Model Boat Mayhem
Technical, Techniques, Hints, and Tips => Batteries & Chargers => Topic started by: Bob K on November 27, 2017, 12:43:57 pm
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A quick question about batteries. I use either SLA or NimH, so far without any problem. However, just like car batteries which gradually decline in performance over the years, should I replace my model boat batteries on a precautionary basis when they have provided years of useful service. Example: My HMS Skirmisher has a 10Ah SLA, and is used around once a week for two or more hours of continuous usage for over six years. I sail twice a week, so my most popular boats all get a lot of use.
Should we wait until a noticeable reduction in run time is noted after the usual full charge, or replace them after X recharge/use cycles. As I say I do not have any problems with them, always buying good quality batteries and looking after them, but there must be limits.
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Hi Bob, My adage is "if it ain't broke don't fix it" and the same applies to the car battery, if I start getting starting problems and the battery is five years old or more that's when I replace it, it's rare that a battery in a model will suddenly fail so you will know in good time that your sailing times are getting shorter, till then save your pennies for mince pies. ok2 O0
Joe
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Thank you Joe. Sounds like good advice.
My many batteries have all seen countless hours of life, and been recharged many times.
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Hi Bob I have a couple of Deac batteries they must be 35 years old and they still take a charge and drive a motor.
Roy
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on my sub i use sla batteries. it used most Sundays.
i have a rule of now that a replace them 1 1/2 to 2 years as don't want to risk a model over £15 and then use them for testing of aux power supply but that just me.
that remind to i better replace mine soon lol
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Hello Bob
Check the Voltage just after you have recharged the battery. I have 2 x 12v 5 AHr in my Puffer and that has been going strong for four years and I am sure the batteries were in something else before that. Normally a 12v SLA will charge to 13V, or maybe a bit over. One of my Puffer Batteries will now only charge to 11V so it is telling me it has had enough. It has been a gradual decline however so you will get plenty of warning.
John
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The Opportunity rover landed on Mars, solar powered and reliant on lithium-ion rechargeable batteries. The expected mission life time was 90 days: it's a harsh environment, after all. Cold during the day, freezing at night.
Nearly fourteen years later (5000 battery-cycles and counting) she's "doing OK".
...I think I'd swap out a boat battery only when it doesn't read the expected charge after a night on the charger. :)
Andy
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I use SLA batteries exclusively in my boats and have never had one fail completely. As they age the run time starts to decrease, and when it reaches a point where the run time is too short for a decent sail I retire them. My oldest battery is over 8 years old and still performing well. I keep a record of each time they are charged, and ALWAYS store them in a fully charged state. One feature of SLAs that I like is that they can "bounce back" as it were. If the battery level drops, and the boat stops, or slows dramatically, in the middle of the lake, wait a couple of minutes and they will usually recover enough power to get back to shore. I have never used LiPos so can't comment on them, but in my experience neither NiCd or NiMh batteries will do that, once they're flat they stay flat.
Peter.
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Interesting replies. Thank you. I will keep an eye on my older SLA's and see if they start to lose performance. The voltage readings during charge and after charge (no load) all look good.
However, with something as critical as a submarine I would replace early as a dead battery could be terminal.
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A Lead Acid battery, properly looked after and not overworked, will last a long, long, time. Toward the end of its life, performance will drop off gradually. It isn't going to suddenly stop being a battery. If it does that, something else has gone on, and that could just as easily happen with a new one.
A 12 volt battery in good condition should be over 13.5 volts when charged, any less, it isn't charging fully - first thing to check is the charger. But as said earlier, if it ain't broke, don't fix it. Not many things more disappointing that replacing a perfectly good part with a dud fresh out of the box.
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Malcolm,
OK my charger is putting out 14.5 Volts but at the end of charging the battery registers 12.5V.
Can I get it back to full charge, 13.5 Volts, easily and simply?
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Malcolm,
OK my charger is putting out 14.5 Volts but at the end of charging the battery registers 12.5V.
Can I get it back to full charge, 13.5 Volts, easily and simply?
12.5 is low for a fully charged battery. At a nominal 2.2 volts per cell, a 12 volt battery should charge to at least 13.2 volts, so at a guess, one cell is not really charging and the rest are charging high. 5 X 2.5 gives 12.5 volts with one cell not charging but being a very low value resistance. A clincher for that would be if, under load, after a short time, it lost an extra couple of volts fairly suddenly. That is a sign of a flat cell reverse charging and giving a reverse voltage.
Probably time to mend it with a new one. The "S" in SLA is for "Sealed" as in "sealed for life", "Life" being the life of the battery. Unless its a smart charger stopping early. I do like dumb trickle chargers. They tend to just do as required.
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12.5 is low for a fully charged battery. At a nominal 2.2 volts per cell, a 12 volt battery should charge to at least 13.2 volts, so at a guess, one cell is not really charging and the rest are charging high. 5 X 2.5 gives 12.5 volts with one cell not charging but being a very low value resistance. A clincher for that would be if, under load, after a short time, it lost an extra couple of volts fairly suddenly. That is a sign of a flat cell reverse charging and giving a reverse voltage.
Probably time to mend it with a new one. The "S" in SLA is for "Sealed" as in "sealed for life", "Life" being the life of the battery. Unless its a smart charger stopping early. I do like dumb trickle chargers. They tend to just do as required.
Yes, you are right about it being a smart charger.
From memory I think I have an old trickle charger hanging about.
One of those squarish tin box types with a meter on the front and a switch to select 6 or 12 for charging.
Of to parts unknown to find it.
Thank you.
Success easy to find. Never thought about using it on SLA's had it for charging car batteries.
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I thought that using a general lead acid charger would boil SLA batteries if left to their own devices?
