Solar 101

[Guest]

Unfortunately you will not be able to make your own post until you get vetted by our Admin Solar Pete.

To answer your question. Your 7Ah battery is not be getting back up to 100% SOC since it has been discharged to 0% SOC. With a 5w bulb running 24 hours you are consuming 120watt hours a day. That 7Ah can provide about 84wh if you use 100% of it's charge.

A battery that can safely provide that amount daily will need to be about 40Ah (120wh / 12v x 4days = 40Ah). That will require about 4 amps of charging or a panel wattage close to 80w.

So in short your 10W panel and 7Ah battery is too small for your 5 watt bulb to run 24 hours.

Thanks so much !
how do i get my 7ah battery to its normal state again ? When i see the charge controller it shows 14.4v around afternoon, begins with empty battery sign in morning. I usually drain it completely by turning on the 5 watt bulb at night which goes on for about 2 hours.

[SunEagle]

Thanks so much !
how do i get my 7ah battery to its normal state again ? When i see the charge controller it shows 14.4v around afternoon, begins with empty battery sign in morning. I usually drain it completely by turning on the 5 watt bulb at night which goes on for about 2 hours.

A damaged battery may seem to be charging back up to full capacity but under load the voltage will quickly drop.

Unfortunately once a battery has been drained, it has been damaged and may never be able to store 100% of it's rating again. I would look into getting a new battery and one that is a little larger so it meets your watt hour requirements. Remember to also increase you panel wattage to match the battery requirements.

[Sunking]

Thanks so much !
how do i get my 7ah battery to its normal state again ?

You don't, you destroyed it by abuse. A dead battery will show fully charged soon after you put it on a charger. Tu run a 5 watt light say 12 hours per day requires 12 volt 25 AH battery. A 12 volt 25 AH battery will require a 50 watt panel.

[sevensuns]

You don't, you destroyed it by abuse. A dead battery will show fully charged soon after you put it on a charger. Tu run a 5 watt light say 12 hours per day requires 12 volt 25 AH battery. A 12 volt 25 AH battery will require a 50 watt panel.

Hi !

Thanks so much for your help.

I forgot the mention i am using a solar charge controller so it restricts the battery drain. However the battery seems to have drained, after fully charged my old 12v 7 amp is able to power my 5 watt bulb for not more than 3 or 4 hours.

I got a new 12v 7amp battery and it seems to power for more than 5 hours atleast after fully charged.

I got a new panel 18v 30w. Please tell me how do I hook it up all together. How do i connect my existing 12v panel 10w panel with the new 18v 30w panel ? series or parallel ?

I am a bit worried about connecting the old battery in parallel since the old one seems to be draining quickly and might affect the new one too.

What would be my best option ?

Thanks for your help appreciate it.

[SunEagle]

Hi !

Thanks so much for your help.

I forgot the mention i am using a solar charge controller so it restricts the battery drain. However the battery seems to have drained, after fully charged my old 12v 7 amp is able to power my 5 watt bulb for not more than 3 or 4 hours.

I got a new 12v 7amp battery and it seems to power for more than 5 hours atleast after fully charged.

I got a new panel 18v 30w. Please tell me how do I hook it up all together. How do i connect my existing 12v panel 10w panel with the new 18v 30w panel ? series or parallel ?

I am a bit worried about connecting the old battery in parallel since the old one seems to be draining quickly and might affect the new one too.

What would be my best option ?

Thanks for your help appreciate it.

Unfortunately most charge controllers will let a 12v battery get below 11v which is a death sentence.

Panels can be wired in parallel if their Vmp is within 5% and in series if their Imp is within 5% of each other. Depending on what the specs of your 10w & 30w panel they may not get you in the ballpark. If they are more then 5% different then the smallest Vmp rated panel will limit the higher rated one.

You are correct in not wanting to wire an old and new battery in parallel because the old one will hurt the new one.

Just to give you some idea how many watt hour a 7Ah battery can safely provide. You multiply the voltage x Ah x 25% or 12 x 7 x 25% = 21 watt hours. That is about a 25% discharge of the battery. Going more will shorten the life and you will get less cycles out of it. A 5 watt bulb running 5 hours is 25 watt hours which is more then the safe calculation of 21 watt hours.

I would get a bigger battery and make sure you can provide a C/10 charge rate where C = Ah of the battery.

[sevensuns]

Unfortunately most charge controllers will let a 12v battery get below 11v which is a death sentence.

Panels can be wired in parallel if their Vmp is within 5% and in series if their Imp is within 5% of each other. Depending on what the specs of your 10w & 30w panel they may not get you in the ballpark. If they are more then 5% different then the smallest Vmp rated panel will limit the higher rated one.

You are correct in not wanting to wire an old and new battery in parallel because the old one will hurt the new one.

Just to give you some idea how many watt hour a 7Ah battery can safely provide. You multiply the voltage x Ah x 25% or 12 x 7 x 25% = 21 watt hours. That is about a 25% discharge of the battery. Going more will shorten the life and you will get less cycles out of it. A 5 watt bulb running 5 hours is 25 watt hours which is more then the safe calculation of 21 watt hours.

I would get a bigger battery and make sure you can provide a C/10 charge rate where C = Ah of the battery.

-------------

Thanks so much for sharing that valuable knowledge.

So you are suggesting to use my new 18v 30w panel with the new 12v 7 amp battery only. I guess I can use the old 12v 7amp battery with the 10w panel separately until the battery lasts.
I am a bit worried on spending too much on a 25 amp battery its kind of costly here in gulf !

I noticed the charge controller drains battery upto 11.3v on my old battery. My old battery worked fine for a year but i guess Chinese batteries cannot be relied on. Some might last longer.
I guess would use both separately but i do not have 2 charge controllers so would use the 10w panel during day only then switch to 30w panel connected to battery.

Thanks again.

[SunEagle]

-------------

Thanks so much for sharing that valuable knowledge.

So you are suggesting to use my new 18v 30w panel with the new 12v 7 amp battery only. I guess I can use the old 12v 7amp battery with the 10w panel separately until the battery lasts.
I am a bit worried on spending too much on a 25 amp battery its kind of costly here in gulf !

I noticed the charge controller drains battery upto 11.3v on my old battery. My old battery worked fine for a year but i guess Chinese batteries cannot be relied on. Some might last longer.
I guess would use both separately but i do not have 2 charge controllers so would use the 10w panel during day only then switch to 30w panel connected to battery.

Thanks again.

Well the 30w panel should be enough to keep the 7ah battery happy. But your problem is the battery is too small to run your loads as long as you want. Either reduce the light wattage, get a bigger battery or settle on less than 5 hours of battery life.