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Old 05-21-2017, 12:22 PM   #1
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Time for new house bank

I have known this was coming, but the time is now. My almost 7 year old house bank with 3 Chinese made sealed LA 8D batteries is dying. I need to replace it and am trying to come up with options. I am hoping that you all can help me walk through the decision process.

I have a MagnaSine 2812 inverter charger and a 6KW genset. No solar at this time. The other batteries in the boat are an 8D AGM start battery of undetermined age, 2 original 8D sealed LA batteries for the thrusters, windlass, and crane, and a group 27 AGM genset start battery that is a year old.

The batteries are in the aft lazarette underneath the cockpit. They are not easily accessible with very little overhead clearance. In this same space are the thruster batteries, DC electrical panel, and a diesel hydronic furnace. I can changed the form factor of the batteries if needed.

I would prefer to not go with the 8D size again. They are simply hard to manage. However, I certainly can if that is going to be the best option. Watering batteries in this location will be tough. However, I could opt for a watering system if I went with wet LA batteries. I would prefer to spend as little money as possible (I am a sailor after all) but at the same time am looking at long term cost per kWh.

Here are the options as I see them. I am also open to others I haven't thought of.

Wet GC2 batteries - I can buy these at Costco for under $80 each with each pair giving me 210 AH. I could fit 8 to 10 where those three 8D batteries are now by changing the battery boxes. A watering system would keep them watered. It would take a bunch of cables but I figure for under 1 boat unit I could install everything. This would give me 800-1000AH of capacity, 1/2 of which would be usable so 400-500AH.

8D AGM - Other than the 160lbs each, this would be the simplest and easiest to do as three would drop in to replace what I have. More expensive at ~$1,800 for three of them. 700-750AH with about 350-375AH usable.

Firefly Oasis: I would prefer to be looking at this in a couple years instead of now. I'd like to have other folks get more experience with them. $500 each for 116AH. Can be discharged down to 20% SOC apparently, but doing that dramatically reduces the number of life cycles. They claim a 50% depth of discharge will give 3600 cycles, 80% will give 1000. That is still about 2x the number of cycles a wet cell GC2 would have at 50%.

I'm sure there are other options as well. I'm not interested in LiPo batteries at this point and I know there are other form factors which would be good to look at. AGM GC2?

For the way we currently use the boat most of the time, the Oasys is likely overkill. We primarily weekend the boat with an occasional week or two away from dock power. GC2 wet cells would be fine for us but I have an ignorant question. What risk is there to have the wet cells in the same space as the diesel furnace? What is the realistic risk of an explosion due to gas buildup in the same space as a flame?
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Old 05-21-2017, 01:31 PM   #2
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Do you want quick, simple and cheap or do want complicated, time consuming and expensive? Your time, your money, your degree of frustration and your decision.

Two questions- are you keeping your current battery electrolyte topped up and is your charging system doing ok?
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Old 05-21-2017, 01:40 PM   #3
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Time for new house bank

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DH

Do you want quick, simple and cheap or do want complicated, time consuming and expensive? Your time, your money, your degree of frustration and your decision.



Two questions- are you keeping your current battery electrolyte topped up and is your charging system doing ok?

Great questions. I would rather not go for time consuming and complicated. Changing the type of batteries wouldn't be bad. I've gone from 4D to GC2 in my sailboat and it isn't too big a deal. I don't mind changing the charge profiles on my charger, that shoudln't be too tough either.

Cheap is better than expensive but I don't mind spending more money to get more long term value.

My current (original) bank are sealed LA so no watering to do. Charging system for the house seems to be fine.

If a watering system works well, and if there isn't a safety issue with having the wet cells in the same compartment with the furnace, the GC2 wet cells would be a very strong contender. It should get me 5 years of good performance.
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Old 05-21-2017, 01:47 PM   #4
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It seems you can spend $1800 on the 8D AGMs and have some work to wrestle them into place, but then you are done. No cable modifications, no battery box modifications, no hold-down modifications, no watering system, etc.

Or you can spend $1000, then modify cabling, hold downs, boxes, and add a watering system. And after the inevitable dozen trips to the hardware store, you will probably be out another $200.

It's a pretty straight time for money tradeoff.

Personally I would swap for 8D AGMs and move on the the next project.
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Old 05-21-2017, 01:51 PM   #5
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It seems you can spend $1800 on the 8D AGMs and have some work to wrestle them into place, but then you are done.............Personally I would swap for 8D AGMs and move on the the next project.
When the letters AGM are spoken, one cringes at the cost. IMHO, they are worth every penny!
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Old 05-21-2017, 01:57 PM   #6
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It seems you can spend $1800 on the 8D AGMs and have some work to wrestle them into place, but then you are done. No cable modifications, no battery box modifications, no hold-down modifications, no watering system, etc.

Or you can spend $1000, then modify cabling, hold downs, boxes, and add a watering system. And after the inevitable dozen trips to the hardware store, you will probably be out another $200.

