Electrical Draw Calculations

[PNWorBUST72]

Ok I think I get it now.

My individual device usage math was ok but how I used it to size my batteries was incorrect mostly?

So since I have to go through the inverter, because I am off shore or genny power, I need to pull 80amp-hours for very hour I use the 1000 watt device.

So my 240AH sized battery bank could run this for something more like 2hrs instead of 28hrs.

So is boondocking more like camping in the RV then living at an RV park cause how else do people boondock unless they have 4000ah battery banks? Is boondocking even a viable option with no solar or genny perhaps?

[JDOnTheGo]

Originally Posted by PNWorBUST72

Ok I think I get it now.

My individual device usage math was ok but how I used it to size my batteries was incorrect mostly?

So since I have to go through the inverter, because I am off shore or genny power, I need to pull 80amp-hours for very hour I use the 1000 watt device.

So my 240AH sized battery bank could run this for something more like 2hrs instead of 28hrs.

Yes!!! Exactly right!

Originally Posted by PNWorBUST72

So is boondocking more like camping in the RV then living at an RV park cause how else do people boondock unless they have 4000ah battery banks? Is boondocking even a viable option with no solar or genny perhaps?

That is a debate that every person has with themselves and their equipment. I have a 10,000 ah battery bank and 2,000 watts of solar to feed my power hungry coach. I made the CHOICE to go all electric (and invest heavily in solar and lithium batteries). A more typical approach (in RV's) is a combined battery and propane system. Using propane for stove top, oven, and refrigeration (absorption fridge) massively reduces your need for electricity. I lived in an RV for a couple years with this setup and 600 watts solar and there was very little difference between "how" I lived when boondocking vs on shore power (mostly boiled down to not running the clothes washer/dryer when boondocking). I'm living entirely off electricity now and again, very little difference between boondocking and with shore power. However; if it is cloudy for several days in a row, I have to conserve power (or I could get a generator).

All that said, I would think boondocking FOR ME for very long (couple days) without either solar or generator would be difficult. However; some folks live without using much electricity and I bet they can go a pretty good while.

[Twigg]

Originally Posted by PNWorBUST72

So is boondocking more like camping in the RV then living at an RV park cause how else do people boondock unless they have 4000ah battery banks? Is boondocking even a viable option with no solar or genny perhaps?

Well most don't use 1000W induction cooktops

Most cook with propane.

[Twigg]

Originally Posted by JDOnTheGo

Yes!!! Exactly right!



That is a debate that every person has with themselves and their equipment. I have a 10,000 ah battery bank and 2,000 watts of solar to feed my power hungry coach. I made the CHOICE to go all electric (and invest heavily in solar and lithium batteries). A more typical approach (in RV's) is a combined battery and propane system. Using propane for stove top, oven, and refrigeration (absorption fridge) massively reduces your need for electricity. I lived in an RV for a couple years with this setup and 600 watts solar and there was very little difference between "how" I lived when boondocking vs on shore power (mostly boiled down to not running the clothes washer/dryer when boondocking). I'm living entirely off electricity now and again, very little difference between boondocking and with shore power. However; if it is cloudy for several days in a row, I have to conserve power (or I could get a generator).

All that said, I would think boondocking FOR ME for very long (couple days) without either solar or generator would be difficult. However; some folks live without using much electricity and I bet they can go a pretty good while.

Excellent explanations, all down the thread.

[PNWorBUST72]

How does the alternator work in these systems? I never really understood the amp ratings, is that reflective of the amount of amp's it would recharge a battery over the course of an hour?

I assume while driving these issues AS important since you are at least getting some amps back every hour. I also assume there is NOT a direct 100A alternator - you charge back 100amps per hour even in the BEST situation?

I am thinking of using a seperate smart charger versus the all in on converter boxes.

[Twigg]

Originally Posted by PNWorBUST72

How does the alternator work in these systems? I never really understood the amp ratings, is that reflective of the amount of amp's it would recharge a battery over the course of an hour?

I assume while driving these issues AS important since you are at least getting some amps back every hour. I also assume there is NOT a direct 100A alternator - you charge back 100amps per hour even in the BEST situation?

