Regen Voltage

[Rusttree]

Anyone have an idea what the maximum output voltage the generator produces when it's on full regeneration mode? Specifically, I'm trying to figure out the max voltage applied to the battery when it is getting recharged. I'm guessing for our IMA battery it's somewhere close to 200V.

Alternatively, if anyone knows the rules regarding the safe upper voltage that can be applied to a battery to recharge it, that would be just as helpful.

[b1shmu63]

There is no safe way to use voltage limiting as a way to charge Ni-Mh batteries, PERIOD! That is why even the cheapest charger uses a timer charges at a fixed current and assumes the battery is dead when you put it in. The IMA system uses three Hall effect current sensors and a computer to achieve proper charging.

[Rusttree]

Yeah that's what I've been learning recently while doing research on recharge controllers and such. I'm taking the assumption that the BCM is the unit that is actively controlling the recharge (where you mention the Hall effect current sensors). What I'm trying to figure out is what voltage Honda designed the battery to be recharged at. Some of the data I've reviewed suggests the battery acheives voltages in the upper 180's, so I'm assuming the charge voltage can reach near 200 during full regen mode.

[b1shmu63]

Ok, well it sounds like you have been doing the right kind of research. The other thing to consider is that the voltage on the batteries will vary with temperature so that the voltage you will see across the IMA batteries depends on the charge rate, the level of charge and the temperature of the batteries. Battery voltage/temperature will go up if the batteries are being exercised vigorously. Hybrid batteries owe their efficiency in part to their low internal resistance. This characteristic makes it impossible to get an accurate "read" on the battery full condition using real time voltage or current measurements. The only safe test is to discharge the battery until the voltage begins to go down as the internal resistance begins to go up. This is what happens during a recalibration cycle. Thereafter it is back to ded reckoning using the current/time and the computer. Should the hybrid batteries ever become fully charged they stop storing energy and start generating gas and heat. You don't want to go there.

[Armin]

Rusttree,

you're close. The highest peak I have measured on the battery during max regen when the battery is almost full is about 190V.

As others pointed out, this has nothing to do with charge management. It's simply the result of passing about 40 Amps of charge current through the batteries internal series resistane of about 0.5 Ohms and adding that to the about 166 to 168V no-load voltage of a full battery.