Increasing domestic battery capacity

[Mike55]

My current domestic batteries (4 x nominal 115Ah Trojan 27TMH) are life expired. I'm considering replacing them with 4 x nominal 130Ah Trojan 30XHS batteries. There is physically enough space to take them in my battery box (they're a bit bigger in all directions) and enough clearance to get them in.  The existing battery connection cables should reach the new battery's terminals OK. The terminals are the same type.  According to the manufacturer's data sheets the charging characteristics (voltages) of both battery types are the same. My alternator is a 110 Amp unit and the battery charger is a Mastervolt Mass Combi 12/2500-100.  As this is going to be a fairly expensive outlay, is there anything I've overlooked that is going to come along and bite me on the backside? I'm intending to buy them from Tayna batteries as they appear to be the cheapest.

 

Any advice gratefully received.

Edited March 24, 2019 by Mike55

[Tony Brooks]

Nothing that I can see and doing so will reduce the cycled depth of discharge assuming the same use so potential could give a life advantage.

[nicknorman]

Should be fine.

[BruceinSanity]

How long did the last set last? Is it worth laying out large amounts of money for batteries that require a dedicated maintenance regime?

[Tony Brooks]

9 minutes ago, BruceinSanity said:

How long did the last set last? Is it worth laying out large amounts of money for batteries that require a dedicated maintenance regime?

Also my thoughts but without an answer to your question I decided to let it pass.

[Mike55]

We've had the boat about 2 1/2 years, and the current batteries were on it when we bought it. I don't know how old they were then.  As far as I can tell the charging regime for the batteries I'm proposing to buy is the same as the existing.

[dmr]

Is there any way that you can fit in the 6volt T105 or 125's? The 6 volt jobbies are better than the 12 volts, in fact they last twice as long:....

 

https://www.trojanbattery.com/products/deep-cycle-flooded/signature-line-flooded-2/

 

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

[Mike55]

The reason I'm looking at increasing the capacity of my domestic batteries is to give us greater flexibility in how long we moor without having to run the engine. We'd like to have the flexibility to moor for 2 nights rather than one. We struggled to do that on the current batteries even when they were performing OK.

[MtB]

Just now, Mike55 said:

The reason I'm looking at increasing the capacity of my domestic batteries is to give us greater flexibility in how long we moor without having to run the engine. We'd like to have the flexibility to moor for 2 nights rather than one. We struggled to do that on the current batteries even when they were performing OK.

 

Errr... batts that only last one night are not ‘performing ok’ surely. Might they br sulphated or have you ruled this out? If they are in good nick but simply too small they probably have significant value second hand. 

 

What are you using to drain them in a single night?!

[Mike55]

11 minutes ago, Mike the Boilerman said:

 

Errr... batts that only last one night are not ‘performing ok’ surely. Might they br sulphated or have you ruled this out? If they are in good nick but simply too small they probably have significant value second hand. 

 

What are you using to drain them in a single night?!

I did a test yesterday when virtually straight after switching off the charger there was insufficient capacity to start the diesel heater. I had to reconnect the charger to start the heater. By this morning the battery voltage dropped to just under 12V, on a load of a fridge, watching TV for a few hours, running the diesel heater for about 3 hours plus a small number of LED lights.

 

How do you rule out sulphation?

[Tony Brooks]

Phrases like "how long we moor without running the engine" ring alarm bells. This strongly suggests the likelihood of persistent under charging and thus a short battery life. To many it also suggests that you should not buy top line batteries until you have proven you know how to look after them and actually do so. I would suggest you practice on a set of wet open cell leisure type batteries.

 

An ordinary boater can not rule out sulphation  very easily. One way with wet cells is to compare the state of charge given by rested voltage and the hydrometer. The further they differ the more sulphated. Bowed out ends of the battery indicates sulphation but a fast dropping voltage could just as easily be one or more shorting cells.

 

What battery monitoring equipment do you have and how do you use it?

 

Study this as a first step:

 

[Mike55]

8 minutes ago, Tony Brooks said:

Phrases like "how long we moor without running the engine" ring alarm bells. This strongly suggests the likelihood of persistent under charging and thus a short battery life. To many it also suggests that you should not buy top line batteries until you have proven you know how to look after them and actually do so. I would suggest you practice on a set of wet open cell leisure type batteries.

