Cable Requirements for PD4655 Converter
I have the infamous WFCO 8955 converter in my toy hauler. Considering upgrading to a PD4655 to reduce my battery charge times. I have approx. 8-10 feet of 6 gauge cable that runs from my battery...
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I used 1/0 cable and moved my PD9280 to within 3' of the batteries. 1/0 is the largest wire that will fit the dual terminals of the PD9280 when you split it into two bundles and feed both into the terminal pair at the PD9280 output (one pair is provided for positive and one pair for negative).
When you start charging below about 80% state of charge, you should get the full amperage output of your charger. If the cable is small, there will be some voltage drop, so the charger will see the battery voltage plus the voltage drop on the cable and think that's the battery voltage. It's no problem at this point because the charger will simply increase the amperage up to its limit as long as the sum of the cable voltage drop plus the battery voltage is below the charger output voltage.
However, as the battery voltage rises, there will come a point where the sum of those two is equal to the output voltage of the charger. Now the charger can't increase its output voltage any more, so it begins cutting back the charge current. The longer your charge cables, and the thinner they are, the sooner this cutback happens. You now face longer charge times, since the charge current is reduced.
Some people don't care. They are plugged in 24 hours. Others have solar and don't have high charge rates anyway. But if you are boondocking and need to charge with a gen, as I do, this decreased rate is a real problem. There are two solutions. One is to buy a remote sensing charger. It will sense the true battery voltage, not the battery voltage plus the voltage drop through the cables. This is an excellent solution, but can be expensive. The other solution is to reduce the resistance of the cables. Short and fat is a simple solution if you can get it to work for you. I would have used 4/0 charge cables if they would have fit. :)
When you start charging below about 80% state of charge, you should get the full amperage output of your charger. If the cable is small, there will be some voltage drop, so the charger will see the battery voltage plus the voltage drop on the cable and think that's the battery voltage. It's no problem at this point because the charger will simply increase the amperage up to its limit as long as the sum of the cable voltage drop plus the battery voltage is below the charger output voltage.
However, as the battery voltage rises, there will come a point where the sum of those two is equal to the output voltage of the charger. Now the charger can't increase its output voltage any more, so it begins cutting back the charge current. The longer your charge cables, and the thinner they are, the sooner this cutback happens. You now face longer charge times, since the charge current is reduced.
Some people don't care. They are plugged in 24 hours. Others have solar and don't have high charge rates anyway. But if you are boondocking and need to charge with a gen, as I do, this decreased rate is a real problem. There are two solutions. One is to buy a remote sensing charger. It will sense the true battery voltage, not the battery voltage plus the voltage drop through the cables. This is an excellent solution, but can be expensive. The other solution is to reduce the resistance of the cables. Short and fat is a simple solution if you can get it to work for you. I would have used 4/0 charge cables if they would have fit. :)
