JRDG Coherence II; Battery Display Issue

We had a power outage here in New York that lasted 3 days. I shut down the system, but didn't think to power down the CII. It is operating fine, but neither the LOW or FULL light is illuminated for the battery. The power came back on Tuesday at about midnight, so its been receiving AC for nearly 40+ hours. Does this mean the battery is no longer holding a full charge? Will it affect performance? Frankly, I didn't notice whether the light was illuminated before the power outage

Three additional details. When I power down the PS, it automatically powers up within about 5 seconds. Also, the FULL lamp comes on for a second then goes off. This at least tells me the lamp is functioning. Lastly, when I switch from AC to Battery, there is no discernible fall off in performance. Basically, everything seems to be working, but the LOW/FULL lamps are dark.
I'm betting that your batteries cannot hold a full charge now. If you haven't replaced the batteries in over 5-7 years, it might be time. If you go in battery mode how long do the batteries last before switching to AC? I think you might find its a shorter period of time than you were used to.

When I had my batteries replaced, JRDG did it quickly if I remember the cost was around $120 with shipping.
Would you happen to know if it is ever normal for both FULL and LOW lamps to be dark? Is the performance of the unit compromised in this state? How would one normally determine when it is time to replace the battery? What did you notice?Thanks for the response.
Stew, if you determine that your batteries last significantly less than prior to the blackout, you may want to cycle the charge completely several times. The operation may restore some of their original charge capacity. If you require new batteries, call JRDG at (719) 473-1181,, extension 4. G.
Would you happen to know if it is ever normal for both FULL and LOW lamps to be dark? Is the performance of the unit compromised in this state? How would one normally determine when it is time to replace the battery? What did you notice?Thanks for the response.
I noticed exactly what you described and then when testing battery life it was significantly shorter. On my BPS1 I can get around 6-8 hours a continuous battery play. When the batteries were near the end of thir life, I could only get an hour or less.

Guido is right though - might be worth trying to cycle them.
Stew, as mentioned in my PM, there is an entry in the JRDG knowledge base that suggests that one of your batteries may have failed and may need replacement. See:


The Coherence II manual at


discusses battery operations in the following paragraphs:

A MODE SELECT push button: Momentarily pressing this button switches
the power supply between AC and BATT operational modes. Either the
BATT lamp or the AC lamp will be illuminated. Note: BATT mode is not
allowed unless the batteries have achieved sufficient charge capacity.


Upon initially connecting AC power, it may be necessary to press and hold
down the MODE button (2) for five (5) seconds to initially boot-up or
reset the charge management system located within the Power Supply. In
a few seconds, the AC mode lamp will light and the Preamplifier INPUT 1
And RECORD 1 lamps will illuminate.
The Coherence Preamplifier is designed to be powered from the AC mains
which automatically initiates battery charging as necessary and is indicated
by the illumination of the AC mode lamp. However, the Preamplifier is still
powered by the internal batteries. AC mains power is disconnected from
the power supply internally whenever the BATT mode is selected using
the MODE push button. Under this operating condition, the preamplifier
operates exclusively from the internal batteries. Up to fifteen (15) hours of
operation in this mode is possible depending upon the initial state of
charge of the internal batteries.
If the Preamplifier is not used for an extended period of time and/or a
source of AC power will not be available, AC power should be removed
and the MODE push button should be pressed and held down for
approximately five seconds. A slight click will be heard. No lamps should
be illuminated. This feature allows the preamplifier to be stored or
shipped without discharging the internal batteries.

If the FULL charge lamp is illuminated, the battery capacity will range
between 50-100% of full charge. This lamp will not illuminate shortly after
the BATT mode is selected.
If the LOW charge lamp is illuminated, the battery is significantly
discharged and will automatically switch back to AC mode to commence
charging. If AC mains power is not available under these conditions, then
the Power Supply will automatically switch off, thus preventing the
batteries from becoming overly discharged.
The Power Supply is intended to operate connected to active AC mains at
all times. The charge management system only permits operation at the
voltage indicated on the rear panel. If an incorrect AC line voltage is used,
all of the Power Supply front panel lamps will flash on and off simultaneously
approximately four times per second.


