Overcharge Help

capewoods

My 2006 T@B Clamshell has two 125 amp AGM batteries wired in parallel.  About a year ago, I installed two 100 watt solar panels permanently mounted on the roof and I use a Trimetric TM-2030 system monitor and a SC-Solar Charger to charge batteries.  System has been great -- but yesterday I hauled the T@B over to my father in laws to install diamond plate on the front.  On the hour or so ride over, my master switch was on meaning that my batteries were being charged both by solar and by the TV.  When I arrived, I was horrified to discover that the Trimetric was reading battery voltage at 16 volts and I could hear my batteries bubbling!  They were, however, not hot to the touch yet.  I disconnected the TV and tripped the breakers on the solar.  I even reset the Trimetric thinking something had gone seriously wrong.  Loads on the batteries and a little bit of time returned the voltage on my batteries to normal, but I have no idea where the overcharge could have come from, what was causing the problem, or how much non-replaceable water in my sealed AGM batteries may have been gassed off.

On the ride back, my master was off meaning that my batteries were cut off from the tow vehicle and I had no problems.  At the suggestion of Bogart Engineering (who by the way are always an absolute pleasure to work with and I love their products), I measured charge voltage and amperage going into the batteries first from shore power alone, then from TV alone, then from Solar alone.  Nothing too surprising.  I saw 13.4 volts and 8 amps dropping over time to 1.5 amps on shore power.  I saw 13.8 volts and 4.5 amps dropping to 2.7 when connected to the TV.  Lastly, with solar alone, batteries are at about 94% and showing 13.0 volts with slightly positive amperage in heavily filtered sun.  In other words, everything seems pretty much OK.

It nevertheless scared me to death that I may have damaged these very expensive batteries and still can't figure out what actually happened.  My theory was that my TV alternator was somehow boiling my batteries, but that seems unlikely based upon additional research about the output of the alternator and I would have thought it would have also boiled my TV battery.  While the solar charger would have reduced charging from the solar panels to zero if it saw that high a voltage going in from the TV, it cannot (I don't believe) control that voltage input from the TV.

Does anyone of the really smart electrical guys out there have any ideas of what might have occurred or how I can test a theory?  Thank you in advance for your assistance.

Michigan_Mike

Sounds like your panels had the batteries charged up to their maximum and your TV was continuing to charge them beyond their capacity.   Here is a discussion I found that alludes to something similar and it might be of some help to you:

Charging Discussion

capewoods

I do have breakers between panels and my batteries that I can isolate at any time, but it sounds like I should just rely on my Trimetric to charge batteries with solar panels and use my master switch to cut off TV -- since it is likely the TV that is the more unreliable charger?

capewoods

Agreed.  And I really don't think it's the TV which is a 2014 Jeep Grand Cherokee with less than 40K miles.  Yet, where was 16 volts coming from?  If you keep dumping 14 volts into a battery, does the voltage increase above that?

Ratkity

Trimetric has a charger and a meter that work together with it via a specially wired phone cord-looking connector (with the standard phone cord clips at either end - don't use a regular phone cord). The trimetric meter can be set to charge the battery if Gel, AGM or Lead-acid flooded (AGM requires a lower charge input). There's also an "Equalize" mode on the meter for lead acid flooded batteries to condition them. It's a high-rate charge that isn't done for more than 2 hours at a time and there are special instructions on how to properly equalize batteries (venting, heat build-up, boiling off distilled water issues). Some AGMs can be equalized, but most manufacturers don't consider it necessary. Setting up the meter, one must make sure all the multitude of options are selected properly (battery type, max charge rate manufacturer requires, the amp hours capacity of the battery). The people who make it are amazing and will help you as well.

My trimetric meter senses when I'm on shore power or there is another power source to the battery (TV). Solar in general is considered a trickle charge, especially since optimally, panels aren't even close to 90+% efficiency unless the temperature is 72F and totally unshaded and pointed south during that 4-5 hrs of perfect sunlight. 

You can use the trimetric solar battery charger without the meter. You just lose some functions. It's a 3-phase charger just like in your converter. 

Most TV heavy duty alternators are also just trickle chargers to the battery. It's rare for a TV to be able to charge a flat or 50% discharged deep-cycle battery unless you are traveling 8-12 hours. I believe the power is not direct from the pigtail, but goes through the converter (someone will have to verify this for me - don't have wiring schematics of T@B), but in wiring my electric, only my Zamp panel connector goes straight to the battery and Zamp panel suitcases have smart controllers connected to the panels (so do the Renogy suitcase panels, although I ordered a 100W set without it because I already had the trimetric set up installed).

Keep us updated!! Hope you find out the problem soon.

capewoods

The setup you describe using Bogart Engineering's Trimetric meter and charger is exactly the setup I have, and I agree it's a great system.  That said, I'm pretty sure it can only reduce the solar power coming into the batteries to zero when it sees an overcharge coming from somewhere else.  It was on the Trimetric that I saw the voltage at 16.  And yes, I've since reduced the max voltage parameter on the Trimetric -- but I don't think that will throttle the voltage to the batteries down from either the TV or the T@B converter.

