Open or sealed batteries

[MattS]

I think it‘s time to replace my 12V batteries.

My starter battery is 10 years old, is a Numax MV26MF, and appears to still be turning the engine over fine… but at that age it feels like I should replace for peace of mind?

My house battery is only 3 years old, a Powermax FLA 110ah Leisure (flooded) but doesn’t seem to be living up to its capacity (a couple of hours of 5-10A draw and the voltage drops down below 12V to the point that the fridge compressor won’t run).

Seems to me that on a boat that’s going to be heeling etc, a sealed battery makes more sense.

Why wouldn’t I switch to sealed for both starter and domestic?

 

[Mistroma]

I think it‘s time to replace my 12V batteries.

My starter battery is 10 years old, is a Numax MV26MF, and appears to still be turning the engine over fine… but at that age it feels like I should replace for peace of mind?

My house battery is only 3 years old, a Powermax FLA 110ah Leisure (flooded) but doesn’t seem to be living up to its capacity (a couple of hours of 5-10A draw and the voltage drops down below 12V to the point that the fridge compressor won’t run).

Seems to me that on a boat that’s going to be heeling etc, a sealed battery makes more sense.

Why wouldn’t I switch to sealed for both starter and domestic?

Do you mean AGM when talking about "sealed" or are you including low maintenance batteries. No free electrolyte in AGM and angle of heel is irrelevant. Some people describe low maintenance batteries as "sealed" as they aren't designed to require regular top ups. Most can be topped up if ever required, usually a matter of removing a sticker and removing plastic caps (usually designed to be easy to tighten and more tricky to undo ).

 

[MattS]

Sorry yes - I’m referring to low maintenance ‘wet’ batteries. Something like this Numax XV31MF Sealed Leisure Battery 12V 105Ah

Should I be considering AGM?

 

[Tranona]

If you have a split charge system and the engine battery is only used for that, 10 years is not unusual. Replacement could be any 60-70Ah battery of the type commonly used on small diesel cars that will fit the space and have the same terminal layout. House batteries are very different and you are constantly discharging and (poorly) recharging so the 2 key things to consider are capacity to take the loads you are placing on them and cycle life (the number of charge/discharge cycles). Charge acceptance and self discharge are also relevant.

I am not surprised your battery is gone after 3 years if you are regularly putting those sorts of loads on them. The rule of thumb is to keep discharge below 50% of nominal capacity, so your 5-10amps gives you between 5-10 hours capacity before you go below 50% - but this assumes your batteries are fully charged to start with, difficult unless you use shorepower or have lots of solar. So the first thing to do is conduct a power audit so you know what you are using. Big draws are fridge, electronics including autopilot and night lighting (either cabin or sailing lights). This gives you an idea of capacity and I would say that if you have all those running and sail regularly with maybe 1-2 hours motoring a day you need to double your capacity so you are using less of your capacity each day. Even then a couple of hours motoring will not replace what you have used, although there are ways you can improve this depending on your existing charging arrangements.

As to choice of batteries, much depends on how much you want to spend. Basic (100Ah) FLA are around £80, Leisure type £100 AGMs £140 upwards. Essentially the more you pay the more life you get. You might get 3-4 years out of FLA but even my basic AGMs are now in their 6th year and I expect at least 10 years. (The AGM battery in my Morgan has just entered its 19th year! - not quite the same as house batteries in usage but illustrates the low self discharge, high charge acceptance characteristics of AGMs.) The ones I have in the boat are 95Ah Exides as used in stop/start Jaguars and Land Rovers. Because of the volume sales they are 30-40% cheaper than "marine" AGMs.

Hope this helps.

 

[MattS]

Thanks - very useful.

I am not surprised your battery is gone after 3 years if you are regularly putting those sorts of loads on them

This is actually fairly abnormal - load tends to be < 2A most of the time (mainly electronics / tablet charging etc.). I had turned on the fridge to simulate a higher load, so that I could test the theory that the capacity was depleted.

below 50% of nominal capacity, so your 5-10amps gives you between 5-10 hours capacity before you go below 50%

So even with a 5A load, you’d still expect 5-10 hours capacity out of a 110ah right? The battery was definitely fully charged - I’d taken it home and put it through a proper full charge cycle and then a repair cycle, so it should have been in the best state it could be. It still only seemed to manage a couple of hours before it was dropping below 12V.

Thanks for the additional info on battery types @Tranona

 

[Refueler]

I think it‘s time to replace my 12V batteries.

