Yet Another Battery Question

[heinzir]

Does it hurt a flooded deep-cycle battery if it is never fully cycled or deeply discharged? Or should that theoretically make it last longer?

My boat sits on a mooring and is used primarily for daysailing. Electrical loads are minimal: VHF, depth sounder, and an automatic LED anchor light that comes on every night. I have been using a small 5W solar panel (trickle charger) with a blocking diode but no regulator to keep the battery topped up. There is no other means of charging the battery at the mooring. The outboard is a manual start and has no alternator.

The deep-cycle batteries I have been using only seem to last 2 seasons and then they won't hold a charge.
I have swapped the 5W solar panel for a 10W unit and added a smart (PWM) regulator for this season. I have to buy a new battery; should I go with another deep-cycle or switch to a regular type? I'm thinking that the solar panel is charging and topping up the battery every day just as an alternator in a car keeps the car's battery topped up; it never has a chance to "deep cycle" if everything is working properly.

By the way, the money gods have decreed that I stick with flooded rather than gel or AGM construction.

Henry
Chiquita

[erps]

Batteries that sit in a discharged or partially discharged condition get a hard coating on the plates (sulfate) that makes it harder for the lead to take a charge. Equalization is a high charge voltage that is supposed to break down the sulfate coating. It's also my understanding that a deep cycle battery does need to be deeply cycled to reach its full capacity of storing and giving off amps. There are several battery authorities on this forum and SSCA forum. I have found Bill Trafors' posts most helpful when I've had questions.

If you can get to a dock now and then and put a fancy charger on them you maybe able to get another season or two out of them unless you go with a fancy solar setup.

By the way, I kept a boat on a mooring for several years and I ate up batteries too.

[sailingdog]

PWM-chargers should do a pretty good job of charging the batteries...but a 10 W panel is probably not going to give you enough output to CHARGE the batteries, as it is probably just enough to keep them from discharging any further. What you need is a larger panel. Deep cycle wet-cell batteries really need to be recharged to near 100% on a regular basis or they will sulfate and die. Equalization can sometimes help, but they NEED TO BE RECHARGED REGULARLY.

A 10 W panel is only going to generate less than 3-4 Amp-hours on a good day (10 W = 14.4 V * .7 amps; 5 hours * .7 amps = 3.5 amp hours.).

This isn't enough to re-charge the batteries after your day out—much less what your anchor light is using up...and they're going to be sitting there at a partially discharged state for a long period of time. If you don't get a larger solar panel or bring the batteries to the dock and charge them up to 100%, you won't get much more than two years out of them...since you're basically killing them.

What you really need is a 60-80 Watt solar panel that can properly charge the batteries. A 80 Watt panel would give you about 25-30 amp-hours of charging per day. This is probably enough to replace what your VHF, Depth Sounder, and Anchor Light use and keep the battery nearly fully charged...greatly prolonging its life span.

[BarryL]

Hello,

As Sailingdog wrote, you want to keep a flooded battery at 100% charge as much as possible. You NEVER want to deeply discharge the battery.

As others wrote, I bet you are not properly charging your battery. Do you have a voltmeter? If not, get one and learn to use it to measure your battery. If you find the voltage is above 12.2 or so volts, the charging is not sufficient.

Good luck,
Barry

[camaraderie]

You don't say what size your batteries are or what your typical weekend use is weekly in amp hours...but let me assume a 200AH bank...a nightly draw of 5 amps for the anchor light (1/2amp x 10 hours) and assume you go sailing for a few hours twice a week drawing 10 amps each trip. That is a 55ah's a week need + the normal weekly discharge rate of wet cells is at least 6ah's.
So let's call it 60ah's a week that need replacing or (given system charging losses) about 10 ah's a day. You need a minimum of 40AH's of panels to stay topped up (using the 4x rule) and more if my assumptions seem light to you. Since you are in high lattitudes and are not in bright tropical sunshine...I would err on the higher side and get something in the 50-60W range.
As others have sad...discharging below 12.2V and NOT getting to 100% charge (12.6V) at rest...is a formula for battery destruction and gradual loss of charge capability through sulfation. You also should be EQ'ing your batts once a month at something close to 16V with a dockside or home-based 3 stage charger...but the first step is to at least keep things topped up. When you step on the boat and turn the panel off...it should be reading 13.3V or more and stay there for several hours.

