough drive, the battery would be fully charged. (It would take about 10 hours at 5 amps for a 50% depleted 100 AH battery. Of course, the math isn't really quite that simple, even though I did the calculation that way before, for the sake of a quick estimate--the current drops as the battery becomes charged--I'm expecting a bit more than 5 amps from our TV when the battery is way down, but I haven't tried it yet.)

What bothers me are the blanket statements, on this forum and others, that 7 pin charging simply doesn't work. It does.

If you'd replaced the 7 pin charging system with a separate, larger wire and Anderson connectors, or whatever, all you would gain back would be the loss through the 10 gauge wire over about 20 feet. That's about a quarter volt at 5 amps, or 1.25 watts of loss through the wire.

Tom

Honestly, my take on all this is that, if your TD battery can't me maintained with the 7 pin, the back up option is to hook some jumper cables between your TV and the TD battery and charge your house battery that way for a while. As long as your alternator puts out good amperage at idle, then you can probably get by that way.
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Re: etrailer article

Postby Chisomisac » Wed May 24, 2023 8:36 am

Understanding the fundamentals and best practices is key when it comes to optimizing battery performance.

You mentioned that LFP (Lithium Iron Phosphate) batteries are quite different from lead batteries, and it's wise to dive into that topic later. That's a smart approach, as LFP batteries have their own unique characteristics and considerations that deserve separate attention.

If you're looking for some assistance in crafting high-quality content, you might want to check out writersperhour.com. They offer professional writing services that can help you create engaging and informative articles.

Keep up the good work, and best of luck with your house bank deep cycling endeavors!
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