We have been on a can in Boot Key Harbor for 10 days or so. Never in one spot for so long before.
My 6 golfcart house bank drops below 12 volts with little amp hour draw. I am using a honda 2000 generator to run the bank up till I am only putting in 10-15 amps at 13.7 or 13.8 volts. After charging, bank shows 12.2-12.3 volts. After 30 amphours voltage drops to 11.8-11.9. I think I have one bad cell, have removed that pair now have 4 glof carts. Same problem.
Is this OK? "They" say automotove batts are 12.6 fully charged. 12.0 discharged. I don't remember seeing "golf cart" numbers.
Sounds like you're not getting your batteries fully charged. 10-15A at 13.7 - 13.8 is still well in absorption range. The voltage should be higher.
1-What is the actual voltage at the battery bank + post when charging, not on the charger or the display but on the terminal? 13.7-13.8 is very low for absorption charging. Your voltage should be upwards of 14.6V. Trojan prefers 14.8V for absorption charging voltages.
Voltage is "pressure", increase the voltage and more current flows. You should get to less than 2% acceptance of "C" (C is capacity at the 20 hour Ah rating) with at least 14.4V at the battery terminal BEFORE you go into float mode. Ideally I like to see less than 1.5% acceptance before the charger enters float. On older sulfated banks this threshold changes and you may never get below 2% @ 14.4V this is why manufacturers & monitor folks often suggest 2%. Once in float mode the accepted charge current will drop in relation to the new float voltage. Simply bumping the voltage up and down at the same SOC changes how much current will flow into the battery.
For example I have a group 31 wet cell on my bench right now that is taking just 0.12A to maintain 13.4V. It is a 90 Ah battery so at 13.4V this battery is accepting less than one tenth of one percent of its capacity to maintain a float voltage of 13.4V. I have seen healthy batteries taking .04A to maintain float.
The industry number you see of 2% acceptance for "full" are often driven by the battery monitor folks. 2% acceptance is not technically 100% full for a healthy battery. Lifeline battery for example suggests that a full battery can be considered when the battery is taking .5% of "C" (20 hour Ah capacity) at 14.4V....
2- A fully charged wet cell battery with a resting voltage reading will be about 12.7 - 12.73 depending upon the manufacturer, not the 12.6V "they" suggest.. "They" have been stealing 10% of your banks capacity from you or about 70Ah, that you PAID FOR.... 70Ah is an entire group 24 battery you did not know you had........
Every .1V counts when it comes to battery SOC... Two six volt batteries are a 12V...
These are Trojan's values:
100% = 12.73
90% = 12.62
80% = 12.50
70% = 12.37
60% = 12.24
50% = 12.10
40% = 11.96
30% = 11.81
20% = 11.66
10% = 11.51
Note that the difference between 12.62 and 12.73 is 10% of the banks capacity!!! 12.6V is less than 90% SOC for most brands. Each tenth of a volt is roughly 10% of capacity.
3- What charger are you using? Is it programmable? It is likely going into float prematurely because your bank is beyond its recommended size range. Some chargers also lower the voltage, to be self protective, if they are getting to hot. Lowing the voltage reduces the current output and the charger runs cooler. Lower voltage means less accepted current to the battery.
4- To FULLY charge a 675 Ah bank of golf cart batteries will take 10+ hours and this is with a BIG charger. Your battery bank will accept about 165A of current in bulk (below 80% state of charge) and a Honda 2000 simply can't support a charger or chargers anywhere near that capacity. Once above 80% state of charge the accepted current diminishes and the "finishing" process is simply a matter of time and less about current. Also you have a charge efficiency to consider. You'll need to put back about 115 - 120% of what you took out to reach full....
There may be nothing wrong with your bank other than some some sulfation due to chronic under charging. They probably at least need to be equalized at this point after checking the specific gravity, then fully charging (to a real 100%) and topping up the electrolyte.
5- Be SURE your bank is wired to the loads and charge sources correctly. + and - should come off opposite ends of the bank your you will create an intra-bank imbalance which can lead to shorter life. This is one of the most often violated "bank non, no's" I see.
