Basic AGM battery replacement

[TSweather]

After reading countless posts on this site regarding the future of battery technology (fascinating stuff), I am looking for input on what used to be considered a 101 level basic swap of new batteries for old ones.

Our boat is a 2003 TPI build with the standard Balmar alternator, Promariner ProNautic built in charger, and two group 31 AGM house batteries rated at 950CCA each. These batteries have served us well since 2018 when we purchased the boat, but are now barely able to start the engine after powering our electronics through a 3hr race.

Is there anything I should consider while swapping in what will likely be Lifeline brand 100ah replacement batteries? Open to other brands, though I'm admittedly a bit lost in the world of modern AGM considerations.

Also, we do not have any type of battery monitor on the boat and I have been considering the addition of a Victron BMV-700 to the nav station.

I'm hoping to make this as simple as possible seeing that my strengths are in weather, rigging, and composites, not electronics.

Thanks, Todd
#41

[Vento Solare]

Todd,

I have been happy with both the Lifeline GPL-31T and Odyssey Extreme ODX-AGM31M AGM batteries.

I had a Lifeline battery for 7 years and when load tested at 20amp discharge rate got about 80% of the rated capacity. I keep one of my old batteries at home charged in case there is ever a problem so I can do a quick swap. Two years ago I swapped to the old battery thinking I had a problem. It turned out there was a corroded power connection to the NMEA-2000 bus that needed to be reterminated. I cruise, race and do some distance racing. I can go 12 hours with reefer and instruments on before I need to charge. When cruising I will turn off the reefer after an evening charge and will turn it on again in the morning. Never a capacity problem.

I have the standard Xantrex Link 20 Battery monitor that came with the boat.

[Dan Corcoran]

Odyssey Extreme Batteries (these are TPPL lead acid batteries), they charge a bit faster giving you more usable capacity per lb.

ABYC, recognizing that TPPL batteries can more easily jump the fuse on a short to create a fire, now requires the same serious fuses as they do for lithium batteries = 5,000 AIC per 100 Ahr making a T fuse a good additional investment.

[TSweather]

Thanks guys, really appreciate the input.

Follow up question for you Dan as the addition of a "t-fuse" was part of the confusion that I was having with your prior write-ups. Would you be willing to link me to one that I could use for this specific application? Guessing I would need one for each of the two batteries? Is there just one that goes on the battery terminal itself so I don't need to crimp new cables? I saw the spec of 5,000 AIC per 100 Ahr, though some of these batteries are 105Ahr and don't seem to even mention TPPL in their descriptions.

I just don't want to guess my way through adding a "safety" feature that is spec'd wrong that will leave me without electronics at a critical moment.

Thanks, Todd

[Vento Solare]

Todd,

The standard J/109 system is fused between the alternator and the battery for charging. If you have the optional "systems group" that included the high capacity 110 amp alternator, you could replace the fuse setup with this GoPower Class T Fuse Block Kit from Defender.

[Dan Corcoran]

Getting back to you on your fuse question. Bluesea systems are top rated products. Whenever I buy something else to save money, I find something strange about the alternate product, usually around how it mounts.

Option 1: T-Fuse, 20,000 AIC. Good up to 400 Ahr of TPPL or Lithium battery
https://www.bluesea.com/products/500710 ... 10_to_200A

Option 2: Less expensive, but you need space over the battery 10,000 AIC. Good up to 200Ahr of TPPL or Lithium battery
https://www.bluesea.com/products/5191/M ... 30_to_300A

[TSweather]

Thank you Dan and Bill for the really helpful advice and for pointing me in the right direction. Our boat does have the 110 amp Balmar alternator, so I'll look for the fuse, though I do not recall ever seeing it before. Otherwise that MRBF terminal fuse block looks like a solid option to include on each battery.

The boat is a 2003 and left TPI before the Xantrex monitors were being installed, so I can only monitor batteries by using a multimeter. This is why I'm planning to install the Victron battery monitor.

Todd

[Vento Solare]

Todd,

The fuse on Vento Solare is mounted inside the engine compartment mounted on the port bulkhead just behind the removable stairs. It is just above the voltage regulator which is also bulkhead mounted. See picture below with the large diameter red leads.

