Self Contained Shipping Container and I am more than confused.

[PalapaScott]

First of all I am a Solar newb and a huge researcher. It seems like the more I read the more confused I get so I am asking for anyones help that is willing to offer it on setting up an off the grid solar setup. I have been trying to back into the solar panel sizing and I just dont think I am doing this right.

Here are the basics of what we need. We will need to operate 2 battery chargers from the solar setup to keep 2 batteries charged for use at all times. One issue we have is that the batteries could be used daily and therefore need to be charged daily or there could be a number of days of no use. The chargers are the type that charge at a higher rate until the battery is charged then drop down to a trickle charge. My thought is figure the solar setup using the worst case scenario and saying there will be a daily discharge and subsequent need to use the higher power charge rate to recharge the batteries.

Here are the specs on what we have.

Battery 1 that will need to be charged. 48v sealed battery. The charger we were given to charge looks like a small scooter battery charger. The numbers on this charger are as follows.
110ac output 36v 1.8a. This does roll down to a trickle charge but I do not have the specs on the amps it runs at. Assuming 1a on trickle. Typically this takes about 6 hours to charge the battery.

Battery 2: 12v marine deep cycle battery. The charger to charge this battery will be one of the typical car chargers that can deal with deep cycle batteries. The numbers I have on that are as follows.
110ac output 12v 12a for normal charge and 12v 2a on trickle charge. This battery would require about 5 hours to charge before switching to trickle.

As far as I can see this will require an inverter to run the chargers.

The question I have is what size solar setup would we need for this. We are in Houston and I have read that 4.5 hours of sun per day is what we would expect.

In trying to figure this out I came up with needing a 6kw system and I just know that is not right. A $10k dollar system for 2 battery chargers doesnt make since. After more research I think I determined the watt hour needs are 2520 for a 24 hr period. Do we divide that by 24 to get an hourly draw and then start backing into the solar setup? AS you can see I seem pretty mixed up.

So, any assistance anyone can give we would appreciate.

[ButchDeal]

Battery 1 that will need to be charged. 48v sealed battery. The charger we were given to charge looks like a small scooter battery charger. The numbers on this charger are as follows.
110ac output 36v 1.8a. This does roll down to a trickle charge but I do not have the specs on the amps it runs at. Assuming 1a on trickle. Typically this takes about 6 hours to charge the battery.

Are you sure that battery #1 is 48V? and that that charger is the one to use with it? or that its output is 36V?

Battery 2: 12v marine deep cycle battery. The charger to charge this battery will be one of the typical car chargers that can deal with deep cycle batteries. The numbers I have on that are as follows.
110ac output 12v 12a for normal charge and 12v 2a on trickle charge. This battery would require about 5 hours to charge before switching to trickle.

ok so this one is simple toss your charger and get a PWM or better MPPT charge controller. This will go directly from solar to charging the battery.
How many amp hours is the battery?

As far as I can see this will require an inverter to run the chargers.

not necessarily.

The question I have is what size solar setup would we need for this. We are in Houston and I have read that 4.5 hours of sun per day is what we would expect.

In trying to figure this out I came up with needing a 6kw system and I just know that is not right. A $10k dollar system for 2 battery chargers doesnt make since. After more research I think I determined the watt hour needs are 2520 for a 24 hr period. Do we divide that by 24 to get an hourly draw and then start backing into the solar setup? AS you can see I seem pretty mixed up.

So, any assistance anyone can give we would appreciate.

deal with the batteries separately. The 12V deep cycle lead acid can be done more simply.

[PalapaScott]

Are you sure that battery #1 is 48V? and that that charger is the one to use with it? or that its output is 36V?

The motor is supposed to be a 48v motor but that I am not 100%. Will need to do some digging to double check. For the charger I am sure on the numbers as they are right there and this is the charger they sent for the motor. This is a custom built unit from China and who knows what they may have changed and not told us.



ok so this one is simple toss your charger and get a PWM or better MPPT charge controller. This will go directly from solar to charging the battery.
How many amp hours is the battery?

Amp hours are rated as follows: 20 amp hours 105.

I like the idea of skipping a piece in the puzzle (inverter) but now it seems I need to figure out how this works without it and how to determine the solar panel needs


not necessarily.



deal with the batteries separately. The 12V deep cycle lead acid can be done more simply.

See bold

[SunEagle]

You are going about this incorrectly.

There are a number of sticky posts in the off grid section of this forum. Start reading the ones that talk about battery sizing. That is how you determine how big a battery system I would need to get your daily watt hour usage without discharging the battery more than 25% each day.

[PalapaScott]

You are going about this incorrectly.

There are a number of sticky posts in the off grid section of this forum. Start reading the ones that talk about battery sizing. That is how you determine how big a battery system I would need to get your daily watt hour usage without discharging the battery more than 25% each day.

My only issue with that is I am not certain I am figuring the watt hours correctly. When doing so do you sue the dc current or the ac current multipled by the amps to get the watts on the chargers. How does this figure into the the advice that butchdeals post mentioned regarding dropping the inverter

[organic farmer]

One of the many beauties of off-grid solar power systems is that every system is different.

I am not sure of what the purpose is for having two independent battery-banks.

[PalapaScott]

One of the many beauties of off-grid solar power systems is that every system is different.

I am not sure of what the purpose is for having two independent battery-banks.

The batteries I am talking about are on a pedal powered bike that has a (supposedly) 48v assist motor. There is a sealed battery specifically for that motor and We are adding a second 12v battery to power lights and a car stereo. So I am not looking to setup 2 solar battery banks but to charge the 2 batteries on the pedal bike from a solar power source.

[SunEagle]

My only issue with that is I am not certain I am figuring the watt hours correctly. When doing so do you sue the dc current or the ac current multipled by the amps to get the watts on the chargers. How does this figure into the the advice that butchdeals post mentioned regarding dropping the inverter

You can use the voltage times the amps to calculate watts but having a meter to do the work for you over a period of time is better. Just taking a snap shot of the voltage and amps can result in an inaccurate watt usage.

If you have DC loads you do not need an inverter. The inverter will add some waste into the formula and use some of the total watt hours consumed.

If you are just guessing to the amount of watt hours used IMO you will end up with either too small or too big of a battery system. Also the size of your pv panel wattage will be based on the size of your battery so if you are off in one place you will be off in both.

[SunEagle]

The batteries I am talking about are on a pedal powered bike that has a (supposedly) 48v assist motor. There is a sealed battery specifically for that motor and We are adding a second 12v battery to power lights and a car stereo. So I am not looking to setup 2 solar battery banks but to charge the 2 batteries on the pedal bike from a solar power source.

To charge a 48volt battery will require almost 60volts from your panels going into a 48V charge controller. Since most panels do not generate 60volts you would be required to wire a number in series. The total number of panels will be determined by the total amount of charging amps required for a specific battery system.