 

An ordinary boater can not rule out sulphation  very easily. One way with wet cells is to compare the state of charge given by rested voltage and the hydrometer. The further they differ the more sulphated. Bowed out ends of the battery indicates sulphation but a fast dropping voltage could just as easily be one or more shorting cells.

 

What battery monitoring equipment do you have and how do you use it?

 

Study this as a first step:

 

I have already read that thread. The batteries I currently have and am proposing to buy are all wet open cell batteries.  The boat has a voltmeter and ammeter switchable between the domestic and starting batteries. I also have a hydrometer.

 

The boat has spent all winter on a shore supply, but when we go out over the summer we want to have the flexibility to moor somewhere for 2 nights without running the engine. I understand that a days worth of cruising is necessary to restore the batteries to 'fully' charged, but I'd like to be in the position that I don't have to do that every day, and I can occasionally go 2 nights on battery power alone.

1 hour ago, dmr said:

Is there any way that you can fit in the 6volt T105 or 125's? The 6 volt jobbies are better than the 12 volts, in fact they last twice as long:....

 

https://www.trojanbattery.com/products/deep-cycle-flooded/signature-line-flooded-2/

 

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

I hadn't really considered this - I was looking at a simple switch of similar batteries just with greater capacity. I'll look further into this. Thanks. 

[cuthound]

Many boaters who wish to stay 2 or 3 days on a mooring fit solar panels, so that for 8 months of the year the sun will help charge your batteries.

[roland elsdon]

You have something seriously amiss.

On a  new good set of batteries (220) amp hrs we can do 3 days fridge lights pumps phones before hitting our self imposed cut off of 12.3 amps. ( no tv and only a small cabin)

the addition of solar ( only 180w) makes us pretty much energy neutral in the summer.

 

I only expect 2 years out of cheap batteries and wouldnt buy expensive ones, they are too easily damaged.

 

Sorry self imposed limit of 12.3 volts off load

[WotEver]

34 minutes ago, Mike55 said:

I understand that a days worth of cruising is necessary to restore the batteries to 'fully' charged, but I'd like to be in the position that I don't have to do that every day, and I can occasionally go 2 nights on battery power alone.

A day’s worth of cruising may very well not fully charge the batteries, depending on the size of the bank and the depth of discharge. It may do, but guessing isn’t the best way to look after the batteries. Only by monitoring them can you actually know how charged they are. Either by taking a hydrometer reading or by measuring tail current at 14.4V+. 

 

As to how long you can can survive without hammering the batteries, have you done an energy audit?  Without knowing how much you use daily (or nightly or whatever) you don’t know what percentage charge you are removing from the batteries per day. If you’re only removing say 20% of their capacity then you could go two days, but if you’re using 30% of their capacity then you really shouldn’t go more than a day if you want to maximise their life. 

 

The answer to having a high daily usage isn’t simply to raise the battery capacity to cover it because you now have to consider how you’re going to replace that energy. A high depth of discharge simply won’t be replaced in the 12 hours between 8am and 8pm if you have a tiny alternator for instance. 

 

The answer to good battery life life comes from monitoring them and following three steps:

 

1. Do an energy audit to estimate your daily usage. 

2. Work out how you will replace ‘1’ daily (or 2 x ‘1’ every other day if you prefer). If you can’t balance this then reduce ‘1’.  

3. Once 1 & 2 are balanced, buy a battery bank of at least three times ‘1’ if you want to last a couple of days between charging. 

 

Oh, and with the current low price for solar panels it makes absolutely no sense these days to not have any - a decent solar installation can handle your entire daily power requirements in the summer. 

[Mike55]

40 minutes ago, roland elsdon said:

You have something seriously amiss.

 

Yes, I realise that my current set of batteries are knackered, and may have been on-their-way for some time. We've only had the boat for 2 1/2 years so the batteries are almost certainly at least 3, probably 4 years old or more.