[Dan Corcoran]

I have a fuse there also, which makes sense when the alternator is the source of current you want a fuse near by. Similiarly there are fuses on the cables for the shore chargers.

To be clear, none of these fuses need not be upgraded with the Odyseey or other TPPL lead acid batteries under the ABYC standards, but rather the fuse in the battery compartment near the battery needs to be 5,000 AIC per 100Ahr of battery. I don't recall what my 109 came with in the battery compartment, it just made sense to use the T-fuse. Since then the prices of T-fuses have skyrocketed.

[Dan Corcoran]

Courtesy of ChatGPT:

Here’s a clear summary of ABYC (American Boat & Yacht Council) requirements for fuses on marine batteries, focusing on what matters for safety with systems like lithium or lead-acid batteries:

Purpose of Fuses

Protect wires and equipment from overcurrent that can cause fires.

Prevent battery or conductor overheating in the event of a short circuit.

Key ABYC Standards

ABYC standards most relevant to battery fusing include:

E-11 (AC & DC Electrical Systems on Boats)

A-31 (Battery Installation and Safety)

Requirements include:

Fuse Size:

Fuse must be rated no higher than the ampacity of the wire it protects.

Typical rule: Fuse rating ≤ 150% of the wire’s ampacity (depends on ABYC subsection).

Fuse Location:

Within 7 inches (18 cm) of the battery positive terminal (closest point of origin).

Protects the entire wire run to prevent shorts along the cable.

Fuse Type:

Marine-rated fuses (UL-listed for marine use) are required.

Types: ANL, MEGA, Class T, or equivalent, depending on system voltage and current.

Redundancy / Multiple Batteries:

Each battery bank or parallel battery must have its own fuse.

Main switch doesn’t replace the need for fuses.

Lithium vs. Lead-Acid:

Lithium batteries require specific fusing for high short-circuit currents; ABYC recommends fuse sized for battery maximum short-circuit current rather than just wire ampacity.

Lead-acid batteries typically use fuses sized for wire protection only.

Practical Takeaways

Every positive battery cable must have a fuse within 7 inches of the battery.

Fuse rating must protect the wire, not just the equipment.

Use marine-rated fuses only.

Lithium batteries may need higher-rated, fast-acting fuses due to their high short-circuit capacity.

Fuses are required for each battery, even in a bank.

[Dan Corcoran]

Also from ChatGPT

ABYC standards do address fusing near alternators, though the requirements are a bit different from battery terminal fusing. Here’s the breakdown:

Fuse (or Circuit Protection) for Alternators

According to ABYC E-11 (DC Electrical Systems):

DC output from an alternator must be protected against overcurrent.

Protection can be a fuse or circuit breaker installed as close as possible to the alternator output terminal, usually on the positive output wire.

Key Points

Purpose: Protects the alternator and wiring from short circuits or faults.

Fuse Type: Marine-rated fuse or DC-rated breaker capable of handling the alternator’s full output.

Sizing:

Must accommodate the normal maximum output of the alternator without nuisance trips.

Must interrupt in case of a short-circuit (manufacturer specs often guide exact rating).

Relationship to Battery Fuses

Fuses at the battery do not protect the alternator.

Both are required:

Battery fuse → protects wire from battery to loads.

Alternator fuse → protects alternator and alternator wiring from overcurrent.

[Dan Corcoran]

Lastly, you also want an alternator protection device wired into the engine compartment as well, especially if your battery has a battery management system (BMS) that can cut off the battery suddenly.

Here is more info:
Sterling Power Pro Protect 24v Alternator Protection Device Overview:

The Pro Protect is a highly effective alternator protection device which prevents high voltage back EMF spike events that can destroy your alternator's expensive regulator and internal diode pack. These events can be caused by:

Loose wiring
Failure in a split diode/relay charging system
Switching off engine electrical power while engine is running
Defective rotary battery selector switches
Failure of a fuse in alternator's circuit
Any of the above events, and many more, could easily destroy the sensitive components of an alternator; this device will prevent damage from these events by diverting any high spike to ground, and is effective for full-power to no-power fault events. The Pro Protect is designed to absorb/divert spikes in excess of 36v in 24v nominal systems.

Please note that this device is sacrificial by design: a severe voltage spike may destroy the device; the point is that the spike destroyed the device rather than your alternator.