Thanks for the input Cork ie. The machine came with two inexpensive 24v (110vac input) chargers. I am using them to charge 4ea of the 6volt batteries in series. If I had mains power where the lift will be, I would just buy a 48 volt golf car charger and be done with it.
Not to hijack thread, but there is a need for the kind of setup we're looking at. In the vineyards, there are quite a few jobs that require moving a lightweight machine a short distance at a time with off cycles greater than on time. I hate to have an ICE engine idling so much of the time. But like most people farmers hate to buy batteries. With a hybrid system, four relatively inexpensive Pba batteries could be used, and a lawnmower engine could be run to charge or supplement battery pack. I'll start a thread on this later as I'd like to solicit suggestions on the best way to reach this goal.

 

trainpilot as far as I understand it is very difficult to reach 65 mph speeds with a 48 volt system. I believe it has to do with the hp of your motor relative to voltage. What is your donor ( vehicle you will put the electric system into) vehicle going to be? The folks on here can help you with the Gross Vehicle Weight and Horse Power figures. It takes a know amount of hp to reach and maintain 65 mph relative to your finished vehicle weight. I would post on that subject first to make sure your lift parts will be able to give you the required sustained speeds for your distance.

Keep up all up to date, when I have more results to report I will keep you in the loop. Just a thought you might not be aware of. Power generators both AC and DC have a difference in the amount they can produce cold and warm. As they (the windings in the generator/alternator) warm up they produce less. Under max load they all reach the lower level very quickly. This is why on the high end audio forums you will see references to voltage output warm and cold.

 

an automotive alternator with the diodes replaced or diodes external can charge higher than 48. In an auto they typically turn 2.8 times engine speed so they are not strangers to high rpm. Your field current and rpm determine the output. Increase either one and you get more. I think the usual regulator supplies the field with about 8 volts maximum.

 

Found this thread because I am building several e-bikes and wanted to have a range extender and more importantly, cannot afford the LiFePO4 batteries to mount on bike. The first design uses a single 500 watt 24v motor attached underneath the frame and powers the chain so that the the gears on the rear sprocket are utilized. The second design uses 2 500 watt hub motors. Rather than hang lithium batteries from the frame, I plan to build a trailer to carry the batteries. I have two HF motors, one 79cc 3hp and a 212cc 6.5hp. The smaller motor will most likely use a direct drive PM motor as a generator. The engine will run at a fixed RPM and I plan speed regulation of engine to control voltage. I will be using multiple Lead Acid batteries in series to 24v. Do I need to put a protection circuit to prevent overcharge? If so, how can I accomplish that? Maybe a simple gauge to show battery capacity and manually turn off when charged? The second design is the larger motor and possibly ultra-capacitors (since the motor is already heavy without two LA batteries) directly connected to the motor controllers. In both designs, I will be using 24v battery banks and or Ultra-capacitors and motors and want to use automotive alternators or PM motors as generators and am very interested in the voltage regulation and overcharge protection circuitry needed. Any helpful advice is welcome.

In deference to the original design concept of in this post, I also know several people who are very interested in this concept. This design could employ a Sterling external combustion or even a steam engine with many fuel options. It is help with electronics I am looking for, not a judgement on my use of resources.

 

The field voltage is very easy to change on an automotive alternator, probably all you need to do is set maximum voltage out to the charging voltage of the 24v batteries as it is done in an automobile where it is limited to ~14.5 volts for the 12v system at all times.
The current rating of a automotive alternator is greatly over rated.
You only have to look at the size to realize how long will it be able to supply 120amps for that size of unit?
It will only supply this for a very short period.
Max.

 

Would there be any advantage to using a PM brush motor as the generator instead of using an alternator? In either case, couldn't I use a voltage regulator between charger and batteries to prevent overcharge?

 

IMO, all you would need is a current capable generator/alternator and a means of keeping the max voltage limit to 29v-30v.
If you can find a properly sized DC motor, the ideal would be wound field rather than P.M. it would be relatively easy to regulate.
Many old spindle motors for milling machines or lathes would be a good source.
Max.

 

I'm going to start a new thread. How to convert a 12v alternator to 24v. I've searched the Internet and do not have specific enough information exactly how to do it. Thanks for the help Max

 

The output is controlled via the rotor current via the two brushes and slip rings.
The automotive version uses a PWM controlled regulator to set the output at 14.5v.
Max.