How do you maintain your batteries at the dock?

[Fishspearit]

It would be nice if we could always be on the move cruising, but like most people we have to spend long periods working and living at the dock. Since we've got deep cycle batteries that aren't designed to always stay on a float charge, I'm wondering what sort of regimen most people are using to keep their batteries healthy while at the dock for 3-6 months or more.

I have a 'smart' charger, although I sometimes question how smart it really is. Every time the power flickers it goes back into bulk charging mode and brings voltage up to 14.5 or so. Sitting here on a float charge of 13.75V I can see my batteries bubbling and hear them gurgle periodically. What is the best voltage for floating a deep cycle lead acid battery? I should also add that I have no way of equalizing them, which would be nice, but since I have a working inverter/charger I'm not going to spend the money right now for one with equalizing capabilities.

I'm pretty sure I should be discharging them occasionally to keep them healthy, and I'm thinking a deep discharge to 50-60% once a month, and maybe a partial discharge half way through the month. What are others doing for a healthy battery life while the boat is penned up in it's stall?

[S/V Illusion]

Glad you asked as I've often wondered myself. Guess we've all seen the arguments that batteries need to be periodically partially discharged as well as periodically equalized ( a more accepted practice) to maintain longevity and many of us are well-versed in battery chemistry to know there may be some truth, however, nowhere have I ever seen any empirical data to support the theory regarding the damage from constant float charging.

Hope you get some responses with more than the battery chemistry rehash.

[Pblais]

I've had solar panels with both boats and the panels regulated keep the boat charged well during off use times. I don't like being plugged in given the crap you can get in the power line. That seems to work well at keeping them topped up. Other than checking the water level regularly I don't see many problems. That seems to work well when I had flood batteries then switched to AGM and now back to flood.

Properly regulated power is perhaps the hardest thing to get. It helps if you can get a good volt meter to adjust the regulator properly. The dime stop digital meters can be off a great deal.

[CaptHead]

I have done years of boatlife and 12 and 6 volt batteries. I have a Prosine smart charger and all the battery checking equipment. I have been a member of boating forums for over 25 years and they all keep a smart charger going the whole time the alternator is not running. I say they are nuts.

Batteries have cycles built into them. They produce so many cycles in their life, period. So, you can use it by cycling it every .5 volt with the charger on constantly or do what I do. Turn it off and use the batteries for the purpose they were intended. Storage of electricity.

Use 40%-50% and recharge and you get the optimum amperage from that battery.

here is a chart for the doubting thomasses:
Typical Cycle Life
(100 amp/hr Trojan Deep Cycle Battery) Depth of discharge Number of cycles Total amp-hrs provided
during service life10% 6,200 62,00020% 5,200104,00030% 4,400 132,00040% 3,700148,00050% 2,900145,00060%2,400144,00070%2,000140,00080%1,700136,000

I charge mine when they are low. I have 7 year old batteries and they are fine. I use very little distilled water too. I highly recommend this system.

[Fishspearit]

Originally Posted by Pblais

I've had solar panels with both boats and the panels regulated keep the boat charged well during off use times. I don't like being plugged in given the crap you can get in the power line.

Off use times I would be fine just turning the charger off and letting the batteries sit, but I was thinking more along the lines of 'in use at the dock' with fridge on, lights, stereo, etc.

Capt. Head, so you never float charge your batteries? That chart didn't paste well, kind of hard to pick the numbers out of it.

The reason I wonder about this is that when I was on a submarine maintaining the battery(I don't think I'm giving away any state secrets here, the sub was decommisioned 13 years ago) we never kept it on a float charge, it was either trickle discharging or being used, or being charged. A different battery, yes, but still a lead acid deep cycle battery.

[CaptHead]

I will let the charger go through all cycles before turning it off. On anchor is a different story as I use them harder and recharge either daily or EOD.

[CaptHead]

Typical Cycle Life
(100 amp/hr Trojan Deep Cycle Battery) Depth of discharge Number of cycles Total amp-hrs provided
during service life
10% 6,200 62,000
20% 5,200 104,000
30% 4,400 132,000
40% 3,700 148,000
50% 2,900 145,000
60% 2,400 144,000
70% 2,000 140,000
80% 1,700 136,000

There is % use, # of cycles, Total amps use

[S/V Illusion]

I asked a similar question on another board and was referred to this link which is not only responsive to the original question but provides some authoritative info
on how to best maitain batteries under charge.

Battery Charging Techniques

[btrayfors]

Captain Head...

Where did you get those figures? Could you please provide a link?

The figures you cite suggest that the Trojan batteries are better than the Cadillac of flooded batteries, the Rolls/Surette.

Rolls publishes # of expected cycles for their batteries, based on Depth of Discharge. For the 4000 Series, life expectancy is as follows:

"The 4000 Series expected life cycles vs. depth of discharge @ 100 hr. rate/25°C:

2688 @ 10% DOD
2048 @ 30% DOD
1536 @ 50% DOD"


For the 8000 Series it is as follows:


"The 5000 Series expected life cycles vs. depth of discharge @ 100 hr. rate/25°C:


6600 @ 10% DOD (depth of discharge)
5040 @ 30% DOD
3840 @ 50% DOD"

As an aside, IMHO batteries in the Float Mode are not being cycled. They are being maintained at or near full-charge.


Bill

[sluissa]

As far as I know, it's bad for Lead Acid batteries to be below about 75% charge. If they stay below that for any significant length of time they start to degrade which shortens the life of the battery. As far as I'm concerned a float charge does nothing to hurt it.

