Charging a third 12v battery from 24v?

[100 TD]

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...

It gets a bit tricky to use this as, The light is ON when IGN is ON and engine OFF, The light is OFF when IGN is ON and engine is ON and charging, The light is OFF when IGN is OFF, The light is ON when IGN is ON and engine is ON and NOT charging. And the light gets power from 2 sources, it can be done but............

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...

Unfortunately hardly anybody sells the 24V one on ebay so you will have to pay a bit more I expect. Don't forget Surepower make basically the same product, as well as others, there may even be some electronic kits available etc to power a 40A relay............

My first priority in this is to have NO connections drawing from the starting batteries when the engine is not running..........
I'll go out to check if that wire is out there.

When the engine is "Not charging". How did you go with the alternator, is it internally regulated with 3 wires coming from it?

Clever thinking on the pressure switch, but as you say, more stuff to fail...

The pressure switch has been used sucessfully before many times, for starter motor disconnects so you caan't hold the starter on or engage it when the engine is running, you just need to screw a tee fitting in where your oil pressure sensor goes and add a pressure switch. However this doesn't guarantee your alternator is working, like a VSR.

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!

Wire all of your accessories directly to your 12v battery via fuses to protect the individual wiring of each different circuit. Wire your converter directly to the 12v battery, it should have it's own fused output.

..............Expensive and hard to find relays won't help you when you are away from home.

If he goes the Redarc/Surepower, they have a built in over ride function to bypass all electronics (basically powering the relay manually)

When I want it to run, I flip the switch. .........
You just have to remember to flip the switch.

The function of the automatic VSR is simply to fix that! Everybody forgets to turn the switch at some point and gets caught.
BEP Marine 24v 300amp VSR on eBay (end time 04-Feb-10 14:29:33 GMT)

 

[TLC Norway]

thanks for all the good answers, seems like this would do the same trick for me:
PST-SSB2280 for 24 volt systems at Off-the-Shelf and Custom 24 volt Power Supplies.

Half the price of redarc, is it cheap china ware or good enough?
I guess, if one of these failes, the result will not be a discharged 24v system, but an un-conditioned 12v system.

 

[Stone]

Which one were you looking at in that website? The only viable one I saw had an output of 24V...wouldn't work for charging your 12V battery.

 

[TLC Norway]

Which one were you looking at in that website? The only viable one I saw had an output of 24V...wouldn't work for charging your 12V battery.

None of these solutions will work for charging 12v, that's why i add the converter after the output. that's what i'd have to do with any of the other solutions, like the one from redarc.
The choice from redarc would be the SBI24 at http://redarc.com.au/static/files/SBI_1_Page_Spec.pdf
-and the output is still 24volts, that has to be converted to 13.8v to charge the aux battery for non-essential needs.

 

[Stone]

Oh okay, I misunderstood you. I thought that because I saw charging solutions on that page that you have found an all in one unit that has a voltage sensor as well as a step down converter. Cheers.

After looking at the specs...I think you're still way better off with a Redarc...or if you want to do it cheap, a non-voltage sensing simple solenoid. Did you see the price on the 40A model? That would be one heck of an expensive switch at $667! LOL.

 

[TLC Norway]

Oh okay, I misunderstood you. I thought that because I saw charging solutions on that page that you have found an all in one unit that has a voltage sensor as well as a step down converter. Cheers.

After looking at the specs...I think you're still way better off with a Redarc...or if you want to do it cheap, a non-voltage sensing simple solenoid. Did you see the price on the 40A model? That would be one heck of an expensive switch at $667! LOL.

It would be great to find an all-in-one model, but there is no such thing.

The one i mentioned in the last post is 84.50$ , and the redarc is almost the double, and more expensive shipping...

What did you look at $667? FUNO!

Still waiting to get a exact quote from redarc...

 

[Greg_B]

It would be great to find an all-in-one model, but there is no such thing.

Yes there is. Check out the link in my post above. 24-12 volt converter, charger, float charge. Just ubber expensive.

The Dudes system seems to the fit the bill, is simple, and from what I understand has proven reliable.

gb

 

[100 TD]

It would be great to find an all-in-one model, but there is no such thing.

Yes there is. .......................... 24-12 volt converter, charger, float charge.

The unit you have mentioned/linked to doesn't have voltage sensing, it is a voltage converter that produces approx 13.6v from a variable input source of 20 to 45 volts. The auto voltage seensing is the main thing that TLC Norway is trying to achieve as he already has a 24 to 12 converter. His is slightly better for the application as it outputs higher at 13.8v.

