Battery charger/shore power

[nimrod1230]

A supplementary question related to an earlier post regarding shore power.
Should I leave the battery charger on 24/7 or switch on every 2/3 weeks?
Charger is a fancy Cristec unit with intelligent charging regimes.
If the wisdom is to leave it on, should I fit a galvanic isolator in the circuit?
Sorry for all the questions but permanent power is new to me.

 

[VicS]

A supplementary question related to an earlier post regarding shore power.
Should I leave the battery charger on 24/7 or switch on every 2/3 weeks?
Charger is a fancy Cristec unit with intelligent charging regimes.
If the wisdom is to leave it on, should I fit a galvanic isolator in the circuit?
Sorry for all the questions but permanent power is new to me.

Your choice really whether or not to leave the charger on 24/7. A modern multistage charger should be suitable to leave on if required.

BUT if you are leaving shore power connected for prolonged periods, in use or not, a Galvanic isolator in the connection is next to essential unless your shorepower system is installed without earth bonding to the DC negative/ anodes etc. or includes an isolation transformer.

It is very unlikely that a professionally installed system would these days be done without the earth bonding. It may even be in contravention of the latest standards to do so.

 

[Spi D]

Your choice really whether or not to leave the charger on 24/7. A modern multistage charger should be suitable to leave on if required.

BUT if you are leaving shore power connected for prolonged periods, in use or not, a Galvanic isolator in the connection is next to essential unless your shorepower system is installed without earth bonding to the DC negative/ anodes etc. or includes an isolation transformer.

It is very unlikely that a professionally installed system would these days be done without the earth bonding. It may even be in contravention of the latest standards to do so.

+1. As batteries' service life depends on how many deep dis- and recharge cycles it receives, keeping it topped up is a long term precaution. The benefit of always having access to full capacity (and other devices connected to shore power) is not to be ignored either

 

[NormanS]

A supplementary question related to an earlier post regarding shore power.
Should I leave the battery charger on 24/7 or switch on every 2/3 weeks?
Charger is a fancy Cristec unit with intelligent charging regimes.
If the wisdom is to leave it on, should I fit a galvanic isolator in the circuit?
Sorry for all the questions but permanent power is new to me.

Surely it depends on what you are doing? If the boat is shut down with nothing drawing current, there is not much point in keeping the charger on. If you are likely to be aboard every 2/3 weeks, switch it on when you're there.

 

[Amulet]

Surely it depends on what you are doing? If the boat is shut down with nothing drawing current, there is not much point in keeping the charger on. If you are likely to be aboard every 2/3 weeks, switch it on when you're there.

My reading tells me is that it is very much better for the batteries to leave it on if it is designed to deliver the appropriate float voltage to the battery. My experience is consistent with that. Have I missed something?

 

[NormanS]

My reading tells me is that it is very much better for the batteries to leave it on if it is designed to deliver the appropriate float voltage to the battery. My experience is consistent with that. Have I missed something?

The designed purpose of a battery is to store electrical power. If it can't do that, it's no use. If you have constant mains power, you don't need a battery. Your car has a battery. Is it on constant charge? Your house probably doesn't have a battery, but probably has constant mains power. But what would I know? When in use, my boat doesn't have mains power.

There's nothing wrong with leaving a suitable charger switched on. It is merely unnecessary.

 

[Amulet]

The designed purpose of a battery is to store electrical power. If it can't do that, it's no use. If you have constant mains power, you don't need a battery. Your car has a battery. Is it on constant charge? Your house probably doesn't have a battery, but probably has constant mains power. But what would I know? When in use, my boat doesn't have mains power.

There's nothing wrong with leaving a suitable charger switched on. It is merely unnecessary.

Yes, I do know how a battery works. Most sources I find say that lead acid battery life is maximised if they are kept fully charged and a float voltage is maintained when the battery is not in use. The float voltage should be such as to cancel our the self-discharge and low enough not to cause gassing. This is what intelligent chargers do. The required float voltage varies as a function of temperature, and very smart chargers sense the temperature. I can't imagine going to all that trouble if switching the votage to zero for a while was just as good.

 

[nimrod1230]

From the replies I guess a combination of leaving on and off depending on visiting times and how the batteries hold charge. Thanks for your thoughts.

 

[Amulet]

From the replies I guess a combination of leaving on and off depending on visiting times and how the batteries hold charge. Thanks for your thoughts.

