Battery Gassing with MPPT Charge Controller

[Mike Two Moons]

Hello:
I am seeking input as to why I am experiencing problems with my new battery charging arrangement, which I installed last fall. I have not been able to get clarification from either the vendor or manufacturer of my new MPPT250 charge controller by BZ Products (25 amp), which I installed with hope of getting an increase in current and better charge control of the solar panels to the batteries.

Problem:
Over winter I boiled two batteries dry, which I attribute to the MPPT charge controller. After taking the two “cooked” batteries out of service and connecting to the two remaining batteries, I find the battery now connected to the MPPT input is also overcharging/gassing.

Original set-up: (worked OK for 8 years)
- Four 6 volt deep cycle batteries connected in series and parallel to equate to 2 twelve volt units 480 AH capacity
- Two 80 watt solar panels (in parallel – I haven’t been able to get them to work in series) leading through a Flexcharge NC25A Charge controller 25 amp
- KISS wind generator also feeding through the charge controller

Revised set-up:
- - Four 6 volt deep cycle batteries connected in series and parallel to equate to 2 twelve volt units 480 AH capacity
- Two 80 watt solar panels (in parallel) leading through the MPPT charge controller
- KISS wind generator wired directly to the batteries (no charge controller)

Before leaving the boat for the winter (six months) the KISS was decommissioned, so is not part of the problem. The batteries were equalized, fully charged and fully watered. The MPPT is rated for twelve volt, so why is the battery, which is connected to the MPPT so active, yet its’ partner shows little visible activity?

Do you think I have misunderstood the capability of this charge controller completely and it isn’t compatible with 6 volt batteries? The manufacturer’s comments were – wire the solar panels in series and “possibly a PWM controller (pulse width modulation controller???) may be better suited for your purposes”.

It is said that having the solar panels in series is better for the output, but the fact I haven’t achieved that, shouldn’t be a factor……should it?

What am I missing? Before I put things back to how they were I’d appreciate anyone’s input.

I am on the hard in Alanya, Turkey for the summer, so can rely on shore power to keep the beverages cool, but would like to know if I can utilize this MPPT unit, if at all.

Thanks…………..Mike

[Kettlewell]

My BZ charge controller never worked well either--I was getting too little charging from it. I switched to the Flexcharge and it seems to work very well. I get a lot more "juice" from the same solar panels. I think if you want to go MPPT get a Morningstar unit.

[btrayfors]

Hi, Mike...

I feel your pain :-) But, you're in a great spot. Enjoy some of that wonderful Turkish cuisine and chill out a bit!

First, you need to make sure that the batteries and MPPT controller are wired correctly. You should have two pairs of 6VDC batteries, each pair wired in series, and connected together in parallel to yield 12VDC @ 440AH.

Next, you need to ensure that your MPPT controller is correctly regulating the charge from the solar panels. For this, you need:

1. a good multimeter to measure voltage from the panels, and voltage out from the MPPT controller; and

2. a decent clamp-on ammeter which will tell you exactly how much amperage the panels are putting out into the MPPT controller, and how much amperage the MPPT controller is putting into the batteries.

IMHO, EVERY BOAT should have these two tools...they are fundamental to troubleshooting any electrical problem.

You don't have to pay $350 for a Fluke 337 clamp-on ammeter. A good one can be had for about $70 on eBay....the Mastech MS2108 (NOT the MS2108A). Get one, and learn how to use it.

Don't know what kind of batteries you have but from your comments I assume they are flooded lead-acid batteries. If so, you should be seeing an absorption voltage of about 14.4-14.8VDC, and a float voltage of 13.4-13.6VDC.

At these charging voltages you should NOT see a lot of bubbling and gassing. If you do, it could well mean that your batteries are compromised and need to be replaced.

Flooded batteries should be checked at regular intervals for water needs, and filled with distilled water only. HydroCaps or WaterMiser caps can help a lot to help prevent water loss.

