Diy solar system

Hi,
I was wondering about what battery you guys would recommend for a small 12 volt system
I already have 2 100 watt solar panels and a charge controller
Also what 1000watt inverter you would recommend for the system. (240volts output on the inverter would be useful)
I live in Ireland if thats useful to know
Thanks Ben

Depends on your purpose.
For off-grid living, one rule of thumb is to have enough battery for 3 days without sun.
For fixed-orientation solar panels, expect 5.5 effective hours of sun per day (maybe less on the Emerald Isle)
Panels are rated for watts STC (standard test conditions of one full sun and 25 degrees C), while realistic PTC performance test conditions of elevated panel temperature and slight breeze might be 80% of that.

You have 200W STC, expect 160W actual output, 880 Wh/day. For 3 days that comes to 2640 Wh. At 12V, 220 Ah usable capacity.

I'm familiar with lead-acid batteries. The other guys can recommend Lithium, which (for most chemistry) requires a BMS battery management system. What battery types does your charge controller support? Does it have a temperature sensor, which is needed for best battery life?

Although flooded wet-cell (i.e. golf cart or forklift) batteries are half the price, they require more maintenance. I prefer AGM, absorbed glass mat. The ones I've used are SunXtender, and can handle 5000 discharges of 20%, 1000 discharges of 50%. Let your worst-case 220Ah consumption be 70% of a 314 Ah battery. Here's something close, 295 Ah @ 72 hour discharge rate:



At $900, I'll bet that's more than everything else you bought.
It is also heavy enough to require truck shipping. Paralleling smaller batteries, or connecting two 6V in series, you may get more choices and cheaper shipping.
I don't know what varieties are available locally.
Maybe, you can find some good used gel-cell or AGM that came out of a large computer UPS.
Of course, if you decide your needed capacity is much lower you can get by with as little as a used car battery. Especially if you're just going to run a microwave occasionally while the sun shines.
If you are pumping water, the goal is to pump while the sun shines and not store the power in a battery.

Yeah
That battery is definitely more than everything I have got so far.
My charge controller does have a temp sensor connection though it doesn't come with the probe.....I probley should get the probe for it tbh (It's a 30amp renology wanderer charge controller. It supports sealed,gel,lithium and flooded batteries)
I don't plan to use the system at night anyway...

BenCos18 said:

Yeah
That battery is definitely more than everything I have got so far.
My charge controller does have a temp sensor connection though it doesn't come with the probe.....I probley should get the probe for it tbh (It's a 30amp renology wanderer charge controller. It supports sealed,gel,lithium and flooded batteries)
I don't plan to use the system at night anyway...

Click to expand...

Well, you have to consider how much power draw you plan for and when. Then a battery can be sized accordingly. What do you plan to operate with the system?

As for inverter, true sine wave is the way to go unless your load is going to be OK with "modified sine wave" which is just a square wave with a flat spot at the zero crossing.
If you're starting a motor, induction motors require surge current many times their operating current, while others start more softly.

Also, do you have expansion plans, or is 200W PV, 1000W AC the most it will ever be?

Hedges said:

Well, you have to consider how much power draw you plan for and when. Then a battery can be sized accordingly. What do you plan to operate with the system?

As for inverter, true sine wave is the way to go unless your load is going to be OK with "modified sine wave" which is just a square wave with a flat spot at the zero crossing.
If you're starting a motor, induction motors require surge current many times their operating current, while others start more softly.

Also, do you have expansion plans, or is 200W PV, 1000W AC the most it will ever be?

Click to expand...

I don't plan to go over 1000watts for the inverter and the PV will most likely be staying at 200watts tbh.
Also thanks for the help btw

I doubt I'll pulling more than 700- 800watts from the inverter. Though if I was very short of solar I could add another 2 panels to the system.

Hi Ben , I would most likely consider Victron products. They are just across the pond from you and should be reasonably priced. They offer such a fast range of products for future expansion. Look at the Victron Phoenix 12/1200 50Hz Pure Sinewave Inverter. With an added Bluetooth module you can monitor it on your phone / pad. I have been using this product for over a year w/o any issues. Also have a few other Victron products in my setups.

ok
I will have a look at them then
thank you

BenCos18 said:

ok
I will have a look at them then
thank you

Click to expand...

Sorry for the typo : vast range

no worries xD

BenCos18 said:

I doubt I'll pulling more than 700- 800watts from the inverter. Though if I was very short of solar I could add another 2 panels to the system.

Click to expand...

You still have to project how many watt hours you'll be drawing per 24 hour day, how many during the night, how much before letting it sit and recharge.

You will generate about 180 watt hours per hour around noon, half that at 9:00 AM and 3:00 PM.
The inverter will draw 1000 watt hours per hour while operating, so you get one hour of inverter operation on an average day.

If you plan to run the inverter only at night (e.g. run 100 watts of LED bulbs all night), you will draw 80 Ah from the battery. If lead-acid deep cycle, should get at least 160 Ah battery and plan to replace every 3 years. If lithium, a bit smaller and probably replace every 10 years.

That would still cost you $490 for my favorite AGM. The guys who use Lithium may have some suggestions which cost less.

https://www.solar-electric.com/concorde-sunxtender-pvx-1530t.html

If you plan to power a 1000W microwave oven for 5 minutes at a time during daylight hours, that is only 85 Wh per cycle, 7 Ah. It will take 30 minutes to recharge at noon, one hour to recharge at 9:00 AM or 3:00 PM, and you can do up to 11, 5 minute cycles per day. Battery needs to be at least 14 Ah. A 40 Ah deep-cycle battery may last 3 years. For this sort of shallow-cycle usage I would suggest starting with a used car battery. Get one for free that still has good voltage. $0 for now, after some experience you can select a new battery.

Here's a random brand 12V 33 Ah AGM battery for $73


What model battery charger do you have? Is it MPPT or PWM? If MPPT it will harvest more power from the panels and can accept 50 to 80V input. PV panels are getting to be the lowest cost part of the whole system, so you can add some to get more watt hours to use during the day without buying a larger battery to store more. Just need to stay within maximum charge rate of the battery, and maximum PV Isc (short circuit current) rating of the charger.

Hedges said:

You still have to project how many watt hours you'll be drawing per 24 hour day, how many during the night, how much before letting it sit and recharge.
If you plan to run the inverter only at night (e.g. run 100 watts of LED bulbs all night), you will draw 80 Ah from the battery. If lead-acid deep cycle, should get at least 160 Ah battery and plan to replace every 3 years. If lithium, a bit smaller and probably replace every 10 years
What model battery charger do you have?

Click to expand...

it's a pwm renology controller
I don't plan to use the system at night very often tbh.
I doubt I'll be pulling more than 700-800 watts from the inverter very often tbh.

I might get a mppt controller in the future though I'll get the system working first......
edit fixed typo (should say system not server lol)