What does "matched batteries" actually mean? (1 Viewer)

Dec 30, 2015
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Been reading various threads that mention "matched batteries" where you are adding a second leisure battery. What is it that needs matching? I also read that you can add a battery with a different capacity to the first, so presumably we are matching something else. Is it just type of battery? Andrew
 

scotjimland

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Ideally, both identical.. same make , same type, same capacity (ah ) and age..

you can get away with different sizes (ah) but NOT type ie do not mix AGM, FLAs or Gels..

can also get away with different ages provided there isn't too big a difference, if so the weaker older battery will drag down the new one..

I recall one person who was so particular that they were identical, he visited the battery factory and bought two off the production line with consecutive serial numbers..
 
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acropolis22
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Many thanks. Can't see myself visiting the factory, but have logged your advice. Andrew

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scotjimland

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Funny how the manufacturers get away with putting them in parallel for on road parking ;)
manufacturers get away with lots of things... like selling leaky vans that are not fit for purpose..

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eddie

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Ideally, both identical.. same make , same type, same capacity (ah ) and age..

you can get away with different sizes (ah) but NOT type ie do not mix AGM, FLAs or Gels..

can also get away with different ages provided there isn't too big a difference, if so the weaker older battery will drag down the new one..

I recall one person who was so particular that they were identical, he visited the battery factory and bought two off the production line with consecutive serial numbers..
Good post
 

Lenny HB

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Funny how the manufacturers get away with putting them in parallel for on road charging;)
I know you have a thing about that Eddie, but in practice not that bad.
The most common situation being a Gel Leisure with a wet flooded starter battery. The alternator will be charging at Approx 14.3v which is fine for both batteries once the Gel reaches 14.3v it needs to be held there for 8 hours for a full charge so it may not get a full charge on shorter journeys, on longer ones the voltage won't worry a Gel. When charged from the mains agree it is not ideal to hold the starter battery at 14.3v for such a long period, but charge to the starter battery is normally limited to 2.5 amps so unlikely to do any harm.

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eddie

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I know you have a thing about that Eddie, but in practice not that bad.
The most common situation being a Gel Leisure with a wet flooded starter battery. The alternator will be charging at Approx 14.3v which is fine for both batteries once the Gel reaches 14.3v it needs to be held there for 8 hours for a full charge so it may not get a full charge on shorter journeys, on longer ones the voltage won't worry a Gel. When charged from the mains agree it is not ideal to hold the starter battery at 14.3v for such a long period, but charge to the starter battery is normally limited to 2.5 amps so unlikely to do any harm.
Hi Lenny, lol you right I do bring it up a lot, but really only to make people think. Us traders get a lot of stick about trying to flog things (Yes it is our job) but you would be amazed at the level of battery paranoia from some of our customers.

"Hi I have a 2016 "XYZ" Motorhome and I have space for a 2nd battery. My mate has told me that they must be exact so can you remove this perfectly good new battery and fit two "new" perfectly good batteries?

We suggest simply supplying a 2nd identical to slot in alongside what is there and it is as if we are talking rubbish lol!

GEL batteries are in my mind an expensive waste of money that have only insidiously crept into the motorhome market due to the German obsession with liquids in crashes and recycling.

Personally a lead acid battery with lids is the way to go. But I started at the Longlife Tyre and Battery Company at 16 making battery cases, soldering lead plates and filling batteries from Carboys. As it was dangerous, I at 16 being the youngest got the shitty jobs lol
 
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acropolis22
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I know you have a thing about that Eddie, but in practice not that bad.
The most common situation being a Gel Leisure with a wet flooded starter battery. The alternator will be charging at Approx 14.3v which is fine for both batteries once the Gel reaches 14.3v it needs to be held there for 8 hours for a full charge so it may not get a full charge on shorter journeys, on longer ones the voltage won't worry a Gel. When charged from the mains agree it is not ideal to hold the starter battery at 14.3v for such a long period, but charge to the starter battery is normally limited to 2.5 amps so unlikely to do any harm.
Does that imply that in an ideal world you would match the two leisure batteries, but ALSO the starter battery? Andrew
 

thehutchies

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I recall one person who was so particular that they were identical, he visited the battery factory and bought two off the production line with consecutive serial numbers..

