Battery charging, from another thread

[Bala]

I had been discussing this but i thought it was hyjacking the original thread.

I had noticed mike posting about the required amps of 5% to 10% to charge a battery with panels and the sums did not work for my system.
I had quite a bit of back and forth with Sunking but was still confused.

I have 2200w of 24 panels to charge them, so 94amps, but this is limited to 80amps by my charge controllers.

Through research today i have found that my battery is 1800ah @ C100 rate.
My battery is 1065ah @ C10 rate,
I read that charging requirements are worked out on the C10 rate.

I had been working the sums on 1800ah, C100 rate this means charge amps are about 4.5%

So for my system it would mean that my 80amps of possible charge is about 7.5% of my C10, 1065ah.

So this works out with Mikes 5% to 10% requirments.

Makes sense to me but am I correct?

[Sunking]

Well first you need to look at your battery owners manual, it will tell you what range you need to be at.

Next you are expressing terms incorrectly and is causing some confusion. Example you say C10. Generally C = the Amp Hour capacity at the 20 hour discharge rate. So let's say C = 1000 Amp Hours. So C10 = 1000 AH x 10 = 10,000 Amps. That would of course blow your battery up. I think you mean C/10 which would be correct. 1000/10 = 100 amps.

So what you really want to know, check you manual, is the AH capacity of your battery at the 20 hour discharge rate.

[Bala]

My system seems to work fine, I am following this to understand more on how systems are designed and work to ensure I get the best from it,

Where i got C10 from?

The C10 amp hour info is in my manual, it is also in the brochure attached, on the table Electrical specs @ 25c
My batteries are the 4RP1800

http://www.exide.com.au/industrial/specs/ExideBrochure.pdf

Below is a paragraph from a site I found while researching info on charging, the link is to the whole page,

"Referring back to my battery charging page you will see that a 1200 amp/hour battery bank requires a battery charger of at least 10% C10 capacity. The C10 capacity of this battery bank (Exide Energystore 4RP1330) is 800 amp/hours so the minimum battery charger that is required is a unit of around 80 amps."

http://www.tasmanenergy.com.au/direct_charging.html

[Sunking]

Where i got C10 from?

OK I see where the confusion coming from. Look closely at the Exide brochure. 10 is subscript and looks something like this C10. That is telling you the 10 hour discharge capacity of the battery.

[Bala]

my owners book does list it as C10 but i get what you are saying about how it is written.

So what is the most common way to size battery for a stand alone solar system, that paragraph I posted shows find the c10 rate and go from there, that works for me, but is that normal, or your way sunking?.

Just in case your bored i have a real time situation, a friend has a micro hydro system, no solar, the hydro puts out 10amps, 24v .
But due to blockage it had been down to about 6amps, throw in an old fridge, lights and someone who did not realize the batteries are down to 22v and sounds like they have been at that for weeks at least. hydrometer does not read.

I am trying to tell him how much in amps he needs to try?? to recharge his batterys, I have suggested they may well be US.

Best info i can find for him( he has no manuals ) is that his batteries are 750ah @c100

As a hydro produces power 24 hrs a day I would think it would be done a bit different.

how would you size charging for a hydro system?

[Sunking]

So what is the most common way to size battery for a stand alone solar system,

It is really very simple.

Calculate you daily watt hour consumption.
Multiply daily consumption by 5.
Divide by nominal battery voltage.

So for example let's say you use 1000 wh per day and use a 12 volt battery system. [1000 wh x 5] / 12 volts = 416 Amp Hours.

[Bala]

Sorry my typo,

It was meant to be "size battery charging capacity" for a stand alone sytem

[Sunking]

It was meant to be "size battery charging capacity" for a stand alone sytem

What you are fishing for solar panel wattage. Again very straight forward process.

Determine daily watt hour used.
Select system efficiency of 50% or PWM charge controllers, or 66% for MPPT controllers.
Determine worse case sun hours which is winter for me in the month of December.

So back to the example of 1000 watt hours per day, 3 hours insolation, PWM controller. Formula is watts = [daily wh / .5] / Sun Hours. so [1000 wh / .5] / 3 = 666 watts.

[russ]

No - Bala is tying to help a friend with a micro hydro setup.

Russ

[Bala]

yep Im looking for how to work out charging,

So once battery capacity is decided on,

How many amps of charge do you need avail from,

a: panels

b: ac charger

c: hydro ( if it different from the other 2)

[Sunking]

yep Im looking for how to work out charging,

So once battery capacity is decided on,

How many amps of charge do you need avail from,

a: panels

b: ac charger

c: hydro ( if it different from the other 2)

Don't worry about charge amps, worry about solar panel wattage, that will take care of the charge amps.

Use the two examples I just used for battery capacity and solar panel wattage. With a 660 watt solar panel will deliver 50 amps to a 12 volt 420 AH battery using a MPPT charge controller, or 41 amps with a PWM which is a C/8 and C/10 charge rate respectively. Perfect, and I never even gave charge rate one thought.

[russ]

This is for his buddy's micro hydro unit

[Sunking]

This is for his buddy's micro hydro unit

I know Russ, it doesn't change my answer. Solar panels and batteries are matched to the daily watt hour use.

Sure I could say size the system to supply C/8 to C/10 charge current, but that is meaningless. Think what would happen if you did like a lot of DIY's on here and went out and bought a 240 watt panel, 12 volt 200 AH battery, and need say 2 Kwh of power every day. Will it work? Yep for about 1 day and you are done. A 240 watt panel with MPPT would supply 20 amps the perfect C/10 charge rate, so what it will not work.

[Mike90250]

I'd think daily hydro production needs to be 120% of daily usage. Batteries need to = 3 days of consumption.

10 KWH usage, needs 12kwh hydro (or solar) and you need 30KWh of batteries. This "uses" the batteries pretty hard in solar, but hydro, where you ALWAYS have charge 24/7, it won't hardly use the batteries till you start the fridge motor.

[Sunking]

This is for his buddy's micro hydro unit

shucks i need to get my glasses checked. I thought you said hydroponics garden. Sorry guys my bad.