It's a pretty straight time for money tradeoff.

Personally I would swap for 8D AGMs and move on the the next project.


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When the letters AGM are spoken, one cringes at the cost. IMHO, they are worth every penny!

Good perspectives. I must admit to liking the idea of increasing Ah capacity by switching to the GC2s. OTOH, why bother having a son-ion-law if not to help wrestle 8D batteries?
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Old 05-21-2017, 02:02 PM   #7
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Although I'm a big proponent of GC2s in place of 8Ds, I have to agree with TT. The extra work and maintenance required for a LA GC2 replacement bank seems to outweigh the cost difference of $500-800. I'd also go 4D or 8D AGM if access is challenging.

On my boat, 3 GC2s fit perfectly in each 8D box. I replaced 2 8Ds with 6 GC2s without the need to modify or change the boxes. Access for maintenance is not an issue.
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Old 05-21-2017, 05:22 PM   #8
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almost 7 year old house bank with 3 Chinese made sealed LA 8D batteries is dying
This says to me your good usage pattern would allow you to invest, in a higher quality bank, without worrying about murdering them prematurely.

Top quality FLA like Rolls/Surrette if an easily accessed watering system would be a great bang for the buck, maximum longevity maybe 15+ years. Sam's Club (or Batteries+, Duracell brand actually East Penn) not Costco, GC2s are least up front, but will need replacing sooner, PITA project.


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GC2 wet cells would be fine for us but I have an ignorant question. What risk is there to have the wet cells in the same space as the diesel furnace? What is the realistic risk of an explosion due to gas buildup in the same space as a flame?
A good venting system should be in there anyway, AGMs vent too, just less.

If not "always" on, then set up to run for five minutes before spark sources.

------
If you decide to go AGM, then go Lifeline Odyssey or Northstar.

Firefly Oasis only for chronic PSOC contexts, seems to not be a problem for you.

Battery size obviously up to you, plenty of choices within above, maybe look at 2V cells.

Personally I would consolidate all those other batteries at the same time, replace the ancient ones to get a bigger House bank, and just put an LVD cutoff between the critical 12V units and the rest

So while the whole House bank is well topped up, they all share in all the loads.

But as Accessories usage pulls down SoC, that doesn't ever threaten Starters/bilge/windlass/thruster functionality.

Maybe some locations are "too far", wiring too huge, justifies keeping it separate, but 8D is a lot of Deadweight Lead to cart around for just occasional use for one specialized task.

The larger the One Big Kahuna Bank is, better for total AH capacity, surge power capacity when needed, shallower cycling means even better longevity. . .
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Old 05-21-2017, 05:50 PM   #9
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John, good thought there. At this point, I wasn't planning on messing with the thruster/windlass/crane bank. They are old, but don't get used much and seem to still be behaving well.

I need to really look to see how well that space is vented. My first thought is, not super well. There is a large hatch over the center of it, that is not sealed to be water tight. It has a channel around the edge to drain the water. There would be plenty of air exchange there. Much better than the venting on my sailboat anyway.

Currently, the Costco Batteries are Interstate GC. That is what I used the last time for my last boat. I was pretty happy with them. I could use the existing battery boxes for 8 GC2 batteries and just have a bunch of link cables made up.

I certainly understand the idea of consolidating the batteries. However, I just pulled up 160' of chain and a 60' anchor while every other system that runs on the house bank was telling me the SOC was really low. It was nice having a separate bank to handle that. I just think that my thruster/windlass is oversized for the task with 2 x 8D batteries. As you mention, that is a lot of weight to haul around to use occasionally.
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Old 05-21-2017, 05:52 PM   #10
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John, you mentioned an LVD cut-off. I am not familiar with that. What is it? How does it work? It almost sounds as if it is something that would isolate a section of batteries once the SOC drops to a certain point?
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Old 05-21-2017, 05:54 PM   #11
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Firefly Oasis: I would prefer to be looking at this in a couple years instead of now. I'd like to have other folks get more experience with them. $500 each for 116AH. Can be discharged down to 20% SOC apparently, but doing that dramatically reduces the number of life cycles. They claim a 50% depth of discharge will give 3600 cycles, 80% will give 1000. That is still about 2x the number of cycles a wet cell GC2 would have at 50%.
The Trojan -105 Golf Cart 6v batteries I use have a claimed life of 1200 cycles. From my experience that is about right. You comment would indicate GC2s with a life expectancy of 500 cycles.
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Old 05-21-2017, 05:59 PM   #12
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Because of poor access-AGM.
Because of poor ventilation with flame source - AGM.
You can find AGM golf cart batts or someone to wrestle the old out and new 8Ds in.
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Old 05-21-2017, 06:14 PM   #13
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Because of poor access-AGM.
Because of poor ventilation with flame source - AGM.
You can find AGM golf cart batts or someone to wrestle the old out and new 8Ds in.


