Rerouting Converter Connection

Ok, but all converters do that as their "loaded voltage" That 1.1v drop mentioned is another thing, related to amps of course. To get your 80 amps #4 should do it if the route is short but 12 ft is way too long for that, so IMO go fatter. The #4 will be safe but IMO you will not see the 80 amps. (You will probably only see 75 anyway with the PD the way they work, so you might not get much better with fatter than #4--hard to know what is "worth it" --we are talking about gen time doing 50-90s and differences in under half an hour, maybe 15 minutes--)

Not clear why to do this at all if the batts are not to be allowed to go low. Off grid you do 50-90s fast charging with highest amps you can make. In that case the rewiring makes sense. If not off grid, you are not doing 50-90s and have no need for fast charging (not using a gen, so can be recharged in slow time) So why rewire?

So you only need to do this job if you are planning to let the batteries go low to 50% as a regular routine.

BFL13 wrote:
PT's post seems mixed up to me.

I understand what he is saying. Under heavy load, the PD converter does sag a few tenths of a volt from rated output. I try not to let the batteries get that low very often.

Drew,

Good point. I hadn't taken that into consideration when I thought about the indicator light. Was just thinking about the lights that show when a fuse is blown, but that is full 12V.

Don,

If I measure the voltage at the converter terminals and then at the battery terminals, there is a 1.1V difference when the batteries are low. That has to be due to the length of the wire and possibly some resistance in the disconnect contacts. Can go with a bigger wire if #4 is not sufficient. Using a PD9280 converter.

STBRetired wrote:
Been thinking about rerouting the 12V output connection of my PDI 80 amp converter to reduce voltage drop when in boost mode.

Current configuration:
Converter (rear of coach) -> 12V Power Panel (rear of coach) -> Battery Disconnect (front of coach) -> Batteries (rear of coach)

I intend to route new cables from the Converter directly to the Batteries with an 80 amp breaker (or fuse if I cannot source a self resetting breaker). This would reduce the length of the run fro the Converter to the batteries from about 65 feet to about 12 feet. Figure some number 4 ought to do it.

Am I setting myself up for any pitfalls by not running the Converter through the disconnect?

Not clear, but you do want to rewire from converter to power panel to battery not straight to the battery, by-passing the panel.

The 12v items that are run from the battery direct would still work AFAIK, because they do not use that existing path from panel to disconnect switch

If you are also wiring in a big inverter near the batteries you can share wires with the converter. A big amp ANL fuse is an option for the shared pos wire near (or on) the pos battery post.

EDIT--PT's post seems mixed up to me.

pianotuna wrote:
PD converters are famous for not being able to maintain voltage in boost mode, if the battery bank is hungry.

Even my Magnum charger with rather large wire and a 3 foot run shows voltage drop when the jars are low.

of course they would show lower voltage if the battery's are low, you either charge by current or voltage.

if the charger is maxed out current wise and is limiting the amperage, then the voltage will not rise until the battery's fall under the current being limited. once the voltage limit is reached, current will keep reducing.

wouldn't matter if you use a wire the size of a telephone poll. i never had trouble getting my 9245 to run at 45+ amps when the battery's were low

PD converters are famous for not being able to maintain voltage in boost mode, if the battery bank is hungry.

Even my Magnum charger with rather large wire and a 3 foot run shows voltage drop when the jars are low.

STBRetired wrote:

Thanks for the suggestion on the Bussmann Hi-Amp. Think I will wire an indicator light across it so that I will notice that it is tripped before the batteries don't get charged.

I don't think this trick will work all that well in this situation because there won't be much of a voltage difference across the tripped breaker to light the lamp. It works for fuses on (most) circuits because the other side is effectively grounded, at least with the high impedance a little LED has in the circuit. In your case, you have a difference of maybe 1.5 or 2V, if the battery isn't already well on its way to being very much discharged, which may not even be above the forward voltage of the LED depending on what color/type you choose (and, even if it is, will not put enough current through a sensible dropping resistor to light it very brightly).

Better in my opinion would be to install a little panel voltmeter monitoring the battery voltage. Besides giving a good indication of whether or not it's charging from the converter, it can also give somewhat of a clue as to its state of charge, etc.

There are other circuits that are branched off in the disconnect cabinet, like the steps, and the propane detecter. Will not be abandoning the old run to the front, just running new cable to the batteries.

Thanks for the suggestion on the Bussmann Hi-Amp. Think I will wire an indicator light across it so that I will notice that it is tripped before the batteries don't get charged.

No problems, and it sounds like an excellent plan to me. In fact, the converter was factory wired on the battery side of the disconnect on my motorhome.

It does mean that, with the disconnect switch off, you won't be able to run the 12V items in the coach from the converter...but of course you will have the batteries charge from it.

Excellent plan. Although I would use a 100 amp manually reset breaker such as Bussmann Hi-Amp (amazon).

If that is a direct feed cut-off switch (no branch connections) I would be tempted to just abandon the whole circuit and go direct. Put the switch/relay close to the battery as well.