Battery Equalistion - How many times?

[Richard10002]

3 x New cheap open lead acid batteries in March, 110Ah each. No mains, so engine and generator charging only. Generator charging via 80A Sterling inverter charger.

 

Generally discharged to about 55%, occasionally 50%, and probably charged to about 85%, most times.

 

Since late October, noticed not really holding a charge to the point where use of about 50Ah in a day results in monitor showing 50% discharge, voltagearound 12.2V.

 

So I decide to try the equalisation/de-sulphate on facility on the Sterling. This charges at 15.5V for up to 4 hours, and Sterling suggests it might take a few goes, and it might not work.

 

Neve done tho before but, from the manual, I am expecting it to run at 15.5V for as long as it takes to blow the sulphate off, then the voltage will drop as the capacity rises dramatically, at which time, I can revert to the normal charging setting.

 

I ran the desulphation for 3.5 hrs yesterday, then 4 hrs today - the battery caps are off, and the cells are all bubbling away, batteries not getting hot. But the voyage remains at 15.5V, and the capacity last night and tonight remains poor.

 

How many times could I run the desulphation setting fr its 4 hours, before calling it quits, and accepting the batteries are knackered?

 

I'm definitely giving it another go tomorrow but, after that, perhaps £210 for 3 new batteries, and perhaps an equalisation every couple of weeks or so.

 

Thanks for any help,

 

Richard

[by'eck]

3 x New cheap open lead acid batteries in March, 110Ah each. No mains, so engine and generator charging only. Generator charging via 80A Sterling inverter charger.

 

Generally discharged to about 55%, occasionally 50%, and probably charged to about 85%, most times.

 

Since late October, noticed not really holding a charge to the point where use of about 50Ah in a day results in monitor showing 50% discharge, voltagearound 12.2V.

 

So I decide to try the equalisation/de-sulphate on facility on the Sterling. This charges at 15.5V for up to 4 hours, and Sterling suggests it might take a few goes, and it might not work.

 

Neve done tho before but, from the manual, I am expecting it to run at 15.5V for as long as it takes to blow the sulphate off, then the voltage will drop as the capacity rises dramatically, at which time, I can revert to the normal charging setting.

 

I ran the desulphation for 3.5 hrs yesterday, then 4 hrs today - the battery caps are off, and the cells are all bubbling away, batteries not getting hot. But the voyage remains at 15.5V, and the capacity last night and tonight remains poor.

 

How many times could I run the desulphation setting fr its 4 hours, before calling it quits, and accepting the batteries are knackered?

 

I'm definitely giving it another go tomorrow but, after that, perhaps £210 for 3 new batteries, and perhaps an equalisation every couple of weeks or so.

 

Thanks for any help,

 

Richard

 

Even if you are working on standing volts to determine battery SOC, its likely your estimations are optimistic. Given that premise you may have been taking them below the 50% SOC generally agreed as the max discharge for anything approaching a decent life span. Add that to the even more relevant estimation of the perceived 85% charged SOC and they probably are knackered.

 

I would give it one more de-sulphation cycle then call it a day if no substantial improvement in capacity.

 

Remember as mentioned by Gibbo, each time you under-charge a battery its capacity is reduced. If you continue the regime you end up with battery capacity in a spiral decline.

 

With a new set of batteries I would run the generator/Combi for longer until it at least goes into float mode, unless of course a long days cruising achieves the same.

[dor]

Your regime is the classic route to knacker a set of batteries in six months or so. I know - I've been there. I now like to think I know a bit more about battery management and expect to get 3 or 4 years out of a set of batteries (no landline or generator).

 

I have got some more life out of a set of batteries that were behaving as you describe. I put each one on an 'intelligent' charger for several days, followed by about 12 hours at 16V. I did get another years use out of them, although they were never as good as a decent set.

 

As by'eck suggests, give it another go, maybe two. But after that give up on them and put it down to experience. You need to be getting those batteries up to 100% charged every week at the very least. If you are discharging to 50-55% on a daily basis then reconsider your power usage. LED lights can make a big difference (half a dozen 20W halogens might look nice, but they are drawing 10 amps).

[smileypete]

If you have space then how about put the 3 batts to one side and put 3 new ones in.

 

Then float the old batts on solar power, try a desulphator (Courtiestown do reasonable ones) or do a bit of equalisation while charging the new batts.

 

For living aboard without shoreline I'd try to arrange so part of the bank can be isolated and taken 'offline' for 100% charge, EQ etc to restore capacity.

 

My gut feel is that cheap leisure batts sulphate slower than semi traction batts but are a lot harder to desulphate.

 

cheers, Pete.

~smpt~

[dmr]

You really need a hydrometer to find out what is going on.

Charge batteries fully, measure specific gravity (SG), then equalise and check SG every hour. Equalisation is complete when SG stops increasing.

