Battery Problem

[Midnightsun]

Something odd happened to me last Friday. Was on the boat and I got a low battery warning @ 11.9V. Hmmm, I have been plugged into shore power for a good 5 days and assume my 2 year old charger is working fine. The 2 other battery banks for the engines are registering around 14V on a float charge which is pretty much normal. Went out fro a ride and nothing changed in voltage on the house bank so I assume that both alternators are not malfunctioning. Though I must have a defective isolater output going to the house bank since all juice needs to go through this to get to the battery. As luck would have it I had installed a 4 bank charger for use when on the dry for 120v only which is connected directly to each bank so I flipped off the main charger breaker and plugged in the 120v charger however the battery did not increase much at all after a good 14 hrs to only 12.3V. It has been charging since Friday evening and I just checked remotely, shows 12.98v but this is after almost 3 days of charging. It should be on a float charge by this time at around 13.5v++. Can only assume the battery has gone bad even if it is only 2 years old. Unfortunately this is dual L16 6v battery setup which is worth around $1000.

A little info. Dual 435AH 6V L16 batteries, secondary charger is only 10a per bank and seems to charge but at a ridiculously slow rate. This charger is hooked up directly to the battery so no acr or isolator to go through. Water levels on both batteries are fine and a visual inspection shows plates clean as a whistle.

Bottom line is the bank just seems like it does not want to take a charge at a normal pace.

Anyone have any advice/suggestions for me before I dish out a bunch of boat dollars and lug 125lb batteries around?

[bud37]

Test with a hydrometer to see what the acid density is........do you have the ability with any of those chargers to equalize......maybe worth a try to get the battery bubbling good......read up on it first as there are some precautions to follow. Myself I would remove them , take em home to play around, then if no good back to the store....heavy though heh.

Sometimes batteries just short out or die with no obvious reason. With only two years they would have some warranty I think.

The other thought , the charger is not recognizing the battery or is bad....past that I don't know, you will have to do some exploring, chargers, isolator etc.

[Viper]

A good tester will tell you if one of them has a bad cell. Disconnect and test. If they pass, you're on the hunt for anything from a poor connection to a bad charger output leg, isolator diode, a poor charge breaker on that output, etc.

[Midnightsun]

Unfortunately I do not have time to fiddle with the batteries at this stage. No house bank kinda screws up taking the boat out without having this issue in the back of my mind not to mention anchoring is a no go. Will purchase 2 new batteries and then bench test the old ones to see what the problem might be. Just checked it again remotely, went from 12.98 to 12.04 with a smaller 10a charger connected directly to the house bank. That voltage is indicative of a bank that is 70% discharged. For whatever reason it almost seems like catastrophic failure. I am leaning towards a bad cell bringing down the entire bank.

[pepmyster]

Hmmmm strange indeed. Need to test each one for sure. I have a great little tester which I use for work and during the summer I test the batteries at the boat. I know they are new, I would test them first. Then, start the hunt. It almost sounds like you have a load on them. Voltage of charge going up and down? I would hunt for something loading them.

[Midnightsun]

Good point pepmyster, will check it out.

[bud37]

Source of the post Just checked it again remotely, went from 12.98 to 12.04 with a smaller 10a charger connected directly to the house bank

That would be quite a load to pull down to 12.04 on a good battery, have you checked this with a good multimeter directly on the bank....What was your float voltage for that bank before ?

Edit....to add, a good battery monitor with a shunt would alert you to any parasitic loads that may not be obvious otherwise....

[km1125]

I'd compare the individual battery voltages. They should both be the same but if one is a bit below the other that would indicate something wrong with an individual cell.

With that charger and a significantly depleted battery bank, it would probably take 40 hours to get them fully charged, and that is with *no* other load on that circuit.

[Midnightsun]

Like I said, no time to fiddle with them at this stage of the game. If they are defective I will surly get some sort of compensation from the place I bought them from. Good news is I was able to get 2 Rolls batteries for an almost to good to be true price. Will pick them up today from a solar outfit about 20 mins from my home. For those not familiar with Rolls, they are considered la creme de la creme when it comes to batteries. Very well known and respected in the solar crowd. https://rollsbattery.com/battery/s6-l16-hc/

[Viper]

Have installed 4 of them so far this year. Great batteries for sure but like anything else, their longevity is only as good as how well they're maintained. If I remember correctly, they come with a 3 year warranty. Two of the units I replaced were only 2 years old so the customer is going through the warranty process.