Batteries and monitors (again)

[boathunter]

I could search, I have read a lot on here generally. Now I have a boat with a 3.5kva generator, 80a charger, inverter and inverter charger controller, all mastervolt. And some enormous gel batteries.

All are 10+ years old including the batteries and been looked after for that time by a gent who never wanted to know how it all worked.

The controller has stored history showing 58 'cycles', deepest discharge 337ah (oops), peukert 1.27p, C.E.F. 90%. Batteries are 2 x 220ah gel.

I went away for a few days, there was nothing 12v left switched on but the battery charger wanted to do some serious charging when I got back and switched it on. I'd deliberately switched it off to see what happened.

I bought the boat knowing how old the batteries were and expecting to have to replace them, but if they still have life, there are other things ahead on the list of things to do.

However, best to start making plans and trying to judge the state of them.

 

Do the numbers from the controller mean anything useful? Or as I suspect from the low number of cycles that maybe the controller has been replaced and it's comparing 'now' with 'not that long ago' when the batteries were already on their way out.

I need to get logical but unsure how to go about it.

[WotEver]

You can safely ignore the numbers on the controller. Even if they're accurate they don't really mean anything much.

 

Charge the batteries, noting the charging current. You will note that the current slowly decreases. When it doesn't decrease over the period of an hour you can treat the batteries as 'fully charged'. Let us know what that current is (I'm going to guess around 5A).

 

Now see how long the batteries last you. Probably not very long, but let's wait and see.

 

Tony

[nicknorman]

Yes the numbers don't mean much, but perhaps the CEF gives a bit of a clue. I get 93% to 95% from our mastervolt kit. 90% is a bit on the low side suggesting the batteries are "tired" but it's not horrendous.

 

Do as Tony suggests, observe the AH taken out and having taken out a reasonable chunk of AH switch everything off and check the rested battery voltage. You can then estimate the actual SoC from the various published tables, and compare with the SoC calculated by comparing the AH taken out against the nominal (as new) capacity. This will give you an idea of what the actual capacity is now, after 10 years.

 

Incidentally the mastervolt kit tends to work on 1 cycle being one complete cycle down to zero SoC so 58 "cycles" may be 116 cycles down to 50% SoC or 232 cycles down to 75% SoC etc.

[boathunter]

Thank you Tony.

Some reading since I posted tell me cef (charge efficiency factor) and peukert exponent are set on the controller dependent on battery type.

Most interesting is the number of cycles. "Cycles are number of 35% (low battery set point) used from the battery. One cycle is counted if batteries discharged from 100% down to 0% and charged back up to 100%, or, discharged twice to 50% and back to 100%, or, 4 times to 25% and back to 100% etc."

 

Also the manual states a normal cranking battery is kaput after 50-80 cycles, semi-traction 200-250 cycles, full traction 1000-1500 cycles. Not sure where the gel batteries fit into that? Can't see any sticker on them, will look into that. If they count as traction, likely they've had it?

 

Also says it counts a cycle if down to 35% and charged to 85% or more.

 

Not sure how I can monitor charging current, the kit appears to keep that to itself and calculate the other numbers from it.

[nicknorman]

Thank you Tony.

Some reading since I posted tell me cef (charge efficiency factor) and peukert exponent are set on the controller dependent on battery type.

Most interesting is the number of cycles. "Cycles are number of 35% (low battery set point) used from the battery. One cycle is counted if batteries discharged from 100% down to 0% and charged back up to 100%, or, discharged twice to 50% and back to 100%, or, 4 times to 25% and back to 100% etc."

Also the manual states a normal cranking battery is kaput after 50-80 cycles, semi-traction 200-250 cycles, full traction 1000-1500 cycles. Not sure where the gel batteries fit into that? Can't see any sticker on them, will look into that. If they count as traction, likely they've had it?

Also says it counts a cycle if down to 35% and charged to 85% or more.

