Help with dc 2 dc charger

[barnhill910]

Im in the process of setting up my dual battery system on my camper trailer and i need help with a dc to dc charger with a mppt solar input. I found a couple that would work but they are all from Australia and shipping would be expensive. One of the main ones i found that will work is the ePower 30A DC to DC Charger - Enerdrive EN3DC30. The main limitation on all the ones I found are the the voltage for the solar input. The panel im running is a 41V 310W panel that i picked up from the 300 acre solar farm we are putting in. The guy running the job hooked me up with 4 of them. Is there any other controllers/chargers that i should look at.

 

[dwh]

You could just split it...a DC to DC charger, say from Sterling, and a separate MPPT unit for the solar, such as Morningstar or Midnite.

 

[barnhill910]

You could just split it...a DC to DC charger, say from Sterling, and a separate MPPT unit for the solar, such as Morningstar or Midnite.

i was thinking about that but i want a all in one system if i can find one for a descent price.

 

[veetee]

From the Specifications I read the input on CH2 (MPPT Solar) is 45V...

 

[dwh]

Couple of drawbacks I see with that unit...

It's either/or. With seperate systems, the battery could be charged by both the alternator and the solar while under weigh.

It's limited to 30a from the alternator. Most alternators these days can put out much more than that. A simple split charge relay might actually get the battery bulked up faster.

Bulking to 14.4v (or whatever), current limited at 30a, then doing that long slow absorb stage...how many will drive enough hours to where the charger actually ever does reach float stage?

 

[DiploStrat]

Assuming ...

that you REALLY need a B2B (many folks, including yours truly) don't, I really like the look of the CTEK D250S/SmartPass combo. It is an integrated setup of a B2B, an intelligent relay, and a small MPPT solar controller.

See more here: http://smartercharger.com/battery-chargers/#CTEK D250S DUAL

Download the manual and read page 20.

This diagram may help:



Basically: (The manual is not clear on what is actually happening.)

-- When you start to charge, closes relay to get as many amps as possible.

-- When charge drops to 20A (the max capacity of the D250S) it opens the relay and the D250S takes over to assure full, high voltage during the absorb stage. (And temperature compensation.)

-- Integrates the solar.

-- Charge complete it uses the relay to assure that the starter battery is charged as well.

Basically, close to the best of both worlds.

 

[darksidecustoms]

I run the CTEK D250S with a 180Ah battery and it works great. Has MPPT too.


Sent from my iPhone using Tapatalk

 

[dwh]

Ctek 250 is limited to, IIRC, 22v on the MPPT input. Won't work with his PV module.

 

[DiploStrat]

Ctek 250 is limited to, IIRC, 22v on the MPPT input. Won't work with his PV module.

You are correct. D250S and SmartPass have an upper voltage limit of 22v.

N.B. My Blue Sky Solar Boost 3024 is rated for PV of up to 57v.

So this brings us back to the original question: Do you really need a B2B? If your vehicle runs at 14v+ and you are willing to invest in proper cables, I would bet that the answer is "no."

 

[barnhill910]

Couple of drawbacks I see with that unit...

It's either/or. With seperate systems, the battery could be charged by both the alternator and the solar while under weigh.

It's limited to 30a from the alternator. Most alternators these days can put out much more than that. A simple split charge relay might actually get the battery bulked up faster.

Bulking to 14.4v (or whatever), current limited at 30a, then doing that long slow absorb stage...how many will drive enough hours to where the charger actually ever does reach float stage?

Im never going to be charging with solar while under weigh the solar is only for when camp is set up. thats why i was looking for a ether or system.

 

[barnhill910]

You are correct. D250S and SmartPass have an upper voltage limit of 22v.

N.B. My Blue Sky Solar Boost 3024 is rated for PV of up to 57v.

So this brings us back to the original question: Do you really need a B2B? If your vehicle runs at 14v+ and you are willing to invest in proper cables, I would bet that the answer is "no."

what size cable are you talking about running i was going to run 4 awg from the dual batt on the jeep to the trailer. Instead of buying the wires i was going to buy a set of 20' jumper cables and use that i can get them for $15 a set.

 

[DiploStrat]

I have a 20 foot run from the front of my truck to the batteries. I use a pair of 1/0 AWG cables. (100mm2). That gets me less than 0.5v drop.

Do the math here:http://www.calculator.net/voltage-d...nce=20&distanceunit=feet&amperes=100&x=79&y=8

20 ft. of 4 AWG @ 14v pushing 100A will give you about 1v of drop. Less at 50A.

What is your charging voltage, what is your distance, and what does your battery manufacturer require?

 

[SparkyDan]

The best part of a dc dc charger is that you dont need to run massive cables all the way to you auxiliary battery. Most of them will produce full charge voltage and current with a voltage input as low as 11 volts, this means cables that are 8-10mm can be run from the main battery to the charger that is mounted with the aux battery and your aux battery will get properly charged.

When we set up house banks in boats and motor homes we work on the charger being no smaller than 10% of the house bank A/h, so a 30amp dc to dc will charge a 300ah bank.
The Enerdrive charger can take up to 45v of solar so this would work really well with the panel you have.