Yup. If it wasn't for the poor access and the flame source, I would definitely go with 6V wet cells.

Anyone have any ideas as to whether the GC2 AGM are as robust as their wet cell counterparts?
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Old 05-21-2017, 06:21 PM   #14
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I would recommend against Rolls/Surrette. I bought into the mystique for an off grid house and it was a big, costly mistake. Support was non-existent from factory. I have had two cells fail, and both times it took 3+ months to get replacements. The first was under warranty in the first year of use, and shipping cost as much as the battery would have. The second replacement I bought through a dealer with shipping included in a larger order he had placed. While waiting for the 3 months to get replacements, I had to run the bank at 46v nominal instead of 48v, but fortunately all my gear was sufficiently adjustable to do that.

Never again.
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Old 05-21-2017, 06:31 PM   #15
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Most ACR/VSR will also work as Load low-voltage disconnects.

But these usually have fixed setpoints for opening (isolating) and closing (combining).

Also many aren't of sufficient ampacity to handle large loads "across" the device, just charging a Starter from sources attached directly to a larger House bank.

Immediately coming to mind as large-amp capacity AND adjustable setpoints are

Samlex, which has a 200A "Battery Protector",

Victron BatteryProtect has 100 and 220A

both the above, setpoint choices limited but sufficient

InterVolt (Australia) PSR (not sure if their newer EBI Pro will do), both variable in .1V increments

Blue Sea 7635

Newmar

It's actually pretty basic functionality, with a large solenoid Arduino could do it, but marine robustness. . .

Since you're able to just fire up the genset on demand, you really could have almost all the various batteries on board act as one big bank, distance/wire size permitting, while SoC is high.

A Reserve bank kept completely separate "just in case" against disaster, dead shorts, could be also used for specific occasional uses, set up switching so different Load groups could be reassigned to another bank as needed. Cranking engines is such a tiny short use, but critical, should be set up so easy to do from either bank.

Doing it that way, then the LVDs maybe no longer needed.

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Old 05-21-2017, 06:41 PM   #16
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When the letters AGM are spoken, one cringes at the cost. IMHO, they are worth every penny!


Amen

Maybe it was due to accessibility in my Owens but I'll never own anything but AGM in another boat/rv application. There's enough crap to maintain without paying good money to drag more maintenance down the gangway. My time is limited 8D AGM is the no brainer plug and play solution if I woke up in your shoes David. Pay a young man a $100 and tell him to wrestle the damn things for you.

Now if you're retired and in search of a hobby by the 6V FLA and top them off to your hearts content.
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Old 05-21-2017, 06:46 PM   #17
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I feel your pain Dave . I think I cooked my house bank a few years ago . I didn't know any better and I was leaving the inverter on charge mode with the generator running when we were traveling . I have an extra high output alternator on the main engine that was enough to keep everything topped off, plus a 120 watt solar panel . Finally somebody here in TF told me to turn off the charge while traveling . I have 4 6vgc batteries for house and 8d start battery and group 27 start for generator. It takes some maintenance to keep them watered, but for the most part they are easy to get to . I bought mine at napa . I got pretty good deal because they only had one more month to stay on their shelf before they send them back . So far so good . They are about 3 years old I think .
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Old 05-21-2017, 06:58 PM   #18
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Dunno about these, from Latvia

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Old 05-21-2017, 07:01 PM   #19
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Although tempting to just replace your house bank you might be better served in the long run to consider what would be an optimum configuration. To me that would involve eliminating the seperate thruster/windlass/crane bank. One or more of those items could be on your start battery given that the engine will always be running when they are used. If you do ultimately want just one large bank (plus start battery/bank) then best to have all the batteries in the bank of the same age.

First up I would get all of your 8D's load tested to determine how much life they have left. If the thruster etc bank is getting towards the end of its life then biting the bullet on replacing them as well and creating one large bank could well be worth doing.

For batteries, take a look at the Odyssey PC1800 FT. AGM, so a bit more expensive. But you can buy from Port Townsend Shipwright's CoOp - they sell large quantities of them and get unbeatable prices for them. They can be used for start as well so you could have just one battery type other than for the genny start battery. This allows simplified charging, and periodic rotation of start battery through the house bank.
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Old 05-21-2017, 07:53 PM   #20
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Great suggestions. I had wondered about combining the start with the thruster. My recent issues with a poorly running engine makes me a little gun-shy. However, using an ACR to charge those should be good. I was thinking that even if I wanted to maintain the same form factor (8D), maybe I could use 2 8Ds for thruster and start, instead of the 2 8Ds for thruster and another 8D for the start?

OTOH, I kind of like Johns suggestion of just making one big bank for house, thruster, windlass and leave the start isolated. All 5 of those 8Ds are in the lazarette. The two banks are separated by 6-7 feet. Not too bad. That would be a total of 1250 Ah. Since I have a separate start battery, plus a genset battery, I should ever be in the position where I couldn't raise the anchor.
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