inverter question

[Mike90250]

Opps

Another quick question.
Should I keep the battery box separate from the controllers?
I guess the answer will be yes and well ventilated.

Mark

yes, you don't want acid mist from batteries getting into the electronics.

[mark2310]

Hi
Thanks again for all of the info.
I think I will use a battery bank of 4 12v 125ah wired as shown in the earlier link.

As I have mentioned im not always there in the van so this will give recovery time to the system should it be run to low, but as with most things im tight so will probably turn the fridge off last thing at night.

We also have a lot of sun/daylight there about 6-7hrs winter and about 16hrs this time of year.
Hope to start testing and building in the next couple of weeks.

Thanks again for all of your help.

Mark

Opps

Another quick question.
Should I keep the battery box separate from the controllers?
I guess the answer will be yes and well ventilated.

Mark

[mark2310]

Yeah there's no way your fridge is using that much, more likely something like a third of that. You can probably find a number online or in its literature but the way they're tested can be kind of rigged so to get a real number kind of takes a killowatt.

Also, if you plug in a room temperature fridge and measure that it will show you a significantly higher power consumption than normal.

Hi
Thanks again for all of the info.
I think I will use a battery bank of 4 12v 125ah wired as shown in the earlier link.

As I have mentioned im not always there in the van so this will give recovery time to the system should it be run to low, but as with most things im tight so will probably turn the fridge off last thing at night.

We also have a lot of sun/daylight there about 6-7hrs winter and about 16hrs this time of year.
Hope to start testing and building in the next couple of weeks.

Thanks again for all of your help.

Mark

[Bucho]

So the problem is the fridge running 24hrs at 150 watt burning 3600wh.
It wont be running all the time so I need to figure out how much power it takes over 24 hrs.

Mark

Yeah there's no way your fridge is using that much, more likely something like a third of that. You can probably find a number online or in its literature but the way they're tested can be kind of rigged so to get a real number kind of takes a killowatt.

Also, if you plug in a room temperature fridge and measure that it will show you a significantly higher power consumption than normal.

[SunEagle]

Thanks
Ive got one of those only problem is the fridge is in the van and the van is in the middle of nowhere so will have to run the generator for a while to figure out what its using.
Anyone got any idea a 12v 150 watt fridge will use in 24hrs?

Mark

Some refrigerators have a yearly estimated watt hour usage printed on their labels.

I don't know if that 12volt unit has that information but my guess there is not a lot of insulation on that thing so it could need to run a lot to keep the temps low inside.

[mark2310]

There is a device called "kill a watt" meter that will measure the amount of watts an appliance uses. You would measure the load for a few days which would get you an average daily watt hour usage.

More than likely, unless the fridge is very inefficient, it probably draws that 150watts for a few minutes every hour. But if you guess too little you can easily undersize your battery system and quickly kill them.

Thanks
Ive got one of those only problem is the fridge is in the van and the van is in the middle of nowhere so will have to run the generator for a while to figure out what its using.
Anyone got any idea a 12v 150 watt fridge will use in 24hrs?

Mark

[SunEagle]

So the problem is the fridge running 24hrs at 150 watt burning 3600wh.
It wont be running all the time so I need to figure out how much power it takes over 24 hrs.

Mark

There is a device called "kill a watt" meter that will measure the amount of watts an appliance uses. You would measure the load for a few days which would get you an average daily watt hour usage.

More than likely, unless the fridge is very inefficient, it probably draws that 150watts for a few minutes every hour. But if you guess too little you can easily undersize your battery system and quickly kill them.

[mark2310]

That is a lot of energy to run from batteries and will be costly.

If you are going to use 4kWh daily then you will need a battery 5 times that so that you will not discharge it more than 20% a day and have a couple of days of power if the sun isn't shining.

So 4000 x 5 = 20000watt hours.

That is big so you should be looking at a 48 volt battery system. 20000 wh / 48 v = 417Ah. So you need to build a system of batteries that consists of 24 x 2volt 400Ah or 12 x 4volt 400Ah batteries.

Your panel wattage will be around 2000 watts and you will need a 40A MPPT charge controller.

Are you starting to understand the costs to run your electrical loads? You might want to rethink what to run and what not to.

So the problem is the fridge running 24hrs at 150 watt burning 3600wh.
It wont be running all the time so I need to figure out how much power it takes over 24 hrs.

