Over-charging batteries

[Richard10002]

I thought that 14.4V was the point below which lead acid is said not to "boil", (cant think of the word, but hope you know what I mean).

 

I recall this being the reason that some technologys, (AGM, Gel, Sealed), have this specified as an upper limit for charging?

 

I may be wrong  

[ditchcrawler]

On 14/09/2020 at 07:56, jenevers said:

So what damage can happen if it's 14.4V?Trojans btw?

Why would you want to float at 14.4 volts 

 

[Richard10002]

18 minutes ago, ditchcrawler said:

Why would you want to float at 14.4 volts 

 

I don't think, "wanting to float at 14.4V", was the context of the question.

 

I think it was more along the lines of:

 

If, for some reason, having left the boat for a few weeks with the solar running, what damage could be caused if it charged at 14.4V, rather than dropping to a float of 13.6V, and remaining there?

 

I guess if the answer was that there would be no damage, there would be no immediate need to address the possibility. If the answer is some undesirable damage, maybe some significant attention would be given.

 

"undesirable" is the wrong word, but you will get the gist?

[ditchcrawler]

17 minutes ago, Richard10002 said:

I don't think, "wanting to float at 14.4V", was the context of the question.

 

I think it was more along the lines of:

 

If, for some reason, having left the boat for a few weeks with the solar running, what damage could be caused if it charged at 14.4V, rather than dropping to a float of 13.6V, and remaining there?

 

I guess if the answer was that there would be no damage, there would be no immediate need to address the possibility. If the answer is some undesirable damage, maybe some significant attention would be given.

 

"undesirable" is the wrong word, but you will get the gist?

But dont most solar controllers drop back to float on fully charged batteries, even cheap ones. I have one of the cheapest and when I get to the boat its always just less than 27 volts, I don't know what its been up to as I am not there. 

[jenevers]

2 hours ago, cuthound said:

 

Plate and sometimes, depending on plate and group bar materials, group bar corrosion.

 

The former shortens battery life by a little, nowhere near as much as sulphation from undercharging. The latter causes the battery to fail spectacularly when one for more plates drop off their group bar and short the battery out.

Spectacularly as in explosion?

2 hours ago, WotEver said:

And they’ll probably require regular topping up. 

They are.

[WotEver]

8 minutes ago, jenevers said:

Spectacularly as in explosion?

That’s possible, yes. 

[jenevers]

1 hour ago, ditchcrawler said:

Why would you want to float at 14.4 volts 

 

I'm sure I set float at 13.5v, it's just that whenever I look at the remote MT50 it seems to display over 14v. This was during winter when there was no load on the batteries.

[WotEver]

Just now, jenevers said:

I'm sure I set float at 13.5v, it's just that whenever I look at the remote MT50 it seems to display over 14v.

Did you happen to note the current?

[jenevers]

1 minute ago, WotEver said:

That’s possible, yes. 

Has that ever happened to anyone on this forum?

[WotEver]

Just now, jenevers said:

Has that ever happened to anyone on this forum?

It happened to Biggles, but for a different reason. I’m pretty sure I’ve read on hereof folk having to spread loads of Bicarbonate all over the engine bay. 

[jenevers]

2 minutes ago, WotEver said:

Did you happen to note the current?

Afraid not. I did notice that the battery icon showed a completely full battery which it isn't now, even though the batteries are at 12.7v

[WotEver]

3 minutes ago, jenevers said:

I did notice that the battery icon showed a completely full battery

You can safely ignore that icon for evermore.

[cuthound]

42 minutes ago, jenevers said:

Spectacularly as in explosion?

 

 

Potentially yes, particularly if a spark is generated by the short and hydrogen gas is present.

 

 

31 minutes ago, jenevers said:

Has that ever happened to anyone on this forum?

 

I have witnessed the aftermath of a battery explosion, but it was in a telephone exchange, not a boat.

 

The 2 volt, 600Ah cells were glass cased, and the explosion took out 4 cells. The floor was awash with acid and bits of glass were embedded in the walls and ceiling.

Edited September 15, 2020 by cuthound
Clarification

[Richard10002]

1 hour ago, ditchcrawler said:

I don't know what its been up to as I am not there. 

I think that's the point

 

I find the MT50 very confusing but, if the sun is powerful enough, I think the MT50 allows 3 hours of bulk/absorption everyday, before dropping to float.

 

I think I could set it to less time of bulk/absorption, but that would defeat my particular goal. I suppose, if you are leaving the boat, with topped up batteries, you could alter it to float every time you left, and set it back when you return..... but that would be a faff, and unnecessary if the damage at 14.4V was going to be insignificant.

 

I am merely trying to justify the question here - not trying to provide an answer