I can absolutely guarantee you that you are destroying yourbatteries with your current set up.

[heinzir]

Would that I could get a 60-80Watt solar panel but alas! My boat is so small and my budget so tiny!

The only load on the battery every day when not sailing is the anchor light.
This has an LED bulb and only draws 60 milliamps (I measured.) If it runs from 7 PM to 7 AM it would use .72ah per day (.060A * 12 hrs.)

The depth sounder and VHF are obviously only used when sailing, which is mostly on weekend afternoons. I don't have the specs in front of me but a quick check on Westmarine.com shows that a similar VHF unit draws 200ma on standby. Even if it were on every day for 5 hrs that would be 1ah (.200 * 5.)

A depth sounder similar to my Standard Horizon also draws about 200ma. That's one more amp hour for a total of 2.72, a little less than the 3.5ah potential of the 10W solar panel.

And that's assuming the VHF and depth instruments are on for 5 hrs every day. I wish I was able to sail that much but Life keeps getting in the way. (I'm raising 3 grandkids.)

I am an electronic technician by trade but know that I have a lot to learn about batteries and proper charging procedures. I am familiar with using a voltmeter and have even built and installed an LED charge indicator for the boat that has 9 red, yellow, and green LEDs that light up at incremental voltages from 10.5 to 14. It is accurately calibrated with my shop Fluke dvm. According to this indicator the battery charge has been adequate yet the batteries just don't last.

My first thought was that the battery was being OVERcharged since the draw is minimal and the panel puts out current every day even if the boat sits unused for a week or two. Is this possible? That's why I bought the PWM controller. (This will be the first season I've used it.)

Back to one of my original questions: Given my light loads and marginal charging capability, would I be better off ditching the deep-cycle battery and going with a standard automotive battery? Which would survive these conditions better?

Henry
Chiquita

[sailingdog]

Henry-

If you use the VHF for any transmission, it's going to draw down the batteries fairly quickly, since they're at least 25 Watts of transmission power, and somewhat inefficient, so you're probably looking at 2.25 or 2.5 amps per hour for transmit.

You're also missing the parasitic discharge that wet-cells go through, just sitting there...

It could be from overcharging, but I seriously doubt it. What PWM charge controller are you using, and is it a three-stage charge controller. If it isn't a three stage charge controller, you need to get one that supports bulk, absorption and float phases at a minimum. If it was overcharging, it would probably be boiling off electrolyte. Have you checked the electrolyte specific gravity and levels in the cells on a regular basis??

Are there any other parasitic loads on the batteries that may not have been accounted for???

[heinzir]

Good point about the electrolyte level and specific gravity. No, I have not been checking it and yes, I will.

I know about the current drain when transmitting on the VHF at full power but I'm mostly a lurker, not a talker. I don't think that is an issue.

I don't remember the brand of charge controller but it is a sophisticated 3-stage unit. It is new this year as is the 10W panel. I previously used a 5W panel w/o a controller. (This was before I felt the need to add an automatic anchor light -- before I was dismasted at the mooring by a drunken power boater in the middle of the night -- but that's another story!)

There shouldn't be any other parasitic loads as I have a master switch that turns off power to everything except the anchor light and the automatic bilge pump. I added a latching alarm LED to the pump circuit to tell me if it has come on while I'm away from the boat. It has never come on yet. (I do test it once in a while to make sure the alarm and the pump are both working properly.)

The boat is still sitting in my driveway; I have several more weekends worth of projects to finish up before launching for the season. I want to replace the battery before she hits the water. What's the verdict? Deep-cycle or regular?

[sailingdog]

I'd go deep cycle...the loads you're using it for are more deep cycle than anything else, as is the charging regimen.

[artbyjody]

Thought I would pass this along - courtesy of a link found from the Panama Canal delays that referred to Yachting Monthly...

Sterling Power Products: What is the best battery to use for an auxiliary charging system?