Edit: overcharging can cause your liquid to drop, so check it regularly, but as long as you keep an eye on that, no problem.

[CaptHead]

From the Galcier Bay web page. They make refrigeration, etc and have a how to size a battery bank page with this info.

I can't answer to the float/cycle question and see both sides. The problem isn't with the battery when nothing is on, it is when you use the water, say, and the draw automatically kicks in the charger. I watch that happen on my panel.

Glacier Bay - Support

I have the Trojan 6V T-125 and a bank of 6. I will increase to 10 after I add a second 350 Amp alternator to my port engine. Problem is I don't want to add 4 new batteries to these 6 old so I need to wait till they are shot. They are rated at 240 Amps and 10 combined to 12 V will give me 1200 AH total.

A neighbor put those huge tall rolls in his boat and he ended up selling it in a few years. I never found out how they lasted.

[CaptHead]

I usually go 70-80% just for that reason.

[S/V Illusion]

I've excerpted a portion of the link to which I referred earlier as some of you may want to re-read it:

"All battery do not like having residual charge current flowing through their plates for extended periods of time. However, for our discussion here, I'll limit my comments in particular to deep cycle lead acid batteries. ... the problem created by continuous charge/residual current flow through lead acid batteries in positive grid corrosion. This is something that happens anyway during the charge process, but when the charge to float mode time ratio becomes mostly float mode, the grid corrosion continues to happen with no useful effect on the battery, so that the positive grid corrosion is highly accelerated. The grid corrosion produces increased internal impedance ( i.e. - reduced cranking capability ) and reduced deep cycle capacity from the loss of effectiveness of the positive plates. The relative reduction of capacity percentages I cited due to continuous charging versus cycle charging come from 2 primary sources: manufacturer's data, and my own empirical data from messing about with deep cycle batteries extensively since 2000. The primary manufacturer I have worked with is Concorde Battery, who manufactures not only the Lifeline AGM batteries, but also a complete line of aircraft and aerospace batteries in civil and military applications. The same family that owns Concorde Battery also owns Trojan Batteries, so the experience base there is pretty broad. Trojan was the premier manufacturer of submarine batteries during the diesel/electric submarine era. They are also still the leading manufacturer of golf cart batteries, among other batteries.

The stated 35 to 40% maximum reduction in useful life of a deep cycle lead acid battery due to continuous float charging was based upon Concorde's own testing and their experiences in field applications of their batteries in solar power applications ( the ultimate cycle charge environment ). My own customer experiences and the results of my own studies with the Lifeline batteries supports the stated range of useful life reduction with some reduced effect if the float voltage is temperature compensated and well regulated at the lower end of the allowable float voltage range. In the last several years, Concorde/Lifeline has reduced their recommended float voltage range from a nominal 13.4 volts to 13.2 volts, and this will further reduce the rate of positive grid deterioration in the float mode. In one of my own examples, the new AGM 4D batteries I installed on my Stamas 44 lived about 3.5 years in constant float mode at a temperature compensated 13.4 volt nominal. At the end of that time, the measured cranking power ( CCA ) and deep cycle capacity was reduced by about 20%. The next 1.5 years was spent using cycle charging, and the measured CCA and a-hr numbers were only about an additional 5% lower. I have to note that these examples are from premium grade AGM deep cycle batteries, and the results from a relatively inexpensive flooded battery would probably be significantly worse."

My own experience seems to diverge a bit from the above in that I've managed 7 or 8 good years out of my bank of Trojans whilst keeping them charging 24/7 while on the dock to no apparent damage given this is the expected useful lifetime.
The real question is whether it's worth potentially shortening the life of an expensive bank when there are multiple alternative power options.

[trinescape]

on my tri which is on a wet mooring so no a/c power, all i have is 2 -40 watt solar panels thru an excellent smart solar regulator feeding into a 200 amp wet battery and i leave my 12 volt refrigeration on [ only on the lowest setting] and my batteries are 6 years old and still going strong , mind you every time i check the boat one of my regular checks is looking at the battery level. having said that on some visits ,cloudy days the volt meter is fractionally low eg-12.1 volts insteadof 13.9 -14volts so thats how i vary my battery levels

[David M]

Originally Posted by Fishspearit

It would be nice if we could always be on the move cruising, but like most people we have to spend long periods working and living at the dock. Since we've got deep cycle batteries that aren't designed to always stay on a float charge, I'm wondering what sort of regimen most people are using to keep their batteries healthy while at the dock for 3-6 months or more.

I have a 'smart' charger, although I sometimes question how smart it really is. Every time the power flickers it goes back into bulk charging mode and brings voltage up to 14.5 or so. Sitting here on a float charge of 13.75V I can see my batteries bubbling and hear them gurgle periodically. What is the best voltage for floating a deep cycle lead acid battery? I should also add that I have no way of equalizing them, which would be nice, but since I have a working inverter/charger I'm not going to spend the money right now for one with equalizing capabilities.

I'm pretty sure I should be discharging them occasionally to keep them healthy, and I'm thinking a deep discharge to 50-60% once a month, and maybe a partial discharge half way through the month. What are others doing for a healthy battery life while the boat is penned up in it's stall?

14.5 volts is much too high. An absorption charge is not necessary each and every time.....all this will do is turn your water into hydrogen much faster than normal. Either something is wrong with your charger or it needs an adjustment if such an adjustment is possible.