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Old 01-01-2016, 12:58 PM   #1 (permalink)
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Default External discharge resistor ?

There is a main page thread about quick discharging batteries. Someone suggested that some chargers could be used with an external discharge resistor.

Are the PL8's capable of doing that with something like the following?

http://www.ebay.com/itm/1000W-1ohm-a...a5c&rmvSB=true
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Old 01-02-2016, 12:53 AM   #2 (permalink)
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For the PL8 V2:
PL8 is regenerative discharge to a lead acid battery up to 40A, 1344 watt max.

For the Dual PL 8x2
PL 8x2 regenerative discharge supports up to 40A, 1344 watts per channel max.

In either case the charger needs to be powered by the lead acid battery in order for this to work.

I haven't seen a provision to add an external power resistor into the discharge circuit of the charger.
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Old 01-02-2016, 09:46 AM   #3 (permalink)
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Fair enough. Just curious.

I'll probably be better off keeping these discharge resistors separate anyway. I'll be in a position to charge and discharge about as fast as I could ever want pretty shortly.
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Old 02-13-2016, 09:57 AM   #4 (permalink)
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I was really hoping the PL8 supported this, too.
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Old 02-13-2016, 02:10 PM   #5 (permalink)
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Quote:
Originally Posted by Rodney Kirstine View Post
I was really hoping the PL8 supported this, too.
I think most guys just connect/switch a resistive load on as needed to pull their lead acid battery voltage down low enough to allow the PowerLab to reach the desired discharge rate. It's a fairly simple thing to add and you just connect as needed when you see the PowerLab limiting discharge current due to lead acid battery reaching max volts.
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Old 02-13-2016, 02:39 PM   #6 (permalink)
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Quote:
Originally Posted by RevoKelly View Post
I think most guys just connect/switch a resistive load on as needed to pull their lead acid battery voltage down low enough to allow the PowerLab to reach the desired discharge rate. It's a fairly simple thing to add and you just connect as needed when you see the PowerLab limiting discharge current due to lead acid battery reaching max volts.

I set this up very recently but had never heard of using a large resistor to discharge before I started looking at this.

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Old 02-13-2016, 02:59 PM   #7 (permalink)
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i run 2 cooling fan motors (from a mazda) in series for 6s packs, i can do a fully charged 6s 5000mah in about 15min with very minimal noise (BLADES REMOVED !!) from the motors. They pull aprx 10@ when i put a amp meter on it.
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Old 02-13-2016, 09:06 PM   #8 (permalink)
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Quote:
Originally Posted by RevoKelly View Post
I think most guys just connect/switch a resistive load on as needed to pull their lead acid battery voltage down low enough to allow the PowerLab to reach the desired discharge rate. It's a fairly simple thing to add and you just connect as needed when you see the PowerLab limiting discharge current due to lead acid battery reaching max volts.
I don't use a lead acid battery to run my charger. For me, having the option to connect to a resistive load and then control the discharge with the PL8 would be really nice. In the scenario you mention, I have to buy the load resistors and a deep cycle lead acid battery instead of just load resistors.
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Old 02-15-2016, 05:10 AM   #9 (permalink)
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This exact scenario is why I keep my iCharger around even though 99.9% of my charging is done with the DPL8.
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Old 02-15-2016, 12:44 PM   #10 (permalink)
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Quote:
Originally Posted by Rodney Kirstine View Post
I don't use a lead acid battery to run my charger. For me, having the option to connect to a resistive load and then control the discharge with the PL8 would be really nice. In the scenario you mention, I have to buy the load resistors and a deep cycle lead acid battery instead of just load resistors.
Yep, understood - for guys that wouldn't normally require off-grid charging, it is not a convenient solution and a standalone discharge solution would make more sense. We're kicking some ideas around on how to address this need using the PowerLab - will keep you posted.
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Old 02-15-2016, 03:56 PM   #11 (permalink)
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Nice! I know it's not always possible to add some things that were never part of the original scope of the project but it's really great to hear that you're looking into if it can be done.
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Old 02-24-2016, 10:12 PM   #12 (permalink)
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Quote:
Originally Posted by RevoKelly View Post
Yep, understood - for guys that wouldn't normally require off-grid charging, it is not a convenient solution and a standalone discharge solution would make more sense. We're kicking some ideas around on how to address this need using the PowerLab - will keep you posted.
I hope it works out! It's the one thing I want my DPL8 to do that it currently doesn't.
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Old 08-09-2016, 06:18 PM   #13 (permalink)
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RevoKelly - any update on this effort?
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Old 08-10-2016, 11:29 PM   #14 (permalink)
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I don't have anything I can publicly discuss yet, but we're working on it.

In the interim, I've found a workaround setup that works quite nicely if you're running on 12v or 24v power supply and you don't normally use the Battery supply setup in your PowerLab ...

SETUP

1. Find a suitable resistive load which, when powered by your switching power supply voltage, results in a wattage load that meets your discharge requirements, but does not exceed the amps capability of your power supply ... for example, connecting a 1 ohm resistive load to a 24v power supply will result in 24A and 576W. (V = I x R)

2. Setup the PowerLab Battery supply settings as follows:

Battery Low Voltage Out = { slightly less than your power supply voltage }
Battery Max Amps Out = { max amps rating of your power supply }
Enable Regenerative Discharge: enabled
Regen Amps IN to Pb = { slightly less than resistive load current }
Regen Volt IN to Pb = { slightly higher than your power supply voltage }

So for my setup, I have a 24.6v power supply capable of 75A, and a resistive load (modified hair dryer) which is 0.75 ohm. When attached to that 24.6v supply, the resistive load will draw 32.8A and 807W. So my PowerLab setup values are:

Battery Low Voltage Out = 11.9V/23.8v (slightly under 12.3/24.6v)
Battery Max Amps Out = 40A (limit of DPL)
Enable Regenerative Discharge: enabled
Regen Amps IN to Pb = 32A (slightly under 32.8A of resistive load)
Regen Volt IN to Pb = 12.5/25V (slightly above 24.6v power supply)

This setup gives me about 800W of discharge for my Dual PowerLab - so takiing a 12S (pair of 6S) 5000 packs from full to storage can be done at 30A which only takes about 5 mins.

OPERATION

When you need to do a high-wattage discharge (something higher than the internal discharge limits of the Powerlab), simply :

1. Switch the PowerLab supply setting to Battery (to enable regen discharge)
2. Connect your external discharge load to your power supply
3. Start your discharge
4. When your discharge completes (and all chargers are idle), disconnect your resistive load

CAUTION: Never connect/disconnect the resistive load (or any other significant power load) while *ANY* PowerLab charger is active !!! The PowerLab manual will tell you the same thing, but just reiterating the same precaution when it comes to the external discharge load.

HOW IT WORKS

As the regen discharge current ramps up, the load on your switching power supply will go down ... the PowerLab basically takes over supplying most of the power to the external discharge resistor while the power supply continues to provide (at least) a small amount of power, therefore it is able to continue to regulate the output voltage.

The nice thing here is that it doesn't tie-up one of your charger ports - for example, both sides of your Dual PowerLab can be used to discharge a 12S pack.
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Old 03-31-2017, 03:38 PM   #15 (permalink)
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Kelly,

Any update on the FMA discharge solution?
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