House Battery Bank Questions

[junaido]

I have a house bank of 4 Trojan Mileage Master 6V batteries of unknown age.  I think there is a Xantrex battery charger. Recently I noticed the cabin lights get dim after 3-4 hours of use when boat had no shore power. The Link 20 battery monitor shows green lights but when I check voltage it's about 10V. After leaving the charger on for a few days, I turned it off, turned everything off that could draw current (Link 20 still showed 0.1A current for some reason), after a day the fully charged house bank was down to 9.9 V with nothing on. When I put a multimeter on the 4 batteries, two of them show 5.5 V and two show 4.5 and 4V respectively. Is there any way of milking some more life out of these batteries by getting rid of the weaker two batteries? In case I need to replace, the Interstate Golf Cart batteries at Costco are about $100 whereas the Trojan batteries run about $300 at the local battery store. Both have roughly the same amp hours, 210 vs 225 AH. Are the Trojans really 3 times better? Any other 6V battery recommendations? Thanks.

[KWKloeber]

Possibly some helpful info you can use:

https://groups.io/g/Catalina30/message/108544

Rod Collins really likes USBatteries - calls em the Trojan Killers.

You might want to load test the batteries.  Is there no date code on them or serial no.?

[waughoo]

I would say that if your cabin lights brings 4 Trojen batteries down to 10v after only 3 or r hours of use, them batteries are cooked.  As a last ditch hail Mary, you could check the electrolyte in all the batteries.  It is possible that all the water has been cooked out of them.  Pull the caps and add distilled water to bring them up to the proper level.

After you've checked that, do a load test and start shopping for batteries.

[pablosgirl]

I would not mix old batteries with new ones.  I run 4 GC2's from Advance Auto Parts. They go for ~$100 each on sale. I have 6 years of heavy use on them and they are still going.  I do check the water level at least once a month.  Letting the water fall below the top of the plates damages them and reduces capacity.

[Stu Jackson]

The 0.1A draw on the Link 20 could well be the parasitic load of the Link unit itself.  Yes, when have you checked the water levels?  Have you used a hydrometer on the cells?  It does sound like your bank is toast, because of the voltage sag and no results when charging.  In addition to water levels, have you checked to see if any batteries have their cases bulged?  Please do not continue to charge this bank unattended because it sounds like a potential for a catastrophic event: charging dead batteries that could have internal faults is a possible route to a literal blow up.  Individual choices in new batteries can vary all over the place, but in the end the choice is usually over cost and quality, you can't get low cost with high quality.  Maine Sail's experience is priceless.  Lots also depends on how you intend to use your boat:  i.e., weekend warrior vs. long term cruiser/anchor out for long periods. 

[junaido]

I should have mentioned, batteries had been topped off with distilled water before all these readings. No bulges in batteries but I think the time has come to replace. I have yet to spend a night at anchor so I think I will probably go with the cheaper option. When I turn on the charger it shows 8 or 9 amps going into the battery bank. This continues to drop off steadily to about 1A after several hours.

[Roc]

If your battery charger can go into the equalization process, you should try to do that.  I just bought (4) Duracell golf cart batteries at Sam's Club to replace the "Energizer" ones I bought there back in 2009.  The one's I just bought are EGC2 replacing the GC2 from 2009.  $135 each.   20 amp hour rate 230. 

[KeelsonGraham]

Letting the water fall below the top of the plates damages them and reduces capacity.

This got me thinking. What happens to wet cell batteries if you're on the same tack for a couple of days? Unless you go against the normal advice surely a good part of the plates will be uncovered when the boat is heeling??

[KeelsonGraham]

I should have mentioned, batteries had been topped off with distilled water before all these readings. No bulges in batteries but I think the time has come to replace. I have yet to spend a night at anchor so I think I will probably go with the cheaper option. When I turn on the charger it shows 8 or 9 amps going into the battery bank. This continues to drop off steadily to about 1A after several hours.

I have the same problem. Last weekend, after a 9 hour charge, my four T105s were down to 50% after 4ah of draw. I did a hydrometer test on two of the batteries which revealed some totally discharged cells in both of them. I didn't bother checking the other two. They all have to be replaced.

[Steve McGill]

Assuming you have the space in your battery location the proper orientation for the battery cells are to have them running port to starboard, not bow to stern. This will help minimize the plates being uncovered.

Good luck,

Steve