AGM Battery Failure - Two Sets in Two Years

[sailjumanji]

Originally Posted by sailjumanji

Some of these aren't right. The solar controller had wires undersized by one gage. All other wiring in the boat was correct size.

Some of the Mastervolt charger voltages were off, or temp correction not working properly. But that was about 0.10-0.15 volts, so not sure how problematic that was.

Solar charge appears to time out absorption to float, which probably meant the batteries didn't get fully charged when we were at anchor. That repeated over several days and weeks, probably killed the first set of batteries.

We also deleted the VSR and replaced with a DC to DC charger, so the outboard motors only charge the start battery directly. And then the house batteries get a much more controlled three stage charge.

The boat only came with a shunt on the house battery, but it was hard to calibrate. Temp variations caused the zero to vary, which made the amps calculation vary. And with the VSR, the house loads were being pulled from both house and start batteries while system voltage above 12.8 volts, which made it impossible to monitor aH out. Now we have separated the bank with removal of the VSR, and added a Mastershunt on the house side to get very accurate amp, aH and SOC readings.

We also installed a Masterbus system so that all chargers and temps can be monitored to watch for irregularities. Also to be able to set voltages, absorption time, etc. Using a computer with Masteradjust software.

So now that we can see exactly what is happening with each charger and the battery bank, it appears that when the solar and shore power are not playing well together sometimes. For instance, when both on, the refrig load causes the solar to stay on float lights, but it is kicking up voltage when the fridge load kicks in. On shore power charge only, the MassCombi would cover the load while keeping voltage on float. Previously we couldn't see this.

We also added some passive ventilation for the battery compartment. And with the bus system we can check that each temp sensor is working, and can then check that voltage compensation is working.

There doesn't appear to be any smoking gun, but possible several issues that caused failure. Whether this fixed it is too early to tell.

I thought I posted all of this already, but not easy to look back using my phone screen.

Yep, I just see that I posted all of this on #198. I gotta learn to ignore questions from people that can't be bothered to at least read the last dozen posts for an answer to their questions.

[sailjumanji]

Originally Posted by tunnelvision

Considering the repeat failure you've experienced I would recommend doing a capacity test on the new batteries before installing them. This will tell you if they are healthy and give you a baseline for future testing.

True. And I've done the 20 hour test on the three old batteries. Its a PITA, just staying up that long, constantly adjusting draw up or down to stay at the 20 hr rate, recording amps and voltage, ... Times two batteries. I know why people don't do this routinely.

Mastervolt has a tester to do this automatically. I did the test using the inverter, light lamps on dimmer, etc.

[Sailing Ohm]

Originally Posted by sailjumanji

Some of these aren't right. The solar controller had wires undersized by one gage. All other wiring in the boat was correct size.

Some of the Mastervolt charger voltages were off, or temp correction not working properly. But that was about 0.10-0.15 volts, so not sure how problematic that was.

Solar charge appears to time out absorption to float, which probably meant the batteries didn't get fully charged when we were at anchor. That repeated over several days and weeks, probably killed the first set of batteries.

We also deleted the VSR and replaced with a DC to DC charger, so the outboard motors only charge the start battery directly. And then the house batteries get a much more controlled three stage charge.

The boat only came with a shunt on the house battery, but it was hard to calibrate. Temp variations caused the zero to vary, which made the amps calculation vary. And with the VSR, the house loads were being pulled from both house and start batteries while system voltage above 12.8 volts, which made it impossible to monitor aH out. Now we have separated the bank with removal of the VSR, and added a Mastershunt on the house side to get very accurate amp, aH and SOC readings.

We also installed a Masterbus system so that all chargers and temps can be monitored to watch for irregularities. Also to be able to set voltages, absorption time, etc. Using a computer with Masteradjust software.

So now that we can see exactly what is happening with each charger and the battery bank, it appears that when the solar and shore power are not playing well together sometimes. For instance, when both on, the refrig load causes the solar to stay on float lights, but it is kicking up voltage when the fridge load kicks in. On shore power charge only, the MassCombi would cover the load while keeping voltage on float. Previously we couldn't see this.

