AGM Pack Design

Hi All,

I've been given 12 x 12v, 120AH AGMs. Wanting to use them with solar at the farm.


Just after some opinions on best way to configure them.

I have a 48v charger/inverter (PIP-5048MS) already. Pretty happy with it but open to getting another type if better suited for task.

I could hook them up like this but suspect there will be another way to help them balance better?

Spazmor said:

Hi All,

I've been given 12 x 12v, 120AH AGMs. Wanting to use them with solar at the farm

Just after some opinions on best way to configure them.

Click to expand...

@Spazmore

Your configuration does not allow for a failure of any 1 of the batteries. You would have to disconnect the whole pack to replace any one of them.It alsoisnotreally optimal for balancing although Pb based systems don't require it so much. Nevertheless I do have a balancing system on my pack.
A better way of stringing the pack would be as following:



That way you can take one of the strings off line and service it while the other 2 are still working.

Balancing I accomplished with a self build Balancer setup with these modules.https://www.ebay.com/itm/1Pcs-48V-S...d-Batteries-/153328030808?hash=item23b3101458




And the bank with thermostatically and PWMcontrolled Server case fans.




Wolf

Connect the inverter to the positive pole of the top battery, and the negative to the bottom battery. That way the whole bank will balance a bit better.

SilverNodashi said:

Connect the inverter to the positive pole of the top battery, and the negative to the bottom battery. That way the whole bank will balance a bit better.

Click to expand...

That is certainly a good way to try to keep the pack equal.
In my case I opted for Heavy duty Buss cabled between all the negative posts on one side and the same on the positive side and drawing from the middle, both feeds going to a buss bar where all items are collectively supplying and or drawing.
I do have a equalization setup though as discussed and my batteries will vary by a 10th of a Volt every now and then but not for very long.

Wolf

Wolf said:

SilverNodashi said:

Connect the inverter to the positive pole of the top battery, and the negative to the bottom battery. That way the whole bank will balance a bit better.

Click to expand...

That is certainly a good way to try to keep the pack equal.
In my case I opted for Heavy duty Buss cabled between all the negative posts on one side and the same on the positive side and drawing from the middle, both feeds going to a buss bar where all items are collectively supplying and or drawing.
I do have a equalization setup though as discussed and my batteries will vary by a 10th of a Volt every now and then but not for very long.

Wolf

Click to expand...

This is an even better way of doing it. But keep all the cables between the battery banks and the busbars the same length.

Thanks so much Wolf,

Your system looks beautiful. It's a bit fancy!
I agree with you that design looks like it would balance better and allow for redundancy too.
I like it alot..





Are those voltage LCDs accurate in this configuration? It hurts my head to try to understand if the other batteries will affect the readings.


Also, I know PB is forgiving but, do the 4 batteries within series become unbalanced?
I was looking at balancing at the battery level with 4 of these https://www.aliexpress.com/item/bat...for-48V-battery-system-solar/32643622608.html

Final question if you don't mind, how have you joined the three packs where they combined onto the bus cables. What type of connection, crimps, terminal lugs with nut and bolt?

You generally balance la batteries by overcharcing Them. So as Long as you have the Charger correctly setup it Will work fine

Spazmor said:

Are those voltage LCDs accurate in this configuration? It hurts my head to try to understand if the other batteries will affect the readings.

Click to expand...

Actually they are quite accurate at least to the tenth of a volt. I did check them before using them against a reference voltage generator.
The battery voltage that theLED voltmeters show comes from a direct connection to the pos and neg of each battery. I don't have a picture of it but I did have a battery fail and the voltage of that battery was so far off from the others it was easily found and replaced

Also, I know PB is forgiving but, do the 4 batteries within series become unbalanced?

Click to expand...

There is a lot of information on that subject just look up AGM battery balancingand the results will educate you.
As daromer said

daromer
You generally balance la batteries by overcharcing Them. So as Long as you have the Charger correctly setup it Will work fine

Click to expand...

I was looking at balancing at the battery level with 4 of these https://www.aliexpress.com/item/bat...for-48V-battery-system-solar/32643622608.html

Click to expand...

I have that same style equalizer on my battery bank. Except I went anal and got three of them for 3 strings. I don't think that is necessary especially if you tie all the batteries together on the negativesas you see in my diagram.

Final questionif you don't mind, how have you joined the three packs where they combined onto the bus cables. What type of connection, crimps, terminal lugs with nut and bolt?

Click to expand...

Post a picture of the AGM battery you got or the part number and lets see what is available for a 3 parallel setup or what can be made.
In my case the batteries have a regular post and a threaded post. The regular posts I joined with a cable similar to this but with regular post terminals.



The rest are all homemade cables with crimp terminals and AWG 2 Cable.
The beginning of the bank



There where many changes made between that picture and now.



One of them is tapping the bank from the center of the battery bus bars andequal cable lengths on the pos and neg of the bank to the main distributionbus bar.

Wolf

These are the batteries I was given.
They're froma retired UPS. Old but didn't see much action so hopefully still have some useful life left in them. They've been holding a charge but I should do a capacity test on them.

I have some 4guage cable I was going to use. This should be ok at least between the batteries maybe x 2 for the bus cables? IDK is that's overkill. I'll likely have less than 1.5m bus cables.
Rated inverter power is 4.5kw / 48v = 94A

Spazmor said:

These are the batteries I was given.
They're froma retired UPS. Old but didn't see much action so hopefully still have some useful life left in them. They've been holding a charge but I should do a capacity test on them.

I have some 4guage cable I was going to use. This should be ok at least between the batteries maybe x 2 for the bus cables? IDK is that's overkill. I'll likely have less than 1.5m bus cables.
Rated inverter power is 4.5kw / 48v = 94A

Click to expand...

I had an 100ahAGM battery that was over discharged. Was at about 7v for memory. I recharged it very very slowly, took about a month, so as not to 'boil' and dry it out. Came back at about 80ah or so. It's about 8 years old.

It will be interesting to see what sort of life you get out of them.