Any thoughts on results of my battery test?

[Frank Langer]

Hi,

I have two 86 amp group 27 gel cell deep cycle batteries wired in parallel for the house battery and one group 24 wet cell deep cycle for our starting battery. I have a Heart Freedom 1000 Link 10 inverter/charger, and when cruising for a weekend or a week at a time, use about 98 amps per day at most (refrigerator, cabin lights, instruments, stereo, water pump, etc.). I monitor our useage carefully, and tend to "baby" the batteries, never letting them get even close to 50% discharged.

The group 27 batteries were replaced in May, 2001 and the group 24 in May, 2007. However, the boat had little use between 2005 and 2008 before we retired. As we are planning several cruises this summer, I had anticipated that I might have to replace the group 27 batteries due to their age. But I decided to test them to see how they fared.

I borrowed a hand load tester from West Marine, and the batteries showed the following:

Group 24 wet cell deep cycle, rated at 575 Marine Cranking Amps showed voltage of 12.41 and MCA of 675 (I don't understand how it could be higher than it's rated for???)

The first Group 27 gel cell deep cycle rated at 700 MCA showed voltage of 13.38 and 673 MCA; the second showed voltage of 13.22 and 678 MCA.

I didn't absolutely trust the hand held, so took all three batteries to a local battery shop for testing. They put all three under load, and I could see that none of them dropped below 10 volts during the test. They said the group 24 was undercharged by about 25% and recommended I recharge it a bit. But they think the batteries are fine and no need for replacement. As they are in the business of selling batteries, I figure if they think they can't sell me a new one, then probably mine really are ok.

Any thoughts on all this? I like the idea of not having to replace them yet, as they are very expensive, but I also don't want to be caught short while out cruising.

Thanks,
Frank

 

[bayhoss]

Gut Feelings

Frank, I've been in your circumstance a hundred times. On one hand all measurments and tests say that something is fine. On the other there is the nagging fear of something being prone to failure. For myself I use the logic of if it failed how much would I be willing to pay to get out of the jam caused by the failure.

If I would pay more than the cost of the part, I buy the part then and there and think no more of it. If I could make do, then I plan for doing just that.

Hope this helps,
Frank

 

[rwthomas1]

I have a pretty robust charging system in my boat but no monitoring. The reason is I don't really go that far so a house battery failure would be annoying but not life threatening in any way. When the batteries go I'll put in new ones.

Your situation may be different. Depends on how far you plan on cruising, duration, etc. Coastal cruising from civilization to civilization in short hops should be no issue. The batteries die, pull in and replace them. Now if you are going off the beaten path, more than a few days sail from the world, then things change.

You did not mention instrumentation. Since batteries don't die an instant death, generally, you should be able to see a trend in loss of battery performance over time and know when they are due. A monitor would be nice to have while cruising anyway.

My house batts came with the boat, they are marked '00 for year. I don't work them hard and keep them charged up. As long as they give me service I will use them.

RT

 

[u079721]

Given the age of the house bank, I would for sure replace them - just for the peace of mind.

And if it were me, I would replace the starter at the same time, just so I wouldn't have to worry about getting the engine going after draining the house down. But then I tended to cruise in remote areas where you could not easily pick up new parts. If you don't usually drain your house bank too low, and can rig the engine to start from the house bank, then you could use the house bank as a back up for the engine battery - in which case you could save some by getting another year or two out of the engine battery.

Which is not the answer you wanted to hear - but just think of what an inconvenience it would be to have the batteries die while anchored out somewhere.

 

[Akavishon]

dunno myself ...

I don't speak from personal experience (having replaced my battery bank last year), but I've heard people say something like "milk the batteries as long as you can; for emergencies, carry a cheap portable jump start pack".

http://www.nextag.com/battery-jump-start/shop-html

Again, it's not from personal experience, but it does sound like a workable solution ... maximizes battery life, and may protect against emergencies.

Zoran

 

[tadslc]

A little off subject but I didn't think you should charge gels and wet cells together. Or for that matter AGM and wet cells.

 

[Frank Langer]

Tad, you are right that it's best not to charge different batteries. However, I think I need gel cells not only because the inverter manufacturer recommended them but more importantly, because they are stored under the quarterberth where we sometimes have a guest sleep, and I don't want them exposed to hydrogen gas.

I could replace the wet cell starting battery with a gel cell, but cost is a bit of a factor.

The house bank is separated from the starting battery, though I can charge either separately or all together. I have my charger/inverter set at the level to get the right charge for the gel cell batteries, which leaves the wet cell a bit undercharged. I periodically top up the wet cell with my car charger as it can add an extra charge beyond what is good for the gel cells (at least that's what I've been told).

Always open to suggestions though...

Frank

 

[u079721]

Sounds like Frank is on top of the charging issue with the two different battery types. IIRC the issue is mostly one of the proper float voltage, with the float voltage for gels being something like 0.5 units lower than what is common for wet cells.

But as for the replacement battery type, please don't NOT get wet cells because of concern over "dangerous hydrogen gas" in the cabin. The hydrogen gas given off on occasion is not toxic, and the only danger is an ignition hazard if it can collect somewhere. Being lighter than air it is not going sink in the bilge as would propane, and the cabin roof is certainly not air tight enough to hold it in. My wet cell batteries were under the starboard settee, and there was never an an odor problem, and they were very convenient to reach for service.

Wet cells are great technology, and will last a long time, IF maintained. But if you are going to put your batteries out of sight where you won't check on them often, then gel cells would be the way to go.