Multimeter reading of 17v

[dmr]

 

I think this can lead to confusion because one or more shorting cells will appear to lengthen charging times.

 

When compared with charging and discharging times with a new battery under a similar load :-

 

A faster charge and faster discharge = serviceable but sulphated batteries (loss of capacity).

A slower charge and faster discharge = unserviceable battery with shorting cells.

 

 

I think this can lead to confusion because one or more shorting cells will appear to lengthen charging times.

 

When compared with charging and discharging times with a new battery under a similar load :-

 

A faster charge and faster discharge = serviceable but sulphated batteries (loss of capacity).

A slower charge and faster discharge = unserviceable battery with shorting cells.

 

Point taken, but I did say "on the way out" and I believe that almost all liveaboard batteries will fail from sulphation rather than shorted cells etc.

There are always a few really obscure faults that will buck any trend, one of my Trojans had a cell that was not shorted, I always measured a decent voltage, but it would just not charge, I never got to the bottom of that one.

 

The OP wants to better understand his boats electrics which is great. My idea is that he has a permanent low cost display of Amps and Volts, and maybe even amp-hours, and gets into the habit of looking at these lots of times every day to get a "feel" for how his boat works (you cant really do this if you have to grovel about in an engine 'ole with a hand held meter). After a short time it will all make sense and problems will be spotted in good time.

 

As an example, charging amps tells me that in winter I turn off the engine well short of full charge. I also know that I should have over 80% in the batteries by early evening (but I have a Smartguage), if its much less than that then its time for remedial action such as a long charge or even a touch of equalisation.

 

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

[WotEver]

 

The OP wants to better understand his boats electrics which is great. My idea is that he has a permanent low cost display of Amps and Volts, and maybe even amp-hours, and gets into the habit of looking at these lots of times every day to get a "feel" for how his boat works (you cant really do this if you have to grovel about in an engine 'ole with a hand held meter). After a short time it will all make sense and problems will be spotted in good time.

 

As an example, charging amps tells me that in winter I turn off the engine well short of full charge. I also know that I should have over 80% in the batteries by early evening (but I have a Smartguage), if its much less than that then its time for remedial action such as a long charge or even a touch of equalisation.

Great post Dave

[Tony Brooks]

 

 

Point taken, but I did say "on the way out" and I believe that almost all liveaboard batteries will fail from sulphation rather than shorted cells etc.

There are always a few really obscure faults that will buck any trend, one of my Trojans had a cell that was not shorted, I always measured a decent voltage, but it would just not charge, I never got to the bottom of that one.

 

The OP wants to better understand his boats electrics which is great. My idea is that he has a permanent low cost display of Amps and Volts, and maybe even amp-hours, and gets into the habit of looking at these lots of times every day to get a "feel" for how his boat works (you cant really do this if you have to grovel about in an engine 'ole with a hand held meter). After a short time it will all make sense and problems will be spotted in good time.

 

As an example, charging amps tells me that in winter I turn off the engine well short of full charge. I also know that I should have over 80% in the batteries by early evening (but I have a Smartguage), if its much less than that then its time for remedial action such as a long charge or even a touch of equalisation.

 

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

 

I absolutely agree.

 

The reason I posted was not so much for the OP but for others who may well be silently reading the replies to help with their own problems that we are not party to.

[hackenbush]

Thank you posters. I've read and studied and attempted to understand all the answers. I'm definitely going to have to upgrade my monitoring tools that's for sure.

My latest reading this morning was 12.54. This after Tuesday and Wednesday using 2 led lights, galley light and water pump. Not having ever measured voltage until this last week I have no idea whether that's normal for this battery. I'm hoping it is of course!

[WotEver]

Doesn't sound too bad. How often are you charging? Have you fitted an ammeter yet?

[nicknorman]

Thank you posters. I've read and studied and attempted to understand all the answers. I'm definitely going to have to upgrade my monitoring tools that's for sure.

My latest reading this morning was 12.54. This after Tuesday and Wednesday using 2 led lights, galley light and water pump. Not having ever measured voltage until this last week I have no idea whether that's normal for this battery. I'm hoping it is of course!

12.54v means around 80-85% charged which is good if you haven't charged it for a couple of days.

[hackenbush]

Doesn't sound too bad. How often are you charging? Have you fitted an ammeter yet?

That's what I was hoping to hear. I also didn't charge the battery at all yesterday as I'd run out of oil (which did seem to happen quite quickly but that's for another thread perhaps!).

Due to budget constraints I think the ammeter will have to wait until the new year

12.54v means around 80-85% charged which is good if you haven't charged it for a couple of days.

So, from what I've learned so far this would be the perfect time to charge it back to full?

