Hot off-gassing house batteries?

Being this is my first trawler and experience with larger battery banks, I’m looking for input on whether I’m doing something incorrectly that is reducing the life of the house bank, and will compromise batteries going forward, or whether this sounds like standard end of life for battery bank.

• Purchased the boat 3- years ago and from the previous owner inherited inverter/charger (Magnum Pure Sine 2810) and house batteries (six, 6-volt Trojan 145 golf cart batteries wired in series-parallel to form a 12-volt bank). Batteries were reportedly purchased 5-years ago (Sept 2019)
• The system has operated smoothly for the past three years, performed general maintenance from the start, monitoring water levels, keeping batteries clean, and have not changed POs charge settings, and have observed float charge to be a consistent 13.5-volts.
• Over the past year specifically, and progressing over the last couple months of noticed more and more voltage drop to the point where the battery monitor indicates I’m at 80% capacity, yet the voltage is dropping into the low 11-volt range after an hour or two with pretty low load (< 10amps)
• I’ve also notices that in the past few months the batteries (specifically the forward pair) have required more DI water than previously to keep them topped,
• After returning from our trip in September I noted temperature of the forward pair of batteries was elevated when hitting them with a temp gun, temps topped out about 107 degrees (I’m in Alaska so ambient is relatively cool). Temps seemed to cool the following day but were still elevated. The other four batteries, including the battery with the temp sensor were at ambient temperature. I topped all the batteries off with DI water and left for two weeks.
• Upon returning to the boat, I again noted elevated temps on the forward pair of batteries (in the 90-degree range) and upon inspection of the cells, three of the six cells in the first two batteries were observed to be dry, with water well below plates. I added water, but temps stayed elevated and significant gassing was audible. Wanting to get another 10-day cruise out of the boat I decide to remove that pair of batteries from the system and went forward with a four-battery bank.
• In the two days prior to leaving port, I monitored the four-battery bank with a temp gun and found battery temps to be at ambient temps.
• We went cruising for the next ten days and the bank functioned sufficiently, still dealing with relatively quick voltage drop,
• Upon returning to port and charging them for a day or so, I again heard audible off-gassing. Hit the batteries with a temp gun, and these batteries temps were elevated into high 80’s, with consistent off-gassing.

I’m confused as to why the forward two batteries in the six-battery bank got hot, with the other four batteries at ambient, and then when I removed the forward two batteries, the center two batteries got hot. I should note that while my inverter battery monitor displayed a 13.5-volt float charge. I never did put a multimeter on the batteries to confirm the charge was accurate.

My plan is to replace the entire house bank, but I don’t want to mindlessly go out and purchase new batteries, if there is a problem with the system.

Thanks for your input! -Ryan

You may have shorted out a battery cell. As open lead acid batteries age, they shed lead off the plates which eventually builds up in the cell until it shorts out. That is my understanding anyway as I have never experienced it. With the shorted cell, it depletes the other batteries as it's the lowest voltage. It also heats up. That battery is toast. If all the batteries are of the same age, many may be nearing that point and the bank should be replaced.

Ted

Yep, dead battery in there. You can find which one(s) by pulling all the cables and letting them rest overnight and then check resting voltage. They’re old though, so no sense in putting in only one or two. Put all new in and be done.

Just had a thought. You might want to check out your series/parallel wiring scheme to see if you’re using best practice.

I agree, lead is sloughing off of the plates and settling down in the bottom and builds up enough to short the plates.

A bit surprising as Trojan GC batteries have extra space below the plates to avoid shorting, but all of the symptoms point to this.

So replace them with the same kind. Should last as much as ten years.

David

Check the specific gravity of each cell, see if there's a big difference - which points to a bad cell. Testers are cheap at any auto parts store.

Its battery time, replace them all. One or more is dragging the entire bank down. Went through the same issue with my genset battery recently. It was 10 years old so I wasn't surprised it was shot.
And whatever you do don't continue to charge a off gassing battery, it's a real mess when they go boom... and it can happen.
HW

I can tell you the two hot ones are not the problem. They are the ones doing all the work. Still it doesn’t really matter, the whole bank now needs replacing as there are now a combination of dead cells and damaged cells.

Why this happened? Possibly bad luck with a defective cell from the beginning. Possibly too many repeated deep draw downs of the bank. Possibly imbalance of the connections to place batteries in series/parallel.

I do not see a temperature sensor to control the charge, so it seems to be overcharing since 2019.

I agree with the assessment. I will add that it is always worthwhile to carefully check your charging system before replacing batteries. That would include cabling configuration and charging voltage program. It is too easy to assume batts are the only problem and damage new (expensive) batteries before you figure out that there may also be a charging problem.

Greetings,
Mr. R. I'm a big fan of checking specific gravity (SG) of individual cells on occasion. As Mr. JC notes in his post (#6), any significant difference in readings indicates a bad cell AND the testers are dirt cheap (boat-buck-wise). Needn't be done every time you service the batteries IMO but perhaps every 6 months OR if you think you may have battery issues.

