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Can I run two DC-DC chargers in parallel to speed up battery charging?

Ample

Ample

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I have a 40A DC-DC LiFePO4 charger now. If I increase the size of my LiFePO4 battery bank, I'd like to increase the amount of charging amperage otherwise, it will take longer to charge up the bank.

I'm thinking it might be an idea to add a 2nd charger in parallel on my alternator. The alternator will easily handle 80A.

Will this work? Or will the 2 chargers "fight" each other?

Edit: to note that it's a LiFePO4 bank and charger.
 
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Parallel chargers is pretty normal fare. They won't fight each other since they are both trying to do the same thing, provide current to the battery.
Component tolerances will see one device have a lower output voltage than the other. This will make itself felt towards the end of the charge cycle.

Once the battery voltage passes the point the lower charger is targetting the bulk of the current, all of it in pretty short order, will come from the higher voltage charger. That's not really a concern as the charge current has probably tailed off a fair bit at this point so it won't result in longer charge times and the current limited nature of the chargers will mean the charger can't be overloaded.
 
gnubie said:
Parallel chargers is pretty normal fare. They won't fight each other since they are both trying to do the same thing, provide current to the battery.
Component tolerances will see one device have a lower output voltage than the other. This will make itself felt towards the end of the charge cycle.

Once the battery voltage passes the point the lower charger is targetting the bulk of the current, all of it in pretty short order, will come from the higher voltage charger. That's not really a concern as the charge current has probably tailed off a fair bit at this point so it won't result in longer charge times and the current limited nature of the chargers will mean the charger can't be overloaded.
Click to expand...

Thanks! I updated my post to clarify that I'm running a LiFePO4 system, both the battery bank and the DC-DC charger are designed for LiFePO4. Will this change your thoughts?
 
It makes no difference really. The chargers just follow a different charging strategy. About the only thing to keep in mind with lifepo4 charging is that they don't get parked at elevated voltages for longer than necessary. A proper lithium charger won't have any issues doing this, even if there are 2 in parallel.
 
HRTKD said:
Yes, but how long will your alternator support that level of output?
Click to expand...

This would be something I would be concerned about too. But OP says their alternator can easily handle the 80A, hopefully that is continuous.

Ample said:
I'm thinking it might be an idea to add a 2nd charger in parallel on my alternator. The alternator will easily handle 80A.

Will this work? Or will the 2 chargers "fight" each other?
Click to expand...

Not sure what charger you have (from the current rating I'm guessing Renogy), but from the Victron Orion-TR Smart product descrtion:
Models are available up to 400W and unlimited multiple units can be connected in parallel to increase output power.
Click to expand...
 
HRTKD said:
Yes, but how long will your alternator support that level of output?
Click to expand...

It's a 220A alternator. So I think that as far a max output goes, it will be fine. What I don't know is whether or not it will supply 80A continuously for a long time when idling.
 
Dzl said:
This would be something I would be concerned about too. But OP says their alternator can easily handle the 80A, hopefully that is continuous.



Not sure what charger you have (from the current rating I'm guessing Renogy), but from the Victron Orion-TR Smart product descrtion:
Click to expand...

Yes, it's the Renogy. Alternator is rated for 220A. Thanks for the note on the Victron. Hopefully the Renogy is like that too.
 
Ample said:
It's a 220A alternator. So I think that as far a max output goes, it will be fine. What I don't know is whether or not it will supply 80A continuously for a long time when idling.
Click to expand...

What type of vehicle, I don't have any insight, but I would guess if its a commercial vehicle that might have a refrigeration unit, or be specc'ed as an ambulance, or other type of vehicle that would require a lot of power at idle, that the alternator would be much more likely to be able to handle continuous high output.

One other (less common) option you could look into is an external regulator. This is more common in boats than vehicles. I believe these work by regulating output based partially on temperature, which I believe is why alternators fail at high continuous output.
 
