Still eatng batteries?

[Keeping Up]

It seems as if our boat still wants to eat batteries.

 

After installing new batteries (4x110 Ah Varta), in the first week the voltage in the mornings was 12.6, in the second week 12.5, in the third week 12.4, in this the fourth week 12.3

 

Poor charging regime, I hear you say. But we cruise every day for between 6 and 8 hours, by which time the batteries are taking less than 1 amp at 14.6 volts. By my reckoning that means we are fully charging them every day, and our normal usage is only about 65 to 75 Ah overnight (TV, lights, etc during the evening then the fridge and inverter stay on).

 

The symptoms are the same as with previous batteries, which continued downwards at 0.1v per week until they were useless after less than 3 monthss. In the past 2 years the boat has eaten 2 sets of Vartas, one set of US batteries, and 2 sets of Numax (20 batteries in all!). The only ones to last were a set of cheapies that were still giving about half their capacity after nearly 6 months.

 

Since than I have had a new engine fitted so have changed from a 70 amp alternator with Adverc set to 14.4v, to a new Beta with 175 amp alternator running up to 14.6. No difference in symptoms. I have also rewired the whole high-power end of the system with 70mm cable, got a new inverter, replaced the old analogue ammeter with a Nasa BM2 (which confirms my original energy audit), and changed all my lights to LEDs.

 

So why do my batteries not seem to like the way they are being treated? I don't have the facility to do an equalisation charge when travelling, but surely it shouldn't be so urgently needed? Don't dozens of other people run batteries from a Beta engine for months on end, without their voltage steadily dropping?

 

Any ideas?

Edited August 4, 2014 by Keeping Up

[PhilR]

Your charging regime sounds more than adequate to me. I wonder if you might be underestimating your overnight power consumption? The recent weather has been exceptionally hot and your fridge has probably been working overtime. 75 Ah is probably approaching 20% of your battery capacity and this might be an underestimate?

 

Ideally, you should switch everything off for a couple of hours before taking a voltage reading.

 

BTW, are all your 4 new batteries for cabin electrics or is one of them a starting battery?

 

I'm sure you will get loads of more helpful replies from the experts. Good luck.

[Guest]

Have you actually verified what the batteries are actually receiving from the alternator, ie are they really getting 14.6?

[system 4-50]

What components of your charging system have not been changed during this period?

[Machpoint005]

The one with a hole where the electrical fluid leaks out?

 

A facetious way of agreeing with 4-50, in other words.

Edited August 4, 2014 by Machpoint005

[Keeping Up]

Thanks for the thoughts so far.

 

The amp hour figure comes from the BM2 readout so I think it is fairly accurate. It is also exactly what I expected it to be which gives me confidence in it. On just one occasion when we had a slightly longer stop and watched DVDs while the fridge battled against a hot day we managed to use 120 Ah but that's still only just over 25% of the bank's nominal capacity.

 

These 4 are all for the domestic supply, there's a starter battery too. On our old engine there was a diode splitter - hence the Adverc - but on the Beta there is a second alternator so the systems are completely separated.

 

Admittedly things have only been switched off for a few minutes before observing these readings, but that has been consistent from the start, it's the slow and steady trend downwards that is worrying - and I can see it happening even if I don't switch things off first. Anyway with the fridge not running the rest of the load is only 2A which doesn't make a lot of difference.

 

I've checked the readings, both charging and discharging, separately with a digital voltmeter on the terminal posts of each battery too, just in case I had a poor connection. Every reading has been the same on the DVM as that shown by the BM2. The SG of the batteries when charged is also starting to fall, so everything points in the same (downwards) direction.

What components of your charging system have not been changed during this period?

That's what puzzles me. There is literally nothing (including all the cables and even the isolator switch) that has not been changed. The only common features are the domestic items from the consumer unit onwards, and our cruising and charging patterns.

[Machpoint005]

Every cable? Every joint? Every plug socket and light fitting?

(you see what I'm getting at).

[nicknorman]

First of all it's really helpful to have a Smartgauge as well as an amp-hour counting meter, that way you get a "scientific" indication of the actual capacity of your batteries vs the as-new capacity, although I accept you're getting a pretty good idea just from the voltage. My experience with the same engine/alternators was that after 6 months of occasional use, and being left on shore power float for long periods, the capacity of a new set of cheapo wet lead acids was down approaching 50%. I equalised them and miraculously recovered back to 100%. I found that if I equalised them every few months I could keep the capacity well up but approaching 2 years, they started to get sick, didn't respond to equalisation and in the end I replaced them with Trojans. How the Trojans will fair remains to be seen but so far after 4 months they remain perfect.

 

I get the feeling that wet "leisure" batteries just don't like to be used intensively. As we know they are pretty much just re-badged starter batteries. Maybe the folk who get them to last years, are light users so the batteries don't get cycled that much and when the capacity falls significantly they don't notice.

