New batteries - length of time in storage - sulfation - priming/conditioning

NicaSol · June 2015

Although not a stranger to RE sytems a recently purchased property with a system in the process of being renewed/expanded has been a challenge. Searches for information has led me (helpfully) to this forum several times. Time to join in. No joy after a week of trying to contact Trojan by email and phone. Thus, my first post.

I'm in a remote location in Nicaragua and any local help or installer expertise is simply not available (another reason for thus this post). The system is a battery backup system for when the grid power goes down (almost daily). The system has not been installed due to a delay in the shipment of solar panels and may not be installed for several weeks. I have a few concerns related to the batteries.

The batteries (12 Trojan L16H-AC) were purchased new in mid May. They were made in January of this year (date code = A5). I doubt that they have ever received maintenance charges since being manufactured. When I first measured their SG (hydrometer-temp compensated) it was 1.210 (+/- .003) for all cells.

I am concerned about the length of time these batteries have sat with a low SoC so I have been charging them. Since the system has not been fully assembled I have been using the inverter/charger (Xantrex 2524) only in charger mode to charge the batteries one series string of 4 batteries (24 volt system) at a time.

Following instructions on Trojan's web site I did a "normal" charge" and then an equalization charge. After the normal charge the SG for each cell was about 1.235. After the equalization and a 24 hour rest the SG is about 1.260 (temp compensated).

From what I have read deep cycle batteries need to be conditioned/primed for 100 cycles or so to reach their full capacity. Trojan states that for L16s that is 1.272. My questions:
1) Is the SG of 1.260 reasonable for a pre-conditioned L16 battery and can I expect an improvement with regular cyclical use?
2) Although "new" batteries, given the apparent (lack of) maintenance history, how extensive would sulfation be?
3) Before putting the batteries into regular use, and given the improvement after the first equalization, would further equalization charges help (or hurt)?
4) Would the use of a pulse module, e.g. the "Battery Life Saver", be of any benefit (harm) if sulfation is present?

Thank you for your attention to this post.

BB. · June 2015

OK... Battery health first:

TROJAN BATTERY USER'S GUIDE - Tuk Tuk Factory (PDF download)

State of Charge as a measure of Specific Gravity and Open-Circuit Voltage
Percentage Charge / Specific Gravity / Open Circuit Voltage Cell 6 Volt / 12 Volt
100 1.277 2.122 6.37 12.73
90 1.258 2.103 6.31 12.62
80 1.238 2.083 6.25 12.50
70 1.217 2.062 6.19 12.37
60 1.195 2.04 6.12 12.24
50 1.172 2.017 6.05 12.10
40 1.148 1.993 5.98 11.96
30 1.124 1.969 5.91 11.81
20 1.098 1.943 5.83 11.66
10 1.073 1.918 5.75 11.51

1.210 SG is around 65% SOC... The typical recommendation (not everyone agrees by the way)-- Below ~75% state of charge, batteries start to sulfate faster... And a day or so at below this SOC can start negatively affecting the battery's overall service life.

Add that batteries tend to age after as they get hot. For every 10C over 25C standard temperature, the aging life is cut by ~1/2 (25C is 100% life, 35C is 50% life, 45C is 25% life).

And, one would presume that sulfating is worse at higher tempratures too.

So, getting those batteries back over 90% SOC with a borrowed genset+battery charger would be a good idea.

NicaSol wrote: »

1) Is the SG of 1.260 reasonable for a pre-conditioned L16 battery and can I expect an improvement with regular cyclical use?

Roughly 1 month of not charging would discharge by 25% for typical flooded cell battery or ~1.227 SG would be OK. So 1.260 SG upon recept would should be fine

I do not know about Trojan and your local battery guy... In tropical climates, some mfg./distributors will reduce SG for the initial fill. Warm batteries perform very well (lots of capacity compared to cold climates) and running a slightly reduced SG will give you longer battery life.

2) Although "new" batteries, given the apparent (lack of) maintenance history, how extensive would sulfation be?

It does not sound like a problem in this case.

3) Before putting the batteries into regular use, and given the improvement after the first equalization, would further equalization charges help (or hurt)?

Equalization is for cells that are "out of balance" with other cells... If the cells are less than 0.015 SG between high and low cell, equalization is not needed.

However, cycling (cycling deeper than 80% State of Charge) and recharging (per Torjan's recommendations) is the next thing to do.

You can adjust your charging voltages a bit higher or lower depending on the SG readings. Also, watch water usage... If you are having to fill the cells every month--May be over charging. If you don't have to fill the cells every 2-6 months, may be under charging.

4) Would the use of a pulse module, e.g. the "Battery Life Saver", be of any benefit (harm) if sulfation is present?

Desulfators are always up for a wild discussion on forums.

There are people that don't believe they work, and can cause (usually small/temporary) problems in some cases (me).

And others that think "why not"--Won't hurt and may help.

And even others that think that desulfators work really well (help good battery to last longer, and possibly save some dead batteries).

We can talk about them more--But desulfator discussions can head into the weeds pretty quickly.

If you want to try one--Sure, won't usually cause many problems (but remember desuflators use a little battery power--So putting them on batteries without a charging source can discharge the battery even slightly faster).

-Bill

sawmill · June 2015

I installed 8 Trojan L-16H-AC batteries (24V) one year ago. In the beginning I could not get these batteries to the 1.277 level with normal charging, 1.265 was about the best I could obtain. My individual cells would vary (+ - .005 ). After a couple of months cycling the specific gravity began to come up and was more equal on all cells. Now one year later they are fine with their SG readings. Keep in mind I am NO battery expert but would not be too worried if one could keep these batteries at 1.260 with occasional equalization before putting them in service.

