Duracell House Bank not doing it...

[jefndeb]

Hello,

The PO installed two of the Duracell Model SL18DA batteries in Feb of 2019 for the house and one for the starting battery.

However this past weekend on the hook, only showing about 10-12 amps DC load, (running the fridge) via the inverter, I was at 80% withing 5 hours.....didn't seem to add up right.

The house bank is also used for both the bow & stern thrusters so I guess thats why he picked these more-or-less starting batteries.

I sorta expect to run the genset an hour in the morning for coffee & maybe microwave and then one more time in the evening to run the AC to dehumidify the cabin etc and top off the house bank, but I didnt expect the batteries go down that fast..

Reading the spec of these batteries they look like Sams type Truck cranking batteries....

I cant even find an Amp Hour rating for these??

Not sure if I should just deal with it as is....

 

[DavidM]

Those are 8D starting batteries and using one for house service is probably causing it to fail prematurely.

You are right, thruster usage is a bit like starting- heavy current, 100 amps or so for 10-20 seconds at a time. But deep cycle batteries can handle 100 amps for a short while just like they do in powering an inverter to run a microwave.

So replace the failing 8D with a pair of GCs or Group 31 AGMs. See my article on this subject in the Library section of this forum.

David

 

[Comodave]

My boat originally came with 8Ds, at least that is what it seems. A PO went to 6 volt GC batteries and that is what I would do in your shoes. They are much easier to get in and out and they are a true deep cycle. I put in a stern thruster a couple of years ago. Used a dedicated AGM battery for it on it’s own 15 amp charger. So far it has worked great. I was able to put the AGM right next to the thruster so the cable run is short and I get good voltage to the thruster.

 

[Pete Meisinger]

A couple things jump out at me. Using a standard "D" to run an inverter and ultimately the refrigerator is not a good match. Refrigerators are a heavy draw and can kill a battery pretty quickly. IMHO you are doing real well if you only drew it down to 80% in five hours. I never had good long life out of "D" batteries. Two seasons was all I could get. Plus you really don't need the size and weight of a "D" for a starting battery, especially in Florida.

Get a few group 27 deep cycle batteries for the house and a 24 or 27 starting battery. If you have twins you may want to consider a pair of starting batteries, wired separately.

pete

 

[jefndeb]

Do you think I should keep this starting battery as it is since it seems to be pretty much what its designed for and focus on the house bank first?

 

[DavidM]

Your 8D will work fine as a starting battery. That is what it was made for. But if you ever have to replace it, a G31 has 900+ CCA and will start your engine just fine and will weigh much less than the 8D.

David

 

[jefndeb]

Yeah, those things look they will be a buger to move outta there...

 

[Xsbank]

There is probably already an inverter built into your fridge so you might gain some efficiencies running it on 12volts.

 

[jefndeb]

Yes sir, I tried turning off the fridge AC breaker and turning on the DC breaker but the temp dropped fast so I guessed that wasnt the best option...

 

[boathealer]

12A for 5 hours is 60Ah. If that is 20% of your indicated SOC, then 5 times that woudl be around 300Ah capacity.

Typical 8D Ah are around 230-250Ah capacity, IIRC. Depending on your SOC = 0% setting, this could be just about right for what you have.

 

[jefndeb]

OK, so you are saying that the reading are normal for what I am seeing? with this type of wet cell batteries...

 

[boathealer]

OK, so you are saying that the reading are normal for what I am seeing? with this type of wet cell batteries...

Based on what you provided, *I* think so. Would be good to know what your SOC meter threshold is set to for "0% remaining".

Others - am I missing something?

 

[jefndeb]

ok, here is a pic of the summery page I set up showing the data.....this is a moment when the fridge/freezer compressor I think was idle...I also forgot to mention thaere there is also a dang ice maker upstairs on as well....

