Electrolyte specific gravity anyone?

[Loafer]

Could be, although it comes back to my earlier question of at what point is the acid added. I've certainly bought motorbike batteries where the acid was either added by the dealer, or even in a pack for you to add yourself. It seems to me to make sense to add the acid as late as possible in the supply chain.

Agreed. Wish I could add it myself. Doesn't that constitute hazardous cargo though? Probably too expensive.

[nicknorman]

Agreed. Wish I could add it myself. Doesn't that constitute hazardous cargo though? Probably too expensive.

Surely no more hazardous than when it is put into vented batteries? In fact less so, I would have thought, because it can be in a sealed container.

[Loafer]

Nicknorman, sorry `i didn't answer this - no, I wasn't going to get a Smartguage in addition to my BMV600S.

 

It looks like a sensible bit of gear, and I would have one if it were a lot cheaper.

 

Consider this though:

 

At the moment I have my 600S well-calibrated initially, by telling it that I have 400Ah of battery capacity (not yet 450). After casually watching all the numbers, it is easy to determine that the SOC readings (upon discharge) are inaccurate. (Hence the Smartguage which claims to do a better job.)

 

With time though, I can readjust the total Ah figure and Charge Efficiency to reflect what is actually happening, i.e. I'll still see the same numbers during use. SOC included.

 

Does that sound even remotely intelligent?

 

ETA Gotta go now. Peeps coming for tea.

Edited February 4, 2015 by Loafer

[nicknorman]

Nicknorman, sorry `i didn't answer this - no, I wasn't going to get a Smartguage in addition to my BMV600S.

 

It looks like a sensible bit of gear, and I would have one if it were a lot cheaper.

 

Consider this though:

 

At the moment I have my 600S well-calibrated initially, by telling it that I have 400Ah of battery capacity (not yet 450). After casually watching all the numbers, it is easy to determine that the SOC readings (upon discharge) are inaccurate. (Hence the Smartguage which claims to do a better job.)

 

With time though, I can readjust the total Ah figure and Charge Efficiency to reflect what is actually happening, i.e. I'll still see the same numbers during use. SOC included.

 

Does that sound even remotely intelligent?

 

ETA Gotta go now. Peeps coming for tea.

Yes that sounds reasonable, if a little faffy! I know a good few folk who have such AH counting gauges and say "how can the lights possibly be going dim, I still have 80% SoC on the gauge" when their batteries are shagged. But you are more intelligent than that! Well that presumes you remember to decrease the AH capacity setting in 6 years time when the Trojans start to falter!

 

The AH counting gauges are not too bad if you routinely get back up to 100% SoC, but they seem to drift off quite a bit if you are just cycling between say 80% and 60%, whereas the Smartgauge is much better at coping with that kind of use, and of course automatically compensates for any reduction in capacity.

[dmr]

Replies to various above posts...

 

The Smartgage is worth every penny.

 

I believe that stronger acid reduces life expectancy of batteries so manufacturers are likely to add excess water rather than excess acid.

 

I have had a shot at working out how much the SG is reduced by adding extra water, had to make a couple of assumptions.

 

With a SG of 1.270 at the "correct" level, I reckon adding 100ml of water will raise the level by 6.9mm and reduce the SG to about 1.257.

 

Is the terminal voltage reduced by a similar factor??????

 

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

[Loafer]

Replies to various above posts...

 

The Smartgage is worth every penny.

 

 

I may one day soon request proper authorisation for release of funds for a Smartguage. I have read all the blah, and I agree that it must work well.

 

Trouble is, it's a bit pricey, when I've already got good monitoring. I'm a geek and a fiddler, so I enjoy fine-tuning the 600S to give what I think are the right numbers.

 

Each to his own tastes (or his own bad tastes)!

[dmr]

Yes but the Smartgage will enhance your geeky fiddling because you can then actually confirm that you have got the fiddling right.

It is expensive and it does lack a bit of style and flashness! It looks like it was produced by an engineer without a marketing department!.

 

There is something very satisfying about a simple direct readout of state of charge that always work.

I also like it because if I need to work away Gillie can easily take over with the engine running and state of charge monitoring.

 

I want to get an amp hour counter but fancy making one myself but have not found the time to do it yet.