[nicknorman]

That's what I was hoping to hear. I also didn't charge the battery at all yesterday as I'd run out of oil (which did seem to happen quite quickly but that's for another thread perhaps!).

Due to budget constraints I think the ammeter will have to wait until the new year

 

So, from what I've learned so far this would be the perfect time to charge it back to full?

It's always the perfect time to charge! But being pragmatic you could probably go another day without charging if that were more convenient. I just want to check one thing - do you have any solar? If so you have to be careful that the solar isn't raising the voltage a bit if you take a measurement in daylight.

[hackenbush]

It's always the perfect time to charge! But being pragmatic you could probably go another day without charging if that were more convenient. I just want to check one thing - do you have any solar? If so you have to be careful that the solar isn't raising the voltage a bit if you take a measurement in daylight.

I have panels but they're not wired in yet. I'm planning on doing this soon although from everything I've read on the forum there's no rush to do this in winter

[MtB]

12.54v means around 80-85% charged which is good if you haven't charged it for a couple of days.

 

 

Are we sure about that?

 

My batteries are showing 25.04V on the BMV702, 71% SoC on the Smargauge (and curiously, 94% SoC on the BM2).

 

I have grave doubts about those SoC voltage charts especially at the higher SoCs. Does 12.73V resting voltage always mean 100% SoC? A new and easy way of knowing 100% perhaps!

Edited December 1, 2016 by Mike the Boilerman

[Tony Brooks]

At about 09.30 yesterday morning my 65 watt panel was producing a battery charge of 0.5 amp and it would have got more as the morning wore on. Lets guess the average yesterday was 0.75 amp then six hours an 0.75 amp = 4.5 Ah. I suspect that with a 100 watt panel it would be closer to delivering about 1.5 amps on average so that is 6 x 1.5 = 9 Ah a day. That may well be enough to power your LED lamps. I would suggest that while we have these cold sunny conditions it would be well worth connecting the panel(s).

[nicknorman]

Are we sure about that?

 

My batteries are showing 25.04V on the BM2, 71% SoC on the Smargauge (and curiously, 94% SoC on the BM2).

 

I have grave doubts about those SoC voltage charts especially at the higher SoCs. Does 12.73V resting voltage always mean 100% SoC? A new and easy way of knowing 100% perhaps!

Not totally sure since it varies a bit according to the exact chemistry (calcium, antimony etc) but anyway, with batteries nothing is certain (except death and flattening). But anyway I think we can say the SoC is "reasonable".

 

Did you ever recalibrate the voltage reading on your Smartgauge?

[Geo]

12.54v means around 80-85% charged which is good if you haven't charged it for a couple of days.

 

A very good situation from where the OP started from.

 

What it actually is as a SoC I suggest does not matter, I suspect with freezing temperatures etc 12.5+ is a very good reading

[WotEver]

I have panels but they're not wired in yet. I'm planning on doing this soon although from everything I've read on the forum there's no rush to do this in winter

Actually, cold and bright days can give great output. It's the grey overcast ones that give little or no output. And frost on the panels is a bad thing. No doubt if you get them wired up in the next week or so this current weather trend will break.

[MtB]

Actually, cold and bright days can give great output. It's the grey overcast ones that give little or no output. And frost on the panels is a bad thing. No doubt if you get them wired up in the next week or so this current weather trend will break.

 

 

Yes my 560W of solar is currently pushing out 3.9A into 24V batteries! Full sunshine very low in the sky, and panels flat on roof. If I tipped them up to face the sun I'd imagine doubling this or more.

 

On the other hand on a grey dull day this time of year the controller shows zero, or possibly 0.1A or 0.2A.

Not totally sure since it varies a bit according to the exact chemistry (calcium, antimony etc) but anyway, with batteries nothing is certain (except death and flattening). But anyway I think we can say the SoC is "reasonable".

 

Did you ever recalibrate the voltage reading on your Smartgauge?

 

 

No. Each time I decide to do it, the practical difficulties of disconnecting it whilst pressing two buttons (or something similar) defeats me, as it is 25ft from the batteries! I need a second pair or hands, or to install a switch in the line or something.

 

I've grown used to knowing it reads 0.27V too high. My new BMV702 and the new solar controller both confirm this.

 

The bit that concerns me is whether this 'over reading' affects it's SoC calculations, or whether the displayed voltage is unrelated to the algorithm.

 

 

 

Edit to move the decimal place

Edited December 1, 2016 by Mike the Boilerman

[hackenbush]

That's good to know re panels. I'll fast forward my wiring project

[chubby]

I have panels but they're not wired in yet. I'm planning on doing this soon although from everything I've read on the forum there's no rush to do this in winter

For reasons involving laborious long term and difficult studies i really don t get to go boating ( i liveaboard ) as much as poss & so my boat is mostly moored up .

