Battery Charger DC amp jumps

[tankfarms]

Hello,
I have a Constant Power Mfg. brand battery charger for batteries in my MCC. Recently, I've observed that the charger's DC amp "jumps" every 4-5 seconds and then repeats. To be exact, the DC amp starts around 1 amp and gradually increases to 1.5 amps, and then suddenly jumps to 6 amps, and then comes back and start doing this again. At the same time, DC voltage stays at 135VDC without changing, however just a very tiny bit of the volt meter "jerk" can be seen as the DC amp jumps.
I have done a visual inspection on the battery bank and no abnormal conditions were found (i.e. liquid level, leaks, bubbles, cracks, etc.), so I'm not sure where to go for the next step troubleshoot. Below are some background info for the system I have.

Batteries:
flooded type, 20 batteries total, (3 cell each, with 2.25VDC nominal cell voltage). Total output voltage: 135VDC.

Charger:
Brand: Constant Power Mfg. (can't find any info on internet)
Input: 120VAC, 29amps
Output: 130VDC, 10amps

Any feedback/comments are welcome. Thanks

 

[zog]

I woudl check ICV's and do an impedence test on the batteries. Sounds like you may have some internal discharge going on, maybe cell reversal. When was your last equalizing chagre?

I assume you observed this with all of the loads disconnected?

 

[tankfarms]

I woudl check ICV's and do an impedence test on the batteries. Sounds like you may have some internal discharge going on, maybe cell reversal. When was your last equalizing chagre?

I assume you observed this with all of the loads disconnected?

you mean to check each cell voltage one by one?

not sure about the equalizing charge; I don't think we do it at all as this one has the equalizing dial set at 0.

I observed all of this with LOADS ON. I couldn't disconnect any loads as most of the loads are for motor controls (i.e. start/stop coils, relay power, etc.), and it's not possible to do so as I'm at a refinery.

 

[tankfarms]

Checked ICV this morning. There are a total of 60 cells. All readings are in the range of 2.25-2.30 volts, which are normal. Except on one cell, reading is a bit higher at 2.43 volt. not sure if it means anything.

Also checked the charger DC output voltage, it's at 136 volt and jumps to approx. 139~142 volt every 5~6 secs as the DC amp jumps from 1amp to 6 amps.

Now, not sure which caused which? DC amps jump causing volt to jump or DC volt jump causing the amp to jump? I'm now inclined to the later; if the case does that mean the charger might have some issues?

Thanks.

 

[SG-1]

Does the load on the batteries (output) increase when the charger amps increase ?

 

[LarryFine]

Also checked the charger DC output voltage, it's at 136 volt and jumps to approx. 139~142 volt every 5~6 secs as the DC amp jumps from 1amp to 6 amps.

That sounds like something designed into the charger.

If it were load-related, the voltage would drop during the current spikes.

 

[tankfarms]

Does the load on the batteries (output) increase when the charger amps increase ?

This increase is really a spike ( I should have said it properly). And there's really no telling, as most of the "loads" are starter/breaker control coils, powers to relays. Except for relays that need constant power, the coils are energized only when opening/closing starter/breaker, thus not pulling loads all the time.

 

[SG-1]

As ZOG has suggested, give the batteries an equalize charge.

Measure the battery output to the load. See if it is spiking.

 

[topgone]

What others have said, give the battery string an "equalizing charge" if you haven't done it since. The purpose is to give each cell "equal" charge as other cells are taking more than what they used to get.
E.g. you said your terminal voltage was 136 (for 60 cells). Dividing 136 by 60 will be 2.267 volts per cell (which is a good float voltage IMO). But you did say one cell measuring something like 2.43 volts! That proves that the cells are unevenly charged for the moment.

 

[zog]

You will want to do an impedence test (Mentioned this in post 2), that tells you the overall health of your battery.

Your battery will experiene sulfation after time, the build up of excess sulfates in the bottom of the jar and on the plates can cause small + to - shorts internal to your cells. An equalizing charge is a charge at a higher voltage and very high current (You can sometimes hear the cells boiling) which mixes the electrolyte and forces the excess sulfate back into the electrolyte. This should be done annually to ensure loing cell life.