The Dudes system seems to the fit the bill, is simple, and from what I understand has proven reliable.

A simple on/off switch or relay is reliable, people on the other hand are not, but as he says and we all know, "You just have to remember to flip the switch". This is why a VSR is necessary, to make it automatic so you don't forget!

 

[Greg_B]

The unit you have mentioned/linked to doesn't have voltage sensing, it is a voltage converter that produces approx 13.6v from a variable input source of 20 to 45 volts. The auto voltage seensing is the main thing that TLC Norway is trying to achieve as he already has a 24 to 12 converter. His is slightly better for the application as it outputs higher at 13.8v.

It does voltage sense (unless we are not on the same page with that term) as the bcd600 senses when the battery is charged, and goes into float mode. In fact, the manufacturer calls it a battery charger. It also claims to have a adjustable output voltage: http://www.analyticsystems.com/Datasheets & Manuals/BCD/bcd600d.pdf

But, again..pretty much moot...as it's ubber expensive. I have a used one sitting on the shelf which will find itself an application at some point.

simple on/off switch or relay is reliable, people on the other hand are not, but as he says and we all know, "You just have to remember to flip the switch". This is why a VSR is necessary, to make it automatic so you don't forget!

The Dudes is just that. His (ala the diagram) has keyed relays which isolates the 12V battery from the starting bank when the truck is off. And the 12V charge going from the keyed converter goes through a charge regulator. Unless again, I am misunderstanding what you mean...

Cheers

gb

 

[The Dude]

Yup, my system is dead simple, isolates the batteries when the truck is shut off (guarantees a start), has a 7 amp charge regulator that is voltage sensitive and has been reliable for the last 4-5 years running a fridge, HAM stereo, inverter ect...

There is NO need to get a big charge regulator when you have the battery in the system. It is hard on your ALT and is not needed. The battery will supply all the amps you need and the 24->12 converter will charge the third battery

If you have the converter it should be done fairly cheaply.

two 24V 30amp automotive relays $20
one 12V charge controller $50
wiring $???

under the hood of my 60s there is an accessory electrical hub. It has ACC, BAT, IGN and ground. Use that to control your relays.

Becareful of voltage drop. On my first go around I lost almost a volt from the front of the truck to the back. With upgrade (heavier gauge wire) and an increase of voltage from my solar converter (brand of 24V->12V) I now get a nice 14.4V to my third battery. (which should be what you want for good charging)

 

[Stone]

Greg: I think the confusion here is that we are thinking about a voltage sensor that senses the voltage of the MAIN battery (24V bank), not the 12V "house" battery. The purpose of the VSR is to shut off power to the converter when the voltage of the 24V bank reaches a nominal low level so that it never depletes the starting battery...very much like how the Redarc works in my truck.

I think having a VSR that is set at the right voltage shut off would probably work well in making sure that the house battery gets a charge when the truck is running, and shuts it off when it isn't. If I were to do this, I would also add a manual HD marine battery switch inline to the VSR so that I have an option to manually disconnect the whole system if I wanted to.

Brad brings up a good point about voltage drop too...make sure the gauge of wire used is appropriate for the application. Depending on how long a wire you will need to run, it needs to be fairly thick.

 

[Greg_B]

Greg: I think the confusion here is that we are thinking about a voltage sensor that senses the voltage of the MAIN battery (24V bank), not the 12V "house" battery. The purpose of the VSR is to shut off power to the converter when the voltage of the 24V bank reaches a nominal low level so that it never depletes the starting battery...very much like how the Redarc works in my truck.

I think having a VSR that is set at the right voltage shut off would probably work well in making sure that the house battery gets a charge when the truck is running, and shuts it off when it isn't. If I were to do this, I would also add a manual HD marine battery switch inline to the VSR so that I have an option to manually disconnect the whole system if I wanted to.

Ahhh, gotcha, missed that part then. Cool. Well, for over $1000.00 Cdn the bcd600 does that too! "If the yellow Low Input LED comes on, the input voltage has dropped below 19 VDC (27 VDC on the -24 version). To keep from completely discharging the batteries (if the battery charger is being operated from batteries), the unit will shut down until the voltage recovers to 21 VDC (29 VDC on the -24 version). Make sure that the charging system is operating properly, and that the wires connecting the input voltage to the unit are not corroded or damaged."

