Can you mix sealed and flooded batteries?

[Québec]

One of our bank of three leisure batteries (flooded) is knackered. I'd like to move to having sealed batteries, but have a sneaking suspicion I can't just add one sealed battery to the two flooded ones. Is that right? And why?

 

Edited to add: should be sealed and unsealed. Don't know why I wrote 'flooded'...must have water on the brain!

Edited April 17, 2013 by Québec

[Guest]

One of our bank of three leisure batteries (flooded) is knackered. I'd like to move to having sealed batteries, but have a sneaking suspicion I can't just add one sealed battery to the two flooded ones. Is that right? And why?

 

Edited to add: should be sealed and unsealed. Don't know why I wrote 'flooded'...must have water on the brain!

 

I know our combi. is set differently for charging gel and wet cell battery types because of the different charging characteristics so I know in our case we could not mix wet and gel.

 

However of course 'sealed' does not necessarily mean gel, a sealed wet cell is basically an open wet cell with a bit more electrolyte and a sealed top (though even then the tops can sometimes be removed with a bit of persuasion)

 

All that said when I asked a similar question last year when one of our bank went belly up the advice seemed to be it is not a good idea to mix 'n' match types within a bank because there was some suggestion that even sealed wet and open wet have different charging characteristics, I'm not sure how true this is though.

[Québec]

Thank Martin,

 

We'd be mixing sealed and unsealed wet cells.

If they DO have different charging characteristics, is that a problem? And why?

We have a 12v system with a Sterling Procharge charger.

 

Paul

[Chris Pink]

It's not a problem as such, it just means you have to charge for the lowest rated battery so instead of pushing it to 14.8V for flooded cells you have to stick to 14.4V for the sealed ones.

 

Bear in mind a lot of 'sealed' (ie 'low-maintenance') batteries can have the tops taken off anyway with a bit of force.

 

The main reason you can't charge these batteries at the higher rate is you can't replace water if it evaporates under the higher charge.

And 'sealed' doesn't mean gel. In fact they are not usually specified as 'sealed' much more likely to be called 'low-maintenance' or 'maintenance-free'

 

And I don't quite understand why you would want to 'move to having sealed batteries'?

To clarify a bit further; gel batteries are significantly differently in that if they gas the bubbles get stuck in the gel and can remove sections of plate area from the battery. This is not generally what is meant by "maintenance-free batteries"

Edited April 17, 2013 by Chris Pink

[wonderdust]

Why is that cars are quite happy to use sealed and charge at 14.8v without any problems?

Edited April 17, 2013 by wonderdust

[Chris Pink]

They don't, not without some sophisticated charging management at least, gassing voltage for a 12V battery is 14.4V. To continuously charge at higher than that voltage will require replacement of water. It will also require temperature compensation as the engine compartment of a car is quite a warm place and 14.8V will not make for a happy battery at 30°C

 

....so your 'quite happy' is, i'm afraid to say, absolute rubbish.

 

...as is your assertion that car alternator regulators are routinely set to this voltage.

Edited April 17, 2013 by Chris Pink

[wonderdust]

So the voltage readings from a Mercedes Ml, Mercedes C class, Honda VFR (gel), Vauxhall Astra and Land Rover Defender all with sealed batteries are all wrong then?

[Chris Pink]

If they are readings you have taken, put your multimeter in the bin.

 

You are wrong.

And just one example to show you're talking crap;

 

http://www.ebay.co.uk/itm/Mercedes-Benz-C-Class-1-8L-Alternator-Voltage-Regulator-SG12B062-2542582-OEM-/160960919963?pt=Motors_Car_Truck_Parts_Accessories&hash=item257a04b99b

 

others are available.

Edited April 17, 2013 by Chris Pink

[wonderdust]

I best get on to Fluke to tell them their calibrated multimeters are wrong and also inform Mercedes that their onboard diagnostic display needs to thrown in the bin!

[Chris Pink]

Suggest you read my post #6 more carefully and then go and learn something about battery chemistry and charging characteristics because at the moment you are spouting a load of arrogant rubbish.

 

if you put 14.8V charger onto a gel battery without specific precautions (ie only in the bulk stage, never in the absorption stage) you will irrepairably damage it. Fact.

 

Honda VFRs do not have this sophistication and don't charge at that voltage (in fact their regulation is pretty pants and they have a rep for destroying batteries) Later Mercedes et all probably do have some kind of current limiting (i am no expert on car power management)

 

...but the standard boat charging, whether it be solar, alternator or three stage battery charger should not charge gel batteries over 14.4V (or lower if the manufacturer recommends this)

 

and for you to suggest otherwise is ignorant rubbish.

