Help with current limiting on etrike

[Hank]

Hi, first post from a noob. I recently built an etrike using a 48 volt 1000 watt BLDC hub motor. The trike is powered by 4 12 volt 18ah sealed lead acid batteries. I have added a Honda eu1000 generator and a mean well ac to dc 48 volt 21 amp power supply (https://www.jameco.com/z/RSP-1000-4...8-Volt-21-Amp-1008-Watt-with-PFC_1585725.html). I am trying to create a hybrid that will run off either the batteries or directly from the generator/power supply.

The problem that I am trying to solve is the generator is a bit small for the application, but it is the only generator I have, so I am going to use it. The power supply puts out 21 amps and is voltage adjustable. I want to limit the current to about 15 amps but keep the voltage constant at about 50 volts. I tried connecting the power supply directly to the motor controller which overloaded the generator when accelerating. I then connected the power supply to the battery bank which worked better but required that I turn down the voltage when going up a hill.

Here is the question. Is there an add on device to keep the voltage constant but limit the current to 15 amps? I read that using a resistor would limit the current but wouldn't it also limit the voltage? Thanks for any help, I have very limited electronic knowledge.

 

[duke37]

You cannot do this, the current will depend on the voltage. You can control voltage and maximum current but not at the same time.

 

[kellys_eye]

There's nothing wrong with using the Honda generator to power a charger connected to the batteries - this gives you the same functionality i.e. movement via battery or generator but the generator is used to deliver both the locomotion AND charge the batteries.

What you then have to contend with is ensuring that the battery charge never falls to a level such that the charger is delivering ALL the current (which it can't). In true hybrid vehicles they don't allow the batteries to go 'flat' but kick in the generator to 'assist' with movement and, at the same time, recharge the batteries well before they go flat.

Since movement doesn't always require the full 1000W delivered to the motor (down slopes, flat surfaces etc) there is plenty of opportunity to keep the batteries fully charged and/or power the vehicle via the generator output during these low current situations.

The only 'failure' with such systems is if you're on a constant, never-ending, up slope!

 

[Hank]

How many amps could a charger be run at without prematurely ruining the batteries?

 

[kellys_eye]

When the charger is running the output will be split between the load and the batteries. The load will take what it needs up to the maximum the charger can deliver then the batteries will provide the 'remaining' current - assuming it is required.

When the load isn't taking 100% from the charger the difference is used to charge the batteries. The idea is to keep the batteries with sufficient charge that the total load demand never exceeds what the batteries/charger can deliver when working together.

The batteries will take whatever charge they can - the charger itself will determine that (usually 0.25 x the total Ahr capacity so, in your case, 18A max).