Redarc BMS1215 failing to do its job (Help!)

Submitted: Monday, Mar 07, 2016 at 10:27
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A technical question that is very specific to the Redarc BMS1215 battery management system.

I use this system in the vehicle, have a 150AMP Gel Battery connected (Auxilliary) and it has two Redarc 120W solar panels connected.

The BMS1215 unit, which has worked well over a period of time, is now allowing a current draw from the cranking battery sufficient to drain it very quickly when the vehicle is switched off. Clearly the system is designed to prevent this from happening and my auto-electrician and myself have been in discussion with Redarc Technicians on the issue.

In fact, they sent a replacement unit and this is also allowing the same to occur.

All wiring has been checked (and rechecked) and was professionally installed and we have a high level of confidence the problem does not exist in the wiring or earth. But regardless, the unit is designed to not allow any current draw from the cranking battery if the vehicle is switched off.

When the 2x120W Redarc solar panels are disconnected, the current draw from the cranking battery stops. So it points to a possible issue in one or both of the solar panels that is affecting the electronic circuit in the BMS1215 unit.

Now, I could install a mechanical smart solenoid to resolve the immediate problem – but the question remains as to why it is happening.

Any thoughts or suggestions, adding that I continue to work with the Redarc people on the problem, they are helpful and concerned to get a resolution, but everyone is scratching their heads!

Cheers, Baz – The Landy
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Reply By: Member - Jim B8 - Monday, Mar 07, 2016 at 11:52

Monday, Mar 07, 2016 at 11:52
Baz
Nothing worse than a weird fault. Every circuit is different, so I wont even pretend. But you mentioned the solar panels, do they have blocking diodes fitted? Maybe disconnect them in full sunlight and see if they are producing around 17 volts each? If one isnt, check if one of the diodes hasnt blown? Just a thought. One thing, if it worked before, then its not a design issue, its a fault that has developed.

I have an interest in this because I have just dropped off my new Mazda for fit out, and they are installing all redarc gear, I have 2 x 120 panels, the 30 amp battery manager, and 2 x 120 batteries going in, hope it all works well
I am a fan of the RedArc gear, after trying the TowPro, very very good.

Only other thing I can suggest to look at is mounting, is the unit well ventilated?
Good Luck
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Follow Up By: Member - wicket - Monday, Mar 07, 2016 at 12:38

Monday, Mar 07, 2016 at 12:38
Your new Mazda ! What happened to the Iveco ?
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Follow Up By: Zippo - Monday, Mar 07, 2016 at 12:44

Monday, Mar 07, 2016 at 12:44
Jim's observation ("Just a thought. One thing, if it worked before, then its not a design issue, its a fault that has developed.") is a big clue, and the fact that a replacement Redarc unit gives the same result reinforces that.

Either the system caused the Redarc BMS to fail (and the replacement in quick time) - suggesting that there IS a system fault outside the BMS, or the BMS unit just died and the replacement was faulty too.

If you have the time (and haven't done it already) send the original BMS back to Redarc. I'm sure they'll be ready and able to quickly ascertain whether it is still functioning correctly, and that will indicate where the fault must lie.
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Follow Up By: Member - Jim B8 - Monday, Mar 07, 2016 at 12:53

Monday, Mar 07, 2016 at 12:53
Wicket
Well the Iveco is no more, I got rid of it, and bought a BT50 with 6 speed auto, getting it fitted out as we speak - i wont speak ill of the dead, but its fair to say it had some issues
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Reply By: HKB Electronics - Monday, Mar 07, 2016 at 11:57

Monday, Mar 07, 2016 at 11:57
I had a quick look at the user manual and it states for one 12V panel a bocking diode is not required, for more than on panel use as per manufactures instructions.

The above is a little ambiguos, a solar panel acts like a variable rsistor when shaded, the more voltage you apply to the panel the more "leakage" you get through it, two panels in parallel would have twice the leakage etc, generally with similar panels in parallel this is not an issue, with panels in series parallel combinations it could be an issue and blocking diodes can be used to overcome this, see blocking diodes and solar panels.

Generally there isn't any reverse current flow from a regulator so in most 12V installs blocking diodes aren't required, from what you have written you are getting reverse current flow from the regulator through the solar panels, a blocking diode would prevent this but I'm surprised this would occur as the regulator should isolate the panels from the battery when they are not producing power.