Dzl said:
What type of vehicle, I don't have any insight, but I would guess if its a commercial vehicle that might have a refrigeration unit, or be specc'ed as an ambulance, or other type of vehicle that would require a lot of power at idle, that the alternator would be much more likely to be able to handle continuous high output.

One other (less common) option you could look into is an external regulator. This is more common in boats than vehicles. I believe these work by regulating output based partially on temperature, which I believe is why alternators fail at high continuous output.
Click to expand...

It's a van commonly used for couriers, etc. The stock alternator is 180A I think and the one I have is the optional 220A factory upgrade for commercial vehicles such as ambulances and shuttle buses.
 
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Update: a Renogy rep said that my 40A DC-DC charger should NOT be used in parallel as 2 of them will conflict.

They make a 60A unit, but it's on backorder and it's a fair bit more expensive.

I may look into the 60A unit if it ever goes on sale as faster charging is a "want" vs. a "need".
 
gnubie said:
Now ask them to explain how they will conflict. At this point their script will run out so it should get interesting.
Click to expand...

Renogy tech support has a very limited depth of knowledge (and this is coming from someone who has a very limited depth of knowledge ;)). The amount of times I've seen people posting here who received bad advice, no advice, or confused and sometimes contradictory advice from renogy has got to be in the dozens by now.

@Ample if you end up replacing the unit with a larger capacity dc-dc charger you could consider going with a different brand. Sterling power makes the highest amperage chargers i'm aware of (60A, and up to 120A in some cases), Victron would be my top choice based on the bit I've read/researched, but they don't have high amperage models. Other brands include Redarc, Renogy, and Cotek.
 
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Dzl said:
Renogy tech support has a very limited depth of knowledge (and this is coming from someone who has a very limited depth of knowledge ;)). The amount of times I've seen people posting here who received bad advice, no advice, or confused and sometimes contradictory advice from renogy has got to be in the dozens by now.

@Ample if you end up replacing the unit with a larger capacity dc-dc charger consider going with a different brand. Sterling power makes the highest amperage chargers i'm aware of (60A, and up to 120A in some cases), Victron would be my top choice based on what I've read/researched, but they don't have high amperage models. Other brands include Redarc, Renogy, and Cotek.
Click to expand...

Actually, my experience with Renogy as been very good. Maybe the complaints are a sign of their success or rapid growth making them add new people who then need to get up to speed. But they helped me a fair bit when I was designing my system 2 years ago.

I'd like to go Sterling or Victron but because my vehicle is used infrequently, it's a bit harder to justify. If I was powering something critical, then for sure.

But it's just a fun vehicle. And back when I was (more of) a noob, Renogy provided the perfect balance of value and performance. I would still recommend them.

Back in the day and in a former life, I spent good money on enterprise-level equipment.

But since I'm a geek at heart (as you can tell from my other zany threads here...) I like to occasionally pursue slightly off-beat solutions. :)
 
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Ample said:
It's a 220A alternator. So I think that as far a max output goes, it will be fine. What I don't know is whether or not it will supply 80A continuously for a long time when idling.
Click to expand...
It could burn up. An alternator needs air cooling to handle high power output. When the engine is idling, the fan is barely turning.

Cop cars and ambulances have to deal with this. They often have a second, beefier alternator to handle electrical loads.
 
My truck, which is not a special purpose vehicle, has dual alternators from the factory. 220 Ah and 157 Ah. They don't both operate at the same time. The factory rating of 377 Ah, isn't going to be 377 Ah at the same time.
 
Ample said:
Update: a Renogy rep said that my 40A DC-DC charger should NOT be used in parallel as 2 of them will conflict.

They make a 60A unit, but it's on backorder and it's a fair bit more expensive.

I may look into the 60A unit if it ever goes on sale as faster charging is a "want" vs. a "need".
Click to expand...
Keep in mind that a 40 amp output means 50 amps input.
 
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