 

[rsn48]

I frequently reference a well known electronics and electrical guru - Jeff Cote - working in the PNW and BC area. He says some PO's install starting batteries as they look just like proper FLA batteries when selling their boat, they get to say they just installed new batteries to the unwary prospective buyer. He says if you use those starter batteries for you boat house bank your odds of experiencing a nasty battery explosion goes up exponentially. Starter batteries are not designed to take on extended heavy loads, just a quick short high load, then recharged.

Here is a Jeff Cote video discussing various battery options for your boat, the good news is he talks about starter batteries near the beginning of this video, its an hour and a half long vid but if you aren't familiar with boat batteries and which ones to use and why, this will be well worth your time to watch the whole thing:

 

[ranger58sb]

Yes sir, I tried turning off the fridge AC breaker and turning on the DC breaker but the temp dropped fast so I guessed that wasnt the best option...

That shouldn't have happened. Doesn't sound exactly like a battery (capacity) issue. Maybe it's not actually/properly connected or otherwise has some wiring issues, etc.?

In any case, suggests you need to take a look at that as a potentially separate problem.

-Chris

 

[jefndeb]

Wow, that video is one of the best I have seen, very clear and well spoken presentation from Jeff Cote

I think I will investigate the Firefly 31 AGM batteries being that I now, thanks to that video, feel that our Amp Hour budget will be around 200-225 per day.

But these Firefly AGM G31 are over $540 each at 116 AH......??..i would need 3 each....ouch

I also see the Duracell 31DTMAGM is $180 each at 105 AH...??,,,worth a try at that price??

Are the firefly batteries really work all the extra cash?

 

[FF]

"Are the firefly batteries really work all the extra cash?"

A better question is can you reduce the battery loads?

A fridge AND an ice maker on any battery setup will be really difficult to not kill.

 

[Pete Meisinger]

Sure, keep the "D" for engine starting, just don't expect it to last more than a couple years.

I know, lots of people get longer life out of a "D" but I didn't. Plus they are expensive and difficult to move.

pete

 

[bayview]

80 % is more than enough to get you going the next day. Why are you concerned.
Reefer tricks to reduce battery drain are freezing water to keep it cold with no power. Reducing constant opening and closing. setting it t a colder temp when running genny, use a cooler chest for cocktail's etc to reduce opening.

 

[ghost]

If your amp hour budget is 250/day, then you need to budget around 500ah bank so you don’t daily discharge more than 50%. That’s for a single night. If you are doing multiple nights then you will not get back to 100% charge because you can only bulk charge to roughly 80% ish depending on how long you can sit through an absorption period. So to get the quickest charging rate, add another 20%. So to have room to grow, I would not go less than 600amp hours personally.

This is the math that caused me to evolve the last ten years until my bank is now around 1200ah. We haven’t even discussed whether you can charge sufficient to the bank size either...

 

[jefndeb]

Thanks for all the comments and suggestions...

Is there really such a thing as a dual purpose 8D AGM Battery? ...one that, within reason, truly can be deep cycle for house loads but also provide large momentary current loads for a thruster?....and if not, which side do they tend to lean towards? cranking type or Deep cycle type?

I ask this because it would be ideal if I could simply replace the 2 existing 8D house batteries (that also run the thrusters) with 2 8D AGM giving me close to 475 AH......

 

[Bacchus]

I took that route several yrs ago and bought 3 East Penn 8A8D AGM Intimidator line. They seem to have decent ability to do both and the specs are available online. My Mainship has 2 8Ds for a combined house / start and a 3rd dedicated to bow & stern thrusters.
The MS arrangement with start & house combined (with a 1-2-all-off sw to manage use) doesn't make a lot of sense but I really wasn't interested in a major rewire job at the time.

I am currently starting to develop a plan to replace these when needed and will likely go with either multi AGM GC2s or GP 31s AGMs.

While they have served me well and never let me down re start, house or thruster use - The 8Ds are monsters and dont provide any benefits IMO. I will not do it again and wouldn't recommend it.

