Electrical Musings

[twistedtree]

Originally Posted by Dockhead

Thanks, I think this is a very good suggestion, and I strongly suspect that you are right, and that I have not gotten rid of the sulphation from my discharge incident last month. It would explain everything, wouldn't it? It's very good that I will now have the Honda generator which I will simply run continuously for a while when I get back to the boat next week.

A bit of thread drift - should I or should I not equalize all 8 batts at the same time? The Victron manual suggests doing them one at a time, which would be a PITA. And how much equalization is too much? Corrodes the cathodes, doesn't it?

OMG, we're not going to get back into stray and circulating currents in parallel battery banks, are we? But more seriously, here's what I'd suggest from experience and reading...

- I'd EQ in parallel, but monitor the SQ in all cells as it proceeds. I'd only consider breaking out individual batteries if there are one or two real stragglers who's SG is proving difficult to restore. By isolating the stragglers, you can continue to EQ them without torturing the other batteries. In my experience there are always stragglers, but never enough to warrant breaking down the battery bank.

- You should EQ until the SG is both within spec AND has plateaued for an hour or more. It's not unusual for cells to settle out with SG higher than specs, so it's largely an exercise in "hunting" for the SG where the discharge chemical reaction has been 100% reversed.

- Keep an eye on fluid level and fluid temp to be sure you don't run any cells dry or overheat them. Suspending the EQ, then restarting again later is fine if things need to cool off, or you need to go get dinner or whatever. When you restart you will obviously need to return the batteries to full charge before the EQ will get going again, but that shouldn't be too hard.

- I wouldn't worry about corrosion. I think it's really only a problem with a system that chronically overcharges the batteries. And besides, the sulfation will kill your batteries way before corrosion, so accepting some risk of corrosion in order to eliminate sulfation is a worthy tradeoff.

- As for how long to EQ, it's really hard to say. I'd monitor SG and let that drive the length of time since that's the only way to measure the reversal of the chemical reaction. When I had a problem with my bank, it took 24 hours of EQ to straighten it out. That was broken up over a couple of days, but it went on for a LONG time.

Once you get the SG up where it should be, you can use those measurements to test whether your normal charge regime is actually bringing your batteries back to full charge. I'll bet it isn't, and that your sulfation is not just the result of one discharge event, but actually an accumulation from regular deficit charging. It takes a surprisingly long duration of acceptance charging to really get a battery fully charged. Thick plated batteries like the big Surrettes make matters way worse. You may find yourself playing with charge voltages etc to get a charge protocol that is the right balance of generator run time, solar/wind charge, etc. and batteries that are actually being returned to full charge (as measured by SG and nothing else) at least once a week.

Good luck and let us know what you find. Meanwhile, I'm going to try and measure a circulating stray current.........

[s/v Jedi]

And they are the regular flooded batteries I assume...

I know you guys know all this, but let me add it for future readers

Here is what to do:

Fully charge the bank using the Victron charger so that the charger is in float for an hour or so. No shortcuts here.

Measure the specific gravity SG of each cell and note that down (logbook). Mark the weakest cell of each battery and the weakest cell of all Note that, plus local temperature in the logbook too. Put a sink half full of water and toss all the battery caps in there, i.e. leave them off the batteries.

Top up the batteries with distilled water once more.

Put some paper towel (2 layers) over the batteries so that all the openings are covered.

Now disconnect all 12V loads and switch the charger to equalize mode.

Go wash all the battery caps with detergent and plenty rinsing. Shake water out of each and let air-dry.

By now the batteries should be boiling. You must be able to hear that and even feel it when touching the sides (you feel bubbles popping). The sides also get warm. I point a fan at it so that there can never be a too high concentration of hydrogen (is impossible to become dangerous high so no worries), plus to cool it a bit.

After an hour of boiling, kill the charger, put the paper towels aside and clean up any acid drops. Now, measure and note down the SG of every cell again. You want to see two things:

1. increased SG
2. more uniform readings, i.e. the weak cells must have improved more than the others.

If point 2 is true, it means you're good but not ready yet. Put paper towel back over openings, boil for another hour and repeat this SG test again and again, until:

If point 2 shows that the SG does not improve anymore... not even on the weak cells, then you are done. The SG readings you have now are the true ones at this point in time. Clean up, put all the caps back etc.

Now, If you're not happy with the final readings, you have one last ace to play. Put on loads and switch off any charging source. Do this so that you can exactly repeat this procedure and write it down in the logbook (which loads, time etc). Check your battery monitor which should have reset itself to 100% capacity after the last full charge/equalize. The goal is to do a deep discharge, say down to 40% or even 30% capacity left.

After that... next day at the earliest, charge the bank again to at least one hour float charge and repeat all above. This cycle will restore a lot of capacity.

cheers,
Nick.

[ebaugh]

I have 12 T105's that 24 hours of equalization will not recover to spec SG. They have suffered for 18 months of chronic undercharging with only quarterly equalization. It's a real PITA using a generator. They still work OK, bit I estimate capacity is reduced to 50 to 60 percent of new.

At 100 to 110 degrees F, I was afraid to go past 15.3 volts. Ambient is 95 or so with the generator running, so there is no such thing as cooling them off.

Mine do exhibit the phenomenon mentioned I think in the Rolls manual where an hour or so into the process, voltage actually drops for awhile before it starts to rise again.

Good luck!

[ebaugh]

Originally Posted by s/v Jedi

And they are the regular flooded batteries I assume...

