The manual says that the PS100 is temperature compensated, meaning that the float charge voltage should decrease with battery temperature. Just now, I measured a voltage of 12.8 at room temperature on a fully charged and charging battery. This seems rather low.
Is there a published chart of charging voltage vs. temperature?
Is this a float charger only or does it have a multi-stage charging logic?
The PS100 is designed to follow the Yuasa recommended temperature curve for float charging batteries. This would give a nominal charge voltage of about 13.7 V at 25 deg C. The design should follow the curve to within +/- 0.2 deg C or better.
If you are reading 12.8V aT 25C (at the battery - the logger will read low due to protective diodes) is the side of the charger hot? If so the sensing thermistor which is inside the charger gets hot too and pulls down the charge voltage to match the temperature it senses. If it is hot the battery could be not charged yet or faulty (a bad cell perhaps) and is not reaching full charge. If it is not hot then the PS100 may be faulty or may not have been setup correctly. There is an adjustement potentiometer inside which is set during production which you could adjust (at your own risk) or return it to be checked.
The PS100 is a float only charger. We also now offer a more advanced (and more expensive) charger the PS200 which has just been released. This is multistage and can charge at higher rates. It also can be interogated by the datalogger to check its state.
Thank you, Andrew.
At this point the battery is definitely fully charged, and the battery terminal voltage is 13.2V. The battery temperature is 22C, and the outside of the charger is about 32C.
Can you give me a few more points on the temperature vs charge voltage for your design?
I am afraid I do no have access to the test data at the moment as it is a holiday period here. What the circuit tries to do is to match the Yuasa float/standby curve. This can be seen by clicking on the Charging Voltage/Temperature curve link on this page:
http://www.yuasaeurope.com/en-gb/industrial/products/np/
The temperature sensor for the PS100 is inside that case so it will be seeing 32C or a little higher. This puts your measured voltage just under the expected curve or on it if the internal temperature is warmer.
The PS100 is a series regulator so will dissipate more heat the higher the charge voltage. What voltage supply are you feeding into the regulator as I am surprised it is so hot. Is there some extra load across the output of the supply? Perhaps you could try to measure the current going into the battery and out to the logging system when it is charged to get the whole picture.
The placement of the temperature sensor does appear to undermine the temperature compensation. After discharging the battery about 50%, and then switching to charge mode the logger voltage briefly spiked to 12.9 before settling at 12.65. When the battery approaches 100% charge the charger remains warm because of a constant load in the range of 150-200mA, and this keeps the logger voltage down near 12.8. The AC supply is a 9591.
It seems that this is all working the way one would expect, given the design of the PS100.
This is a limitation of the PS100 (and many similar chargers) I am afraid especially when there is significant load on the battery. However, if the charger does warm up the over-reading of battery temperature is on the "safe-side" in terms of risk of damage to the battery.
The PS200 has a similar on-board sensor but is more efficient so does not dissipate so much heat with a similar load. It also has a feature where you can send a independent measurement of battery temperature to the charger rather than using its on board temperature sensor. Unfortunately it does cost more.
Thanks for the information on this, this has helped greatly.
* Last updated by: dano1987 on 12/7/2011 @ 8:08 AM *