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SoC for Batteries - with a lot of data!


Dr Bob

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32 minutes ago, dmr said:

 

I think Lithium came out about 3 to 5 times as expensive. I reckon they will become ideal boat batteries, but I suspect its a few years off yet.

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

Apparently the cost of lithium batteries may drop next year due to more competition.   They are already pretty comparable on overall price with semi traction batteries like Trojans.   I agree tho they are the best technology batteries (so far) for off-grid use.   Wouldn’t recommend them for someone on shore power a lot tho.

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Lithium is still going up in value investors are involved  so I suspect that Sodium glass batteries will be the savior of the electric car and become standard fit in everything. Its always the same nowadays investors kill tech because they are greedy sodium fortunately is cheap and plentiful unlike Lithium, Give it two years and all will be well

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A bit more data for anyone still interested and before we go off to the Dog and whatsit up the road in Dadlington.

Last night (from 7pm) we used 50 Ahrs - as read from the meter. I think this is pretty much what was used based on the inverter on for 13hrs (7pm to 8am) running between 1.7A and 5.1 A out depending on whether the fridge was cooing- and the TV/rasp pie/hard disk plus the usual water and toilet vacuum pump - plus 1 coffee from the coffee maker (80A) for a minute. From that I think the current flow over the shunt seems not too far off.

At 8am the voltage was 12.55V with the inverter on. I turned off everything for 20 mins and then the voltage at 20 mins rest was 12.66 (the coffee machine had just been run when it was at 12.55V). Assuming the volt reading is correct (BIG ASSUMPTION) then that says I was 90%+ SoC which is in line with the amps used overnight (again assuming it was near 100% at 7pm the previous evening which I think it was near as the solar had been very good from 3pm to 7pm). All this however is a pile of c**p if the voltmeter is inaccurate. I did notice however that the 12.66V on the BMV was the same as the 12.6V on the MPPT controller.

I then started the engine at 9.00am. The current in on start up was 81A which fell away to 60A in the first 20 secs. It then settled out less than 40A after a minute. I think it is a 90A alternator so does that sound like it is working as it should?

By 9.45 the Amps had dropped to 15A so if we roughly estimate the amps put in (ie draw a graph of amps v time and look at the area under the curve ) I would estimate maybe 15A went in. As only some of this would be converted to 'charge' then maybe we got circa 10A of our 50A used back. In this time however the amp hr counter had gone from -50A to +3.6A.

To me, I think the meter is showing the Amps out and Amps in ok, and the voltage ok  but something is wrong with the Amp hr counter. I experienced this on our old boat with a BMP monitor that seemed to ok on voltage and amps in/out but the counter would add up for half an hour or so then jump back to the fully charged amp hr setting. I assumed the current meter is the actual current over the shunt but the Amp hr counter was a function of these number plus what it made up itself trying to compensate for Pukhets equation or whoever it was who made this topic so complicated. This boat seems the same. Amps hrs out seems fairly accurate but amps hrs in seems a bit of a fantasy. (I will check to see if there are any wires not connected to the shunt but I suspect it s ok as it seems to be the Amp hr in counter that is telling lies).

A final comment on the solar. The solar mppt was showing it on 'adsorption' when the engine was switched off, so the voltage on the mppt was 14.4V (thats what it is set to) - but the voltage on the BMV was now different at 14.21V. At this stage I had circa 10A of solar coming in but there was 5-8A being used by the various chargers etc. Not sure why the solar wasnt on float.

Ok, so what can I conclude from all this - and all your inputs.

1) I think the alternator is charging ok at the start with 80A immediately. It seems however to have far too low a float voltage which cannot be adjusted. I will check the voltages across the alternator and the batteries etc. Sounds like I may need a new alternator.....and maybe a higher current version.

2) I must be getting near my 100% SoC (ie 95%+) given the 'voltage at rest' but this is probably due to the solar - so ok for another month or so.

3) The solar mppt is set for 14.4V in 'adsorption' but less than 14V on float. Should I increase the float voltage to 14.4V or even 14.8V? That seems to be the cheapest way to get a bit more charge into the batteries.

Ok, Dog and whatsit is calling ........

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I agree the volts and Ah in/out seem to correlate.

Have you synchronised your BMV when the batteries are fully charged? If you don't do this regularly the % charge will get progressively further out of kilter.

Also have you got the correct settings in the BMV regarding battery type, capacity and when to stop charging? 

It is particularly important to change the stop charging % F3. The BMV default is 4% tail current, and a more realistic setting is 1%.

This thread shows my learning curve on the BMV.

Since then I have reduced F1 to 400 Ah to reflect the reduced capacity of the 10 year old batteries (measured by discharging to load at theg 10 hour rate) and further decreased F3 to 1% which more accurately reflects a fully charged battery.

To synchronise the BMV when you are sure the batteries are fully charged, simply press the left and right arrows together for 3 seconds, with the display showing the % SoC.

 

Edited by cuthound
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Thanks cuthound. I have sync'd the BMV almost each day when I consider it full. I will get the manual out and look at the F3 setting. I am sure it is not set properly for battery type etc but will have a look tomorrow.  I'll also have a look at your link. Interesting. ....the pub is calling.

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3 hours ago, peterboat said:

Lithium is still going up in value investors are involved  so I suspect that Sodium glass batteries will be the savior of the electric car and become standard fit in everything. Its always the same nowadays investors kill tech because they are greedy sodium fortunately is cheap and plentiful unlike Lithium, Give it two years and all will be well

I think it will be a lot more than two years before sodium batteries become available on mass, more like 5-10 years.

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13 minutes ago, Robbo said:

I think it will be a lot more than two years before sodium batteries become available on mass, more like 5-10 years.

