Charging a third 12v battery from 24v? (1 Viewer)

[TLC Norway]

I run a 2H with the 24v setup. Previously i've run all my 12v accessories and gadgets from a 24/12v converter, but as the accessories stack up, and the need to be able to use some accessories while camping and so on, i want to run everything via a third battery, getting charged only when the engine is running, to prevent me from having dead batteries.

The best way to do this would be to add an extra 12v alternator, and have a completely separated system, but i dont have the alternator, and i do have the converter. And last, i want to use the space under my hood for a AC OBA setup.

I have a high quality 30amp converter, that puts out 13.8v and should be able to charge the third optima battery fine. Any opinions on this way of charging it?

So, how to wire this the best way possible, and is there any opinions if i need to change/upgrade the oem alternator?
And is it okay to activate the converter with a relay triggered by a signal from the alternator?
It would be best to use a voltage triggered relay/switch that turns on at lets say 25 volts or so, but i dont have it, and those dont come cheap...

again, i DONT want the converter connected unless the engine is running!

EDIT: forgot a few things...
Do i need a regulator or something in this setup? how will the battery cope beeing connected directly to a 30amp converter, when i dont draw any current from the 12v setup, or when all my gizmos are connected? i guess they will draw most of the current from the converter, and when the alt isn't running, the load goes from the battery... (?) not sure how that works...

 

[Stone]

You can switch the converter on and off with your key power by running it through a relay. You can easily pick up a 24V relay from Lordco and other such places...recommend going with something of decent quality like the Hella ones.

Pin 30 of the relay will run a fused wire to the 24V battery (+) pole, and Pin 87 will run a large gauge wire to the (+) of your converter. The (-) of your converter will just go to chassis ground as usual. Pin 87a of the relay will be blank and you should make sure it never touches ground as it's live when the relay is off.

Pin 86 of the relay is connected to ground, and Pin 85 is hooked up to a 24V (+) wire in your truck that is switched on with your ignition. Pin 85 and 86 are interchangeable unless you have a relay with an inline diode on the switch...then it has polarity.

Then you would just hook up your converter output to your auxilliary battery. You can buy a charge controller that can take at least 30A from places that sell solar power stuff if you want to prevent overcharging of your aux battery, if you want.

ToyRoverlander...he's talking about a CONverter, not an INverter...very different.

 

[TLC Norway]

Thanks stone, great writeup! I do know to hook up relays, but i was probably not clear in the first post.
I want the signal not to come from the key, as the converter would then be on prior to starting the engine.
I dont have any electrics discharging my battery before starting, and i would not add any.

Is there any hot spot to hook up the relay switch signal from, that is not hot when the engine stops/have not been started?

Tell me more about the charge controller...

 

[CDN_Cruzer]

I have a 30 Amp 12/24V converter hooked up to 30amp solar charger controller charging a 3rd optima battery. the solar charge controller is something like this.


30A, 12V Solar Charge Controller | Canadian Tire


I have a 50 amp Bosch relay that is hooked up to a little box on the right hand side of my engine bay labeled Power outlet. I have it hooked up to the wire that only goes live when the engine is running. not sure if your HJ60 has one of those boxes? here is a discussion about that

https://forum.ih8mud.com/diesel-tech-24-volts-systems/196657-24v-12v-converter-relay-switch.html

This setup has worked very well for me. I have camped from the truck for over a month and been able to use the 12V battery to supply all my needs and never had a problem with it running down. I also have left the truck sit for 2 weeks in cold weather and it starts right up with lots of voltage.

 

[TLC Norway]

I have a 50 amp Bosch relay that is hooked up to a little box on the right hand side of my engine bay labeled Power outlet. I have it hooked up to the wire that only goes live when the engine is running. not sure if your HJ60 has one of those boxes? here is a discussion about that

So, now we are getting somewhere! The wire that only goes live when the engine is running, where do i find it?

I have nothing labeled a Power Outlet, and i coud not find anything relevant to this matter in the thread you linked to.

I would consider a solar charger like that, now i get what you mean.
Have one of those at my cabin, for 50amps. that one can also charge the battery via a generator.

I am also making this setup for camping, and would like it to be as simple, but efficient as possible.
But i dont want to put all the cash into a voltage-triggered relay, damn expensive.

Thanks for your interest!

Back to searching for that wire to trigger my relay...

 

[Stone]

Hmm...I can think of a couple of wires that are hot when the ignition is in the ON position, but I can't think of any that are hot only when the engine is running. The VSV lead is one wire I can think of...let me know if you manage to find a wire that's hot only when the engine is actually running.

