current output

Submitted: Thursday, Feb 23, 2017 at 09:55
ThreadID: 134345 Views:3482 Replies:6 FollowUps:14
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Hi

I have an Isuzu DMax with a 90A Alternator which also charges a second battery in the vehicle through a BCDC charger. I also have an Anderson Plug at the rear of the vehicle for charging the caravan battery.

I would like to measure the output through the Anderson Plug. I have a 50A wattmeter with anderson plug connections. Is the output likely to exceed 50A at the andersen plug and therefore damage te wattmeter??

Hope this isnt a silly question.

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Reply By: HKB Electronics - Thursday, Feb 23, 2017 at 10:13

Thursday, Feb 23, 2017 at 10:13
Depends on the size of the cable and the SOC of the battery batteries and the battery type. I have seen currents of 60A and above with a discharged battery in an under bonnet scenario using 10mm2 cable.

If you connect it with the motor idling you should be fairly safe as the alternator will only be able to supply around 50% - 60% of its rated power at idle, I'm assuming you have an AGM battery in the van.

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Reply By: Member - Blue M - Thursday, Feb 23, 2017 at 12:14

Thursday, Feb 23, 2017 at 12:14
What is a silly question is determined only by those you ask.

What sort of BCDC charger do you have?

I am glad you asked this question for I want to do the same test.
I was hoping that my Redarc 1240 BCDC charger in the Ute would/could only put out 40Amps max through the Anderson plug.

Cheers
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Follow Up By: Malcom M - Thursday, Feb 23, 2017 at 12:24

Thursday, Feb 23, 2017 at 12:24
You have to understand that amps are pulled and not pushed.
The BCDC may well be a 40a or a 140 amp unit but if the target device only wants 1 amp then that's all it will take.
Think Warragamba dam as the BCDC and a garden hose as the cable. Just because you have a gazillion liters of water available does not mean you will ever need it or indeed be able to stuff it down the hose.

How much current might flow through your Anderson depends totally on what gear you have connected and how much current it wants plus the size cable delivering the current.
Can't see how you could ever pull 40 amps unless the batteries in the trailer were flat.
Perhaps write down all the trailer devices and what power they consume and that will get you close to what might flow.
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Follow Up By: William 1 - Thursday, Feb 23, 2017 at 12:39

Thursday, Feb 23, 2017 at 12:39
Mine is a Redarc 12/20 charger.

I presume that means that the max it will ever put out to the anderson plug is 20A. I have a 150w 12v three way fridge in the van so presumably in theory there should be suffcient power. I just wanted to check that this was the case. Hopefully I won't stuff up the 50W wattmeter.
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Follow Up By: Malcom M - Thursday, Feb 23, 2017 at 12:50

Thursday, Feb 23, 2017 at 12:50
Correct
The 20 amps is the maximum amount of current that your charger can supply.
Even if you 5000 amps feeding the Redarc, unless it goes faulty, it can only give out 20 amps.
However you are in teh pooh. 20 amps at 14 volts = 280 watts (20 x 12 = 240w)
50 watts at 14v is a little under 4 amps. (50 @ 12 v is slightly more than 4 amps)
Have a look at this - calculator
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Follow Up By: Malcom M - Thursday, Feb 23, 2017 at 13:03

Thursday, Feb 23, 2017 at 13:03
William, the meter in the link is 50 amps not 50 watts so you'll be ok.
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Follow Up By: Batt's - Saturday, Feb 25, 2017 at 19:03

Saturday, Feb 25, 2017 at 19:03
Blue M I have had an LV1240 bcdc charger in my patrol for approx 1 yr I put a 130 amp/volt meter in line a couple of months ago and it was pulling 33 amps off the alternator to charge 2 x 105 ah agm's every things been working well so far. Now the redarc charger requires 60 amp fuses I had 50 amp fuses in line before installing the charger when I only had 1 battery to charge straight of the alternator via a dual batt system.so I just left them in place and put a couple of 60 amp fuses in my tool box just in case. So a couple of weeks ago we had an extremely hot day and for some reason the 50 amp fuse near the starter battery blew so I have now put in the correct 60 amp fuses so I would expect they have factored in start up surges so it can draw more than 40 amps sorry about the long story.
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Follow Up By: Allan B (Sunshine Coast) - Saturday, Feb 25, 2017 at 19:50