Keep the wind generator out of the equation, and by all means DO NOT connect it to the battery directly. It will surely burn them up unless regulated properly.

I completely agree with Kettlewell's comments. The Morningstar units are great...the 45 amp model would work well for you.

Bill

[Tellie]

btrayfors

1. a good multimeter to measure voltage from the panels, and voltage out from the MPPT controller; and

2. a decent clamp-on ammeter which will tell you exactly how much amperage the panels are putting out into the MPPT controller, and how much amperage the MPPT controller is putting into the batteries.

IMHO, EVERY BOAT should have these two tools...they are fundamental to troubleshooting any electrical problem.


PREACH IT brother

[sailorboy1]

how long each day does your controller keep the batteries in absorption before going into float?

If it is a default 1 hour and the boat has just been sitting, then you would expect your problem

[sailinglegend]

Originally Posted by Don L

how long each day does your controller keep the batteries in absorption before going into float?

If it is a default 1 hour and the boat has just been sitting, then you would expect your problem

I'm on the hard in Alanya and will be speaking with Two Moons soon.

It seems that the BZ controller has no Absorption voltage setting - only a float setting. The manual says when the float voltage of 14.1 v is reached the float light comes on and the current will reduce. This means the battery is never getting a proper charge, so it would seem that they sit at this voltage even when and if they do reach a full state of charge over the winter. Lowering the float voltage will mean even less charging current in the summer.

It would seem with no Absorption Voltage of 14.6 v or more to properly charge the batteries they have badly sulfated.

The BZ appears to be a very cheap unit - with good batteries buy a good charge controller that can be programmed to suit your battery size and Ah usuage.

[btrayfors]

Batteries aren't cheap, and you certainly don't want to damage new ones.

1. Throw out that BZ controller;

2. Get a good PWM or MPPT controller. Not sure of your battery bank size, but Morningstar makes some excellent controllers, like the SunSaver 15A MPPT model and the TriStar 45A and 60A MPPT models;

3. With a good controller, no need for a smaller solar panel; and

4. Get some HydroCaps or WaterMiser caps to help reduce water loss.

FWIW

Bill

[noelex 77]

Originally Posted by btrayfors

Batteries aren't cheap, and you certainly don't want to damage new ones.

1. Throw out that BZ controller;

2. Get a good PWM or MPPT controller. Not sure of your battery bank size, but Morningstar makes some excellent controllers, like the SunSaver 15A MPPT model and the TriStar 45A and 60A MPPT models;

3. With a good controller, no need for a smaller solar panel; and

4. Get some HydroCaps or WaterMiser caps to help reduce water loss.

FWIW

Bill

+1

If you can adjust controllers voltages there is no need to get smaller panels. Even with a large solar array a good controller will adjust the output so that its appropriate.

Unfortunately not many controlers do not have a suitable range of adjustment to set a charging algorithm that is appropriate for long term storage. When buying a controller it is an important feature that is frequently not considered.

A better controller would be my recommendation.

Morningstar make some good controllers, but many of them require hooking up to a PC to select a suitable algorithm for long term storage. Consider controllers fom Plasmatronics (PWM only), or Rogue that allow adjustment with a push of a few buttons.

[sailorboy1]

Originally Posted by noelex 77

+1

If you can adjust controllers voltages there is no need to get smaller panels. Even with a large solar array a good controller will adjust the output so that its appropriate.

+1

I paid little extra on my recent installation for my Outback Flexmax to get a controller that I could adjust every feature on without needing any thing else except pushing a button and changing the setting.

I wasn't too worried about ending up with a 60 amp controller because of this when my panesl were only going to put out 20 amps (plus I can add another panel later if needed).

[Kettlewell]

I couldn't figure out what my BZ was doing. The voltage would go up and then it would cut out, up and cut out, repeat endlessly. It never seemed to give the panels a chance to charge the batteries.

