[Green Machines]

Hi, I have a Sigmadrive controller that lets me set the amount of regeneration. (I don't have a pot on the brake pedal yet, so it only regenerates on deceleration.)

My question is 'how many amps can I safely push into my 60ah lead acids?' Can I push a whole bunch of amps in for brief periods or not?

My charger only ever reads about 15amps, so that's what I have the max regen set at.

My on-board amp meter only reads into the negative (charging) a few times during a trip. Is it worth putting a pot on the brake too?

thanks

 

[DIYguy]

What kind of pb are they? Flooded, gel, or AGM? AGM's can take some high currents, flooded and GEL's you have to be careful with....

 

[Green Machines]

They are sealed, wet cells.

I've just downloaded the specs and it says:
'Charge Methods:
Constant Voltage Charge 77oF(25oC)
Cycle use 14.4-14.7V
Maximum charging current 18A
Temperature compensation -30mV/oC'

So is 18A it?

 

[major]

My question is 'how many amps can I safely push into my 60ah lead acids?' Can I push a whole bunch of amps in for brief periods or not?

Hi Green,

I've always been an aggressive regenner. I see no reason to set the current limits for regen less than what you have for acceleration.

Is it worth putting a pot on the brake too?

That is my preference.

Regards,

major

.........regenner Might be a new word

 

[rillip3]

Got to be careful with that one, looks like reneger. Same letters, totally different meaning.

If you want to follow the manufacturer's instructions, you should set the regen limit to a max of 18 A. In reality, not 100% of that regen will make it to the batteries, however. It depends on where your meter is getting it's number. For example, putting 18 A into the charger is no problem; the charger has efficiency losses, so 18 A in is not 18 A to the batteries. If that meter is giving the amperage leaving the charger, then it's up to you to follow or ignore the manufacturer's instructions regarding charging.

 

[DIYguy]

Sounds like they might be GEL's. The specs should say if they are AGM (Absorbed Glass Matt). At any rate.... one thing to be careful with is the "room" for regen energy. Most advanced designs using regen never fully charge the pack. You need to leave it partially discharged.... or not engage regen until you've gone a few miles....

Good luck!

 

[gottdi]

I'm with Major on this one. If you can pull higher amps during acceleration then your regen should match that. Remember that regen is usually only for a few brief seconds at best each time so a quick burst back into the system won't kill your batteries. It is not like your charging your pack for a specific duration.

So what kind of amps are you seeing during acceleration?

 

[Green Machines]

I've set max amps (drawing) at 300A, my dash amp meter only goes up to 200A so I don't know exactly what it's drawing at the top, it's over 200 at times.

I try to drive at under 100A, it's 50A cruising at 30mph in town, which is what I do most of the time. 100A-150A for acceleration and hills.

The maximum regeneration possible from the controller is 50A (in). When set to allow it, it will peak up to that momentarily when I take my foot off, then slowly drop to zero just before the car stops.

There's also a delay setting, that delays acceleration and deceleration, this has a great impact on regen when set at as little as 0.2 of a second delay. It looks like the bulk of the regen comes immediately upon the change from acceleration to deceleration. By having this set at 0.2 seconds it lessens the harshness of the jump up in amps, maybe that's a good thing?

 

[major]

I've set max amps (drawing) at 300A, my dash amp meter only goes up to 200A so I don't know exactly what it's drawing at the top, it's over 200 at times.

I try to drive at under 100A, it's 50A cruising at 30mph in town, which is what I do most of the time. 100A-150A for acceleration and hills.

The maximum regeneration possible from the controller is 50A (in). When set to allow it, it will peak up to that momentarily when I take my foot off, then slowly drop to zero just before the car stops.

There's also a delay setting, that delays acceleration and deceleration, this has a great impact on regen when set at as little as 0.2 of a second delay. It looks like the bulk of the regen comes immediately upon the change from acceleration to deceleration. By having this set at 0.2 seconds it lessens the harshness of the jump up in amps, maybe that's a good thing?

No offense mate, but sounds like a crappy controller.

I'd complain to the one you bought it from.

major

 

[etischer]

Make sure to program in a way to limit regen based on voltage too.

I limit my regen to 100A. Above 330 volts the regen torque tapers to zero so my battery voltage never rises above 335. On a fully charged pack, you don't want to pump in 100A, even for a few seconds. I've hit 400V on a few occasions by accident, it wouldn't be hard to blow up your inverter. The voltage rise can be quicker than the software can shut the inverter off. Using the taper method works better than having a hard cutoff limit.

 

[major]

Make sure to program in a way to limit regen based on voltage too.

I limit my regen to 100A. Above 330 volts the regen torque tapers to zero so my battery voltage never rises above 335. On a fully charged pack, you don't want to pump in 100A, even for a few seconds. I've hit 400V on a few occasions by accident, it wouldn't be hard to blow up your inverter. The voltage rise can be quicker than the software can shut the inverter off. Using the taper method works better than having a hard cutoff limit.

Good point etischer. This is a feature which was incorporated into the systems which I used. Without it, the inverter would simply fault or trip shutting off abruptly at the overvoltage (OV) set point.

This type of algorithm will cause a fade in regen torque as the voltage rises too high. If you put the regen control (input command) pot on the brake pedal, when this happens, all you need to do is push harder on the pedal and get into the friction brakes to make an easy controllable stop. It is very intuitive.

major