Set up a small system for a local guy... He seems to think the battery is draining too quickly

[ericfx1984]

Recently set up a system for fellow... Cheap Chinese 3,000 w all in one 24 volt inverter, 1200 Watts of solar panels and a cheap Chinese 24 volt 100 amp power battery

Anyway he's been living for about a year or more with no electricity other than running a generator powered off of propane

For him this has been a game changer

However every now and again he will wake up and the batteries are drained down to about 24 volts...

Today I went ahead and charged his batteries by using his generator to power the AC charger

Brought it up full power until the battery stopped charging and then used a clamp meter on the battery and a 1500 watt heat gun

The heat gun worked out to about 1,450 watts coming off the battery and he ran for about an hour and a half before the battery went to the inverters shut off voltage which works out to about 10% battery remaining

Now this isn't a particularly accurate test... But based on the numbers the battery test at about 96% or... 2450 watt hours

I feel like for this type of test especially being pulled at a rather high rate of discharge... It's within the margin of error

In short the battery could be 90% or it could be 110% or anything in between

Anyway he lives in an RV and he would like to run his small portable air conditioner

I initially explained to him that the 24 volt, 100 amp hour lithium iron phosphate battery could probably do it but that it would really be on the absolute limit of its capabilities

I believe I have him convinced to add a second battery at this point

Does my testing methodology seem to make sense...

My calculations I would think that he should be able to run the portable air conditioner overnight for about 4 hours and still have a reasonable reserve in the morning

Luckily his portable air conditioner has a shut off timer

Thoughts? Comments? Critiques? Insults?

 

[pollenface]

2560wh = 2048wh @ 80% depth of discharge.

I estimate the AIO unit would use half of that in standby power alone overnight.

An additional battery sounds good to me.

 

[ericfx1984]

2560wh = 2048wh @ 80% depth of discharge.

I estimate the AIO unit would use half of that in standby power alone overnight.

An additional battery sounds good to me.

It doesn't use anywhere near that... At idle I think it's pulling about 60 w or so

 

[Q-Dog]

It doesn't use anywhere near that... At idle I think it's pulling about 60 w or so

Multiply 60 watts times 12 or 14 hours. It might not quite be half, but it is more than 1/3 of capacity.

 

[LydMekk]

Most people do not grasp the amount of batteries needed for their consumption.
They often need 2-3 times the initial battery storage.
Chalk it up to lessons learned.

 

[42OhmsPA]

Most people do not grasp the amount of batteries needed for their consumption.
They often need 2-3 times the initial battery storage.
Chalk it up to lessons learned.

This!
I had a rough idea based on months of research / planning. I started with ~22kwh back in Oct. I plan to have 44kwh by this September, along with a ground mount array SSE to help the S and W rooftop arrays.

 

[400bird]

Multiply 60 watts times 12 or 14 hours. It might not quite be half, but it is more than 1/3 of capacity.

If the inverter is on, those 60 watts are used.
60 watts X 24 hours = 1.4 kWh

I'd say it's more than half of his capacity if the inverter is on all day.

 

[Q-Dog]

If the inverter is on, those 60 watts are used.
60 watts X 24 hours = 1.4 kWh

I'd say it's more than half of his capacity if the inverter is on all day.

He has solar panels to charge up during the day. He only has to get through the night when there is no solar.

 

[Alice2021]

100Ah battery can not run full 3000W inverter , and once he plugs in a high power appliance,such as fridge, microwave oven,etc, his battery will fall down very fast..So please suggest him to add more pcs battery.

 

[ericfx1984]

100Ah battery can not run full 3000W inverter , and once he plugs in a high power appliance,such as fridge, microwave oven,etc, his battery will fall down very fast..So please suggest him to add more pcs battery.

I suggested it to him before we even did the install...

And if you do the math it's only pulling about 65 amps Off the battery when you're pulling around 1300 or 1400 Watts off the AC side

But it's just fine for light use

 

[ericfx1984]

Most people do not grasp the amount of batteries needed for their consumption.
They often need 2-3 times the initial battery storage.
Chalk it up to lessons learned.

I would agree with that... But I had suggested to him before we even got started that he needed at least one more battery

 

[ericfx1984]

Most people do not grasp the amount of batteries needed for their consumption.
They often need 2-3 times the initial battery storage.
Chalk it up to lessons learned.

One of the things I've been doing is letting him borrow my kill-a-watt and going over periodically to his place to give him a running total...

He has been amazed by how much energy he actually uses

 

[Alice2021]

An inverter is just a converter, not an energy producer.
We should offer enough batteries before it can drive the electrical appliances.

 

[ericfx1984]

An inverter is just a converter, not an energy producer.
We should offer enough batteries before it can drive the electrical appliances.

What are you even talking about?

 

[pollenface]

It doesn't use anywhere near that... At idle I think it's pulling about 60 w or so

I still recommend adding additional battery capacity

He has solar panels to charge up during the day. He only has to get through the night when there is no solar.

14hrs of non-sunlight would draw about 840wh, give or take...

 

[ericfx1984]

He finally agreed to order a second 24 volt 100 amp power battery... He'll be sitting at around 5 kilowatt hours... Maybe four or four and a half kilowatt hours usable

 

[LydMekk]

Like pulling teeth, eh ?

 

[ericfx1984]

Like pulling teeth, eh ?

Well when I first started planning his system I suggested the second battery and ideally a third... But he started saying, "Oh Eric... I don't use a whole lot of power All I use is this air conditioner and a propane furnace"

I Explained to him that an air conditioner actually does pull a considerable amount of energy and really if it's cold enough even the propane forced air furnace can pull quite a bit of air as it can be on for quite some time

 

[MisterSandals]

I don't use a whole lot of power All I use is this air conditioner and a propane furnace"

This is exactly the reason most here insist on having a basic energy audit before proceeding with unknown requirements.

 

[sunshine_eggo]

Well when I first started planning his system I suggested the second battery and ideally a third... But he started saying, "Oh Eric... I don't use a whole lot of power All I use is this air conditioner and a propane furnace"

I Explained to him that an air conditioner actually does pull a considerable amount of energy and really if it's cold enough even the propane forced air furnace can pull quite a bit of air as it can be on for quite some time

Gallons of gas consumed in a generator is a decent approximation of electrical needs.

A gallon of gas has 33.7kWh of energy in it. Assume the generator converts 1/3rd of that into electricity.

So, one will need 11.2kWh of electrical energy for for every gallon of gas their generator consumes if supplying via solar/battery.