My starter battery is 10 years old, is a Numax MV26MF, and appears to still be turning the engine over fine… but at that age it feels like I should replace for peace of mind?

My house battery is only 3 years old, a Powermax FLA 110ah Leisure (flooded) but doesn’t seem to be living up to its capacity (a couple of hours of 5-10A draw and the voltage drops down below 12V to the point that the fridge compressor won’t run).

Seems to me that on a boat that’s going to be heeling etc, a sealed battery makes more sense.

Why wouldn’t I switch to sealed for both starter and domestic?

OK - I don't follow the usual path as many know ... so here goes !

10 years ... that's good and maybe you could do this ...

Replace the starter battery with similar again - its a proven item... so expect similar again.
Take the starter battery and put that in place of the 'Leisure' battery ... see how that goes for a while ?

Leisure batterys are not all same .. labelling can be misleading.

Leisure batterys can be any of three types :

1. Able to be used to start an engine as well as having a slightly more discharge capability than a typical starter battery.
2. Moderately increased discharge capacity with still possibility to start small engine
3. Higher discharge capability and definitely not suitable to start an engine - it would buckle the plates !

I know some will disagree with that ... but go to a Caravan dealer and ask ...

I gave up using Leisure batterys many years ago as a caravanner and boater. They just did not have the life to justify the costs. So I started to use standard starter batterys .. in fact eventually went with breakers yard 2nd hand. I had usually longer life than the Leisures I used before ... I had possibility to use to start engine or any use ... All I had to do was to not discharge lower than about 55 - 60% level.

Sealed or not ? Does it really matter ? For me the two criteria are :

1. Physical size of the battery for locker
2. Amp/Hrs capacity.

If its not sealed / Low maintenance - then I make sure the vent tube is pointing UP !!

 

[MattS]

Replace the starter battery with similar again - its a proven item... so expect similar again.

That's kind of what I was thinking - just get another Numax (similar, as they don't make exact model any more from what I can see).

Take the starter battery and put that in place of the 'Leisure' battery ... see how that goes for a while ?

Ah not a bad idea!

If its not sealed / Low maintenance - then I make sure the vent tube is pointing UP !!

I think this was my consideration - is sealed just more appropriate to a boat that's going to be heeling over. The vent on the current Powermax points out sideways, not up, as far as I can see!

 

[Refueler]

Look at your battery and imagine how far you'd have to be heeled for any seepage.

My boat has broached twice that I know of and no fluid ever escaped from my unsealed batterys.

The only time I had battery fluid in the locker (I have a dedicated battery box under the aft divan seat) - was when a battery died and winter froze it splitting the battery in the bottom.

 

[Graham376]

I stick to open lead acid Trojans, never had a spill and can be topped up.

 

[Tranona]

Thanks - very useful.

So even with a 5A load, you’d still expect 5-10 hours capacity out of a 110ah right? The battery was definitely fully charged - I’d taken it home and put it through a proper full charge cycle and then a repair cycle, so it should have been in the best state it could be. It still only seemed to manage a couple of hours before it was dropping below 12V.

If it has only lasted 3 years with light loads then perhaps you need to look at something other than replacing with the same. I used to own a 26' pretty basic boat with just electrics, basic nav gear and an ST10000 pilot plus some use of an absorption coolbox. 105Ah Lifeline AGM charged only by a 35A Yanmar 1GM alternator. Lasted 9 years before I laid the boat up (and neglected to keep the battery charged!)

Don't think sealed/non sealed is an issue. The issue is what is the best value given your usage pattern and time horizon. Doubling capacity reduces the discharge on each battery in the bank and therefore extends life as well as enabling you to run the fridge for example without worrying about capacity. Larger capacity also increases the charge absorption rate. Spending more on a better battery of the same size will give you longer life with the same usage pattern - and the extra life is potentially greater than the extra cost.

 

[MattS]

If it has only lasted 3 years with light loads then perhaps you need to look at something other than replacing with the same.

Yes had thought similar - try a different (recommended) brand. The boat has a cheap Anself solar controller on it, and when I got it it was set to Gel battery setting, and with a stop voltage of 15V (which based on limited documentation, I think means it turns off the PV feed when the battery level reaches 15V). So I wonder if a few years of over-charging might have damaged the capacity.. I've now changed it to open lead acid setting, and a stop voltage of 13.6V

 

[Bilgediver]

Do you mean AGM when talking about "sealed" or are you including low maintenance batteries. No free electrolyte in AGM and angle of heel is irrelevant. Some people describe low maintenance batteries as "sealed" as they aren't designed to require regular top ups. Most can be topped up if ever required, usually a matter of removing a sticker and removing plastic caps (usually designed to be easy to tighten and more tricky to undo ).

