Progressive Dynamics - max current before overload

[JamesJudasPries]

Hello all,

I am trying to figure out what the max power output of a PD 9145 converter is before its brain decides there is an overload condition- and also, what it does to solve that.

through my experimentation, I have attached short chunks of #4 wire with lugs directly to my 2 golf cart batteries, brand new, discharged to about 50%. With my DC clamp meter, I measured 47 amps @ 12.6 volts when i plugged in the converter to an ac outlet. The charge wizard pendant had also been installed on the unit.

My question is, just how low will the converter output voltage get in order to control current to the max 45 amp output. The paperwork says the converter's full load current is rated at 45 amps and about 12.6 volts. I understand the fact that at the batteries state of charge rises, so will the converter voltage until max 14.4 is reached at full current, and then the battery demand will taper.

So what if someone has maybe 4 or six golf carts which will demand significantly more than 45 amps if heavily discharged? surely the converter would have to drop to maybe even 12.0 volts or lower to control the charge current from climbing past max output. Would the PD9145 simply consider this overload condition if the batteries demanded too much current at a voltage below the 12.6 min spec? And does the converter shut off completely at this point?

[time2roll]

Just saying you could put a big fat variable resistor across the PD40 and crank the voltage down to 10 volts and it would hum along putting out 40 amps all day.

If the battery starts fully dead at 10.5 volts the voltage will only rise from there.

You may not even get 40 amps through 4x GC2 when fully dead because the resistance is so high.

Lots of time I had a dead battery come into the shop for a charge. I think the shop charger was about 60 or 80 amps with several steps from 13.4 to 15.6 volts. I would crank it all the way up and get maybe 5 amps on the gauge. Then after some time the amps would actually increase as the resistance dropped faster than the voltage potential climbed. Once it got close to 50% charged it would start acting like a normal battery. I would tell the customer if they ran it down like this again he would be buying a new battery.

[JamesJudasPries]

Of course that is true about a charging source having to be higher than the batteries open circuit voltage. I think if you have 400 amp hours or more worth of heavily discharged batteries sitting at say 11 volts, even if the charging voltage is 11.5v a mere half volt above the batteries, that might still cause a fair amount of current to flow. Obviously this might only be for a few minutes, and then the charger will have to constantly raise voltage.

[BFL13]

smkettner wrote:

JamesJudasPriest wrote:
ok, so the answer must be that the converter output voltage will drop as low as necessary to control the current. How else could it perfectly dial in 45 amp output into very thirsty batteries?

Typically the drop will not be below 10.5 volts.
Even a large and very low battery does not create a dead short.

Smk is being very mysterious here. If the converter output voltage is equal to or less than the battery voltage no current will flow at all!

The fact is , the converter voltage stays above the battery voltage the whole time as the battery voltage rises to Vabs, and then holds steady just above battery voltage while amps then taper.

[JamesJudasPries]

Smkettner I think you nailed it

[time2roll]

JamesJudasPriest wrote:
ok, so the answer must be that the converter output voltage will drop as low as necessary to control the current. How else could it perfectly dial in 45 amp output into very thirsty batteries?

Typically the drop will not be below 10.5 volts.
Even a large and very low battery does not create a dead short.

[BFL13]

JamesJudasPriest wrote:
ok, so the answer must be that the converter output voltage will drop as low as necessary to control the current. How else could it perfectly dial in 45 amp output into very thirsty batteries?

The converter's voltage stays higher than the battery's voltage as the battery's voltage rises. during this time (Bulk stage) the charger is "current limited" or else its current would go higher than 45.

When the battery voltage reaches near 14.4, which is now held constant, the battery itself will regulate the amps by the way its "acceptance rate" in amps falls as the battery's state of charge rises. That is your tapering amps during the Absorption stage.

See these charge profiles: scroll down to graphs

http://pdf.wholesalesolar.com/battery-folder/charging_instruction_2011_2.pdf

[JamesJudasPries]

ok, so the answer must be that the converter output voltage will drop as low as necessary to control the current. How else could it perfectly dial in 45 amp output into very thirsty batteries?

