question

francesco avatar image

My Agm Camper life duration

Good evening, this is the story of my Agm battery for cyclic use.

We have been living in a camper for almost 3 years.

The battery is almost exhausted.

I mean, with loads of 2/4 amps it is still good.

But with a load of 15 amperes (C 0.15), it only returns 25/30 ah.

I took a test with the recently purchased victronenergy smartshunt.


Is this normal after just 2 years and 8 months of continuous daily use?

The battery has about 1000 light cycles.

It discharges daily at approximately 12.5 / 12.6v.

He only suffered 3 or 4 deep discharges.

It is always charged at 100% every day, from a 300watt panel with a 30 amper mppt regulator.

The charge is set as follows:

- maximum current phase

- absorption phase of 90 or 120 minutes at 14.5v

- floating phase at 13.7 / 13.8v.

- temperature compensation at -3mV / C / 2V (about -18mV / C)

The working temperature has always been between 15 and 30 degrees. So very good.

The charging parameters are correct right?

On the battery it is written to charge at 14.7 / 14.9v in cyclic use and 13.8v in buffer use.

But my cyclic use is very light, almost a buffer use.

So I decided that 14.9v is too much.

Also I have seen that charging at 14.5v, the tail current is reached at the same time as at 14.9v.

In few words, monitoring the absorbed amps, I noticed that 14.5v equals 14.9v.

So I preferred 14.5v because it generates less gas.

The battery is designed for 1000/1200 discharge cycles (70%).

It actually has less than 1000 cycles at 80% now.

ESScharging batterybattery capacity
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6 Answers
lehrling avatar image
lehrling answered ·

"The mppt voltage is measured on the battery poles."

Yes, but The MPPT is some distance from the battery - are you using any remote sensing for voltage?


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Hello

yes ... the controller is about 1.5m from the battery.

But I repeat what I have already written:

The setting is with boost at 14.5v (with temperature compensation).

I made many precise measurements with the tester on the battery poles in various charging conditions.

The tension is always right.

ON RARE OCCASIONS, WHEN THE CONTROLLER DELIVERS MORE THAN 15 AMPERS, THERE IS A 0.1V DROP FROM THE CONTROLLER TO THE BATTERY.

THEREFORE IT IS 14.4V INSTEAD OF 14.5V.

But in my opinion this is irrelevant.

Since in my climatic conditions, the battery ALWAYS reaches 100% charge.

Sometimes at 12.00, sometimes at 14.00, sometimes at 15.00 ... but it always manages to absorb 0.2 / 0.3 amper in floating.

This indicates a full recharge, from what I know.

klim8skeptic avatar image
klim8skeptic answered ·

End of life for a LA battery will be, when the battery's ah capacity falls to 60% of battery's nominal ah rating.

You will want to be precise, and measure your load, against the batteries published ah ratings.....

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Hello.

If you read my posts well, everything is written precisely.

I repeat: with a load of 15 A, it delivers 25 ah.

With a load of 2/4 A, it still looks useful, even if I haven't discharged it fully with small loads.

However, with a load of 15A, new should give 80 ah. Now she gives 25. It is 30% of original capcity. So she died.

I will use it until it fails even with small loads.

My question is whether his life was normal or not.

I repeat: 960 cycles at 80%.

Expected life from the manufacturer 1000/1200 cycles at 70%.

Batteries are consumable devices.

You use them, they wear, and they eventually fail to meet their specifications, then you then recycle them....

32 months of continuous use/cycling is probably a lifetime for your batteries.

Thanks for your opinion!!

Its the first experience and because of that, i ask....

Becouse i read online of solar sistems battery banks that last up to 10 years, i was worried.

Probably thei are differrert leaed acid battery, with hight performance....

Or a different use....

Tahnk you for clarification.

lehrling avatar image
lehrling answered ·

In your original post you asked two questions:

"Is this normal after just 2 years and 8 months of continuous daily use?"

"The charging parameters are correct right?"

I have been responding to your second question.

You are right to question and scrutinize your system to ensure it is right before you spend money on a new battery or batteries.

Not judging, just saying if this was my setup I would want to address a few of the basics first before blaming the short life on a poor quality battery.

Your starter battery could be taken right out of your solar system. If it is discharging, find and fix the cause. If it needs charging after some crazy long time sitting, use the charging system it already has - start the engine and let the alternator do it.

Where are you sensing voltage for your MPPT controller?



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Hallo and thanks for your opinion.

maybe I explained myself wrong ... the engine starter battery is perfect after 3 years. As new.

It is managed by the victronenergy Cyrix. And i disconnect it most of the time anyway.

My doubt is about the agm battery services.

IF THE DURATION OF 960 CYCLES AT 80% IS NORMAL. 2 years and 8 months.


The mppt voltage is measured on the battery poles.

I also put 16mmq cables to minimize the voltage drop. (The installator put 10mmq initially).