[Mike Two Moons]

Hi All:
After some in depth naval gazing and wiring/voltage checking, I have reached the conclusion that a couple of factors have caused the overcharging/gassing issue.
1. The float setting of the MPPT is 14.1. Trojan Batteries suggest 13.2. The MPPT setting may be acceptable when the batteries are under daily usage, but for wintering, this is too high.
2. The high charging, lead to higher water disipation over the winter. Much more than I have experienced before. I do not have the self maintaining watering caps and the batteries dried out - specifically the ones immediately connected to the MPPT.
3. The batteries were not in as good shape as I had thought when I closed up for the winter. They were all charged and fully watered, but were 9 years old. Specific gravity tests showed 3 out of the four now have a weak cell.

Next winter I will utilized a 20 watt solar panel to keep a small top up charge going and I am going to adjust the float setting to Trojans recommendations on the MPPT. That will all be happening on a completely new bank of batteries.

Thanks for the input and welcome any additional insight if you see a flaw in my thinking......Mike

[Mike Two Moons]

Hi All:
Thanks for all the feedback, but I now find I have to confess my sins. Sailinglegend stopped by the boat today and immediately saw the error of my ways.

I had botched the wiring of the MPPT. Connect the MPPT positive lead to the positive on the battery is straight forward enough until you involve 6 volt batteries in series. I had attached to the positive terminal which was in the middle of the pair and not at the end. So effectively I was charging a six volt battery with 12 volts. Let the gassing begin!

So yes my face is red (not just from this hot Turkish sun), but I think Sailinglegend's insistance that I wear this pointy hat around the marina for a week is a bit much.

The input has also indicated that I need to reasses and balance the charging qualities of my overall system under summer and winter modes.

Thanks........Mike

[sailinglegend]

Maybe his wiring error was a blessing in disguise because we have identified that his BZ MPPT250 charge controller is not fit for purpose as it is only a single stage device that doesn't have a boost voltage, only goes to a float of 14.1 - this it seems is adjustable.

If he had wired it all correctly then his batteries would only ever had got to 14.1v and sulphated because they were not being charged properly. Batteries need to get to their gassing voltage to stir up the electrolyte to stop stratification, and to reduse any sulfation.

Don't buy cheap MPPT controllers - buy ones that can be adjusted to suit your battery capacity and your AH usage. When you leave the boat re-programme them for a lower boost and float voltage.

[S/V Alchemy]

Originally Posted by Mike Two Moons

Hi All:
Thanks for all the feedback, but I now find I have to confess my sins. Sailinglegend stopped by the boat today and immediately saw the error of my ways.

I had botched the wiring of the MPPT. Connect the MPPT positive lead to the positive on the battery is straight forward enough until you involve 6 volt batteries in series. I had attached to the positive terminal which was in the middle of the pair and not at the end. So effectively I was charging a six volt battery with 12 volts. Let the gassing begin!

So yes my face is red (not just from this hot Turkish sun), but I think Sailinglegend's insistance that I wear this pointy hat around the marina for a week is a bit much.

The input has also indicated that I need to reasses and balance the charging qualities of my overall system under summer and winter modes.

Thanks........Mike

Some lessons are more costly than others. Look at the bright side: with 9 year old six-volts, even if you hadn't cooked them, they were elderly anyway. You have a chance on shore power to sit back, perhaps take a marine electrics course, and review your options.

There is very good advice in this thread. Had you been able to make a sketch of your set-up, it would have been pretty clear where the problem was. With both solar and wind, a MPPT like an Outback or Morningstar is a wise investment, along with metering to tell you what's happening at 10 AM, noon and 4 PM at the panels and at the battery terminals.

I would stick with the six volts, despite the more complex wiring. They are clearly able to be abused and if treated a little better, should last many years.

But I would also get the Hydrocaps and I would make sure, even if it involves having a boat electrician over to review your work, that you've done it right. Good luck.