Not sure how I can monitor charging current, the kit appears to keep that to itself and calculate the other numbers from it.

Oh well maybe your mastervolt kit is different from ours but with ours, CEF is calculated automatically. What is the exact model of the kit you have?

[boathunter]

Oh well maybe your mastervolt kit is different from ours but with ours, CEF is calculated automatically. What is the exact model of the kit you have?

ah-ha! A fellow MV kit owner.

After yet another read through you are correct, it starts off with CEF figure then adjusts itself as it goes along.

The controller calls itself a Masterlink MICC. The booklet for it is dated 2001. I can't see any model numbers or other distinguishing stuff.

I've switched the charger off to see what happens. The controller doesn't seem capable of reporting what load is on the batteries.

 

More reading between posting - looks like I need to run a known load on the system for 20 hours and do some calculating?

I have a 440ah bank of 2 gel batteries and a 2kw inverter. So I need to run approx 5% of bank size as amps for a load = 22amps at 12v for 20 hours? Lord knows what I'd use for a load. 22a x 12v = 264w

Or

Use a similar load through the inverter until it shuts down on low voltage at 10.2v. The controller book suggests a light bulbs. Now I'm beginning to get confused. Could you suggest a suitable load for my battery bank / inverter? 4 x 60w light bulbs? Then some inverter losses to take into account?

 

Re read your question.

The MICC

MV mass 12/80-2

Mv mass sine 12/2000

Edited June 7, 2016 by boathunter

[nicknorman]

ah-ha! A fellow MV kit owner.

After yet another read through you are correct, it starts off with CEF figure then adjusts itself as it goes along.

The controller calls itself a Masterlink MICC. The booklet for it is dated 2001. I can't see any model numbers or other distinguishing stuff.

I've switched the charger off to see what happens. The controller doesn't seem capable of reporting what load is on the batteries.

More reading between posting - looks like I need to run a known load on the system for 20 hours and do some calculating?

I have a 440ah bank of 2 gel batteries and a 2kw inverter. So I need to run approx 5% of bank size as amps for a load = 22amps at 12v for 20 hours? Lord knows what I'd use for a load. 22a x 12v = 264w

Or

Use a similar load through the inverter until it shuts down on low voltage at 10.2v. The controller book suggests a light bulbs. Now I'm beginning to get confused. Could you suggest a suitable load for my battery bank / inverter? 4 x 60w light bulbs? Then some inverter losses to take into account?

Re read your question.

The MICC

MV mass 12/80-2

Mv mass sine 12/2000

I don't have an MICC (have different more recent stuff) but looking at the instructions you can see the present load, and also the AH taken out since fully charged, on the MICC (which has a shunt to measure current). So, starting from fully charged and pressing the AHr-time button to check the SoC is reporting 100%, just leave the batteries to discharge with any old load - fridge, light etc. 12v or mains via the inverter -doesn't matter. You can see what the current load in A is, by pressing the Volt-Amp button. Keep an eye on the voltage, don't let it get too low. The 10.2v inverter cut out is way too low, you'll damage the batteries if you take them that low unless under very heavy load. Press AHr-time button once to view the SoC and twice again to view the AH taken out.

 

So when you decide to stop the discharge, as I said before you can check the AH taken out or SoC, with the SoC derived from the rested no-load voltage, to get an idea of the % of remaining capacity vs the new capacity.

 

So for example if you stopped the discharge when the reported SoC was 75%, but the rested no-load voltage was 12.2v indicating an actual 50% SoC, you would know that the batteries are down to half capacity.

Edited June 7, 2016 by nicknorman

[boathunter]

Thanks Nick.

 

I don't really have much 12v stuff apart from lights and water pumps. TBH despite the seemingly heavy duty kit, there's only a fridge on 240 and that's going in a skip in favour of a 12v compressor version. TV's are already ousted, I'm not a TV watcher.