Check the panel wiring and if correct then cover the panels and connect to the BMS through an amp meter, if you see current flow into the panels I would be going back to Redarc and asking them why is this occuring, ie are blocking diodes needed and if so why?

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Follow Up By: Baz - The Landy - Monday, Mar 07, 2016 at 13:49

Monday, Mar 07, 2016 at 13:49
Thanks HKB

The Redarc panels have diodes in them. Could be possibly where it is going wrong.

On your last point, wiring appears all good and there is current flow when covered, so that is the very question we are asking Redarc.

And at pains to highlight they are working with us on it.

Thanks for your input, that was very useful.
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Follow Up By: Frank P (NSW) - Monday, Mar 07, 2016 at 14:01

Monday, Mar 07, 2016 at 14:01
Baz,

Unless I'm mistaken, those diodes in the panel junction boxes are bypass diodes, not blocking diodes.

To install blocking diodes, put one in the positive output cable from each panel. You have to get diodes with suitable current capacity for your panels. EG if your panel can output 10 amps then you'll need at least a 10 amp diode.

If you have two panels in parallel, joined into one lead going to the Redarc, then one diode of sufficient current capacity will work. To increase current capacity you may need two or more diodes in parallel to share the load.

Here's a link to some suitable diodes. $12.00 for 20 should see you out of trouble. :-)

If you do this, the band on the diodes should be towards the Redarc

Cheers
FrankP

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Follow Up By: Baz - The Landy - Monday, Mar 07, 2016 at 14:23

Monday, Mar 07, 2016 at 14:23
Thanks Frank…

As I understand it the Redarc panels set-up in my configuration should not need them (from Redarc).

However, the question remains as to why has it only just started happening, and secondly, why the BMS is failing to stop a negative drain on the cranking battery – that is what the BMS unit is designed to do regardless of any problem I may have with the solar panel or anything else for that matter.

At least, that is my understanding. Potentially it points towards something going amiss in the solar panels and affecting the BMS software.

Redarc have tried to replicate the problem with the old BMS unit that was returned however have not been able to.

Cheers, Baz
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Follow Up By: HKB Electronics - Monday, Mar 07, 2016 at 15:25

Monday, Mar 07, 2016 at 15:25
I can't think of anything the panels would do to upset the software in the BMS, they either produce
output if in the sun or none when not. If the BMS is leaking current back to them then the problem is with the BMS firmware or hardware.

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Reply By: Bob Y. - Qld - Monday, Mar 07, 2016 at 11:58

Monday, Mar 07, 2016 at 11:58
Bit of a mystery Baz! Doubt that I can help you though.

We also have a BMS1215 in our slide on camper, charging 2 x 120amphr batteries, and assisted by a 160w solar panel mounted on the roof. For extended stays have a folding 120w panel too.

In the time we've had it, it has been reluctant to charge using solar. In the mornings, full daylight, one can hear the relays attempting to kick in, but once the sun hits the panel, the BMS has gone to sleep, and usually needs to be manually "invigorated" to start charging. A check of the LCD readout shows the batteries being charged, all parameters perfect, except solar amps at zero.

Spoke to a Redarc tech once about this, and the only suggestion he had was to change from "Touring" to "Storage" mode, to allow the unit to kick in. I've done this numerous times, but it's not a solution, as if one was leaving camp early, the system wouldn't be charging at maximum amps.

Both 12v & 240v charging have been okay. Certainly haven't had the problem that you have Baz. I feel my drama will only be resolved by the unit returning to Redarc for inspection.

Perhaps this might be a legitimate excuse for you to upgrade to the 30amp unit or even the lithium model? :-). Hope you get it sorted soon.

Bob



Seen it all, Done it all.
Can't remember most of it.

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Follow Up By: Baz - The Landy - Monday, Mar 07, 2016 at 13:49

Monday, Mar 07, 2016 at 13:49
Hey Bob,

I'll keep you posted...

Baz
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Reply By: Mick O - Monday, Mar 07, 2016 at 13:21

Monday, Mar 07, 2016 at 13:21
Baz, I've been running my BMS for 6 years now with no problems. As you know, mine is sitting over 280 AH of Powersonic AGM's and manages 300W of solar as well.