I am thinking of using a seperate smart charger versus the all in on converter boxes.

An alternator won't fully charge some of the more popular house batteries as its output is regulated to 14.2 to 14.4 volts.

[PNWorBUST72]

Is there a way around that or an you tell me what batteries they are limited too maybe?\

But still, getting a constant 14.2 is better then running them down no?

[Twigg]

Originally Posted by PNWorBUST72

Is there a way around that or an you tell me what batteries they are limited too maybe?\

But still, getting a constant 14.2 is better then running them down no?

You can feed an inverter/charger with the alternator output. It will then charge the batteries correctly.

There isn't much advantage in charging house batteries while you are driving because you would generally start a journey with them fully charged and they won't lose much while driving. If you are setting out with the batteries low, then feeding them 14.2 volts for hours will cause problems over the long term. So if I were doing that regularly I'd probably find a way to charge them from the generator.

AGM batteries might suffer less, as they require a lower maximum charge voltage. Flooded Lead/Acid need 14.8 volts to charge them correctly.

[PNWorBUST72]

So if the alt isn't doing a good job charging the batteries while I drive, how does an electric fridge stay powered if I am on long drive?

ALOT of these questions might be my overall lack of RVing knowledge as well my ever inquisitive nature, always analyzing ****.

[JDOnTheGo]

Originally Posted by PNWorBUST72

So if the alt isn't doing a good job charging the batteries while I drive, how does an electric fridge stay powered if I am on long drive?

"...charging the HOUSE batteries..."

Again, a typical RV has an absorption refrigerator that cools using propane when not running from generator/shore power.

Assuming an electric only refrigerator (as I have), your choices are solar (which is what I use while parked and driving), generator, or alternator. You could use the alternator with the appropriate "combiner" (used generically) or the other ideas listed in this thread. Some of this is dependent on the type of batteries you have (the required voltage) as already mentioned.

[Robin97396]

Has anyone done a cost analysis on AGM versus lead/acid batteries?

I'm not trying to be cheap. I've just been wondering about average cost per year during their respective service lives.

I like the fact that AGM doesn't freeze, which could save a northerner's fanny.

[Defjr333]

You CAN charge your house batteries while driving. These units:

Sterling Power battery to battery charging system - Smart DC battery to battery charger, marine grade DC powered charger

take the output voltage of your alternator and converts it to the proper voltage curve. It is a true multi-stage dc to dc charger. Same concept as an MPPT for solar. BUT you need to drive A LOT for it to be beneficial. If you do not drive 100+ miles a day, I would put that $ into the solar. Just my .02
Doug

[Twigg]

Originally Posted by PNWorBUST72

So if the alt isn't doing a good job charging the batteries while I drive, how does an electric fridge stay powered if I am on long drive?

ALOT of these questions might be my overall lack of RVing knowledge as well my ever inquisitive nature, always analyzing ****.

Modern domestic fridges consume far less power than many people think. We have been conditioned over the years by the power consumption of RV fridges, and older domestic ones.

A 10-hour drive won't use a lot, and when you get to the other end you plug into shore-power, or run the genny to top the batteries off.

A newer apartment size fridge will consume around 100W when it's running. But they run around a 30% duty cycle, so around 75 amp hours over 10 hours.

If you have 4 x 225 amphour 6V batteries, that will deplete them by 15 to 16%.

There may be ways to ensure that a smart, three-stage charger can be made to work correctly when fed by an alternator, but I'm not there yet so I haven't investigated.

[david.dgeorge07]

This is what I used.

https://www.amazon.com/gp/aw/d/B0040...ve+relay&psc=1


Sent from my iPhone using Tapatalk

[joeblack5]

For fast and efficient charging you have to use a charger that can measure how much charge (Ah) was take out of the battery.
The vehicle alternator is regulated to a voltage. Voltage is a very poor indicator of the SOC.
There are alternator voltage regulators that are adjustable so that you can increase the voltage and current. The charging can go then very fast but to switch it off before the battery gets overcharged is critical. That is where the capacity meter like trimetric or a cheaper alternative..fleabay#170841787761 comes in.
The charge curves chargers have no good use in partially discharged batteries since they do not know how full or empty the battery is as a result they charge at reduced rates (long time) just to be on the safe side.

