Can I use a pair of Ampere Time 12v 100Ah batteries for starting an engine?

I have a 3 battery lead acid battery bank. 1 battery is starting the starboard motor. The other 2 batteries in parallel are the house and starting for the port engine. 5.7 liter Merc fuel injected I/Os. I would like to replace the 2 house batteries with ampere time 12v 100Ah batteries. I would leave the single starting battery as is lead acid. Obviously the house batteries are where I need the extra capacity.

I was hoping to leave the existing Charles Industries C-Charger 5000 20 amp in place for the AC converter. The manual states:

When properly installed and connected, the C-Charger will automatically charge and maintain the batteries. When power is applied, the C-Charger will enter a bulk or “constant current” mode, during which a higher rate of charge is achieved to fully replenish the batteries. When the batteries near a full charge, the output current will decrease and the charger will enter a timed absorption mode. After four hours in absorption mode, the output will drop to a float rate to maintain the batteries at a temperature compensated finishing voltage approx 13.6 volts.

The 13.6 volts seems like its on the edge, but its also simple enough to just turn it off and not float for long periods. But it can't be that critical for me to monitor, so if I am running the generator/AC over night and it reaches a full charge and goes into float until the morning.

Most importantly over several days when using the boat and the generator is running I would charge the house LifePO4. In storage I would use a morningstar PWM sunsaver 20 amp charge controller set to AGM with a 120v panel.

from my reading lithium are not good starter batteries . yours 280 amp max surge draw
i know cars pull high amps but not sure boat is similar you need to find how many amps the starter uses and how often you start . starter batteries are made for short high draws lithium steady rate draws
i seen complaints on amazon from people using single in there car . . and since lithium has come down to 400 for 100ah starter batteries can be bought less than 100 . walmart has batteries as low as 58 bucks about 5 sizes plus trade i got one Monday so your risking 800 to 2k batteries where 60 will work fine. add small maintain solar to just starter batterie for 30 bucks . good luck

Jr233 said:

from my reading lithium are not good starter batteries .

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I am using lithium ion in my motorcycle and highly recommend them. 1/3 the weight (or less), much smaller, and they hold their charge a lot longer, especially when sitting idle. As you mentioned, I also don't know the specs on a boat motor, but I would not dismiss lithium.

Here's a youtube by @HighTechLab - won't answer your specific question but gives some 'context' that you might find useful.

Different LFP cells have varying discharge characteristics. Some like Headways can discharge a 10C for brief periods. Those would be perfect for a starting battery.

In anticipation of using LFP to start my 24 HP 3 cylinder diesel, I put a clamp on amp meter on the starter an was surprised to see 500-600 amp draw while starting. In retrospect, this makes sense for a diesel as they typically have a compression ratio of 20:1.

As suggested, I’m going to stick with lead acid for starting and use LFP for house service.

iamrich said:

I am using lithium ion in my motorcycle and highly recommend them. 1/3 the weight (or less), much smaller, and they hold their charge a lot longer, especially when sitting idle. As you mentioned, I also don't know the specs on a boat motor, but I would not dismiss lithium.

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mc lower demand. i failed to add car type altimeter's are not good to charge lithium due to the difference of how lithium take charge is much higher amp than lead acid without a device added there's many articles and you tubes on that. now there might be lithium designed to drop inti internal combustion starters . often when called drop in it mean for house batteries in RV which get charged from mains
check will prose rv as well as his you tubes and book on amazon main thing 100 ah 12v are lower priced
350 but still a deep cycle marine battery can be had for under 100 and does decent starting job add a 10 watt solar to maintain 25 -30 bucks . for most solar lithium is the way don't forget lithium cannot be charged under 32f or 0 c so if cold start but cannot let it charge unless you have heat pad