# Question about charging batteries in parallel & charging in general

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**22**✭
Q1. If I have (2x) 12Vdc 100Ah batteries in parallel, will they all charge evenly?

Q2. If I have (2x) 12Vdc 100Ah batteries in parallel, how many Renogy 100 watt panels will I need to charge them in 1 day?

Q3. If I have (2x) Renogy 100 Watt panels, that have an Isc Short-Circuit Current rating, and If I want to use an inverter connected directly to the panels, will the load be divided evenly between the two panels? If I have a 7 amp load, will each of the panels only share 3.5 Amps for each of the two panels?

Maximum Power: 100W

Maximum System Voltage: 600V DC (UL)

Optimum Operating Voltage (Vmp): 18.9V

Optimum Operating Voltage (Vmp): 18.9V

Open-Circuit Voltage (Voc): 22.5V

Short-Circuit Current (Isc): 5.75A

Dimensions: 47 X 21.3 X 1.4 In

Weight: 16.5lbs

Can you show me where a good decent Pure Sine Wave Power Inverter is or what it's name is? I've looked at Home Depot and Amazon Prime, and it seems that people are not satisfied fully even with some really nice inverters. I would like a 1,500 Watt Pure Sine Wave Power Inverter to start with. If not, then 1000 Watts would be a nice little start for just researching currents on a 12v system.

I'd like to start small to get a feeling for solar systems, and buy a MorningStar ProStar 30, (1x) Trojan 31-AGM 100Ah Battery, and maybe (x2) 100 Watt Renogy Monocrystaline modules to start. Then I'd like to get a Pure sine wave power inverter, but If I'm going to buy one, I want to get a halfway decent one to start with, like either a 1000w or 1.5kW pure sine power inverter. I'd like to start by powering my quad core laptop and my Insignia 32" LED Full HD TV upstairs.

Q2. If I have (2x) 12Vdc 100Ah batteries in parallel, how many Renogy 100 watt panels will I need to charge them in 1 day?

Q3. If I have (2x) Renogy 100 Watt panels, that have an Isc Short-Circuit Current rating, and If I want to use an inverter connected directly to the panels, will the load be divided evenly between the two panels? If I have a 7 amp load, will each of the panels only share 3.5 Amps for each of the two panels?

**Specifications**Maximum Power: 100W

Maximum System Voltage: 600V DC (UL)

Optimum Operating Voltage (Vmp): 18.9V

Optimum Operating Voltage (Vmp): 18.9V

Open-Circuit Voltage (Voc): 22.5V

Short-Circuit Current (Isc): 5.75A

Dimensions: 47 X 21.3 X 1.4 In

Weight: 16.5lbs

Can you show me where a good decent Pure Sine Wave Power Inverter is or what it's name is? I've looked at Home Depot and Amazon Prime, and it seems that people are not satisfied fully even with some really nice inverters. I would like a 1,500 Watt Pure Sine Wave Power Inverter to start with. If not, then 1000 Watts would be a nice little start for just researching currents on a 12v system.

I'd like to start small to get a feeling for solar systems, and buy a MorningStar ProStar 30, (1x) Trojan 31-AGM 100Ah Battery, and maybe (x2) 100 Watt Renogy Monocrystaline modules to start. Then I'd like to get a Pure sine wave power inverter, but If I'm going to buy one, I want to get a halfway decent one to start with, like either a 1000w or 1.5kW pure sine power inverter. I'd like to start by powering my quad core laptop and my Insignia 32" LED Full HD TV upstairs.

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## Comments

5,182✭✭✭✭If you have them wired properly and they are the same amp hour and age battery, they will in a 24 volt string and they will for a long time in 2 parallel strings for a 12 volt battery bank. It doesn't work like that, if they are fully charged and you don't use any power it takes next to nothing, if you draw them down to 50% more than 4 on a sunny day. On a cloudy day and you've drawn them down 50% a huge amount... No one answer. You don't hook an inverter directly to panels. Most won't work at all with out a battery bank. No IMP? Our Sponsor has some of the best prices on

Exeltech inverters, They make a nice 1100watt pure sine, made in the USA for @$600.If that is too expensive Xantrex ProWatt 1000 gets pretty good reviews at amazon, I think someone here has posted a review of the 1000 or 2000 ProWatt inverter. Likely the best start is to buy or see if your power company has a Kil-A-Watt meter, and see what amount of energy these items use. Some new 32 inch TV's use <50 watts and your Quad core laptop likely runs around 120 watts max.

2 - 100 watt panels angled within 10 degrees of your latitude facing south should give you a usable 4-500watthours of power, so if my guesses are correct you could run your laptop for @4hours or your TV for 8-10. A single 100 amp hour 12 volt battery, will be drawn down near 50% so you could only use on sunny days, since you would be drawing it down to 50-60% State of Charge.

22✭Awesome. Thank You.

** KILL-A-WATT **

I will buy the Kill-a-watt meter from Amazon then, to get a better understanding of how much electricity (amps, watts, volts) my Laptop & 32" Insignia HDTV is using. Then I stand back and take a look at how many panels I'd need to power the things I'd want to power using Solar Power.

** NO Imp Rating **

As for the Imp, it seems people on Amazon have asked the question regarding how many amps (Imp) they are getting. There was a reply with a person that owns these panels and he/she said about 5.30 Amps (Imp).

** Solar Panels to DC-AC Power Inverter **

As for connecting a solar panel up to a DC - AC Power Inverter, it's very possible. I have several Buck, Boost, and even SEPIC Converters that will handle the 5+ amps coming off the panel(s). It will regulate the voltage to 14 volts. 14 volts because when there is a load, I want to make sure that with the voltage drop, it stays above minimum operating voltage in order to keep the power inverter running. I wouldn't be allowed to pull more amps then what the panel(s) can output.

** Buying a Power Inverter **

I'll take a closer look at the power inverters on NAWS. I'll also take a closer look at the ones on Amazon. Thank You for the help, very much appreciated.

140✭✭According to Renogy's data sheet for their 100W monocrystalline panels (PDF link), their Imp is 5.29A. Their Vmp seems a bit high for using a PWM charge controller (the Renogy 100W polycrystalline panels have a Vmp of 17.8V and an Imp of 5.62A, thus giving more charging Amps), unless Voltage drop due to wiring distance or high temperatures is an issue.

ETA: In answer to your question about how many 100W PV panels would you want to keep a 12V/200Ah battery bank charged, I would recommend four such panels. Here's the math:

(400W PV array * .77 derating factor) / (14.5V charging Voltage * 200Ah battery bank capacity) = 10.6% charging rate

The assumptions that go into this calculation are that, in general, you'll average around 4 hours per day of "good sun," and that your panels will produce about 77% of their rated power.

22✭So four panels, to charge a 200Ah battery bank, with 4 hours of good sunlight?

So that's 5A x 4 = 20A. 20A x 4Hrs would be 80Ah. That doesn't seem enough to charge 200Ah battery bank. I don't understand your math, or the terms your using. I'm new to solar power, but I do understand Amps & Ampere-hours. I'm also aware that I can't discharge the batteries to 0%.

140✭✭Keep in mind that it's best not to go below 25% depth of discharge (DOD) for a battery bank on a routine basis, in which case your system is only having to provide around 50Ah (plus a bit extra for inefficiencies) to your battery bank during the day. The "derating factor" refers to the fact that your panels usually won't produce their full rated power in "real world" conditions.

252✭✭I don't go below 50% ever or as stated by AT, more than 25% on a regular basis. It also should be noted that you will need to put 30% more amperage into the bank than you took out of it to get back your original state of charge.