Understanding the Battery Label - Novice ??

[obiwan_canoli]

It appears I need to replace my 4-6V House Batteries. While the RV panel display shows Chassis Battery @ 12.6V, House Battery display shows 13.4. The Solar Controller display, also shows 13.6, and when I press the Amp/Volt button, it shows 5.6A (the status bar at top of screen shows 2 of 4 cells black - suggesting 50%). Pressing the Amp/Volt button on the controller one more time gives me a figure of 42.1A, with all status cells black, at the end of which it states 100%. Pressing one last time returns me to the Voltage indicator.

If I understand my battery bank resources correctly, good batteries at a full charge should show far more than 42.1A available. I surmise this because the label on the first of 4 batteries shows

"115 mins @ 75 Amps   225 Ah @ 20Hr"... (English, please). This suggests to me that with good batteries, I should have a bank of about 900Ah, more than adequate for several days without shore power.

I don't have the mind to wrap around this on my own, without input from someone much more knowledgeable than I, and patience as a teacher of battery wizardry... thanks for your help in turning the bulb over my head on...

Michael

[richard5933]

Couple of thoughts...

The amps being shown on the display are usually not the capacity of the batteries, but rather the amount of current going into or out of the batteries at that moment in time. My guess is that at the moment you pressed the button the first time it told you that 5.6 amps were going into your batteries. The next press of the button which showed 42.1 amps is likely a cumulative count of the amps either used or put back into the batteries. On my display, the number will go up while I'm discharging showing me how many Ah I've pulled from the battery bank, and as I charge the number goes back towards zero. Some count the other direction. As you run the charger make a note of which direction this number goes.

On my display, I've programmed in the total capacity of the battery bank, and the percent of charge is based on the actual number of amps which have flowed across the shunt measuring them. The percent of charge (SOC) which is showing 50% on your batteries could be based on the voltage or on the amps going into/out of the batteries. Likely yours is measuring the voltage, but checking the manual should confirm which it is.

Since you have four 6-volt batteries, you most likely have them connected in series/parallel configuration. That means that you have two pairs of two batteries. Each pair is in series to make a 12v battery, and the two pairs are in parallel to double the amps. (Series increases voltage, parallel increases Ah). This would mean that if you have the four batteries delivering 12 volts you have 450 Ah @ 20hrs, not 900.

If your chassis batteries are showing 12.6v and your house batteries are showing higher, then perhaps you are not charging your chassis batteries while plugged in. If they were being charged you would have seen a higher reading.

The difference between the two house battery readouts could easily being explained by either a margin of error (the displays are not all calibrated the same) or as a result of some minor voltage loss due to length of cables, size of cables, etc. Not something I'd worry about.

[wolfe10]

Assuming you are on shore power when you took those readings (or solar wired the same way).  If so, your coach, like many others only charges the house bank from shore power.  13.4 is  VDC is a good "float voltage" for your house bank.  Float voltage is what a smart charger or inverter/charger does to after the batteries are 90+% charged.  All is well.

12.6 on the chassis battery is very close to a fully charged battery bank, but not being charged.

Most accurate ways to check battery life status is either:

1. If wet cell, with a hydrometer.

2. Load test the batteries, but ONLY after fully charging them.  Most places that sell batteries will do this for free.