Battery drop

[sailorboy1]

Originally Posted by sailinglegend

None of these will guarantee to get you batteries to 100%. I have exactly the same setup but the only way I guarantee 100% full is overnight on shorepower.

Guess my system is better than yours.

My point is that maintaining your batteries as full as you can in order to make them last longer is not FREE

I'm not taking bait to get into a yet another "when is my battery charged" debate

[Peeew]

I went through a similar situation on my recent four month trip. Eventually I accepted the fact that with my overnight draw and limited daytime solar input I was just going to have to kill my 5x105 amp hour battery bank. I did not want to motor a lot and I did not want to run my generator for long hours to fully charge my bank. So I did what I could each morning and evening with my generator for an hour or so and let my 200 watts of solar help during the day. Sad to kill a new battery bank in one season but a lot cheaper than going into a slip once a week for shore power. I had a lot of daily draw with fridge, freezer, plotter, autopilot etc. So it worked out OK but will do some upgrades before my next long trip. More solar is first on my list.

[garychurch]

Had the same problem with year old wet cell batteries. They were shot. While they indicated that they charged fully they depleted to 11.6v overnight with a very modest amperage draw.

Replaced with AGM and added amp-hr meter with shunt and never go below 50% discharge. More than solved problem.

Good luck.

[JimZeigler]

There are a lot of good points here. You need to check each battery. Use a volt ohmmeter that you have cross checked with a fresh AA, C or D battery. Disconnect the batteries and measure the charge across the battery and if you have can, the charge across each cell. Assuming you are using 12V batteries, according to my references, 12.6 to 12.& 7 V is full charge for a disconnected a lead acid battery (2.1 V per cell - use a piece of wire to check the cell voltage and DO NOT drop the wire onto the top of the plates. Full charge on a gel is 12.85 to 12.95 V and on an AGM is 12.8 to 12.9 V. If you do not find an issue here, then place a ight load on each battery and check again. Then check the connections and especially the ground connection. Connect the ground to the battery and connect a wire to the 12V side. With VOM, check that you are getting 12V at all the ground points on you boat ( engine, electrical panel, keel, rigging, thru hulls. They connect the 12V side to the batteries and with the VOM connected across the batteries, turn on each circuit separately and look for the drain. When you hit it, the VOM will show it. Start with the main battery switch off - I actually had an issue one time with my electrical panel that occurred as soon as I turned on the main battery switch. Check for corrosion on the connections on the hot site. If you have an infrared interferometer (used to measure engine temperatures) scan the electrical panel and the engine room meticulously. Or if you have a friend in the local fire department, ask them to stop by with their thermal imaging camera and look for a hot spot. Finally, I assume no one is using the microwave oven off the invertor overnight. That draws a ridiculous amount of current. Good luck.

[Madehn]

I think i will start a race-- two posts one on battery charging and one on anchoring-- we can see which gets the most posts in a 12 hour period and which one has the first insult or indignant reply. seriously some good information here if i were in a philosophical mood about these two topics i would quote the sage "certainty is a delusion and repose is not the destiny of man" but given as how i am just a workin' stiff i think i will just go have a beer on my partially charged batteries and then see how far i have dragged.

[john61ct]

From bank care POV

2 hours genny run in the early AM before solar kicks in

can be worth 10x more than running later in the day

But running to carry heavy loads is different, can also help a lot.

Running 7 hours just to help the bank is not worth.

[dmkkeng]

Originally Posted by Khiimori

Hi everyone.
I am having an issue with battery voltage drop over night. I can have the batteries fully charged according to a Victron BMV-700 battery monitor and a voltage of 12.7V also displayed on a solar control monitor. With only a fridge, VHF and MFD on during the night at anchor the battery voltage drops to 11.8V between 9pm and 5am.
The Victron battery monitor says the ah discharge is around 50 to 60 ah.
I have 5 x 142Ah lead acid batteries as service and 1 as a start battery.
The batteries were new in 2 stages, August and October last year.
I had the batteries equalise charged and tested in a shop last month and was told they are in good condition.
Any ideas as to why and more importantly how to test for the cause?
I am new to the forum so apologise if I have posted in the wrong area or missed a previous post on the same subject.

To start with I'm not sure 12.7V equates to a fully charged battery. Also I would not trust the battery monitor - it may be giving you a false indication that you are at 100% SOC.
If the voltage is dropping to 11.8V you are likely at less than 50% capacity which on a continuous basis will reduce the life of the batteries. I would suggest that you look up the specifications of your batteries and perform a specific gravity test on each cell - this will ultimately tell you if all your cells are good and if you are fully charging the batteries.
Also I would invest in a good digital voltmeter and verify the battery voltage at the battery.