Trojan L16 REB bank - cell issue

Surfpath · September 2018

At 4pm today i noticed that my 48v, 8 battery, 3 cells per battery Trojan L16 REB bank, drew down to 47.3 volts last night (what's that? 40% SOC?), and almost the same voltage the night before.

I performed a brief EQ and noticed lots of normal bubbling activity from all cells, with the exception of no bubbling in the middle cell on Battery three. Also the SOC in this cell was almost non existant, and the water level in the cell was significantly higher than any other cell in the bank. I checked about 12 other cells in the bank - all were a healthy 1.275 to 1.300.

The bank is 6 years old. For the first 5.75 years my average drawdown has been to about 75% SOC. Then from May to July this year, to about 55% because of an old inefficient fridge. After I got a new inverter fridge in July my lowest voltage has been 49.3v, with an average SOC drawdown of around 80%. That is, up to 2 days ago.

Funds are VERY tight now. How long can I last with my disabled bank? I can't see us being able to afford another battery purchase until December? Such a bummer. Thoughtful suggestions are appreciated.

Estragon · September 2018

Depending on your inverter, and range of adjustability in charging sources, you may be able to get by on a 42v nominal bank for a while.

Just adjust charging sources down in voltage accordingly, and remove the offending battery. Before doing so, it might be interesting to see if, while bulk charging, the bad cell gets hot (or better yet, try charging the bad battery separately if you have a 6v source).

Dave Angelini · September 2018

I don't think that will work Estragon. Too much delta. The method you describe is for the 2V cell L16 and larger 2V batteries.

There was a topic about the "smart carbon" Trojans failing at the same time as the regular not so smart Trojan L16's with an installer group I work with. Marketing hype is out there.

In a pinch Surfpath you can substitute another L16 or even a golf battery for awhile. The charging will not be optimum with a smaller golf battery but it will be alot better than what you have now.

Surfpath · October 2018

Dave,
My REB s are the version just before smart carbon came out. So I guess they are the not so smart type.

I can get my hands on a new or almost new 200 amp hr golf cart battery. With the new fridge we've dropped consumption considerably, so perhaps this will be ok.

Just to confirm. I checked sg in that cell again. i see practically no movement in the gauge. Tomorrow morning I will look at the down draw.

Surfpath · October 2018

Hi Estragon, I have an outback 48v to 230v inverter

Estragon · October 2018

Dave may well be right that limping by at 42v nominal won't work. It would definitely work better with 2v.

FWIW, my OB 48vdc 120vac inverters have a min LBCO of 9x4=36vdc. Default is 10.5x4=42v. It ain't pretty, but would likely work in a pinch at 42v nominal.

Putting in a GC battery temporarily isn't a bad idea either.

BB. · October 2018

2x 6 volt @ 200 AH batteries in parallel to replace one 6 volt @ 370 AH battery should be a good fit for a temporary fix. Just monitor the specific gravity and water levels in the string to see that they play nicely together.

Bill

Surfpath · October 2018

Ok, so 2 better than one?. I'll have to research how to wire it all up.
I hope that I can get good use out of them.

That battery (#3) always had higher Sg's. Perhaps that's why it was the first to go.

Our night time power use is pretty low now with the new fridge. Wild guess....Maybe 1 to 1.5kwh? If I went with one golf cart battery could i do it, or would it compromise the rest of the bank?

I generally don't have to worry about getting enough sunshine, just the odd very rainy day.

Surfpath · October 2018

Estragon.
Is there a problem if the bad cell gets hot when bulking?. We are not home for most of the day these days Only on the weekend s. days

I don't want a runaway issue on my hands, if you know what i mean

Estragon · October 2018

One mode of failure is when plate material sheds enough to the bottom of the cell to cause a short. While charging, current gets used to heat up the short, which heats up the battery. Obviously not a good thing, so if it's happening, the battery should be taken out of service.

If that battery always had higher SG, it may well have had more grid corrosion, and failed short.

Dave Angelini · October 2018

Whatever you decide, it should be very temporary!
This is full time offgrid? Things can snowball into loss of power or worse. You can't just go somewhere else right?
Find the money! Good Luck!

Photowhit · October 2018

You can also just leave it as it is!

This should work until a catastrophic failure in the cell shorting. Unless you have multiple string of batteries, the single bad cell shouldn't draw down any other batteries...

BB. · October 2018

I would personally, be hesitant to leave a known bad cell in a cycled series string.

