Time to Replace Batteries

[Jmreim]

Power needs on my boat are fairly simple. When anchored we use lights (LED), fridge, light use of water pump for sink & toilet and perhaps charging some devices (iPad/iPhone). No genset so no AC or hot H2O heater. We do have an inverter and might use the microwave for coffee/tea in the morning.

The boat currently has 2 8D and 1 Group 31 battery. They all appear to be about 8 years old (the boat was new to me last Nov) and seem to be failing. I'm no expert and trying to learn all I can about battery types and configurations.

The yard has recommended replacement with the same configuration (2 8D and 1 Group 31) using AGM batteries.

Questions:
1) Is this the best configuration to use or should I be looking at other battery sizes?
2) if I change configuration, would that also require other electrical work that could be costly?
3) If I stay with the 2 8D and 1 Group 31, does anyone have a specific battery they think is wonderful?
4) Am I missing any other considerations here?
Thx -
Jim

 

[Comodave]

Are you using the Group31 for starting? And the 2 8Ds for house? If so the 8Ds are probably not what you want for house usage. I would use the 31 for starting and replace the 8Ds with 6V golf cart batteries. I am surprised that a yard would recommend staying with the 8Ds since they aren’t great for deep cycle usage. The gold carts are a much better deep cycle. You do have to change the wiring to have 2 sets of series and put the 2 sets in parallel. And make sure that they are hooked up properly so you are drawing across both sets and not just one set of series. Now would be the time to make the change but you will be much better off with the 6 V house bank and with 4 6V batteries you will have approximately the same amp hours as the 8Ds but better deep cycle.

 

[BruceK]

At 8yo they`ve done well. If what you have works, why change it? Sure 8Ds are heavy to move and fit, but they can come in deep cycle (here at least).
If you switch from conventional lead acid(sealed or not)to AGM,you might need to adjust your charging profiles. Maybe it`s not necessary, but check. TF member FF is good at charging profiles. Your charger might have an AGM setting,making it easy.

 

[rsn48]

Lithium is of course a wonderful way to go but you don't just purchased lithium batteries, it's a lithium system.

I advocate Firefly batteries as they are the next best thing to lithiums out there that aren't lithium. Below I'll link you to a Jeff Cote talk on Fireflies. [They are cheaper than lithium but more expensive that other Gelled batteries]

 

[firehoser75]

Jim,
I second the recommendation to move to 6V golf cart deep cycle batteries to replace the large, heavy 8Ds. The wiring changes needed are not really much on the scale of things.
If you are using AGM batteries now, then go ahead and replace them with AGM (except golf carts instead of 8D). However, remember that most boaters "murder" their batteries, they don't usually die from age (however, 8 years sounds pretty good). AGM's are even more sensitive to needing the correct charge profile and they suffer partial charge operation even less well than lead acid. Lead acid are cheaper to purchase as well, however, they do require checking the liquid monthly and topping up as needed.

If you cannot get the AGM batteries back to 100% charge regularly (at least once per week and better daily) they may suffer an early death. Rod over at Compass Marine has some great info on this subject with advice on recharging for best battery life. Probably on a cost per amp/hour basis, lead acid golf carts are hard to beat. However, there are possibly other considerations you may want to consider (eg. access to check the fluid levels, etc.).

 

[RedRascal]

Could you share what each battery supports currently? It will help to know what is used for starting, thrusters and house. Also do you usually like to anchor out for a couple days in row without starting an engine and need a few nights of power without recharging? Or is just one night on the hook more typical before motoring about the following day?

 

[catalinajack]

Why change? Because they yield about the same amphours in the same footprint as the 8Ds, the 8Ds are not true deep cycle batteries, and the 8Ds are monsters. The fact that the poser of the question got good performaance from his 8Ds is means little. I say this very respectfully of your opinion but this has been discussed many times on this forum and the broad consensus is always the same, ditch the 8Ds and go with golf car batterries. And if there is enough height and the allternator(s) are up to the task more amphours could be had by using L16s but these are indeed heavier than golf car batteries.

At 8yo they`ve done well. If what you have works, why change it? Sure 8Ds are heavy to move and fit, but they can come in deep cycle (here at least).
If you switch from conventional lead acid(sealed or not)to AGM,you might need to adjust your charging profiles. Maybe it`s not necessary, but check. TF member FF is good at charging profiles. Your charger might have an AGM setting,making it easy.

 

[oscar]

You could try and stretch them some more with an equalization......

 

[ranger58sb]

The boat currently has 2 8D and 1 Group 31 battery. They all appear to be about 8 years old (the boat was new to me last Nov) and seem to be failing. I'm no expert and trying to learn all I can about battery types and configurations.

The yard has recommended replacement with the same configuration (2 8D and 1 Group 31) using AGM batteries.