So with a setting of 14.5v, I measure 14.4 in case the controller loads 15/20 amperes.

But for 90% of the charging the voltage is perfect without any drop.

I AM ABSOLUTELY SURE THAT THE BATTERY HAS ALWAYS BEEN CHARGED. (it is sufficient to check that it does not absorb more amper at the end of the charge ... let me explain: if at the end of the charge, even by increasing the controller voltage by a lot, the absorbed current does not increase, and remains at 0.2 amperes, it means that the charge is totally complete).

Doubt can be an "overload".

A 120 minute daily boost at 14.5v may be too much if the battery is discharged at 12.6v, as in my case.

Maybe I should charge it as a buffer use.

Only 13.8v, without boost.


One last detail: the AGM swelled slightly ... but this happened at the beginning of its life.

lehrling avatar image
lehrling answered ·

"I have already written the temperature compensation. (-3mV/C/2V...around -18mV/C)"

Yes but you did not state what the the actual temperature compensation setting is, it won't be an around number. Mine is set to -30.00mV/C.

You are always close to 25C temperature anyway, probably won't matter much.

"Some periods it was used in parallel with a starter battery.

But not even this can damage a battery, since the parallel is an electrical condition of perennial balance. A battery in parallel is like a single battery to its own charging parameters. And in discharging, a hipotetic load, it is divided between the two batteries proportionally to the internal resistence of each one. To keep them always at the same voltage."

OK. I personally would not charge in parallel with a different battery in a different location.

What is draining your starter battery?


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hello ... it's not an "around" number ... I wrote -3mV / C / 2V.

it is the algorithm of my mppt controller.

So at 12v they are -18mV / C ... but at 14v they are -21mV / C.

I don't know if I've made myself clear ...


You are right about the parallel.

The best condition is that of identical batteries.

But this is because they have a similar life and the load is shared equally.

Different batteries mean that one is more stressed than the other ... but still less stressed than alone.

However the agm has never been used with the engine starter battery.

It has been used for some time with another "starter type" battery. And in the same location, at the same temperature.

The charging parameters were more or less correct for both batteries.

And in any case, most of the time only the Agm was used.

The engine starter battery is separated via cyrix relay.

I apologize for the bad English ... I help myself with Google translate.

Do you think it is too little 2 years and 8 months, 1000 cycles at 80% (very light cycles) ??

I was expecting a little more ....

I must say it was used every single day.

32 months = 960 days = 960 charges / discharges.

The manufacturer expects 1000/1200 cycles ... but heavier than my average use.

The decline has been in the last month ... and only with big loads.

In fact the datasheets predict a stable duration for 90% of life ... and then a very rapid decline all together.

francesco avatar image
francesco answered ·

Hello.

It is certainly not a top of the range battery.

Paid 190 euros.

https://www.accessoricaravan.it/products/batteria-radon-mastro-agm-100-ah-versione-bassa-ideale-per-caravan-e-camper#:~:text=BATTERIA%20RADON%20MASTRO%20AGM%20100%20AH%20VERSIONE%20BASSA%20IDEALE%20PER%20CARAVAN%20E%20CAMPER,-SKU%3A%2038270VCM&text=Imposte%20incluse.&text=Piombo%20purezza%2099%2C99%25%3B,di%20esalazioni%20e%20fuoriuscite%20acide.

Agm "master radon" 100 ah.

-I have already written the temperature compensation. (-3mV/C/2V...around -18mV/C)

-yes, of course degrees Celsius, I'm Italian.

-the current tail is not a parameter taken into account by my mppt controller.

I meant that, looking at the charging amperes in the absorption phase, both at 14.5v and at 14.9v, the charging evolves in the same way. And it always comes to an end of charge. (in few words the battery gets to absorb 0.2A at the end...these indicate a full charge).


I don't think 14.5 or 14.9v makes a difference in battery life. If this was loaded 100% every day.

Some periods it was used in parallel with a starter battery.

But not even this can damage a battery, since the parallel is an electrical condition of perennial balance. A battery in parallel is like a single battery to its own charging parameters. And in discharging, a hipotetic load, it is divided between the two batteries proportionally to the internal resistence of each one. To keep them always at the same voltage.


Anyway ... Did it last too short? (about 1000 cycles at 80%).

This is the screenshot of the Smartshunt voltage at the end of the test, after about 25 ah....2 hours with C15A (C0.15).

With 2/4 A load,it still last notmally.

screenshot-20210119-220240.png

Super cheap Starter batteries last me even less in the same conditions. 600 cycles.

Next battery will be probably a FIAMM AGM,or VICTRONENERGY AGM or NDS AGM


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lehrling avatar image
lehrling answered ·

What battery is this?

What is your tail current set to?

What is your actual temperature compensation setting value?

Working temperature you quoted is degrees celsius correct?


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