The exact "final" down the road is unknown. I would not trust such a battery unless acid leakage, fumes, or fire does not endanger my family or the greater property.

Bill

mike95490 · October 2018

A battery with a internal shorted cell, is giving you it's due warning. Ignore it, and it might just sit there for another 20 weeks, or it's resistance may change, start boiling the acid and melt down the case of the battery. The best outcome is that it does nothing, anything else it's likely to do, will be messy.

Cheapest way out is with a pair of golf cart batteries, paralleled together to emulate the 6v 400ah battery that is sick.

The battery shorting out, is generally the sump in the bottom is full of cell debris ( some batteries have a 3" sump just for shed plate material) and that layer of loose fluffy conductive material sits, semi floating in the acid, conducting power, till it does something else.

Surfpath · October 2018

Thanks for the heads up. This morning the bank voltage was low again - 47.8v (although at midnight it was a respectable 50.2v - go figure). Again, I checked and the SG was almost non existent in that cell. Tonight when I get home, I am also going to check all the other SG's (I just checked half before) - to make sure I have no other bad cells.

Even though money is tight, in the next day or two I will get the golf carts: 2 Trojan 105's 225amp hrs ea. (I have no quick access to any used or even new L16's).

Can someone kindly sketch how I am going to cable up the new golf carts into the existing string (ie. a parallel within a series)

What about the cables? Do I have to get exactly the same gauge as the rest of the bank?

if the golf carts are 225amphrs each, should I also change the advance charge programming on the Outback?

I really appreciate the thoughtful suggestions.

Surfpath · October 2018

Again, do I really need two Golf Carts? I have a very efficient fridge now (0.9 Kwh/day) and don't draw much at night. Just double checking.

Photowhit · October 2018

If all you have done is a "brief equalizing", at least do a long corrective equalizing before spending the money.

If it's on the scale anywhere, run an equalizing charge at 64 volts (or what ever is suggested by Trojan) for a couple hours and see if there is improvement, then continue checking each hour until there is no improvement. If it's on the scale and quits coming up but is close I would and am currently using mine. I am pretty sure mine was intentionally poisoned but I have a single cell that would go above about 1.255 but the rest all run near 1.3. I can't recall how long this cell has been 'bad' but it's electrolyte was dark about a year after it was installed (I worked security and lived in a playground for adults)

The battery is over 7 years old now and it's been at least 2 years now that the cell has been running low.

BB. · October 2018

Using one golf cart battery drops your bank from 400 ah to string 225 ah... Nearly 1/2 capacity.

Also, when you recharge, the one GC battery will probably over charge (half size battery in series witha bunch of larger batteries).

Your choice... Keep an eye on everything (make sure the GC battery does not overheat or boil dry).

Otherwise, connect 2 GC batteries on parallel (+ to +, - to -) to make a single 6 volt @ 450 AH battery.

Then remove the bad battery and connect this pair in its place.

If you are still not sure, ask again for more details. Doing it wrong can ruin your day.

Bill

Estragon · October 2018

> @Surfpath said:
> Again, do I really need two Golf Carts? I have a very efficient fridge now (0.9 Kwh/day) and don't draw much at night. Just double checking.

You could put in one GC, with ~1/2 capacity of an L16. I've never tried it, so if you do, please let us know how it goes. I think the GC would just contribute less current to loads, and take less current charging than others in the string, but I really don't know.

Surfpath · October 2018

And my other question is, in the interim before I install the GC batteries, shall I put the outback temp sensor on the affected battery? That way, if it does heat up the c controller may throttle back ( i would imagine it would at least)

BB. · October 2018

In series, all batteries see the same current.... You either will get ~2x current on the single GC battery in series... Or you will get 1x current for the GC battery and ~1/2 the charging current for the rest of the battery string (i.e., 400 AH @ 10% = 40 amps recommended charging, 225 AH @ 10% rate of charge = 22.5 amps for a single GC battery).

You can try it and see what happens... More or less, the GC battery will be "more sensitive" to high current charging when >~80-90% state of charge (less efficient charging, more current turned into heat).

Depends on how you program the charge controller (reduced current charging, drop voltage set point, etc.).

One 6 volt "undersized" battery in series with the rest of the 7 full size 6 volt batteries--There is no really "good way" to make them play nicely together without (at least) keeping an eagle eye on the rest of the batteries in the string.

