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razzle308 avatar image
razzle308 asked

AGM settings

Hi All.

Sorry for another setting question.
I have just had to replace my second 120ah AGM in 14months and short of getting 2 faulty batteries I need to know why. Both batteries had very little use. last one sat in my shed connected to the controller for 5 months and failed on my first camp 2 weeks ago.

I have a 75/10 set to agm and thought that was all I needed. Left it connected to a small panel thinking I was doing the right thing keeping it topped up.

What am I doing wrong?

Thanks, Darren.

battery chargingAGM Battery
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13 Answers
kevgermany avatar image
kevgermany answered ·

Does the panel get to a high enough voltage to start the charge? Needs to get to battery voltage plus 5.

Would help if you give the actual settings on the controller.

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ncgrechlni avatar image
ncgrechlni answered ·

This sounds odd, sorry for that and for sure this should never happen. Please, can you give us some details like the params from your controller and if possible about the history (charging)? Did you get load from the panel and may I ask, how much and does this fit the rating?

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razzle308 avatar image
razzle308 answered ·

There was no load attached. Just charging. Both batteries suffered a bad cell. Or cell collapse.

Below is the solar panel i am using just to keep battery stored. On the previous dead one i had a 180w 3 panel foldup.

screenshot-20211113-125817.jpg


screenshot-20211113-125817.jpg


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razzle308 avatar image
razzle308 answered ·

This is the panel for storage.

20211113-125340.jpg



20211113-125340.jpg (848.6 KiB)
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kevgermany avatar image
kevgermany answered ·

What batteries are they? Your settings show spiral cell. But this is not the common AGM.

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razzle308 avatar image
razzle308 answered ·

There are no other applicable options.

That is the only AGM. Then gel, lithium pzs victron deep discharge.

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kevgermany avatar image
kevgermany answered ·

Suggest you check with the battery maker and set the parameters manually. Absorption voltage looks to be on the high side. Float is the default victron for most lead types,

Are you in an area with high temps? This can kill them quickly.

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Just checked, some of the victron AGM gel batteries absorb at 14.2V.

In expert mode you can limit the absorption time. It should be set to adaptive, in any case.

Another thought: The mains chargers switch to a storage voltage if there's been no load for a while. Solar chargers don't, not sure why. If you know you're not going to be using the battery for a while, set float voltage to manufacturer storage voltage. Reset to normal float a few days before you're going to use the batteries.

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razzle308 avatar image
razzle308 answered ·

Not so plug n play :(

The info on my Force 120ah are 'standby use' (13.5-13.8v), 'cycle use (14.4-14.9v), current max (36.00A)

Not sure how to interpret these into float absorb bulk.

So it would seem this charger is not designed for continuous use?

4 comments
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The ideal charge current per parallel set is more like 24A.

Those voltages look like typical ranges for float (lower) and absorption (upper), but don't aim for the higher end of the ranges. Less is more.

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As in float =13.5, absorption = 14.4?

Could probably lower float further.


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kevgermany avatar image
kevgermany answered ·

If it helps, the victron multiplus units using dip switches generally set float at 13.8 and storage at 13.2 for all lead acid.

If you're going to use occasionally, consider float at 13.2, but increase to charge before you use the battery. But check with maker/supplier first.

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razzle308 avatar image
razzle308 answered ·

So i can see and understand the idea of setting a float program for sitting in the shed.

What is a good setup for camping given the short sun time and possibly intermitant sun?

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kevgermany avatar image
kevgermany answered ·

Whatever the manufacturer says for your batteries.

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razzle308 avatar image
razzle308 answered ·

So for camping....should i be bypassing the absorbtion phase. Should i set a higher bulk voltage before float kicks in?

Anyone able to help me that. Going away next week and i dont wanna chew another battery :(

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kevgermany avatar image
kevgermany answered ·

You can't set bulk. As it it charges, voltage rises until it reaches bsorption. Then it stays there. Until either max absorption time or tail current reached. Then it drops back to float.

So set absorption to the higher value.

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