Lead vs load question

[Gdwats]

If i have 2 batteries and plan on a third, do I designate first battery as the lead or primary battery, then hook subsequent like batteries to it? I get that i think. But, ehen hooking up an ac inverter, can i use the second, then 3rd battery, when I get it, to attach the inverter or must I use the lead battery for that too? That is my real question..

[Mike90250]

The smartgauge website has illustrations on how to properly connect 3 batteries, (wire all in parallel, then connect diagonally)
http://www.smartgauge.co.uk/batt_con.html (example #2)

[Gdwats]

Wow, Mike. That is a very useful link. Think ill use method 2 for now, and hook the inverter up on the same diagonal as the controller.
Thanks a bunch!
Greg

[ButchDeal]

How old are the two batteries you have now? And what size are they?
are all three the same?

[Gdwats]

One is about a week old, the other is now 1 hr in use after reaching 14.3v. They are both 55ah sla deep cycle from ChromeBattery. haven't hooked them together yet as I need to get a cable. From that handy link I read that 35 mm or better Copper cable is best I think they said. Do not have a third battery yet but anticipate it.

[ButchDeal]

One is about a week old, the other is now 1 hr in use after reaching 14.3v. They are both 55ah sla deep cycle from ChromeBattery. haven't hooked them together yet as I need to get a cable. From that handy link I read that 35 mm or better Copper cable is best I think they said. Do not have a third battery yet but anticipate it.

Why keep buying small batteries? You could have just purchased a 100ah or 200ah and not have to worry about jumpers, balancing etc?

[Mike90250]

Why keep buying small batteries? You could have just purchased a 100ah or 200ah and not have to worry about jumpers, balancing etc?

Awww, where's the fun in that?

But be aware, your solar has to be matched to your batteries. Too large of a battery bank, and it may take too long to recharge them, and they fail early.

110 ah of battery needs about 11A from solar, to recharge. Add another battery, (165ah) and you need 17A of actual solar (which is about 15 or 20% less than the label on the panel - you would need 21A (rated) to deliver 17A of solar into your 165ah of battery. Any less and you risk sulfating the batteries

[Gdwats]

Thanks Mike. Am stopping at 3 panels and 2 55ah.

[Gdwats]

Why keep buying small batteries? You could have just purchased a 100ah or 200ah and not have to worry about jumpers, balancing etc?

Because I can't lift or move heavy batteries....bad back. That's why.

[ButchDeal]

Because I can't lift or move heavy batteries....bad back. That's why.

hm. Is this a portable system? so you are carrying them separately?
A single 110ah battery would weight in a bit less than two 55ah batteries.
Or you could get two 6V 110ah batteries, to avoid the parallel.

[Sunking]

Because I can't lift or move heavy batteries....bad back. That's why.

Then why are you buying 12 volt batteries.? Batteries are not 12 volts, they are 2 volts. Never Ever parallel batteries. If you need 150 AH buy 150 AH batteries, like a pair of 6-volt 150 AH batteries wired in series.

[Gdwats]

I can't lift them.

[Gdwats]

Ok, all hooked up with 2 55ah sla deepcycles, 2 renogy mono 100W panels(3rd on the way), a 20A mppt, and 500W inverter. Batteries were both charged to 14.2v before hooking together, and after. Question is, how low should I let the voltage drop before disconnecting the inverter? At 12.4 now and 12.2 is my shut off assumption till next full charge?

[NEOH]

Ok, all hooked up with 2 55ah sla deepcycles, 2 renogy mono 100W panels(3rd on the way), a 20A mppt, and 500W inverter. Batteries were both charged to 14.2v before hooking together, and after. Question is, how low should I let the voltage drop before disconnecting the inverter? At 12.4 now and 12.2 is my shut off assumption till next full charge?

Yes, shutting down at 12.2 Volts could be OK.
But it all depends upon the load on the inverter when that voltage reading was taken.
Auto-shutdown @ 12.2 Volts could be correct.
You have a 500 watt inverter, but I have no idea what the load is.

12.2 Volts measured with NO Load and rested for 24 hours means approx 60% Charge Remaining.
12.2 Volts measured with a LOAD means, greater than 60% remaining - which is a very reasonable cut-off.
The Battery Voltage will rise over night.
Measure the voltage in the morning before the PV turns ON
Then you can better "guestimate" the State of Charge remaining.

[NEOH]

I can't lift them.

Can you lift a 13 Pound battery ?

EXAMPLE: Here is a 2 Volt 100 AH Cell @ only 13 lbs ...
https://www.alibaba.com/product-deta....26b131bYvsY4I

And a 200AH 2 Volt Cell weighs only 30 lbs each.

While your 55AH 12v AGM's weigh 39 lbs EACH.

You connect 6 Cells in SERIES x 2 Volts each = 12 Volts.
Cells in series are much better than batteries in parallel.
Maybe, next time?