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Old 21-03-2018, 09:41   #1
txg
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Trojan L16 voltage under load

We recently installed a set of two Trojan L16, Model SPRE 06 415. They were shipped to the caribbean and it looks like they have fallen over at some point, because the shop had to refill some water and there is a small dent on one top corner.

The shop recharged the batteries and they held the voltage for some days (without any load) so we assumed they are fine.

But: Compared to our old bank that was AGM but only half the size and three years old, they have a lot more voltage sag under load and i want to find out if this is normal behaviour.

When loaded with 130amps after a full charge, they instantly drop below 12v. When discharging with normal house loads of about 10amps they drop to 12,0v at about 70% according to the victron battery monitor.

When loaded with 130amps at 70% SOC they drop down to about 11V.

The three year old 60Ah Victron AGM that is still hooked up to position 2 of our 1/2/both switch shows about the same or maybe a little bit less voltage sag at these loads than the new Trojan bank which is not AGM but new and much bigger at 377Ah.

All voltages are measured directly at the batteries.

Any ideas on this, is this normal beaviour for a wet battery? Never had them before.
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Old 21-03-2018, 09:52   #2
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Re: Trojan L16 voltage under load

Quote:
Originally Posted by txg View Post

Any ideas on this, is this normal beaviour for a wet battery? Never had them before.
Hell my 460AH bank of batteries when at 95% charge will drop to 11 something if I run the toaster on the inverter. But after the toaster stops it goes right back to near when it was before I did and just be 19AH lower in charge. My last battery bank did the same thing.

And in the mornings with the battery at 80% if I run a 10amp total load the batteries will read around 12.1-12.2. That's just normal I feel.
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Old 21-03-2018, 10:21   #3
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Re: Trojan L16 voltage under load

Yes even quality flooded have higher resistance than good AGM, will drop more volts per high C rate discharge.

LFP is way ahead of both though.

Going to a bigger bank can help a bit as well.

Only real State of Health measure without very pricey gear is a 20-hour load test, more hassle than most are willing to set up, but if you can find a good pro to pay, may be worth it while they're still new.
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Old 21-03-2018, 10:22   #4
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Re: Trojan L16 voltage under load

Sailorboy, IMHO that's not normal at all. Voltages are a bit lower than one could expect with reasonably good condition batteries.

It is normal for a fully charged wet cell bank to drop to about 12.3-12.4 soon after a modest load is applied, but it will recover somewhat to around 12.4-12.5 as time passes and the load remains.

But voltages around 12.1 or 11. anything are MUCH TOO LOW.

Here's a graphic depicting load tests on four different battery banks. Two of them are gelled golf-cart batteries, over 10 years old. The others are T-105 flooded golf-cart batteries, about 7 years old. The blue curve is most relevant to this discussion: it depicts a T-105 golf-cart bank which has been fully charged AND equalized. It shows measured battery voltage under load for the first 20 minutes.

As you can see, after an initial drop in voltage, it begins to recover, and by the end of the testing period it measures 12.4 volts while still under load.

This is just about what I see every morning with my flooded battery bank, i.e., a voltage drop for the first few minutes followed by significant recovery.

By the way, AGMs and Gels do not exhibit the same drop-then-recover as do flooded LA batteries. Rather, they maintain a pretty steady voltage decay over time.

If the load is removed, the battery voltage will continue to climb until it reaches somewhere near a "resting state" where it reflects a pretty good estimation of state-of-charge.

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Old 21-03-2018, 10:26   #5
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Re: Trojan L16 voltage under load

I've seen those load curves before and they have never matched what happens in real life on my boat. And what really happens has been consistent for more than 1 set of batteries.
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Old 21-03-2018, 10:35   #6
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Re: Trojan L16 voltage under load

If the batteries were tipped to the point that they lost fluid and someone on the Caribbean just topped them back up with water, you may have a problem.

Charge the batteries fully, measure the specific gravity of the fluid, and compare it to the manufacturer's specs. Remember that there is a temperature correction.
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Old 21-03-2018, 11:35   #7
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Re: Trojan L16 voltage under load

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Originally Posted by donradcliffe View Post
If the batteries were tipped to the point that they lost fluid and someone on the Caribbean just topped them back up with water, you may have a problem.

Charge the batteries fully, measure the specific gravity of the fluid, and compare it to the manufacturer's specs. Remember that there is a temperature correction.
indeed. battery acid has been lost and not replaced.
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Old 21-03-2018, 14:05   #8
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Re: Trojan L16 voltage under load

Quote:
Originally Posted by btrayfors View Post
Here's a graphic depicting load tests on four different battery banks. Two of them are gelled golf-cart batteries, over 10 years old. The others are T-105 flooded golf-cart batteries, about 7 years old. The blue curve is most relevant to this discussion: it depicts a T-105 golf-cart bank which has been fully charged AND equalized. It shows measured battery voltage under load for the first 20 minutes.

As you can see, after an initial drop in voltage, it begins to recover, and by the end of the testing period it measures 12.4 volts while still under load.
That graphic is for a 10A load. When you pull around 1kW through an inverter for a microwave or toaster, you are drawing over 80A and will see a much larger initial drop.
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Old 25-03-2018, 10:29   #9
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Re: Trojan L16 voltage under load

We now had a technician look at the batteries. At first, he tested CCA with a digital tester and got out only around 600CCA which he decided was to low.