We also added some passive ventilation for the battery compartment. And with the bus system we can check that each temp sensor is working, and can then check that voltage compensation is working.

There doesn't appear to be any smoking gun, but possible several issues that caused failure. Whether this fixed it is too early to tell.

I thought I posted all of this already, but not easy to look back using my phone screen.

How was I wrong in what I highlighted?

-Your wiring was wrong (it doesn’t matter by how much it is still undersized and if you sized such an important wire wrong then I do have questions about other wiring). Why not eliminate any potential problem here and create the least resistance by actually upsizing your wire by two or three? Why play it so close?
..”The solar controller had wires undersized by one gage”

-charger didn’t get to correct voltages and didn’t maintain proper charging curve...”Some of the Mastervolt charger voltages were off” + “Solar charge appears to time out absorption to float” + “Temp variations caused the zero to vary, which made the amps calculation vary”

- shunt was either wired wrong or not working... “The boat only came with a shunt on the house battery, but it was hard to calibrate”

You said all of this yourself only with far more words. All of these could be a smoking gun (literally if your wiring is to small) but not getting appropriate charge voltages is your biggest electrical issue and again the reason for your repeat failures. If everything else was fine just this alone would kill you batteries.

The opinion of lack of research (which is overall the biggest issue I’d say) is based on the sum of the improper charge voltages/curve, wrong wire sizing, and thinking mastervolt designed them wrong not that you didn’t follow directions.
See I have data sheets for my batteries and I know that a difference of .15 volts would equate to ~12.5% SOC which is quite substantial. My data sheets also explicitly say what the charge curve should be and explicitly warn of damage by not following the charging curve. All of this falls under the category of research.

[sailjumanji]

Originally Posted by Sailing Ohm

How was I wrong in what I highlighted?

-Your wiring was wrong (it doesn’t matter by how much it is still undersized and if you sized such an important wire wrong then I do have questions about other wiring). Why not eliminate any potential problem here and create the least resistance by actually upsizing your wire by two or three? Why play it so close?
..”The solar controller had wires undersized by one gage”

- shunt was either wired wrong or not working... “The boat only came with a shunt on the house battery, but it was hard to calibrate”

You said all of this yourself only with far more words. All of these could be a smoking gun (literally if your wiring is to small) but not getting appropriate charge voltages is your biggest electrical issue and again the reason for your repeat failures. If everything else was fine just this alone would kill you batteries.

The opinion of lack of research (which is overall the biggest issue I’d say) is based on the sum of the improper charge voltages/curve, wrong wire sizing, and thinking mastervolt designed them wrong not that you didn’t follow directions.

I said I have issue with SOME of the things said. Overall, you are spot on. Except originally you said:

Yes, multiple I think.
-Charger wasn’t charging at approved manufactures settings. Wasn’t even programmable. Biggest issue yet somehow glossed over by 70% of ppl on this thread.
- shunt to tell exact draw and charge values was either damaged, improperly wired or of low quality.
- wiring wasn’t adequate to handle the charging values needed via solar (likely everything else as well)

Shunt wasn't damaged, the wires were the proper harness with twisted pair and shield, and it wasn't low quality. If anything, oversized shunt which caused difficulty measuring small variations, and acting like a thermistor with temp. I wonder how many people actually check their shunt with a clamp meter, and calibrate it? Almost everyone I talked with hadn't done it.

Wiring on the solar was borderline ok vs manufacturer spec. We were arguing over length of cable vs the length vs gage guideline by manufacturer.
And when we tested it, there was not excessive voltage drop. But Seawind sent upsized replacement wires just to be sure. Just to be able to put that potential issue behind us.

But my issue is the statement "likely everything else as well." And "(it doesn’t matter by how much it is still undersized and if you sized such an important wire wrong then I do have questions about other wiring)". We, Seawind and Mastervolt reviewed all of the wiring, lengths and sizes, and everything else was appropriate. Saying the boat likely has other wiring issues because of one wire, is taking it too far. And was opposite of what we actually observed.

Oh, and why don't manufacturers gage up one or two wiring sizes on everything? You know the answer to that - cost. And weight, and it's a PITA to deal with oversized wires. And if you are already below recommendations on voltage drop for critical equipment, why do it?