Automotive electronics - Honda charging system

Charging systems typically increase the charge voltage at lower temperature s. Does anyone know if the increased voltage fully compensates at low tempe ratures? One would think that the chemical reactions would be slowed consid erably.

I recently discovered that my Black & Decker 2 amp charger is not temperatu re compensated and it also does not have a constant voltage phase for satur ation of the battery. At lower temperatures, the 2 amp constant current cha rge results in surface charge building up rapidly and the unit switches to float mode prematurely.

I also have the new switching version of the Battery Tender Plus which prev iously was a linear design. The charger is now temperature compensated. Thi s device does implement the constant current and constant voltage phases fo r saturation of the battery.

Lastly, I recently tested the new CTEK MXS 5.0 charger which is quite impre ssive. It has an eight stage charging algorithm with optional reconditionin g mode. The saturation phase can take several hours at 14.5 volts or higher . After monitoring these chargers, I can now see the significant limitation s in my car's charging system.

Reply to
kt77
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The free energy of the chemical reaction involved does depends on temperature.

Chemical reactions do tend to get slower at lower temperatures, but this doesn't seem to be a problem with batteries. Electrolytes get more resistive at low temperatures, which can be more of a problem.

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Bill Sloman, Sydney
Reply to
bill.sloman

not be very precise. This morning I measured my battery voltage at the batt ery terminals 36 hours after removing my battery maintainer. The voltage re ad 12.70 volts. I then opened the driver side car door which apparently res ults in some current flow. The battery voltage dropped to 12.60 volts and t hen drifted down to 12.48 volts within a few minutes.

ter about 25 minutes. I've checked this battery on quite a few occasions an d temperature also seems to be a factor. It's not clear if voltage readings are any more meaningful at lower states of charge. The table I have been r eferencing shows 100% charge at 12.7 volts, 75% charge at 12.4 volts, 50% c harge at 12.2 volts, 25% charge at 12.0 volts, and 0% charge at 11.9 volts.

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Battery voltage is a logarithmic function of reagent concentration. When a battery is close to fully charged there's not a lot of the unchanged reagen t, and a lot of the charged reagent, and it doesn't take much discharge to shift the voltage appreciably.

It's also a function of battery temperature, which goes up a bit - due to o hmic heating - whenever you pull charge out of it.

The voltage you read at the terminals can drift around a bit for all sorts of reasons.

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Bill Sloman, Sydney
Reply to
bill.sloman

doesn't seem to be a problem with batteries. Electrolytes get more resistiv e at low temperatures, which can be more of a problem.

I found some information on the temperature compensation used with lead-aci d batteries. The temperature compensation defines the maximum charge voltag e per cell and the float voltage per cell for any specified temperature. Th e objective is to prevent overcharging and extend the life of the battery.

Car batteries are typically exposed to ambient temperatures in the range of -40 to +120 degrees F. Discharge capacity is reduced at low temperatures a nd I suspect that charging is less effective even with the temperature comp ensation. It makes you wonder if car batteries were being charged adequatel y in the recent very cold winter.

The logarithmic relationship you mentioned is quite interesting and does se em to explain the sensitivity in the voltage readings.

Thanks for both of your replies.

Reply to
kt77

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