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 > DC-DC Charging ?

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Slownsy

USA

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Posted: 02/20/21 04:56pm Link  |  Quote  |  Print  |  Notify Moderator

BFL13 according to Renogys manual you wil have to instal 6-4 Wire from truck to FW as distance 20-30’
Frank.


Frank
2012 F250 XLT
4x4 Super Cab
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pianotuna

Regina, SK, Canada

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Posted: 02/20/21 05:00pm Link  |  Quote  |  Print  |  Notify Moderator

BFL13,

You convinced me to get one, too! Thanks for finding what, for me, is the right size for the right price.


Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp hours of AGM in two battery banks 12 volt batteries, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

BFL13

Victoria, BC

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Posted: 02/20/21 05:20pm Link  |  Quote  |  Print  |  Notify Moderator

Slownsy wrote:

BFL13 according to Renogys manual you will have to install 6-4 Wire from truck to FW as distance 20-30’
Frank.


Yes, thanks. I will see how it goes first. It is more like 12 ft one way, but the 7-pin charging wires are more like #10 or 12, so amps will suffer. It is a Truck Camper and camper batts are near the front of the truck bed, so closer. I get 15 amps on the 7-pin now to the camper batt (at first, then it tapers)

My purpose is not to get more amps (but that would be nice), but to not have the two types of batteries "mixed", which might not even be an issue either. I just don't want to mix them and that's that.

--PT, what do you want one for? And why not get the 60 amper, or will that overtax your alternator ? (input amps draw being higher than output amps.) Also you said you will have two banks so do you need two?


1. 1991 Oakland 28DB Class C
on Ford E350-460-7.5 Gas EFI
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2. 1991 Bighorn 9.5ft Truck Camper on 2003 Chev 2500HD 6.0 Gas
See Profile for Electronic set-ups for 1. and 2.

theoldwizard1

SE MI

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Posted: 02/20/21 05:35pm Link  |  Quote  |  Print  |  Notify Moderator

BFL13 wrote:

Or is it just charging the house batts, which are isolated from the engine batt being charged from the alternator?

This !

Some have a manual "backfeed" button to charge the vehicle battery if it is lower than the house battery.

theoldwizard1

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Posted: 02/20/21 05:42pm Link  |  Quote  |  Print  |  Notify Moderator

BFL13 wrote:

Yes, thanks. I will see how it goes first. It is more like 12 ft one way, but the 7-pin charging wires are more like #10 or 12, so amps will suffer. It is a Truck Camper and camper batts are near the front of the truck bed, so closer. I get 15 amps on the 7-pin now to the camper batt (at first, then it tapers)

The whole point of a DC-DC charger is NOT HAVE TO WORRY ABOUT VOLTAGE DROP ! The charger should be as close as practical to the house battery. The limiting factor will be the fuse that is powering the 7-pin charge wire.

BFL13 wrote:

My purpose is not to get more amps (but that would be nice), but to not have the two types of batteries "mixed", which might not even be an issue either. I just don't want to mix them and that's that.

This is even MORE important if you are running different battery chemistries.

BFL13

Victoria, BC

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Posted: 02/20/21 06:10pm Link  |  Quote  |  Print  |  Notify Moderator

The Renogy will be within 2 ft (one way) of the house batts. Input 7-pin #4 is fused at 40 amps Stud 1 in the Chev truck under the hood. Output max is 20 amps. We'll see what happens (early March). [emoticon]

They are different chemistries but have the same sort of charging voltage specs. Don't care--I still don't want to mix them.

pianotuna

Regina, SK, Canada

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Posted: 02/20/21 06:43pm Link  |  Quote  |  Print  |  Notify Moderator

Hi BFL13,

I got the 20 amp because the alternator is only 130.

My charging paths are both equipped with automatic 50 amp circuit breakers.

I have bank switching so it is easy to switch from one bank to the other, so no need for two dc to DC chargers.

* This post was edited 02/20/21 06:58pm by pianotuna *

MEXICOWANDERER

las peñas, michoacan, mexico

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Posted: 02/20/21 07:01pm Link  |  Quote  |  Print  |  Notify Moderator

Gdetrailer wrote:

DC to DC converter should be a "one way" device but to ensure it is..

Insert a Schottky Diode in front of the DC to DC converter to ensure your vehicle battery and charging system are not going to damage your house batteries.

[image]

Read HERE

"Low Forward Voltage Drop

One of the chief characteristics Schottky diodes are known for are their low forward voltage drops.


One note of interest although my 500 ampere dual schottky rectifier needs an isolated heat sink, it passes 166 amperes at vf .304 showing .214 quiescent. I used it on the BORG to insure absolute isolation protection of reversed polarity connection.

Their low forward voltage drops means that they consume less voltage than a typical diode.

A typical silicon diode consumes about 0.7V across its junction.

A typical schottky diode may consume only 0.3-0.4V across its junctions. Thus, it saves about 300mV of power. "


[image]

5 pack of 40A Schottky diodes HERE for $9

Those actually are a "dual diode" package, contains two diodes that you can parallel if you like..


BFL13

Victoria, BC

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Posted: 02/20/21 07:05pm Link  |  Quote  |  Print  |  Notify Moderator

My 1991 C's alternator is fairly lame. They got new ones in the 1992s.

With alternator charging in the C as is, I get 30 some amps at first and then it settles around 20 amps. So no point in using a 20 amp DC-DC in mine to get more amps. Also house and engine batts are all FLA no mixing worries.

When there is solar, it has a bit more voltage than from the alternator so that cuts back amps from the alternator.

With the Renogy, I suppose I can dial the solar voltage to match more closely so they add their amps better than they do now. Haven't checked to see if the Renogy has adjustable output voltage--I think so. Then I could dial them both to 14.6 battery spec and they will add their amps better.

BFL13

Victoria, BC

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Posted: 02/20/21 08:04pm Link  |  Quote  |  Print  |  Notify Moderator

So it wants a wire to the ignition circuit to turn the unit ON, but the unit will be back in the camper. It says any 12v source will do though, so I will connect that wire to the house.

I can leave the 7-pin plugged in with the always live Chev input and put a switch on the "ignition" wire from the house to turn the unit on and off.

"The DC-DC will not power on or operate until the D+ ignition cable is connected to the ignition
circuit where it will detect a 12V source to operate ON. The purpose is to toggle the DC-DC
switch on when the vehicle is running with the alternator to prevent the DC-DC from operating
incorrectly with just the starter battery leaving you with a drained starter battery."

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