Later J

[Twigg]

Originally Posted by Defjr333

You CAN charge your house batteries while driving. These units:

Sterling Power battery to battery charging system - Smart DC battery to battery charger, marine grade DC powered charger

take the output voltage of your alternator and converts it to the proper voltage curve. It is a true multi-stage dc to dc charger. Same concept as an MPPT for solar. BUT you need to drive A LOT for it to be beneficial. If you do not drive 100+ miles a day, I would put that $ into the solar. Just my .02
Doug

That looks like an excellent solution, at a price.

[o1marc]

Originally Posted by Robin97396

Has anyone done a cost analysis on AGM versus lead/acid batteries?

I'm not trying to be cheap. I've just been wondering about average cost per year during their respective service lives.

I like the fact that AGM doesn't freeze, which could save a northerner's fanny.

AGM batteries typically run from 50% more up to double the cost of a liquid battery. The AGM is a compromise between liquid and deep cycle batteries. While it can be used for starting or deep cycle use, they don't perform as well as either of them. AGM only work well to about 50% and charge slower than a liquid battery. A typical liquid battery at 100% may discharge to 70% while starting the engine, but recharge rapidly. Deep cycle batteries are what we want for house batteries. They discharge slowly to 10% and charge slowly also. AGM's last longer, but they don't say how much longer, of course actual use will determine that. Weigh the advantages and disadvantages to determine if the AGM is cost effective for your application.

[Twigg]

Originally Posted by o1marc

AGM batteries typically run from 50% more up to double the cost of a liquid battery. The AGM is a compromise between liquid and deep cycle batteries. While it can be used for starting or deep cycle use, they don't perform as well as either of them. AGM only work well to about 50% and charge slower than a liquid battery. A typical liquid battery at 100% may discharge to 70% while starting the engine, but recharge rapidly. Deep cycle batteries are what we want for house batteries. They discharge slowly to 10% and charge slowly also. AGM's last longer, but they don't say how much longer, of course actual use will determine that. Weigh the advantages and disadvantages to determine if the AGM is cost effective for your application.

Pease don't discharge your deep-cycle batteries to 10%, you will ruin them.

The accepted minimum state of charge is 50%, and many think that even that is too low for longest life.

[o1marc]

Originally Posted by Twigg

Pease don't discharge your deep-cycle batteries to 10%, you will ruin them.

The accepted minimum state of charge is 50%, and many think that even that is too low for longest life.

I agree 10% is pushing it, but that is what is stated on some deep cycle batteries.
A search found this info:
"A deep cycle battery on the other hand has much thicker plates and they are solid, not sponge. These thicker plates have less surface area and thus less of the instant power that a starting battery needs. They are designed to be discharged down to 20% of their maximum charge REPEDITIVELY. The thicker lead plates allow for this as they are much sturdier than their sponge counterparts."


Here's a typical time frame for life:
General expectations for batteries if deep cycled (these are just approximate guidelines):

Starting battery (Automotive battery etc) : 3-13 months
Marine Battery : 1-6 years
AGM Deep cycle: 4-7 years
Gel Cell Deep Cycle: 2-5 years
Flooded Lead Acid Deep Cycle Battery (L16-RE etc): 4-8 years

[Twigg]

Originally Posted by o1marc

I agree 10% is pushing it, but that is what is stated on some deep cycle batteries.
A search found this info:
"A deep cycle battery on the other hand has much thicker plates and they are solid, not sponge. These thicker plates have less surface area and thus less of the instant power that a starting battery needs. They are designed to be discharged down to 20% of their maximum charge REPEDITIVELY. The thicker lead plates allow for this as they are much sturdier than their sponge counterparts."


Here's a typical time frame for life:
General expectations for batteries if deep cycled (these are just approximate guidelines):

Starting battery (Automotive battery etc) : 3-13 months
Marine Battery : 1-6 years
AGM Deep cycle: 4-7 years
Gel Cell Deep Cycle: 2-5 years
Flooded Lead Acid Deep Cycle Battery (L16-RE etc): 4-8 years

The 20% figure sounds like BS marketing speak, or simply written by someone who hasn't a clue.