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Sol-Ark 12k with 8 Trojan T-1275's series parallel 48v seeing different voltages on different batteries, ranging from 13.42v to 14.46v

Sun_Dried_Toad

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Sep 6, 2020
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I am very new to all of this, so forgive my ignorance. I am here to learn, and get more knowledgable about my system and solar and battery theory in general.

During my research (I have been researching for around 2 years, on and off) I came to understand that your cells should be pretty uniform in charge. so if we are concerned about individual cells in each battery that are inconsistent, it would seem if I have batteries that differ in voltage by as much as 1.1 volt, that seems bad.

My voltages are:
13.96 13.68
13.36 14.21
13.42 13.62
14.46 13.68

Total voltage, when measured across the whole bank of 8 batteries is 55.2v
total voltage, when measuring each of the 4 battery parallel banks is also 55.2v
All batteries are brand new. the first 4 were purchased about 6 months ago, but have just been sitting, unused, and not connected to anything until last weekend. last Saturday, I wired in the Sol-Ark and the first 4 batteries and connected a single load circuit to the system. the second 4 were purchased two days ago, on Friday. as soon as I got home with the newly purchased batteries, I tested them. all 4 showed 12.5 volts, which I thought was considered low or even dead? I figured since they are deep cycle batteries, perhaps just connecting them to the system and allowing it to charge them would straighten everything out. I disconnected the load circuit from the system the first night so there would be no drain on my new batteries until they had a chance to charge the next morning when the sun was up. when I got up on Saturday, I connected the load circuit, after the sun was up and powering the PV array and charging the batteries while providing full PV power to the load circuit. no power was drawn from the battery bank, since the Sol-Ark and PV array were on load priority, while simultaneously charging the batteries. this morning, I took voltage readings, and that is what I listed above. definitely higher, but I am still concerned about the variances.

the system ran all day yesterday fully charging the batteries. last night, there were no alarms for low voltage or power interruptions. we only have one load circuit on the system right now, since we are still testing and learning about it.
 
Last edited:
I have 8 T-1275 in a 4S2P configuration.

12V in series must be balanced prior to deployment and monitored for balance.

They all need to be individually charged to full @ 14.82V until current has dropped to below 2A.

Once balanced and placed in series, it helps a lot to install these:


You'll need 1 per 4S string.

You also need to learn this:

 
I have 8 T-1275 in a 4S2P configuration.

12V in series must be balanced prior to deployment and monitored for balance.

They all need to be individually charged to full @ 14.82V until current has dropped to below 2A.

Once balanced and placed in series, it helps a lot to install these:


You'll need 1 per 4S string.

You also need to learn this:

I do NOT miss doing acid Specific Gravity test.
 
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