Battery size and use

[sunstroke]

I bought 2 AGM batteries that are 12v-10aH, sealed, spill proof and lead acid, rechargeable. Can I use them for solar power? I have a 100watt controller and 4- .1.5watt solar panels all from Harbor Freight and a 400watt inverter. I am just beginning and learning this solar power stuff. Any help would be appreciated. I just want to tinker with it until I understand it.

[PNjunction]

Want to know the super super shortcut? Here it is:

So, what's the max watt-hours we can take out of this battery? Use the power-formula, (P/I*E) aka (Watts / Current * Voltage)

12v battery * 20ah = 240 watthours. BUT, we now divide this in half so as not to exceed a 50% discharge.
240 / 2 = 120 watthours.

Now multiply this by 0.9 to account for the inverter loss.

120 * 0.9 = 10.8 watt max load.

This would be the maximum wattage of your load to use without getting too heavily into the Peukert factor, and would provide at least a 10 hour runtime.

Real world values may need tweaking, but this is napkin-calc.

Tip: If you are going to wing it instead of calculating and measuring it, after a discharge, let your agm rest for a few hours. 4 hours or more preferable. Assuming they are in good shape (and that's a BIG assumption), then your resting voltage with no load and no charge should be about 12.2 to 12.3v for a 50% DOD. If lower, than you discharged too far, or too fast / puekert.

[PNjunction]

Also know that with agm's, taking them down to 50% DOD on a daily basis means that you only have about 300-500 cycles. You get a year's worth or so of operation from them.

Cutting your load in half so that you only draw 25% capacity from them, and now you are extended to about 900-1200 cycles - maybe 3 to 4 years.

So to get 3-4 years, you'd cut your load in half again to only 5 watts or so! That would be like driving a 20-watt "equivalent" led bulb daily for 10 hours.

You can see why if you have the time and knowledge to take care of flooded deep cycle batteries, they represent a more cost-effective choice in a low-current application.

[littleharbor]

Also four 1-1/2 watt solar panels aren't going to charge anything. Your 20 ah of battery will need around 2 amps @12 volt nominal voltage, Find yourself a 35 to 40 watt solar panel.

[robert normandeau]

Help need please !,,,,
Can I use only a 6v golf cart battery for using my 200w solar system? OR need minimun 2x6V batteries ?

THANKS

[Sunking]

Help need please !,,,,
Can I use only a 6v golf cart battery for using my 200w solar system? OR need minimun 2x6V batteries ?

THANKS

Sure you can. Batteries are not 6 or 12 volts. They are 2 volts.

A 200 watt solar system assuming you are using a MPPT charge controller can support a 12 volt 130 AH up to 12 volt 200 AH battery. Makes no difference what voltage the battery is as long as it is the required AH capacity without having to parallel batteries. The issue is weight and space.

A 12 volt 200 AH battery is available and about the largest 12 volt battery you can buy. A 12 volt 200 AH battery weighs in around 1140 pounds. A 6-volt 200 AH battery weighs in around 70 pounds, a 4 volt 200 AH around 35 pounds if they made them.

I do not know about you, but if I needed 12 volts at 200 AH, I would use 2 6-volt 200 AH batteries and save my back for my wife.

[robert normandeau]

Thanks.
6v golf cart batteries are lighter ? Maybe would need two, what do you think ?

Need 300W/daily because of the 2 to 3 sunhours for feb - March.
Need for this reason = I bought a 170-250 heater
Is it OK to have MPPT 30A with my 200w system for security and for the future in case I would put 3 panels ?

Thanks for your useful help

Robert

[robert normandeau]

I mean 170W using the Lo power and 250W using the Hi power with my new heater

Robert

[robert normandeau]

Can I use 2 x 6V golf cart batteries (500 Ah total) with my MPPT 30A, will it support this power ?

Robert

[robert normandeau]

A 200W solar panels system can only support a 200 Ah battery ? No more ? Can't use a 250 Ah battery ? Could you confirm me this, please !
So wouldnt be useful to buy 2 x 6V golf cart batteries for 450 Ah ? What do you think about it ?
And want to put 2 x 100W solar panel en parallel to get more Ah possibly. AM I right ?

Robert

[ButchDeal]

Can I use 2 x 6V golf cart batteries (500 Ah total) with my MPPT 30A, will it support this power ?

Robert

It is only 500ah if you run it parallel at 6v. In series at 12v it will be 250ah
Yes you can you them in series at 12v with an mppt CC

[robert normandeau]

Thank you ButchDeal
Please can you answer all my questions written just before rhat, please

Robert