Changing Battery Size? 4x L16 to 8x GC2?

My house bank needs to be replaced, and I'm thinking of swapping from 4x 6v L16 AGM batteries (@120 lbs each) to 8x 6v AGM golf cart batteries (@55 lbs each) for easier replacement and handling. In fact comparing the amp hours, the GC2 batteries would get me 880 AH vs the 800 AH (at 12V) that I currently have. I'm trying to figure out if there's any downside?.... it doesn't seem like it? Other then I'll need to build a shelf to store them all. Anyone have any insight?

Thank you!

If you have reasonable access & can hire some muscle to exchange them, another less expensive option is replace the existing AGM’s with 6v FLA L16’s. You will gain Ahrs, and very durable - expect 7 yrs+ if you avoid DOD<50%. Deka through NAPA are hard to beat.
Either way if you switch to GC2’s or L16 FLA, invest $100 or so in a battery minder system. Watering becomes a 5 minute task, don’t have to even open battery boxes. The easier it is to maintain FLA, the longer they last.

IMO, if you are staying with lead acid batteries, then stay with L16, taller and less footprint. 8 GC2 will cover twice the footprint

SteveK said:

IMO, if you are staying with lead acid batteries, then stay with L16, taller and less footprint. 8 GC2 will cover twice the footprint

Click to expand...

Sticking with AGM, which is what I currently have. The footprint would be the same, but the hight wouldn't. I'd be having a battery shelf built, so it would be 4 GC batteries on the bottom shelf, and 4 GC on the top.

Shelf would have a footprint of 24" L x 16" W x 30" H

Have you considered LiFePO4?

Two of these would give you 920 AH, weigh 87 pounds each.

Delta Riverat said:

Have you considered LiFePO4?

Two of these would give you 920 AH, weigh 87 pounds each.

Click to expand...

This is a good question. With the cost difference between AGM and LiFePo4 you could cover the conversation cost while loosing hundreds of pounds and gain more battery capacity.

mliemon2 said:

Sticking with AGM, which is what I currently have. The footprint would be the same, but the hight wouldn't. I'd be having a battery shelf built, so it would be 4 GC batteries on the bottom shelf, and 4 GC on the top.

Shelf would have a footprint of 24" L x 16" W x 30" H

Click to expand...

I have long been a fan of GC2 batteries, even flooded LA batteries. When I needed to replace a couple of 8d batteries (really odd chinese sealed LA battery that was between a 4d and 8d size) I went with 4 x L16 6v AGM because of the space I had available and found a very good deal on them. Yeah, they are heavy, but it was easier to get them in than it was to get out the old batteries. I did it myself using some tackle arrangements. In your case, I would tend to either stay with the L16 format, or look at going to LiPo.

If I had to replace my L16s now (may be sooner than later as a power outage just caused them to be deeply discharged) I would go with LiPo. As Delta pointed out, you could get 920 AH with two of those LiPo 8ds. Frankly, you could get one of those and still come out ahead of 8 x GC2s. The 880 AH of the GC batteries is going to give you 440 usable AHs at 50% state of charge. I try not to take my AGMs down that far as 50% discharge will still greatly reduce battery life over say a 70% SOC. Just one of those 460AH batteries would give you almost 370 AH at 20% SOC and have a much longer life. Two of them would give you over 730 AH at 20% SOC. 8 x GC2 AGMs are going to run you what $2,000? You could get two of those LiPo batteries for maybe $2,500. Certainly worth considering.

OTOH, if you have the space, you might consider FLA GC2s. If you can get a watering system, you would spend $800 or so on 8 of them at Costco. I've used them on a prior boat and they actually work well. However, you need to water them.

I have the same L16 house bank.

If I were to replace my house bank today I would probably use one of these.

Go from 440 pounds total to 164 pounds total in about the same square foot of floor space.

Go from 420 AH useable (at 50% discharge) to 920 amp hours usable.

