Third Battery for 12v system in 24v truck setups

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Bob Otte

Bob Otte

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Looking to add a smaller Odyssey Battery and Victron 24v -12 v 70 amp converter to charge it to my '73 to power all my 12v accessories (stereo, cb, etc). I currently have a solar converter/balancer to power these but it has not been the most reliable. Curious if I could see some of your systems and how you have set them up for inspiration as well as feedback. TIA
 
Behemoth60

Behemoth60

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I've tried everything short of adding a second alternator. Happily, Recent technology developments have finally solved this problem. A DC-DC charger is really the ultimate solution to this old problem.
 
coldtaco

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Why run isolators in a dual battery set up? I just run a wire between the two batteries (appropriately sized) (12V). The left battery powers the vehicle, the right battery powers the starter, winch, and maybe something else (can't remember without looking).
 
Bob Otte

Bob Otte

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I'm far from an electrical guru and I really don't want to mess with the trucks electrical system since it is all 24v and works well. I would rather put a secondary 12v system in place
 
Felde

Felde

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Why run isolators in a dual battery set up? I just run a wire between the two batteries (appropriately sized) (12V). The left battery powers the vehicle, the right battery powers the starter, winch, and maybe something else (can't remember without looking).
?.. because batteries in a 24V setup do not like to be discharged or charged at different rates. Never pick 12V from just one battery which is in a 24V setup. It kills the batteries quite fast. I even put a load balancer between them to assure consistent charging.
 
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coldtaco

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I'm far from an electrical guru and I really don't want to mess with the trucks electrical system since it is all 24v and works well. I would rather put a secondary 12v system in place
Sorry, after re-reading the tittle I realized you were talking about adding a 12V battery (system) to a 24V system. I back out😉
 
Felde

Felde

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I'm far from an electrical guru and I really don't want to mess with the trucks electrical system since it is all 24v and works well. I would rather put a secondary 12v system in place
Good approach.
To have 12V available you may just put a 24V-12V step-down converter. I did that to feed my 12V radio and the lighter socket for any necessities.
Most tools run USB ports today anyway, so I put a USB port assy in the center console, which directly feeds from 24V, though.
But this all sucks from the starter batteries, so I'm not running heavy equipment like a cooler on it.
For this purpose I also made a plan:
In a so called dual battery setup, DC-DC chargers are state of the art. They assure a controlled charging of the secondary battery, which works better than just a cutoff relay. In modern vehicles, the alternator is not providing constant power (don't know how that is called in English). Here a DC-DC is the only working solution anyway.
A 24V dual battery setup (actually 2x 2x12V) is quite expensive and bulky due to the 2 additional batteries needed. And most appliances run 12V anyway.
So going for one 12V secondary battery is a good alternative. But this requires a 24V-12V step-down DC-DC charger. VIctron has some and redarck most likely also has.
The difference between a pure step-down converter and a charger is:
A converter just provides whatever is drawn from it. No control. The fuse is the limit.
The charger is 'smart' and controls its output in order to provide the battery a decent charging. It has bulk absorption phase and settling phase as needed.
Victron actually literally has this in its product names: The chargers bear 'smart' in it:
This is what I would use:
Regards Ralf
 
Bob Otte

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Thank you sir, where did you wind up mounting your charger and 12v battery if I may ask
 
Felde

Felde

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Thank you sir, where did you wind up mounting your charger and 12v battery if I may ask
I didn't do it yet. Budget is limited.
In the center console of my BJ73 there is a lot of room below this inner top mould. I hardly ever used it.
I ran a 6 AWG (good for 90A) cable there from the engine battery and put a fuse box as distribution hub in the center console (don't forget to put a fuse near the battery, too). From there I distributed power to some USB and socket outlets near the rear doors (to support me while camping).
So, the main cable is thick enough to support the secondary battery setup later on.
The DC-DC will go in the center console lower department there, too. I didn't take detailed measurements yet, though. Hope it fits.
The battery will most likely go behind the driver seat in a box on the floor, so close to the console. It needs to be well secured.
The room behind the passenger seat may take a fridge...
Regards
Ralf
 
Gengis

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There you go:
1633697056026
 
Bob Otte

Bob Otte

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Went with a different one , doesn't have all the fancy features but it's done. Wound up making a battery tray to fit in the area by the booster to keep it under the hood and out of the passenger compartment with inline fuses and multiple relays for switched power and to kill the converter when the truck was not running. Happy so far

IMG 0719


IMG 0720


IMG 0722


IMG 0724
 
T

Troopie59

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There are a dozens of different DC-DC Orion's! What you need is indeed an Orion "charger", they have also Orion "convertors" in almost the same housing. That's more like a power supply. You can put them in parallel for more current as you like. Beware these units run pretty hot, so place them vertical in a well ventilated place and leave at least 10 cm under and above the unit (this is what the manual says). The "Smart" ones have Bluetooth and can be controlled with the Victron connect app on your smart phone (a demo version is available). The output voltage and charge profile can be chosen from pre-sets for different type of batteries (AGM, Gel, lithium etc..). These parameters (e.g output voltage during absorption time etc,) can be adjusted manually too. A nice feature is that the unit "knows" when the de engine is running, even with modern car's with variable alternator voltage in which case most smart relais don't operate correctly. When the engine stops the charging stops automatically (preventing draining of the starter battery). This is also programmable.

Also you can choose between isolated and non-isolated versions. In most cases the slightly cheaper non-isolated will be oké.

I bought recently a 24-24V Orion-Tr Smart Isolated DC-DC Charger (400W) for charging a 24V 120Ah Lithium battery. Works flawlessly. Same will be true for any Orion 24V-12V charger I suppose..