[smileypete]

Suggest you read my post #6 more carefully and then go and learn something about battery chemistry and charging characteristics because at the moment you are spouting a load of arrogant rubbish.

 

if you put 14.8V charger onto a gel battery without specific precautions (ie only in the bulk stage, never in the absorption stage) you will irrepairably damage it. Fact.

 

Honda VFRs do not have this sophistication and don't charge at that voltage (in fact their regulation is pretty pants and they have a rep for destroying batteries) Later Mercedes et all probably do have some kind of current limiting (i am no expert on car power management)

 

...but the standard boat charging, whether it be solar, alternator or three stage battery charger should not charge gel batteries over 14.4V (or lower if the manufacturer recommends this)

 

and for you to suggest otherwise is ignorant rubbish.

Oh dear oh dear oh dear, pot... kettle... springs to mind!

 

 

Sure, gels shouldn't be charged above 14.4 but wonderdust wasn't saying otherwise, was he? And what he did politely say is very likely to be factually correct, not a 'load of arrogant rubbish'. The only arrogance is from your side sadly...

 

For a bit of an insight into why wonderdust may be more right than you think he is, have a look in the back of this PDF:

 

http://www.yuasaeurope.com/images/uploads/uk/downloads/YBSU25446_Yuasa_Cat_09_cars__light_vans_complete.pdf

 

Beyond el-cheapo leisure batts all one need to is charge them according to the manufacturers requirements. (For the former, a look at The Battery FAQ and maybe some web searching may have to do)

 

cheers, Pete.

~smpt~

Edited April 17, 2013 by smileypete

[Chris Pink]

hmmm, i assume you refer to this;

 

"Modern car charging systems allow only a small current to flow into the battery when it is fully charged. "

 

which perhaps paraphrases my "not without some sophisticated charging management at least"

 

...but in a discussion about boat charging systems, I would contend that there are few systems intelligent enough to deal with a maintenance free or gel battery in this way. and the Sterling Procharge isn't one. (nor is a Honda VFR) which is why they have gel settings which set the absorption phase below 14.4V (or in the case of the Procharge either 14.4V or 14.2V). The Procharge also sets a flooded voltage at 14.8V and a sealed voltage at 14.4V so for the original question, I hold that my original answer is exactly right.

 

The post you quoted - arrogant? yes, OK, probably is, but Mr Dust was aiming to confuse rather than elaborate.

[wonderdust]

I was not aiming to confuse anyone, all i did was to ask a question on reading i have seen, that is why i put a ? at the end of my sentence.

[Chris Pink]

OK, I apologise. To rewind, the answer is "Modern car charging systems allow only a small current to flow into the battery when it is fully charged with sophisticated charging management" absent in boats and the Sterling charger.

 

14.8V in this application is a red herring as it could be any voltage in the bulk stage that maximises the current at the battery, the battery will hold that voltage down. Absorption is the stage where the terminal voltage has risen to the charger's regulation voltage. On a gel battery that mustn't be more than 2.4V per cell (14.4 V).

 

Using the Sterling Procharge and adding a sealed battery to a flooded bank means the voltage setting goes down to 14.4V and charging is slower in the bulk stage.

[Québec]

 

1) And I don't quite understand why you would want to 'move to having sealed batteries'?

 

2)Using the Sterling Procharge and adding a sealed battery to a flooded bank means the voltage setting goes down to 14.4V and charging is slower in the bulk stage.

1) Because I quite fancy the idea of having 'maintenance-free' batteries. Am I alone in my madness? (I'm only talking about lead-acid batteries, not gel)

 

2) If I have a mixed bank, does the Sterling charger adjust automatically, or would I have to do something?

[bottle]

If I have a mixed bank, does the Sterling charger adjust automatically, no

 

or would I have to do something yes look in the manual, if you have one or look at the Sterling site or give them a 'ring'

[Chris Pink]

1) Because I quite fancy the idea of having 'maintenance-free' batteries. Am I alone in my madness? (I'm only talking about lead-acid batteries, not gel)

 

 

 

There's not much difference, essentially you are softer on them because you can't maintain them. Is it an irksome task at the moment topping them up?

[smileypete]

...but in a discussion about boat charging systems, I would contend that there are few systems intelligent enough to deal with a maintenance free or gel battery in this way. and the Sterling Procharge isn't one. (nor is a Honda VFR) which is why they have gel settings which set the absorption phase below 14.4V (or in the case of the Procharge either 14.4V or 14.2V). The Procharge also sets a flooded voltage at 14.8V and a sealed voltage at 14.4V so for the original question, I hold that my original answer is exactly right.

 

Aaargh!!! The p*xy Sterling manual rears its head again! I reckon tossing a coin would give better luck choosing the charge voltage.

