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killarneygetaway avatar image
killarneygetaway asked

DC-DC charging between tow vehicle and 5th wheel camper 12v-24v

Hi.

I am upgrading the DC electrical in my camper to 24v so that in the future I can install a large inverter more efficiently. To that end, the charging from the vehicle 7-pin harness will no longer work. So, in order to get vehicle charging I need to install a DC-DC converter (12v-24v). As nice as getting the Orion Smart is, I feel it is overkill and not a necessary expense. Therefore, I would like to install the Orion 12/24-20 IP20 converter but it doesn't have isolated -ve connections. Based on my limited understanding, as long as the ground systems at both ends are connected with the correct wire sizes, an isolated system is not required. So, I was wondering if one of the fine experts on this site could confirm if my thinking is correct and if the attached setup is correct and adequate.

Additional information that may be needed is that the camper systems (lights, pump etc) are all still on 12v and I will be installing a step down converter to feed all the 12v. They will share the same ground path (camper chassis) as the 24v side. Other installed components are a Lynx power distribution box, Battery protect, Victron 100/50 MPPT charge controller, Battery shunt. Batteries are currently 4 - 6v Trojan T105 batteries but plan to upgrade to Lithium in the near future.

Also note, that I will be installing a properly sized relay (not shown on diagram) on the vehicle side so I can hook up one of the upfitter switches in the truck to turn on/off the power to the Anderson connector as needed.

Thank you,

J...dc-dc-charger-diagram.jpg

orion dc-dc
dc-dc-charger-diagram.jpg (51.5 KiB)
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ingo21 avatar image ingo21 commented ·

i would stay with 12v . then you do not need all the extra things.....and you probably will have problems with a common ground for 12v and 24v

i have a 12v and 24v system on my boat and i would NOT do it again.

the reason i did it is because i am using one of these TESLA battery modules which are 24V.

the size of your inverter is sort of limited to the size of your batteries. meaning your 4 - 6v Trojan T105 can only handle a certain amount of power to convert to 110v or 220v.

i am running a 5000watt inverter which is way to big for what i need.

again i would stay with a 12v only system........

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killarneygetaway avatar image killarneygetaway ingo21 commented ·
Thank you for your honest reply.


I am planning on upgrading my batteries to minimum 400ah lithium and will be getting at least a 3000w inverter after that. On 12v, that requires 4/0 cable vs 24v which would only need 1/0 cable. This is just a work in progress to get me there 1 piece at a time.


I've been going back and forth between 12v and 24v and what keeps drawing me toward 24v is the smaller cable size requirements.

Thank you.

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1 Answer
Kevin Windrem avatar image
Kevin Windrem answered ·

You should look at DC-DC CHARGER, not converter. A converter outputs a fixed voltage which will not work well as a charger ( voltage will either be too low for a full charge or could overcharge them if too high.


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killarneygetaway avatar image killarneygetaway commented ·
So I should look at the Orion-Tr Smart 12/24-15amp. The original question remains, can I use the non-isolated as illustrated or in this case, should I go with an isolated?


Thank you.

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Kevin Windrem avatar image Kevin Windrem killarneygetaway commented ·

Yes you can use the non-isolated version as long as you can make a common connection for both negatives

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kevgermany avatar image kevgermany ♦♦ killarneygetaway commented ·
I have something similar in my campervan. DC:DC charger from the alternator into 24V. DC:DC converter to drop the 24V leisure battery down for the 12V loads. Both Orions.

If you find a single charger isn't enough, can add a second later, as I'm about to do.


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