Battery charger usage

[Laundryman]

I have a Guest 20amp ( 2x10amp) multi stage charger. My boat is on a pontoon with electricity so I am in the practice of leaving it on. It's fully automatic and should take care of itself.

Should I leave it on?
Should I use a time switch?
Should I just use it when I am present.

The question is prompted by a comment on another thread asking" why would you need to leave it on 24/7"

 

[VicS]

If it goes to a float stage when the batteries are charged you should be able to leave it on ... but is there any reason to?

On a timer with frequent on periods may not be a good idea because it may always restart at full whack. On for 24 hours once a month or so may be more acceptable.

I'd not leave it on unless there was some load that required the battery to be routinely recharged

If using a timer check if the charger draws current from the battery when not powered up. My portable one does..

 

[VicS]

Best part of 12 hours and no other comments!

Anything between +1 and 8πr³/3 ?

 

[nigel1]

I'll bite.

I leave my boat disconnected from shore power for up to 6 weeks. Battery charger is off. Of course, I leave the batteries in a fully charged state before I leave the boat. There is no draw, no leakage's (from battery bank).
I have a D400 wind geny, but that is secured when I am away.

The longer I can keep the boat electrically isolated from the shore the better in my opinion.

 

[johnalison]

I also leave my charger off most of the winter but thee is a solar panel connected to the service batteries. About every 6 weeks I put the charger on for a day or so to charge the start battery as I think the period from end of October to April is too long even for a fully charged battery.

 

[halcyon]

I have a Guest 20amp ( 2x10amp) multi stage charger. My boat is on a pontoon with electricity so I am in the practice of leaving it on. It's fully automatic and should take care of itself.

Should I leave it on?
Should I use a time switch?
Should I just use it when I am present.

The question is prompted by a comment on another thread asking" why would you need to leave it on 24/7"

Leaving the batteries on float charge 24/7 will do no good, and can reduce battery life. It has it's roots in history, and stationary battery banks, used as back-up power supplies at telephone exchanges. These were held at 13.6 volt, with a periodic charge to a high voltage. Back in the early 80's Sealine asked us to design a mains charger for them. This unit combined the 13.6 V float charge with a high 14.2 V charge stage. At the time, the battery charger was only used when the owner was on board, so providing a regular high voltage charge phase, thus maintaining the battery in a good state.

So leaving charger on 24/7 is not good, a timer is okay with a multi-stage charger.

What time period ?, well next time on the boat charge up the batteries, turn of charger as you leave. After say a week return to boat, turn on charger, and see how long it takes to go through a charge cycle. Set timer to run weekly for this period plus a bit. If the time is very short, try a one month period, same test. If you have a load on the battery you may want to reduce the one week figure.

With a non regulating charger, you can fit a voltage controlled switch that can give a similar, in some cases better, charge level.

Brian

 

[Deleted member 36384]

Leaving the batteries on float charge 24/7 will do no good, and can reduce battery life. .....

Brian,
Interesting post. Would this apply to chargers such as Sterling's Pro Charge Ultra which has a "New, low activity, standby mode to increase battery life." In your opinion should this type of charger be switched off as well. I am away from home for long periods of time and the Pro Charge Ultra that I have fitted stays on all the time as I believe it does not operate in float mode all the time due to the feature quoted above. I am not wishing to hi jack the thread, however, it may be a relevant exception or it may not be. When I do get down to the yacht the current draw is normally zero and the voltage 24.8V (IIRC - 24 volt system, to state the obvious). This is read directly from the chargers inbuilt meters.

 

[Plevier]

Leaving the batteries on float charge 24/7 will do no good, and can reduce battery life. It has it's roots in history, and stationary battery banks, used as back-up power supplies at telephone exchanges. These were held at 13.6 volt, with a periodic charge to a high voltage.

From a battery manufacturing background I'd take a slightly different perspective (but no real disagreement).
13.6-13.8V is a combination - or compromise - float/recharge voltage used on heavy standby (not cycling) batteries in critical applications to make sure they are always up to full capacity.
If your charger floats at around that level, yes it's too much for a more lightly constructed battery and might affect the life.
I believe some multi stage chargers now drop back to a true float voltage of nearer 13V. (It's gone full circle; that's what used to be used as a pure float voltage in standby systems, with a regular boost charge, before the higher dual purpose float/recharge voltage became popular.) If you have one of those it won't do any harm to leave it on.
However because the self discharge of modern batteries is so low, there is probably no benefit in it unless you are leaving the battery alone for more than 3 months. Normal industry practise for new batteries in storage is to recharge every 6 months.
If you leave it on, do make sure that a brief power interruption won't instantly put it onto a timed boost (like my charger) otherwise you may cook the batteries!
I turn my charger off and give a refresh every few weeks.