 

.........Dave

[mad dog n' Englishman]

Good morning.

Can I ask your opinion of this unit "Ctek M100" to give a proper equalisation charge when off grid. I know it would mean running the genny to charge pairs of batteries separately but if it gives the correct voltage it would seem a small sacrifice to make. As it would be at most once a month or much less .

Any thoughts would be welcome.

Garry.

[nicknorman]

Good morning.

Can I ask your opinion of this unit "Ctek M100" to give a proper equalisation charge when off grid. I know it would mean running the genny to charge pairs of batteries separately but if it gives the correct voltage it would seem a small sacrifice to make. As it would be at most once a month or much less .

Any thoughts would be welcome.

Garry.

Hi Garry. The spec for the equalisation mode says 15.7v at 1.5A for 0.5 - 4 hours. So a good voltage, but at a very low current. When I EQ at 15.5v, my 450AH bank normally takes 6 - 10A. So I suppose,if you have 12v 110AH batteries it could work if you did one battery at a time, but very tedious and lots of genny running. It's also not clear what criteria are used to exit the mode (the mention of 0.5 to 4 hrs implies some automatic exit depending on something?)

 

For around £100 I think you would be better off getting a bench power supply that you can adjust the voltage on, and get probably 5A.

 

Edit: maybe this one which will give you 5A at 15.5v (adjustable) http://www.maplin.co.uk/p/100w-slim-bench-power-supply-n93cx

 

Or this one, a bit more fancy (I have one of these) http://www.maplin.co.uk/p/80w-switched-mode-dc-multi-voltage-slim-bench-power-supply-n27gg

 

They both have the advantage of being under your control, rather than some fancy algorithm, and have displays of voltage and current.

 

Cheaper,offerings available on eBay.

Edited February 5, 2015 by nicknorman

[Keeping Up]

I went into my local Maplin's and they had one similar to the first of those, with an almost identical spec, for £10 less. It will give 15.5v at up to 5A or 16v at up to 4.5A and it does the job just fine.

[dmr]

I am very naughty with my equalisation, I do it from the alternator (by adjusting the Adverc voltage) and so like to do it quickly to avoid running the engine for ever. I start equalisation once the charge current is down to about 10amps. When I increase the voltage to 15.5v the current goes up to about 25 amps, though drops down to maybe 15 quite quickly.

 

This slightly brutal equalisation does the job. I do not get massive water loss, the batteries do not get hot, and they are now over three years old,cycled everyday, and still looking good. I do make sure I have good ventilation.

 

Hence I think a 1.5 amp charger is way too small.

I Like the idea of a power supply but get a beefy one.

 

Charging pairs of batteries sounds tedious, get a charger/psu than can do the whole lot together (turn off anything in the boat that might struggle with 15.5 volts). The split pairs concept is Petes idea (and maybe mine) but I think its only worth doing if you are not willing or able to run an engine or generator and so need to use a "battery to battery" type charger.

 

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

Edited February 5, 2015 by dmr

[mad dog n' Englishman]

Hello, Nick, Allan and Dave.

Thanks for the link to Maplins and the advice. It has all sunk in and will be acted upon as soon as poss.

Cheers,

Garry.

[Loafer]

No sun here today, and no other charging employed. So right now, at 2123 hrs, here's what I'm seeing from 4xT105s:

 

Batts showing 12.14V with a 13A draw.(Laptop, telly and fridge) (That is unusually large here , added by laptop charging whilst in use.)

 

Ah consumed ('CE') =-92.0Ah

 

SOC says 83%.

 

Can't provide resting voltage 'cos we're using stuff. Which is EXACTLY what I'm interested in!

 

Other stats to follow, for those still awake!

 

PS Fridge now stopped, with 12.20V and 8.6A draw.

 

I am very naughty with my equalisation, I do it from the alternator (by adjusting ........

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

 

How often, Dave?

[dmr]

No sun here today, and no other charging employed. So right now, at 2123 hrs, here's what I'm seeing from 4xT105s:

 

Batts showing 12.14V with a 13A draw.(Laptop, telly and fridge) (That is unusually large here , added by laptop charging whilst in use.)

 

Ah consumed ('CE') =-92.0Ah

 

SOC says 83%.