Battery Complement 2 each 12 volt, 7.2 amp/hour
user replaceable sealed, lead calcium,
maintenance-free batteries
Battery Service Life 5-8 years
AC Unassisted Run Time 14-18 hours based upon
initial battery full charge

There are 2 JRDG-authorized repair shops in New York State. They are both listed on the JRDG Knowledge base at:

Looks like battery is shot. I switched mode over to battery and it autromatically cycled back inside of 2 hours. As much as I dread it, I will have to bite the bullet and swap out the batteries for new ones. I was told to remove the unit completely from all power sources and let it sit for a couple of hours, if not overnight. This will let the circuit reset.
Uck.... Looks like the 3 days long battery drain zeroed the battery and possibly inverted their polarity as well. Remember to apply a touch of vaseline or similar lubricant onto the walls of the battery compartment, to prevent the fresh set from ever getting stuck inside. There is a specific JRDG bulletin, which states....

"placement Battery Installation

The replacement batteries for the Coherence and Coherence II preamplifiers are chosen specifically to fit into the holes cut into the preamplifier power supply chassis.

To install the batteries, please observe the following precautions:

• Unplug the power supply from the AC outlet.
• Disconnect the preamplifier from the power supply.
• Using a cloth or paper towel, rub a light coating of Vaseline or petroleum jelly on the inner walls of the battery pockets of the power supply chassis. This will prevent the batteries from becoming stuck in the future if there is any sort of swelling or shape increase. Note: Do not place the petroleum jelly directly on the battery, as it may cause you to lose control of the battery and drop it during installation."
Stew, the batteries aren't bad to replace. I sent mine in to JRDG, but thinking about it, they could probably just ship you the batteries and you could do it yourself.

I've used their email message service from their website and rarely get a response back, even after 2-3 weeks. When I call them they are usually very responsive. I just thought it was more 'polite' to email, but calling them gets you a response quicker.
Do lead acid / Gel / glass matt batteries invert? I know my NiMh batteries can and do. The battery pack for my camera is 10 AA cells in series so if I have a weak cell, I'm a goner.
I'm working on a replacement / fix / rebuildable now since Canon gets 100$ and the aftermarket stuff sometimes is of suspect fit.
Magfan, the JRDG literature is not terribly specific. It states only that excessive drain may damage the Lead-Calcium batteries of Coherence. Actual polarity inversion is a pure fruit of my own guesswork. Needless to say, the application of a non manufacturer-supplied battery cell to an electronic device like Coherence II is a recepy for expensive, and sometimes fumiginously stinky fireworks. G.
Replacement of the batteries has solved the problem. Battery charge now reads FULL. I guess the lesson is that when the battery no longer reads FULL, it is time to replace. Perhaps I will try to listen strictly off the battery, but previous experiments yielded no audible benefit. Thanks to all who posted in response.
I also wanted to add for the benefit of other Coherence II owners that the sound is indeed improved with fresh batteries. I don't know if there is a scientific explanation or if it is even counter-intuitive, but I know what I am hearing. Bass is more punchy and entire presentation is fuller and more robust. Just a lesson for the uninitiated. Do not try to squeeze every last ounce of life out of the batteries. I will now be more sensitive to whether the FULL lamp is illuminated. I will also again keep a spare pair of batteries around after about the 4th year.
Stew, it is likely that your depleted batteries did not deliver an optimum voltage to Coherence any longer.... Hence a comparatively more dynamic performance with fresh batteries. G.
All, if anyone needs replacement screw fasteners for Coherence top and back plates, the correct type is:


Please note that these are not common 4-40 screws, and they may not be stocked by all consumer-grade hardware outlets. G.
We'll put a few in the mail to the address below.