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 > Lance TC - lithium - DC-DC charger question

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otrfun

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Posted: 05/18/22 06:46pm Link  |  Quote  |  Print  |  Notify Moderator

mbloof wrote:

BFL13 wrote:

Another factor is to keep the input voltage high enough so the DC-DC buck/boost converter can maintain the set output amps and voltage to the camper battery. This is a separate issue from fusing the input side for its wire size, and having the input wire gauge match the input amps.
I think your on the right track here.

For camper applications, we have the wiring of the truck, then the connector(s), pigtail and then the wiring in the camper itself.

I swear my 97 Ford had 18AWG wiring! I tapped the output of the alternator and ran to a solenoid (switched on with the engine running) and 6AWG to ~1' of the 7Pin and then spliced in as large of a AWG wire as I could fit. The ground went from the 7Pin to the trucks frame.

At least Lances have 8AWG wire in their pigtails, a quick look at the wire sizes used in most 7Pin cables is 14AWG. [emoticon] My NL uses 10AWG to go to the battery.

Lets face it, all wire has resistance and higher currents will create higher voltage drops. Depending on efficiency of the step up charger/converter itself (which BTW 'stepping up' a voltage is difficult to do with anything resembling 'efficient') it could be easily trying to draw 50-60A on the input.

However, given the wiring in the camper itself (and the batteries state of charge) the battery may never see 40A of charge current. For example I recently viewed the charge current at the battery after a 2-day trip that the PD6045Li I have in my NL was providing when I got home. ~19A at the battery. [emoticon]

Personally I'm debating getting a 20A or 40A model myself. I do know that some of them have a switch/configuration option to operate at 1/2 power. [emoticon]

- Mark0
NL used 15-20 ft. of 10 gauge wire for the battery to converter run on our 8-11, too. Like you we got less than 20a of charge current from our 45a PD converter. We replaced the 10 gauge with 2/0 (now get a full 45a). Used 2/0 'cause we sometimes quick charge our lifepo4 using both our 45a converter and 40a dc2dc charger at the same time (85a of total charge current). FWIW, we used a 25 ft run of 2 gauge cable from our truck's battery to the 40a dc2dc charger mounted inside the TC. 43.5a alternator/battery load with 40a of charge current.

orourkmw

Port Allen, LA USA

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Posted: 05/18/22 06:54pm Link  |  Quote  |  Print  |  Notify Moderator

What kind of connection did you use on the 2 gauge between the truck and camper.

otrfun

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Posted: 05/18/22 07:48pm Link  |  Quote  |  Print  |  Notify Moderator

orourkmw wrote:

What kind of connection did you use on the 2 gauge between the truck and camper.
175a, 2-gauge Anderson-type connectors.


mbloof

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Posted: 05/18/22 09:05pm Link  |  Quote  |  Print  |  Notify Moderator

otrfun wrote:

mbloof wrote:

BFL13 wrote:

Another factor is to keep the input voltage high enough so the DC-DC buck/boost converter can maintain the set output amps and voltage to the camper battery. This is a separate issue from fusing the input side for its wire size, and having the input wire gauge match the input amps.
I think your on the right track here.

For camper applications, we have the wiring of the truck, then the connector(s), pigtail and then the wiring in the camper itself.

I swear my 97 Ford had 18AWG wiring! I tapped the output of the alternator and ran to a solenoid (switched on with the engine running) and 6AWG to ~1' of the 7Pin and then spliced in as large of a AWG wire as I could fit. The ground went from the 7Pin to the trucks frame.

At least Lances have 8AWG wire in their pigtails, a quick look at the wire sizes used in most 7Pin cables is 14AWG. [emoticon] My NL uses 10AWG to go to the battery.

Lets face it, all wire has resistance and higher currents will create higher voltage drops. Depending on efficiency of the step up charger/converter itself (which BTW 'stepping up' a voltage is difficult to do with anything resembling 'efficient') it could be easily trying to draw 50-60A on the input.

However, given the wiring in the camper itself (and the batteries state of charge) the battery may never see 40A of charge current. For example I recently viewed the charge current at the battery after a 2-day trip that the PD6045Li I have in my NL was providing when I got home. ~19A at the battery. [emoticon]

Personally I'm debating getting a 20A or 40A model myself. I do know that some of them have a switch/configuration option to operate at 1/2 power. [emoticon]

- Mark0
NL used 15-20 ft. of 10 gauge wire for the battery to converter run on our 8-11, too. Like you we got less than 20a of charge current from our 45a PD converter. We replaced the 10 gauge with 2/0 (now get a full 45a). Used 2/0 'cause we sometimes quick charge our lifepo4 using both our 45a converter and 40a dc2dc charger at the same time (85a of total charge current). FWIW, we used a 25 ft run of 2 gauge cable from our truck's battery to the 40a dc2dc charger mounted inside the TC. 43.5a alternator/battery load with 40a of charge current.


I've heard of others rewiring from the converter/charger to the batteries with similar results.

Personally, I'm just looking for a 'fail safe' of sorts. If/when it might happen that I'm low on juice and digging the Yamaha out is not convenient, three button presses on the Trucks remote could not be easier. [emoticon]


- Mark0.

