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Old 24-08-2012, 19:04   #1
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Absortpion Charging for 6V Trojan Batteries

Hi all,

My house bank consists of 4x Trojan 145 Plus 6V batts, series/parallel for a 12V 520 Ah house system.

As many of you know, Trojan recommends 14.8V absorption voltage and 13.2V float for a 12V nominal system.

Trojan Battery Company

I've set my Outback Flexmax 60 charge controller for the 14.8V spec, and it performs as set (i.e. 14.8V for a 1.5 hour absorb time as set by me). But, I feel like I'm gassing the batts. The batts are definitely bubbling, and toward the end of the absorb time my propane alarm even goes off because of the gases from the batts. Yes, yes, the batts should be ventilated, but I only have a passive vent system with no fan running. The practical aspect is I can't cook from the stove if the propane alarm has not cleared!

My questions: Does everyone run their Trojans at a 14.8V current, or do you scale it back a little, say 14.4. or 14.6? Does anyone else who charges per the Trojan 14.8V spec have issues besides me?

Thanks,

Frank
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Old 24-08-2012, 20:03   #2
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Re: Absortpion Charing for 6V Trojan Batteries

Frank,

14.8VDC shouldn't be a problem unless the batteries are already fully charged and/or the ambient temperature is very high.

This summer we've had outlandishly high temps, and that could be part of your problem.

Problem with setting time limits on the absorption phase is that they may well be too long (when temps are hot and/or batteries are already full) or too short (when batteries are well discharged and are taking a charge).

See the Trojan T-145 data sheet (a PDF...Google it). At the bottom is a lot of info re: temperature effects.

One thing which might help with the outgassing is the use of WaterMiser or HydroCap caps. All my Trojans (10 T-105s) have WaterMiser caps, and I routinely use 14.8 VDC for absorption and for "repeat absorption" phases. My Victron is set for "repeat absorption" every other day for 1/2 hour.

However, my batteries are all in a cooled environment, not in the very hot outside temps.

Bill
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Old 25-08-2012, 05:48   #3
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Re: Absortpion Charing for 6V Trojan Batteries

Thanks for the reply, Bill. I always appreciate your informed comments!

Regarding temps, I have a temp sensor running from the charge controller to the batteries, and the boat is conditioned to about 75 degrees since we have the A/C on 24/7.

I agree that the issue is probably not going to a float voltage early enough, but the guidance I've read on absorb times is 1 hour per 350-400aH.

I pulled up the data sheet you recommended (I never knew there was one, thanks!) and noticed the spec'd absorb charge voltage was 2.35-2.45/cell, so I think I'll dial it back to 14.6V.

I can also set the number of amps for when it cycles from absorb to float. Right now I had that set at 4 amps, but I'm gonna bump that up to 6 amps and see how that answers.

Thanks again,

Frank
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Old 25-08-2012, 06:03   #4
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Re: Absortpion Charing for 6V Trojan Batteries

Frank,

Sounds like a plan.

Don't forget the WaterMiser or HydroCaps....they make a difference!

Bill
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Old 25-08-2012, 06:19   #5
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Re: Absortpion Charing for 6V Trojan Batteries

My Xantrax 3 stage charger, has a "cold", "warm", and "hot", setting that bumps the parameters of all 3 stages up and down, to adapt to the ambient temperature. perhaps this is your problem?

The solar panel charger is similar. With our Trojan L-16s, even as full time liveaboards, self sufficiently and anchored out... We have no problem with gassing.

By cycling very shallow, and bringing them back up DAILY, to 100%, (totally with solar), the batteries will last > 10 years, The electronics last longer too, due to a higher line V.

With our hydro caps, we only need to add water in small amounts, about once every 4 months!

Their TALL L-14s and L-16s btw... have a MUCH longer life span, if you can get them to fit...

M.
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Old 25-08-2012, 07:56   #6
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Re: Absortpion Charging for 6V Trojan Batteries

Look at the battery return amps ( the actual current going into the battery) when this drops to 2% of the AHr capacity (10.4A in your case). The charging should drop back to float.
I think this will show your absorption time is too long for your system.
Adjust the absorption time so is generally coincides with the time taken for the return amps to be correct. You will need to check it over a few cycles.
The controler can be set up to do adjust this automatically on every cycle, but it requires some optional equipment (mate, DC and hub)
You can also look at the net amp hours and see at what stage you are generally dropping back to float.

Make sure you have temperature compensation with the right profile (Outback use 5mV per degree C ). This is important with the very aggressive absorption voltage.
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Old 25-08-2012, 12:30   #7
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Re: Absortpion Charging for 6V Trojan Batteries

Quote:
Originally Posted by noelex 77 View Post
Look at the battery return amps ( the actual current going into the battery) when this drops to 2% of the AHr capacity (10.4A in your case). The charging should drop back to float.
I think this will show your absorption time is too long for your system.
Adjust the absorption time so is generally coincides with the time taken for the return amps to be correct. You will need to check it over a few cycles.
The controler can be set up to do adjust this automatically on every cycle, but it requires some optional equipment (mate, DC and hub)
You can also look at the net amp hours and see at what stage you are generally dropping back to float.

Make sure you have temperature compensation with the right profile (Outback use 5mV per degree C ). This is important with the very aggressive absorption voltage.

Thanks, Mark and Noelex. I have the magnum remote/batt monitor/inverter-charger set-up, so I didn't get the mate, etc. But I can set the absorb time and the amp value threshold for when it goes from absorption to float as well as the time of absorption. I'll keep an eye on it for a few days and see how my adjustments are doing.

Frank
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Old 25-08-2012, 12:41   #8
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Re: Absortpion Charging for 6V Trojan Batteries

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Originally Posted by GeoPowers View Post
Thanks, Mark and Noelex. I have the magnum remote/batt monitor/inverter-charger set-up, so I didn't get the mate, etc. But I can set the absorb time and the amp value threshold for when it goes from absorption to float as well as the time of absorption. I'll keep an eye on it for a few days and see how my adjustments are doing.

Frank
I think you find adjusting the adsorption time will solve your problems. The amp value threshold on the outback is not much use on a boat because it cannot destinguish how many amps are going into the battery (which is the important number) and how many amps is used running loads.

For example the outback could be recording 15A going out. But 10A could be running the loads. With only 5A going into the battery. If only 5A are going into the battery at the absorption voltage you are well past the point where the charge should be dropped back to float, but the the outback has no way of knowing this.
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Old 25-08-2012, 13:11   #9
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Quote:
Originally Posted by noelex 77

I think you find adjusting the adsorption time will solve your problems. The amp value threshold on the outback is not much use on a boat because it cannot destinguish how many amps are going into the battery (which is the important number) and how many amps is used running loads.

For example the outback could be recording 15A going out. But 10A could be running the loads. With only 5A going into the battery. If only 5A are going into the battery at the absorption voltage you are well past the point where the charge should be dropped back to float, but the the outback has no way of knowing this.
Very good point, thanks again!!

Frank
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