Booster Diode and Solenoid to Redarc BCDC

[drivesafe Senior Member Find all posts View Profile Close drivesafe]

Sorry folks but you are now talking about an unrelated charge requirement.

The OP posted up about charging his auxiliary battery, which happens to be under the bonnet of his Toyota. You are now talking about camping ( house ) battery charging. How does this have anything to do with the OP's post?

If you match the battery to the requirements, and in this case, an Optima Yellowtop is by far the superior auxiliary battery, then even if you fitted a 40 amp DC/DC device, the LOW VOLTAGE Toyota alternator will still recharge the battery far quicker.

If you want to charge house batteries in a camper trailer or a caravan, then the best DC/DC devices come from Sterling and you can tailor the DC/DC device to suit your needs. From their new Wildside (19.5A ) all the way up to their 180 amp Battery to Battery charges.

Look outside the square and you will find far better gear, giving better results.

[Justinvv Member Find all posts View Profile Close Justinvv]

Another weekend playing around with the BCDC and fitting a few bits and piece.

https://youtu.be/2lvhOyvIrlQ

[drivesafe Senior Member Find all posts View Profile Close drivesafe]

Hi Justin and a nice video, and I hate to be a wet blanket but the meter installation is wrong.

To get an accurate voltage reading, the positive ( + ) wire from all volt meters MUST be connected directly to the battery’s positive ( + ) terminal and meter’s negative ( - ) needs to be connected to either the cranking battery’s negative ( - ) terminal, or a known earth point on the body of the vehicle.

What you have done is a common mistake that can easily give you a reading as much as a volt diffence between what your battery voltage is and what the voltage is at the junction you have connected to.

The difference in the actual voltage and what your meter displays is a result of voltage drop caused by the current being drawn by any appliance connected to the same wires, and the way you have wired up the meter, you are going to get voltage drop on both the positive and the negative wire.

[dBC Member Find all posts View Profile Close dBC]

Justin, is your engine the 2.8L or the 3L? Glimpses of grill/headlights during your MPPT experiments makes me think it's a 2.8L? The general consensus around these parts is that the booster diode can't be used on the 2.8L. Have you found otherwise?

I found similar results to you when comparing the cheap PWM controller that was velcro'd to the back of my panel Vs the Redarc's in-built MPPT controller. The MPPT does seem to get more power out of those panels.

[dBC Member Find all posts View Profile Close dBC]

These are worth considering as an alternative dual voltmeter. For a while there they were offering discounts to pradopoint members, not sure if that's still running. They fit very neatly into any of the many blank switch panels. I went with the blue LEDs and they draw so little current that I don't even bother switching them off, so I can do a quick voltage check peering through the window without unlocking the car. I ran each of them to a direct dedicated feed off each of the batteries for added accuracy. Every time I start the engine, I can see how quickly the Aux voltage exceeds the Main voltage... almost always less than 1 minute as per the plot above.

[drivesafe Senior Member Find all posts View Profile Close drivesafe]

I have a simple Safety Lead that connects to the terminals of your cranking battery, and then runs into the cab, just run the twin wire in to the cab via the passengers door, while the door is opened.

With the twin wire located in the cab, shut the door on the wire.

The wire has a 1 amp in-line fuse, mounted near the battery and a set of twin screw block terminal in the cab.

You then fit the probes, on your multi meter, to the other side of each of the screw block terminal.

This is something you can either make yourself, or I can post one up to you.

Up until just recently, this is exactly how I have tested BATTERY voltage for the last two decades, and it is VERY accurate.

But in October last year, one of my customers told me about a simple and cheap bluetooth battery monitor, the Quicklynk BM2.



The monitor uses your SMART Phone as its display and has some unique features, and there are two versions.

There is a FREE single monitor APP and a MULTI-BATTERY MONITOR APP which is $15, but worth every cent.

The single monitor APP gives you a continuos voltage reading in 2 second increments, plus a 5 minute graph below the voltage display.

This graph is also continuos and but moves in 1 minute increments so that you can see what has happened over the last 5 minutes and this is idea for STOP/START alternator operations.






There is also a 24 hour graph that displays everything that happens from midnight to the next midnight.

This means you can lookup your voltages once you get home, instead of trying to monitor while driving.

Furthermore, the devices holds the 24 hour graph for the previous 30 days.

Once you upload the graphs to your phone, you will then have them available permanently.

If you have between 2 to 4 monitors, the $15 APP is the way to go.