JoeChiOhki

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Posted: 05/19/22 09:35am Link  |  Quote  |  Print  |  Notify Moderator

This stuff has gotten so complicated in the last ten years or so.

In the olden days, we just put a 90amp self-resetting marine breaker on the firewall on the line coming back to our 100amp rated Lift Gate Plugs for our charging umbilical between the truck and camper with 4 or 2 gauge wire all the way back and connected to our big banks of batteries.


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Posted: 05/19/22 10:59am Link  |  Quote  |  Print  |  Notify Moderator

Quote:

This stuff has gotten so complicated in the last ten years or so.


It has,huh..

I just cut the charge wire from the truck to the camper..everything works except it won't charge off the alternator..I charge off of solar...Besides getting complicated,if you buy all the odds and ends and gadgets,it really adds up for lithium...


Lifepo4-380ah/Lithium NMC-140ah/Solar-400 watts/Wagan & Giandel PSW/Engel & Iceco 3-1 compressor fridge freezer/5K Window AC/Honda 2K

BFL13

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Posted: 05/19/22 01:22pm Link  |  Quote  |  Print  |  Notify Moderator

"I've heard of others rewiring from the converter/charger to the batteries with similar results.

Personally, I'm just looking for a 'fail safe' of sorts. If/when it might happen that I'm low on juice and digging the Yamaha out is not convenient,"

Some more notes on our camper set up

Can't carry a gen with the truck camper set up we have, so the DC-DC and truck engine is the gen and charger if solar can't keep up.

For the pos 12v to the DC-DC I by-passed the 7-pin connector that goes into the camper at the front of the truck bed, and have that wire with my by- pass wire added to it with a wire nut going inside the camper to the DC-DC. The wire nut is for when the camper is off the truck have to undo that plus pull the 7-pin. The neg to truck bed also comes off.
Proper connectors you can undo and do up would be better of course.

I have the 20 amp Renogy DC-DC and it does 20 amps to the camper batts according to my battery monitor. Way more amps than the 7-pin ever did.

Left campground with batts at 52% and thanks to DC-DC and some solar, it was 82% on arrival back home for about a two and a half hour drive. Way better than 7-pin!

Another advantage to the DC-DC is you can set the voltage to match the voltage of the solar controller so they add their amps. EG the other day with low batts and no solar in the woods, drove to a place in the open mid-day, and was getting 12.2a solar and 20 from the DC-DC measured one at a time and with both on monitor showed total 30.2 amps

( With the Class C alternator charging is at a lower voltage than its solar is set at, so they do not add all their amps. Eg, if solar is 15 amps by itself and alternator is 25 amps (small alternator in our C) you might see 32 amps instead of 40 )

With the truck engine off, if I forget to turn off the DC-DC it still does about 14 amps from the truck battery. Goes back to 20 when the truck is turned on. Oops, it is a Chev, no isolator, I must remember to go back into the camper and turn the DC-DC off. Easy to forget if you stop to go into a store, or worse go off for a longer time.

The DC-DC isolates the truck batt from the camper batt, but it does not isolate the camper from the truck unless you have a Ford. I could put an isolator in the camper somehow as others have--might save me someday.


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orourkmw

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Posted: 05/19/22 01:37pm Link  |  Quote  |  Print  |  Notify Moderator

BFL13: what is the size of your “bypass wire” that carries the current to the DC-DC?

BFL13

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Posted: 05/19/22 03:16pm Link  |  Quote  |  Print  |  Notify Moderator

orourkmw wrote:

BFL13: what is the size of your “bypass wire” that carries the current to the DC-DC?


I got into the wires for the 7-pin for the camper that comes up between the cab and the box and dug out the 12v wire before it gets to the truck's 7-pin connector. That wire is maybe #10 or even #12 not sure.

I then added on a length about 1 foot of #8 to come out of the wrapped cord and have another maybe 3 feet of # 8 wire-nutted to that and going up into the camper and onto the DC-DC input. I have a fatter wire for the neg on the DC-DC input that comes down and its end is jammed under the aluminum rail cap which makes it truck frame grounded.

I will try for a photo here of the ugly mess. If I ever get the ambition, I can do it properly someday.

">][image]

I drilled a new hole beside the camper's 7-pin up under there for the pos and neg (to frame) wires. The battery box is in the front driver's side of the camper so it is all together in that front corner.

The 7-pins have no 12v pin 4 at all now. No brake line either--so it is sort of 5 pins [emoticon]

Note the other 7-pin at the back bumper is not affected by all this

Now I am thinking that wire nut on the red wires there could act as my isolator instead of going back to the camper to turn it off when we stop somewhere. The little B+ on/off wire goes to that red input wire.

* This post was last edited 05/19/22 03:37pm by BFL13 *   View edit history

time2roll

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Posted: 05/19/22 07:19pm Link  |  Quote  |  Print  |  Notify Moderator

JoeChiOhki wrote:

This stuff has gotten so complicated in the last ten years or so.

In the olden days, we just put a 90amp self-resetting marine breaker on the firewall on the line coming back to our 100amp rated Lift Gate Plugs for our charging umbilical between the truck and camper with 4 or 2 gauge wire all the way back and connected to our big banks of batteries.
I use the existing system. Works fine. No complications.


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