If it is a smart charger, with a float voltage stage, it is better for your battery to leave it on all the time - that's what it was designed for.

 

[BlueChip]

I always disconnect shore power when we leave the boat as a safety measure.
We do have a galvanic isolator fitted but by disconnecting we totally remove the possibility of stray currents causing galvanic corrosion.
My anodes last three or more years, when we left her plugged in I had to change them every season.
If I leave a dehumidifier on board I run a separate mains cable from the shore power socket bypassing the boats electrical systems.
I have a battery monitor and with everything switched off, there is negligible battery discharge even after a month or so. My smart charger takes about 15 minutes to get back to a float charge.
The only reason I can think to leave it plugged in is if she developed a leak and the bilge pump was running continuously, as we are in a marina I think the continuous discharge would be noticed well before the batteries went flat

 

[NormanS]

An advantage in NOT leaving the charger switched on all the time, is that you get some indication of the condition of your batteries. Are they holding their charge? You will never know if they are on charge all the time. Then you go off on a cruise away from your shore power, and find your batteries have died. Not good.

 

[Amulet]

An advantage in NOT leaving the charger switched on all the time, is that you get some indication of the condition of your batteries. Are they holding their charge? You will never know if they are on charge all the time. Then you go off on a cruise away from your shore power, and find your batteries have died. Not good.

Agreed. Do a capacity test from time to time, and check it against your battery monitor(s). I do. My life is simple, in that I don't cross oceans, and in my current sailing style I usually end up with shore power at least once a week. If you buy a fancy charger why not get its benefit? My alternator regulator on the engine has been bypassed to use a multistage wind generator regulator. It too is clever, doing a far better job in the bulk stage than the original. Despite being a tiddly wee boat with a pathetic little engine I can run my instruments and keep the beer cold.

 

[NormanS]

Agreed. Do a capacity test from time to time, and check it against your battery monitor(s). I do. My life is simple, in that I don't cross oceans, and in my current sailing style I usually end up with shore power at least once a week. If you buy a fancy charger why not get its benefit? My alternator regulator on the engine has been bypassed to use a multistage wind generator regulator. It too is clever, doing a far better job in the bulk stage than the original. Despite being a tiddly wee boat with a pathetic little engine I can run my instruments and keep the beer cold.

Ah well, we live in different worlds. I NEVER have shore power, except when laid up in the winter, so I have to KNOW that my batteries are in good condition and hold their charge.

 

[nimrod1230]

Steady guys, too many opinions will puzzle a poor old man. Having never had shore power permanently available I have had to be self sufficient over the years so this is a novelty though how much it is going to cost remains
to be seen. Have bought a dehumidifier and galvanic isolator ready for plug in. The joys of keeping things simple!!

 

[Spi D]

Cost and dehumidifier goes hand in hand :ambivalence:

The device will have a stated nominal wattage which will indicate the consumption and cost as per hours in use.

 

[sailinglegend420]

........I have a battery monitor and with everything switched off, there is negligible battery discharge even after a month or so...

You highlight a major problem with battery monitor's accuracy because they can't measure the batteries internal self-discharge, which can be 10% a month. Leave the boat for 6 months and the battery will be nicely sulfated!

One idea is to re-programme your charger to a lower voltage and for a shorter boost time so as not to "overcharge" the battery if it does occasionally go back into "boost" mode. This will happen when the shorepower gets disconnected temporarily. You don't want the charger going back into boost mode for 4 hours when the batteries are already fully charged.

A good marine battery charger should have a weekly boost mode for about an hour that will stir up the electrolyte and then drop down to float mode again.

 

[charles_reed]

The designed purpose of a battery is to store electrical power. If it can't do that, it's no use. If you have constant mains power, you don't need a battery. Your car has a battery. Is it on constant charge? Your house probably doesn't have a battery, but probably has constant mains power. But what would I know? When in use, my boat doesn't have mains power.

There's nothing wrong with leaving a suitable charger switched on. It is merely unnecessary.

Depends on circumstances - I know at least one occasion when a fancy charger, left on all winter, boiled all the batteries dry.

This was due to the fact that the charger (so smart that it always put in an equalising charge) went into equalising mode (high volts/low amps) every time the power was reconnected. There were innumerable shorepower cuts and re-connects - the rest can be imagined.
Playing safe, I've always left the charger off.