I find in winter that solar is completely effective BUT this is because i tailor my electrical needs to what my solar can provide as opposed to tailoring my solar to what electrical power i want .

Im careful with my electrical usage .

So , if Hackenbush , your needs are humble regarding electrical power then i would get than panel wired up ASAP

. Where u are it ought to be bright and sunny today and there would be a definate advantage to having your solar installed on days of a similar nature .

My boat runs off solar all year with usage very different in summer and winter but i find that the solar provides for me .

I have 400 w of panels laid flat and 4x 110ah of batts .

 

Id get onto fitting that panel as a priority because it will help on bright sunny days . If u can combine it with a smartgauge as soon as financially viable then i think you ll be on the way towards very much improving your charging / monitoring routine . Whats more as time moves on you can look to add more solar and more batts again if funds allow

 

Just my tuppence

Edited December 1, 2016 by chubby

[MtB]

I seem to remember the op saying the reason for not fitting his solar oanel was lack of funds for the cables and a controller.

 

The correct cables and a controller are not strictly necessary and on a sunny winter day like today it seems criminal not to jury-rig the panel to the battery using any old bits of wire that can be found. The charge current will be modest anyway with the sum so low and a controller is only really necessary for permanent installations. If I were the OP I'd just connect the panel wires directly to the battery terminals now. I'd suggest only doing this while on the boat and able to supervise the charging.

[nicknorman]

I seem to remember the op saying the reason for not fitting his solar oanel was lack of funds for the cables and a controller.

The correct cables and a controller are not strictly necessary and on a sunny winter day like today it seems criminal not to jury-rig the panel to the battery using any old bits of wire that can be found. The charge current will be modest anyway with the sum so low and a controller is only really necessary for permanent installations. If I were the OP I'd just connect the panel wires directly to the battery terminals now. I'd suggest only doing this while on the boat and able to supervise the charging.

Yes I'd agree with that, and connect the panels in parallel for the time being.

[MtB]

Yes I'd agree with that, and connect the panels in parallel for the time being.

Thats possibly overcomplicating things if there is more than one panel available. I'd suggest starting by just connecting up a single panel to start with. Then add in a second if it works!

 

An ammeter of some sort is about the only way of knowing if it's working though, so getting one is high priority.

(Other than seeing a small spark when initially connecting the second wire from the panel to the battery!)

[dmr]

Just to confer with the solar. I have two little and ancient 30w panels which most solar boaters would laugh at and even these are producing an amp or so, though I have angled one to face the sun.

 

I have been thinking a bit more about approaches for low cost basic liveaboard electrics, and the OP is probably one of those rare cases where a Smartguage would Not be a good investment. His electrical use (current draw) is very low, and probably zero for some hours each day, so a measure of voltage will be adequate, especially as he has a desire to learn about these things. I stand by my suggestion of a simple built in volts and amps display. It should be relatively easy to get an approximate correction between off load/rested volts and battery volts with a LED turned on.

 

However if next Christmas any of his wealthy relatives are stuck for Christmas present idea a then I am sure a Smartguage could be included.

 

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

[MtB]

Just to confer with the solar. I have two little and ancient 30w panels which most solar boaters would laugh at and even these are producing an amp or so, though I have angled one to face the sun.

 

I have been thinking a bit more about approaches for low cost basic liveaboard electrics, and the OP is probably one of those rare cases where a Smartguage would Not be a good investment. His electrical use (current draw) is very low, and probably zero for some hours each day, so a measure of voltage will be adequate, especially as he has a desire to learn about these things. I stand by my suggestion of a simple built in volts and amps display. It should be relatively easy to get an approximate correction between off load/rested volts and battery volts with a LED turned on.

 

However if next Christmas any of his wealthy relatives are stuck for Christmas present idea a then I am sure a Smartguage could be included.

 

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

Ive purchased from eBay a combined digital voltmeter and ammeter with 100a shunt for £12.49.

 

This seems the perfect tool for a boater on a low budget with a desire to learn.

 

When I get off this phone I'll post a link to it. Should have arrived yesterday but not here yet!

Edited December 1, 2016 by Mike the Boilerman

[cereal tiller]

Ive purchased from eBay a combined digital voltmeter and ammeter with 100a shunt for £12.49.

 

This seems the perfect tool for a boater on a low budget with a desire to learn.

 

When I get off this phone I'll post a link to it. Should have arrived yesterday but not here yet!

They saw you coming Mike,I just bought one same spec. for £5.07

 

CT

[MtB]

Yours will be from china. Mine is dispatched from the uk. Two weeks quicker delivery!

[cereal tiller]

Yours will be from china. Mine is dispatched from the uk. Two weeks quicker delivery!

Took four days to arrive from somewhere in't North