 

[Stone]

The only thing I can think of that might work is to use a voltage sensing relay and adjusting it so that it switches on when it senses the higher voltage produced by your alternator when the engine is running, and then shuts off when it senses nominal battery voltage. You may have to use the voltage sensing realy to switch a higher capacity relay or solenoid that turns your actual converter on and off. Here's what one of these voltage sensing relays looks like:

Voltage Sensor Relay

I have never tried this setup before, and I don't know what one of these costs...but it would seem like it would work. It's fully programmable, so you should be able to tailor it to the voltages that you see in your battery bank when the engine is running and when it's off. Would also save your battery from draining due to accessories being on, even while the ignition is on...for example, if your alternator packs it in, the relay will shut off the converter once it senses the low shut off voltage regardless of your engine running or not.

Really, a setup like this is very similar to the Redarc Smart Start Solenoid that I'm using in my truck for my dual battery setup. They make a 24V version that would work, and they are available for around $100. The only difference would be that the Redarc is not programmable.

Other than that, I was thinking if you didn't want the converter to be on while cranking, you could use a second relay switched from the starter relay so that when the starter goes, it cuts off the converter.

 

[CDN_Cruzer]

poor wording on my part sorry.

I think the wire is live whenever the key is in the on position not just when the engine is running.

 

[Stone]

Another thought...with the Redarc, you have an LED on your dash that will tell you when it is on or off. You can also install a switch that will "force" the solenoid to connect no matter what the voltage...though I can't think of any reason why you would want to do that in your application.

If you go the two relay route with the voltage sensing relay, you can install an LED inline to the voltage sensing relay power and also mount it on the dash to know when the system is on or off.

 

[seapotato]

There's also these things, not sure if they'd work for your situation or not, but I'm thinking of getting one for the 3rd "house" battery in my truck.

Probably like ones previously mentioned, they connect battery banks when a charging voltage detected.

Automatic Charging Relays - Blue Sea Systems

My uncles a marine electrician, and I haven't talked to him to see if these are the ones he was talking about when he mentioned them to me, but what he was installing all the time on boats lately instead of the conventional battery switch was in the neighbourhood of 80 bucks.

cheers,
ryan

 

[100 TD]

I think the wire you are looking for is the "alternator good signal". It depends on your alternator if it has this wire or not. The 100's have it, and the 80's IIRC, not sure how far back it goes, it only has power on it when the alternator is charging. Otherwise you want a voltage sensitive relay as previously mentioned or a redarc etc. Another way is to use an oil pressure switch, no oil pressure, no connection. However I don't like adding another thing in the oil circuit for something to fail.
(I've got a redarc you can have for $50 delivered if you are chasing one, IIRC 12.7v cut off and 13.6v cut in, but you need a 24volt one.............)
Charging with the converter should be fine, depending on what protection it has as the optima when dead flat may want to pull more than 30 amps but with voltage drop in cables etc it will probably be OK.

 

[TLC Norway]

Interesting answers here... some of the equipment is not available here, or too expensive to get.
My basic idea was to use a voltage sensor relay, but it passed since i could not find any here at an unkilling price. But the one that Stone suggests could not be too expensive... The ones i've seen here is marine grade, and for HD usage in 100amps and more.

Redarc does seem to supply such thingies, and their smart start setup seems really nice, i'd just have to add the converter to it. But maybe it's more of an professional expensive solution compared to the "old fashion" voltage sensor relay...

I have two digital voltage displays, one goes to the 24v circuit, the other one to the "house" 12v circuit.
There is also going to be a kill-switch, force-switch and a light for when charging...

That beeing said, does it not light a battery indicator in my dash when the alternator is not charging?
If so, i should be able to use that signal to a normal relay...

Dammit...now i'm starting to be anxious about the 24volts not getting enough charge without using a sensor before activating the charger/converter.

 

[Stone]

Let me know if there are any interesting solutions in Canada that are not easy to get in Norway, and I'll see what I can do to give you a hand. FWIW, I think that if you want to make sure that your 24V starting battery is always happy and never goes flat because of your accessories, then the Smart Start is probably your simplest, most cost effective solution...seriously. Those guys in OZ know what they're doing...their lives depend on their trucks when they go into the Outback, and this Redarc product that I"m using seems to be a good one.

Cheers.

 

[Granite Grinder]

I used one of these: Battery Chargers - Step Down
It's a true battery charger with built in voltage regulator, they come in 15A blocks, I have/had a 30A model. This was attached to an Optima Blue to run all 12V crap. When the truck is off, it draws it's sensing power from the 12V side (milliamps).
Just a suggestion

 

[Greg_B]

Something like bcd600 is another option. Very spendy though from analyticsystems. Keeping you eye to ebay, or such might net you one.

