Battery Maintenance Question

[lfhoward]

Hi All,

I was working on my trailer today and ran out of power to run a jigsaw from my 1000 watt inverter unexpectedly quickly. Here are some stats:

3, marine deep cycle batteries wired in parallel, approx 240 amp hours when new (2/15).
Starting battery voltage today: 13.8
Cloudy day, only 2 amp charging from solar.
Outdoor temp: 45°

After charging a tool battery and running Bluetooth speakers for an hour, the battery voltage was down to 12.4-12.5. With the inverter on, it dropped to 11.9 and the automatic shutoff engaged when I tried to run the saw. I have run this saw many times before via this inverter so I know the system is designed and wired correctly.

Is this just a problem because of cold weather? Or are my batteries getting old and tired?

I have never before added distilled water to them so I wanted to check with someone who has. How does this look? At least I don’t see the plates so they appear to be submerged (a good thing).









Do they look low? If so, how much do I fill them with distilled water?

Thanks!!

[GTS225]

As long as each cell's plates are submerged, the battery should be ok, assuming nothing else is amiss.
If you have a decent vom, or dvom, you can check for a bad cell. Using your probes, start at a post, and measure from the post to the first cell, by dipping your probe into the electrolite, without touching the plates. Record the voltage, and move on to the next cell. Dip your probes into the electrolite, again without touching the plates, and record the voltage. Do that for the entire battery, and compare the readings from cell to cell. This will tell you if you have a bad cell, which draws the battery down prematurely.
You should get about 2.3 volts per cell. It can be low or high, depending on state of charge. More importantly, the readings should be consistent across the battery.

Almost forgot.....In your set of pics, second pic. Top cell is a bit low. Generally, those cells should be full to the bottom of that slotted tube. This allows for a bit of expansion, should the battery need it.

Oh, and NO SMOKING OR OTHER IGNITION SOURCES! Those lead acid batts give off hydrogen gas, and if one blows up, getting acid in your eyes is not something you will ever do again.

Roger

[MtnDon]

Do as above. For filling water get a dispenser like this. Fill it with distilled water, place the nozzle end in the cell, push down and hold against battery top. It stops dispensing water when the cell level is up to the proper point. Battery mfg have agreed on the plate to top distance.

[lfhoward]

Thanks to both of you for responding so quickly. I’ll get a battery filler bottle— I didn’t know about those and filling the batteries this way seems super easy. I had to look up what a dvom was, but it turns out I have one! A digital multimeter. I’ll check out the voltage of the individual cells once the batteries are recharged. Should I let them sit overnight with no load or charge so they equalize before I take my measurements?

In the event there is a bad cell somewhere (3 batteries x 6 cells = 18 possible culprits), what can be done? In a battery bank wired in parallel as mine is, the batteries should all be the same age, so that rules out buying just one replacement. But I know one bad cell or battery can drag down the performance of the whole battery bank, so maybe I go down to 2 batteries instead of 3?

I’ve been looking at sealed AGM and Gel batteries online and think this might be where I go eventually. They’re about $2 per amp hour which is about double the price of conventional flooded batteries, but they can last longer. Lithium is beginning to become available and they seem awesome because they’re light and can be drawn down lower than lead acid, but they’re $8 per amp hour. My charger and charge controller aren’t able to charge lithium cells, so I’m probably not going that route until prices come way way down.

[GTS225]

If you don't really need the additional amp hours, I'd just take out the bad battery, if you find one. It can always be replaced later.'
This idea of replacing an entire bank of batteries at once, instead of just one battery in a whole bank, seems terribly wasteful to me. I can not see someone with a solar cell bank and storage system replacing 20-30 batteries, just because they found one bad cell in one battery. That would be terribly expensive, and a rather negative impact on the idea of solar power use.
T'were me, replace the bad battery(s), and move on. Write the replacement date on it, so that you'll have a rudimentary record of how long they last.

I have an AGM in my '23 T-bucket, and it's been there for five years, and I don't treat it especially gently. Stays in the car, in an unheated garage for the winter, and fires things right up when it gets to be time to start driving it again, so I can recommend an AGM. I'm still not convinced that lithium, or lithium based poly batteries are the way to go either. Do remember, that that type of battery is what grounded a whole fleet of commercial airplanes due to high temperatures and smoking during flights. It's also responsible for numerous house fires from the advent of hoverboards and vaping devices. There's also been some isolated incidents of cell phones spontaneously combusting from their lithium batteries. I think I'll wait for a few more years before considering lithium.

Roger