To make sure the problem was not in the charging system of the boat we took the batteries off to the shop and put them on charge overnight. I wasn't sure about that, because at that time the batteries were at around 14,4v (temp compensated charger in the tropics) and accepted less than 2amps.

The next morning, he tested again, sadly he didn't bring the digital CCA tester again but an older analog one that tested around 900CCA which he found fine but i think that's very low for a 380Ah battery.

He also tested specific gravity and all cells were in the green range (1,275 if i remember correctly) so he decided the batteries are fine.

Now we put them back in the boat and i'm not so sure. I feel like i spent a lot of money for a big bank that does provide less power than the old one. We'll head out to anchor this evening so i will check what's happening under normal use.

I'm also wondering if it is normal that these wet cells get quite warm when charged? When i've depleted them to 70% and then used our 55amps shore power charger they got quite warm. Not hot, but the old agm didn't do that. I hope that our 110amps alternator won't overheat these cells.

As said in the first post, these are not the normal L16H-AC cells that are widely used but the SPRE 06 415 (solar premium line) which are quite new and look like a replacement for the L16RE-B. Does anyone else have personal experience with batteries of this range? Is their high internal resistance normal behaviour?
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Old 25-03-2018, 10:55   #10
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Re: Trojan L16 voltage under load

What b. said. But also note that "good" and "bad" are sometimes only a few tenths of a volt apart, unless you have a calibrated or known-good voltmeter, it has to be suspected of being accurate only to 1/2 volt, which means a world of difference in "12" volt systems.

I would suspect that the digital tester the technician used is one of the new type that measures internal resistance in the battery, where the old analog style one (did it have a metal "cage" at one end?) was the traditional carbon pile actual load tester. If those batteries are supposed to be something new and different, especially, the results might differ.

The most reliable source of information would be to contact the manufacturer. Buy an inexpensive DC clamp ammeter, use it to check the charging output that is going to the batteries from whatever source. Check it when you start charging, and again maybe every 15 minutes because it WILL change. Then run those numbers by the manufacturer, along with what the batteries are doing (how hot, etc.) and try to get a grip on this with *numbers*. And yes, that may also mean getting a thermometer or a contactless IR thermometer.
But battery charging is all about physics, and physics is pretty much ruthless stuff. To say a battery is "hot" means nothing. To say it is 200F or 90C when charging at a 1/4C rate, that's something the support staff can give you a better response to.

Pursuing the real answers, rather than just throwing money into annual batteries, is absolutely going to be worthwhile.
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Old 25-03-2018, 11:14   #11
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Re: Trojan L16 voltage under load

I agree with SailorBoy...

Our golf cart batteries have a large sag when loaded with big loads. We recently got a washing machine that has a built in heater. When we run it off the inverter it will pull 85-90A (for about 45 seconds). Our batts will drop below 12V, but recover once the heater kicks off.

Just like Sailorboy, if I load my batts hard first thing in the morning they will sag to like 12V.. Been like that for 2 years.
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Old 25-03-2018, 11:20   #12
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Re: Trojan L16 voltage under load

Quick question to the Trojan specialists here.

We are thinking of replacing the 3x90 AmpHr 12V batteries in the near future.
So far we are set for a set of 6V Trojan wet cells to get the same AmpHr @12V we had before.

We have several solar cells which can charge via Mppt solar regulater.

Now here comes the question, it has happened that we could not go to the boat about 2000km away for about a year (while it also happened that we've been on board for almost a year :-) ).

With the gel type batteries I do not worry too much.

How about the wetcells? Would they cope if one assures that the elyctrolyte has been topped up before leaving and keeps them attached to the solar?

Thanks,

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Old 25-03-2018, 11:25   #13
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Re: Trojan L16 voltage under load

txg:
The electronic tester; e.g., Midtronics, only measures CA (marine, cold, JSI, etc., etc.). I use this to infer the health of the battery being tested since most 6V deep cycle battery manufacturers do not provide a tech spec for CA for these batteries. The Trojan SPRE 06 415 is no different. I have a $700 electronic load bank that measure amp-hours, but it is really not for field use. The point is, testing to determine the available Ahr insitu is difficult...the Midtronics tester only provides an indication of the health of the battery.

That all said, your SPRE 06 415 batteries have a 20 hour rate of 377Ahr or, 377Ahr/20A = 18.85A for 20 hours.

When you pull 130A; this amounts to 6.7 times the 20 hour rate. Significant voltage sag will occur but not quantitatively knowing the health of the batteries makes it hard to tell if the sag is excessive but experience shows me that they should not sag as much as reported.

However:
Quote:
When discharging with normal house loads of about 10amps they drop to 12,0v at about 70% according to the victron battery monitor.
Since the 10A is significantly less than the C/20 rate the voltage drop exhibited is definitely excessive.

I agree with the poster that was concerned that the shop filled the batteries with water (hopefully with distilled water!) that has diluted the electrolyte and I believe that this is probably the cause for the battery heating when being charged that they are experiencing.

Quote:
He also tested specific gravity and all cells were in the green range (1,275 if i remember correctly) so he decided the batteries are fine.
I really, really have a hard time accepting this value. Was the hydrometer reading temperature corrected? So this begs the question, how much electrolyte was spilled? Were the plates uncovered? If so, the uncovered plate material is essentially dead and you have lost capacity.

In short, the spillage and possible mechanical damage of your "new" batteries has altered the battery's characteristics so that they will not provide 377Ahr.

Hope this helps.
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