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Battery Monitors and Capacity


GeoffS

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Just now, Richard10002 said:

When you say Ah gauge, what do you mean? Is it something like a NASA BM2 SOC reading? Or are you taking Ah used reading and calculating SOC from your estimate of capacity?

The fact that you may have an incredibly accurate Smartgauge at all states of charge is fine but, if you read the manual, Gibbo makes it clear that it is not to be expected at all times.

Thus it is entirely possible that MtB and myself are right in what we now say, and it is entirely possible that you are correct in what you say about your particular Smartgauge on your particular system.

 

My AH gauge is a Mastershunt. Since it is not very common, I tend not to refer to it by name in order to avoid confusion. But it is similar to say a BMV 700series, but without the analogue shunt, and a little better IMO, although you need a separate Masterview screen to read the figures (which conveniently also talks to the Combi). Anyway, it reports the SoC based on AH taken out / put back in and keeps a running calculation of Charge Efficiency Factor which it includes in the recharge SoC figure.

As I understand it, a NASA BM2 is not a straightforward AH-counting SoC gauge, it tries to be “cleverer” during discharge, but fails. Its discharge SoC is pretty rubbish according to many accounts.

We know why both of MtB’s SGs are rubbish - they are both way out of calibration. I don’t know why yours would be less accurate than mine, but I haven’t seen the calibration nor the installation.

3 minutes ago, Mike the Boilerman said:

 

Err... do you know something I don't?

Oh! Did you sell one? I must have missed that. Anyway, it means you will have loads of cash burning a hole in your pocket - you could get rid of that encumberance by buying some lithium batteries:P

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On 23/10/2017 at 11:11, Jon57 said:

 

Lithium batteries. The big unanswered question is how do you charge them? The listing is silent on the point  as far as I can see. Lasdt time I looked at lithiums one had to buy a dedicated charger which plugged into the 240Vac supply. This may have changed nowand they can be charged from an ordinary alternator but the listing doesn't actually say, AFAICS.

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21 minutes ago, Jon57 said:

They are not a bad price (you can get them much cheaper than your specific ad) but I think perhaps differences are down to the built-in electronics and safety features. There is no mention of cell balancing nor of over-temperature passivation that do get a mention in more expensive offerings. It’s not that clear about over and under charge protection either.

16 minutes ago, Mike the Boilerman said:

 

Lithium batteries. The big unanswered question is how do you charge them? The listing is silent on the point  as far as I can see. Lasdt time I looked at lithiums one had to buy a dedicated charger which plugged into the 240Vac supply. This may have changed nowand they can be charged from an ordinary alternator but the listing doesn't actually say, AFAICS.

The charge regime for the quoted batteries talks about 14.4v which should suit many boat alternators. What is not totally clear is whether you have to take them off charge once they are fully charged and/or what happens if you don’t. Data sheet here:

B8823069-EE6C-4D56-B23A-2ACABFD0A111.png.64cfe0989ec25508053f9b49a7a8477d.png

 

79B2711B-78D7-4D60-AFE0-59ECB073004B.png.2ad3b92154c7f88610a936eaf3732aae.png

Edited by nicknorman
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2 minutes ago, Jon57 said:

Thought you were a monster!! Go on upset them lovely Trojan’s 

Well anyway, a quick google turned up this article, which suggests that charging from a 14.4v alternator is fine. Charging from a smart lead acid battery charger is less fine as it is likely to go to float far too soon.

https://www.powerstream.com/LLLF.htm

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13 minutes ago, Jon57 said:

So as a safe guard a battery to battery charger will do the job then

I guess it would, but it would be quite an expensive solution if you chose a B2B with a high enough current rating to make the most of a large modern alternator. Since the charging graph shows the current falling right off provided the charge voltage is kept at 14.4 I doubt continued charging at 14.4 for an average boating day would be detrimental, but I’ll try to find some info on float charging eg for UPS batteries.

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1 hour ago, nicknorman said:

Yes it’s a pity Lithiums are still so pricy. But we did meet a chap on the KandA with lithiums (along with a very high tec boat) he was very pleased with them and whilst they are very expensive still, one of his points was that you get to use all the badged capacity and thus only need perhaps 1/2 the AH capacity that you would if they were LA,

Lithiums still suffer from reduced cycle count the deeper the depth of discharge.    A typical lithium (LiFePo4) cycle count is around 5000 at 50%  2000 at 80%  and 100 at 100%.     I imagine his lithiums won't last long if he uses the badged capacity!

