Battery one woe: We keep two banks of batteries on-board s/v Hajime. During the last voyage up coast, we switched over to the starter batteries to start the boat motor and left the switch there for a couple days. The starter bank is two group 27, 90 Ah, lead acid batteries from Sam’s in the US dated 2/1012. We ran the bank down to near 11.0 volts over night and the next day. Since the only charger for that bank is an echo charge which only operates when the house bank is charged over 13 volts. So the bank got NO charge for a couple days and all the usage from the boat and we drew it down to near the 10.5 volt empty.
When we saw the low voltage, we switched back to the house and all was well… Or was it? The only charge, again, is the echo charger and if the house was just keeping up the starter bank was not getting charged. The next time we ran the motor for around 6 hours, we set the batteries to ALL so both banks would charge on the 120 Amp motor alternator. The starter batteries still did not charge. When we made it into dock and turned on the shore power on-board battery charger it kept shutting off and the starter bank still did not want to charge up…
Finally opened the battery compartment for the starter batteries and felt the heat. One of the starter batteries was so hot you could not touch it. We disconnected it quick as we could and set it out on the dock. It did eventually cool down.
Diagnosis? SHORT in a battery… The other 12v starter battery which was in parallel with that one did finally come back to charged voltage and is holding a charge and the charger is acting properly again… So we are back to a single starter battery and that’s OK. We are 50 pounds lighter.
Battery two woe: When we bought s/v Hajime in 2010 we remodeled the area under the binnacle, removing the water heater tank so we had some room for a instant on water propane water heater and for the new house bank battery box.
In this box, with inside dimensions of 24.5″ x 14.5″ x 12″, we put 4 each GC2 6 volt batteries. When wired serial then parallel, we had a house bank of 440 Ah at 12 volts. We replaced the batteries in 2012 before leaving for Mexico, after living on-board for 2 years, and it is time to think about replacing them again.
We have plenty of solar to get them charged up daily, but given a cloudy day or two and normal loads we tend to have to run the motor to charge. When new they took a charge better and seemed to have more capacity.
Overnight usage is probably:
Nominal aux and nightlights 1.5 amp for 10 hours = 15 Ah
Refrigerator 7 amp for 8 hours max = 48 Ah
Total max overnight = 63 Ah, this should not take the battery bank from 12.8 volts down to 12.2 volts overnight…
If 12.2 volts is 60% battery capacity then we should have used 40% of 440 Ah or 176 Ah overnight… Maybe the system is inefficient to the tune of (63-176)/176 = -65%.
I know lots of things happen to lead acid batteries depending on rate of discharge, temperature, and number of discharge cycles:
But…. Starting to think (and have read, some where?) that a house bank is GOOD for a couple to three years so we are right in there for our third set of batteries since 2010… Today is Jan 09, 2016
Now the fun and techie bits… We are in Puerto Vallarta. We ran over to Zaragoza Marine Chandlers from the Marina Vallarta docks where we are keeping the boat and looked at AGM marine batteries. Looks like, for us to get similar to our existing 440 AH house bank we are looking at around $1800 USD for AGM lead acid batteries. And maybe reworking the battery box. Can’t find AGM GC2 batteries around here (haven’t looked real hard).
For a while we were thinking that AGM (absorbed glass mat) seems the way to go because they don’t out gas during charging and need no distilled water for maintenance. They are spec’d to be a little more efficient and maybe last a little longer than lead acid. AGM are more expensive than the USA Sam’s club GC2 flooded lead acid batteries we have been using. Sam’s ran about $300 for a set of 4 lead acid batteries. I think in the US we would see about $1000 for 4 each GC2 – AGM batteries.
Battery WOW: Now, we are excited for the lithium iron phosphate batteries we just ordered and our BEST friends are bringing down to Guaymas for us! We will bus up there and bring them back the end of January…
LiFePo4 batteries are way cool, they have almost no energy loss during charging and don’t drop in voltage during use. You can use close to 80% of the battery Ah capacity when compared to the 30% usable in a flooded lead acid battery. Meaning you should be able to replace a 400 Ah lead acid battery set with a 200Ah Lithium iron phosphate set… ( We decided to double our house bank capacity by keeping the house at 400 Ah in LiFePo4 batteries.) They also have maybe 10 times the discharge cycles in them, so they are even (maybe) cost effective when compared to the Sam’s batteries? I understand the Ah capacity of LiFePo4 reduces with the increase in discharge cycles. Maybe up to 25 % over the life of the batteries.
We ordered 4 each of the 100Ah LiFePo4 “Lithium Iron Phosphate” batteries with on-board battery management system , similar to the blue one pictured below. The open battery shows the BMS circuitry loaded into the case:
These are a drop-in replacement for a lead acid or AGM battery, and the BMS takes care of cell balancing, over charge protection, short protection, under voltage protection, and provides for data output to a computer as needed… Specs on the 100Ah LiFePo4 lithium batteries we have ordered…
These batteries run $875 each