Friday, March 16, 2012

Re: [Electric Boats] Re: AGM Battery issue cont'd

 

Andrew:
 
Thanks for the reply. That's what I was thinking since I already have an XBM that measures the whole pack current and voltage wise. The Paktrakr was just a backup and allowed me to easily read the voltage of each battery in the bank inside the cabin conveniently.  But, if it is affecting the lower battery as I suspect it is I might install a power switch to disable it most of the time but, still allow me to do a quick voltage check of the individual battery voltages. It has a 1/4 amp fuse inline with it which is not blowing so the current is somewhere between the Paktrakrs nominal 25 ma and 250 ma. Have not measured it exactly yet but a drain is a drain. Though I would have thought with the chargers a current drain that low would not have been a problem. I did not want to use my Zivan 48 volt charger until I find out what was causing the suspect battery's failure to charge because I did not want to take a chance of damage  to the other batteries in the string. So I've only used the Dual Pro and another portable charger on the battery.  Charging was not a problem before until I added the data recording cable but, maybe it added that much of a draw that it confused the chargers. I've disconnected the Paktrkr for now and will see how the suspect battery looks on my next visit after being solar charged for a week or two.
 
Capt. Mike
 

From: Andrew Gilchrist <andrew@fastelectrics.com>
To: electricboats@yahoogroups.com
Sent: Thursday, March 15, 2012 8:36 PM
Subject: Re: [Electric Boats] Re: AGM Battery issue cont'd

 
Mike

Lead acid uses a constant voltage charge

This means that as the battery nears peak voltage the charger current falls to very low levels ie fractions of an amp

The charger reads the voltage of the entire pack and waits till the current reaches a very low level say .1 amps perhaps less. often for agiven period of time,  and then cuts off

If the other batteries in the pack a slightly overcharged - no real problem lead acid tolerates minor overcharging, the peak voltage has hit 55.2 and the current dropped to cutoff off point.

However if the Paktracker has current draw close to the chargers cutoff amps it will prevent the battery reaching full charge. It could have a leak through a slight short, or it may just drain the battery in the period between charges.

What you then see is a pattern in which the other batteries over charge slightly and the one never charges fully.

Switch to a device which meaures the performance of the entire string of 48v and the draw will be equalised for all battereis and charging should normalise.

Andrew
 


 On 3/16/2012 8:55 AM, Mike wrote:
 
I got some good news as I continue to investigate the status of the most negative AGM battery in my boats 48 volt string. Previously it had passed the Centech battery anyalyzer test and a load test but, was not able to be fully charged by the Dual Pro charger or an external charger that I had connected to it. Since this is the battery that the Paktrakr takes it's 12 volt operating voltage from I suspect this parasitic load (along with the additional data recorder cable I added recently) was causing some problems over the winter layup. So I disconnected the Paktrakr load and let solar panels via the Morningstar Controller charge the bank. The Morningstar does provide some type of equalization in it's charging algorithem. So two weeks later I go back on the boat and plug in the Dual Pro charger:
 and lo and behold three minutes after pluging in the charger the suspect battery is up with the other three batteries according to the Dual Pro display. It also reached a fully charged condition a few minutes after the other three in the bank finished charging. The final voltage is still lower than the other batteries in the string but, things seem to be moving in positive direction.   It's been very puzzling trying to figure out what is going on. It passes a load test and the battery analyzer test which shows a low 2.3 milli ohm internal resistance. Yet two battery chargers intially said it could not be fully charged. But, now it can and is not lagging to far behind the other three batteries in doing that. I'm keeping the Paktrakr disconnected and hoping to see further improvements in this battery with the parasitic load removed during my next visit. Any thoughts on what's happening with this battery?
 
Capt. Mike
 
 
From: Mike <biankablog@verizon.net>
To: ELECTRIC BOATS <electricboats@yahoogroups.com>
Sent: Monday, February 20, 2012 9:21 AM
Subject: Battery issue cont'd

I took Arby's suggestion and bought a battery analyzer from Harbor freight. You can see some of the preliminary test results and also how my Dual Pro Quad battery monitor is working here:
 
Previous links are here:
 
The analyzer shows lower capacity in the suspect battery (most negative in the string) but, still not totally dead. Though the Dual Pro charger timed out in trying to charge it. I still wonder if adding the Paktrakr data recorder cable had done something or if it's just coincidence.  I would have suspected it added just minimal load to the basic draw (25ma) of the Paktrakr. Still this problem did not appear until I connected the recording data cable onto the Paktrakr. I've disconnected the Paktrakr for now. Next time I'm on board I plan to disconnect the batteries let them rest for 24 hours and then do a load test.  Comments or suggestions?




--  AJ Gilchrist Fastelectrics 0419 429 201


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