Redarc BCDC 1220 - Dual Battery charging issues

Submitted: Thursday, Jun 23, 2016 at 04:28
ThreadID: 132836 Views:9163 Replies:4 FollowUps:6
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Hi All,

Looking for some help regarding my Redarc BCDC 1220 charging unit.

What's happening is when starting the car the unit initially goes into boost mode for a short period where both the batteries are receiving voltages of about 14.7V - 15.4V.

A short time later both batteries will then enter absorption mode where the voltages go to about 13.6V - 13.8V.

This is where the problem starts. The starting battery will remain at 13.7V and does not cause an issue at any time.

However after a while of driving the 2nd battery slowly continues to lose voltage. I can be driving for hours on end and the voltage can drop down to 12.1V. If i leave the fridge on overnight at camp, often the 2nd battery is about 11.8V in the morning and problem snow balls from there, leaving me with a flat aux battery and warm fridge after 2 or 3 days.

The 2nd battery receives a small amount of charge in the boost and absorption modes when the car is started, however does not remain charging, even when the voltage drops below 12V.

From what I can gather, the wiring and fuses are all correct, I guess this can also be confirmed by the fact that the 2nd battery is receiving charge in the initial stages of charging.

Has anybody else had issues like this? Or maybe be aware of what might be causing this to occur.

Both batteries are the calcium type, starting being a sealed battery and aux a 105Ah. I have a 60L engel (fridge only), along with a couple of LED lights, only used at camp for a short time.

Any help would be appreciated.

Thanks,

Nathan.
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Reply By: phil p7 - Thursday, Jun 23, 2016 at 07:49

Thursday, Jun 23, 2016 at 07:49
Hey Nathan
I have a Redarc BCDC 1240 fitted to my Hilux.
It runs a 60 litre Primus in the Hilux. Its sounds like the same problem I encountered when I fitted the same to 105 AH deep cycle gel battery.

It runs the Primus and when driving runs the van fridge as well.
It drove me nuts cause it would not charge the 2nd battery fully even after driving for several hours.

I thought I had bought a lemon.

It looks as though you installed the system yourself as I did. Redarc have a great Tech advisor to phone for advise.
All I can do is tell you what I did to solve the problem.

I recently headed to the Redarc stand at the Van show - they said the system is virtually bullet proof and the fault must be in your wiring especially the earthing.

I had earthed mine to the chassis - big mistake - the chassis is isolated from the cab by rubber mounts - the main battery is earthed to the cab not the chassis. the second battery was charging at a fraction of what it should have - 2nd battery ran down after 2 days camping.
Also redac advised that they must have a common earth. The 2nd battery- the BCDC charger and the cranking battery must have a common earth.

So I did this and now she works a treat. Second battery goes to boost on start and adsorb when at 13.8V. Runs both fridges - no problems. Great product.

Hope this helps
Cheers
AnswerID: 601742

Follow Up By: PatrollingOz - Thursday, Jun 23, 2016 at 10:26

Thursday, Jun 23, 2016 at 10:26
Thanks for the follow up, sounds exactly like the issue I'm currently having.

I'm out the country for a few days, I'll have to check the earthing when I get back.

Cheers,

Nathan.
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FollowupID: 871280

Reply By: Notso - Thursday, Jun 23, 2016 at 08:58

Thursday, Jun 23, 2016 at 08:58
Sounds like a supply voltage problem. Or as said above a poor earth.

Can you check the voltage at the input terminal of the unit. If it drops too low then the unit won't charge. Not sure what the minimum is for these units. If it works when your main is at at 14.7 volts but not at 13.7 this could be the issue. It isn't the voltage at the supply end of the circuit but the voltage at the BCDC input that matters.
AnswerID: 601745

Follow Up By: PatrollingOz - Thursday, Jun 23, 2016 at 10:33

Thursday, Jun 23, 2016 at 10:33
Thanks for the reply. I'm going to look at the earthing to see if that's an issue.

If the input voltage is too low, I'm guessing there would be a problem with the alternator or something on that side of the system?

Cheers,

Nathan.
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FollowupID: 871281

Follow Up By: Notso - Thursday, Jun 23, 2016 at 10:41

Thursday, Jun 23, 2016 at 10:41
Not necessarily, there could be a high resistance in the supply circuit somewhere. I would check the voltage at the input terminal when the system doesn't appear to be charging. If the voltage at the supply end is 13.7 and the voltage at the Input to the BCDC is a lot lower this will indicate a high resistance somewhere between the supply end and the BCDC.
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FollowupID: 871282

Reply By: Member - bungarra (WA) - Thursday, Jun 23, 2016 at 11:28

Thursday, Jun 23, 2016 at 11:28
I suspect the change over relay may be the issue.
A mate had a similar issue when we were away together a few weeks ago. After a lot of head scratching I diagnosed the relay as the issue however we could not prove it until we had a replacement when back in town........

It was the relay...unusual but that was it......multi meter on the relay terminals helps

cheers
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AnswerID: 601748

Reply By: HKB Electronics - Thursday, Jun 23, 2016 at 16:14

Thursday, Jun 23, 2016 at 16:14
First off, the voltage at the starting battery is set by the alternator and not the charger and should remain fairly constant irrespective of what the charger is doing.

The 14.7V - 15.4V sounds reasonable for a "full" calcium battery when being charged (absorption mode) The voltage of 13.6V will be when the charger goes into trickle charge mode, if there is no load on the aux then it should remain fairly constant, if a load is applied then the charger should return to charge mode.

I would be checking your wiring, you should have fairly heavy positive and negative cable running from the cranking battery to the charger, if you have a vehicle with a current sensor in the negative side of the cranking battery then the negative cable should run to the body earth point that the cranking battery negative connects to.

You should then have similar heavy wiring from the output of the charger to the aux.

It is not advisable to use the chassis as a negative return unless you absolutely sure that you have good earth points that can handle the return to the alternator.

Cheers

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AnswerID: 601756

Follow Up By: Michaeljp - Thursday, Jun 23, 2016 at 19:43

Thursday, Jun 23, 2016 at 19:43
The OP hasn't said the type of vehicle its mounted in, but could his problems be with these new smart alternators that drop voltage after a while? I was looking into a BC-DC for my 2012 patrol and figured out i need a Redarc 1225 LV model because of the smart alternator in the patrol.
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FollowupID: 871305

Follow Up By: HKB Electronics - Thursday, Jun 23, 2016 at 20:24

Thursday, Jun 23, 2016 at 20:24
The OP wrote:

"The starting battery will remain at 13.7V and does not cause an issue at any time."

The standard Redarc charger needs to see 13.2V so it should work ok.

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Follow Up By: Member - Lyncol - Sunday, Jun 26, 2016 at 11:01

Sunday, Jun 26, 2016 at 11:01
Something else to check you mentioned fuses remove these and replace with circuit breakers. The fuses and holders tend to overheat and Melt. Also the unit needs to have airflow to keep it cool, under bonnet not ideal.
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FollowupID: 871378

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