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dan avatar image
dan asked

Why did my battery die

Why did my battery die.

I'm asking this question to find out what went wrong and how to correctly maintain solar charging of AGM VRLA type batteries in a mobile scenario.

Setup purchased Dec 2018 (14 months old)

2 x HGL-120 -12 PRO SERIES EXIDE VRLA AGM.
1 x Victron 75/15 mppt
1 x Victron battery temp sence
1 x 100 watt solar panel.

Batteries are in parallel, charge cable from mppt is connected to + on one battery and - on the other.
The mppt settings from new have been, absorption 14.3v float 13.7v. Having some concerns over this near default setting about 3 months ago I changed these and made a new user defined standby setting which allowed the battery to achieve a float without major charge. info here

https://community.victronenergy.com/questions/29395/firmware-update-v142-causing-different-charging-ti.html?childToView=29432#comment-29432

The van has been used very little, 3 camping trips, a week each time and 10 other times overnight all with minimal discharge from a 45 watt fridge and a few other small gadgets.
January last was the third week trip to forster, it's then I noticed my discharge was more than normal down to 12.7v and charging back to float was hard to achieve, a bit concerned I started to wonder what was happening.
today with settings on default the voltage wouldn't rise above 14.1v and bulk charged up to 6 amps through the day, after chasing symptoms on line I physically checked the batteries and found the one without the victron temp sencer was hot hot hot, cooked. The other with temp sence was warmer than normal at 35 degc, I suspect it's been warming by leaking power to the dying one, I disconnected the batteries and checked voltage cold battery 13.19v the hot one was12.9v and checked an hour later 12.6v.

I must say I have spent hours of research trying to do everything for this not to happen and here I am, so I ask the question why did my batteries die.


MPPT ControllersESSBMV Battery Monitorbattery
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6 Answers
christyler avatar image
christyler answered ·

Are the battries the same age ? We're they both installed at the same time.

You might be lucky, the bad battrie may not have killed the other one yet

Why is there no battery protect in your system to prevent them discharging to the extent they die.

100w solar panel is not enough to maintain 240ah of battries. You could add a cyrix to also charge from the engine.


Just my thoughts

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dan avatar image dan commented ·

They where purchased the same time, the 100w solar panel produces a 100w, when I'm camping for a week I add a portable panel which together produces 200w, the 100w panel is enough to keep the batterys maintained and run a fridge easy unless it winter and cloudy, I purchased 2 batteries to keep discharge levels at a minimum, I only run a 45w fridge and a few rechargeable items in the day time.

The mppt has a low battery protect, they have not died from deep discharge.

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dan avatar image dan commented ·

Most of the time it's not power loaded, just waiting to be used and when I use the fridge with single 100w panel when I'm traveling, any discharge is recovered the next day once the load is disconnected and ive reached my destination.

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spirou avatar image
spirou answered ·

12.7 is not a deep discharge even with likely higher resting voltage of AGM or did you mistype 11.7?

Anyway, even a sealed battery can dry out. They can also suffer structurally from vibration which can cause an internal short circuit and an event you saw. Happened with a gel battery I had a few years ago.

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dan avatar image dan commented ·

No 12.7v is not deep discharge it was just more than the normal discharge from running a 45w fridge overnight.

Mostly traveled on tar and are in a toyota surf no vibration issues, I have felt the sides of the batteries though and noticed swelling between the cell wall joins.

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dan avatar image
dan answered ·

I contacted Exide this morning, they are replacing both batteries. Wow.

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dan avatar image
dan answered ·

I have received 2 x new batteries.
originally I set my old batteries on Victron default but not wanting to have such a high charge for a battery that sits on the shelf most days, I decided to lower the charge and started with just the float v, absorption @13.8v and float @13.5v. They arrived @12.85v.
After checking over 3 days of charge it's clear that the daily resting voltage has risen higher every charge day.
1st 13.09v, 2nd 13.14v, thrd 13.16v.
if 12.80v is 100% charged then the battery is being overcharged.
Today is the forth day and I have made a new setting (Maintenance)
Absorb 13.20v
Float 13.10v.
Equalize 14.00v every 30 days.
I will keep records of its progress.



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spirou avatar image spirou commented ·

I have the exact opposite problem. When the van is parked for days the min voltage keeps dropping at about the same rate as yours rises. And there's only a 0.01A costant draw which should be covered any day of the year with 320Wp.

Haven't found a formula to keep it steady yet...

But it's also true we use it a lot more than 3-4 times a year so the batteries do get somewhat regular exercise and storage mode isn't that much of an issue. Just a niggling feeling to find a right charging recipe.

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porcini avatar image
porcini answered ·

AGM Batteries need 14,6-14,8V absorbtion in a PV system. This is often done wrong to prevent the battery from drying out, but it is the main reason AGMs die early.

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Warwick Bruce Chapman avatar image Warwick Bruce Chapman commented ·

Victron enables storage mode by default when you select AGM in Ve Configure. Is that still fine because there is the occasional full voltage absorption charge?

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porcini avatar image porcini Warwick Bruce Chapman commented ·

As long as the battery is fully charged storage mode is fine. But this is only useable when a multi is connected to the grid for a long time. PV only does not need this since it doesn't charge at night.

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dan avatar image dan commented ·


Yes, first timers like myself need to know that these mppt battery default settings are for daily working batteries.

a holiday camper being used 3 or 4 times a year sitting fully charged in the driveway receiving the default daily dose of overcharge, will soon die.




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dazey77 avatar image
dazey77 answered ·

Can you post a photo of your battery wiring? Need to resolve why one battery has had a harder time than the other. Could have been a faulty battery, could be wiring.

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