Mark

[SunEagle]

Ok

I know have a total of 4020 watt hours.
Do I need to multiply by something to get the battery size?

Thanks

That is a lot of energy to run from batteries and will be costly.

If you are going to use 4kWh daily then you will need a battery 5 times that so that you will not discharge it more than 20% a day and have a couple of days of power if the sun isn't shining.

So 4000 x 5 = 20000watt hours.

That is big so you should be looking at a 48 volt battery system. 20000 wh / 48 v = 417Ah. So you need to build a system of batteries that consists of 24 x 2volt 400Ah or 12 x 4volt 400Ah batteries.

Your panel wattage will be around 2000 watts and you will need a 40A MPPT charge controller.

Are you starting to understand the costs to run your electrical loads? You might want to rethink what to run and what not to.

[mark2310]

Knowing how many watts each load is only half the answer. How long are you going to run each item on a daily basis. From that you can calculate the watt hours and then add them up to size your battery system.

Fridge @ XX watts * y hours = z watt hours
Lights @ 20 watts * a hours = b watt hours
Fan @ 35 watts * c hours = d watt hours
Micro @ 800 watt * f hours = g watt hours

z + b + d + g = daily watt hours.

Ok

I know have a total of 4020 watt hours.
Do I need to multiply by something to get the battery size?

Thanks

[SunEagle]

Hi

The system is not yet built im looking for info and checking what I have will work.
I need to buy batteries but I have a 12v 110ah battery kicking around at the moment, sorry if this has lead to any confusion.

So to recap.

2x 235 watt panels at 37v
MPPT 40 amp
12 Volt 1000 watt inverter (Brought over a year ago before I thought of doing this)
12v 110 ah battery ( well forget about the battery)

I would like to run a fridge in my van at weekends or for a week if I stay longer. (may run this on 12v)
Led lights 20 watts max.
Fan 35 watts
Microwave 800 watts

Info on the type of batteries and numbers would be helpful as I think most of my questions have been answered.

Thanks again to all for the info so far.
Mark

Knowing how many watts each load is only half the answer. How long are you going to run each item on a daily basis. From that you can calculate the watt hours and then add them up to size your battery system.

Fridge @ XX watts * y hours = z watt hours
Lights @ 20 watts * a hours = b watt hours
Fan @ 35 watts * c hours = d watt hours
Micro @ 800 watt * f hours = g watt hours

z + b + d + g = daily watt hours.

[mark2310]

What battery are you using because you're charging it at something like c/3

Hi

The system is not yet built im looking for info and checking what I have will work.
I need to buy batteries but I have a 12v 110ah battery kicking around at the moment, sorry if this has lead to any confusion.

So to recap.

2x 235 watt panels at 37v
MPPT 40 amp
12 Volt 1000 watt inverter (Brought over a year ago before I thought of doing this)
12v 110 ah battery ( well forget about the battery)

I would like to run a fridge in my van at weekends or for a week if I stay longer. (may run this on 12v)
Led lights 20 watts max.
Fan 35 watts
Microwave 800 watts

Info on the type of batteries and numbers would be helpful as I think most of my questions have been answered.

Thanks again to all for the info so far.
Mark

[Bucho]

At the moment the system im building has 2X 235watt panels at 37v each.
A 40 amp MPPT.
One 110 ah 12v battery.

What battery are you using because you're charging it at something like c/3

[mark2310]

Running a 240volt AC unit from batteries through an inverter is very costly based on the size of your battery system needed and inefficiencies of the inverter.

Thanks again to all that have replied.

I guess I need information on how to proceed with the items I have. I still need to purchase batteries. (any ideas) I've read the link supplied above thanks.
The items I will be running of the set up will be.

A fridge rated at 150 watts.
Small amount of Led lighting. 20 watt max.
Microwave 800 watts.
Fan 35 watts.

Mark

[SunEagle]

Hi

Thanks again for the info.
Is it not possible to use the inverter with more batteries wired in parallel?

My use for the set up will be to run my caravan and I intend to build the system to be mobile on a small trailer so all items will have a sort cable run except for the connection to the van. This will be from the inverter to the van 240v AC.

I hope what im trying to say makes sense.

Thanks
Mark

Running a 240volt AC unit from batteries through an inverter is very costly based on the size of your battery system needed and inefficiencies of the inverter.