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Spend my money on:

Battery questions with a fun poll..spend my money!

4K views 25 replies 15 participants last post by  Minnewaska 
#1 ·
My batteries are group 24 wet cell 'deep cycle'. My needs are limited, LED lights, fresh water pump, charging the cell phone, VHF, run fans on a hot night (rare on a mooring).

I'm at 12. 5 volts, they are five years old. Last year was a tough year for them, they got most of their charging with the alternator on the mooring. If not for last season I think they would be healthier.

I have a stock Yanmar alternator and don't see myself upgrading, nor do I see myself on a slip hooked up to shore power this year.
 
#7 ·
The first thing I would do is load test the batteries. Resting voltage doesn't tell you much, the acid test (no pun intended) is to withdraw a certain amount of charge and then measure the resting voltage. I test my batteries every 6 months or so. An amp/hour meter does help. What I do is use half the battery (you can use less, say 1/4 or 1/3) capacity at the C/20 rate, which for my group 24s was 37.5 Ah over 10 hours. Plenty of resting voltage vs. charge tables on the interweb. The old batteries were pretty stable for about 5 years, and then really started to go down the spout in year 6.
 
#10 ·
I would not spend a penny on batteries, until I had the charging system worked out. 5 years should be minimum lifespan (I plan for 8 and when I last replaced, I could have gone another year) . You'll just crush them again (especially AGM), so think of the money you'll save.

If you don't want to load the boat with permanent panels, then rig something temporary for when you're gone and be sure to leave the boat, with the batteries in float. Also, be sure you can cut power to (not just turn off) everything but the bilge pump and alarm. Anything connected to the bank will have a parasitic load and drain your batts, while you're away during the week.
 
#11 ·
My batteries are group 24 wet cell 'deep cycle'. My needs are limited, LED lights, fresh water pump, charging the cell phone, VHF, run fans on a hot night (rare on a mooring).
Probably fine for your use. When it comes time for a replacement I would suggest a single 12V Golf Car battery such as a Trojan T1275. This is a true golf car battery but in a 12V configuration with 150Ah, about the same capacity as two pseudo deep-cycle G-24 batteries but many, many more cycles, same plates as a T-105 just in a 12V configuration.. US Battery & Deka also make 12V GC batteries. These are NOT to be confused with Group 24, 27 or 31 12V batteries.



I'm at 12. 5 volts, they are five years old. Last year was a tough year for them, they got most of their charging with the alternator on the mooring. If not for last season I think they would be healthier.
Voltage tells you nothing about how much capacity the batteries have left in them nor does specific gravity. All this gives you is guidance on SOC... You can easily have a 100Ah battery at 12.73V and with a good SG and five years later have that same battery at 12.73V and a good SG reading yet only have 50Ah's of capacity in it. Both batteries are at 100% SOC but one is new and one has been depleted by 50% of its capacity. SOC is not capacity.

Only a capacity test can give you guidance on Ah capacity. Load tests only test for cranking ability not long slow discharging. A battery may have poor cranking but may still be able to support a 2A load for many hours.. You are one of the best tools for gauging your bank. If your morning voltage used to be 12.4V and now it is 11.9V using the same loads, well its likely beyond useful...

I have a stock Yanmar alternator and don't see myself upgrading, nor do I see myself on a slip hooked up to shore power this year.
Solar! Your Hitachi alt is doing you zero favors in the battery health department...

Use these till they die but do add solar...
 
#22 ·
Probably fine for your use. When it comes time for a replacement I would suggest a single 12V Golf Car battery such as a Trojan T1275. This is a true golf car battery but in a 12V configuration with 150Ah, about the same capacity as two pseudo deep-cycle G-24 batteries but many, many more cycles, same plates as a T-105 just in a 12V configuration.. US Battery & Deka also make 12V GC batteries. These are NOT to be confused with Group 24, 27 or 31 12V batteries.


.
Wise choice grasshopper! ;-)
 
#12 ·
I have a similar system: 2 grp 27 house and 1 starting battery. I do have a high output Balmar (not huge 70 amp maybe?). We can go 2 or 3 days sailing/ anchor without charging running reading lights and low power instruments.

Our batteries live a tough life on a mooring and never see shore power in season, regularly sitting, undercharged.

I keep saying I'll add a small solar panel to help but in fact we've cut our power consumption in the last few years. A small low output solar charger would be ideal for us(this is a note to self).

The bottom line in our experience and our simple system: Cheap deep cycle batteries (just over 100/ these days), last about 5 years.