Questions:
1) Is this the best configuration to use or should I be looking at other battery sizes?
2) if I change configuration, would that also require other electrical work that could be costly?
3) If I stay with the 2 8D and 1 Group 31, does anyone have a specific battery they think is wonderful?
4) Am I missing any other considerations here?
Thx -
Jim

Jim, how are the batteries configured? Does the single G31 start a single engine, and the two 8Ds are configured as a single house bank?

Three G31s take up only slightly more space than each single 8D, and that would offer more cranking amps (if necessary) and more capacity (Ah). OTOH, more than four in parallel might be a bit less than optimal.

Six GC2 6V golf cart batteries (wired in series/parallel to 12V) would give you true deep cycle capacity, much more capacity, and will fit in the space of two 8Ds. (If your 8Ds are house batteries, this is probably the one I'd pick. Lifeline makes GC2-equivalent AGM GC2; see their GPL-4CT. Not inexpensive, so compare against other brands of G31 AGMs.)

A big advantage of G31s or GC2s versus 8Ds is that each individual battery weighs less, so you maybe don't have to hire a winch, professional wrestler, mule, and a dog to schlep the things...

-Chris

 

[Jmreim]

Yes - the G31 starts a single Cummins diesel (6BT5.9M) and the 2 8Ds are a house bank.

I checked on the GPL-4CT. If I understand your suggestion correctly, they're about $340 each ($2150 for 6). The 8D AGMs are $520 each ($1100 for 2).

 

[Jmreim]

Not really certain what each battery supports - I assumed the 8Ds combine to support all house functions and the G31 is for starting the engine. we'll generally motor each day - anchor a single night.

 

[Jmreim]

Thx - I'm unclear which specific Firefly batteries would replace my 8Ds - do you know?
And must I change all the batteries to Firefly or can my G31 be replaced with a conventional AGM?

 

[sunchaser]

JMR
When it comes to battery discussions on TF, you'll find no shortage of alternative ideas. Why? Because almost any half way rational approach works.

Since you're using some yard strong backs, forget about the weight issue. If you're planning on keeping the present electrical load usage, Bruce K's point about why change is worth considering. Give the previous owner a call and ascertain his usage and off shore power time. Then talk to the yard about $$ to go a different route.

Your money, your call. Take your time, there is no silver bullet.

 

[bayview]

You will get a zillion ideas including this one but IMO keep it simple. It worked for a long time so just replace what you have.

Now your anchor on the other hand........[]

 

[O C Diver]

While the 8Ds may have worked, in open lead acid, I don't believe you will find any that are true deep cycle. The 8D AGM batteries may be deep cycle. My preference would be six 6 volt golf cart batteries wired in series and then parallel. They should fit the footprint of the two 8Ds and are deep cycle.

Ted

 

[Gordon J]

Complicated question

Thx - I'm unclear which specific Firefly batteries would replace my 8Ds - do you know?
And must I change all the batteries to Firefly or can my G31 be replaced with a conventional AGM?

Fireflys require a charging regime which is different than other batteries. They also discharge differently. If you plan to charge and discharge together all must be same.

Other question, you can generally replace one 8D with two group 31 fireflys. On my boat, I replaced two 8D house batteries with three L-15s and both 8D starts with two group 31s. These are all one bank. I no longer have a start and house bank.

Both engine alternators are controlled with Balmar external regulators and the two regulators’ output is controlled by a Balmar center fielder.

I am very pleased with the results and expect I will never replace these batteries.

 

[FF]

"L-15s and both 8D starts with two group 31s."

If these are all deep cycle batts it should work fine.

IF the G-31 are start batts they will not last long in a deep cycle house use.

 

[Gordon J]

Not quite

"L-15s and both 8D starts with two group 31s."

If these are all deep cycle batts it should work fine.

IF the G-31 are start batts they will not last long in a deep cycle house use.

All 7 batteries are combined into one bank. Plenty of amperage/voltage to start Cummins 330 hp engines. Fireflies are not start batteries, and if you tried to use them alone - two group 31 - you would probably be right.

 

[Marlinmike]

I'm of the camp if it last 8 years you (previous owner) did very well, then again he may not have really stressed the system like you will be doing. Alot of good information in this forum, just take your time and let it sink in a little, my only advise is to try and keep it simple....