Yes, let's hope they don't take as long to production is as fuel cells.

They have been on the verge of becoming cheaply and widely available for 45 years now! :mellow:

Lithium ion batteries have been around in iPods and phones for for about 20 years now, and whilst the cost per watt hour has come down a fair bit, it still has a long way to go to match lead acid batteries.

Edited by cuthound
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With your level of interest, I'd say just forget the amp hours counter and use the voltage and current readings to judge the state of charge, unless you want to get a SmartGauge that, pace MtB, gives you a good guide to SoC on discharge.

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6 hours ago, dmr said:

They do look very attractive but don't look anywhere close to cost effective at present, but if you enjoy been at the "bleeding edge of technology" then go for it.

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

I read that hire boats on the Broads have started using them

59 minutes ago, Dr Bob said:

Thanks cuthound. I have sync'd the BMV almost each day when I consider it full. I will get the manual out and look at the F3 setting. I am sure it is not set properly for battery type etc but will have a look tomorrow.  I'll also have a look at your link. Interesting. ....the pub is calling.

Why don't you check with a hydrometer to make SURE they are fully charged before syncing the BMV so you know where you are

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8 hours ago, dmr said:

Have a search on www, I found something a couple of weeks ago and did a rough mental calculation but its all slipped from my memory, probably too much beer drinking.

Preety sure it was a link on this forum.

Its never trivial comparing batteries, Trojans can go down to 20% but its probably best to keep them above 40 or 50%. I think Lithium can go to 0% but maybe 20% is recomended. Trouble is its probably not good to go down to 20% cus if you have a crisis (engine won't start or need to go out urgently) then you have nowt in reserve, so 50% is probably wise regardless of battery requirements.

I think Lithium came out about 3 to 5 times as expensive. I reckon they will become ideal boat batteries, but I suspect its a few years off yet.

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

 

It's also very unwise to charge lithiums to more than 80%, i keep reading.

So that 90AH lithium for £997 actually only gives you 72AH.

They will only be the ideal boat battery if those whose confidence exceeds their competence can be restrained from levering the tops off and charging them directly from their genny, if/when the internal electronic controls croak it. Which I bet will happen from time to time. 

I suppose word will spread after a few spectacular boat fires through. 

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20 minutes ago, Mike the Boilerman said:

 

It's also very unwise to charge lithiums to more than 80%, i keep reading.

So that 90AH lithium for £997 actually only gives you 72AH.

They will only be the ideal boat battery if those whose confidence exceeds their competence can be restrained from levering the tops off and charging them directly from their genny, if/when the internal electronic controls croak it. Which I bet will happen from time to time. 

I suppose word will spread after a few spectacular boat fires through. 

I understand this is the boat with Lithium Batteries I think its victron set up but not sure, O and its got 2 girly buttons

 http://www.richardsonsboatingholidays.co.uk/boats/commodore/

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18 hours ago, Robbo said:

I think it will be a lot more than two years before sodium batteries become available on mass, more like 5-10 years.

Never underestimate the power of need! Electric cars are coming and a cheap chargeable battery that isnt temp dependent is needed, and Lithium isnt the answer, cos it aint cheap and is useless in the cold and has a habit of catching fire when its to hot!

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11 minutes ago, peterboat said:

Never underestimate the power of need! Electric cars are coming and a cheap chargeable battery that isnt temp dependent is needed, and Lithium isnt the answer, cos it aint cheap and is useless in the cold and has a habit of catching fire when its to hot!

They have been saying sodium would be the next battery technology for years (and it’s prob been investigated for battery use since lithium as well), but I think we are still a long way off before anything comes to market.   I think lithium still has a long future, and if your waiting for the “next big thing” before getting some batteries, you will always be waiting.

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15 hours ago, ditchcrawler said:

I understand this is the boat with Lithium Batteries I think its victron set up but not sure, O and its got 2 girly buttons

 http://www.richardsonsboatingholidays.co.uk/boats/commodore/

During our 10 years on the Broads we saw or rather heard countless boats actually being steered soley by using the girly buttons. Often wondered how long the thrusters lasted.

Phil 

 

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In terms of energy density (watts per kg),  nothing can touch the aluminium air battery.

It is easy to produce commercially too.

The major stumbling block is that it is a primary cell, so can't be recharged. However is is almost 100% recyclable, so just needs a network of battery replacement stations to make it viable, particularly to power electric cars.

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58 minutes ago, cuthound said:

In terms of energy density (watts per kg),  nothing can touch the aluminium air battery.

It is easy to produce commercially too.

The major stumbling block is that it is a primary cell, so can't be recharged. However is is almost 100% recyclable, so just needs a network of battery replacement stations to make it viable, particularly to power electric cars.

Aluminium ion batteries are chargeable tho and could have 4 times the capacity of lithium and a very high cycle count.  Wonder why these haven’t been the future lithium killer as they sound a lot better than sodium which suffers in the cycle count area.

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11 minutes ago, Robbo said:

Aluminium ion batteries are chargeable tho and could have 4 times the capacity of lithium and a very high cycle count.  Wonder why these haven’t been the future lithium killer as they sound a lot better than sodium which suffers in the cycle count area.

I don't know, possibly because they want to recover the development costs of lithium first? :P

Perhaps,  having seen the success of the  using industry in selling vinyl, cassette, cd, dat and then vinyl again to music lovers, they envisage something similar with batteries? 

Cynical moi? 

I witnessed a practical demonstration of aluminium air batteries as a one shot alternative to standby generators back in the early 1980's, the only obstacle being reducing the production costs and persuading customers to buy them. 

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