-Bill

Estragon · October 2018

> @Surfpath said:
> And my other question is, in the interim before I install the GC batteries, shall I put the outback temp sensor on the affected battery? That way, if it does heat up the c controller may throttle back ( i would imagine it would at least)

You may want to check your CC manual. It should reduce voltage as temp rises, but may have a limited range as a reading "sanity check". If so, it might (eg) reduce voltage up to 120°f, but not compensate for higher temps (on the assumption readings outside the range are faulty).

If it does work and the bad cell gets hot, the good batteries may end up undercharged at the lower compensated voltage.

mike95490 · October 2018

Here's a sketch how to pull the bad battery ( 4volts) and parallel 2 cheap golf cart batteries in it's place,

likely the safest way to keep your pack intact till you replace the whole thing.

Image: https://us.v-cdn.net/6024911/uploads/editor/8p/hmilby1j96kt.png

sawmill · October 2018

I went through something very similar last year. 1 cell failure in a Trojan 8 L-16 24 volt bank. I bought a cheaper L-16 US Battery to replace the bad one. With nothing to lose I tried (aggressive) charging the individual battery in an attempt to save it. The bad cell would never come within 50 points of the other 2 cells.

It wasn't long before other cells began to show lower SG readings. I ended up selling the 9 L-16s for scrap (.39lb) and using the proceeds to off set a 24v GB fork lift battery. Only time will tell if this battery is superior to other flooded ones. I only know two things for sure. It's great not having all those inter connect cables and I will never have another Trojan battery.

mcgivor · October 2018

Surfpath said:

At 4pm today i noticed that my 48v, 8 battery, 3 cells per battery Trojan L16 REB bank, drew down to 47.3 volts last night (what's that? 40% SOC?), and almost the same voltage the night before.

I performed a brief EQ and noticed lots of normal bubbling activity from all cells, with the exception of no bubbling in the middle cell on Battery three. Also the SOC in this cell was almost non existant, and the water level in the cell was significantly higher than any other cell in the bank. I checked about 12 other cells in the bank - all were a healthy 1.275 to 1.300.

The bank is 6 years old. For the first 5.75 years my average drawdown has been to about 75% SOC. Then from May to July this year, to about 55% because of an old inefficient fridge. After I got a new inverter fridge in July my lowest voltage has been 49.3v, with an average SOC drawdown of around 80%. That is, up to 2 days ago.

Funds are VERY tight now. How long can I last with my disabled bank? I can't see us being able to afford another battery purchase until December? Such a bummer. Thoughtful suggestions are appreciated.

Six years at what temperature? Higher temperatures can reduce life expectancy dramatically but realistically six years is not that bad considering the specs are often based on ideal conditions, 2200 cycles for LA chemistry is respectable, remembering a cycle is a cycle, they do die of old age, usually faster than claims suggest, it always starts with a single cell, or so it seems, then manifests into total failure, a slow death which is unavoidable.

Surfpath · October 2018

Thanks for the sketch Mike. I get the drift. But I'm wondering how to make the wire 'junction.' Ie. where one cable turns into 'two' between the old 6v battery and the two smaller new ones.

I am guessing I need to use the same cable size for the new wiring as the old (4ga AWG I believe).

I have had my L16's for just about 6 years at an average of about 27-28 degrees C (around 80F).

Surfpath · October 2018

Here's the cycle chart for this model of Trojan-REB (the 'old' one). When I think about it again, my average drawdown has been to about 70% (not 75 as I originally stated above), so I think Ive gotten an OK-ish deal out of them. They were my first bank - so I think I did not murder them.

As I mentioned before I am hoping to get a little more time out of the remaining seven (at least 9 months would be perfect). The other cells have been performing fine, from what I can tell.

mike95490 · October 2018

To make the connections, you stack 2 jumper cables on each of the 400ah battreies, and a jumper goes to each golf cart battery, sorry I didn't draw it more plainly. You already have 1 jumper, if it's not long enough, make the battery taller with a chunk of wood under it.

Surfpath · October 2018

Mike, like this? Hopefully the image attached. The other small issue is that my existing batteries use the L shaped "post" terminal, while the T105's will likely have a vertical threaded post and wingnut. The cabling is not long so it'll be harder to bend onto the new vertical post. I may have to get 4 new cables that fit the job.

Surfpath · October 2018

Image: https://us.v-cdn.net/6024911/uploads/editor/fh/2xqm0rd5cq10.jpg

mike95490 · October 2018

yeah, you may need new cables to do the length and bends

Trojan L16 REB bank - cell issue

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