 

[firehoser75]

Jim,
You have received some good advice regarding battery types. Some of the new technology batteries are excellent, but fairly expensive, and most of them (lithium, firefly) require their own charging parameters that older chargers and internally regulated alternators will have trouble satisfying. So even though (for example) Firefly are great batteries, it may be quite expensive to change over (the whole system) to them?
If you are charging both of your banks (8d and G31) from the same source, then they should both be of the same type (AGM or Lead Acid for examples). If your only regular recharging consists of running the engine, and you don't have a "high output" externally regulated alternator, you are probably not getting your batteries up to even close to fully recharged. Also, most battery types require very long recharge times to completely reach 100% state of charge. Failure to reach this full recharge regularly will over time (number of cycles) damage the batteries shortening their life. Firefly will tolerate this "partial state of charge" operation very well (that is one of their strengths), but both AGM and lead acid will not.
If how you use your boat (also depends on your recharging setup) does not allow for a very regular recharge up to a full 100% (takes hours), then I advise you to buy the least expensive lead acid batteries (golf cart) (Sam's Club, Costco, etc.) that you can and just replace them more often. If you are like me and anchor out alot the only way I can reach 100% recharge regularly is with my solar panels or by connecting every few days to dock power. This info applies most to your house bank.

For more info on this entire subject visit www.marinehowto.com. He has some excellent info there.

 

[Baker]

Jim,
You have received some good advice regarding battery types. Some of the new technology batteries are excellent, but fairly expensive, and most of them (lithium, firefly) require their own charging parameters that older chargers and internally regulated alternators will have trouble satisfying. So even though (for example) Firefly are great batteries, it may be quite expensive to change over (the whole system) to them?
If you are charging both of your banks (8d and G31) from the same source, then they should both be of the same type (AGM or Lead Acid for examples). If your only regular recharging consists of running the engine, and you don't have a "high output" externally regulated alternator, you are probably not getting your batteries up to even close to fully recharged. Also, most battery types require very long recharge times to completely reach 100% state of charge. Failure to reach this full recharge regularly will over time (number of cycles) damage the batteries shortening their life. Firefly will tolerate this "partial state of charge" operation very well (that is one of their strengths), but both AGM and lead acid will not.
If how you use your boat (also depends on your recharging setup) does not allow for a very regular recharge up to a full 100% (takes hours), then I advise you to buy the least expensive lead acid batteries (golf cart) (Sam's Club, Costco, etc.) that you can and just replace them more often. If you are like me and anchor out alot the only way I can reach 100% recharge regularly is with my solar panels or by connecting every few days to dock power. This info applies most to your house bank.

For more info on this entire subject visit www.marinehowto.com. He has some excellent info there.

A most excellent post, sir!!! And I agree wholeheartedly!!

 

[FlyWright]

I replaced 2 lead-acid 8Ds of 225 AH each with 6 GC 6V LA batt pairs in series/parallel of 220AH/12V pair. I gained about 50% AH capacity in the same boxes that held the 2 8Ds. The GC sit an inch or two taller than the 8Ds.

The house bank costs about $600 at Costco. Great return/replace policy and easy access near my local waters.

 

[Larry M]

At 8yo they`ve done well. If what you have works, why change it?...

That’s what I would do if for nothing else from a cost standpoint. When removed our 8Ds, we upped the capacity and changed to 10 Trojan T105s. The batteries were about $1250. To replace all the wiring, lugs and heat shrink the cost was several hundred dollars just for materials. I was able to makeup the cables. If I had to paid someone to make the cables and rewire the new configuration, easily another $1,000. The batteries were the cheap part.

 

[Simi 60]

Why change? Because they yield about the same amphours in the same footprint as the 8Ds, the 8Ds are not true deep cycle batteries,

8D is a size designation
Plenty of 8Ds are deep cycle

Lifeline
Fullriver
Odyssey
Victron
Plus a multitude of other suppliers all have 8D deep cycle batteries

https://www.batteryequivalents.com/group-8d-batteries-dimensions-features-and-recommendations.html

and the 8Ds are monsters.

Yep, so I got the battery supplier and the electrician to put them in

The fact that the poser of the question got good performaance from his 8Ds is means little. I say this very respectfully of your opinion but this has been discussed many times on this forum and the broad consensus is always the same, ditch the 8Ds and go with golf car batterries

Usually only in the US where Trojans are cheap
Here in Australia I bought 250ah 8D, deep cycle AGM for about the same price as a single 6v Trojan.

If the Trojans cost you double the money and you weren't the one moving the batteries around would you still think they were the better option?

.

 

[rsn48]

Are Fireflies and Lithiums more expensive upfront, absolutely. Are Fireflies and Lithiums more expensive in the long run, absolutely not, lead acids are.

Battery expense is linked obviously to your budget, but other factors are in play as well. I completely reno'd my home in 2016, a back to the studs type of reno. Part of the reno was choosing a new roof. I look at and ordered Cambridge roofing. When I ordered them the guy said the were warrantied for 30 years, he had other products that would last longer. I told him in 30 years I'll probably be dead or sitting in a wheelchair drooling, by then I won't care, it will be my wife's problem.