I have found that using the Trojan recommended charging voltage and time necessary for a full charge requires attention to the water level.

Bill

NicaSol · June 2015

Bill x 2 - Just want to say thanks for now for your informative and helpful replies. As it would happen Trojan got back to me with their thoughts. I'll report back in a couple of days how their suggestions worked out (after a 24 hour rest period or so between SG readings).

inetdog · June 2015

NicaSol wrote: »

Bill x 2 - Just want to say thanks for now for your informative and helpful replies. As it would happen Trojan got back to me with their thoughts. I'll report back in a couple of days how their suggestions worked out (after a 24 hour rest period or so between SG readings).

Trojan has made changes in the initial electrolyte SG for their RE batteries in the last few years. Make sure that you get the correct 100% SOC SG numbers from them for your particular battery serial numbers or production dates.

softdown · June 2015

FWIW: My limited experience with de sulfation is that it tends to extend auto battery life by one year. Not a miracle but generally worthwhile. Probably won't even do that unless the battery has been run down for a period. But mine usually encounter some mild abuse. I can definitely tell an old auto battery is stronger after de sulfating it. Cranks the engine faster and doesn't self discharge nearly as rapidly. But those early gains tend to dissipate over the ensuing months.

Getting six years instead of five years is worth it.

NicaSol · June 2015

This is what Trojan had to say.

"Response:
1.260 SG is about 90% SOC. Full charge SG is 1.270 – 1.280 (ideal 1.277). More equalization would have increased the SG. We recommend when storing batteries that a time to boost charge is when the voltage has dropped below 1.220 SG. If you use the Life Saver, you would have to back it up with some boost charging since it draws power from the battery to do it’s de-sulfation." ....and after asking for some clarification regarding the questions I asked them (same as my OP)...

"Response:
If all of battery(s) cells came up to 1.260, then this is a good indication that the batteries are OK. The 1.260 SG just indicates that the batteries are about 90% state-of-charge, and can be brought back to full charge by doing more equalization."

A company/person of few words but I followed their suggestion about "more equalization". Trojan's FAQ page also recommends equalization as a "freshening charge" (but with no guidlines, specs or limits) for when batteries have been in storage and have an SG of about 1.220 (and only after charging normally). Since the Xantrex 2524 didn't have the capacity to charge all 12 L16H-ACs as a single 3 string 24 volt bank I charged each of the 3 strings individually. It has now been at least 4 days since the last string was charged and all cells have held steady at a SG of 1.275 - 1.280. To get there I ran the strings through a "normal" charge first. This raised the SG from 1.210 to 1.235. The first equalization generally raised the SG to 1.260. The second equalization raised the SG to 1.275-1.280. I did two equalizations because after 3 hours on the 1st EQ: 1) the battery temp was going over 40C and rising fast (Trojan recommends 49C/120F max); 2) the SG was only at 1.260 which had me concerned (thus this post and my email to Trojan) and it wasn't clear in anything that I could find that equalization as a freshening charge could be done until the SG no longer rises or the recommended SG is reached.

These batteries are expensive in Nicaragua. Really happy I do not have thousands of dollars of really heavy paperweights.

Dave Angelini · June 2015

I am having trouble understanding why with a grid connection, even though it goes down daily, why can't the SW2524 keep 3 strings charged?
I have used that inverter/charger to charge 1,100 AH banks and it's 70 ADC should do the job with the grid, unless you are deeply discharging the bank! That will make paper weights.
Is it the cost of electricity? What is the cost of fuel for the generator? I spent quite a bit of time on both sides of Nicaragua in the mid 90's. Absolutely beautiful !

NicaSol · June 2015

Dave, thanks for bringing that thought up. It was on my mind too as I thought that perhaps I was missing something in my understanding of charge rates. With 12 L16H-AC (20 hr rate = 435 Ah) and a 24 volt system there are 3 strings of 4 batteries giving me a total capacity of 1305 Ah. The Xantrex manual recommends a charge rate of 10% of battery capacity. From what I have read and understand "battery capacity" refers to the entire battery bank, which in this case is 1305 Ah (3 x 435 per string). Ten percent of that is 130 Ah. The Xantrex 2524 has a maximum charging capacity of 70 DC amps, about one half of the recommended charging amps. So the following points are my reasoning for charging the strings individually.
1) given the unknown maintenance history (new, but 4 months old when I took possession) I wanted to make sure they were charged as quickly and effectively as possible.
2) everything I have read refers to the total Ah capacity of the battery/bank as a base for charging calculations regardless of SoC.
3) with that in mind I didn't think the Xantrex 2524 had the capacity to charge the full bank or it would only do so very slowly.

BUT, it seems to me (and perhaps you as well from the nature of your post) and correct me if I am wrong, that I'm not replacing/recharging the full capacity of the battery bank. In my case the SoC was 60%, more or less. Are you saying that I really only have to be concerned about the 40% capacity (520 Ah for the entire bank) that has to be replaced? And, that 10% of that - 52 amps - would be within the capacity of the Xantrex charger? I would really appreciate hearing from you (and anybody else) about this (or if my thinking/understanding is really off). Thanks.

Dave Angelini · June 2015

The very first thing you should keep in mind is quite a bit of what battery company's tell you is based on their wanting sell you more batteries but not before the warranty is up. The batteries you have will last longer if you charge them slowly (within reason) and discharge them slowly and not below 50% SG.

So, Yes you are only concerned with charging the capacity you have used and some loss during the process. You really do not have the issue that a generator has (ending charging as quick as possible to save fuel) as your cost for electricity is probably the same with a 70amp charger or a 130amp charger. Turn that SW on with your utility and get those batteries healthy right now!

New batteries - length of time in storage - sulfation - priming/conditioning

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