At a cost of fairly close to FLA

mliemon2 said:

My house bank needs to be replaced, and I'm thinking of swapping from 4x 6v L16 AGM batteries (@120 lbs each) to 8x 6v AGM golf cart batteries (@55 lbs each) for easier replacement and handling. In fact comparing the amp hours, the GC2 batteries would get me 880 AH vs the 800 AH (at 12V) that I currently have. I'm trying to figure out if there's any downside?.... it doesn't seem like it? Other then I'll need to build a shelf to store them all. Anyone have any insight?

Click to expand...

If the house bank is isolated from start and thruster functions... (sounds like it is?)... I think I'd first look at LiPo alternatives.

Otherwise, I'd probably hire some muscle to swap new L16s for old. Saves engineering/building a new mounting system for 2x GC2s...

-Chris

If you asked this question 3 years ago I would have said stick with the LA L-16 as the best bang for the buck. Now three years latter and the market place has flipped. The best bang for the buck is now LiFePo4 batteries. If you feel you need AGM’s then definitely look at cost savings of converting to LiFePo4.

One thing I didn't see mentioned is; are you setup to change from charging FLA (yes AGM are a FLA battery) batteries to LI batteries?
There are different charging requirement between the 2.
To do it right could require additional outlays to make the conversion work.
It isn't just a swap out of 1 for the other unless you don't care about a potentially boat fire.

It isn't just a swap out of 1 for the other unless you don't care about a potentially boat fire.

Click to expand...

A little extreme don't you think.

Nepidae said:

One thing I didn't see mentioned is; are you setup to change from charging FLA (yes AGM are a FLA battery) batteries to LI batteries?
There are different charging requirement between the 2.
To do it right could require additional outlays to make the conversion work.
It isn't just a swap out of 1 for the other unless you don't care about a potentially boat fire.

Click to expand...

AGM is not an FLA battery. It is lead-acid chemistry, but it does not have liquid electrolyte, which is what the Flooded in FLA refers to.

And they need a different charge profile too.

Except for the extended high current draw in bulk (alternator protection) you can charge LiFePO4 on a lead system with no danger of fires. You just won't get them completely charged.

On the other hand, if you charge Lead chemistry with lithium chargers you will have problems. Destroy AGM and boil FLA's dry.

LifePo4 are currently so much cheaper than L-16 or AGM that the savings will pay for the additional equipment needed.

A yard is going to quote you $30,000 to convert. A DIY could do it for $3,000.

Warning, this is not a DIY project for electrically challenged individuals.

Even ABYC admitted they were unable to get LifePo4 batteries to catch fire. Any fire talk applies to all batteries equally.

And Li Time even has the ABYC stamp.

Yeah, you have to pay someone to remove those Lead-Acid clunkers from your boat, but you can DIY the LIFePo4 yourself.

And you can trust me too because I did it -

No, I don't think it was a little extreme.

Just recently there was a fire attributed to the Lithium batteries and while they didn't think that the batteries self-combusted (more likely the improper installation of the batteries) it was a boat fire and Lithium batteries were involved.

Would you like to be the boat next to the one that caught fire, I sure wouldn't want to be and unfortunately there is no way to know whether a boat has improperly installed Lithium batteries.

As also stated, it isn't a swap out from AGM batteries to Lithium batteries. While some may be able to DIY with the changeover most wouldn't know where to start.

Therefore, do NOT attempt a switch from FLA batteries unless you are a knowledgeable person with a high level of marine electrical work behind you, unless you'd like to have a boat fire.

Hope I made my position clear on this topic.

Nepidae said:

As also stated, it isn't a swap out from AGM batteries to Lithium batteries. While some may be able to DIY with the changeover most wouldn't know where to start.

Therefore, do NOT attempt a switch from FLA batteries unless you are a knowledgeable person with a high level of marine electrical work behind you, unless you'd like to have a boat fire.

Hope I made my position clear on this topic.

Click to expand...

I don't know where to start on most things that I've never done before.

