Trying to understand recharging the batteries

[HDRider]

I explained my lack of understand of electricity in this earlier thread.  Long story short, I am an e-dummy.

But yet, I persevere.  Using ChatAI

 

Q - How long would it take for 400 watt solar panels to recharge 390 amp hour battery

A - To calculate how long it would take for a 400-watt solar panel to recharge a 390-ampere hour (Ah) battery, we need to take into account a few factors, such as the efficiency of the solar panel, the weather conditions, and the charging controller used.

Assuming a charging efficiency of around 80%, which is a reasonable estimate for most solar panels, we can calculate the charging time using the following formula:

Charging time = Battery capacity (Ah) / (Solar panel power (W) x Charging efficiency)

Plugging in the values, we get:

Charging time = 390 Ah / (400 W x 0.8) = 1.22 hours

Therefore, it would take approximately 1.22 hours, or 73 minutes, for a 400-watt solar panel to fully recharge a 390 Ah battery, assuming optimal conditions and a charging efficiency of 80%. However, in real-world situations, the actual charging time may vary depending on factors such as the weather, the angle and orientation of the solar panel, and the state of charge of the battery.

 

[HDRider]

Q - How long would it take a 2000 watt generator to recharge 390 amp hour battery?

A - The time it would take a 2000 watt generator to recharge a 390 ampere hour (Ah) battery depends on several factors, such as the charging efficiency, the condition of the battery, and the charging rate.

Assuming a charging efficiency of around 80%, which is a reasonable estimate for most lead-acid batteries, we can calculate the charging time using the following formula:

Charging time = Battery capacity (Ah) / (Charging rate (A) x Charging efficiency)

To determine the charging rate, we need to convert the generator's wattage to amperage, using the formula:

Charging rate (A) = Charging power (W) / Charging voltage (V)

For a typical 12-volt lead-acid battery, the charging voltage is around 14.4 volts. Thus, the charging rate of a 2000 watt generator would be:

Charging rate (A) = 2000 W / 14.4 V = 138.9 A

Plugging in the values, we get:

Charging time = 390 Ah / (138.9 A x 0.8) = 3.5 hours

Therefore, it would take approximately 3.5 hours, or 210 minutes, for a 2000 watt generator to fully recharge a 390 Ah battery, assuming optimal conditions and a charging efficiency of 80%. However, in real-world situations, the actual charging time may vary depending on factors such as the temperature, the state of charge of the battery, and the type of battery chemistry.

[HDRider]

Why does it take a 2,000 watt generator so much longer to recharge the batteries than 400 watt of solar panels?

[CnC]

Because their answer is not "real world?"  🤪

Charlie.

[Frank C]

2 hours ago, HDRider said:

Why does it take a 2,000 watt generator so much longer to recharge the batteries than 400 watt of solar panels?

The first example has an error in the charge time formula.  It’s using watts instead of converting that to amps by dividing by the panel output voltage.  The second example does that.  Compare the two charge time formulas.   An example of why AI is not to be trusted.  It very confidently gave a wrong answer.  And in the real world there are other factors as well.  The 390Ah rating of the batteries is a discharge capacity rating.   Charging is different in that there are different phases of the charge process cycle with different voltage and current values depending on how deeply the battery is discharged.  The battery charger also has a maximum limit on the battery charging current as well.  A generator with 2000 watts output will charge the batteries faster than a 400 watt solar panel, but it won’t be 5 times faster.  

[Rivernerd]

3 minutes ago, CnC said:

Because their answer is not "real world?"  

Spot on.  In my "real world" experience, a generator recharges our 390 Ah batteries much faster than the solar panels, even when parked in direct sunlight at mid-day.  

[CnC]

Seriously, I'm not an "expert."  But at first glance it appears they are mixing watts and amps.

In our real world, we use about 120 amps a day and on most sunny days our 340 watts of panels keeps up with us.  That's with frig, furnance, water on LP and minimal use of microwave, coffee pot and 120 TV for movies at night.

Charlie.

[ScubaRx]

2 hours ago, HDRider said:

Why does it take a 2,000 watt generator so much longer to recharge the batteries than 400 watt of solar panels?

Because the generator is only supplying power to run your onboard charger which may be as low as 45 amps output. 

[Steph and Dud B]

41 minutes ago, CnC said:

on most sunny days our 340 watts of panels keeps up with us

True that. I have trouble getting a decent discharge on our 640 AH lithiums to exercise them. The solar keeps topping them off. And we only have 340 watts of solar. 

[snakeriveridaho]

5 minutes ago, Steph and Dud B said:

True that. I have trouble getting a decent discharge on our 640 AH lithiums to exercise them. The solar keeps topping them off. And we only have 340 watts of solar. 

That has been our experience so far also. The solar panels have kept our batteries topped off, even when we have used our convection oven for some baking.  Although, we haven't used the air conditioner yet. 

[HDRider]

1 hour ago, ScubaRx said:

Because the generator is only supplying power to run your onboard charger which may be as low as 45 amps output. 

Do the solar panels use a different charger, something other than my "onboard charger"?

 

[Fritz]

2 hours ago, Steph and Dud B said:

I have trouble getting a decent discharge on our 640 AH lithiums to exercise them. The solar keeps topping them off. And we only have 340 watts of solar. 

To get a decent discharge I think it's necessary to turn off the solar controller (the switch located in the storage area above the streetside bed).  This prevents incidental recharge.