We have no charge monitors and simply watch the digital voltage(hand meter), after long rest periods(most important: spring readings after a fall charge and disconnect).

With these readings, I can tell the different state of each battery - it's age -(apparent in the comparison to the others) - and how much longer it's useful.

We can keep them longer (than our 5 year average), but then end up not having ample storage to allow a few days of sailing/time at anchor without running the engine.
 
#13 ·
I suggest that you invest in a state of charge meter, such as the Balmar SmartGauge, BEFORE spending a penny on batteries. This will allow you to clearly see the actual SOC of your batteries, and get the maximum life from them.

Here is a link where you can buy one (and help the guy that has helped us all): Purchase A Smart Gauge Photo Gallery by Compass Marine How To at pbase.com

Disclaimer: I am neither affiliated, nor invested in Balmar, SmartGauge or Compass Marine. I'm only a happy customer. :)
 
#15 ·
5 years is very good. I also vote for a solar setup. A 50 or 100 watt panel With a nice controller would do wonders. Our boat sits in the slip with no shore power and a 50w panel I stow below underway, batteries are always floating in the low 13s. I would get a set of 6 volt golf cart batteries in series. They will take up the same space and cast about the same as the group 24s.
 
#17 ·
I'll take the batteries to get load tested. My local West Marine has a charger that load tests. If they are shot, I might have room for the golf cart batteries or I'll go with Mainsailes suggestion.

Thinking it through further, this is not a boat I will keep for more than a couple more years. I'm either relocating or getting a bigger boat. So I will be keeping the stock alternator until unless it dies. I will however investigate solar.

Probably a lower end set up from a reputable manufacturers that I can stow when not in use. It's a 30 ft racer/cruiser that I mostly day sail and overnight so I won't be adding big panels.

Thanks for the replies!
 
#18 ·
Hey,

Your needs sound similar to mine. My boat is on a mooring, gets day sailed about twice a week and weekend cruised 5-10 times during the season. I have minimal electrical needs - some lights, instruments, etc. On a weekend cruise I will use my DC powered Isotherm fridge, otherwise it's just ice.

I just don't see the need for solar or any special batteries, alternator, etc. I motor 10 minutes out of the harbor and 10 minutes back in. On a weekend cruise there is usually at least an hour a day of motoring and that's been enough to keep the batteries charged. My current (and previous) boat has 3 group 27 batteries. When the engine is on, the alternator (standard unit) charges all three batteries. When the engine is off I draw on two batteries and reserve one for the engine. If I am on cruise somewhere I spend at least 1/2 the time in a marina, then the boat is plugged in and the built in battery charger is on.

I have been using this set up for about 10 years and I see no need to change. I get about 5 years from a battery. I currently have Interstate SRM-27 batteries that cost about $100 (it's been a few years since I bought one) and that's it. That's about $20 a year for one or $60 / year for all three batts. Not enough to cash to worry about.

If I had higher requirements I would put up a solar panel or something but then I would need to worry about mounting it, breaking it, wiring it, and controlling it.

What is the problem you are trying to solve again?

Barry
 
#24 ·
A little follow up on this story.

I started this thread by mentioning that there is not much chance of me ending up on a slip for the season. Surprise surprise, here I am ending the season after a summer in a nice marina. It was damn expensive, but worth it to me. I did not sail as much but spent more time overall on the boat.

As to the batteries, I had them "load tested at my local WM. Not sure how accurate that was, they used a little hand held unit, and they said they where just fine.

I put water in the batteries early in the season and all seemed fine. Well I just checked the house bank and they took about 1/4 - 1/2 gallon to top up the two group 24 units. I hope I didn't fry them.

For weekend use at anchor or on the mooring they seemed just fine. I plan on leaving them on the boat this winter, hooking up the power a couple times a month and see how it goes in the spring.

I still have my mooring but this marina life is sort of addicting. Not having to schlep a dingy around the marina and make long wet trips out to the boat in marginal weather is making me lazy.
 
#25 ·
If you are leaving the batteries on the boat, I suggest disconnecting them from the electrical system. There are parasitic loads, and things that go bump in the night, that can conspire to drain the batteries (or worse).

I disconnect my batteries from the negative buss bar that I installed. I connect a battery tender to each BANK (not each battery) using the alligator clips, and leave them for the winter. So far, so good.
 
#26 ·
That's a lot of water (1-2 quarts?) to top up 2 batteries after about 6 months. Glad to hear they are serving your purpose, but I would wonder about charging profiles, if not battery health. Running that dry had to be an issue for the plates, but it sounds like you might be on borrowed time anyway.

Glad you're enjoying the slip.
 
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