 

[ranger58sb]

Is there really such a thing as a dual purpose 8D AGM Battery? ...one that, within reason, truly can be deep cycle for house loads but also provide large momentary current loads for a thruster?....and if not, which side do they tend to lean towards? cranking type or Deep cycle type?

Often labeled "marine" or "dual-purpose" and with both cranking amps and capacity (in Ah) listed in the specs. And "deep" won't be as "deep" as with a traction battery, but probably an OK compromise given your goal.

Pretty sure East Penn/Deka, Trojan, Interstate, etc. all have flooded ones... and West Marine probably stocks a flooded one too, made by one of those (East Penn?) and more expensive than if from big box stores.

Not sure all of those make AGM versions; I think East Penn/Deka does. Shop the others too.

Then there's Lifeline AGMs. They do make a starting line and a "deep cycle" line. I don't remember specs for their "deep cycle" line, but if it includes cranking amps it's probably a choice. Likely much more $$$ than the other brands.

Last I checked, Odyssey does NOT make an 8D form factor... We've been using banks of 3x Odyssey 31m-PC2150s in a space slightly larger than a single 8D to get huge cranking amps, more capacity (~300 Ah compared to ~245 Ah), and so far 11-12 years as house duty in a duel-purpose set-up like yours. Odyssey is like Lifeline, also $$$ compared to the others.

I've read Northstar and Full River are also decent AGMs; don't know if they have dual-purpose 8Ds but that'd be worth a check, too.

-Chris

 

[firehoser75]

If you are having to replace batteries that are "not working" for you, you will now have multiple options. One option is to just replace what you have now. This is the easiest choice from a "making changes" point of view.

Personally I would not go back to those huge, heavy, 8D's if for no other reason as they are hard to move around, besides not being true deep cycle!!
If you are planning on keeping your boat for a long time, then considering the Fireflies is a good idea. They will suffer operating with a partial state of charge very well. This is what kills most other types of batteries (coupled with depth of discharge). They should give you a very long life (maybe even be the last batteries you will ever put in your boat?), and they can be regularly discharged to a much lower level than most other battery types allowing a smaller amp/hr capacity overall maybe even resulting in taking up less "footprint" space. They also accept a higher charge rate compared to alot of other battery types. The bad news, they are expensive (initially, but maybe not overall), and you may need to make some wiring and charging system changes as well. Some research is obviously in order if you want to consider these batteries.
If not Fireflies, then I would strongly suggest Golf cart batteries. These are readily available in both flooded and AGM (various reasons for one over the other), are true deep cycle, and are much lighter and easy to handle compared to 8D. However, it would require some rewiring and maybe new battery boxes.
If you do not go with Fireflies or some other battery type that tolerates POC (partial state of charge) operating, then I would also suggest installing solar to better enable reaching a full charge regularly to increase battery longevity. Then your could "bulk" charge your bank using the generator in the morning allowing the solar to top them off during the rest of the day.

 

[jefndeb]

Yes sir,

I see 3 Firefly 31 AGM would be around $1500,... but then 2 Northstar 8D AGM would also be about the same price....at $699 each

The concern I have is that our thrusters are currently fed from the house bank (2 8D Wet Cells)..(not sure if Mainship did this at the factory but it looks factory installed).....it would be close to ideal if we could just replace these 2 8D with the same footprint (except AGM) with a battery that is a true "Dual Purpose " battery,.. to run the house loads but also the thrusters ...i know they are very heavy to install as well,

 

[FF]

There are many differences that make a long term difference in battery types.

Deep cycle batts do well as start batts , thruster batts or for a windlass , if there are enough of them.

The starts have lots of plate surface area so maintain a high voltage as big amps are pulled , until the plates are covered with gas.They recover quickly as the gas leaves.

If you have near the same surface area , say 2 batts instead of one , the deep cycles will do a fine job of big amps for a short time..They will gas the plates too.