At the current Trojan replacement prices, I would be tempted to switch to 100Ah
or so lithiums. They have become cost competitive at the same usable amp-hours.
If the inverter charger can be configured to charge them properly it's a win-win.

hollywood8118 said:

Its battery time, replace them all. One or more is dragging the entire bank down. Went through the same issue with my genset battery recently. It was 10 years old so I wasn't surprised it was shot.
And whatever you do don't continue to charge a off gassing battery, it's a real mess when they go boom... and it can happen.
HW

Click to expand...

Yep, turned charger off prior to leaving the boat.

tiltrider1 said:

Possibly imbalance of the connections to place batteries in series/parallel.

Click to expand...

For a novice, what exactly does that mean? Thanks, Ryan

SteveK said:

I do not see a temperature sensor to control the charge, so it seems to be overcharing since 2019.

Click to expand...

There is a temp sensor on the bank, connected to the negative on the aft most battery. I'm reading that maybe it is more appropriately place on the center battery.

RT Firefly said:

Greetings,
Mr. R. I'm a big fan of checking specific gravity (SG) of individual cells on occasion. As Mr. JC notes in his post (#6), any significant difference in readings indicates a bad cell AND the testers are dirt cheap (boat-buck-wise). Needn't be done every time you service the batteries IMO but perhaps every 6 months OR if you think you may have battery issues.

Click to expand...

Routinely check SG is something I have been lax on. Will definetly incorporate into my program going forward.

I appreciate all of the replies and information! -Ryan

You can get a battery tester fairly cheap and check each battery.

ryastu said:

There is a temp sensor on the bank, connected to the negative on the aft most battery. I'm reading that maybe it is more appropriately place on the center battery.

Click to expand...

I recall that the temp sensor should be on the negative terminal which comes to the bank as that would be the hottest. I see it on the last negative post at the tail end.
ETA: corrected, not positive (thanks Dave post 20) Bad memory

Promariner says to hook the temperature probe to the negative terminal. Don’t know about other brands.

Comodave said:

Promariner says to hook the temperature probe to the negative terminal. Don’t know about other brands.

Click to expand...

Have not had a temp sensor since LFP installed. Post 19 corrected

ryastu said:

For a novice, what exactly does that mean? Thanks, Ryan

Click to expand...

Here is a proper explanation SmartGauge Electronics - Interconnecting multiple batteries to form one larger bank

JackConnick said:

Check the specific gravity of each cell, see if there's a big difference - which points to a bad cell. Testers are cheap at any auto parts store.

Click to expand...

JackConnick said:

Check the specific gravity of each cell, see if there's a big difference - which points to a bad cell. Testers are cheap at any auto parts store.

Click to expand...

Jack, just gave you some good advice and this is what you need to do the job. https://i5.walmartimages.com/asr/4e...eba00_1.faa959c5d2da41424ef1f696304b5cd6.jpeg

ryastu said:

Being this is my first trawler and experience with larger battery banks, I’m looking for input on whether I’m doing something incorrectly that is reducing the life of the house bank, and will compromise batteries going forward, or whether this sounds like standard end of life for battery bank.

• Purchased the boat 3- years ago and from the previous owner inherited inverter/charger (Magnum Pure Sine 2810) and house batteries (six, 6-volt Trojan 145 golf cart batteries wired in series-parallel to form a 12-volt bank). Batteries were reportedly purchased 5-years ago (Sept 2019)
• The system has operated smoothly for the past three years, performed general maintenance from the start, monitoring water levels, keeping batteries clean, and have not changed POs charge settings, and have observed float charge to be a consistent 13.5-volts.
• Over the past year specifically, and progressing over the last couple months of noticed more and more voltage drop to the point where the battery monitor indicates I’m at 80% capacity, yet the voltage is dropping into the low 11-volt range after an hour or two with pretty low load (< 10amps)
• I’ve also notices that in the past few months the batteries (specifically the forward pair) have required more DI water than previously to keep them topped,
• After returning from our trip in September I noted temperature of the forward pair of batteries was elevated when hitting them with a temp gun, temps topped out about 107 degrees (I’m in Alaska so ambient is relatively cool). Temps seemed to cool the following day but were still elevated. The other four batteries, including the battery with the temp sensor were at ambient temperature. I topped all the batteries off with DI water and left for two weeks.
• Upon returning to the boat, I again noted elevated temps on the forward pair of batteries (in the 90-degree range) and upon inspection of the cells, three of the six cells in the first two batteries were observed to be dry, with water well below plates. I added water, but temps stayed elevated and significant gassing was audible. Wanting to get another 10-day cruise out of the boat I decide to remove that pair of batteries from the system and went forward with a four-battery bank.
• In the two days prior to leaving port, I monitored the four-battery bank with a temp gun and found battery temps to be at ambient temps.
• We went cruising for the next ten days and the bank functioned sufficiently, still dealing with relatively quick voltage drop,
• Upon returning to port and charging them for a day or so, I again heard audible off-gassing. Hit the batteries with a temp gun, and these batteries temps were elevated into high 80’s, with consistent off-gassing.

