Battery Condition

[stranded]

Our house battery bank (400ah agm) has recently started behaving pretty normal down to about 85% charge and then suffering serious voltage drop under anything but light loads (tv or heating, but not both). They are 9years old including 4 periods of six month liveaboard, so don’t owe us anything. But as our usage pattern has changed this year I am just wondering if it is possible to know if the symptoms I describe are of a battery dying of old age or one which has been used too much for high inverter loads - notably 100 amps of immersion heater for 25 minutes, helped by up to 25 amps of solar? Or perhaps the combination of the two factors?

 

[kwb78]

I would expect them to be failing by that point just from age, let alone running high inverter loads as well. I'd say you've done well to get 9 years out of AGMs with 2 years living aboard.

 

[Clancy Moped]

I would expect them to be failing by that point just from age, let alone running high inverter loads as well. I'd say you've done well to get 9 years out of AGMs with 2 years living aboard.

Have to agree 9 years is good going, regardless of use.

 

[stranded]

I would expect them to be failing by that point just from age, let alone running high inverter loads as well. I'd say you've done well to get 9 years out of AGMs with 2 years living aboard.

Thanks for that. Yes, pleased with the life we’ve got out of them and will replace when we come ashore in January.

Quandary is because until this year we have had a diesel genset so in the first 8 years that did the heavy lifting like hot water, though we did use the inverter regularly for shorter high load periods - kettle, coffee machine.

We are not going to replace the diesel generator and found we could do fine day to day over 5 months in Britanny this summer, including inverter hot water, with just our 400 watts (+200 so far unused in reserve) of solar.

But if such a usage pattern is going to cost me a new set of batteries every year or so, then I’ll have to bite the bullet and get a little Honda generator.

 

[Clancy Moped]

It shouldn't as long is everything is set up correctly, we ran 4.5kw gen set, water maker, tv, laptops, hot water, Eber heating in the winter, fridge 40L freezer etc, we went through a set of Rolls batteries for about 7ish years, we also had a lot of solar going on, we would do 8 months of the year on the hook like this.

 

[stranded]

It shouldn't as long is everything is set up correctly, we ran 4.5kw gen set, water maker, tv, laptops, hot water, Eber heating in the winter, fridge 40L freezer etc, we went through a set of Rolls batteries for about 7ish years, we also had a lot of solar going on, we would do 8 months of the year on the hook like this.

I’ll only know by trying it out with new batteries. Interestingly, the batteries that are dying - Stand By UPS. Batteries - were declared by a very knowledgable former forumite to be utterly unsuitable for the usage we have put them to. Some reason I suppose to hope we might do even better with a more suitable type.

 

[noelex]

When drawing 75+ amps from a 400 Ah lead acid battery bank for 25 minutes, a reasonably significant voltage drop should be expected even from a healthy battery.

This is about a C5 rate of discharge. You can look at this graph (using the C5 curve) and it will give some idea of the expected voltage of a healthy battery at various states of charge. This does vary slightly depending on battery construction. AGM batteries usually hold their voltage better under load than other types of lead acid batteries, and this graph is for a typical flooded lead acid battery, but it should give you some idea if your voltages are abnormally low.

 

[neil1967]

I’ll only know by trying it out with new batteries. Interestingly, the batteries that are dying - Stand By UPS. Batteries - were declared by a very knowledgable former forumite to be utterly unsuitable for the usage we have put them to. Some reason I suppose to hope we might do even better with a more suitable type.

I would be heading towards LiFePO4 - twice the capacity for the same physical footprint, and able to cope easily with the loads that you are placing on your batteries, as well as able to accept a veery high charge rate. Yes, they are expensive (200AH batteries can currently be had for around €700, but at least you are getting nearly 200 AH usable) - and you will probably need to redesign parts of your system, but for regular users, with high loads, they are excellent.