Ratkity

Cape, you are correct. It's a great system and steps down when it senses the battery voltage is at a certain level, even without the meter. Glad you got the meter with it or you wouldn't have seen an issue! I placed the meter under the sink cabinet. I can still open the front door and reach in to check the meter without undo effort (and it was easier to hide the wires).  The Victron system is pretty cool too from reports here. I hope you find your solution soon. All the best!

capewoods

Following up on my earlier post, I thought I'd update others as to what I've found.  After some further experimentation, I determined that neither my TV nor my T@B converter were the source of the overcharge of my batteries.  Rather, my SC-Solar Charger functioning through my Trimetric TM-2030 was delivering up to 16.5 volts to the batteries near the end of the absorb phase of the charge.  This was causing gassing in my VMax ChargeTank SLR125 AGM Solar batteries (two wired in parallel).   I called Bogart Engineering and confirmed that I had the correct charging profile and asked about the overcharge.  Bogart doesn't have a specific charging profile for the VMax batteries I'm using, but acknowledged that my selection of Profile 9 for the Concorde Lifeline 12V AGM battery was correct.  They also indicated that the high voltage is deliberate but is only applied near the end of charge under the following conditions:

1. That it be done ONLY when the amp input is less than 2% of C, where C=amp hour capacity of the system and

2. That it only be done for an hour or two.

According to Bogart, Concorde believes that this is good in a solar powered system which could otherwise undercharge the batteries. They allude to this in their technical manual on their Lifeline batteries (page 19). Apparently, Full River (another AGM battery company form China) also recommends this.  Bogart actually called Concorde and the following is from an email they sent me and asked me to share:

"Because of your email, I called Concorde battery company, and got some very helpful and authoritative advice from an engineer there.(Dave Vetetakis)  He verified that the profile we suggest for Concorde (Lifeline) AGM's is exactly what they would now recommend.  I expressed concern that the batteries were bubbling, but he said this is normal-- but said also that this should go on when the amps value was 2% of C (capacity) or less, and only until the 107% of overcharge was attained. (That's the "rPC" display on the TriMetric TM2030, NOT the regular amp hour display)  He said that in practice in the past the bigger concern was damage from undercharging, not overcharging.  They said they had done a lot of testing more recently on this topic to verify this.  He also thought it was good that the SC2030 was not was staying in float when batteries were only being lightly used (for example, storing an RV in the sun during very low usage of power.)"

I have since been trying to confirm with VMax that they too recommend this charging procedure for the ChargeTank SLR125 AGM, but have thus far not had a call or email in response to my inquiries.  I have examined all of their materials and do not see anything allowing for voltages in excess of the traditional 14.7V gassing point.  I have noted extensive discussions/debate on other forums regarding some gassing in AGM batteries and whether this is normal -- or just damaging the battery.   

Would love to hear other's experiences or thoughts and I'll update when I get the recommendation from my manufacturer.  In the interim, I'm limiting the charge to 14.7 volts.

ChanW

Thanks for the update. Mainly educational for me, as I have minimal experience with solar charging.

So do you have two different brands of battery in your system? Isn't it recommended to have the same brand/type/age of battery in a bank that's being charged on the same charging circuit, for just this quandary - different requirements for different batteries?

capewoods

I don't have two different brands.  Both batteries in my system are VMax ChargeTank SLR125 AGM Solar.  It's just that the closest Profile in the Bogart Engineering instructions for the TriMetric TM2030 instructions is the Concorde Lifeline AGM.

ChanW

Ah, thanks. I'm not a very thorough reader. B-)

capewoods

Just to bring this discussion full circle, I finally received an email from VMax (the manufacturer of my batteries) that suggested that although the high voltage top off profile may be recommended for the Concorde Lifeline line of batteries, no voltage in excess of 15V is ever recommended for charging VMax batteries.  They in fact suggested that charging voltage be limited to 14.6 -- which I have now done. 

Whether or not Concorde and Full River might be right that the greater threat to batteries charged with solar panels might be sulfation over time, I think I have to accept the recommendation of my battery manufacturer.  Hope this helps others.

Ratkity

Thank you for the update, cape!

JustJohn

capewoods said:

Just to bring this discussion full circle, I finally received an email from VMax (the manufacturer of my batteries) that suggested that although the high voltage top off profile may be recommended for the Concorde Lifeline line of batteries, no voltage in excess of 15V is ever recommended for charging VMax batteries.  They in fact suggested that charging voltage be limited to 14.6 -- 

That's odd, since they clearly recommend up to 14.9 v here: 

Nominal Voltage	20Hr Capacity	RC (min)	Energy (kWH)	Terminal Posts	Dimensions	Weight	Charging Current*	Charging Voltage	Float Voltage
12V	125AH	260	1.700	8mm (included)	12.9"w x 6.8"d x 8.7"h	75lb	8A-35A	14.4-14.9V	13.5V-13.8V

The above was copied from the VMax website.

jkjenn

The bubbling normally occurs during the equalizing (conditioning) phase of charging. It should take around an hour to complete. For lead acid batteries, it is part of maintenance to deal with the stratification that occurs over the course of the life of a battery. I see Lifeline indicates tat a conditioning charge can be used for their AGM batteries, as well. But, it does not appear as though it should be a part of the every day charging process. http://lifelineb.wpengine.com/wp-content/uploads/2015/12/manual.pdf

I am guessing your Bogart system is similar to my Victron system. I can edit the float and bulk charging voltage to match the specs provided by the battery manufacturer on my controller. When does Lifeline recommend equalizing the batteries?  Trojan recommends only equalizing when only wide or low specific gravity is detected.