I was always under the impression that Sealed Lead Acid batteries shouldn’t be charged at high rates like wet cells can and should have max voltages and currents limited or have I been over cautious all these years?
I’ve always used 'intelligent' chargers and let them charge for lower and longer than at a standard 14hour rate like wet cells.
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Grasshopper is bang on the money. If your SLA isn't toast already then using that thing will rapidly speed its demise - and maybe yours, too.
Like the man says you need a constant voltage charger which limits the current to well below that thumped out by a car battery charger (which is what you have there). I know you're at the wrong end of the planet for a large choice of retailers but this is the one I use https://www.componentshop.co.uk/1-8a-automatic-desk-top-charger-for-12v-sealed-lead-acid-sla-batteries.html (https://www.componentshop.co.uk/1-8a-automatic-desk-top-charger-for-12v-sealed-lead-acid-sla-batteries.html)
You could probably find similar from ROC suppliers. Just DON'T USE THAT YELLOW THING!!
DM
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Yes, my dumb charger is a puny thing with a current limiting resistor in the lead which keeps the trickle down to around 250mA, OK for my batteries. A "full size" charger should only be used very sparingly to see if it makes any difference. It might start a cell re-forming, but most likely won't, and anyway should be used with extreme caution, meaning an external voltmeter and ammeter.
Smart chargers assume that the battery that they are connected to is a good 'un, anything else confuses them.
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Sometimes a "smart" charger will flash red (faulty) if the battery has been run too low. Half an hour with a low rate "dumb" charger can often build it up enough to continue charging with the smart charger. However, running a battery right down is not a good idea and may significantly reduce its life.
I like to rate my batteries to give at least two hours continuous running, so they come home in good condition for recharging.
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As Dave says, using that yellow charger is likely to turn your SLA into a USA (Unsealed Lead Acid) in short order and maybe spread it around the room as well.
If there is a faulty cell in your SLA it is unlikely that you will be able to restore it to its normal operating capacity. Deterioration with lead acid cells is generally a one way process. They don't respond to short sharp shocks like some other types. People often don't appreciate that lead acids generally do not like to be discharged beyond half of their operating capacity as this can result in irreversible damage and loss of overall power. So in practical terms a 5ah NiMH pack which can be safely deep discharged will have almost double the usable capacity and running time of a 5ah SLA.
Colin
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I know you're at the wrong end of the planet for a large choice of retailers
Actually Dave, we're quite advanced over here, we have a thing called wireless, running water is available (if you happen to live near a stream), and some of us even have electricity {-) . Seriously though, chargers suitable for use with SLAs are readily available, I have a couple and they're very effective, and reasonably priced.
I have to go now, the Goon Show is on the wireless thingy, and Harry Secombe beckons %%
Peter.
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Hi Peter, Ah ha a Goon show fan eh! I used to live opposite the BBC producer of the Goon show, he said he loved it. Gone now but a great guy, John Browell.
cheers Roy
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I have to go now, the Goon Show is on the wireless thingy, and Harry Secombe beckons %%
Heard on a recent flight landing in Sydney “Welcome to Australia, for those wishing to adjust their watches the time here is 1960”
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Seriously though, chargers suitable for use with SLAs are readily available, I have a couple and they're very effective, and reasonably priced.
Then perhaps you might recommend a particular type and a "local" source for it, Peter, or are you keeping it a secret in case you start a rush on them?
Dave M
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I bought one from Lidl/Aldi (forgot which one...) when they had them in stock....I’m always checking their hardware /tool sales.
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Actually Dave, we're quite advanced over here, we have a thing called wireless, running water is available (if you happen to live near a stream), and some of us even have electricity {-) . Seriously though, chargers suitable for use with SLAs are readily available, I have a couple and they're very effective, and reasonably priced.
I have to go now, the Goon Show is on the wireless thingy, and Harry Secombe beckons %%
Peter.
:-)) :-)) :-)) O0 O0 O0 {-) {-) {-)
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I bought one from Lidl/Aldi (forgot which one...) when they had them in stock....I’m always checking their hardware /tool sales.
Yes Aldi has them here also, bought one for my son's Jet Ski, AKA wave runner, will check it out and maybe borrow it.
Car battery charger is back in the cupboard.
My smart charger is one of those Imax B6's, 240V, V2.
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Yes Aldi has them here also, bought one for my son's Jet Ski, AKA wave runner, will check it out and maybe borrow it.
Car battery charger is back in the cupboard.
My smart charger is one of those Imax B6's, 240V, V2.
The Imax will be fine with a battery that has a full set of working cells.
If the battery in the jet ski is a lead acid starter battery, its charger is likely to give the same problems - if its a smart one it might well outsmart itself, if it isn't it might deliver too high a current for safe charging. A battery with a dud cell is headed for recycling. The redeeming feature of lead batteries is that they are very recyclable. But only with the right sort of factory.
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30+ years ago, a colleague at work decided to charge an SLA (approx 7Ah size) using a limited curent PSU at a low current. He left it on all night. The next morning the SLA was completely spherical. We drew lots on who would approach close enough to turn it off.
:} :} :}
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Then perhaps you might recommend a particular type and a "local" source for it, Peter, or are you keeping it a secret in case you start a rush on them?
Dave M
No secret Dave. I have two Powertech peak detection chargers for SLA batteries, one is 6v only as all my SLAs are 6v, and one suitable for 6 or 12 volts. I bought them in a small electronics store in Ballina some years ago, sadly, no longer there, but I believe they, or something similar, are available from the Autobarn chain. I also have an Imax smart charger which I bought online, although I have since discovered that it is a "knock off", distinguishable by the lack of a holographic sticker on the casing. However it works very well, so I'm not complaining - too much %)
Peter.