 

Can't provide resting voltage 'cos we're using stuff. Which is EXACTLY what I'm interested in!

 

Other stats to follow, for those still awake!

 

PS Fridge now stopped, with 12.20V and 8.6A draw.

 

 

How often, Dave?

 

I used to be quite serious about equalisation, measuring lots of stuff and writing it all down, but I have got very laid back recently.

It feels to me like you can leave it quite a while, get a fair bit of sulphation, and still fix it with a good equalisation. (talking Trojans here, not sure this applies to the cheapo leisures).

 

in the summer we cruise most days so these is no problem. In the winter I sometimes think "the batteries aren't doing very well", maybe down to 50% or less by 5pm (engine time). so then I do a bit of equalising. Maybe every 4 to 6 weeks, maybe a bit less often. Sometimes if we are moving I will do a "mini equalisation" for a couple of hours before shutting the engine off. I rarely bother with the hydrometer. I did push it a bit too far last winter and needed a bit of 16v or so to sort it out (did use the hydrometer for that).

I also don't do the "8 hour charge" once a week, just 2.5 to 3 hours almost every day. We do have "washing machine days" when we maybe get 5 or 6 hours of engine running. I do tend to charge at 15v in winter, and drop this down to maybe 14.7 in summer (in addition to any automatic temperature compensation).

 

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

[Loafer]

I'm the reverse! I spent years being only slightly interested, now I'm thinking of taking notes!

 

Thanks for your musings. Got all that.

[cuthound]

I used to be quite serious about equalisation, measuring lots of stuff and writing it all down, but I have got very laid back recently.

It feels to me like you can leave it quite a while, get a fair bit of sulphation, and still fix it with a good equalisation. (talking Trojans here, not sure this applies to the cheapo leisures

 

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

Many moons ago at the dawn of my career I used to work on the DC Section of BT. We used to equalise big (15,500 AH) open lead acid batteries every 3 months, and "condition" them (fully discharge to assess actual capacity (using an antimony probe to assess charge on the negative plate) every 2 years. Those batteries has a 25+ year life expectancy.

 

Occasionally we would be called in to look at neglected batteries, typically badly sulphated due to being continuously undercharged. These would be charged at 2.7 volts per cell, until they began to gas, then left to cool before the process was repeated, as often as necessary until the sulphated battery would accept a charge. This would usually (but not always) break down the sulphation and return the battery to good health.

 

I would therefore equalise once every 3 months for healthy cells.

[Radiomariner]

Many moons ago at the dawn of my career I used to work on the DC Section of BT. We used to equalise big (15,500 AH) open lead acid batteries every 3 months, and "condition" them (fully discharge to assess actual capacity (using an antimony probe to assess charge on the negative plate) every 2 years. Those batteries has a 25+ year life expectancy.

 

Occasionally we would be called in to look at neglected batteries, typically badly sulphated due to being continuously undercharged. These would be charged at 2.7 volts per cell, until they began to gas, then left to cool before the process was repeated, as often as necessary until the sulphated battery would accept a charge. This would usually (but not always) break down the sulphation and return the battery to good health.

 

I would therefore equalise once every 3 months for healthy cells.

Back on the old days when much of my life was spent looking after Radio Station batteries, charging individual cells was not only possible but practical. I often 'rescued' a single sulphated cell this way. Then each cell in a battery of 6 cells were connected to the next by a lead bus on the battery top. Most of the batteries I see these days have the connecting bus inside the carcase. If anyone knows how to charge an individual cell, in this type of battery, in the fashion cuthound describes, please let me know, and I will try it.

 

Edited for punctuation.

Edited February 6, 2015 by Radiomariner

[cuthound]

Radiomariner, I am not aware of how you can charge individual cells in a sealed battery without butchering the case.

 

Modern batteries with the group bar enclosed in the case, especially VRSLA's, often fail either open or short circuit because the join between the group bar (pure lead) and the plates (often a lead/calcium alloy to reduce water consumption) corrodes. This allows the affected plate to drop into the battery.

 

The best performing batteries from a longevity viewpoint often use pure lead plates and also plates which are thicker than average. This is especially true if the batteries are used in ambient temperatures over 25 decrees C.