I think that prudence is always warranted but very bad things can happen with boats. Fuel leaks can result in boat fires. Propane leaks can result in boat fires. A multitude of electrical issues can result in boat fires, not just Lithium batteries. However, the percentage of boat owners that always hire a professional to do all of the above is very small, at least in my plebian circles. While boat fires do happen, they are rare considering the amount of ignorant fools like me that are messing around with boats.

What is the mystery of Li batteries. Seems like the nay-sayers like to promote the hazards of explosion or boat fires. Only the extremely experienced should dare to even connect the leads to them.

The charge and potentially discharge profiles are different. So if the inexperienced attempts the incorrect charge profile, are they inherently dangerous, or do they just not charge efficiently.

I had some LAs that got pretty hot once. Never got to the real cause. I suspect the inverter/charger dumped too many amps into them.

Sparks around the hydrogen can make LAs explode.

So, I guess only the professionals should install LAs also.

Aside from proper cable, fuse, terminal sizes and a balance system, what's the big deal with Li.
It would be nice to know, even for the inexperienced, because I've found that quite a few of the so-called professionals aren't always as knowledgeable as they think.

Nepidae said:

Therefore, do NOT attempt a switch from FLA batteries unless you are a knowledgeable person with a high level of marine electrical work behind you, unless you'd like to have a boat fire.

Hope I made my position clear on this topic.

Click to expand...

The same cautions would be in order for any significant electrical or fuel system work. A reasonable boat owner will either understand the systems well enough to safely do the work, or hire a qualified tech. There are lots of ways to do unsafe things on boats but LFP doesn’t need to be any riskier than most other system mods.

I agree. It doesn't take much study to learn the proper LiFePO4 protocol. They have been around now for a long time.

Don't confuse LiFePO4 (lithium-iron-phosphate) with LiPo (lithium polymer), the latter is the one most often involved in thermal runaways and also the most common in small apps like cell phones, laptops, power tools, ebikes as they have a very high energy density to pack a lot of power in a small size.

I'm more afraid of the silly goof ball crap I find on my boat all the time done by previous whiz-bangs than I am of my LiFePO4 install which I have carefully installed and monitored only after re-documenting the existing wiring and maintaining isolation.

Yeah, if you want it done right, do it yourself!

I have no complaints of my own work.

Nepidae said:

No, I don't think it was a little extreme.

Just recently there was a fire attributed to the Lithium batteries and while they didn't think that the batteries self-combusted (more likely the improper installation of the batteries) it was a boat fire and Lithium batteries were involved.

Would you like to be the boat next to the one that caught fire, I sure wouldn't want to be and unfortunately there is no way to know whether a boat has improperly installed Lithium batteries.

As also stated, it isn't a swap out from AGM batteries to Lithium batteries. While some may be able to DIY with the changeover most wouldn't know where to start.

Therefore, do NOT attempt a switch from FLA batteries unless you are a knowledgeable person with a high level of marine electrical work behind you, unless you'd like to have a boat fire.

Hope I made my position clear on this topic.

Click to expand...

If you just swap from FLA to LifePo4 you won’t cause a fire. You might destroy an alternator or you might destroy the batteries themselves.

LiFePo4 is less likely to be involved in a fire than FLA batteries. Of course, ignorant people go “oh, boat fire”, “boat had LiFePo4 batteries”, “must have been the batteries”. More likely the fire was caused by a poor connection that generated enough heat to start a fire. Poor connections happen regardless of battery type involved and large battery banks are able to supply more fuel regardless of battery type.

One should be more afraid of large battery banks than the type of battery being used.

I'll add that I have more fear of lead acid batteries than I do of LiFePO4.

The lead acid generates hydrogen and oxygen when charging - explosive
The acid might leak - corrosive
The explosion might happen when I'm really close - corrosive acid in face

The LiFePO4 are in a sealed waterproof ABS case with a current limiting BMS
Proven to not catch fire even with severe abuse
BMS will shut down to prevent overcharge and also shut down to prevent over discharge.