[nicknorman]

Tunnel lamp is typically 5A or so, if you want to intentionally drain the battery for a test. But expect lots of knocking on the boat with "excuse me, did you know that..."

[boathunter]

Tunnel lamp is typically 5A or so, if you want to intentionally drain the battery for a test. But expect lots of knocking on the boat with "excuse me, did you know that..."

I've switched off the charger, the monitor reported 100%. It thinks with 1.5a as a load it has 133 hours of power, but that particular reading has reduced to 131 hours in the first 5 minutes. Seems to have slowed down. Maybe I should have let it rest after charging? Oh well, for now I just want to know if they need replacing right away. If not I can try for more accuracy later.

 

Edit to add actually time remaining has gone back up while the fridge is off. I think I'll continue the test just behaving as normal because even if the batteries are a bit beyond it, being a low elec consumer they may well do for the summer anyway. It's not so much the cash to replace them as the difficulty/weight/size getting them out!

[nicknorman]

The time to run display is pretty useless as it will vary with the instantaneous current - as you say, it will read something different depending on whether the fridge is running or not. It also presumes that you are prepared to completely flatten your batteries and that they have the original capacity as set up in the monitor which they almost certainly don't.

 

Yes just discharge as normal and note the AH taken out and rested voltage (loads off) before starting to recharge, that will give you a ballpark idea of actual capacity.

[WotEver]

However... don't use the monitor as a guide to 100% charged. Your batteries may be well off 100% charged when the monitor says they're there, or vica-versa. You MUST use an independent method of determining when they're charged as I suggested in post #2.

 

Tony

[nicknorman]

However... don't use the monitor as a guide to 100% charged. Your batteries may be well off 100% charged when the monitor says they're there, or vica-versa. You MUST use an independent method of determining when they're charged as I suggested in post #2.

 

Tony

Yes it will depend on the settings, which we don't yet know.

[boathunter]

The time to run display is pretty useless as it will vary with the instantaneous current - as you say, it will read something different depending on whether the fridge is running or not. It also presumes that you are prepared to completely flatten your batteries and that they have the original capacity as set up in the monitor which they almost certainly don't.

 

Yes just discharge as normal and note the AH taken out and rested voltage (loads off) before starting to recharge, that will give you a ballpark idea of actual capacity.

The blurb gives the impression that it 'synchronises' capacity each time the batteries are fully charged based on the previous ah used and the charging they just got. I may have misunderstood that though. Still, if it does accurately count the ah used and measure the voltage as you say I'll have a pretty good idea how much capacity has been lost so far. It could be a few days before I have meaningful numbers (hopefully).

 

Thanks again for your help Nick, don't go away!

[boathunter]

Depending on where I read in the instruction booklet, time to run is based on an average over the previous 4, 8 or 16 minutes, or

On a table describing button levels of operation, can be set to 0, 10, 20 or 30 mins and is preset at 0 mins. I'll check that when I'm more confident, it would seem more useful set to a longer period?

[nicknorman]

The blurb gives the impression that it 'synchronises' capacity each time the batteries are fully charged based on the previous ah used and the charging they just got. I may have misunderstood that though. Still, if it does accurately count the ah used and measure the voltage as you say I'll have a pretty good idea how much capacity has been lost so far. It could be a few days before I have meaningful numbers (hopefully).

Thanks again for your help Nick, don't go away!

The "synchronising" to 100% is based on:

 

1/ all the AH taken out being replaced AND

2/ charging voltage above the set value AND

3/ charge current being below the set value AND

4/ these conditions being maintained for a set time.

 

Of these, at least 3/ is a user setting, the default is 2% of capacity which for your bank is 8.8A. This is quite a lot IMO and, unless the batteries are shagged I'd expect to be able to get the current down to 1% or less. I get it down to 0.25% after a long charge with our 2 year old batteries, which really is "fully charged". If you only charge to 100% as determined by 2%, you are likely to accumulate sulphation.

