Battery Order when Wire in Series ?

[Matrix]

I have my batteries in my 4 battery 24v battery bank numbered as to the order they are in connected in the series connection. (Trojan L16H-AC 435ah New as of Oct 16 2017)

Yet at full charge ... the 3 cells of the battery at the "end" where my final negative terminal is located consistently reads about 10 points higher than all the other 9 cells. At 85-90% charged today, cells 1-9 were all within about 2-4 points of each other - about 1.245 average, where as cells 10-12 (the last battery in series that becomes negative for the battery bank) read 1.255 average. I am still charging for the day, this is about 85-90% on the battery bank.

I know 10 points is not much, but it is odd that it is all on one battery where all the other batteries are so close cell to cell. The batteries are getting fully charged, and I did a full EQ last Saturday but it did not change the point gap of 10 points. I have been seeing this 10-15 point gap for the past few week or more on my regular Saturday SG health check.

Does this have anything to do with the order of the batteries? Would the battery last in series at the negative be being charged more than the other 3? Would it help to / Or could I safely move the batteries around in their order? would that help Adjust the SG of the lower batteries and better balance the bank?

[BackwoodsEE]

It makes absolutely no difference which order voltage sources (or loads, for that matter) are wired in series. So long as there are no parasitic loads anywhere in the series string tapping a partial voltage off of some but not all sources, the exact same current flows through each one.

[Mike90250]

It makes absolutely no difference which order voltage sources (or loads, for that matter) are wired in series. So long as there are no parasitic loads anywhere in the series string tapping a partial voltage off of some but not all sources, the exact same current flows through each one.

Absolutely correct. When was the last time an EQ was performed (if these are flooded) ?

[Matrix]

Flooded - Yes
EQ'ed - Last Weekend (7 days ago)
All connection cables at same length and battery cables to inverter are both same length

[sensij]

Air flow around the bank is worth considering. One end could be running warmer or cooler than the other. Are you measuring the temperature and compensating the hydrometer reading?

[Matrix]

Yes I compensate for SG with temp. Have 2 battery temps on the batteries, and they are fairly cool. 27.4* C. The batteries are in a battery box. Each has about 1" of space from the other, and about 2"'s from the side walls. There is 5"s of space above the batteries and an air vent directly above the battery bank (also a fresh air in at the bottom of the box).

I kinda figured The whole switching them around thing would not do anything. Guess it could not hurt though. But it does Seems kinda of odd that it is only one battery. .

[BackwoodsEE]

Air flow around the bank is worth considering. One end could be running warmer or cooler than the other. Are you measuring the temperature and compensating the hydrometer reading?

Excellent point. I was just thinking from a purely electrical perspective but this reminds us that the physical order of batteries in the string can make a difference for a different reason than circuit topology. Well worth checking into.

[Matrix]

Would it be possible to discharge the higher battery by itself? What would b a good quick source to discharge a 6v battery in a reasonable time frame. Either that or independently charge the other 3 up to the SG of the highest one. Would either of those options help anything?

[Matrix]

OK so I have EQ'ed ... and EQ'ed ... and EQ'ed. 32v and 60 min fixed setting. Trojan says for the L16H-AC the EQ should be 32.4, but I cannot set my charger that hi. But I have been monitoring the Highest and lowest cells. After 4 EQs it seems that all batteries have stopped going up in SG.

Trojan says 100% charge is 1277

After trying to get all cells SG to balance, and after what seems to be SG no longer rising, I am getting 1305 on the highest cell (battery #3 in series), and 1302 on Battery # 4 at the negative terminal, and 1299 on battery #1 at the positive terminal. BUT on battery # 2 ... on all 3 cells I am still about 10-15 points under. Cells are at 1295 / 1291 / 1290.

I know this is not what Trojan would call "out of range", but it also appears these 3 cells (all in the same battery) are NOT going to come up to the level of the other battery's cells.

Any ideas?

[Matrix]

Wrote this to Trojan. We'll see what they say:

Using L16H-AC for solar. 4 Batteries in series went into service Oct 16, 2017. EQ was first done a week later with AC charger. But In the past 3 weeks, SG in 3 out of 4 batteries have been lagging behind at 100% charge by about 15 SG points. Trying an EQ to raise all batteries to same SG, but having no luck on one battery.

Charger: Conext SW 4024 AC Charger: 32v 60 min Fixed EQ charge option highest setting for EQ. This is the highest volt setting that I have available with this charger.

Have done a carefully monitored EQ until SG appears to stop rising on all batteries. Have EQed 4 times monitoring SG each hour. Temps do not exceed 75* F (cool morning). SG has appeared to stop rising. Battery samples are as follows

20 min after last EQ
- Battery 1 - 6.88v: 1299 Center cell (positive to inverter)
- * Battery 2 - 6.88v: Lowest - 1295 / 1291 / 1290 All cells
- Battery 3 - 6.90v: Highest - 1305 cell closest to negative post
- Battery 4 - 6.88v: 1302 center cell (negative to inverter)

So I still have about a 10-15 point gap on one battery all cells. All 4 batteries are a month old.
- What can be done about this?
- Is this a problem?
- Are they still breaking in?

Thanks

[Higher Voltage]

You need a balancer. I can send a link. I have a similar problem. But I have 48 batteries.https://www.alibaba.com/product-deta...52ca246eQyhUMe

[Higher Voltage]

So I have them set up normally 12 12 12 12 =48v bank x 12 of these. Im going to try 12 12 12 12 12 12 12 12 12 12 12 12 = 12v . parallel. x 4 of these to =48v. The reason is batteries balance in parallel but not in series. Does anyone object?

[Sunking]

You need a balancer. I can send a link. I have a similar problem. But I have 48 batteries.https://www.alibaba.com/product-deta...52ca246eQyhUMe

You just bought a thingabobby that does nothing except make you wallet lighter and the sellers wallet heavier.

[Higher Voltage]

Are these balancers a power sucker? Similar units are used for Li Po s.

[Higher Voltage]

I checked my batteries when charging and they do not charge at the same V. The bank is the same V . Is there another solution ?