Solar Converters has a charge controller which will shut off if input voltage goes below a preset voltage as well, but the only funky part about that model is the 12V load side has to isolated from the 24V side so the unit can output limit itself to 20amps. Really limits applications.

I think The Dudes is dead ass simple, and would have the same risk of failure as any system with a built in sensor. Probably less. Carry a few spare relays as part of your kit is good practice anyway.

gb

 

[100 TD]

The Dudes switch or relay system is reliable, simply an ON/OFF switch. Everybody can do this for any type of battery isolator or charge system isolator. As mentioned before the problem with this system is "people on the other hand are not" and nor are your friends or wife when they drive the truck.
"You just have to remember to flip the switch". This is what TLC Norway does not want.(if he can get an auto unit cheap enough)

What he does want is voltage sensing of the supply voltage.This is how most dual battery systems work, they ensure the main batteries are not touched unless there is excess charge available.
The voltage sensing of the Redarc/Surepower type isloator senses at approx the following voltages. It does not turn it's output on until the 24 volt battery system reaches 26.4 volts, which means the alternator is running. It disconnects when the 24 volts system discharges to 25.4 volts meaning the alternator is not charging, or it is loaded to capacity with other loads such as lights etc and can not maintain a higher voltage output.
What this voltage sensing does is "disconnect" the load (24 to 12 volt charger) from the main batteries at 25.4 volts, ensuring that nothing s draining the starting batteries and they are left in a fully charged state. No (not that I know of) 24 to 12 charger or converter has this voltage sensing function built in as they are converting from approx 20v to a higher voltage down to 12 volts. They do not care about an alternator, they are happy to run 20 to 28 volts.

The BCD600 does not sense the voltage input

 

[100 TD]

I think having a VSR that is set at the right voltage shut off would probably work well in making sure that the house battery gets a charge when the truck is running, and shuts it off when it isn't. If I were to do this, I would also add a manual HD marine battery switch inline to the VSR so that I have an option to manually disconnect the whole system if I wanted to.

The redarc has this availability if wired to a 3 position double pole switch, set it to AUTO/OFF/FORCE ON

 

[The Dude]

The relays take the human factor out of it. My wife jumps in and drives. There is no switch to flick. The truck does it for you buy having the keyed relay get it's power of the IGN circuit. It's only on when the truck is running. Off in the ACC or off position.

What I don't get is why you want to have voltage sensing while your truck is running?? Isn't a quick look on the dash volt meter going to tell you that?

If your alt isn't charging, the third battery is the least of your worries IMO

Most charge regulators will not charge with low voltage, so in a sense, if you have a failure on your primary 24V system, you will not draw that system down further charging the third battery. another reason to get a low amperage charge regulator. If you can find one in the 5-7 amp range, you should never have an issue with your alt keeping up.

 

[100 TD]

The relays take the human factor out of it. My wife jumps in and drives.

So does mine, and everybody elses! I have a redarc which automatically charges my auxiliary battery and keeps my fridge cold. My wife doesn't have to think about it when she drives, nor do I for that matter.

...........i want to run everything via a third battery, getting charged only when the engine is running,............................

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

The truck does it for you buy having the keyed relay get it's power of the IGN circuit. It's only on when the truck is running.

Actually it's ON when the IGN is on, whether the truck is running or not. This is not what TLC Norway wants!

What I don't get is why you want to have voltage sensing while your truck is running?? Isn't a quick look on the dash volt meter going to tell you that?

When you turn on your stereo and your high beam and you spot lights and you max out your alternator your voltage sensing relay automatically disconnects your third battery so it doesn't load up the system any more and drain your main batteries down any further. Dash volt meters are inherently inaccurate, an indication only and it requires constant supervision to pick up.

If your alt isn't charging, the third battery is the least of your worries IMO

If you have a third battery drawing your main batteries down you are in real trouble if your alternator is not working or performing poorly

Most charge regulators will not charge with low voltage, so in a sense, if you have a failure on your primary 24V system, you will not draw that system down further charging the third battery. another reason to get a low amperage charge regulator. If you can find one in the 5-7 amp range, you should never have an issue with your alt keeping up.

As mentioned previously, 24 to 12 volt chargers will pull your batteries down to 20 volts or lower .