While you can use the FREE APP with any number of monitors, and I was monitoring up to 6 units, you can only monitor one at a time and have to continually charge the monitor being linked to by the APP.

With the MULTI-BATTERY APP ( this is a new APP ) you can monitor up to 4 devices at the same time.

You can also view any 1 to 4 batteries on the 24 hour graph.






I am so impressed with these devices I now sell them with my kits, but you can get them off Ebay for as little as $39.95.

The reason I now sell them with my kits is because the MULTI-BATTERY APP allows the user to send the data to a third party, and in my case, it makes it incredibly easy to fault find for someone who is not able to monitor the batteries to see where a problem may be.

Anyway, lookup BM2 battery monitors for more info.

[Justinvv Member Find all posts View Profile Close Justinvv]

Yep, I have one of them also. Branded Maston. Its cool for logging etc, but a bit of a pain if you just want something to glance at.

https://youtu.be/5ZSWXrpZr4o

[Justinvv Member Find all posts View Profile Close Justinvv]

Justin, is your engine the 2.8L or the 3L? Glimpses of grill/headlights during your MPPT experiments makes me think it's a 2.8L? The general consensus around these parts is that the booster diode can't be used on the 2.8L. Have you found otherwise?

I found similar results to you when comparing the cheap PWM controller that was velcro'd to the back of my panel Vs the Redarc's in-built MPPT controller. The MPPT does seem to get more power out of those panels.

Min is the last of the 3.0L. I havent tried it on the 2.8. The 3l only had a temp compensated alternator, maybe the 2.8 has a variable voltage one.

With mine I get an extra volt using the diode. and it runs at a better charging voltage. I have had it since getting the car and had no issues.

I just changed to the BCDC to see if I could get more longevity out of the battery, and to experiment with the solar controller. Also allows me to use a different chemistry.

[Justinvv Member Find all posts View Profile Close Justinvv]

Hi Justin and a nice video, and I hate to be a wet blanket but the meter installation is wrong.

To get an accurate voltage reading, the positive ( + ) wire from all volt meters MUST be connected directly to the battery’s positive ( + ) terminal and meter’s negative ( - ) needs to be connected to either the cranking battery’s negative ( - ) terminal, or a known earth point on the body of the vehicle.

What you have done is a common mistake that can easily give you a reading as much as a volt diffence between what your battery voltage is and what the voltage is at the junction you have connected to.

The difference in the actual voltage and what your meter displays is a result of voltage drop caused by the current being drawn by any appliance connected to the same wires, and the way you have wired up the meter, you are going to get voltage drop on both the positive and the negative wire.

I checked this, and the voltage drop is minimal and its suffice for what I need it for. But you are right, it would be more accurate directly from the battery.

Maybe if I run out of things to do I will run a twin core up to the meter. And just use the Accessories to tun the meter on and off.

The negative is actually right the way back to the batteries.

[Justinvv Member Find all posts View Profile Close Justinvv]

Hi Justin and a nice video, and I hate to be a wet blanket but the meter installation is wrong.


What you have done is a common mistake that can easily give you a reading as much as a volt diffence between what your battery voltage is and what the voltage is at the junction you have connected to.

OK, I ran some 3 core and now have a direct Meter to battery connection to keep all the perfectionists happy

[drivesafe Senior Member Find all posts View Profile Close drivesafe]

Hi Justin, and it’s not a case of trying to be a protectionist.

You are about to test your setup and presumably you are going to post up your findings. If those findings are flawed because the voltage readings could be way off, it sort of defeats the purpose of the tests.

The info was meant as nothing more than a way to help you to get more accurate finding.

[Justinvv Member Find all posts View Profile Close Justinvv]

I agreed with you. I didn’t really have any voltage drop to worry about though for this exercise. But I had a couple free hours. It’s all done now.

Also so in full sun at mid day the redarc was “nearly” 2 Amps better than the PWM on the panels. On a partially depleted battery with a 12 amp continuous load on it.

[Boneyone Member Find all posts View Profile Close Boneyone]

Something to think about regarding conductor size for auxiliary power systems in general. A good book, Caravan & Motor-home Electrics, indicates that we should aim for between 0.15V to 0.2V drop across our cabling systems to provide optimal performance. To achieve this, the authors suggestion is to crunch the numbers as below:

V drop = (L x I x 0.017)/A

L=Conductor length in m, so that means total of both the positive & negative cables.
I=Current in Amps.
A=Cross sectional area in mm2.

