MultiPlus test lead to Battery corundum - failure - I am stumped

[Yoda]

Well I got the batterys out - what the heck was I thinking - dang they are heavy. I actually cut the side of the battery box so I could tip them in and out. Should have don than to start. Switch is totally buggered up so I removed both. It appears I tried to move it the wrong way - was buried behind the battery box.

The switches I took out are the two lower ones centered in the picture. they were tied to the batterys. I then tied the power in cables directly to the power bar above. Its easier to remove a battery cable, then fight the buried switch. Tomorrow I will service the batterys (clean, check water level,etc) and put them back, wire up, plug the trailer in and do a full equalize and charge. Then run my test again. I will also lower the cut off voltage to 11.5 and see what happens. I just need to drag 200' of cable through the window and across the drive and plug into my desk top. I will also double check the charging parameters. I need to put the batterys back first as the multiplus needs power to program.

I will take specific gravity before and after, noting battery and cell.

And as I now have 2 short 4/0 cables I may use them for the series connections replacing the 2/0. Just might make a difference in the voltage drop. Busy day tomorrow. On edit - they weren't 4/0 I had used 2/0 to do all the battery connections to the power in bar

Keith

[Yoda]

Update -Success reran test after resetting low voltage cut off to 11.3V
Here is what I did. Crown recommended Equalizing the battery bank for 2 to 3 hours. I was able to do 2 One with the multiplus and one using the solar chargers. The Multiplus would not do a second equalize about 1/2 hour after the first ended - it indicated starting, but never went into the equalize mode. That when I set the MPPT to do it.

So first question - why would the multiplus not do a second manual equalize? Battery voltage was 13.6 and battery temps cool - 67F

From Wednesday until today I let thing sit on the solar for a few days.

Today I had time to run test – it actually worked.

I started at 12:40 Solar MPPT's were on float with battery bank showing 13.64V I turned the solar off – battery draw was 14W (trailer safety sensors, etc) I wanted to let the batterys sit for an hour When I went inside to do ither things at 12:45 voltage was 13.29

Battery drain during this time was a constant 14W

The Test

Before SG readings

1:45 Took first SG readings Voltage as I started the readings was 12.77
Batt1
12.65, 12.70, 12.65
Batt2
12.65, 12.65, 12.65
Batt3
12.65, 12.65, 12.70
Batt4
12.65, 12.70, 12.75

Voltage before turning on inverter 12.7V

Test
2:02 inverter on/coffee on 11.9V Power draw 88 amps 960W Is this 0.8v amount of voltage drop normal ?
2:04 11.8V
2:06 11.7V
2:08 11.73V – voltage appeared to be stabilizing , or even creeping up. Power draw constant 88.2A
2:09 11.75V
2:10 11.76V
2:11 11.77V
2:12 coffee pot ended brewing cycle Battery bank voltage jumped to 12.26V 0.49V increase

Second battery readings after test About 2:15

Batt1
12.5, 12.6, 12.6
Batt2
12.65, 12.65, 12.6
Batt3
12.6, 12.6, 12.55
Batt4
12.6, 12.6. 12.55
Done with SG readings at 2:26 Voltage 12.5 with 14W drain Overall SG dropped 0.05 to 0.1 per cell during the 10 minutes at 88 amps max drop was 0.2 Battery 4.

Turned solar on. Both on bulk voltage initial jump to 13.3 Afternoon sun. Later 3:13 13.4 I confirmed the bulk/absorption setting is 14.5V – but sun is just not strong enough right now to reach 14.5V recommended bulk/absorption rate and I was tired and not wanting to drag out the power cord.

Ill check in the morning to see how the draw down overnight is at the typical 14w usage.

So do these numbers look OK?

Thoughts?

Keith

[howson]

Yoda -- is this what you did to get into "Equalisation" mode? Victron's manual seems to imply it will only run for one hour...perhaps cycling the unit off (wait a few moments) and then back on before attempting a subsequent cycle would help.


There's a step--by-step process in par 3.3.3 Activating equalisation or forced absorption

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The voltage drop while under load is not unusual.

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In post 7 we established an approximate 300 minute run time to full discharge at your test load of about 88 amps. So 30 minutes represents 10% of SoC, right? Breaking it down further, .33 per minute is consumed at an 88A load rate. So approximately 3.33% was consumed in the 10 minute test. That's such a small amount it would be hard to know if the results measured are correct. The small voltage drops look like what could be expected.

I'd look to construct a test that would result in a 50% SoC (or "DoD" as Trojan puts it in their chart). As annotated previously, that's ...Two batteries in series, the assumption is 5.82 x 2 = 11.64v at 50% SoC (or DoD).

Remember as you continue to read that I'm not a battery expert nor have I ever tried a test on wet-cell batteries. The following is a hypothesis based on what I've read and learned.

Here's what I'd try. The Trojan spec sheet shows a battery should sustain a 100A load for 106 minutes to full discharge. Since you have two sets in parallel, that should double the run time, or 212 minutes to full discharge. So to get to 50% DoD, run a test designed to last 106 minutes @ 100A load in Inverter mode (so the Multiplus does not switch to Charge mode upon test completion). When the test is complete let the batteries rest for about 30 minutes (or more). The expected voltage level of the batteries is 11.64 (again, as previously documented that's a 50% DoD). Leave solar off so it doesn't confuse the results.

Howard

[Yoda]

Yoda -- is this what you did to get into "Equalisation" mode? Victron's manual seems to imply it will only run for one hour...perhaps cycling the unit off (wait a few moments) and then back on before attempting a subsequent cycle would help.


There's a step--by-step process in par 3.3.3 Activating equalisation or forced absorption

----------------

The voltage drop while under load is not unusual.

---------------

In post 7 we established an approximate 300 minute run time to full discharge at your test load of about 88 amps. So 30 minutes represents 10% of SoC, right? Breaking it down further, .33 per minute is consumed at an 88A load rate. So approximately 3.33% was consumed in the 10 minute test. That's such a small amount it would be hard to know if the results measured are correct. The small voltage drops look like what could be expected.

I'd look to construct a test that would result in a 50% SoC (or "DoD" as Trojan puts it in their chart). As annotated previously, that's ...Two batteries in series, the assumption is 5.82 x 2 = 11.64v at 50% SoC (or DoD).

Remember as you continue to read that I'm not a battery expert nor have I ever tried a test on wet-cell batteries. The following is a hypothesis based on what I've read and learned.

Here's what I'd try. The Trojan spec sheet shows a battery should sustain a 100A load for 106 minutes to full discharge. Since you have two sets in parallel, that should double the run time, or 212 minutes to full discharge. So to get to 50% DoD, run a test designed to last 106 minutes @ 100A load in Inverter mode (so the Multiplus does not switch to Charge mode upon test completion). When the test is complete let the batteries rest for about 30 minutes (or more). The expected voltage level of the batteries is 11.64 (again, as previously documented that's a 50% DoD). Leave solar off so it doesn't confuse the results.

Howard

Yep that is what I did to equalize. On edit I did it from the touch 50 in charger only mode and not from the pannel as 3.3.3 indicates. I should hear from Crown on Monday. I suspect he will want a deeper equalization as he wanted 3 hours. One added thing. I have 100% SOC set at 12.7V per Crowns information sheet sent to me. At end of test it showed 96%
Crown's sheet
ProperSetUpCareSLI.pdf

Also a handy test reporting form
Test Inspection Form_RE.pdf