 

[stranded]

I would be heading towards LiFePO4 - twice the capacity for the same physical footprint, and able to cope easily with the loads that you are placing on your batteries, as well as able to accept a veery high charge rate. Yes, they are expensive (200AH batteries can currently be had for around €700, but at least you are getting nearly 200 AH usable) - and you will probably need to redesign parts of your system, but for regular users, with high loads, they are excellent.

When drawing 75+ amps from a 400 Ah lead acid battery bank for 25 minutes, a reasonably significant voltage drop should be expected even from a healthy battery.

This is about a C5 rate of discharge. You can look at this graph (using the C5 curve) and it will give some idea of the expected voltage of a healthy battery at various states of charge. This does vary slightly depending on battery construction. AGM batteries usually hold their voltage better under load than other types of lead acid batteries, and this graph is for a typical flooded lead acid battery, but it should give you some idea if voltages are abnormally low.
View attachment 167728

Really helpful - I’m going to print that out and stick it next to the battery monitor.

Keep thinking about lifepo but too complicated and not idiot proof enough for me, and I would need to replace a mastervolt combined charger/inverter and presumably reintroduce an alternator regulator, so major expense. Interested to read of a major breakthrough in sodium batteries today.

 

[Neeves]

Really helpful - I’m going to print that out and stick it next to the battery monitor.

Keep thinking about lifepo but too complicated and not idiot proof enough for me, and I would need to replace a mastervolt combined charger/inverter and presumably reintroduce an alternator regulator, so major expense.

Funny - I've been saying that - maybe, maybe you will get less expensive suggestions - or PM Kelpie.

Jonathan

 

[Neeves]

Sodium batteries are already available 'off the shelf' (at least in China). They will replace Lithium, or are replacing Lithium, in some applications but are not 'direct' replacements. They are reputed to be cheap.

Some Sodium batteries are being used in Lithium (and Sodium) hybrid applications to get the benefits of both - which suggests that the electronics needed to 'manage' Sodium might be similar, if not the same as Lithium.

It may all change within the next five years - 'it' all seems to be moving fast.

Jonathan

 

[stranded]

Sodium batteries are already available 'off the shelf' (at least in China). They will replace Lithium, or are replacing Lithium, in some applications but are not 'direct' replacements. They are reputed to be cheap.

Some Sodium batteries are being used in Lithium (and Sodium) hybrid applications to get the benefits of both - which suggests that the electronics needed to 'manage' Sodium might be similar, if not the same as Lithium.

It may all change within the next five years - 'it' all seems to be moving fast.

Jonathan

The piece I read said that the breakthrough resolves the main problem with sodium batteries - that they are much less energy dense than lithium and so need to be considerably bigger. But yes, should be cheaper and without the overheating risks.

 

[stranded]

Incidentally, I found the thread which I presume prompted your earlier suggestion to pm Kelpie and was very interested to learn that it is not necessary to have a specific lithium setting on your battery charger so long as you can make custom adjustments to the charging profile, which I can. So that would remove one cost barrier to switching.

On the other hand, my main concern is high inverter draws and it sounds like lithium is not the winner on that front. I dont really need more capacity - rarely go below 75% soc, happy cooking on gas etc. and no easy way to add more charging.

 

[johnalison]

I had an electronics chap on board recently for another job and he offered to test my batteries. I protested that they appeared to be working, but he tested them and found them to be < 40% of whatever, so they are being replaced. They were basic ‘heavy duty’ batteries from nine years ago, with the start battery from the year before. They may owe me nothing but it’s still a bill to be paid.

 

[PaulRainbow]

I had an electronics chap on board recently for another job and he offered to test my batteries. I protested that they appeared to be working, but he tested them and found them to be < 40% of whatever, so they are being replaced. They were basic ‘heavy duty’ batteries from nine years ago, with the start battery from the year before. They may owe me nothing but it’s still a bill to be paid.

If they "appeared to be working" they must have been doing the job, so why change ?

How did he test them ?

