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BFL13

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Posted: 02/10/18 12:08pm Link  |  Quote  |  Print  |  Notify Moderator

ScottG wrote:

2oldman wrote:

OK, yes, parallel batteries might do better separated. Series, no.


Remember, the discussion is about using two chargers. Trying to use two smart chargers for either parallel or series batteries never works well if the two chargers are in parallel.


No idea where you are getting that idea from. Here are four smart chargers in parallel on a bank of three 27s in parallel, all doing just fine. You can see the total amps by adding those up--the total as confirmed on the Trimetric. That maxes out my Honda 3000 gen for VA. Can get more amps than that by using charger(s) with PF correction, but these shown do not have that.

[image]

BTW the most amps I got with multiple chargers was with two PowerMax converters (a 100 with PF correction and a 55 without)on the Honda 3000 plus solar, all set to 14.8v, which had 172 amps showing on the Trimetric. That was on a bank of two T-1275s in parallel, in parallel with two 6s in series, for a four battery bank starting at about 50% SOC.

* This post was edited 02/10/18 12:19pm by BFL13 *


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Harvard

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Posted: 02/10/18 12:29pm Link  |  Quote  |  Print  |  Notify Moderator

I would not do it unless I knew there was some diode auctioneering in the circuits. Diode auctioneering is where one charger will not effect the other charger AND the hardest working charger will "win the auction".

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Posted: 02/10/18 12:45pm Link  |  Quote  |  Print  |  Notify Moderator

I regularly parallel a Schumacher 25 amp smart charger with my 40 amp meanwell rsp-500-15 adjustable voltage power supply when I want to get to Vabs ASAP.

Still takes 20+ minutes of 65 amps on a 50 month old 700+ deep cycle 90AH ~50%Soc Northstar AGM before it reaches 14.7v and this high amperage blast , on this battery, always has a positive effect on voltage held during the next discharges, so when i notice the battery not holding a certain voltage for X amount of load and X amount of AH removed, I figure it is time for the high amp blast, and will deliberately drain the battery further so that it can accept 65 amps for longer.

I usually have to bump the MW voltage a bit over 15 when in parallel, or its amps will start tapering once the battery reaches the 14.2v range, but it depends on what the schumacher thinks it is doing at the time, as the schumacher will try for 16.4v at 25 amps output, sometimes.

So I have to monitor voltage when in the 14.5v range, and I remove the schumacher once amps into the battery taper to below 40 and the meanwell can finish the job from there as fast as possible.

When applying 65 amps to this particular 50% depleted AGM battery, voltage will rise to as high as 14.4 within a minute or 2, but then drop down to as low as 13.5v over the next 5 minutes, then take the next 15 minutes to reclimb back upto 14.5v+.

I imagine if the schumcher were only trying for 14.3, it would give up on this initial voltage climb before the depleted battery has awoken and accepted the high amperage available willingly.

There is no guarantee any particular charging sources are going to work nicely together to increase charging amperage and minimize charging times on any particular amount of capacity or tyoe of battery, flooded vs AGM.
It is likely best if neither charging source uses the same wiring/busses to the battery terminals.

BFL13

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Posted: 02/10/18 12:52pm Link  |  Quote  |  Print  |  Notify Moderator

Harvard wrote:

I would not do it unless I knew there was some diode auctioneering in the circuits. Diode auctioneering is where one charger will not effect the other charger AND the hardest working charger will "win the auction".


Never heard of that. In the above photo, later on during the recharge the three Vector chargers tapered their amps while the 40 amper stayed at 40.4. That one has a voltage of 14.8 while the Vectors have 14.6. Once the 40 amper was the only one left charging, its amps started to taper until it was finished.

The lower voltage charger is not knocked out by the higher voltage charger right off. It is all about the comparative "spreads" between their charging voltages and the battery voltage. With enough spread even the lower voltage charger does its full amps.

