Battery monitor

[noelex]

We shall have to agree to disagree!

I am happy to agree to disagree. If boat owners have gained information on how to maximise their battery system after persisting with tis thread , perhaps we have achieved something.

 

[halcyon]

If there is a low level load and high battery capacity the Peukert equation is irrelevant, but modern sail boats often run high current devices such as water makers, and even boats with small battery capacity, use relatively high current devices such as a fridge and computer.

But those are only intermittent loads, not perminent loads.

You may have a computor on the small battery capacity, but you only have a low average loading on the battery. If the computor represents a high perminent load, a) you will not be able to sail far before a flat battery b) you should not have turned it on.

The first job with any boat is to make sure the system you have, meets the needs you have. Having a BM with Peukert will only tell you that you should not have turned the computor on. Which you already knew, well should have.

I have been envolved with battery monitoring and boats since 1980, back then we had fridges on yachts to. The problem then was bigger because the fridges were not efficient, and the altenator smaller. But we could normally get an owner through a season without a flat battery, or problem.

Brian

 

[noelex]

It is during high loads that the battery drains more than the simple AHr draw would predict. Peukert formula needs to be applied in these situations. Even if if the high load in inermittant the compensation needs toi be applied. If the battery monitor does not compensate for this the SOC reading will be incorrect , particularly over several charge and discharge cycles. Most high end battery monitors apply this Peukert compensation for this reason.
The high current demands of modern boating appliances make this sort of adjustment essential if the SOC counter is kept accurate.

 

[Maine Sail]

It is during high loads that the battery drains more than the simple AHr draw would predict. Peukert formula needs to be applied in these situations. Even if if the high load in inermittant the compensation needs toi be applied. If the battery monitor does not compensate for this the SOC reading will be incorrect , particularly over several charge and discharge cycles. Most high end battery monitors apply this Peukert compensation for this reason.
The high current demands of modern boating appliances make this sort of adjustment essential if the SOC counter is kept accurate.

Most all battery manufacturers will supply you with the Peukert correction for their batteries. When installing monitors I always get the manufacturers Peukert data to plug into the monitor.

As far as I am concerned there is no perfect battery gauge or monitor. They can get out of whack quite easily especially if only charging off an alternator and sulfation sets in.. I suspect the monitor manufacturers re-set to full @ 2% because if not consumers would complain and whine that their batts were never "full".

On my own boat I use solar to get the bank back to 100% with a nice low current charge that takes the bank from 80% +/- to 100%. My own monitor is set to 1% for re-set though I still usually manually re-set when it is taking about .5% at solar float voltage.. My bank is usually taking less than .5% when full at about 13.8V..

I use my monitor as a guide only and I could care less if it is 2 or 3% off as I never even dip the bank below 65-70% soc and get very good life out of my inexpensive banks. I also load test my batts each winter doing a 20 hour discharge on each battery in the bank so I know when it is time to replace. I have actually found that most batts will produce slightly more that their 20 hour rate at 77F. I suspect this is because the manufacturers play it safe with the 20 hour ratings to account for variations in lead and antimony and other variables that come with chemistry,.

I install mostly Victron monitors but also install the Xantrex monitors too and both allow many variables to be set, tweaked or changed... By far the biggest issues I see are not with scaling issues but installation errors and lack of correct programming..

I see reserve capacity plugged in for Ah's about once a month and have also seen cranking amps plugged in as Ah.. That guy had a very, very dead bank, but not according to his monitor. The batteries were "obviously junk"......... Ouch.....

 

[Plevier]

I install mostly Victron monitors but also install the Xantrex monitors too and both allow many variables to be set, tweaked or changed

Maiine Sail, agree all your comments. Just been reading both Xantrex and Victron websites - have a strong feeling they are the same devices with different labels is that right?

Both manuals are very coy about what they mean by state of charge readout. They don't say whether it's relative to the nominal capacity, or the effective capacity at the discharge rate in use. I suspect the former as they both talk about the capacity withdrawn being simply amps X time - they do not mention Peukert in that context.

They both offer time left to go at the present rate of discharge (they make that statement explicitly - at the present rate of discharge). That is calculated with Peukert's equation and they both stress that it's pretty approximate.

