How many amps going to batteries on shore power?

[phann]

At some point in the near future I will upgrade the stock converter to a three stage model. Meanwhile, I know my current converter delivers about 13.7 volts to the batteries while on shore power, but how many amps are being delivered? Im hoping to estimate how many hours I can safely leave the battery disconnect in the "Use" position while on shore power, based on the batteries current state of discharge. Also, do the amps delivered to the battery via the converte differ according to what the shore power connection Im using (i.e.. 30, 50, 20)?

Thanks for any info in advance.

[alano]

It's very difficult to say what the charging current will be as a function of the discharge state of your batteries. The stock converter acts like a constant voltage source and can deliver up to 55 A. If more than 55 A is required, the output of the converter will fold-back such that the current does not exceed 55 A.

The answer to your other question is no, the converter can deliver 55 A no mater what shore power connection you have. For example, 20 A service can supply 120 V * 20 A = 2500 W, which is more than sufficient to deliver the output power of 13.7 V * 55 A = 750 W.

[AnnArborBob]

How long you can stay disconnected from shore power (using the disconnect switch) is difficult to predict since that is entirely dependent on what 12v load you are putting on the batteries. If you are an energy hog (e.g., furnace running a lot, inverter on, watching TV, lights, etc..) you could deplete a good set of batteries overnight. With very careful energy management, you could go four or five days (assuming no power input from shore, solar or generator.) If you are concerned, try it in your driveway and see how long your batteries last under various scenarios.

As a very broad brush, wild ass guess, "rule of thumb" place to start, I would suggest starting out by being connected to shore power for one to two hours per day and see if that gets you back to 100% charge each day after typical usage and adjust accordingly. I think that the stock Airstreram charger will provide about 50 AH towards a charge, with that the math is easy.

[markdoane]

Hmmm.

Two good answers. Stick a fork in it. This thread is FINISHED!

[mpsgolf]

I had similar questions about my Parallax converter charger so I contacted Ed the manufacturer.

The model in my 28' is called a constant voltage, variable current charger. I tried to copy the curve he sent me but can't with my iPad. I'll explain it as best I can.

It is for a group 27 battery with 50% discharge. The voltage is mostly constant at 13.8. When charging first starts and amps are high it is about 13.5 but within 1-2 hours it is at 13.8. As far as Amps, when the battery first starts to charge from 50% amps are high at 45. They drop rapidly to about 25A at an hour and 15A at 2 hours. At three hours it is between 2-3A, and continues to drop to below 1A.

Hope this helps. Sorry to draw with words what should be a graph.

[tjdonahoe]

That's good to know,looks good

[Protagonist]

Originally Posted by mpsgolf

As far as Amps, when the battery first starts to charge from 50% amps are high at 45.

Neat trick if you're plugged into 15-amp or even 30-amp shore power… Where do the extra amps come from?

[n2916s]

An output of 45 amps at 12vdc is only 540 watts

The input of 30 amps @ 120vac is 3600 watts

Not a problem

[markdoane]

Originally Posted by Protagonist

Neat trick if you're plugged into 15-amp or even 30-amp shore power… Where do the extra amps come from?

Should've stopped at post #4. It was perfect up until then.

[Protagonist]

Originally Posted by markdoane

Should've stopped at post #4. It was perfect up until then.

Still perfect. There are no dumb questions, only dumb people asking questions. Sometimes I'm dumb.

[n2916s]

As I get older, I have more of those less insightful moments. Been there, done that, forgot where I put the t-shirt...

[AnnArborBob]

Originally Posted by Protagonist

Still perfect. There are no dumb questions, only dumb people asking questions. Sometimes I'm dumb.

Not to worry. Lots of people forget to make the "mental" amp conversion when switching from DC to AC.

But I agree that this thread has run it's course. Move along, nothing to see here...

[ROBERT CROSS]

I've forgotten more than I'm currently aware of...

Bob

[idroba]

So now we are going to let self appointed thread censors decide when a thread has had enough, or "correct" answers and tell us to "put a fork in it"?

I don't agree with that method of operation.

[Protagonist]

Originally Posted by idroba

So now we are going to let self appointed thread censors decide when a thread has had enough, or "correct" answers and tell us to "put a fork in it"?

No thread is finished unless the moderators lock it so no one else can post. Just yesterday— or maybe the day before; all my days run together— someone performed some Marie Laveau voodoo to zombify a formerly-dead thread from eleven years ago. That's some serious thread necromancy!

[markdoane]

Originally Posted by idroba

So now we are going to let self appointed thread censors decide when a thread has had enough, or "correct" answers and tell us to "put a fork in it"?

I don't agree with that method of operation.

Don't take yourself so seriously. It was meant as a compliment to the first two respondents, who posted excellent and complete responses to the original post. Nothing more.

[Jammer]

Originally Posted by phann

At some point in the near future I will upgrade the stock converter to a three stage model. Meanwhile, I know my current converter delivers about 13.7 volts to the batteries while on shore power, but how many amps are being delivered? Im hoping to estimate how many hours I can safely leave the battery disconnect in the "Use" position while on shore power, based on the batteries current state of discharge. Also, do the amps delivered to the battery via the converte differ according to what the shore power connection Im using (i.e.. 30, 50, 20)?

Thanks for any info in advance.

Converters are best understood as a constant-voltage supply. They will deliver a smaller and smaller current to the battery as the battery charges. Overcharging is typically not a problem except in hot weather, and even then the batteries will be fine if kept watered. The real advantage of 3-stage converters is that they charge the battery more quickly. With new but fully discharged batteries the charging current may reach 30 or 40 amps but willl taper off to around 1-2 amps over a 48 hour period.