12 volt control box.

Discussion about any electrical topic except 240 volts. Solar, converters, inverters, lights, battery chargers, etc
User avatar
T1 Terry
Posts: 15963
Joined: Fri Nov 23, 2012 3:44 pm
Location: Mannum South Australia by the beautiful Murray River
Has thanked: 50 times
Been thanked: 30 times

Re: 12 volt control box.

Post by T1 Terry »

We use them or the Victron DC to DC because they are so reliable. Not sure about the 50 amp claim, 40 amp continuous is a more realistic expectation. The ability to also handle a few portable panels is a bonus as well as the one unit able to handle 12v or 24v starter battery systems to charge a 12v house battery.
The advantage of the Victron unit is it will talk to your phone via Blue Tooth and does a check every .... can't remember off hand, but you can set the voltage it looks for from the start battery and if it doesn't see that, it stops until the restart voltage (you programmed in) is reach that indicated the battery is being charged by the alternator again, so no need to add a an ignition powered wire to the controller or a Voltage Sensing Relay (VSR) to protect the start battery from over discharge.

T1 Terry
A person may fail many times, they only become a failure when they blame someone else John Burrows
Those who struggle to become a leader, rarely know a clear direction forward for anyone but themselves
User avatar
Kappy
Posts: 410
Joined: Mon Feb 29, 2016 11:24 am
Location: Wagin WA

Re: 12 volt control box.

Post by Kappy »

My new DC 2 DC charger arrived today was a good price with a Fleabay discount to boot. https://www.ebay.com.au/itm/284391220783
20220330_153553.jpg
Now to measure all the wiring, may have to pay to get them done as my heavy duty crimping tool is still in Wagin.
Anyway should be the end of my concerns.
Will look into some portable panels later.
Thanks every one
Cheers
You do not have the required permissions to view the files attached to this post.
Cheers

Kappy

Growing older is inevitable, growing up is optional.
User avatar
Kappy
Posts: 410
Joined: Mon Feb 29, 2016 11:24 am
Location: Wagin WA

Re: 12 volt control box.

Post by Kappy »

In the process of checking my wiring from Vehicle battery/alternator to my new DC2DC charger.
Checking to see if there was a fuse from near positive terminal on vehicle battery, as suggested, when I noticed something between positive cables (see pic)
20220331_083126.jpg
When I disconnected cable from the terminal to the left of it, there is no power getting to battery isolation switch.
To my untrained eye seems like some type of relay???
Some enlightenment would be handy thanks.
Cheers
You do not have the required permissions to view the files attached to this post.
Cheers

Kappy

Growing older is inevitable, growing up is optional.
User avatar
supersparky
Posts: 8784
Joined: Mon Nov 26, 2012 7:00 pm
Location: Home on the beautiful Gold Coast for a while.
Has thanked: 81 times
Been thanked: 66 times

Re: 12 volt control box.

Post by supersparky »

Kappy, that is a solenoid. Used to switch big currents. Just like a big switch. The grey wire is the one that switches it on/off. It is probably wired so that the start battery can only charge the house battery when the engine is running.
Check the voltage on the big left side terminal when the engine is running.
T1 may provide a better explanation in techno speak shortly.
Cheers
David

David and Terrie
2006 Winnebago Alpine
Not all who wander are lost.
User avatar
T1 Terry
Posts: 15963
Joined: Fri Nov 23, 2012 3:44 pm
Location: Mannum South Australia by the beautiful Murray River
Has thanked: 50 times
Been thanked: 30 times

Re: 12 volt control box.

Post by T1 Terry »

Just like Dave said, it is a starter solenoid being used as a battery isolator. When the ignition is turned on, there should be a "clunk" when the solenoid closes and you should see battery voltage on the start battery side, but no voltage when the ignition is off.
There could be a seperate switch as well or in place using the ignition to turn it on/off, so don't give up if there is no "clunk" when the ignition is turned on, just look for another switch.
This is in place of a Voltage Sensing Relay (VSR) and relies on actually being turned on/off rather than voltage determining when to turn on/off. Just be aware, at idle, the DC to DC charger could pull more current than the alternator is producing.

An alternative is to bypass this solenoid and run the grey wire back to the "ign" terminal on the DC to DC charger, this will drop the required voltage to turn on down to around 10v from memory, when power is not supplied to this terminal the Dc to DC charger will shut down at roughly 12v and not turn back on until it sees 13.6v on the input terminals.

Clear as mud eh :lol:

T1 Terry
A person may fail many times, they only become a failure when they blame someone else John Burrows
Those who struggle to become a leader, rarely know a clear direction forward for anyone but themselves
User avatar
Kappy
Posts: 410
Joined: Mon Feb 29, 2016 11:24 am
Location: Wagin WA

Re: 12 volt control box.