 

Anyway, back to the OPs question on mixing sealed and unsealed and charge voltages...

 

Firstly unsealed; a bog standard el-cheapo non sealed/open/wet/maintainable leisure batt must be very similar, at least chemistry wise, to a non-sealed truck or car batt, and the trucks and cars which have these batts almost always charge them at a nominal 14.4V

 

Now for sealed; I think the OP is not thinking of sealed VRLA like gels/AGM, rather the el cheapo sealed for life/maintenance free/wet leisure batts, again they must be very similar to sealed truck or car batts of the same type. The trucks and cars that have these fitted sometimes charge them at a nominal 14.8V, as wonderdust says and as mentioned toward the end of the Yuasa document.

 

Moving onto charging, it seems that leaving unsealed batts 'unattended' on a high power charging source can be risky in the longer term, as there's been cases of batts boiling dry and overheating dangerously. It appears the risk of this happening goes up when the ambient temps are high, and the charge voltage is above 14.4V.

 

Also for charging el cheapo sealed leisure batts (wet not VRLA/Gel/AGM) there's been a few reports of them under performing when charged at 14.4V.

 

So for the OP I'd expect there's no one answer that will work best all the time for charging unsealed and sealed together, it all depends on the circumstances.

 

Still, the advice of the battery supplier or manufacturer, where available, should followed first and foremost. It may be worth asking the supplier of the sealed batt whether they can be charged OK at 14.4V. If it's performance does deteriorate in use, then go back and ask whether the charge voltage for the sealed bat can be raised to 14.6 or 14.8V, taking care it's never done when the batts are being charged unattended.

 

cheers, Pete.

~smpt~

Edited April 17, 2013 by smileypete

[acdbox]

Hi, I wanted to clarify as I'm in the same boat... Pardon the pun. But I got a bit confused with all the slight diverging from main question... So it'is actually possible to bank sealed/un-sealed batteries, though this is not best practice, not optimal for charging and in an ideal world not the best solution. But it will work and nothing will blow up, right?

[Tony Brooks]

Wrong - eventually something might dependant upon your charging voltage and it is likely to be a sealed battery but that depends upon the charging voltage.

 

Some sealed batteries can not accept a "typical" wet cell charging voltage and if you force them to they may dry out and eventually explode. If you reset the charging voltage to that acceptable to the sealed batteries eh wet open cell ones will not be accepting the optimum charge but at least the situation should be safe.

 

Some sealed batteries (AGM) may require a higher than "normal" charging volatile for wet cells but if you set the charging system to this no damage should be done to the wet cells AS LONG as you top them up regularly. If you do not top them up they might dry out eventually and then possibly explode.

 

I will stick my neck out and say that as long as you have no fancy charging system in use AND the alternator's regulated voltage is no more than 14.2 then it is doubtful if any battery that you are likely to afford will explode.

[Phil Ambrose]

Still a bit confused myself, I have just fitted 4 new low M/T batts which have screw caps for filling, I assumed that low maintenance in this case just means extra electrolyte and I left my charging voltage at 14.4v.

Is my world going to end with a huge explosion?

Phil

[Tony Brooks]

No. The plates probably use calcium instead of antinomy so they gas at a higher voltage and they probably have a larger reserve of electrolyte. The chemical reactions are just the same. Actually the caps may catalytically re-combine the hydrogen and oxygen produced by gassing, but probably not.

 

I just wish that battery vendors were informed enough to tell people the gassing or maximum charging voltage and better still mark it on the case. Itw ould save a lot of problems. However the gassing voltage is a bit variable over the life of a battery.

[Top cat]

When we bought Grace she was fitted with two open cell batteries and two different "sealed" batteries all wired in parallel. I knew this was bad practice and expected to be changing them quite soon. In the event they lasted another 4 years before I decided they were past it, I have no idea how long they were like that before I bought her. I replaced them with a matched set of sealed batteries mainly because acess for topping up is awful.

So while the experts will tell you not to mix types it would appear that you can get away with it.

 

Top Cat

[Tony Brooks]

Of course you can, especially with a 13.8 to 14.2 volt regulator alternator. This is why it is important to try to understand the "theory" so you know what to expect. I suspect if one of the sealed batteries were gels then the outcome might have been different.

 

The whole problem with batteries and charging is there are so many variables teh whole subject becomes confusing and so many just "turn off" and ask for black and white answers when there are none.

[acdbox]

Oh right. No there's a solar charger also.

But If it was possible to refill the sealed batteries, that would alleviate the concerns of drying/exploding.?.? there are some guides online that show how to do this. Again, not a best case solution, but one that appears the most convinient if it'd work