Congrats on getting another one rolling!
The "can solenoid" is the middle speed (second).
First is the tall contactor closing with the dropping resistor in the circuit. (18 volts to motor)
Second is the can solenoid closing bypassing the resistor. (24 volts to motor)
Third is the shorter contactor switching from parallel to series. (48 volts to motor)
Turning on the "ignition" switch should cause the short contactor to switch over from series to parallel. If this isn't happening, then you are starting out with the batteries in series. This would mean about 36 volts in low and 48 volts in second, with no high. This is a great way to burn out a motor or contactor.
To understand your potential charging problem, you have to get an idea of what problems are encountered when charging strings of batteries in series. All batteries are not created equal. Some are going to have higher or lower internal resistance than others. Some are going to have a bit more or less capacity than the others. What this means is as you cycle a string of batteries from full charge to discharged back to full charge and so on, they will slowly get out of synch. During charging, some will reach full charge first, while others are still only part way there. To deal with this, charger designers add an equalization phase at the end of the cycle. During this phase, battery voltage is allowed to climb very high in order to insure all the batteries get to full charge. Unfortunately, there is a problem using sealed batteries with a charger designed for conventional flooded batteries. At the end of the charging cycle the voltage and current will be too high for the sealed batteries. This may cause them to gas, vent, and overheat. You can even encounter a problem called a thermal runaway. In a thermal runaway a fully charged battery is still being charged and begins to heat up. As it heats up its voltage drops causing it to draw more current. This causes more heating result in still lower voltage and even more current draw. If not caught you can end up with batteries going over 200 degrees and actually boiling. This will cause a least a permanent loss of capacity or more likely the permanent destruction of the battery. Some internal gassing is normal in batteries during charging. Flooded batteries gas at the end of the cycle, but they can be refilled with water. Sealed batteries cannot but the still must be equalized. There are several options available to deal with this problem.
Some EVers use "Rudman Regulators" or Batt-Pro regulators, electronic devices which by-pass any current over a certain voltage from the battery to a load. I had a set installed on my Civic EV conversion at one time. What they do, is when the voltage on a particular battery hits a trigger point, say 13.8 volts, the regulator kicks in, putting a 2 to 10 amp load across the battery, I used #1157 stop light bulbs for loads. This prevents the voltage on that battery from going higher, while allowing the other batteries to continue to rise. Of course, adding that load drops the battery's voltage, thereby switching the unit back off. What you end up with is individual units blinking on and off as the whole pack slowly moves towards full charge. Once every single one has blinked at least one, the pack is fully charged.
Another option is PowerCheq equalizers. These use a different method, simply moving electricity from the higher voltage batteries to the lower voltage batteries. Basically they are a 2 amp battery charger powered by two batteries, that compares the voltage of the two and charges one until it matches the other.
Yet another option is to turn down your charger to prevent the voltage from going high enough to damage the sealed batteries. Unfortunately, this will mean you are no longer equalizing them at all. You could solve this by simply charging each battery separately with a cheap 12 volt charger designed for sealed batteries. It would be better to use four, to insure each one gets a full run on its on. Several folks are even doing this as regular charging on EVs. This is referred to as modular chargers. While it works, there is the hazard that one of the chargers might fail and you might not notice. As a result the uncharged battery would get hammered the next time the car was operated. By the time you realize something is wrong that battery has been ruined.
The thing is, all these systems, Batt-Pros, Rudman Regs, and PowerCheqs usually cost more than the simple flooded golf cart batteries your CitiCar was designed for. Adding a $60 PowerCheq to a battery rather than using the $45 dollar battery the car was designed to use isn't good economics. Now if there are safety issues involved, and you have to use sealed batteries, then you are kind of stuck. In that case I would simply get four small 12 volt automatic chargers and take out the original one. That way each battery should get exactly what it wants without harming its neighbors. For a simple 48 volt car this might not be a bad option. On larger conversions with 120 to 192 volts, multiple chargers gets to be a pain.
You can find info on Rudman Regs at:
PowerCheq Equalizers at:
I hope this helps,
Mike Chancey,
'88 Civic EV
Kansas City, Missouri
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