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Old Jan 18, 2013, 02:37 PM
jv8
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regenerative discharge: two PL8's into one battery?

Is it possible to hook up two PL8's to a single AGM battery and have both PL8's regeneratively discharge into that battery at the same time?
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Old Jan 18, 2013, 07:00 PM
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Yes, but make sure you don't over-fill it.
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Old Jan 19, 2013, 10:51 AM
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Quote:
Originally Posted by jv8 View Post
Is it possible to hook up two PL8's to a single AGM battery and have both PL8's regeneratively discharge into that battery at the same time?
Hi:

According to the design engineer, this should be no problem but you'll want to use some fairly sizable AGMs, like 40AH at least.

Tim Marks
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Old Jan 25, 2013, 01:34 PM
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I was about to post a similar question..

May I use 2 PL8 to regenerative discharge a single LiPo??

I need to test some lipos performance on high current discharge, so I was thinking about using 2 PL8 to discharge them at 80A max.

The power will be directed to a bank of 2 AGM 75Ah (24V 75Ah).

Alex.
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Old Jan 25, 2013, 05:41 PM
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Originally Posted by SkyRaptor View Post
I was about to post a similar question..

May I use 2 PL8 to regenerative discharge a single LiPo??

I need to test some lipos performance on high current discharge, so I was thinking about using 2 PL8 to discharge them at 80A max.

The power will be directed to a bank of 2 AGM 75Ah (24V 75Ah).

Alex.
Hi:

This is a completely different scenario you present. I'm checking with the design engineer. I advise you don't try this until you hear back from me one way or the other. I will post again when I get the answer to your question.

Tim Marks
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Old Jan 25, 2013, 10:55 PM
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Hi:

This is a completely different scenario you present. I'm checking with the design engineer. I advise you don't try this until you hear back from me one way or the other. I will post again when I get the answer to your question.

Tim Marks
Hi:

Here's the follow up from our design engineer:

The problem is ground current loops on the negative terminal. PL8 senses charge current on the negative side of the LiPo. The only way to use two or more PL8ís to discharge a single LiPo is to have all the chargers on separate AGM supply batteries. This way, each PL8 senses itís own charge current separately without interference from the other chargers. So, this customer will need to buy 2 more 12V AGM batteries. Or, they could split up their 2 existing AGM batteries and run each charger from itís own isolated 12V AGM battery.

If this customer is using expansion channel, they could connect a 1 ohm 100 watt resistor between the negative terminals of the isolated AGM batteries so that the data communication will work correctly. This method will be good up to 16 PL8 charger on the same LiPo. So, he should be able to go up to 640A discharge current provided each PL8 is on itís own isolated AGM battery.

So it's possible, but you need to be careful. Let me know if you have any questions.

Tim Marks
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Old Jan 26, 2013, 11:21 AM
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Thanks Tim for this great support.

But I will make things a little bit more difficult.

Ok, no problem discharging with each PL8 using its own battery.

And what about charging the same LiPo with two PL8 in parallel??

I make this question because I'm planning to run an endurance test with some lipos.. So I need to run hundreds of charge/discharge cycles.. and to discharge with high current, I need both PL8 tied in parallel.. so this same configuration should be used to charge and run all those cycles.. is it possible??

Thanks again.

Alex.
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Old Jan 27, 2013, 12:56 AM
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Originally Posted by SkyRaptor View Post
Thanks Tim for this great support.

But I will make things a little bit more difficult.

Ok, no problem discharging with each PL8 using its own battery.

And what about charging the same LiPo with two PL8 in parallel??

I make this question because I'm planning to run an endurance test with some lipos.. So I need to run hundreds of charge/discharge cycles.. and to discharge with high current, I need both PL8 tied in parallel.. so this same configuration should be used to charge and run all those cycles.. is it possible??

Thanks again.

Alex.
Hi:

Design engineer says the same setup will work for charging and also...


I forgot to say that he should put some power supplies on the batteries too. The power supplies should be set to 12.000V or 24.000V to maintain the AGM cells at 50% state of charge. They way, he can do infinite cycles.



Also, the chargers should be set up to expansion channel.

One last thing. I forgot to say that the power supplies need to be current limiting and have output grounds that are isolated from earth ground.

See attached schematic. Sorry, it's not too pretty. Hope you can read it.

Tim Marks
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Old Jan 27, 2013, 04:58 AM
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Tim, you guys from Revo are awesome!!!

I'm gonna do such setup.. but I don't need a PS charging the AGMs since I run one hundred cycles each time and then stop to save the log. So I can charge the AGMs between runs.

BTW, the Powerlab is an amazing tool, not only a battery charge. Just a hint: It would be great if we were able to set how many cycles to run; today the max number is 20 or infinite. More options like 50, 100 and 200 are welcome.

Thanks again for this great support.

Alex.
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Old Jan 27, 2013, 01:58 PM
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Quote:
Originally Posted by SkyRaptor View Post
Tim, you guys from Revo are awesome!!!

I'm gonna do such setup.. but I don't need a PS charging the AGMs since I run one hundred cycles each time and then stop to save the log. So I can charge the AGMs between runs.

BTW, the Powerlab is an amazing tool, not only a battery charge. Just a hint: It would be great if we were able to set how many cycles to run; today the max number is 20 or infinite. More options like 50, 100 and 200 are welcome.

Thanks again for this great support.

Alex.
Hi Alex:

Thanks! I have added your request to our new feature request spreadsheet.

Tim Marks
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Old Feb 14, 2013, 06:53 AM
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Hi Tim,

I tried such design to cycle the batteries, but it is quite fragile.

After a few cycles (sometimes in the second, other in the 18th), the chargers stop and issue an error.. I have noted 2 errors:

- "Cell No Add Up" during charge;
- "Safety Code #97 Amps were not read on startup": Before beginning a charge or discharge;

Both errors happens randomly on Primary or Expansion1.

I'm using a similar setup your engineer told us.. the difference I'm not charging the AGMs continuously (since one single charge gives me 200 cycles) and the resistor tying the AGMs is about 2Ohms 150W.

Thanks.

Alex.
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