 

1 hour ago, Mike the Boilerman said:

Lithium batteries. The big unanswered question is how do you charge them? 

The same as any other battery.  They are a lot easier to charge than wet batteries!.   People just get confused with as you may need to to wire in a extra device called a BMS.

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Not a live aboard ,but just weighing up best battery set up. Nice tug , don’t want solar to spoil the look. Old thumper engine don’t want to run forever charging lead acid batteries or a noisy generator.

Edited by Jon57
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17 minutes ago, Robbo said:

Lithiums still suffer from reduced cycle count the deeper the depth of discharge.    A typical lithium (LiFePo4) cycle count is around 5000 at 50%  2000 at 80%  and 100 at 100%.     I imagine his lithiums won't last long if he uses the badged capacity!

 

The same as any other battery.  They are a lot easier to charge than wet batteries!.   People just get confused with as you may need to to wire in a extra device called a BMS.

You missed a zero 1000 cycles at 100% DoD. Which is pretty good, I’d say! Edit: no, you didn’t just miss a zero, the figures are 2000 cycles at 100% DoD

 

but if you look at the total extractable energy it is more interesting - for example you could choose to discharge to 50% and recharge every day. Or you could discharge the same rate and over 2 days reach 100% DoD then recharge. The difference in terms of days in service is then not that much - 5000 days for daily recharging, or 4000 days for charging every other day having fully discharged. Either way, that is quite a lot of days!

Edited by nicknorman
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20 minutes ago, Robbo said:

Lithiums still suffer from reduced cycle count the deeper the depth of discharge.    A typical lithium (LiFePo4) cycle count is around 5000 at 50%  2000 at 80%  and 100 at 100%.     I imagine his lithiums won't last long if he uses the badged capacity!

 

The same as any other battery.  They are a lot easier to charge than wet batteries!.   People just get confused with as you may need to to wire in a extra device called a BMS.

 

Do you have lithiums on your boat? I have an idea due to load balancing/cell balancing issues it is not a Good Idea to have banks of them. Could you describe your installation please? many thanks!

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1 minute ago, nicknorman said:

Just started the engine. Mastershunt reading 69%, SG reading 71%. Shocking!

 

Yes shocking, as my two were reading 89% and 74% respectively, connected to the same battery bank when I left this morning!

 

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1 minute ago, Mike the Boilerman said:

 

Do you have lithiums on your boat? I have an idea due to load balancing/cell balancing issues it is not a Good Idea to have banks of them. Could you describe your installation please? many thanks!

Decent ones have electronics inside for the balancing. It is a myth that you can’t put them in parallel. Series is the problem, because once a cell is full it stops passing current thus starving other cells that might not be fully charged. Not sure how fancy ones like the Mastervolt or Victron ones cope with series but the electronics probably deals with it.

Just now, Mike the Boilerman said:

 

Yes shocking, as my two were reading 89% and 74% respectively, connected to the same battery bank when I left this morning!

 

Of course they were. As well you know, this is because they are both way out of cal in opposite directions. But it pleases you to have them like that, so we don’t mind!

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27 minutes ago, nicknorman said:

You missed a zero 1000 cycles at 100% DoD. Which is pretty good, I’d say! Edit: no, you didn’t just miss a zero, the figures are 2000 cycles at 100% DoD

 

but if you look at the total extractable energy it is more interesting - for example you could choose to discharge to 50% and recharge every day. Or you could discharge the same rate and over 2 days reach 100% DoD then recharge. The difference in terms of days in service is then not that much - 5000 days for daily recharging, or 4000 days for charging every other day having fully discharged. Either way, that is quite a lot of days!

That is better news for me then as I’m looking at lithium in the near future,  can’t find anything to support my Dod statement so I prob remembered wrong..

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33 minutes ago, Mike the Boilerman said:

 

Do you have lithiums on your boat? I have an idea due to load balancing/cell balancing issues it is not a Good Idea to have banks of them. Could you describe your installation please? many thanks!

I’m planning to get 1 or 2 RELiON’s (about 300-400ah) as they are drop in replacements.  Victron have an external BMS and more wiring but prob better if you have a modern Victron charger.

The charging settings are basically like AGM’s (although you don’t need absorption settings) and I’m guessing most of us who are looking at anything other than leisure batteries will have a customisable marine charger already.   As they can take and give the amps unlike deep cycle wet batteries, no absorption charge and take bulk charge to nearly 100% you can shorten your charge time which is a real bonus if charging via a diesel method.

Edited by Robbo
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