Post by Kappy »

T1 Terry wrote: Thu Mar 31, 2022 11:35 am Just like Dave said, it is a starter solenoid being used as a battery isolator. When the ignition is turned on, there should be a "clunk" when the solenoid closes and you should see battery voltage on the start battery side, but no voltage when the ignition is off.
There could be a separate switch as well or in place using the ignition to turn it on/off, so don't give up if there is no "clunk" when the ignition is turned on, just look for another switch.
This is in place of a Voltage Sensing Relay (VSR) and relies on actually being turned on/off rather than voltage determining when to turn on/off. Just be aware, at idle, the DC to DC charger could pull more current than the alternator is producing.

An alternative is to bypass this solenoid and run the grey wire back to the "ign" terminal on the DC to DC charger, this will drop the required voltage to turn on down to around 10v from memory, when power is not supplied to this terminal the Dc to DC charger will shut down at roughly 12v and not turn back on until it sees 13.6v on the input terminals.

Clear as mud eh :lol:

T1 Terry
Clear as mud is probably an understatement, yes a little confused.
For me what seemed to be a relatively simple exercise, has me having to use my brain.
The grey wire with ignition off displayed about .5 volts, the terminal leading to house battery revealed the voltage of that battery, when the house battery isolated the reading was zero. With ignition on (and I think I heard a clunk) the reading is that of the main battery.
My aim was to connect a fuse between the main battery/alternator side and the cable leading to the house battery, as suggested in Enerdrive instructions as close to source as possible.
So to clarify this grey wire that appears connected to an ignition source I need to redirect to ignition connection on the DC2DC.
Just be aware, at idle, the DC to DC charger could pull more current than the alternator is producing.
Clarity please, research reveal the Alternator on my model sprinter, being ex Ambo is 120amp, the DC2DC is basically a 40ampcan't it draw than what the Alt is capable of?? way above my pay grade. How can I test the output amps??
In the process of checking.
Cheers
Cheers

Kappy

Growing older is inevitable, growing up is optional.
User avatar
T1 Terry
Posts: 15963
Joined: Fri Nov 23, 2012 3:44 pm
Location: Mannum South Australia by the beautiful Murray River
Has thanked: 50 times
Been thanked: 30 times

Re: 12 volt control box.

Post by T1 Terry »

Just be aware, at idle, the DC to DC charger could pull more current than the alternator is producing.
The alternator produces its higher current output at normal driving RPM, not idle. Often a high output alternator puts out next to nothing at idle, but that was more the older models from the late '90s, the newer type use battery voltage to excite the ..... ok, no need to go into that part eh :lol:

By using the existing solenoid, the start battery is connected to the DC to DC battery as soon as the ignition is turned on .... it takes a bit of time to do all its checks and balances, then starts up, so you get long enough to actually start the engine without any load on the start battery .... but that doesn't mean the alternator spinning at a low speed can keep up with the supply the DC to DC is looking, so it will drain some from the start battery while idling.

The DC to DC has its own voltage sensing, so by doing away with the solenoid and letting the DC to DC make the call as to whether there is enough voltage at the battery, it will turn on when it sees enough voltage and turn off again if the voltage drops too much .... because the alternator isn't keeping up.

This means, to recharge the house battery via the alternator and DC to DC charger, the engine will need to set to a fast idle, around 1,000 rpm to 1,500 rpm should be enough, then the alternator will be putting out enough to both recharge the start battery and supply the Dc to DC charger.

This might go straight over you head, but worth reading a few times till you get what it means.
Power is measured in watts, watts = volts x amps.
Using this formula, 40 amps at 14.4v charging the house battery = 560w going out of the DC to DC charger. Now add around 10% for the energy the DC to DC needs to do its magic and roughly 660watts is required on the input side of the DC to DC ......

That is the first part to get the head around ....

The start battery might be getting charged to 14v, but the cable between the start battery and anything connected along the way, like a fuse and a solenoid, will cause resistance and that will reduce voltage depending on how many amps are trying to pass through the cable .........

This is the next bit to get your head around, just because the wires at the DC to DC charger measure 14v when the unit is turned, when it tries to get that 660w out of those cables (from the first calculation) the voltage will drop.

Going back to our first formula, watts = volts x amps we can see that watts divided by amps = volts and watts divided by volts = amps.

Once you get the head around that, we can add the parts to the formula
watts we know, 660w need to go into the DC to DC charger, we can measure the volts when the DC to DC charger is under full output load, 40 amps at 14.4v, I'll take a stab at 11.5v, might be more, might be less, but you can put the correct number into the formula when you measure what it is in your set up.

Now we have two parts to the formula, 660w and 11.5v using my example, 660 divided by
11.5 = 57.4 amps ..... this is what the DC to DC charger will need at the input cables and that must come from the start battery, not the 40 amps going into the house battery but nearly 60 amps needs to be supplied by the start battery from the alternator.