Now, If you're not happy with the final readings, you have one last ace to play. Put on loads and switch off any charging source. Do this so that you can exactly repeat this procedure and write it down in the logbook (which loads, time etc). Check your battery monitor which should have reset itself to 100% capacity after the last full charge/equalize. The goal is to do a deep discharge, say down to 40% or even 30% capacity left.

After that... next day at the earliest, charge the bank again to at least one hour float charge and repeat all above. This cycle will restore a lot of capacity.

cheers,
Nick.

Never tried that ace in the hole trick....maybe the guy that gets the 10 T105's in Grenada can try it? I'm keeping 2 for a starting battery, but the rest are free to a good home or are headed to the recycler.

[noelex 77]

Originally Posted by s/v Jedi

Here is what to do:
Nick.

I can feel the force is stronger already.
Great post Nick

[s/v Jedi]

These Trojans are really lousy starter batteries. A couple of years ago I did the very best thing possible to do with starter batteries: I replaced mine with Odyssey thin-plate AGM starter batteries. Wow. You can leave this without a charger for a year, come back and just start the engine with them, no joke.

The catch is their price... but guys like Appie @ Marinewarehouse give discount.

ciao!
Nick.

[ebaugh]

Originally Posted by s/v Jedi

These Trojans are really lousy starter batteries. A couple of years ago I did the very best thing possible to do with starter batteries: I replaced mine with Odyssey thin-plate AGM starter batteries. Wow. You can leave this without a charger for a year, come back and just start the engine with them, no joke.

The catch is their price... but guys like Appie @ Marinewarehouse give discount.

ciao!
Nick.

The monthly...annual? Cruising budget is blown. But I was planning on replacing them with AGM someday. I think due to size constraints they will need to remain 6V golf cart sized, or perhaps 2 Group 24 sized 12V will fit. Does it matter for AGM? Starting 120 HP Lehmans.

[s/v Jedi]

Originally Posted by ebaugh

The monthly...annual? Cruising budget is blown. But I was planning on replacing them with AGM someday. I think due to size constraints they will need to remain 6V golf cart sized, or perhaps 2 Group 24 sized 12V will fit. Does it matter for AGM? Starting 120 HP Lehmans.

These Odysseys are so awesome you can go with half your current Ah capacity. The ones I got were different sized, but I got 2 batteries instead of the 4 I had before (!! yes, 4 starter batteries... now 2!!)

cheers,
Nick.

[twistedtree]

I like the paper towel trick and will need to try that.....

[Dockhead]

Originally Posted by s/v Jedi

These Odysseys are so awesome you can go with half your current Ah capacity. The ones I got were different sized, but I got 2 batteries instead of the 4 I had before (!! yes, 4 starter batteries... now 2!!)

cheers,
Nick.

4 starter batts?? What kind of motor are you starting?? I have one 10 year old truck battery for my 100hp Yanmar which still tests well (I use an Argo internal resistance meter) and starts the main engine in any weather.

[nigel1]

Originally Posted by Dockhead

4 starter batts?? What kind of motor are you starting?? I have one 10 year old truck battery for my 100hp Yanmar which still tests well (I use an Argo internal resistance meter) and starts the main engine in any weather.

Was thinking the same, what you got in there Nick, a 12 legged Sulzer engine??

And, thanks for the post on equelising the batteries, nice and simply put

[s/v Jedi]

There were four Lifeline Gel batteries in parallel. It's one bank for both engine and genset. Engine is just a 4-cyl. Yanmar so nothing special.

The idea behind it must have come from a tech that worked for the previous owner. I have no clue why they did this.

Now I have the two Odysseys and there is a 1-2-both-off switch there so that I can isolate a bad battery. I can also switch house batteries to the starters if needed.

Related: standard alternators can kill batteries if motoring for long periods, as their internal regulators output 14V all the time.

Lesson: if you're motorsailing or motoring for a long period, pull the field wire (blue) from the alternator.

cheers,
Nick.

[ebaugh]

Originally Posted by s/v Jedi

There were four Lifeline Gel batteries in parallel. It's one bank for both engine and genset. Engine is just a 4-cyl. Yanmar so nothing special.

The idea behind it must have come from a tech that worked for the previous owner. I have no clue why they did this.

Now I have the two Odysseys and there is a 1-2-both-off switch there so that I can isolate a bad battery. I can also switch house batteries to the starters if needed.

Related: standard alternators can kill batteries if motoring for long periods, as their internal regulators output 14V all the time.

Lesson: if you're motorsailing or motoring for a long period, pull the field wire (blue) from the alternator.

cheers,
Nick.

You can get fancy with external regulators....or just replace them with ones that have adjustable voltage regulators. My trawlers are set to 13.2V. Charged some if the battery was discharged, otherwise they floated where they were and the alternators took all the loads.

Leese Neville has a nice 90 amp single pulley internally regulated alternator that does this for about 200.

[noelex 77]

Originally Posted by s/v Jedi

The idea behind it must have come from a tech that worked for the previous owner. I have no clue why they did this.

Did they originally run the anchor winch from the start batteries? Just a thought, otherwise even 2 is overkill.

[s/v Jedi]

Originally Posted by noelex 77

Did they originally run the anchor winch from the start batteries? Just a thought, otherwise even 2 is overkill.

I suspect it had to do with the alternator... also the reason for GEL I think.

cheers,
Nick.