[pianotuna]

My 9100 PD9140A does a maximum of about 37 amps. I've often used it in a double conversion mode when the "load" is well over 100 amps.

It does not struggle to recharge the 875 amp-hour battery bank, it simply takes longer. It is wizard equipped.

[doughere]

I had a PD9245 (replaced with a 9260), and no matter how low my 2 GC's were, it never put out more than 40 to 45 Amps.

My experience with both the 9245 and 9260 is pretty much like RoyB above.

The 9245-60 don't care what your batteries would like / could take, it just puts out its all and then starts tapering back as the demand lowers. I wouldn't be surprised (but I sure as heck don't intend to try it !!) if you put a dead short on the units it would probably just output 45 or 60 amps.

Doug

[BFL13]

The converter has a max power and that's it. It does not "overload".

Within that max power, you get its rated amps at the spec voltage which in the PD's case is 13.6 volts. It will have some extra power so you will get more at the start, but the PD has some circuitry thing where it can't quite hold 45 amps at 14.4 volts so it tapers the amps a bit at the start in 14.4v mode. some other converters and chargers can hold their rated amps steady "constant current" until the battery reaches the set absorption voltage. then amps will taper once voltage is held constant in that stage.

The exact way it all happens for different chargers is called their "charging profiles" and those vary among brands somewhat.

The PD and the other brand converters will do a little more amps than the "name" size. Eg my 7355 will do 56 amps, my old Paramode 55 did 60, and my PowerMax 100 does 103 given low resistance paths to the battery.

So don't worry how many batteries you are trying to charge. As was noted earlier in the thread, it will do 45ish amps max no matter how big the battery bank is.

EDIT--RJ, the 60 amp load will be on the battery not the 45 amp converter, so all that happens is your battery will get 45 amps in while that 60 amp load is running for a net loss of 15 amps. Nothing will break.

[RJsfishin]

Batteries do not demand current. Batteries accept current, and only if it is available to them.
You can have a hundred 1/2 dead batteries, and the 45 amp PD will just take 100 days to charge them at 45 amp max.

Now if you get into a demand situation, like dumping a 60 amp load on a 45 amp converter, well,.... just don't do it, ok,....because something is going to break,.....and I'm not sure what.

[RoyB]

I am using a P9260C 60AMP Converter/Charger here and have two banks of GP24 12VC Interstate 85AH batteries, One battery bank only has one working 12VDC Battery in it.

I will run down my batteries to around 12.0VDC over night and when I first fire up my generator running the PD9260C Converter/charger I will see 14.4VDC on my BATTERY MONITOR PANEL reading both selected battery banks and my DC CURRENT meter is reading around 53-54 DC AMP. This is telling me my selected batteries are demanding around 18AMP DC current each when first hit with 14.4VDC.

This sets in this mode for two hours showing 14.4VDC and DC current starts tapering off after around 15 minutes. The DC current slowly tapers back to around 8AMP DC CURRENT in the two hour period.

After two hours the PD9260C switches to 13.6VDC and the DC current drops to around 6AMPs DC. It will remain in this mode for about an hour and then gets to it 90% charge state.

If no current drain is being detected from the trailer side then the PD9260C will drop back to 13.2VDC but as soon as current start being drawn then the PD9260C will revert back to it 13.6VDC mode.

This is basically what I see each morning on my battery monitor panel when camping off the battery banks.

Pretty much follows the battery charging chart shown in the PD9260C manual.

Roy Ken

[Roadpilot]

I don't know about the PD 9145, but battery chargers in general are current sources, not voltage sources. They output a fixed current. As the voltage rises, they'll sense that and then begin to taper off the current until it's fully charged. They may then switch to a constant voltage mode to maintain a float voltage.

So with more batteries, the current would stay fixed at 45 amps, but it would take longer for batteries to charge.

[time2roll]

Great question. I have not seen an answer. I have also never read a issue of a smallish converter overloading and shutting down even with a large battery that needs significant charging.

Reality is that as you go below 50% the internal resistance of the battery is climbing fast so the demand does not increase as much as you may think. If you would to get 90% discharged you may not even get 45 amps into the batteries.

I can say my 35 amp WFCO will charge my 4x GC2 just fine from 50% and even less.