This amp draw is needed when calculation the required cable conductor size (sq area) and the fuse that needs to be bigger than the amps required so it doesn't fail from stress .... for 60 amps I'd use a min of an 80 amp fuse, a 100 amp fuse would be a better choice in my opinion. Now you need to know the cable used will handle better than 100 amps without melting the insulation and starting a fire if there is a short circuit ..... 6 B&S (13.5mm sq) cable or bigger will do the job.

Wiring isn't as simple as you thought eh ;) :lol:

T1 Terry
A person may fail many times, they only become a failure when they blame someone else John Burrows
Those who struggle to become a leader, rarely know a clear direction forward for anyone but themselves
User avatar
Kappy
Posts: 410
Joined: Mon Feb 29, 2016 11:24 am
Location: Wagin WA

Re: 12 volt control box.

Post by Kappy »

Thanks Terry
The more info the better as long as it don't get to techo, I have a good chance of digesting.
Been chatting on a sprinter forum apparently Sprinter's have an inbuilt solenoid, apparently under the driver seat??
I really have no idea of what is the capacity of my alternator, either 150amp or could be just 90amp.
I Went to a local sparky this morning, his test was 14.3volts at idle.
I can't get a thorough analysis of the alternator/system for 3 weeks, here at Batemans Bay.
The question of the house battery its a lead acid battery with 770 CCA and only 90ah, I didn't even check that before, it was a spare as the previous one was quite old and wouldn't charge up using my trickle charger, didn't have access to decent charger, they're at home.
That is probably the root of my problem, it was a spare that I carried for jump starting if needed the previous house battery only has CCA on it .
So I think I need to re think type and size of house battery.
Are you also saying I can do away with that solenoid as I will wire the DC2DC to the ignition input provided.
Also have no idea who fitted solenoid definitely not a MB thing, not sure even St John Ambo, more likely the previous owner judging by the grey wire patched to an ignition source. Not the 1st dodgy bit of wiring I've discovered, mind you the ambo fit out people aren't that good either.
Cheers
Kappy
Cheers

Kappy

Growing older is inevitable, growing up is optional.
User avatar
Kappy
Posts: 410
Joined: Mon Feb 29, 2016 11:24 am
Location: Wagin WA

Re: 12 volt control box.

Post by Kappy »

A quick update.
Today I ran my 95 litre and my 18 litre from my fully charged 95ah battery.
I read 13.6 volts at the start and after 12.5 hrs it was still holding 12.2 volts and both were running.
I have no way of nothing the total amp draw over that period.
Test concluded at 2015 hrs, battery back on charge again.
To the layman in me that appeared ok.
Struggling to get required cable here @ Batemans Bay, even the auto sparking has to order.
Maybe I'll have to go fleabay, for cable and terminals.
Cheers
Kappy
Cheers

Kappy

Growing older is inevitable, growing up is optional.
User avatar
T1 Terry
Posts: 15963
Joined: Fri Nov 23, 2012 3:44 pm
Location: Mannum South Australia by the beautiful Murray River
Has thanked: 50 times
Been thanked: 30 times

Re: 12 volt control box.

Post by T1 Terry »

As I said in the phone call this morning, the fridges pulled the 95Ah battery down to 50% SOC, so in the 12 hrs they used roughly 45Ah, so to run for 24 hrs you will need a 180Ah AGM minimum, or a genuine 100Ah lithium battery .... good luck finding one of them as a drop in, even the Itech world 120 only delivers 84Ah. They use that B/S nonsense that a lithium battery can only supply 80% of the advertised capacity, so they inflate the capacity by 20% plus ...... that should still deliver 96Ah, but the battery shuts down at 84Ah under a constant load.
They probably use the C20 rating that AGM batteries use, discharged over 20 hrs, then the true 96Ah divided by 20hrs = 4.8 amps ...... that would power the little fridge for 24 hrs, but not the big fridge or the two combined because the amps draw would be up around the 15 amp mark, three times the capacity rated load ......

We have had drop ins here that customers have asked us to check if something was wrong, one was advertised as 360Ah :shock: yet any discharge faster than 15 amps caused it to shut down and at 15 amps it delivered 60Ah .... at least with our report he got his money back .....

If they don't show the capacity and load rate used to get that capacity along with the cut off voltage, you can just about bet the capacity is only 80% of the advertised capacity and measured at a C100 rate with a cut off around 10v, the above example of 360Ah battery, 80% = 288Ah, divided by 100 = 2.88 amp load, so the 15 amp load was 5.2 times the load it's capacity was measured at, the affect was 288 divided by 5.2 = 55.3Ah ....
Hopefully from that example you can see how they use smoke and mirrors along with what they don't tell you to mislead you into thinking you were getting a bargain price on a big capacity battery ...... basically, if you think you can buy 100Ah of lithium battery for under $1200, complete with a minimum BMS system, you are only fooling yourself into believing you've found a bargain .....

T1 Terry
A person may fail many times, they only become a failure when they blame someone else John Burrows
Those who struggle to become a leader, rarely know a clear direction forward for anyone but themselves

Return to “Low Voltage Electrical”