Saturday, Feb 25, 2017 at 19:50
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Batts,

Fuses operate by err, fusing. That is, they melt. To melt they require an elevated temperature which is created by the current flow adding to the ambient temperature.
So maybe your 50A fuse was subjected to a significant temperature in the engine bay (it can be as high as 80 degrees or more) adding to a current flow of less than 50 amperes. With luck the 60A replacement fuse will be OK.
Cheers
Allan

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Follow Up By: Malcom M - Saturday, Feb 25, 2017 at 21:58

Saturday, Feb 25, 2017 at 21:58
Batts
Current out is not the same as current in.
A 40 amp unit supplying 40 amps to the batteries will draw more than 40 amps.
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Follow Up By: Batt's - Sunday, Feb 26, 2017 at 13:12

Sunday, Feb 26, 2017 at 13:12
Yes that would be it Allan I had a similar thing happen once with a 70 amp trip switch mounted on the fire wall it worked well until we got those couple of extra hot days that we all experience each yr then it tripped out.

Yes Mal it will draw more of the batt especially when it boost the out put that's what I was trying to say in a round about way because they have a 60 amp fuse fitted on either side of the charger so one would expect that it can also surge up well over the 40 amps on the out put side I probably should've have mentioned that.
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Reply By: Sigmund - Thursday, Feb 23, 2017 at 12:39

Thursday, Feb 23, 2017 at 12:39
With my rig I discharged the 2 aux batteries (110 a each, in parallel) to around 11.5 v and ran the MUX with 120 w alternator at c 2500 RPM to see what they would draw. 19 amps. (Just an isolator in there, not a charger).

I got one of those inline monitors that go into an Anderson link to get the numbers. Very handy.Click me
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Follow Up By: William 1 - Thursday, Feb 23, 2017 at 12:51

Thursday, Feb 23, 2017 at 12:51
Yes. Thas the one I have. I just didnt want to put too much current through it. Hopefully all OK.
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Follow Up By: Nomadic Navara - Thursday, Feb 23, 2017 at 18:06

Thursday, Feb 23, 2017 at 18:06
William, if you have a look at those specifications you will see that it will handle 100 A for a little while (at least while you have time to switch the motor off or disconnect the meter.)
PeterD
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Reply By: HKB Electronics - Thursday, Feb 23, 2017 at 14:01

Thursday, Feb 23, 2017 at 14:01
William if you want accurate information you need to be specific.

Where is the charger mounted and what is its capacity?

If in car does it also charge a battery in the car?

Does the Anderson plug connect to the in car aux if there is one or to the cranking battery?

You should not be running a three way fridge off a battery your trying to charge as it will confuse the charger.

Do you intend to have another charger in the van?

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Follow Up By: William 1 - Thursday, Feb 23, 2017 at 20:25

Thursday, Feb 23, 2017 at 20:25
The charger is mounted in the rear of the ute and is 12V20A. The Anderson plug cnnects to the auxillary battery. The BCDC charger charges the auxillary batery.

I dont understand the difference between charging the battery in the caravan via the Anderson Plug compared with charging the auxillary battery when its running my Waeco in the rear of the Ute. What am I missing????
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Follow Up By: HKB Electronics - Thursday, Feb 23, 2017 at 21:22

Thursday, Feb 23, 2017 at 21:22
William you wrote:

"I have an Isuzu DMax with a 90A Alternator which also charges a second battery in the vehicle through a BCDC charger. I also have an Anderson Plug at the rear of the vehicle for charging the caravan battery."

Then:
"Mine is a Redarc 12/20 charger.

I presume that means that the max it will ever put out to the anderson plug is 20A. I have a 150w 12v three way fridge in the van so presumably in theory there should be sufficient power."

So from the above your charging a battery in the car from the charger mounted in the car. You also have another connection via the Anderson plug form the aux in the car to the battery in the van which has a three way fridge connected to it?

If this is the case there are a few issues with this setup, one the charger in car charging an in car battery and then another in the van is not an ideal setup as the charger won't get the true picture as to the charge state of the van battery.

If you also have a three way fridge connected to the van battery then it will draw 10 amps or more, this again will confuse the charger, not to mention only leave 10A to charge your two auxiliary batteries.