 

23 minutes ago, WotEver said:

A day’s worth of cruising may very well not fully charge the batteries, depending on the size of the bank and the depth of discharge. It may do, but guessing isn’t the best way to look after the batteries. Only by monitoring them can you actually know how charged they are. Either by taking a hydrometer reading or by measuring tail current at 14.4V+. 

 

As to how long you can can survive without hammering the batteries, have you done an energy audit?  Without knowing how much you use daily (or nightly or whatever) you don’t know what percentage charge you are removing from the batteries per day. If you’re only removing say 20% of their capacity then you could go two days, but if you’re using 30% of their capacity then you really shouldn’t go more than a day if you want to maximise their life. 

 

The answer to having a high daily usage isn’t simply to raise the battery capacity to cover it because you now have to consider how you’re going to replace that energy. A high depth of discharge simply won’t be replaced in the 12 hours between 8am and 8pm if you have a tiny alternator for instance. 

 

The answer to good battery life life comes from monitoring them and following three steps:

 

1. Do an energy audit to estimate your daily usage. 

2. Work out how you will replace ‘1’ daily (or 2 x ‘1’ every other day if you prefer). If you can’t balance this then reduce ‘1’.  

3. Once 1 & 2 are balanced, buy a battery bank of at least three times ‘1’ if you want to last a couple of days between charging. 

 

Oh, and with the current low price for solar panels it makes absolutely no sense these days to not have any - a decent solar installation can handle your entire daily power requirements in the summer. 

Thanks for this, this is really useful stuff, especially 1, 2 & 3.  My alternator is a 110 Amp unit, which seems to be a fairly standard size. I do realise that the energy taken out of the batteries has to be replaced including allowing for loses to get back to the same place.  I haven't (yet) done an energy audit but I will do.

[dor]

1 hour ago, Mike55 said:

  My alternator is a 110 Amp unit, which seems to be a fairly standard size. I do realise that the energy taken out of the batteries has to be replaced including allowing for loses to get back to the same place.  I haven't (yet) done an energy audit but I will do.

Do remember that a 110 amp alternator will not produce 110 amps for very long, if at all.  Within minutes it will be down to 40 or 50 amps, maybe 30 in an hour, and will take several hours at less than 10 amps to finally get your batteries anywhere near 100%.

[MtB]

1 hour ago, WotEver said:

Oh, and with the current low price for solar panels it makes absolutely no sense these days to not have any - a decent solar installation can handle your entire daily power requirements in the summer. 

 

This bit is significantly understates the case for solar. Solar keeps me solar self-sufficient for eight months of the year in my liveaboard. Its only late March and already I no longer need to run the engine or generator and I don't expect to need to run either again until mid/late October. 

 

I have 560W of panels and a Tracer MPPT controller. I suggest an installation half this size would keep you going moored up indefinitely for six months of the year, even with your knackered (or small) set of Trojans.

 

Another point no-one else has made yet is Trojans are a good quality brand and if your hydrometer readings show they are sulphated, some aggressive desulphation charge cycles might well restore some lost capacity. Finding a charger to do this is near impossible though. You'll need a bench power supply.

[TheBiscuits]

7 minutes ago, Mike the Boilerman said:

Trojans are a good quality brand and if your hydrometer readings show they are sulphated, some aggressive desulphation charge cycles might well restore some lost capacity. Finding a charger to do this is near impossible though. You'll need a bench power supply.

Maybe, but here on this forum will be your best shot at it!  Where are you?

[WotEver]

24 minutes ago, dor said:

Do remember that a 110 amp alternator will not produce 110 amps for very long, if at all.  Within minutes it will be down to 40 or 50 amps, maybe 30 in an hour, and will take several hours at less than 10 amps to finally get your batteries anywhere near 100%.

Yup... due to the ‘amphour rule’ (which isn’t a rule at all, nor even totally true in all cases), the battery bank will only accept a current more or less equal to the depth of discharge. So...

 

At 90Ah discharged it will accept 90A

At 80Ah discharged it will accept 80A

At 70Ah discharged... you get the idea. 

 

That’s why charging takes so much longer than many folk realise - the closer you get to 100% SoC the slower the charge rate. It can take much longer to get from 85% to 99.99% than it did to get from 50% to 85%.