 

Anyway, maybe you should put into a marina for a night on shore power and try an equalise (presuming you have a charger on board that can do it)? I am presuming your Vartas can be equalised?

[Keeping Up]

Every cable? Every joint? Every plug socket and light fitting?

(you see what I'm getting at).

On the charging side, yes everything. The consumer unit is the first thing that is unchanged.

 

---

 

Nicknorman, your experience with cheap batteries is interesting. I too suspect that battery technology has changed for the worse, and even mid-range batteries like Varta are just rebadged starters. Our previous Vartas had lasted 4 years, but I know they changed their technology just before we bought a set, by adding calcium, and fortunately for us most of the resulting battery replacements were made under guarantee (Varta even removed the range from the market to make some "adjustments" to the formulation)

 

As you say, many users are light or occasional users only, who either don't suffer poor performance or else just don't notice it. Unfortunately my charger on the boat doesn't do proper equalisation charges so I'm a bit stuffed there!

[Keeping Up]

I've been observing the BM2 closely to try and understand its SOC figures. It looks very much as if on discharge it uses instantaneus voltage readings, with perhaps a correction factor for the instantaneous current when the reading is taken, but is not counting amp-hours. On the other hand when charging it seems to ignore voltage and current but simply does an amp-hour count. This will give a correct answer for SOC if (and only if) the Battery Capacity figure set in the Menu is an exact match to the actual capacity. I found that if I charged the batteries until they were effectively full and then adjusted the Capacity setting until it showed 100% SOC, all the figures seemed to track each other properly; the capacity to which I had to set it then told me my bank capacity. If my assumptions are correct and this method is accurate, my 440Ah bank is today sitting at 280Ah capacity

[Bee]

I would try checking for a voltage leak, turn the lot off, is there still current flowing? Batteries nice and dry on top? That's an awful lot of batteries gone duff.

[jenlyn]

When you set the bmv, are you putting the figure 440 in?

[Keeping Up]

I would try checking for a voltage leak, turn the lot off, is there still current flowing? Batteries nice and dry on top? That's an awful lot of batteries gone duff.

 

There is no unexplained leakage. Everything is clean and dry. The current drains are all known and accounted for, being basically 2.2 amps constant plus the fridge

 

When you set the bmv, are you putting the figure 440 in?

When the batteries were new I set it at 440, it tracked accurately enough for a couple of days. Now it tracks accurately when set to 280. By this time next week it'll probably need resetting to 220

[jenlyn]

There is no unexplained leakage. Everything is clean and dry. The current drains are all known and accounted for, being basically 2.2 amps constant plus the fridge

 

 

When the batteries were new I set it at 440, it tracked accurately enough for a couple of days. Now it tracks accurately when set to 280. By this time next week it'll probably need resetting to 220

Set it at 220. Fully charge the batts and sync the bmv. I don't have the instructions with me, but if you read them, I think you will find you have set the bmv incorrectly.

[by'eck]

I've been observing the BM2 closely to try and understand its SOC figures. It looks very much as if on discharge it uses instantaneus voltage readings, with perhaps a correction factor for the instantaneous current when the reading is taken, but is not counting amp-hours. On the other hand when charging it seems to ignore voltage and current but simply does an amp-hour count. This will give a correct answer for SOC if (and only if) the Battery Capacity figure set in the Menu is an exact match to the actual capacity. I found that if I charged the batteries until they were effectively full and then adjusted the Capacity setting until it showed 100% SOC, all the figures seemed to track each other properly; the capacity to which I had to set it then told me my bank capacity. If my assumptions are correct and this method is accurate, my 440Ah bank is today sitting at 280Ah capacity

 

Amp hour counting alone (even if the bank capacity is set correctly) as a way of calculating remaining battery energy is useless without voltage being taken into account.

 

The NASA BM2 uses amp hour counting and battery voltage to calculate battery SOC via a series of algorithms. Even then it can only give an SOC percentage based on the battery discharge regime since last full charge, as future discharge currents can't be predicted.

 

For this reason and that of not knowing true battery capacity, I wouldn't pay too much attention to SOC readings especially if you have accurate means of monitoring battery charge/discharge currents and at rest voltage.

 

FWIW I frig battery capacity based on at rest voltages after known discharges having first asserted they are fully charged and SOC has been indicating 100% for some time, minimal charge current etc. Presently this is 460 Ah out of original 550 Ah of leisure batteries when new just over two years ago.

[MoominPapa]

Is there any way you can give the batteries a really good, long charge. like 24h on a mains charger attached to a shoreline? That would be a way to distinguish between batteries which are decaying, and a consistent undercharge.

 

 

MP.