Regarding charge efficiency both let you set a single average factor, it is not compensated for state of charge. Victron's default is 95%, can't recall if Xantrex same. (I'm surprised it's so high).

Both stress the need for synchronisation. It is supposed to occur automatically but getting out of step seems to be tacitly accepted.

Both say words to the effect that at the switch to float charge point (which Victron takes as 4% current, not 2%) the battery "may be considered" fully charged. Well they may like to "consider" it fully charged for their purposes - but it isn't!

So there is nothing there to change my view, but nor can I get positive proof from either manual! Technical detail is a bit lacking.

 

[Maine Sail]

Maiine Sail, agree all your comments. Just been reading both Xantrex and Victron websites - have a strong feeling they are the same devices with different labels is that right?

The in-between series for Xantrex which included the XBM was the same as the older Victrons and they were both made by TBS Electronics in the Netherlands.

Today the Xantrex monitors are made by TBS and Victron has pulled out of TBS and I suspect are building them on their own. The current production monitors from Victron and Xantrex/TBS are very different.

Both manuals are very coy about what they mean by state of charge readout. They don't say whether it's relative to the nominal capacity, or the effective capacity at the discharge rate in use. I suspect the former as they both talk about the capacity withdrawn being simply amps X time - they do not mention Peukert in that context.

Both the Victon and Xantrex monitors correct for Peukert, if you program it correctly, On the SOC screen (Victron) and the % screen for Xantrex Peukert is calculated for. On the Ah or CE/consumed energy screen they are not Peukert corrected.

They both offer time left to go at the present rate of discharge (they make that statement explicitly - at the present rate of discharge). That is calculated with Peukert's equation and they both stress that it's pretty approximate.

TTG is a pretty useless feature but it's there. I don't think I have ever even looked at it or cared. My loads vary so the CS or % screens would matter more.

Regarding charge efficiency both let you set a single average factor, it is not compensated for state of charge. Victron's default is 95%, can't recall if Xantrex same. (I'm surprised it's so high).

My bank takes about 111% of what was removed, put back in, to get it back to full. It took me a while to get to this and of course it's a moving target as a battery ages. This is why I say there is no perfect monitor but they get darn close.

Both stress the need for synchronisation. It is supposed to occur automatically but getting out of step seems to be tacitly accepted.

Again not much way they can't get out of synch eventually. If you manually re-set, when known full, baed on accepted current from the charge source, and use it to count Ah's to keep yourself away from the 50% DOD threshold they are great. If you pad it by 5% and dip to 55% you're going to be very safe..

If you want pin-point accuracy the device has not been made yet and at least not enough to prove to me that it is "pin point". Where are these white papers and independent lab testing dissertations on the Smart Gauge...? I'd love to see them and read them but as of yet I can't find any..

We don't expect pin point accuracy out of the gas gauges in our cars yet we do on something as complex as batteries...? My gas gauge is currently well below the red line and I know I can go at least another 20 miles....

Both say words to the effect that at the switch to float charge point (which Victron takes as 4% current, not 2%) the battery "may be considered" fully charged. Well they may like to "consider" it fully charged for their purposes - but it isn't!

And again they need to balance customer expectations with product reputation. Most owners are so naive when it comes to boat electrics that they are just happy to see it say "FULL" whether it technically is or not. There is nothing wrong with cycling between 98% and 50% or 98% and 60% as the time it takes to get that last 2% into the battery, on a boat, is often unrealistic unless it sits at a dock or has solar or wind...

So there is nothing there to change my view, but nor can I get positive proof from either manual! Technical detail is a bit lacking.

Yeah I had to actually speak with engineers at both Victron and TBS to get the answers I was looking for...

 

[Stu Jackson]

The 2% figure, as discussed on one of the earlier pages of this thread, is a default value. It can be changed on the old Link models and the Xantrex Links, don't know about the Victrons. Modifying the default values is not something most recreational boaters do, because as Maine Sail said, most folks don't know enough about it. Many of us have modified the default 2% to 1% to avoid the Link calculating a premature "full" bank, because the 2% was a vendor selected default. If your fridge was on after a daysail, depending on how your system was set up, it was possible to have the charger prematurely put the charger into float way too soon (Link 2000 and Freedom combined inverter chargers, like mine).