John.
 
Bob Otte

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There are a dozens of different DC-DC Orion's! What you need is indeed an Orion "charger", they have also Orion "convertors" in almost the same housing. That's more like a power supply. You can put them in parallel for more current as you like. Beware these units run pretty hot, so place them vertical in a well ventilated place and leave at least 10 cm under and above the unit (this is what the manual says). The "Smart" ones have Bluetooth and can be controlled with the Victron connect app on your smart phone (a demo version is available). The output voltage and charge profile can be chosen from pre-sets for different type of batteries (AGM, Gel, lithium etc..). These parameters (e.g output voltage during absorption time etc,) can be adjusted manually too. A nice feature is that the unit "knows" when the de engine is running, even with modern car's with variable alternator voltage in which case most smart relais don't operate correctly. When the engine stops the charging stops automatically (preventing draining of the starter battery). This is also programmable.

Also you can choose between isolated and non-isolated versions. In most cases the slightly cheaper non-isolated will be oké.

I bought recently a 24-24V Orion-Tr Smart Isolated DC-DC Charger (400W) for charging a 24V 120Ah Lithium battery. Works flawlessly. Same will be true for any Orion 24V-12V charger I suppose..

John.
`Interesting, my manual didn't say anything about space above and below
 
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Troopie59

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`Interesting, my manual didn't say anything about space above and below
Then, I guess, you probably have a different manual. I have checked it and it's there. Also, the connectors must be directed beneath. Maybe this depends on how powerful the unit is (mine is 400W, 17A at 24V).
 
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JDM Journeys

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Excellent info @Troopie59 ! Answers some questions I had in looking at the options. Is there anything you can add about isolated versus non-isolated?
 
T

Troopie59

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The difference between isolated and non-isolated versions puzzled me also. I came to the conclusion that if you don't know which one you need, you probably don't need the isolated version. It's meant for special situations with gear that's sensitive for spurious signals that (maybe) are present at the alternator output. We don't use that kind of sensitive gear in our car's normally.

However, there is absolutely no problem with using the isolated version, if you prefer it anyways (just to be sure). But you need more cabling because you don't use the chassis or body as part of the circuit. And those isolated units are - as I said - more expensive.
 
Gengis

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What I am curious about is: If you have an isolated version in yer grubby little paw, can you short the two negatives and make it an non isolated version???? I could not find this info on the Victron site.
 
Bob Otte

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Then, I guess, you probably have a different manual. I have checked it and it's there. Also, the connectors must be directed beneath. Maybe this depends on how powerful the unit is (mine is 400W, 17A at 24V).
This is literally the entire manual included with my unit as well as all they have listed online. Mine is a 24/12 70A. Perhaps it is because it has a cooling fan on one end and doesn't rely on external heat sinks

 
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Troopie59

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This is literally the entire manual included with my unit as well as all they have listed online. Mine is a 24/12 70A. Perhaps it is because it has a cooling fan on one end and doesn't rely on external heat sinks

That's an older version. The newer ones don't have a cooling fan and rely on passive cooling. Some customers complained that the newer versions run uncomfortable hot because of this. I have read a message from Victron customer service on a yacht forum (can't find it anymore though) that Victron recognized this problem and they did some hardware modifications early 2021 so the units after that date don't run that hot anymore at the cost of a little less output. This change is not noticed in their documentation or on the website. Also, Victron states that running hot of pre 2021 models causes no failure whatsoever because it is all within specs and also power output is reduced automatically to cool down the unit if really necessary. But that's not ideal of course. Some people run an external 12V computer case fan underneath the unit solving all cooling problems, if any.

I guess marketing guys or girls at Victron prefer the nice, compact form factor without a fan or massive heat sinks to reduce costs and space also. I am not too happy with those choices. Having said that, my (pre 2021) unit runs fine, becomes hot but not too hot. I always get a steady 400W from it as it should. May be this will be different when driving in really hot (dessert) conditions, I don't know. But I think Victron knows what they are doing.
What I am curious about is: If you have an isolated version in yer grubby little paw, can you short the two negatives and make it an non isolated version???? I could not find this info on the Victron site.
I am pretty sure this is possible indeed. I would suggest to ask Victron to be sure, and rule out any warranty issues as you operate the unit not as designed for.
 
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Bob Otte

Bob Otte

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That's an older version. The newer ones don't have a cooling fan and rely on passive cooling. Some customers complained that the newer versions run uncomfortable hot because of this. I have read a message from Victron customer service on a yacht forum (can't find it anymore though) that Victron recognized this problem and they did some hardware modifications early 2021 so the units after that date don't run that hot anymore at the cost of a little less output. This change is not noticed in their documentation or on the website. Also, Victron states that running hot of pre 2021 models causes no failure whatsoever because it is all within specs and also power output is reduced automatically to cool down the unit if really necessary. But that's not ideal of course. Some people run an external 12V computer fan underneath the unit solving all cooling problems, if any.

I guess marketing guys or girls at Victron prefer the nice, compact form factor without a fan or massive heat sinks to reduce costs and space also. I am not too happy with those choices. Having said that, my (pre 2021) unit runs fine, becomes hot but not too hot. I always get a steady 400W from it as it should. May be this will be different when driving in really hot (dessert) conditions, I don't know. But I think Victron knows what they are doing.

I am pretty sure this is possible indeed. I would suggest to ask Victron to be sure, and rule out any warranty issues as you operate the unit not as designed for.
That would make perfect sense if there was no cooling fan. Gave me a bit of anx for a moment wondering if I mounted it incorrectly
 

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