I used to do that at the battery supplier's.
All off the same pallet, consecutive numbers.
As I was buying eight leisure batteries at a time, they were happy to humour me :)

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eddie

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Does that imply that in an ideal world you would match the two leisure batteries, but ALSO the starter battery? Andrew
If you are starting out from scratch, with an unlimited budget to build say a space shuttle, there are lots of things that you would do in an "ideal world" For example, you would have two alternators, for two battery banks, one engine and one axillary to avoid any anomalies or voltage disparagy on start up.

On a boat for example where budget is less important on design to function you will often see a twin engine set up. Each engine will control two banks of batteries, using a far more sophisticated split charging system than a relay used in 99% on European motorhomes. You will have a bank of batteries for the Port engine, a bank of batteries for the Starboard engines, another for Axillary use (house) and a fourth for bow and sturn thrusters, possibly a fifth for a generator battery system. Because they are independently charged you can use different battery types and, in turn have different charging voltages and regimes.

In a 90% of motorhomes, which are built on delivery vans, with one original alternator, we simply link all the batteries together once the engine starts to run. We energise a relay from the D1 terminal on the alternator (designed to simply put the alternator warning light out) and we use, despite how pretty the outer casing and the impressive sounding name, a simple automotive relay.

However, for 90% of motorhomes is works OK most of the time for most of the people
 

Lenny HB

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GEL batteries are in my mind an expensive waste of money that have only insidiously crept into the motorhome market due to the German obsession with liquids in crashes and recycling.
Due to personal experance I am a big fan of Gel's, prices have reduced to sensible levels now. With my Hymer requiring a low profile battery, Gel was the only choice to achieve a reasonable capacity.

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. But I started at the Longlife Tyre and Battery Company at 16 making battery cases, soldering lead plates and filling batteries from Carboys. As it was dangerous, I at 16 being the youngest got the shitty jobs lol

Also in the event you had an accident you were dispensable.:LOL: Ahh , the good old days.:D
 

Lenny HB

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I'm afraid I'm not kowledgeable enough to get your meaning. Can you elaborate? Andrew
Very few batteries made at a price that manufacturers would pay that will do both jobs satisfactorily, a leisure battery is required to give a low output over a long period be discharged to lower levels without damage, a starter battery is required to supply up to 300 amps for a very short duration and be recharged quickly. There are a few batteries at the right price that will do both jobs, but only available in a small range of capacities and case sizes so it isn't going to happen.

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acropolis22
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....................In a 90% of motorhomes, which are built on delivery vans, with one original alternator, we simply link all the batteries together once the engine starts to run. We energise a relay from the D1 terminal on the alternator (designed to simply put the alternator warning light out) and we use, despite how pretty the outer casing and the impressive sounding name, a simple automotive relay.

However, for 90% of motorhomes is works OK most of the time for most of the people

Well, most of that went over my head, but I surmise that I should have my leisure batteries and starter battery all using the same technology? Gel, lead/acid, or whatever? Thanks, BTW. Andrew
 

eddie

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Well, most of that went over my head, but I surmise that I should have my leisure batteries and starter battery all using the same technology? Gel, lead/acid, or whatever? Thanks, BTW. Andrew
I think to sum up, every time we put our heads up over the parapet with common sense advice, someone will make a "theoretical" shot, not in malice lol

I think the best analogy is if you rang my business and asked "Should I disconnect my engine battery before charging with an external charger, the advice we would give is "yes most certainly"

However, if you rang and asked "Do we bother" the answer would be no!
 

scotjimland

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I think the best analogy is if you rang my business and asked "Should I disconnect my engine battery before charging with an external charger, the advice we would give is "yes most certainly"



what we advise and what we do in practice are quite often different..

in the 'trade' known as arse covering ..

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acropolis22
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I think to sum up, every time we put our heads up over the parapet with common sense advice, someone will make a "theoretical" shot, not in malice lol

I think the best analogy is if you rang my business and asked "Should I disconnect my engine battery before charging with an external charger, the advice we would give is "yes most certainly"

However, if you rang and asked "Do we bother" the answer would be no!
Eddie, not trying to be theoretical at all, or even heretical.... You seem to be crediting me with a lot more knowledge than I have. Was just trying to get a real world answer that would help me avoid a complete cock up. :cautious::cautious:

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acropolis22
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Cor, blimey! I was only trying to find out what "matched batteries" meant. I didn't expect the Spanish Inquisition.... ;)
 

eddie

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Cor, blimey! I was only trying to find out what "matched batteries" meant. I didn't expect the Spanish Inquisition.... ;)
OK I'll try again

These batteries are matched :-
image.jpg


These batteries are NOT matched :-
image.jpg


Easier ?;)

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