Continuous Charging of Boat Battery

[Dante]

Q1: what set-up to continuously charge a boat battery is best?

ASIDE. [My 2004 220 DAUNtlESS 22 has] a slow leak and so the sump pump runs regularly while docked. The batteries are sealed lead-acid deep-cycle types in good shape. The standard wiring allows bilge to run from one of the batteries while battery selector is on the OFF position.

[jimh]

Rather than continuous charging, I recommend continual charging at regular intervals.

A battery can be charged at a low current (perhaps 1-Ampere) by a small "float" charger. However, I would not leave such a charger connected continuously, as my experience with doing that (for extended periods of time) tends to result in a failure of the charger. A better approach would be to get a electrical switch-timer that would turn on the float charger for say an hour each day, producing continual re-charging.

An example of an extraordinarily reliable and durable electrical timer switch that can work for decades and has been used for more than 70-years (which is as long as I can remember seeing one used by my father in our house when I was a child) is the INTERMATIC timer. For example see

https://www.homedepot.com/p/Intermatic-T100-Series-40-Amp-125V-SPST-24-Hour-Mechanical-Time-Switch-with-Indoor-Enclosure-T101D89/100151619

A newer model might also work:

https://www.homedepot.com/p/Intermatic-15-Amp-24-Hour-Outdoor-Plug-In-Heavy-Duty-Timer-Black-HB11KD89/205478787

As for the battery charger, you might use something like this:

https://www.amazon.com/ProMariner-ProSp ... ast_sto_dp

https://www.westmarine.com/guest-1.5-am ... 49454.html

You can adjust the amount of time each day the battery will be getting charged to match the amount of discharge caused by the perpetual pumping of water from the sump area.

[Note on word usage; herein "continuous" means without interruption; "continual" means "occuring at regular intervals"; "constant" means without changing.]

[Tom Hemphill]

Q2: Is there a danger to the attached battery charger if the bilge pump puts too great a load on the circuit?

[Dante]

jimh--thanks for the reply.

You would think these newer maintainers would add an app where you could set timing.

Q3: would getting a maintainer that does both batteries for good measure, even though the second battery doesn't really need the recharging, be worth the cost?'

See this NOCO product as an example.

Q4: what do you think of a solar charger?

It charges intermittently by definition. And in the context of not being worried about the longevity of the charger if it keeps my batteries intact and my boat from taking on excessive water.

Q2: Is there a danger to the attached battery charger if the bilge pump puts too great a load on the circuit?

There is a 5-Ampere fuse on the bilge circuit (at least the box holding the fuse is labeled as such). I understand that that might not protect the power side of the circuit.

ASIDE: That first timer is exactly what I have controlling my swimming pool equipment.

[jimh]

Q2: Is there a danger to the attached battery charger if the bilge pump puts too great a load on the circuit?

The risk inherent in letting a pump operate autonomously from battery power is just that the control mechanism (or the weather) could create almost continuous operation of the pump due to a stuck float switch (or very heavy rain), and this would result in the battery being discharged to an extremely low state of charge. The general thinking with lead-acid batteries is that avoiding discharging them to exhaustion will extend the service life of the battery.

[jimh]

Q3: would getting a maintainer that does both batteries for good measure, even though the second battery doesn't really need the recharging, be worth the cost?' See this NOCO product as an example.

I am not familiar with that particular product, but the NOCO brand has become more prominent lately--with some mixed reviews. That might be due to the NOCO brand selling in huge volumes, so in any product that you sell a million of them, there will be some customer that is not completely satisfied.

If your plan is to leave the NOCO charger powered-on all the time and let it decide how much current to push into the batteries, you'd have to assess that yourself by monitoring what it actually does.

As I see it, the risk to leaving a 120-VAC charging device powered-on and connected to a battery and supplying charging current is in two realms:

1. the charging device is probably not designed for 100-percent duty cycle for extended periods of use; and it may overheat or otherwise fail; and
2. the battery may not appreciate the extended charging time, which could result in the electrolyte "boiling" away.

Q4: what do you think of a solar charger?

The voltage output from a photovoltaic panel will vary with the amount of sunlight. Generally a photovoltaic panel must be connected to a charging control module in order to regulate and control the voltage and current being provided from the panel. In the end the "solar" method will have a lot more cost than the $40 float charger and a $40 timer, and the minimal electrical power being consumed will not be expensive, depending how your mooring arrangement.

ASIDE: That [Intermatic] timer is exactly what I have controlling my swimming pool equipment

Very good choice for that application.

ASIDE
I often gently re-write articles to separate and number questions being posed. This helps readers to recognize the actual questions without out having to carefully read and parse long narratives to find them. I think the record number of questions asked to begin a thread is eight. Generally to have a cogent discussion, it is best to only ask one or two questions to open the discussion.

[bjohn]

I have several NOCO products, including a battery jump start pack and a "Genius 5" model battery charger. I've had a good experience with both products and they seem to be very nicely made. NOCO also sells replacement parts and accessories from their website which is nice.