[Steph and Dud B]

1 hour ago, HDRider said:

Do the solar panels use a different charger, something other than my "onboard charger"?

Yes, they have a separate charge controller.

[SeaDawg]

In our experience of 15 years with the ollie, using solar as our primary choice of charging, but using a genset when we have a string of crappy days, I'll offer this:

We use the generator  (in our case, 2008 Elite I with only two agm 105 ah 12v batteries) in the morning hours, when most depleted, so the genset is charging in "boost"  or "bulk"mode, most efficient for the gas running the generator. 

Once the on-board controller throttles back to "absorption", and definitely if we take a walk and its in "float", if weather is halfway decent, we shut down the generator  and let the silent and efficient solar panels finish the job. The next modes step down, and solar works fine. Actually,  better than a genset, at low amp charging.

(Side note: if we have to charge a tool battery or something else, we'll do that while the generator is running.) 

This has worked extremely well for us. 

A few notes: we have no microwave.  We have no inverter. We camp, not rv. We do have an electric dc fridge. But, the principles would be the same. 

If you use a lot more amps (microwave, toaster oven,   electric coffee pot, etc) you may need to run a generator at night, for a bit,  as well, even with lithium.

The cool thing about lithium batteries is that they actually  "like" the middle charge range. Agms want to be topped off every day. Lithium doesn't need that.

You'll find your sweet spots, whichever batteries you have. 

With agms, I try to not go below   +/- 75% charge, as I  know that extends the life of my (arguably expensive) batteries. With lithium, I'd be ok going down to ten or 15 per cent , but I'd try to keep them in the mid range (30 to 85)

 

[CnC]

On 4/26/2023 at 1:40 PM, SeaDawg said:

A few notes: we have no microwave.  We have no inverter.

And I'd have no wife 😜

Charlie.

[SeaDawg]

7 hours ago, CnC said:

And I'd have no wife 😜

Charlie.

😁I am the wife. I'd be happy to give lessons on a microwave-free life, but many are disinterested. I rarely use my home microwave, so it is easy for me.

Back in 2008, my husband really wanted the convection microwave, (I didn't),  so we got it. It eventually died, probably from lack of use... Since we almost never h ad power, the microwave was useless. We now enjoy a little pantry cabinet created from the microwave cabinet. 

Everyone's needs and wants are different.  Our trailers can accommodate them, with whatever accessories buy. Our lifestyles,  and camping styles, are different,  but we can all work together on solutions. 

 

[HDRider]

On 4/26/2023 at 1:51 PM, Steph and Dud B said:

Yes, they have a separate charge controller.

How could the generator go through the same (or maybe an altogether different) charge controller as the solar panels?

 

I would like to see the generator charge the batteries as fast as it could.  It is my understanding that lithium can take a very fast charge.

[Steph and Dud B]

The generator feeds the converter through the shore line. The converter converts the 120 VAC to DC to charge the batteries based on the settings in the converter.

The solar panels also provide DC power to the batteries through their controller. The two systems supplement each other. As the battery level of charge rises they lower their charging current until the batteries are charged.

The final say is the Battery Management Software in the batteries themselves.  If they aren't happy with the amount or type of charge they are receiving from those 2 systems they shut down charging.

[Steph and Dud B]

6 hours ago, HDRider said:

I would like to see the generator charge the batteries as fast as it could. 

The batteries can actually take a charge faster than some small generators can provide. That's why you may need to adjust your converter settings to avoid overloading your generator. Either way, they charge very quickly on a generator or shore power.

[ScubaRx]

6 hours ago, HDRider said:

How could the generator go through the same (or maybe an altogether different) charge controller as the solar panels?

 

I would like to see the generator charge the batteries as fast as it could.  It is my understanding that lithium can take a very fast charge.

The rate of charge going into the battery is dependent on the amps available. The best that 340 watts of solar can do is about 25 amps.

The onboard charger is 45-150 amps depending on the type you have. 
 

 

[ScubaRx]

7 minutes ago, Steph and Dud B said:

The final say is the Battery Management Software in the batteries themselves.  If they aren't happy with the amount or type of charge they are receiving from those 2 systems they shut down charging.

This is applicable to lithium batteries only. 

[HDRider]

19 hours ago, ScubaRx said:

The onboard charger is 45-150 amps depending on the type you have. 

Do you know the capabilities of the onboard charger that comes with the 2023 Lithium Pro package?

[Galway Girl]

I believe you have the 3000 Watt Xantrex Pro Charger with that package.

The OUTPUT Current for charging is user selectable from 5 to 150 Amps.
If you are running on Shore Power/30A connection then this setting is usually set for 150Amps.
If you are running connected to a generator (not shore power) then what it delivers will depend upon the power output available from the generator. 

 

If

[johnwen]

1 hour ago, Galway Girl said:

I believe you have the 3000 Watt Xantrex Pro Charger with that package.

The OUTPUT Current for charging is user selectable from 5 to 150 Amps.
If you are running on Shore Power/30A connection then this setting is usually set for 150Amps.
If you are running connected to a generator (not shore power) then what it delivers will depend upon the power output available from the generator. 

 

If

Galway Girl,

Thanks for your outfitter's guide.  I've ordered several items from it :)

John

[MAX Burner]

On 4/28/2023 at 11:30 PM, SeaDawg said:

We now enjoy a little pantry cabinet created from the microwave cabinet. 

Does anyone out in Ollie-World want to buy a microwave???