 

[Neeves]

The piece I read said that the breakthrough resolves the main problem with sodium batteries - that they are much less energy dense than lithium and so need to be considerably bigger. But yes, should be cheaper and without the overheating risks.

My take is similar, Sodium should be cheaper but you will need a larger physical space to offer the same storage as a Lithium battery. In many applications size is not an issue and some will find the costs (and safety) more seductive than the need for extra space.

I have yet to see what 'Sodium' specific kit is needed to accompany the batteries that might be unique and thus cannot accept the kit normally used for Lead and now Lithium.

I'm like you and am happy to monitor the actual data and don't see the need for the data collection offered via Blue Tooth. I can accept, easily, that others have different priorities and want different practices.. Having been brought up with Lead and without Blue Tooth we are used to watching the input amps declining as the battery fills etc.

It is sad but I project that Chinese equipment makers will soon identify the opportunities opened up by Victron - and I expect to see clones popping up everywhere - but maybe coloured red.

Jonathan

 

[johnalison]

If they "appeared to be working" they must have been doing the job, so why change ?

How did he test them ?

The charger was using more electricity than it should have and we came to the conclusion that it would not be safe to carry on charging them. I don’t know what the machine was called but I believe the read-out was given in terms of remaining capacity. As you say, they were at least working, but the odds on them packing up totally were obviously high and I didn’t want to be stuck in the middle of nowhere with a problem.

 

[noelex]

I'm like you and am happy to monitor the actual data and don't see the need for the data collection offered via Blue Tooth. I can accept, easily, that others have different priorities and want different practices.. Having been brought up with Lead and without Blue Tooth we are used to watching the input amps declining as the battery fills etc.

One of the big advantages of choosing inexpensive drop-in lithium batteries with Bluetooth is that it enables you to monitor the individual cell voltages.

With a sealed battery and an internal BMS without some form of external communication there is no warning if the cells are becoming unbalanced. The BMS will shut the battery down if an individual cell voltage becomes too high or too low, even if the overall battery voltage is acceptable. Bluetooth (or other forms of communication) provide some warning.

 

[Neeves]

One of the big advantages of choosing inexpensive drop-in lithium batteries with Bluetooth is that it enables you to monitor the individual cell voltages.

With a sealed battery and an internal BMS without some form of external communication there is no warning if the cells are becoming unbalanced. The BMS will shut the battery down if an individual cell voltage becomes too high or too low, even if the overall battery voltage is acceptable. Bluetooth (or other forms of communication) provide some warning.

So you are saying that cheap batteries with a built in BMS is safe as long as it has BlueTooth communication and safer than a cheap battery with an internal BMS, no Blue Tooth. You are saying that a battery with Blue Tooth, obviously, monitors individual batteries whereas all internal BMS, without Blue Tooth, only look at the average, and do not react to the performance to individual cells.

Do you have examples, brands, to support this as I think specific data on which brands are safe, or not, would be invaluable.

Jonathan

 

[stranded]

My take is similar, Sodium should be cheaper but you will need a larger physical space to offer the same storage as a Lithium battery. In many applications size is not an issue and some will find the costs (and safety) more seductive than the need for extra space.

I have yet to see what 'Sodium' specific kit is needed to accompany the batteries that might be unique and thus cannot accept the kit normally used for Lead and now Lithium.

I'm like you and am happy to monitor the actual data and don't see the need for the data collection offered via Blue Tooth. I can accept, easily, that others have different priorities and want different practices.. Having been brought up with Lead and without Blue Tooth we are used to watching the input amps declining as the battery fills etc.

It is sad but I project that Chinese equipment makers will soon identify the opportunities opened up by Victron - and I expect to see clones popping up everywhere - but maybe coloured red.

Jonathan

This

Battery breakthrough brings ‘unprecedented performance’ to next-gen cells — The Independent

Looks like it might be the start of bringing the size of sodium batteries down to equivalent lithium levels.