[Keeping Up]

I have the manual here. By extrapoilating from the manual I arrived at the above conclusions. I haven't set it incorrectly, it is just as a matter of interest that I have arrived at a way of perhaps getting apparently accurate SOC figures and at the same time quickly determined the capacity of the bank.

 

Amp hour counting alone (even if the bank capacity is set correctly) as a way of calculating remaining battery energy is useless without voltage being taken into account.

 

The NASA BM2 uses amp hour counting and battery voltage to calculate battery SOC via a series of algorithms. Even then it can only give an SOC percentage based on the battery discharge regime since last full charge, as future discharge currents can't be predicted.

 

For this reason and that of not knowing true battery capacity, I wouldn't pay too much attention to SOC readings especially if you have accurate means of monitoring battery charge/discharge currents and at rest voltage.

 

FWIW I frig battery capacity based on at rest voltages after known discharges having first asserted they are fully charged and SOC has been indicating 100% for some time, minimal charge current etc. Presently this is 460 Ah out of original 550 Ah of leisure batteries when new just over two years ago.

 

Read what I said again. After observing it for a month I am convinced it doesn't use Ah counting at all when the batteries are discharging, and that it uses Ah counting alone when they are charging, with possible amendments to allow for current levels when discharging. This is why the figures fail to track unless the capacity is set in the engineering menu to match precisely the real value of the bank's capacity.

 

Would you not agree that if they are taking less than 1A at 14.6v and have been doing so for over an hour they are pretty close to 100%? So knowing how many Ah have been taken out overnight, and knowing the open circuit rest voltage, I can reaasonably accurately estimate the SOC?

 

I don't pay much attention to the SOC readings on the meter. I only bought the BM2 as a good way of showing voltage and current, from them I have a good idea of the SOC. But if I can make it show the SOC as well,and maybe even tell me the capacity of my battery bank, that is even better.

Is there any way you can give the batteries a really good, long charge. like 24h on a mains charger attached to a shoreline? That would be a way to distinguish between batteries which are decaying, and a consistent undercharge.

 

 

MP.

I can connect to a shoreliner for 24 hours but my charger won't do an equalisation charge. It will only charge to 14.6 v which is the same as my alternator does anyway, and after4 hours it drops back to 13.8

[MoominPapa]

Would you not agree that if they are taking less than 1A at 14.6v and have been doing so for over an hour they are pretty close to 100%?

From experience, that sounds like a very low end current. I wonder if there's something wrong there? Either the instrumentation is lying, or Gibbo's famous effect is occurring and the voltage is high enough to fill the electrolyte with hydrogen bubbles and increase the internal resistance, and that's what's causing the low current, not the state of charge.

 

MP.

[ditchcrawler]

Do you still have the Adverc, if so a forward biased diod in the battery voltage sensing line will up the output bu about 0.7 volts.

[by'eck]

Read what I said again. After observing it for a month I am convinced it doesn't use Ah counting at all when the batteries are discharging, and that it uses Ah counting alone when they are charging, with possible amendments to allow for current levels when discharging. This is why the figures fail to track unless the capacity is set in the engineering menu to match precisely the real value of the bank's capacity.

 

Would you not agree that if they are taking less than 1A at 14.6v and have been doing so for over an hour they are pretty close to 100%? So knowing how many Ah have been taken out overnight, and knowing the open circuit rest voltage, I can reaasonably accurately estimate the SOC?

 

I don't pay much attention to the SOC readings on the meter. I only bought the BM2 as a good way of showing voltage and current, from them I have a good idea of the SOC. But if I can make it show the SOC as well,and maybe even tell me the capacity of my battery bank, that is even better.

 

I can connect to a shoreliner for 24 hours but my charger won't do an equalisation charge. It will only charge to 14.6 v which is the same as my alternator does anyway, and after4 hours it drops back to 13.8

 

Not what the manual suggests

 

From experience, that sounds like a very low end current. I wonder if there's something wrong there? Either the instrumentation is lying, or Gibbo's famous effect is occurring and the voltage is high enough to fill the electrolyte with hydrogen bubbles and increase the internal resistance, and that's what's causing the low current, not the state of charge.

 

MP.

 

Some batteries particularly ageing ones do take a higher standing current after being fully charged. Its not in the least unusual particularly with lead/calcium leisure types to take less than an amp on a fully charged 500 Ah bank whilst on float and not much more at absorb voltage.

[Keeping Up]

Not what the manual suggests

 

 

Manuals can be misleading.

 

Here's the test. Connect the BM2 to a partially charged battery and allow a small discharge for a couple of minutes so that it registers as Discharging. The BM2 shows an SOC figure, this cannot have been derived by counting. Now disconnect the BM2 and charge the battery fully. Reconnect the BM2 and take current until the voltage matches that of the original test; the SOC is shown as the same figure as before, regardless of what you have manually entered as the capacity. From this I deduce that it it is not counting Ah when discharging.