The Dude, your system works for you and is great for many, but it's not what TLC Norway has requested. An automatic VSR controlled system protects you automatically witthout having to think about it or look at gauges or think about turning extra stuff on, it is how 95% + of automatic battery isolators work

 

[Greg_B]

The BCD600 does not sense the voltage input

Read this part again:

"If the yellow Low Input LED comes on, the input voltage has dropped below 19 VDC (27 VDC on the -24 version). To keep from completely discharging the batteries (if the battery charger is being operated from batteries), the unit will shut down until the voltage recovers to 21 VDC (29 VDC on the -24 version). Make sure that the charging system is operating properly, and that the wires connecting the input voltage to the unit are not corroded or damaged."

I don't think this is a viable option in this situation, however they are out there.

I personally would prefer The Dudes system (not only from a price point) and then run something that filled other needs, that included a voltage alarm: Roving Recovery - Madman Gauges, Digital Engine Monitoring Systems - available in Canada & USA

But, to each their own. TLC Norway will figure his own solution, and I simply hope our differing opinions help him choose his own system with eyes open.

gb

 

[100 TD]

The BCD600 does not sense the voltage input

Read this part again:

"If the yellow Low Input LED comes on, the input voltage has dropped below 19 VDC (27 VDC on the -24 version). To keep from completely discharging the batteries (if the battery charger is being operated from batteries), the unit will shut down until the voltage recovers to 21 VDC (29 VDC on the -24 version). Make sure that the charging system is operating properly, and that the wires connecting the input voltage to the unit are not corroded or damaged."

I don't think this is a viable option in this situation, however they are out there.

As already mentioned, not in respect to charging voltages, they are happy to TOTALLY discharge your batteries

No (not that I know of) 24 to 12 charger or converter has this voltage sensing function built in as they are converting from approx 20v to a higher voltage down to 12 volts. They do not care about an alternator, they are happy to run 20 to 28 volts.

As mentioned previously, 24 to 12 volt chargers will pull your batteries down to 20 volts or lower

But, to each their own. TLC Norway will figure his own solution, and I simply hope our differing opinions help him choose his own system with eyes open.

Agreed!

 

[TLC Norway]

wow, i disappear for a split second to go wheeling, and the thread has exploded.
thats two good cruiser-related happenings in a short time!

100 TD has gotten all the telepathy from me, even dough i am not that good at putting technical thoughts into writing!
When i said i did not want the converter on unless the alt was running, i did mean "i dont want the converter drawing current from the 24v system unless the charge rate and voltage is good at the 24v side."
This to make sure the aux battery always is charged as a second priority.

There is a lot of amps drawn on the original alternator when lights, fans, heating, stereo, gizmos, fridge and so on is on and at full speed, and some days i only drive the car for minutes, other days i drive for hours.
I also forgot to mention i have a warn 8274 coming my way, and it is 24volts. It's gonna need it's juice.
I just want the 24v to be kept in perfect shape, and in first priority.

THAT's why i'm gonna go the VSR route.
Redarc seems to be a good choice.

Thanks to everyone for putting things on the table, and thanks to 100 TD for reading my mind and putting it into words.

I'm still gonna use this thread to complete my 24-12v battery setup, finding a good product at a good price, write up the installation, and the following user reports.

Feel free to post in my build-thread at any time.

 

[Greg_B]

As already mentioned, not in respect to charging voltages, they are happy to TOTALLY discharge your batteries

If you are talking about the parasitic load of not being turned off by a solenoid like the redarc, or automotive relay like The Dudes setup...sure. With the BDC600 there may well be some slight draw as it sits there waiting for the voltage to go above the present minimum required to turn the charger on. I'm going to email the manufacturer and see what they say.

The one Granite Grinder posted up has no parasitic load from the 24V side, and a <1mA parasitic load from the 12V side when it is not charging. Likely designed this way to save the starting battery bank.

If you are talking about sensing voltage from the 24V side to turn the unit on and off I am not getting you at all, because it does that.

If you are talking about a standard 24v-12v converter which is left in the "on" or "hot" mode to the 12v battery...then yes, for sure. It's like leaving your car alarm on for weeks and weeks. Or not float charging the isolated 12V battery if the truck is sitting for weeks, and the battery is getting drained down by mem presents for the stereo, clocks...

It's all moot, as TLC Norway already has a good converter. TLC, I would look at a charge controller too, between the converter and battery...unless your converter has that feature already built in. And if you're really that worried about your charging system make sure your kit has a solder gun, spare alt brushes., and check out the latest in solar panels.