 

As Tony said right at the beginning, watching the trend in charge current is a good guide to 100% SoC and you may well find you can get it down to 1% or less. So I'd recommend checking this setting and reducing it to 1% or less to avoid chronic under-charging.

Depending on where I read in the instruction booklet, time to run is based on an average over the previous 4, 8 or 16 minutes, or

On a table describing button levels of operation, can be set to 0, 10, 20 or 30 mins and is preset at 0 mins. I'll check that when I'm more confident, it would seem more useful set to a longer period?

I'd say that the time to run is a completely useless parameter since it presumes that the present rate of discharge will be maintained until flat. In reality you don't know what the actual capacity is, hopefully you won't fully discharge the batteries, and it is unlikely that the present rate of discharged will be maintained. However nothing wrong with having a tinker if you want to!

[boathunter]

I think it's time I went through the settings to see what's what. BRB.

[boathunter]

More digging in the engine bay. I have 2 x 200ah mastervolt deep cycle gel batteries.

 

The controller is set to 200ah capacity. An arrow indicates I can only set this downwards even if I could work out how to change any values at all.

[nicknorman]

More digging in the engine bay. I have 2 x 200ah mastervolt deep cycle gel batteries.

The controller is set to 200ah capacity. An arrow indicates I can only set this downwards even if I could work out how to change any values at all.

You need to read the instructions! Long press on the select button >5 secs, to change from up arrow to down arrow. Anyway the batteries are probably at 1/2 capacity so I wouldn't bother to change it until you determine what the actual capacity is.

[Arthur Brown]

The batteries are broken when they stop doing what you want of them. Probably 50% capacity is a good point. If they work for you at the moment then charge them and see how they behave.

[boathunter]

The batteries are broken when they stop doing what you want of them. Probably 50% capacity is a good point. If they work for you at the moment then charge them and see how they behave.

I do get that, but I want numbers.

 

I've been camping in a tiny camper for the last year with a compressor fridge, lights, radio and phone charging off a 110ah battery and permanent 100w solar panel. It's not enough without hooking up twice a week for a proper charge.

Strikes me 400ah is about right for the boat and how I live, if the batteries are down to half capacity it could be a pain and better sorted sooner rather than later.

[boathunter]

You need to read the instructions! Long press on the select button >5 secs, to change from up arrow to down arrow. Anyway the batteries are probably at 1/2 capacity so I wouldn't bother to change it until you determine what the actual capacity is.

I read and am still reading the instructions, I tried that and nothing, then I read the batteries must be fully charged to set the capacity so put them back on charge. Now I read I shouldn't bother anyway so I will go back to running them down. lol, I am trying, honest.

Out of interest, might telling the monitor that the batteries had half the capacity they have from the off cause a non mech owner to charge them when down to 50% when really they were down to 75%? That could be good?

[nicknorman]

I read and am still reading the instructions, I tried that and nothing, then I read the batteries must be fully charged to set the capacity so put them back on charge. Now I read I shouldn't bother anyway so I will go back to running them down. lol, I am trying, honest.

Out of interest, might telling the monitor that the batteries had half the capacity they have from the off cause a non mech owner to charge them when down to 50% when really they were down to 75%? That could be good?

Yes it's probably better to have the capacity under-stated than over-stated for the reason you suggest.

[boathunter]

You need to read the instructions! Long press on the select button >5 secs, to change from up arrow to down arrow. Anyway the batteries are probably at 1/2 capacity so I wouldn't bother to change it until you determine what the actual capacity is.

Oh dear, fuelled by a er small Ardbeg and having charged the batteries to 100%, I thought it would be rude not to have another bash at setting the capacity. I got it to page through the possibilities, it paged down to 40ah and stopped. Can't change it from that now!

[nicknorman]

Surely a long press on select will make the arrow change direction? I've never played with an MICC but it seems unlikely the instructions are wrong?