battery overcharging

[garethreeves]

Hi All,

Forgive my ignorance on this subject. I have read through other posts but I am still kinda lost.

2 days ago we noticed the dreaded egg smell. I wasn't sure what it was so left the boat as is. Read about overcharging and went back to get to shut the charger off. I also took some readings.

Battery 1:
Hot to the touch and making a slight hissing noise. 11.5 ish volts with charger on and off. Drops down to 9.5 ish volts when battery selector switched to 1 and a few lights and the stereo on (and charger off).

Battery 2:
Cool to the touch, reads 12.5 volts with charger off, 12.8 with it on. Drops to 12.4 with lights on switch on battery 2 and charger off.

I leave the charger switch on when on shore power. I thought the best thing for them was to keep them topped up. I spoke to the previous owner and he said that he would 'charge them when needed'. Is it wrong to leave it on? Does bat 1 need replacing?

One more question. I left the AC on, but turned the charger off. I was hoping the refrigerator would still get power. Is that just wrong? So without the battery charger on but the fridge on, can I expect to drain the batteries?

These questions seem embarrassingly simple now that I write them down...

Thanks in advance for any help.

Oh some more details might be useful. My boat is a 2000 hunter 320. I've owned it since April (and love it). I am not exactly sure about the brand or type of the batteries. I am pretty sure that the charger (C-Charger 2000) is stock as is everything else.

Gareth

 

[Don S/V ILLusion]

Battery #1 is toast and you could damage the charger or worse if you continue to charge it.
The other battery isn't far behind given the resting voltage you stated.

You really should determine whether your refrigeration is AC or Dc powered. You'll need to know that to properly size your replacement batteries. Should be simple to figure out if it runs when no AC power is available.

 

[navigator97]

Is your charger just a "bulk" charger (single stage)? Or, is it a 3 stage charger with a bulk charge (stage 1) , topping off charge (stage 2) , and Float charge (stage 3)?

 

[garethreeves]

Thanks Don. Did I do this by leaving the charger on?

Navigator97 - I think its one like this. Its described as 'multi step' - http://www.charlesindustries.com/main/ma_batchcch_ad4.html

I can check that actual model number tomorrow or thursday.

 

[Benny17441]

The refrigerator for the h320 is dc powered so by the time you get back to the boat battery #2 should be flat. Like Don says Batt #1 seems to be dead and batt#2 is following in the wake. You raise a good question about wether to keep the charger on 24/7 or not and the answer is that by keeping it on you are likely harming the batteries but the alternative is to follow a schedule to turn the charger on and off and prevent the batteries from getting partially discharged which could lead to worst harm for them. I personally take the convenience approach and keep the charger on at all times which will be necessary if you are running the refrigerator. My suggestion is to get a couple of new deep cycle batteries and start anew.

 

[Maine Sail]

You have one battery that is dead, probably an internal short.

Some questions:

1- When was the last time you added distilled water?

2- Have you ever checked the specific gravity of the batteries?

3- How old are the batteries?

4- Have you checked the temp of your battery compartment?



With a "proper" charger there should be no problem leaving the charge in the "ON" position. However just because a charger calls itself "smart" does not mean it is actually "smart". The one cavaet to this is that dock power is HORRIBLY dirty, fluctuates, spikes and has a nasty habit of destroying battery chargers. In a perfect world these chargers would last decades but when connected to dock power they often fry sooner than the warranty runs out or slightly after it does. The newer "World Voltage" chargers tolerate poor dock power significantly better than US voltage only units.

My one simple rule is this; If the charger does not have a battery mounted temperature sensor, it is NOT a "smart" charger no matter how much the glossy ad tries to convince you that it is..

No temp sensing of the bank, don't purchase that charger unless it is only to be used for a day or two at a time to "recharge" and not "maintain" banks. This is a plain & simple rule for buying a new charger and an easy way to determine a true "smart" charger vs. a dumb charger. Of course if you don't mind buying new batteries sooner rather than later you can save a few bucks on a "dumb" battery charger vs. a true smart one.

Battery temp is a very critical component of battery charging especially when the charger is going to be left on for days/weeks at a time. I have a couple of customers boats who's battery compartments can exceed 120F during sun up hours due to hull color or location of the vessel at the dock and the way the sun hits the hull. These batteries never last long despite a charger or solar/wind system with temp compensation. If this happens to your batteries and you are at a dock consider flipping the boat around at your slip... Other than owner abuse heat is perhaps the #1 enemy of batteries..

Any time a battery goes over 80F the voltage should be adjusted to compensate for the temp increase. Getting a battery over 80F in summer temps is not a difficult task.. A battery designed to be charged at 14.6V at 77F should not be charged at 14.6V at 90F or 100F... Conversely a battery at 32F should be charged at a higher voltage to compensate for temperature drop. A "smart" charger will adjust the voltage based on the battery banks temperature.

Charles does make some very good chargers I have just not been impressed with their lower priced entry level line...

Your current charger may be fine, operationally, and new batteries may be all you need but you still have a non temp compensated charger and leaving it in 24/7 is not necessarily the best idea for bank longevity. You'll probably want to check electrolyte levels every 4 weeks or so with that charger.

 

[garethreeves]

Thanks for the lengthy response maine sail. I'm afraid that the answer to all of your questions is no, or I dont know. I will get on it.

Another data point that I didnt think of until last night is the following.

The fridge accidentally got turned all the way down and a soda can exploded, opening the hatch. It could have been as much as a few days that the fridge was running full blast and wide open. It was still cold the next time I got to the boat but I dont know how long it had been that way. This was just a couple of days before we noticed the bad smell from the battery.

Could the power output and charging required for this have toasted the battery?

Thanks