I’m confused as to why the forward two batteries in the six-battery bank got hot, with the other four batteries at ambient, and then when I removed the forward two batteries, the center two batteries got hot. I should note that while my inverter battery monitor displayed a 13.5-volt float charge. I never did put a multimeter on the batteries to confirm the charge was accurate.

My plan is to replace the entire house bank, but I don’t want to mindlessly go out and purchase new batteries, if there is a problem with the system.

Thanks for your input! -Ryan

Click to expand...

Hi..I’m no expert,but I just replaced my 2(232ah) 6 volt batteries in my house bank after 4 years…figured your good if you get 4-5yrs…just my 2 cents,Mike

Pieyed47 said:

Jack, just gave you some good advice and this is what you need to do the job. https://i5.walmartimages.com/asr/4e...eba00_1.faa959c5d2da41424ef1f696304b5cd6.jpeg

Click to expand...

Pieyed47 said:

Jack, just gave you some good advice and this is what you need to do the job. https://i5.walmartimages.com/asr/4e...eba00_1.faa959c5d2da41424ef1f696304b5cd6.jpeg

Click to expand...

​

ryastu, if it were me, I would first find the bad battery, and if you have one bad battery I would reduce the 6-battery bank to a 4-battery battery bank and call it battery bank one. In place of the 2 6v batteries removed, install one 12v LiFePO4 Lithium Deep Cycle Battery with equivalent amp hours. Call it battery bank two. Install a Perco switch, if you don't already have one, to isolate one battery bank from the other. This will allow you to get more usable life out of the four good old 6v batteries. The good 6v one you removed can be a replacement for one of the batteries in the 4-bank group if one goes bad. I am going on 8 years on my 6-volt battery and I am quite sure they will get me through the winter. I am looking at lithium batteries as a replacement for what I have. HTH JD​

One last thing to check , but very important, is the connections at the batteries themselves and the buss bars. Poor crimps of the wire, poor terminal connections, or any poor, squiffy connections can introduce resistance that can ruin batteries interfering with recharges and power delivery to the boat.

THe actual battery clamp on terminals must be properly crimped to the wire and the clamps properly attached to the battery posts.

That means a good crimper, proper clamping bolts to battery posts, use of a dielectric grease on all connections or an electrical product which I have used for many years called NoAlox or Penetrox, both used in the electrical trades. All of these products will stop or substantially reduce any corrosion in the connections. You only need to cover the connections including wire crimps with a smear of the coating, not gobs of it. Keep good paper towels handy as they are messy and can stain where they are not welcome. On the smaller wires I often use a shortened applicator from a medical fuzzy wire , FORGOTTEN THE TERM, to apply the coating, both to the wire and internally to the terminal to be crimped.

--I use brass battery clamps
--I use bolts and nuts for the clamps, never wing nuts and leave the S.S. OFF as it is comparatively a poor conductor.

--I have used a hammer type crimper successfully to crimp the actual wire to the terminal clamps but they must be used properly. I used to carry a 10 or 15 lb steel plate and use that for the hammer crimper to rest on. A LARGE reasonably flat rock ashore can also be used. Set the hammer crimper on the supporting plate or rock and use a heavy hammer or sledge to hit the crimper. One or two blows should suffice. Wipe off the extruded excess anti corrosion coating, whichever you used.

--I also use heat shrink, glue lined, tubing of the appropriate colour , 3X shrinking and an inexpensive heat gun to shrink the tubing, after the terminals are fitted to the wire. Slip the tubing on the wire BEFORE you crimp the wire and clamp together as the tubing likely will not slide over the terminal once set. It may but check first.

A propane torch will likely burn the tubing before you can react and may damage the wire insulation so find, purchase or borrow an electric heat gun. I have an expensive heat gun I purchased when I use to work. I also have a Black and Decker heat gun which lives aboard the boat and I use that almost entirely for boat work. Just be carefull though as it is also high heat and can damage the heat shrink tubing if played on the tubing too aggressively. Slow shrinking is best.

I may have forgotten some of my procedure but this should cover almost all of it.

Others may have other procedures.

By the way, there is a very good crimper from FTZ. Often mentioned here by ???? lost most of my info and memory. A good crimper for a reasonable cost and if I did not already have a decent heavy crimper I would have one of the FTZs.

Offered by Bay Marine FTZ Correct Crimp Heavy Duty Lug Crimp Tool


Happy wiring.

Just to add. Buy a DC clamp on ammeter for your new bank. When they are recharging, measure the DC amps through each set. All should be about equal. Log the results so you can compare them later as a performance check. Variation can mean a poor connection or a problem cell.
Next take periodic SG readings. If you get significant variations then it’s time to do an equalization charge. Your inverter manual will tell you how to.