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Reply By: The Bantam - Saturday, Feb 25, 2017 at 10:35

Saturday, Feb 25, 2017 at 10:35
1 Bill ...... I think you are not asking the correct question ... yeh and you have some issues.

Any of these multi-stage charging systems work best with a direct relationship between one charger and one battery.

Three way fridges draw a lot of current in the order of 10 to 15 amps. Continuous. Most struggle to get sufficient current with low enough voltage drop all the way to the caravan and have the fridge run efficiently.

Three way fridges should be connected direct the the vehicle charging system thru a realy that only connects when the engine is running.

trying to charge a caravan battery on the same line as a three way fridge is problematic no matter which way you slice it.

having a chain of start battery, dc to dc charger, aux battery in vehicle, 3 way fridge and caravan battery and expecting it all to work well ..... is asking a bit much.

we could argue about appropriate arrangements.

But you are asking the wrong question. ..sorry

cheers
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Follow Up By: William 1 - Saturday, Feb 25, 2017 at 20:03

Saturday, Feb 25, 2017 at 20:03
Hi

I started this thread with a question on the anticipated output at my utes rear anderson plug as I didnt want to damage my 50A wattmeter if I connected it up. I am interested in understanding the way my ute and van are wired up. I have received some good advice from several forumites regarding the wisdom of my 20A BCDC charger being conncted with both my auxillary battery and the caravan battery which I hadn't considered. I therefore hooked the van up to my anderson plug via the wattmeter with my 3 way fridge in the van connected on DC and a small fridge in the rear of my ute running off the auxillary battery. This is the result of my test.

No motor running
12.6V at the ute battery
12.7V in the van battery
Minimal watts going through the watt meter.

Ute motor running
13.2V at the ute battery
12.7V at the van battery
160W going through the watt meter approx 12.9V

Turn off the fridge in the van with motor running
13.2 V at the auxillary battery
13.2V at the van battery
80W going through the wattmeter

I therefore conclude the rear anderson plug is serviced through the BCDC charger as I would expect to get more volts if the lead were from the alternator. The anderson plug charges the battery in the van which in turn services the 3 way fridge. This I think because the volts in the van battery rises when I turn off the fridge with the motor running.

If this is the case then I agree that the system is incorrect. Unfortunately due to the spaghetti wiring its hard to physically see the route of the cables in the van and ute.

I would welcome any comments as to whether or not my logic is correct. Having said that the last forum comment appears to have the same set up as me and experiences no problems.

The mind boggles.






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Follow Up By: The Bantam - Sunday, Feb 26, 2017 at 10:25

Sunday, Feb 26, 2017 at 10:25
Bill mate lots of people have poorly to badly set up systems of whatever and "don't experience problems".

Just because the system does not fall over in a screaming heap, does not mean it has "no Problems"

your figures show that without the 3 way fridge, you have some chance of charging the van battery in reasonable time ...... but dropped to 12.7 volts, you will charge the van battery but incredibly slowly.

If you are trying to charge both batteries and run the 3 way fridge all off the output of your dc to dc charger ...... none of it will work well.

it might work ... but not well.

cheers
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Reply By: Member - Bigfish - Saturday, Feb 25, 2017 at 14:48

Saturday, Feb 25, 2017 at 14:48
William I have a redarc 12vbcdc 20 amp charger mounted in the rear of my Pajero. It feeds 2 x 130amp agm batteries. I also have an 80watt solar panel continuosly connected to the batteries as well. Had no problems in over 2 years. I also have camper trailer that has 2 x120agm fullriver batteries in it. When travelling I connect the trailer via an anderson plug. As soon as I do thie the trailer batteries receive charge from the redarc if the motor is running. If motor is not running then the trailer batteries are sharing the solar panel with the 2 car mounted agm batteries Solar puts out about4.5 amp through an MPPT regulator. I run a 40 litre engel and a 47 litre evakool. Batteries are always in high state of charge. As has been said...you will only receive enough amperage as it deemed necessary to top up battery. Mount a 12 volt voltage gauge and keep an eye on this. Simple way of knowing if everything is working as it should be and the batteries are being charged correctlt. I also have a 100amp wattmeter that lets me know how many watts/amps my trailers contents have used or are using. Handy gadget to have .
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