Terry Ingram, 9114B battery replacement

[David E]

"A drop-in replacement is available from: TNR Technical, Inc. 1-800-346-0601 http://www.tnrtechnical.com/leadacid.html

PowerSonic PS-628 lead-acid battery. Cost: $12.00

I have purchased this battery recently, and it installs easily, and works fine.

Terry "

Terry, you mentioned you got this to work. I got the battery, and assume I have to wire the contacts, but how do you charge this battery?

Thanks

[Gene]

I popped the top cover of the battery off, which was made to be non-destructively taken off.

The battery has 2 slip contacts that go over the leads from the battery.

Slipped them off. Took out old battery.

Slipped them on new battery and replaced the top.

Took 5 minutes and worked like a charm!

Gene

[David E]

But how do you charge the battery?

[David Smith]

The original battery holder had a charging circuit built in that was powered by an 82059D wall wart.

[David E]

Also, I do not have old battery, I was battery less

[Gene]

Sorry then, if you don't have the battery housing, then I don't have any ideas. My misunderstanding.

Gene

[Glynn]

Actually, it shouldn't be too hard to work something out here. We apparently need to:

1. Provide charging circuit between AC wall power and battery.

2. Provide power for running the 9114b itself (but I think the battery does that, even if it is plugged in)

3. What else?

If ya wanna, for "authenticity", the 82059d transformer could be used... I forget exactly what that thing put out, but I think it was an AC output device (hmmm, was it 8VAC output?). So what you would be building is a charger circuit for this to run, one filtered by the battery. I am sure someone around here has the basic diagram and parts list for the 9114b's pack so all you have to do is duplicate that, if the parts are still available.

Otherwise:

Charging a lead-acid 6v battery is fairly easy to arrange. There are even off-the-shelf multi-step chargers which could do so, in the $25-$30 (US) range. The only thing to do then, assuming the 9114b itself is entirely run on the battery, is arrange for protection of the 9114b device from the charger's somewhat higher voltage (calling Captain Zener).

A "dumb", off-the-shelf solution would be finding a small rectified charger of 6-7.2v dc and <=120mA. You ought to be able to find this kind of small "brick" if you frequent thrift-stores and junque shops. It is less than an optimal solution: all it will do is TRICKLE charge, and not even to the battery's maximum capacity, but it would be gentle and do the job, if rather slowly.

A typical multi-step ("smart", hahahah) 6v lead-acid charger has a threshold switch, to give it two personalities. It would output up to maybe 7.8 volts at the peak, dropping to 7.2v or so to trickle-charge afterwards. It's current would not be limited while fast-charging-- the battery itself can handle this-- but in practice, you will likely find 1A or 2A maximums on the charger output itself. In trickle, the current would be limited at some arbitrary level such as 1/12 or 1/24th (safer) of the battery capacity. Once in trickle, you don't need to have the threshold switch kick back to fast-charge mode until your device has drawn down the battery with its load BELOW the battery's "nominal" voltage of 6v.

Has anyone investigated the alternatives for powering a 9114b in one of these ways?

[Ellis Easley]

I traced out the schematic of the charging circuit in my 9114 battery but I don't know just where that is right now. It has the LED that blinks to indicate the cycling that glynn is talking about. There is a full wave rectifier without a filter. There is a small filtered supply isolated by diodes to power a comparator and reference. The pass element is a sensitive gate SCR and its gate is controlled by a comparator circuit with hysteresis, the SCR is triggered with DC as long as the battery voltage is below an upper limit. The LED is in parallel with the SCR, and so when it is glowing the SCR is being kept off and the LED is providing the trickle current. At this current the battery voltage starts dropping until it reaches a lower limit and the SCR is triggered again.

I have been studying the charging circuit in the 3421A service manual just lately, it has a very similar battery, just a little larger - 3.2 A-H, 6V lead-acid. But it has a very different charging circuit. It starts with filtered DC, its pass element is a transistor, and it has two comparators: one controls the constant voltage with a thermistor in the voltage divider to give the voltage a negative temperature coefficient - it's about 7.12 V at room temperature, and the other comparator along with a current sense resistor limits the current to about 1/2 A, with the voltage folding back when the charger goes into current limit. Other differences: the unit has a larger transformer that the 82059D and the unit can run from A/C with a no-good battery (lead-acid batteries become open circuit when dead) - it draws about 0.2 A. The Panasonic lead-acid batteries have some detailed charging specs printed right on them:

"Constant Voltage Charge

Cycle use: 7.25~7.45V(25deg.C)

(Initial current: less than 1.28A)

[this is always 0.4 times the A-H capacity]

Standby use: 6.8~6.9V(25deg.C)"

The voltages specified vary slightly between older and newer Panasonic batteries.

The 3421A charging circuit seems to have chosen to go between the two voltage ranges. I have been using my 3421A to charge some 6V 10A-H batteries I found a few years ago. I mean to rig up a charger just for them and also some 12V 7.2 A-H batteries I found at the same time - someone had thrown them in the dumpster at a mini-storage facility, I think they were trying to avoid the recycling fee. I think they should come in handy - if I keep them from going bad! It has been nagging me that the batteries were going bad while I did nothing so I finally decided to get back on the project.

As they regain their function, the batteries behave thusly (I'm measuring the voltage across the current sense resistor and calculating the current): After letting them accumulate some charge, I remove the AC and turn on the unit and let them discharge for a while at 0.2A. When I turn the unit off and re-apply the AC, the charger goes into current limit for a while (~0.5A), the battery voltage being a little above 6V. After some time the charger comes out of current limit, at this point the battery voltage is ~7.1V and the current is just below 0.5A. The current continues to drop and appears to settle at about 0.05 - 0.1A, depending on the battery.

[Ellis Easley]

BTW, I asked the Ebay seller who had "hundreds" of ThinkJet batteries whether he had any 82033A's or 9114 batteries, he said no.

[Glynn]

To answer the question, how is this battery charged?

The 9114b and most all portable equipment with built-in batteries would rely on the input from a POWER ADAPTOR (ac adaptor, power supply, wall-wart, power brick, etc).

Hopefully you have one. If not, get one, otherwise replacing the battery alone will do no good. It is the AC adaptor that charges the battery whenever you plug it in. You needn't wait until you see a "battery low" indicator.

The battery itself is a lead-acid battery. It will come to you charged. It will need recharging soon AFTER your use of the device. The battery is a good one for powering such devices; it can sit on a charger for long periods without being harmed. It can supply lots of power. And, if it is NOT stored away while DISCHARGED, will last a long time (5 years is typical). Make sure it is fully charged before you put your device in the drawer.