What's Going On With These Batteries?

[SVRapture40]

You can't tell anything about the health of a battery when it is connected in a bank. And you certainly can't tell anything about the health of a battery when connected to an unknown load. Here is what I would suggest you do:


Completely disconnect all batteries.

Fully charge each separately.
Wait 12 hours and check voltage.
If you really want to go all the way, put a calibrated cycle load on each battery separately and calculate the capacity of each battery.


If you have a weak battery, it will draw the entire bank down. Either completely eliminate it from the bank or replace it.

[CapnCrunch]

Originally Posted by a64pilot

You may want to try to find out what your batteries charging voltages are, your voltages are almost dead on for Lifeline and they usually for whatever reason run low voltages.
The bank voltage drop when the fridge kicks on should be nearly nothing, not much at all. If it drops much it likely means a loose connection somewhere.

According to the multimeter, the bank only drops about 11 hundredths of a volt. I just wonder why the BMV shows a drop of more than a volt.

[CapnCrunch]

Originally Posted by SVRapture40

You can't tell anything about the health of a battery when it is connected in a bank. And you certainly can't tell anything about the health of a battery when connected to an unknown load. Here is what I would suggest you do:

If you have a weak battery, it will draw the entire bank down. Either completely eliminate it from the bank or replace it.

Thanx, but I think I've resolved the issue. I cleaned all terminals and connectors, shortened a few cables and rerouted the connections to make an actual "line" of batteries, then disconnected the loads charged them overnight and let them rest for 16hrs. Everybody read 12.99 +/- .02v when I reconnected the loads this afternoon.

[a64pilot]

Originally Posted by CapnCrunch

According to the multimeter, the bank only drops about 11 hundredths of a volt. I just wonder why the BMV shows a drop of more than a volt.

No idea, no real power goes thru the battery monitor so I don’t know, behind cleaning connections and if there is a inline fuse check that for cleanliness too.

[pcmm]

Originally Posted by CapnCrunch

Update, etc.:

I should maybe have specified that the voltage values I initially gave were taken as each battery was first disconnected from the bank and then, again, when all the batterys were reconnected. I checked them again this morning and all read around 12.84. It looks like maybe I just didnt give them time to equalize after re-connecting. (BTW: pcmm was right. The bank is connected to the panel at battery A However, I had turned everything off, so i dont know where any drain could have come from)

The next thing I dont understand is why my BMV 702 shows 11.9v when the bank reads 12.84 with the multimeter, unless the difference is caused by my fridge (which draws about 5.5A, according to the BMV).

I would check the voltage at the shunt with a multimeter see if you get the same reading. could be resistance in the connection. Are you sure that the BMV is connected to the correct OEM shunt?

[GrowleyMonster]

Originally Posted by CapnCrunch

Thanx, but I think I've resolved the issue. I cleaned all terminals and connectors, shortened a few cables and rerouted the connections to make an actual "line" of batteries, then disconnected the loads charged them overnight and let them rest for 16hrs. Everybody read 12.99 +/- .02v when I reconnected the loads this afternoon.

Nice going, Crunchie. I figured things would work out eventually, with the isolated voltages being so close together.

[john61ct]

Originally Posted by pcmm

Nothing to be embarassed about. The maker of walmarts batteries is the same one that makes West Marine;s Deep cycle batteries, and the Deka 6v golf cart batteries. All made by East Penn.

The voltages you are quoting are the charger float voltages not that battery rest voltages.

Evidence of that?

My understanding is Johnson Controls.

Only Deka I know of in any big box is Duracell 6V GCs.

Not saying be embarrassed, but a big box 12V pseudo deep cycle may well need replacing within the year if used for true deep cycling.

[john61ct]

Or batts near EOL

[pcmm]

Originally Posted by john61ct

Evidence of that?

My understanding is Johnson Controls.

Only Deka I know of in any big box is Duracell 6V GCs.

Not saying be embarrassed, but a big box 12V pseudo deep cycle may well need replacing within the year if used for true deep cycling.

East Penn def supplies Walmart (I used to work at East Penn and saw them get labelled) but I think for walmart supplier varies a bit by region.

East Penn also supplies West Marine their deep cycle batteries, same with Mercury marine and a couple of other RV brands that I remember.

[roland stockham]

If looking at any 'own label' batt I have always checked the weight. Basically working on the principal that the heavier a battery is the better it's deep cycle performance and durability will be. So if Walmart sells East Penn batteries under a different name check they weigh the same. If they do it is likely the cost difference may be in the supply chain - ie low payed staff, no special expertize, no backup, less warranty, less choice but lower price. If they are lighter it is likely they are a 'special order' for Walmart that is in fact a cheaper battery.

This applies to lots of stuff. Just buying some new pumps. Top brand verses cheap that is about half the cost. Rated capacity is the same but then look at current draw which is less and duty cycle which is 30min vs continuous. Conclusion the pump head may be very similar but it is a much smaller motor. So, if it is a backup for occasional and non-critical use, may be a good buy. For a heavy use critical location you are probably looking at replacing it frequently so not so good value.

[john61ct]

East Penn vs JCI is an indicator of build quality only.

Doesn't mean actually **designed for** deep cycling.

And does no good anyway if you can't tell who made it at the point of purchase, the "own label" customer can change specs or supplier anytime.

But with Deka's true deep cycle GCs available at $1 / AH @12V, and even Trojan's sometimes, there's no reason to buy 12V batts at big box anyway.

**If** your need is for deep cycling usage, for Starters fine.

[CapnCrunch]

Originally Posted by pcmm

I would check the voltage at the shunt with a multimeter see if you get the same reading. could be resistance in the connection. Are you sure that the BMV is connected to the correct OEM shunt?

Right on target again, dude! What started this whole quest was my fridge compressor would sometimes start up and quickly spool up to 9A (it should top out at 5.5A) then shut down and start up again so I suspected a low voltage issue. I shut the fridge off, connected my multimeter to the input side of the BMV shunt, turned the fridge back on and - lo and behold - 10.5V! Turns out that the connection between the neg cable from the bank and the shunt had corroded after only about 6 months. Now that that little gem is cleaned up, the fridge runs right AND the BMV only shows a minor drop in bank voltage when the compressor spools up.

Thanks for all your input guys!

[curtis742]

The best way to test batteries is with a quality hydrometer. Measure the specific gravity of each cell. The second best way is to perform a cell to cell test with a volt meter. I usually use a couple of three inch pieces of solid copper wire held by the alligator clips of the test leads. I just don't like dipping my test leads in acid and the wires can be rinsed with water afterwards and reused. Both methods will find any weak cells quickly. Don't touch the plates with the wires, just dip them in the electrolyte. The large turkey baster size hydrometer works the best but be sure to swirl the float in a circular motion to overcome surface tension and get consistent readings.

[philiosophy]

I have a somewhat related question on battery maintenance. I was once told monthly equalizing was hard on batteries. He said take them down twice a year and bring them all the way up. Can someone give me a clearer idea of how far down and how long a charge to bring them all the way up. I have rare access to marinas, Do have a Honda 2.0 Thanks in advance

[john61ct]

Bulldust. And going deep discharge should be avoided except when commissioning and capacity testing.

Regular unavoidable PSOC abuse increases the need for equalizing, even weekly may do more good than harm.

If you get to 100% Full every cycle then quarterly is fine.

Assuming your bank is a chemistry suitable for equalizing in the first place.