Something I discovered on my car. The magic eye unscrews and allows top up. Some batteries like Numax have low height plates so that there can be a drastic loss of fluid level before they expose the plates. I prefer full size plates and top up plugs.

 

[MattS]

Something I discovered on my car. The magic eye unscrews and allows top up. Some batteries like Numax have low height plates so that there can be a drastic loss of fluid level before they expose the plates.

Interesting! The Powermax is open, and I've taken all the caps off to look at topping up, but I can't see any evidence of the plates being exposed at all, so I figured that isn't the problem with this one!

 

[Graham376]

Yes had thought similar - try a different (recommended) brand. The boat has a cheap Anself solar controller on it, and when I got it it was set to Gel battery setting, and with a stop voltage of 15V (which based on limited documentation, I think means it turns off the PV feed when the battery level reaches 15V). So I wonder if a few years of over-charging might have damaged the capacity.. I've now changed it to open lead acid setting, and a stop voltage of 13.6V

110AH is too small capacity if wanting to run fridge 24/7. Our solar is regulated with Victron Smartsolar which allows charging regime to be set up for type of battery in use, your set 15v seems rather high, many batteries charge around 14.4v before dropping to float. Looking at the amount of water our 4 x Trojans take, around 2 litres p.a., I won't consider sealed.

 

[MattS]

110AH is too small capacity if wanting to run fridge 24/7. Our solar is regulated with Victron Smartsolar which allows charging regime to be set up for type of battery in use, your set 15v seems rather high, many batteries charge around 14.4v before dropping to float. Looking at the amount of water our 4 x Trojans take, around 2 litres p.a., I won't consider sealed.

I am considering upgrading the solar controller to something like a Victron, I admit - but the panel is only 30W at the moment so not sure if it's worth it just yet!

I'm hoping reducing the stop voltage on this cheap controller will prevent it from charging too high, and should let it just provide some solar top up when available. I have a Sterling 240V 4-step charger that I also have plugged in when in the marina so that should do the bulk of in-berth charging / conditioning I hope!

 

[Rafiki]

I think it‘s time to replace my 12V batteries.

My starter battery is 10 years old, is a Numax MV26MF, and appears to still be turning the engine over fine… but at that age it feels like I should replace for peace of mind?

My house battery is only 3 years old, a Powermax FLA 110ah Leisure (flooded) but doesn’t seem to be living up to its capacity (a couple of hours of 5-10A draw and the voltage drops down below 12V to the point that the fridge compressor won’t run).

Seems to me that on a boat that’s going to be heeling etc, a sealed battery makes more sense.

Why wouldn’t I switch to sealed for both starter and domestic?

I had two open-cell expensive deep cycle batteries which I replaced with a pair of these last autumn:
Hankook DC31 Deep Cycle Leisure Battery
So far I have been very happy with their performance and they cost about a third of a like for like replacement.

 

[MattS]

I had two open-cell expensive deep cycle batteries which I replaced with a pair of these last autumn:
Hankook DC31 Deep Cycle Leisure Battery
So far I have been very happy with their performance and they cost about a third of a like for like replacement.

Would you start the engine from those? Reading the description looks like they're optimised purely for deep cycle (so I'm assuming would be damaging to use them as starter batteries?)

 

[Refueler]

Would you start the engine from those? Reading the description looks like they're optimised purely for deep cycle (so I'm assuming would be damaging to use them as starter batteries?)

True Deep Cycle should never be used to start an engine. The plates are soft and thick to give ability to deliver more of their capacity at low rates.
Starter batterys have more plates which are hard and thin - to get more area contact in the electrolyte to deliver high cranking power. But this also has the disadvantage of not suitable for deep discharge.

Many so-called Leisure batterys are a compromise so a careful check is needed.... reputable brands will quote CCA if its starter capable. If not quoted - then for me - its best not to try !

 

[ghostlymoron]

I don't see how make of battery makes any difference to which lead acid battery you get. It's pure chemistry - weight of lead is directly proportional to electrical capacity. There's a lot of nonsense talked about batteries.

 

[MattS]

I don't see how make of battery makes any difference to which lead acid battery you get. It's pure chemistry - weight of lead is directly proportional to electrical capacity. There's a lot of nonsense talked about batteries.

Just so I can understand you here - are you suggesting that manufacturer of the battery is not relevant? If so, what criteria would you evaluate to decide which batteries to purchase?