Are the solar panels coming into the BMS "Open Circuit" without a solar regulator between the panels and the BMS? I was told at the time of install that leaving the standard solar regulator connected to the panels affects the BMS. The panels need to be wired direct or openly to the BMS unit with its inbuilt MPPT controller doing the work.

Cheers

Mick
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Follow Up By: Baz - The Landy - Monday, Mar 07, 2016 at 13:50

Monday, Mar 07, 2016 at 13:50
Hi Mick

They are Redarc Solar panels designed to integrate well with the BMS 1215, so asking them this question.

Thanks

Baz
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Reply By: Ross M - Monday, Mar 07, 2016 at 13:28

Monday, Mar 07, 2016 at 13:28
I haven't looked at the circuit for a Redarc device but it if relies on the negative line being switched off to protect the start battery., (similar to solar regultors switching the neg line), You may have a device fitted somewhere which is electrically connected across the switched side of the wiring and it is effectively negating the isolating feature of the Redarc.

I have had this experience with connections on solar regulators and it may be happening to you with your Redarc.

Cheers
RossM
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Follow Up By: Baz - The Landy - Monday, Mar 07, 2016 at 13:52

Monday, Mar 07, 2016 at 13:52
Thanks Ross

I'll ask the auto-sparkie.

Cheers, Baz
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Reply By: Baz - The Landy - Tuesday, Mar 08, 2016 at 14:04

Tuesday, Mar 08, 2016 at 14:04
We appear to have identified the problem!

Firstly, there is no underlying fault “within” the product, either BMS or solar panels, which is all Redarc equipment.

Equally, the installation by our auto-electrician is perfect.

Now I am not an engineer or auto-electrician so the least I say the better so I don’t misrepresent the findings as described to me by Redarc and my auto-electrician

It would appear that under certain conditions the BMS will allow a current draw from the start battery even when the vehicle ignition is switched off.

It would appear in very low light conditions, having an implication for the solar panels, and when the house battery is below the charge of the start battery, the start battery may provide some charge back through the BMS – in our case approximately 0.3A/H

In the configuration I have in the vehicle, I continuously run a 60-litre Engel Fridge, but it is an older one without a voltage regulator. Usually it isn’t a problem, but clearly conditions can present when it might become one.

Apparently mine is the first issue that has been brought to the company’s attention, although that isn’t to say it doesn’t occur in other units if the same configuration and conditions exist. I only detected it because the start battery was discharged to the point of not being able to crank the engine after a period of a week or so without use…

One takeaway for me is that wherein I thought the BMS unit worked similar to a smart solenoid and protected the start battery from being discharged when the ignition is switched off – this may not always be the case (under certain configuration and conditions). We have a simple fix for this…

The other takeaway, which is critically important to me is that the entire team at Redarc, an Australian company building products designed for Australian conditions, stand by their product and when problems arise, work hard to resolve.

Cheers, Baz – The Landy
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Follow Up By: Gramps - Tuesday, Mar 08, 2016 at 16:32

Tuesday, Mar 08, 2016 at 16:32
"We have a simple fix for this…"

C'mon Baz, don't keep us in suspense ! What is the simple fix ?

Regards
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Follow Up By: Baz - The Landy - Tuesday, Mar 08, 2016 at 17:05

Tuesday, Mar 08, 2016 at 17:05
Popping a solenoid in between the start battery and BMS.

Cheers, Baz...
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Follow Up By: Frank P (NSW) - Tuesday, Mar 08, 2016 at 18:08

Tuesday, Mar 08, 2016 at 18:08
This is a silver lining in the cloud, Baz.

Now you or your sparky can rig up an over-ride switch on the isolator so you can manually parallel your batteries. You can then winch off both batteries (if your battery-to-battery cabling is heavy enough) and also start off your aux battery if your cranker is flat (same caveat on the cabling, but probably not as critical).

If you decide to investigate this, just check with Redarc and make sure that if your BMS1215 stays in the circuit that it is not adversely affected because in this scenario the output of the BMS1215 will be paralleled with the input. In my application, I isolate my DC-DC charger when I manually parallel the batteries.

I can post a circuit diagram if you like - it's very simple.

Cheers

FrankP

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