 

[TLC Norway]

Let me know if there are any interesting solutions in Canada that are not easy to get in Norway, and I'll see what I can do to give you a hand. FWIW, I think that if you want to make sure that your 24V starting battery is always happy and never goes flat because of your accessories, then the Smart Start is probably your simplest, most cost effective solution...seriously. Those guys in OZ know what they're doing...their lives depend on their trucks when they go into the Outback, and this Redarc product that I"m using seems to be a good one.
Cheers.

Thanks, i'll yell out if i would need something over there... I cant seem to find any prices to the voltage sensor relay, or where to get it.
It looks like there's a lot of shady options out there.

But HEY, you just talked me into the Redarc, and their product seems to match my needs... simple and cost effective, i like that!
Ill push a mail to them, and check the price...

I used one of these: Battery Chargers - Step Down
It's a true battery charger with built in voltage regulator, they come in 15A blocks, I have/had a 30A model. This was attached to an Optima Blue to run all 12V crap. When the truck is off, it draws it's sensing power from the 12V side (milliamps).
Just a suggestion

My first priority in this is to have NO connections drawing from the starting batteries when the engine is not running.
I bought my high quality converter from a well known Norwegian company, so that i can get it sorted out in minutes if it somehow would die on me.
But thanks for the heads up!

I think the wire you are looking for is the "alternator good signal". It depends on your alternator if it has this wire or not. The 100's have it, and the 80's IIRC, not sure how far back it goes, it only has power on it when the alternator is charging. Otherwise you want a voltage sensitive relay as previously mentioned or a redarc etc. Another way is to use an oil pressure switch, no oil pressure, no connection. However I don't like adding another thing in the oil circuit for something to fail.
(I've got a redarc you can have for $50 delivered if you are chasing one, IIRC 12.7v cut off and 13.6v cut in, but you need a 24volt one.............)
Charging with the converter should be fine, depending on what protection it has as the optima when dead flat may want to pull more than 30 amps but with voltage drop in cables etc it will probably be OK.

I'll go out to check if that wire is out there.
Clever thinking on the pressure switch, but as you say, more stuff to fail...
I'd love to get a redarc at that price, but i do need 24volts!

As to protect the optima, i've been thinking of that... when everything is up and running, my needs will most of the time be drawn straight from the converter, right.
So, maybe i should add a regulator or/and fused circuit to the battery, so that it wont cookup...?
I've had a amp-meter dialed in on the converter-circuit before, maybe i should put this after the converter to watch how much current is drawn, or after the battery, to see how much load i put on the battery...
fridge, cab lights, stereo, 220v converter at 300watts, cb, navi and gizmos and so on, all i really wanna do is stare out the front and side window for days, knowing that everything is in order and dont need looking after too much.

Because it's worth it!

 

[Stone]

If I remeber correctly, I think Radd Cruisers over in Vancouver Island is either going to be or is already a Redarc distributor. Maybe ask him if he's stocking them prior to hitting Ebay, if Redarc is the way you're going?

 

[NCPinz]

I'm just wondering if you're overthinking it a bit. Let the charge converter get current when the ignition is in the On position, but include a kill switch in case you're having issues with the 24V side. Expensive and hard to find relays won't help you when you are away from home.

While not a cruiser, I have a 24V Pinz and I've got my converter wired to an always hot circuit. When I want it to run, I flip the switch. Dirt simple and no relays to fail. You just have to remember to flip the switch.

 

[TLC Norway]

If I remeber correctly, I think Radd Cruisers over in Vancouver Island is either going to be or is already a Redarc distributor. Maybe ask him if he's stocking them prior to hitting Ebay, if Redarc is the way you're going?

Hmm...i'll compare the price when i get the info and quote from Redarc AUS.
I really dont know yet witch setup to run yet, gotta thinker a bit more...
Seems like a dead serious product, and it would definitely be added before i go exploring big time alone.

I'm just wondering if you're overthinking it a bit. Let the charge converter get current when the ignition is in the On position, but include a kill switch in case you're having issues with the 24V side. Expensive and hard to find relays won't help you when you are away from home.

While not a cruiser, I have a 24V Pinz and I've got my converter wired to an always hot circuit. When I want it to run, I flip the switch. Dirt simple and no relays to fail. You just have to remember to flip the switch.

I know, i always overthink solutions, and settle for the option that fits my need, and pricetag.
Maybe i'll just test it out without any voltage sensors, just ign. ON relay with a killswitch and add the redarc when i can spare the money.

Forgot to look for the charge/battery light in my dash when i went fooling in the snow today, check out my post for teaser vids.

 

[The Dude]

this is what I did: