DC-DC charger (B2B) options and general discussion

[MarkF]

I have the Victron Orion-TR Smart (Isolated) in my Wrangler and love it. Between the Bluetooth and the auto sense ignition it's worth the premium price. If anybody has questions, let me know.

I got my 272 CATL battery built and a Victron Orion tr smart 12-12 30 installed in my RV. I went with 2 awg battery positive cable and a chassis ground in my 2016 Honda Pilot due to the combined length of run of the Pilot/RV. It’s all working well and thanks for the assistance kennedyma!

I’ll be leaving the 7 pin 12v fuse in place but still wondering if it’s better to remove it for possible backfeeding of the Orion voltage to the Pilot…

 

[DerpsyDoodler]

Hi, I am looking for opinions on this dc-dc converter. I am thinking 2 in parallel with a battery isolator will do the trick. All I can seem to find is 20-30a 24v dc-dc chargers for upwards $350. I want at least 50a charging from my busses' alternator. To get that, id have to spend almost $1000. My entire solar system barely cost that much (not including batteries).

Note that it is not isolated, but I am using a common chassis ground between the house and chassis battery systems, so I shouldnt have to worry about ground loops or galvanic corrosion of the chassis. Any input appreciated.

 

[DerpsyDoodler]

I need y'all to review my plan to charge my 24V house bank for $18USD.

Dasiter 600W High Power DC to DC Boost Converter DC 12-60V to 12-80V Boost Module Board Step-up Transformer

I have been pulling a travel trailer with a van. It is a 30A trailer. One way to describe my rig is a split 'B'.
Where most rigs have all of the electrical in the trailer, the van is my main source of VAC for the trailer.

This plan was started when my 12V inverter/charger in the van went toes up. Right now, the 600AH bank is being charged by solar and the alternator. There is a 6Ga positive cable with a 25A in-line fuse between the starting and house bank with a chassis ground return, very parallel. The current is between 20 and 25A because I blew a 20A fuse but the 25A has held up. I don't want to lose this charging source.

I am changing to a 24V house system with a Growatt 3000 24V AIO. The AIO will replace the existing SCC and Inverter/charger. The 12V, 600AH bank will be rewired to 24V, 300AH.

Defs:
House - the 24V 300AH AGM bank.

SCC - A 15A limited 24V MPPT with max 400W input draw. VOC = 60V. It will ignore excess Amps/Watts. I have this.

Boost - the $18 device I need in the link above. What I need this device to do is present a psuedo 400W(12A * 33V) panel to the SCC.

BIRD - Bidirectional, Voltage sensing relay. I have this.

The flow :
House <- SCC <- Boost <- BIRD <- alternator.

Can the Boost's Volt and Amp pots do this?
Will I have ground issues?

This seems reasonable, but why do you need the scc? all it takes to charge lithium is cc cv.

You mention "chassis ground return." Are you saying you're using the chassis as part of the circuit? I highly discourage this. It will inevitably cause galvanic corrosion and will weaken the chassis. Using the chassis as a subsitute earth ground (safety ground) is a different story. It is not normally energized with current.
What you want to do (if your dc dc charger/converter isnt galvanically isolated between its inputs and outputs) is to make sure the the house and chassis battery systems have a common grounding point on the chassis. this will keep any ground loops from forming through the chassis.

There is a nice resource on grounding in the resources section of the forum. i suggest going through it.

In fact, take a look at the converter i posted above this response.

 

[Zwy]

Hi, I am looking for opinions on this dc-dc converter. I am thinking 2 in parallel with a battery isolator will do the trick. All I can seem to find is 20-30a 24v dc-dc chargers for upwards $350. I want at least 50a charging from my busses' alternator. To get that, id have to spend almost $1000. My entire solar system barely cost that much (not including batteries).

Note that it is not isolated, but I am using a common chassis ground between the house and chassis battery systems, so I shouldnt have to worry about ground loops or galvanic corrosion of the chassis. Any input appreciated.

I have over 125a easily usable (105a and 250a alternators) at 12V I'm looking to get to my 24V LFP battery. I'm considering just using a 2000w inverter and just running a 10 ga cord back with locking connectors. Then a battery charger at the end or the Growatt AC input and do 60a of charging thru it.

Solves 2 problems, one voltage drop and two, I don't need another charger. And if the GW were to somehow fail me, I could still run off the other inverter with the truck running.

 

[DerpsyDoodler]

I have over 125a easily usable (105a and 250a alternators) at 12V I'm looking to get to my 24V LFP battery. I'm considering just using a 2000w inverter and just running a 10 ga cord back with locking connectors. Then a battery charger at the end or the Growatt AC input and do 60a of charging thru it.

Solves 2 problems, one voltage drop and two, I don't need another charger. And if the GW were to somehow fail me, I could still run off the other inverter with the truck running.

well...you don't need another charger because youve replaced it with a second inverter lol.

I dont want another inverter to fuse, wire, ground, and....worry about disconnecting from chassis when the coach is shut off. Im going to get a battery isolator anyway, but why spend bucks on another 2kw inverter when 2 of the dc dc converters i posted is $70 and gives me 60a regulated @24v? that said, i don't have a high throughput ac/dc charger, anyway. i have 2x 10a power supplies.

Also, its worth noting that the devices i posted are not isolated. so beware if considering using them.

 

[Zwy]

At the minimum, I would derate those devices you linked to 50% capacity, maybe even less.

 

[Short_Shot]

I got my 272 CATL battery built and a Victron Orion tr smart 12-12 30 installed in my RV. I went with 2 awg battery positive cable and a chassis ground in my 2016 Honda Pilot due to the combined length of run of the Pilot/RV. It’s all working well and thanks for the assistance kennedyma!

I’ll be leaving the 7 pin 12v fuse in place but still wondering if it’s better to remove it for possible backfeeding of the Orion voltage to the Pilot…

I would pull that fuse as long as nothing else needs it.

Depending on the vehicle's charging system you might actually experience some issues if it has a smart alternator setup. These intentionally cut the charging voltage, and thus current, to save fuel.

Some vehicles may attempt to do this, see higher than expected voltage coming back, and not know what to do with it (if it actively monitors this that is).

Oh and if you for sure don't have a smart alt, then I'd still pull it so you don't have the alternator trying to shove 14+ volts into your lithium, even if it's really low current.

 

[DerpsyDoodler]

At the minimum, I would derate those devices you linked to 50% capacity, maybe even less.

50% or less? why do you say that? do you see something on the boards that leads you to believe I should, or is it rule of thumb thinking that you're encouraging?

 

[gelmjw]

This seems reasonable, but why do you need the scc? all it takes to charge lithium is cc cv.

You mention "chassis ground return." Are you saying you're using the chassis as part of the circuit? I highly discourage this. It will inevitably cause galvanic corrosion and will weaken the chassis. Using the chassis as a subsitute earth ground (safety ground) is a different story. It is not normally energized with current.
What you want to do (if your dc dc charger/converter isnt galvanically isolated between its inputs and outputs) is to make sure the the house and chassis battery systems have a common grounding point on the chassis. this will keep any ground loops from forming through the chassis.

There is a nice resource on grounding in the resources section of the forum. i suggest going through it.

In fact, take a look at the converter i posted above this response.

I appreciate the info. I did, in fact, have some kind of ground issue with the circuit to the chassis battery. I was getting about 6VDC where I wanted 13.1V.
I am using an MPPT SCC to step down from the 24V bank to the 12V chassis. The neg wire from the SCC to the frame was not making good contact. I replaced the ring terminal, scrubbed the frame with a wire brush, and drove a new self-tapping screw into the frame. The SCC now holds the chassis battery at 13.1V.
I can now see where it would be correct to run a neg line between the chassis battery negative along side of the positive.

 

[DerpsyDoodler]

I appreciate the info. I did, in fact, have some kind of ground issue with the circuit to the chassis battery. I was getting about 6VDC where I wanted 13.1V.
I am using an MPPT SCC to step down from the 24V bank to the 12V chassis. The neg wire from the SCC to the frame was not making good contact. I replaced the ring terminal, scrubbed the frame with a wire brush, and drove a new self-tapping screw into the frame. The SCC now holds the chassis battery at 13.1V.
I can now see where it would be correct to run a neg line between the chassis battery negative along side of the positive.

I'm confused now. Why do you need the scc to charge the chassis battery? I thought your goal was to tap into the chassis alternator system to charge your house batteries.

 

[MarkF]

I would pull that fuse as long as nothing else needs it.

Depending on the vehicle's charging system you might actually experience some issues if it has a smart alternator setup. These intentionally cut the charging voltage, and thus current, to save fuel.

Some vehicles may attempt to do this, see higher than expected voltage coming back, and not know what to do with it (if it actively monitors this that is).

Oh and if you for sure don't have a smart alt, then I'd still pull it so you don't have the alternator trying to shove 14+ volts into your lithium, even if it's really low current.

Well short_shot, you were right!
Update on the Orion TR smart dc charger on the subject of back feeding to the tow vehicle, a 2016 Honda Pilot with an “all to smart” alternator…the unit ran fine in “the driveway test” but as soon as I got on the road it wouldn’t charge.

unfortunately the unit is in a metal tub so I can only monitor it via the killer bms app. I tried lowering the threshold on the first “pull over” but that didn’t work then pull over again and turned off the battery sense and detect settings and it started charging. I drove for 45 minutes and pulled into a rest stop and pulled the fuse for 7 pin power in the Pilot. I turned turned on the auto detect with factory defaults and it’s working perfectly now apart from a balancing issue with the bms

 

[burgerking]

Is there a 12v to 48v, 24V to 48v, 48V to 48V charger?