question

piet-hein-van-asselen avatar image

Keep charger on or of when batteries under small load?

Dear all,


I am wondering:

Regarding what i read and hear the best to do with (in this case) AGM- deep cycle and super cycle batteries is following, in short:

- Always after use charge battery to full and after that, disconnect charger.

- If not used a fully charged battery for a period: After 1 or 2 months charge batteries again for maintenance purposes and to make sure a complete charge cycle is made.

- Do not interrupt charge when charging a fully charged battery, so do not charge batteries if not necessary and when it is not possible to finsih a complete charge cycle.



In my case:

I have a color control connected to a multiplus 12 volt, connected to 2 x 230 Ah in parallel.

The system can be monitored by the gsm module, so i have a constant network connection. Power drain in standby is around 0,2 amps due to data connection etc. When i use remote console, power drain is around 0,3-0,4 amps. So in other words: i am superslowly draining the batteries.


Question:

Do i keep the charger on or off when in standby? For my understanding, it is not very healthy to keep a charger always on whe u store batteries, even not when it has storage mode (see above for my understanding)

But in this case i am slowly draining the batteries, so is it better to leave the charger on when i am not on the boat for like 2 weeks?


For what i do now when i leave the boat:

I charge the batteries to 100 percent. I keep the color control online. After 2 weeks, the day before i go to the boat, i turn on the charger remotely.


Is this the best thing to do?


Best regards, Piet

MPPT - Solar Charge ControllerMultiPlus Quattro Inverter Chargerbatterycharger
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I don’t know where those rules come from but I don’t understand them.

There should be no issue at all interrupting a battery charge cycle - they’re analog.

4 Answers
Alexandra avatar image
Alexandra answered ·

@Piet Hein van Asselen

You do not mention what charger you have on your batteries, this may help with a better explanation however the book below is good reading if you are interested in taking care of your bank better. It explains in plain language what causes premature ageing in lead based batteries.

https://www.victronenergy.com/upload/documents/Book-Energy-Unlimited-EN.pdf


If you are leaving the inverter in standby however you may want to check the storage option then your battery will be "refreshed" every now and then (I see you got that in on of your previous replies). If you see how the charge graph in ve config changes when you check it you may get a better picture of what will be happening while you are not on the boat.

1618315169432.png

But for the most part even on float or storage service you will not find many AGMs that can do more than 3 years without having to be replaced no matter what you do. AGMs are fickle things even sitting by themselves with nothing attached they self discharge and sulfate anyway.


The idea that batteries cannot be left on charge is because it can cause off gassing and the battery to boil off its liquid and dry out from that, (this is for not so clever battery chargers that pump in the amperage regardless of SOC), but on float service this should not happen as it will be putting only one or two amps (depending on capacity) to keep it from self discharging as well as your parasite loads. Dry batteries are a bigger problem if you have sealed maintenance free ones. But if you don't you still need to check fluids as a regular maintenance thing anyway.


1618315169432.png (9.4 KiB)
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Thank you for your explanation and the link. I will look into that. Very usefull!


The charger i use is actually the multipluss charger part. In this case multiplus 12-3000, but also winderig for other multiplusses.

Last question; i dont understand whatcyou mean with this:



"But for the most part even on float or storage service you will not find many AGMs that can do more than 3 years without having to be replaced no matter what you do"

I have Victron AGM super cycles. I hope i dont have to replace them after 3 years???


Thanks in advance for the reply!


Best regards, Piet


Alexandra beantwoord · 3 dagen geleden EXPERT ANSWEREXPERT ANSWER


@Piet Hein van Asselen

You do not mention what charger you have on your batteries, this may help with a better explanation however the book below is good reading if you are interested in taking care of your bank better. It explains in plain language what causes premature ageing in lead based batteries.

https://www.victronenergy.com/upload/documents/Book-Energy-Unlimited-EN.pdf


If you are leaving the inverter in standby however you may want to check the storage option then your battery will be "refreshed" every now and then (I see you got that in on of your previous replies). If you see how the charge graph in ve config changes when you check it you may get a better picture of what will be happening while you are not on the boat.

1618315169432.png

But for the most part even on float or storage service you will not find many AGMs that can do more than 3 years without having to be replaced no matter what you do

Alexandra avatar image Alexandra piet-hein-van-asselen ·

@Piet Hein van Asselen

I cannot say from experience with the Victrons as I have never used them or seen them being used in a system.

The datasheet looks promising so I assume that if you are following the recipie set out then you should have the life span they projected.

I do know that at home we had a set of flooded batteries (lasted 5 years) and they were the longest lasting set we ever owned on backup power using the victron as a charger. We had used gel, agms and various never got more than 6 months to a year on our other non victron systems. Between overcurrenting and boiling away electrolite and undercharging I think we covered all the bad practices in the book. ;)

Of course we have moved to lithium now, grid power is worse now and the cycling we do now is uneconomical for lead based systems.

Use the presets they have programmed for their batteries you cant go wrong for both the multiplus and the solar.

And to add at the end of the five year we could only run lights for about two hourshours so still major loss of capacity.

rslifkin avatar image
rslifkin answered ·

As long as the charger is floating the batteries at an acceptable voltage, it should be safe to leave it on forever. The batteries in my boat sit on a constant float whenever it's at the dock during the season, as I never turn the chargers off.

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Kevin Windrem avatar image
Kevin Windrem answered ·

I've always read that lead-acid (including AGM) batteries are best stored with a charger in float mode because of reduced case of sulfation.

The only "laziness" I know of is for NiCad batteries which have a memory effect and benefit from an occasional discharge/recharge cycle. Not so with lead-acid or LFP batteries.

There are differing schools of though regarding LFP batteries. Some say it's best to charge them then store with no charger connected. I asked Battle Born and they say there is no reduced life of their batteries are kept on float indefinitely. So go with what your battery manufacturer suggests.

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piet-hein-van-asselen avatar image
piet-hein-van-asselen answered ·

Thank you for your answers.

Interupting a charge cycle is said it can have a negative effect on battery lifetime.

The idea is if you keep batteries on a constant float voltage, they get lazy. Some people say batteries should alvast cycle a bit. I assume that is also the reason storage mode of modern victron chargers with adaptive mode, switch back to absorption for a certain time after a week or so?


I understand it is safe to keep the battery on constant voltage, i doubt if it is the best for longest lifetime of the battery? This i what i am curious about.


Thank you verder much


Best regards

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