 

[ranger58sb]

Yes sir,

I see 3 Firefly 31 AGM would be around $1500,... but then 2 Northstar 8D AGM would also be about the same price....at $699 each

The concern I have is that our thrusters are currently fed from the house bank (2 8D Wet Cells)..(not sure if Mainship did this at the factory but it looks factory installed).....it would be close to ideal if we could just replace these 2 8D with the same footprint (except AGM) with a battery that is a true "Dual Purpose " battery,.. to run the house loads but also the thrusters ...i know they are very heavy to install as well,

I hadn't noticed the part about your thruster...

Check out Lifeline's GPL-8DL 12V deep cycle battery. 255 Ah and very respectable cranking amps.

https://lifelinebatteries.com/products/marine-batteries/gpl-8dl/

In many cases, somebody's "marine" or "deep cycle" 12V battery is just a decent (or sometimes, less so) dual purpose battery. In Lifeline's case, they project 1000 cycles to 50% Depth of Discharge (DoD) for their 6V deep cycle batteries, and I suspect that applies to their 12V deep cycle batteries, too. (I only have a few years on our "new" Lifeline 6Vs, though, so can't speak to our own longevity experience yet.)

This will also be expensive, but it seems to offer what you want.

Sometimes you can get a real-world price at a local dealer... if you ask. I asked whether our local guys would match Internet prices when I switched one bank to Lifeline GC2s, and they did. Saved a boatload.

-Chris

 

[jefndeb]

ok, thanks Chris,...so if I can find an 8D AGM with a CCA rating thats a little higher than average, with about 225 AH, it would be a fair compromise?

That would give me a about a 450 AH with the two batteries, not bad...

 

[firehoser75]

Using what are termed "dual purpose" batteries will probably result in a relatively short lifespan when compared to a properly sized true deep cycle battery system, if used for a house bank. This is not necessarily a bad thing, as long as you are not expecting different results???
It is also my understanding that AGM's may be even more "sensitive" to partial state of charge (not regularly fully (to 100%) recharging) use than flooded batteries, possibly resulting in a shorter than optimal lifespan?
Again, it may not be an important consideration for you and how you plan on using and maintaining your boat.

 

[ranger58sb]

ok, thanks Chris,...so if I can find an 8D AGM with a CCA rating thats a little higher than average, with about 225 AH, it would be a fair compromise?

That would give me a about a 450 AH with the two batteries, not bad...

Well, you really only need enough cranking amps to start your engine and run your thrusters. Your thruster specs may speak to minimums. And then it's an additive spec in parallel at 12V, so 1000 CCA for one battery means 2000 CCA for a pair...

Using what are termed "dual purpose" batteries will probably result in a relatively short lifespan when compared to a properly sized true deep cycle battery system, if used for a house bank. This is not necessarily a bad thing, as long as you are not expecting different results???
It is also my understanding that AGM's may be even more "sensitive" to partial state of charge (not regularly fully (to 100%) recharging) use than flooded batteries, possibly resulting in a shorter than optimal lifespan?

Given the boat is designed with that dual-purpose thing in mind... as is ours... we've found it easy enough to just live with it. I could probably have improved our system by breaking off each start bank and forming an independent house bank. Lots o' work, rewiring, etc... and it was easier for me to just add capacity to each of our dual-purpose banks with good batteries. And for one bank, I did eventually change it to 6Vs... which are starting that diesel OK so far.

I've read that about AGMs and "partial state of charge" (PSOC) operations, hazards of not fully recharging after a cycle, etc. Hence Firefliy batteries, too Lots o' discussion on cruisersforum, 'cause apparently it's mostly cruising sailors who kill their batteries by not recharging... because they can't, seldom get to a dock with shorepower, don't have solar, etc. Rod (CMS/MaineSail) has details about it on his site, and I think he's talked about it here, too.

We haven't particularly noticed a problem in our own case, but then we're often at a dock with shorepower on, chargers one, etc.

-Chris