So if you are in your late 80's or 90's, go FLA. If you are in your 50's and intend to keep your boat until you don't have the capacity to use it, then lithium or fireflies are the cheapest solution long term. Look for used inverter/chargers out there if you require a newer one to replace your old one, there are plenty, and in good shape.

Now I have successfully murdered 4 FLA's in my past. I also know I am a lazy idiot. So the murder was all my fault because I didn't do due diligence to their upkeep. So far no homicide charges are pending against me.

When I owned my Catalina sailboat, I hung out in the sailing forums. I still will go there for certain advise, then here second. The sailboaters are ahead of the curve when it comes to solar, batteries, Efoy, etc; anything that will keep you on the hook without a generator. The guy I am going to link you too was early in using Efoy at the Sailor's forum, he didn't like how is classic beautiful sailboat would look with solar panels so he went Efoy five years or longer ago. He then installed fireflies and he discusses them in a thread entitled "my attempt to murder my Fireflies..."

https://www.cruisersforum.com/forums/f14/my-attempt-to-murder-my-firefly-batteries-221607.html

 

[ranger58sb]

Yes - the G31 starts a single Cummins diesel (6BT5.9M) and the 2 8Ds are a house bank.

I checked on the GPL-4CT. If I understand your suggestion correctly, they're about $340 each ($2150 for 6). The 8D AGMs are $520 each ($1100 for 2).

In that case, I'd pick the Odyssey 31M-PC2150 for your start battery. Huge cranking amps, long life...

And yes, those prices sound about right. But.... you could also take capacity into account. Six 4CTs would give you about 660 Ah; two 8Ds would give you about 490 Ah. Still a cost factor for the 4CTs, but then you'd also have good deep cycling capability. Individual weight would be a driver, for me, but if you're hiring help then that might not influence your choice.

As I understand it, the Lifeline "deep cycle" 8Ds are probably really deep cycle products. Not aware of other AGM deep cycle competition; haven't seen an Odyssey 8D, maybe Full River but I have no experience with them...

You can also ask you battery warehouse place if they will match Internet prices. I think our 4CTs actually came in at about $270 each, a couple years ago.

-Chris

 

[Beaverlake]

I will again also put in a plug for one of the battery watering set ups. I installed one from Battery Watering Systems. The PO killed six Full River AGMs by using the wrong charging Magnasine inverter/charger profile - something I didn’t catch during the survey. He also killed two x 8d FLA starting batteries using the 20 year old OEM charger (twin Cummins 330).

I replaced the 6 AGMs with 8 Costco GC2/Interstates, the 8ds with 2 Grp 31 AGMs and the old GRP31 genset FLA with an AGM. I replaced the old engine start/gen start charger with a small NOCO Genius charger. Had to add a bunch of new battery boxes. Bought new marine 2/0 cable to replace corroded welding cables the PO had used. Purchased tools, crimps, shrink wrap. I did the work myself but had help getting the 8ds out of the boat.

All in I’m at about $1200 on the house side and about $550 on the start side. I have increased the house capacity by about 15% (yes, I know that FLAs have the least usable power of all the choices). The BWS set up makes maintaining the FLAs a non event and I’ve used about a half-gallon of water in the 8 GC2s since last May. We anchor out a lot and use the Genset about 2-3 hours per day. The NOCO keeps the AGMs topped off at the dock. This is not a “forever” boat.

The BWS set up opened my eyes re the FLA ROI for us, our usage, and ownership profiles. This summer we’ll be in the Desolation area for about 40 days and Barkley Sound for about 21 days. Come September I’ll have a follow up on how well this set up served us.

A few photos . . .

 

[ksanders]

Lithium is of course a wonderful way to go but you don't just purchased lithium batteries, it's a lithium system.

I advocate Firefly batteries as they are the next best thing to lithiums out there that aren't lithium. Below I'll link you to a Jeff Cote talk on Fireflies. [They are cheaper than lithium but more expensive that other Gelled batteries]

Be VERY careful with Lithium batteries.

Very few of the Lithium Ion batteries currently on the market meet the only standard currently in place for the marine industry which is...

ASTM Standard F3353-19 titled Standard Guide for Shipboard Use of Lithium-Ion (Li-Ion) batteries.

The ABYC will probably be coming out with a standard soon, but as of today this is the only standard specific to the marine industry.

I seriously doubt (but that is me speculating) that the ABYC standard will be less stringent than the ASTM standard which has very specific requirements for fireproof enclosures, disconnecting means, and battery management systems.

 

[FF]

Most watering can be avoided by installing Hydrocaps , if there is room.


Hydrocap |

 

[RickyD]

I'm looking at changing out my 2 Deka 8Ds with 6 Trojan J305 6vs. I will have to modify the box but checking Trojan website, they get really crappy reviews. What is your experience or better options?