 

Now start charging. The voltage is now irrelevant, and the change in SOC displayed matches that which you get by mentally adding the Ah that you know you have supplied, divided by the capacity which you have manually entered. If you change the capacity on the menu while charging, the displayed SOC immediately changes accordingly.

 

When you stop charging, after a couple of minutes discharge the SOC suddenly changes to a figure that corresponds to the terminal voltage. I don't think it knows what to do about surface charge so it takes a while before it becomes accurate again.

[by'eck]

Manuals can be misleading.

 

Here's the test. Connect the BM2 to a partially charged battery and allow a small discharge for a couple of minutes so that it registers as Discharging. The BM2 shows an SOC figure, this cannot have been derived by counting. Now disconnect the BM2 and charge the battery fully. Reconnect the BM2 and take current until the voltage matches that of the original test; the SOC is shown as the same figure as before, regardless of what you have manually entered as the capacity. From this I deduce that it it is not counting Ah when discharging.

 

Now start charging. The voltage is now irrelevant, and the change in SOC displayed matches that which you get by mentally adding the Ah that you know you have supplied, divided by the capacity which you have manually entered. If you change the capacity on the menu while charging, the displayed SOC immediately changes accordingly.

 

When you stop charging, after a couple of minutes discharge the SOC suddenly changes to a figure that corresponds to the terminal voltage. I don't think it knows what to do about surface charge so it takes a while before it becomes accurate again.

 

I wasn't disputing the monitors operation when charging is taking place which clearly states that amp hour counting tempered by charge efficiency factor is used, just on discharge when both current and voltage are used tempered by Peukert effect. Connecting/disconnecting the unit proves little - they are meant to be connected once and left to learn the system.

 

Back to your original issue, I wonder if you are in fact overcharging the batteries whilst running the engine, and so hastening their demise. Thoughts are as follows:

 

You have a large alternator that relies only on its internal regulator set at 14.6 volts. You cruise regularly for long days with modest battery drain in between. This leaves the batteries being charged at 14.6 volts for extended periods well beyond the time when a smart charger would have dropped to float. Clearly electrolyte loss would be an issue but I guess you have that covered. I admit this theory may be grabbing at straws but it seems you still haven't had a definitive answer.

 

The above is one of the reasons I use external multi-stage regulators on both of my alternators.

[Keeping Up]

I reckon it's significant that the manual says it uses volts and amps to determine the SOC when on discharge, but it only mentions Ah counting in the context of charging. In the tests I describe above,disconnecting the unit was designed to ensure that it had no way of knowing that I had recharged the batteries, and to see how it reacted (which it did strictly according to the voltage - remembering that all the discharge currents are quite low so the Peukert-monster (or myth) shouldn't arise)

 

Returning to the original problem, I too have wondered if the batteries were being overcharged, but (1) I was having the same problems when I had a smaller alternator and a 14.4v Adverc and (2) The current has dropped to about 10A before the alternator starts to increase the voltage above 14.4, and below 2A before it gets above 14.5; there has been no noticeable loss of electolyte so I don't think it's a matter of overcharging. But I admit to being baffled and will happily consider any suggestions.

 

Incidentally I got rid of the Adverc when the new system was fitted, it is now as simple as could be (Beta alternator, isolator switch, BM2 monitor, and a selection of short new 70 sq mm cables (the batteries are right next to the engine).

 

I have been wondering if there is any way that temperature could be an issue?

[dmr]

Sounds a lot like sulphation to me but I am surprised it happens so quickly.

As Nick says a Smartgage is a very good investment but might not give the full story here, but get one anyway!.

I would much rather see 14.8v than 14.6v when charging from an alternator. Get the Adverc working again if you can, though you will need to do the mod on the alternator. Don't mess about with diodes, there is a simple voltage adjustment inside the Adverc

 

The weapon of choice for getting to the bottom of this is the hydrometer. Its all a bit tedious but will truly give you the state of charge and I bet a beer that the batteries are NOT getting to 100% charge even when you think they are. The old rule is an 8 hour charge once per week. If you are doing lots of 4 hour cruises, or even a bit less, and only charging at 14.6, then its probably not quite enough and once the sulphation starts there is even less charge going in than you think.

 

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

[nicknorman]

Yes I think Dave is right. We cruise for long hours per day as you do, the boat is on shore power float when we are not on it. And yet in 6 months from new the capacity was way down, but was restored after a 15.5v equalise.

 

Regarding hydrometers, I got one of those optical ones from ebay. Looks easier and less messy than the tube-and-float type, though I haven't felt the need to use it yet since our Trojans are still at 100%.