It is said that if you do not fully charge often then the sulphate gets harder, and so is harder to remove. I reckon this is true.

You may need more than four hours equalisation to sort things out. You could maybe even try 15.8 to 16 volts if the charger lets you but make sure this does not kill any equipment on the boat.

It may be that the sulphate is so hard it just won't shift, or the plates might be corroded away which has reduced the capacity.

 

With your next set of batteries try to do a big charge (8 hours) every week, and also check SG maybe monthly....If SG is low when fully charged then its time to equalise. I suspect equalisation does reduce battery life itself, but not nearly as quickly as sulphation.

.....and its caps on during equalisation unless you have clever caps than recombine the hydrogen.

 

............Dave !

[MikeV]

Or they just could have been crap batteries to start with! I bought 4 batteries eighteen months ago and they have been regularly charged to 100% and rarely discharged below 75%, but are still showing the classic symptoms of sulphation. Another new set next year I think!

Edited December 31, 2012 by MikeV

[dmr]

Or they just could have been crap batteries to start with! I bought 4 batteries eighteen months ago and they have been regularly charged to 100% and rarely discharged below 75%, but are still showing the classic symptoms of sulphation. Another new set next year I think!

 

If you are a liveaboard without a mains hookup then 18 months is good!

Big question is...how do you know that you charged to 100%...most instruments, even including the venerable Smartgage, do not get this right

 

Technical note before Gibbo shouts at me....A battery with any degree of sulphation will show every sign of 100% charge even when its less than 100%.

This is because it is fully charged in its current state...only equalisation or other special charging can get back to the true 100%

 

...........Dave

[Richard10002]

.....and its caps on during equalisation unless you have clever caps than recombine the hydrogen.

 

............Dave !

 

I've read a few things about equalising/desulphation, and all have said take the caps off - I'm presuming this is a safety issue, to do with pressure and overflowing?

 

Why caps on? It sounds like you are suggesting that the acid evaporates and dilutes the liquid, but what about the risk of exploding batteries?

[dmr]

I've read a few things about equalising/desulphation, and all have said take the caps off - I'm presuming this is a safety issue, to do with pressure and overflowing?

 

Why caps on? It sounds like you are suggesting that the acid evaporates and dilutes the liquid, but what about the risk of exploding batteries?

 

I am pretty sure its caps on, but will do a search on the www.

A few people fit "hydrocaps" or "Miser Caps" and I believe its these that have to come off

Equalisation is really only like a normal charge but a bit harder.

The caps always have a small vent to relieve any pressure.

All charging produces a bit of Oxygen and Hydrogen, equalisation produces a bit more.

What is important is to ensure good ventilation during equalisation, remove the battery box lid unless it is very well ventilated etc.

Our batteries are in the engine room so I try to have a side hatch open and often use a fan to keep the air circulating.

 

..........Dave

[MikeV]

If you are a liveaboard without a mains hookup then 18 months is good!

Big question is...how do you know that you charged to 100%...most instruments, even including the venerable Smartgage, do not get this right

Not livaboard, although we were cruising for 6 months this year. We rarely did less than 3 hours cruising per day and SmartGauge usually showed 100% after an hour or two. Final charge current at the end of cruising was typically 5-6 amps into a nominally 440Ah bank. So not technically 100%, but pretty close!

 

But mostly my comparison is with the previous batteries which were on the boat when I bought it. I don't know how old they were but they have been giving me usable, if slowly degrading, service for 4 years. The new ones have degraded very quickly to a level where I doubt they would support our modest needs next season. I might bring one off the boat and stick it on the bench to see if an equalisation charge does any good, but I'm not hopeful!

[dmr]

Not livaboard, although we were cruising for 6 months this year. We rarely did less than 3 hours cruising per day and SmartGauge usually showed 100% after an hour or two. Final charge current at the end of cruising was typically 5-6 amps into a nominally 440Ah bank. So not technically 100%, but pretty close!

 

But mostly my comparison is with the previous batteries which were on the boat when I bought it. I don't know how old they were but they have been giving me usable, if slowly degrading, service for 4 years. The new ones have degraded very quickly to a level where I doubt they would support our modest needs next season. I might bring one off the boat and stick it on the bench to see if an equalisation charge does any good, but I'm not hopeful!

 

I suspect that 3 hours every day, or even 4 hours every day, will not be enough to keep the batteries at 100%.

We were maybe doing more like 6 every day over the summer and that did keep ours at 100%, but as soon as we had a few easy days, or a day off, they start to slip. The 5 or 6 amps also does not really suggest 100% charge, but once a bit of sulphation sets in even a low tail current does not indicate a 100% charge, just a "full" charge if that makes sense. It really does take a lot of hours to get the last few percent of charge done.

Have a go at a big equalisation, its not going to bring them back like new, but should improve things.

 

.........Dave (struggling to get through the winter even with a set of Trojans)