Quote:
Originally Posted by Christ
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Whether or not the modules can be mounted on their side (using the ~25mm dimension as it's height) without potential problems.
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This is an area I'm not sure about. I know KOH has amazing abilities to soak and flow. I suspect at an angle, say 30-45 degrees, it would be OK. The problem would be if the highest parts got depleted and current had to flow through that area. I suspect it won't be a problem as KOH is likely to keep the area saturated.
There has to be 'gas space' in the cell so the gas that is normally created and not absorbed by the metal hydride has a place to collect before it recombines as water. It may simply make part of the electrodes 'dry' and thus not pass current. In short, I'm not absolutely sure how flat they can be and not lose capacity.
Quote:
Originally Posted by Christ
. . .Whether the bike's alternator will charge the battery directly, or need some sort of intervention process to keep from overcharging and destroying the battery.
(The bike's electrical system is 6V, the AC generator charges through a rectifier at a rate of ~7.5V 3.3A at 5k RPM, 8V 6A at 10k RPM.)
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Motorcycle?
There are several parts to the problem. The first is getting enough power out of the AC signal. What happens is no charge passes from the AC generator when the voltages are lower than most of the power cycle. It would only take energy from part of the cycle, the peak voltages.
Now a silicon rectifier has about a 1.2 V forward voltage drop before significant current flows. Using Schottky diodes reduces the forward voltage drop, ~0.6 V. If using a bridge rectifier, there are two diodes in the current flow at any time so it needs 2.4 V additional AC voltage or 1.2 V if using Schottky diodes, on top of the AC voltage. Schottky diodes are used in some automotive alternators and possibly in this case.
Is the rectifier external so you might be able to measure the DC voltage drop across the part? Take the rectifier and a 6 V bulb and connect to the battery and measure the voltage drop across the rectifier and we'll know.
Now as to protecting the battery, a linear voltage regulator, not terribly efficient but a common part, LM350, 3 A. But 3 amps is more suitable for low power electronic power supplies. For example 3 A x 7.2 V = 21.6 W., not very much. Plus a linear regulator is going to eat power, 1.2 V x 3 A = 3.6 W. Cheap parts and simple circuit but inefficient.
If we are dealing with a high efficiency, system, I would recommend something called a synchronous regulator:
- MOSFET switches - very low voltage when ON and higher currents, 10-50 A parts are readily available.
- switches the MOSFETs ON per phase - requires clever drive circuits
Then the other option is to add a switching circuit to step up the voltage from the lower part of AC circuit. At 85-95% efficient, a buck-boost switcher would provide power over a significant part of the AC circuit. But power versions, 10 A are not trivial but easy enough to make. They often use a power MOSFET to drive the switching part that does the work.
Quote:
Originally Posted by Christ
. . .How to properly monitor the battery's SOC and voltage, since they're apparently non-linear. (Gauges? Complex charging circuit? VooDoo?)
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Toyota and others use what are called "columb counters" that track the current and voltage in and out of the battery pack. The reason is the battery voltage is a complex function of the temperature, discharge current and internal resistance. A columb counter doesn't care since it counts charge going in and out.
As for over charge protection, a load-cell or switch that opens if the pressure becomes excessive makes a lot of sense. It just opens the charger (or a relay or power MOSFET) to protect the battery.
Quote:
Originally Posted by Christ
. . .Thanks to all in advance for suggestions, and hopefully a collective of knowledge and input on the topic can help more than just myself and Bob.
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It helps if we have a better description of the application. Especially, the load motor or electronics and the charger or alternator. Understanding the whole system, especially the peak and average loads, will make it much easier to propose an efficient design.
Thanks for initiating the conversation. Hopefully others will like "stone soup" bring their skills to the conversation. <grins>
Bob Wilson