Once the battery comes up in its voltage, the spread for the lower voltage charger gets too small for full amps and those amps taper till no spread and no amps. Meanwhile the higher voltage charger may (or may not) still have enough spread to do its full amps. If not, its amps will also taper but not as much as the lower voltage charger's amps are tapering, so the higher voltage charger does indeed end up being the last one to finish.

Another thing is that once total amps taper to where not all the chargers are needed to make that many, you can pull a charger and nothing happens except the remaining chargers' amps jump back up to meet the battery acceptance at the time.

I have observed all this "action" many times. I usually just leave them all connected until it is over (50-90 at 90) but if I am in a hurry to put stuff away I will pull chargers as they become redundant.

Harvard

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Posted: 02/10/18 01:38pm Link  |  Quote  |  Print  |  Notify Moderator

Maybe the smart chargers described have built in diodes like this:

POS--------------|>|------------ + Out
NEG----------------------------- - Out

If these chargers can tolerate a reverse voltage (ie connected up backward), I would bet on this!

ktmrfs

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Posted: 02/10/18 02:08pm Link  |  Quote  |  Print  |  Notify Moderator

I quite often use two PD chargers in parallel when I have enough power available One is a 55A, the other a 65?A. charging four GC. No issue, and I consistently get 110A into the bank for quite a while. and the charge doesn't seem to taper as fast as using one only. Now different chargers may yield different results.


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Posted: 02/10/18 02:38pm Link  |  Quote  |  Print  |  Notify Moderator

Fry the batteries? NO
Faster? YES, however only the first 15 minutes will be twice as fast. For two low batteries you might get them charged in 4 to 5 hours instead of 5 to 6.

Please post your results.


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MrWizard

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Posted: 02/10/18 04:28pm Link  |  Quote  |  Print  |  Notify Moderator

parallel 12v ?
yes..IF the batteries are low enough SOC
if they are taking everything charger #1 can produce, charger #2 might increase total amps into the batteries

this will increase the amps, but only until the amps drop below what the charger with highest voltage can produce, at that time the lesser charger is doing nothing


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BFL13

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Posted: 02/10/18 04:53pm Link  |  Quote  |  Print  |  Notify Moderator

MrWizard wrote:

parallel 12v ?
yes..IF the batteries are low enough SOC
if they are taking everything charger #1 can produce, charger #2 might increase total amps into the batteries

this will increase the amps, but only until the amps drop below what the charger with highest voltage can produce, at that time the lesser charger is doing nothing


To clarify, the second charger is not then necessary, but both chargers could still be doing something. If one's voltage is not far below the other's and both are above the battery voltage, you can have say:

Battery acceptance 40 amps
Charger 1 (60 amper and a tad higher in voltage) and Charger 2 (20 amper) where you are seeing eg, 35 amps plus 5 amps for total of 40.

Charger 2 is still doing some of the amps and Charger 1 is not doing all it could. Yank Charger 2, and now Charger 1's amps jump from 35 to 40.

The amps each does is proportionate to the "spread" between their voltages and the battery voltage. It is not all or none. The lower voltage one will have its amps start to taper first but then you can have both with tapering amps. Two equal 40 ampers would be showing 20 and 20. Pull one and the other jumps from 20 to 40.

One thing to note, if you have a power interruption (gen pops a breaker eg) then to restart the whole thing, you must get the lower voltage charger running again before you start the other or you might not be able to get the lower one going. It can just indicate "full" if the higher voltage one is going.

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Posted: 02/10/18 05:31pm Link  |  Quote  |  Print  |  Notify Moderator

jbeliera wrote:

Here is a technical question. Let's say you want to charge your house batteries on your RV quicker. If you have two 12 volt batteries in your battery bank would you charge that battery bank quicker if you put two 25 amp battery charges on at the same time. Would that be possible to increase charging amps and less charge time or would it fry your batteries

We do this with a pair of smart chargers to reduce ginny run time. Once you reach about 80 or 90 % charge won't make a lot of difference.


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