Dead Batteries -- Blast Them or Coddle Them?

[Dockhead]

Originally Posted by hellosailor

"Just disconnect one battery and leave that a few hours to test the open circuit voltage."
The advice I've seen from multiple battery makers is that flooded lead batteries require a full 24 hours for the electrolyte to equalize out and the surface charge to dissipate. Not a few hours--but overnight to 24 hours.

As an alternative they also "all" make the same suggestion, put a load on the batteries for 3-5 minutes and that will pull off any surface charge. (Won't help the electrolyte equalize but will pull off the surface charge.) With a car they suggest putting the headlights on for a while. With a boat, you'd be looking for a similar load multiplied out times the # of batteries.
A few hours might very well work--but not to the same accuracy. Retest your batteries after a full 24 hours, and you should see the difference.

OK, thanks. I left them isolated for 10 hours yesterday. When I came back, they were showing 25.6 volts. I put a heavy inverter load on them -- a 2.5kW kettle, then a 1.5kW immersion heater. The kettle pulled the voltage down to just below 24 volts -- just like when the batteries were good. When the load came off, the voltage went back up to 25.3 or thereabouts -- a good number.

And I have not yet put on a full overnight charge nor equalized yet. It seems to me that the batteries are as good as they ever were. Kudos to Trojan! I was skeptical that the Trojans -- which are not heavier or larger and thus can't have more lead in them than the Vartas they replaced -- would be any big improvement. I seem to have been mistaken.

[Dockhead]

Originally Posted by Hud3

DH,

I think the real (read "practical") test will be when you have them fully charged, go for a cruise and then see how long they last. If they discharge noticeably faster under normal use patterns, you've got a problem. Good luck!

Thanks, Hud! I just lived with them for 24 hours without charging, and without having fully charged them to start with. They don't seem to be discharging faster than they used to. Got my fingers crossed. I'm going to sail down to Yarmouth this afternoon and hook up to shorepower, and give them a couple of hours of equalization in the morning. After that I guess we will see for sure.

[Fuss]

Originally Posted by Dockhead

The drain shown on the Victron was not 0.00. There was small current -- 0.1 or 0.2 amps, I think. Could have been the backlight in the Victron meter, and/or the water sensor in the bilge pump,

Hi Dockhead,
My victron meter switches the backlight off after a couple of minutes.... whether the backlight is on or off makes no difference to the displayed amp draw (0.00a) and before I had solar, I was able to leave my boat for a couple of months with no great loss of charge.

However!!!, I also have a xantrex monitor for 2 batteries with a dual shunt and this one takes a noticable amp draw and significatly shortens the life of one of the start batteries that it is connected to for its power supply. This means that over 2 months you can really see the difference between the 2 start batteries and this is due to the poor electronic design of the early model xantrex.

The victron does not have this fault.

Now that I have solar this problem is sort of solved.

Hope this helps

[sailinglegend]

Originally Posted by Dockhead

....I just had everything rewired by an expensive professional marine electrician to go to one master negative bus bar, so in theory, the Victron meter should be getting all of the loads. But in practice there are some exceptions -- the engine-driven alternator, for example, doesn't get its negative through the bus bar, and the Victron doesn't count amps added by the alternator. ......

Many battery monitors do not work accurately because the shunt needed to measure the current is often installed incorrectly. It must be as close to the battery as possibly – usually on the negative post – and a new bus bar must be installed immediately after the shunt. All other battery negative cables MUST go via this shunt. With multiple batteries in parallel, and not all in the same location, it is often difficult to know what wires are going where.

With a battery monitor installed the bus bar becomes the new battery post for the service bank, so the starter battery negative must also be connected to the bus bar not to a service battery negative terminal. This error is probably one of the major causes of battery monitors not reading the charging amps. This will often happen when the starter bank has priority and is charged first because the charger positive and negative cables will be connected to the starter battery. When the split charging system supplies positive volts to the service bank the charger will supply the negative arm via the starter battery post and then to a service battery negative stud. For the battery monitor to measure the service battery charge the starter battery negative must go through the new shunt.

[Cheechako]

So here's a question, Let's say you have a bank of 4 batteries and one of them is going bad. Does the Victron know? is it still counting amps hours actually stored accurately?

[Stu Jackson]

A battery going bad will reduce the amount of current it is able to accept. The monitor will simply show the current that has flowed into the bank.

The way to find a bad battery in a bank is to use a hydrometer.

[Dockhead]

Originally Posted by Stu Jackson

A battery going bad will reduce the amount of current it is able to accept. The monitor will simply show the current that has flowed into the bank.

The way to find a bad battery in a bank is to use a hydrometer.

Of course. Amp hours in and out is of very limited value. I go by voltage at low load (a proxy for open circuit voltage).

By the way, the batteries working very well indeed. They just supplied all needs on board for 23 hours without any charging, including anchor light, a lot of inverter use, electronics on 24/7, electric coffeemaker, and stayed above 50% according to voltage.

Kudos to Trojan -- clearly more resistant than my previous batteries.