Charging Battery with Tow Vehicle

[chiefvintage]

I have a very small Whirlpool 3.1 cu. ft. fridge with freezer section, rated at 47W @120 VAC, not sure what the peak draw is yet when compressor is running, need to do some testing; if needed I’ll go the DC/DC route with an inverter.


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[chiefvintage]

I have a very small Whirlpool 3.1 cu. ft. fridge with freezer section, rated at 47W @120 VAC, not sure what the peak draw is yet when compressor is running, need to do some testing; if needed I’ll go the DC/DC route with an inverter.


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[RJ Howell]

I have a very small Whirlpool 3.1 cu. ft. fridge with freezer section, rated at 47W @120 VAC, not sure what the peak draw is yet when compressor is running, need to do some testing; if needed I’ll go the DC/DC route with an inverter.


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Worth doing! I do believe as the new DC frig's have gone, you will see better performance. . t took me some time to switch (and a bunch of folks sayin' research).

[Socal Tom]

For what it’s worth. I charge through the 7 pin connector. My alternator makes 200 amps, I’m using a factory wiring harness and I have a 10ga wire running to the battery. My trailer has a fancy charge meter that can tell me how much charge passes through it, and I’ve used it to monitor how much charging I get while driving. The answer is not much. It does charge, but I would count on it do do much more than maintain a charge. I suspect that because it takes 20 or more feet of wire to get to the battery it would take welding leads to carry the amperage that far. It’s been a while since I did the test, but I’d guess it was less than 5 amp per hour on a battery that was at 50% capacity.

[John61CT]

amps per hour is incorrect

Amps are a flow rate, instantaneous measure.

Ah is static, quantity of energy

so 5Ah per hour makes sense.

Which of course happens to work out to an average of 5A current rate.

Putting in more robust wiring would allow refilling even a large bank in a day's driving.

At a 5A rate you only get 35-40Ah replaced.

But that might be fine for most.

Just verify you aren't sizing so small that there is a fire risk.

[Socal Tom]

amps per hour is incorrect

Amps are a flow rate, instantaneous measure.

Ah is static, quantity of energy

so 5Ah per hour makes sense.

Which of course happens to work out to an average of 5A current rate.

Putting in more robust wiring would allow refilling even a large bank in a day's driving.

At a 5A rate you only get 35-40Ah replaced.

But that might be fine for most.

Just verify you aren't sizing so small that there is a fire risk.

I always get in trouble talking about charging on here. In reality, I looked at the watt hours that were reported by my fancy meter between leaving camp and arriving home ( about a 3 hour trip). It was last year, so I don't remember exact numbers, but my aging memory recalls that it went up about 200 watt hours (the equivalent of about 5amp hours, per hour of travel , total of about 15 Ah which is around 180 to 200watt hours).
Sorry if I confused you.

[featherliteCT1]

John61CT,

I am always educated by and appreciate your posts.

The instructions to my Trimetric meter say:

“As the battery discharges, the TriMetric “amp hours from full” gradually go negative at a rate depending on the number of amps, and go positive when charging. For example if the batteries are discharging with “amps” = minus 10.0, the "amp-hours from full" display gradually decreases by exactly 10.0 for every hour that goes by.

… you don't get as many amp-hours out of the battery as you put in, so that the TriMetric "amp-hours from full" display will give a reading of amp-hours which reasonably closely estimates how many amp hours have been removed.”

Are the above instructions an example of incorrect terminology?