Hot off-gassing house batteries?

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I’m late to this thread. Clearly the bank now needs replacing. Lots of good advice here. However, there is some important information that is missing:

1) What is the typical 24-hour demand on your DC system? I.E. how many amp hours would your bank be depleted over a 24 hour period?

2) How sizeable are your inverter loads?

3) Prior to your problems, what was the typical or usual “state-of-charge” of the bank before you start to recharge?

4) Do you bring it up to a full state-of charge-regularly? Preferably daily, or at least every other day?

5) Do you have solar panels to bring the bank up to a fully charged state?

Answering these questions will guide you on what changes you should be making as to whether to change technology to LFP, and also sizing the bank properly.

FWIW, I have a 900 AH, Trojan T-105 bank. I have replaced my batteries twice. I got 9 years out of my first replacement, which was 1125 AH and there was still life left in it. I downsized it to 900 AH, because with solar, I rarely went below 85% SOC. I then got a Starlink, which raised my inverter use and overall loads considerably. Had I known about the demands of using the Starlink, I would have remained at 1125 AH. I add more water, more regularly than before. Upgrading to the LFP batteries is a no-brainer for some on this Forum, but it would require upgrades to the charging and monitoring systems, particularly the alternator, which are costly. I’m not keeping the boat past my current battery purchase. So it’s not just about comparing battery costs.

Hope this helps.

Jim
 
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Jim,
While we wait for answers to your good questions

Why do you only use 15% of 1125Ah. Even if your needs are more, say 25%, is the size of your bank intended for multiple days on the hook with battery power?
 
Steve: at anchor on a sunny day, the batteries would be fully charged until 7:00 pm. Overnight the inverter would be off, fridge and freezer using 10 amps per hour, 12 hours, 120-150 amp hours. So so perhaps down 13-15% at the lowest point of the day. Turn the genny on, for an hour, putting in 70 amps or so. Solar carries the house loads and brings the house bank up to nearly full state of charge by 6:00 pm. That was a typical pattern for us.

Now with the 900 amp hour bank, with the inverter on and Starlink on, the hourly load was perhaps 17 amp hours. Now the bank drops down to 200-250 amp hours overnight, perhaps 70% state of charge.

Our pattern is to run the genny in the morning and either use solar (most days) to bring the batteries up to 100% or travel and charge the batteries with that approach.

Jim
 
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Jim, thanks for your explanation.
I was expecting multiple days without GEN use at anchor.
IMO, your use cyclevmakes the bank too large as compared to my use.
I use 50% of 800 Ah and recharge, rinse repeat.
Can do two days without recharge. Not worried if bats only last 5 years, instead of 10.
 
Steve: Well batteries are expensive and I want more than 5 years on them, so I care how they are cabled. Any low-hanging fruit I can pick to keep them healthy, I will do. The original battery bank was sized by the PO, pre-solar panels. I replaced the bank in 2014, pre-solar. So we did use them multiple days at anchor. I put 435 watts of panels on in 2016 and it was a game changer.

At anchor, we want hot water, and use the genny for that. At the same time, running the coffee pot and heaters to load up on the genny. We put maybe 40 hours on the genny last year. Hardly anything.

Jim
 
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You have 5 year old batteries. That is the life expectancy of wet cell lead acid batteries. You will here of people who get more years. It is rare and many times they never take them off the dock. Take specific gravities on all cells. The ones that are bad will read low. You may spend a lot of time hoping to get an answer. The fact is wet cells last 5 maybe 6 years. Every car battery I have had for 40 years lasted 5 years. I have 8 golf cart batteries in my boat. First set last 6 1/2 years. The last 6 months were a pain due to overheating. The current set last slightly less that 5 years.
Good LiFePo battery prices have come down on par with the same wet cells. They are now priced better than AGMs.
IMHO
 
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