This is really to assist with determining cable size for a load such as fridge etc but I thought it interesting to apply it to solar panels charging batteries. Especially as a lot of solar panels come with cable that appears to be about 2.5mm2 and some even come with extension cables longer than 5m.

So, with regards to a 5m cable from solar panel (assuming 6A) to battery or controller for example:

Using 2.5mm cable:

(10 x 6 x 0.017)/2.5 = 0.408V drop

Using 4mm cable:

(10 x 6 x 0.017)/4 = 0.255V drop

Using 6mm cable:

(10 x 6 x 0.017)/6 = 0.17V drop

Another way of looking at it, if you want to limit the voltage drop to 0.2V:

A = (L x I x 0.017)/Vd

A = (10 x 6 x 0.017)/0.2

A = 5.1 mm2

[dBC Member Find all posts View Profile Close dBC]

I just changed to the BCDC to see if I could get more longevity out of the battery, and to experiment with the solar controller. Also allows me to use a different chemistry.

Yep. I've been very pleased with my calcium SMF deep cycle aux battery. It's over 2 years old now (completely flattened once) and still seems to perform pretty much as it did when new. It may have lost a little capacity but if it has, it's hard to notice. Inspired by your latest video, I borrowed a mate's Maston bluetooth monitor and strapped it to my aux battery. It pretty much replicates my previous findings using the PowerLog 6S over a year ago.

I ran the fridge for 22 hours (9am previous day to 7am), then removed all loads and let the battery sit for 3 hours. The voltage at the end of that was 12.21V. Then I drove for about an hour (10am to 11am) rested for another 4 hours (11am to 3pm) drove for another 15 minutes, then drove home for over an hour (4pm to 5pm).

While I didn't have a logger on the cranker, I was monitoring it via the dual voltmeter in the cabin. It peaked at 13.9V very briefly and spent most of it's time around 13.6V. You'll see the instant the engine started (~10am), the 25A going into the aux battery caused the voltage to rise to 14.18V and climb from there. My 2.8L alternator has never put out 14.anything. There's simply no way it could have recharged this particular battery, in this particular starting state as fast as the 25A DCDC did. It spent the return trip in float mode and the battery resting voltage was still 12.8V at 8am the next morning.

[drivesafe Senior Member Find all posts View Profile Close drivesafe]

I ran the fridge for 22 hours (9am previous day to 7am), then removed all loads and let the battery sit for 3 hours. The voltage at the end of that was 12.21V. Then I drove for about an hour (10am to 11am) rested for another 4 hours (11am to 3pm) drove for another 15 minutes, then drove home for over an hour (4pm to 5pm).

While I didn't have a logger on the cranker, I was monitoring it via the dual voltmeter in the cabin. It peaked at 13.9V very briefly and spent most of it's time around 13.6V. You'll see the instant the engine started (~10am), the 25A going into the aux battery caused the voltage to rise to 14.18V and climb from there. My 2.8L alternator has never put out 14.anything. There's simply no way it could have recharged this particular battery, in this particular starting state as fast as the 25A DCDC did. It spent the return trip in float mode and the battery resting voltage was still 12.8V at 8am the next morning.

dBC I have no idea where you get your info from but your data does not add up, because there is no way your 25 amp DC/DC device could have fully recharged your battery either!

If you have say a 100Ah battery and you say it settled back up to 12.21v. without allowing that the battery has settled up from a lower voltage, but even at 12.21v, your battery has had at least 40Ah of it's total capacity discharged by your fridge, and that means you need to replace 40Ah.

You have a 25 amp DC/DC device and you reckon you replaced 40Ah of used capacity in 1.25 hours. That for a start does not add up.

Next, no matter what size DC/DC device you are using, or what size battery you have, the last 20% of the charge cycle is controlled by the BATTERY, not the charging device.

So your battery should have taken at least 5 hours of continuos driving, BEFORE the DC/DC device went into FLOAT mode.

I have been testing a new DC/DC device for one of my TRADE customers and here is a graph for how a 55Ah Lead Crystal battery, which had been discharged down to 10.5v and left for 24 hours.

It had settled back up to 11.39v and then a 19 amp DC/DC device was used to recharge it.

The DC/DC device was set to a BULK/ABSORBTION charge voltage of 15.0v and yet, even with a much higher charging voltage ( the higher the voltage, the quicker the charger ) it still took 8 hours to replace the 60Ah before the DC/DC device went into float mode.

You have either a miracle battery or battery charger!