Dual Battery

I sort of sit halfway between drivesafe and DeanoH but more on drivesafes side of the fence.

in an ideal world you have all you batteries of the same chemistry, physical construction and size as your vehicles OEM starting battery as thats what the charging system is designed to charge.

with good drive times and proper discharge discipline that will net you the longest battery life and the most useful discharge time out of the batteries.

in reality going to that much effort is generally more than its worth a stock flooded lead acid battery will quite happily take the initial 15.5 charging volts that get pushed into calcium batteries to quickly push them back up (for frequent short hop work) especially if its partly discharged, isnt the only battery in the system being charged or has a current limiter on the charging side.

Batteries are a pretty robust item, and IME they generally get taken out by other failures or abuse before they die of overcharging issues in the automotive world (providing the alternator isnt doing stupid high output voltages)

The only batteries you really have to watch for is the gel type batteries that you find in things like jump packs, ups's and emergancy lighting systems. They can punch a lot of amps in a little time or a few amps for a long time. But you cant over volt them or push too many amps in when you charge them or they will go wonky quickly.

The SC units are excellent at what they do and getting the most useful draw time out of your setup

another good thing about the SC is that they seem to be the only VSR that has a low voltage cutout on the AUX battery. to save damage to it.

I guess running it dead flat is OK if it is deeeeeeep cycle =)

Quote:

---

Originally Posted by drivesafe

Hi DeanoH, but sorry mate, most of your post is incorrect.
You can put any type battery with any other type battery and you won’t have a problem.

---

Seems like the only thing we disagree with is this statement.

Cells in flooded lead acid batterys 'gas' at around 2.25 volts per cell, for a 6 cell nominal 12 volt battery. This is around 13.5 volts. As you increase the voltage the cells gas more vigorously leading to overcharging, loss of electrolyte and premature battery failure. This is why it is inadvisable to use flooded cell type lead acid batterys in systems designed for higher voltages.
As you correctly point out, a calcium battery may not fully charge in a system designed for a conventional lead acid battery. The up side is that, all things being equal, battery life may be increased as the battery is not being 'stressed' by overcharging.

Deano:)

Can one buy a conventional flooded lead acid cell battery any more? They all seem to be calcium these days. At least, when I have bought the last 3 batteries for my Rangie and Disco. They never seem to charge fully in the Range Rover and Disco - at least the green fully charged indicator never comes up.

Even if I charge with a four stage charger the same applies and I wonder whether the charger is not designed for calcium cells.

The batteries don't seem to last very long either -- may be one year to two maximum before they need replacement.

Quote:

---

Originally Posted by p38arover

Can one buy a conventional flooded lead acid cell battery any more? They all seem to be calcium these days. At least, when I have bought the last 3 batteries for my Rangie and Disco. They never seem to charge fully in the Range Rover and Disco - at least the green fully charged indicator never comes up.

Even if I charge with a four stage charger the same applies and I wonder whether the charger is not designed for calcium cells.

The batteries don't seem to last very long either -- may be one year to two maximum before they need replacement.

---

My local BatteryZone shop still has conventional flooded lead acid batterys, but they're obsolete now, at least as far as automotive applications go. My local auto elec doesn't have them.
It's probably as simple as changing the regulator pack in your alternator to enable your system to run at the higher voltage and it won't harm the vehicles electrics, even something as electro-complicated as the P38. The extra .5 - 1 volt that the system runs at using the more efficient calcium type batterys has its greatest benefit at high current draw, ie. starting and winching.
How old is your charger and what is its rated capacity?
My 8 year old 3 stage Baintech charger has dip switch settings to select battery type, including Calcium. My 2 'phase' mobitronic charger charges up to 14.4 volts and maintains at 13.4 volts. My cheapy Projecta charges up to 14.2 volts and cuts out at 13.4 volts.
Its worth measuring the charge voltage of your charger. If it's low it may mean something as simple as a dirty connection, lead connectors or internally, or even a crook diode. Thermal cutout relays often go 'high resistance' and introduce voltage drop in the output. This is probably the most likely potential culprit. Or it could just be that it was never designed to operate at voltages higher than 14 volts.
Another problem with sealed lead acid batterys is that if they are overcharged and gassed excessively, electrolyte is depleted and the 'magic eye' will no longer work because the electrolyte level is too low. Perhaps the car regulator is overcharging? The battery may be OK, ie. electrolyte level above the plates, but you are unable to measure it.:)

So there you are Ron. Your charging voltage is either too high or too low. Get a good voltmeter and do a bit of super sluething.

Hope that helped.

Deano:)

The 4-stage charger is about two years old. It's an MB3620 sold under a variety of names.

See https://www.soanarplus.com/getProduc...?prodId=MB3620

I later found the same manufacturer makes a model for calcium batteries but I haven't seen it for sale in Australia.

Re multimeters, I have many ranging from the analogue taut band suspension unit I built as a trainee electronics tech in 1966, an analogue AVO 8, Simpson (US) transistorised analogue VTVM, to a Hewlett-Packard DVM - and lots of other DVMs in between.

Crikey Ron I'm suprised you bought it.

From your linked advertisment

.................We will send you your new battery cahrger to you Freight Free.:D

I'm glad I'm not the only one still using an old Avo8. Excellent for auto electric fault finding with its low input impedance. Though I use a Fluke 8020B for general use. My eyes aren't what they used to be and the Fluke it is a very good meter. I think the VTVM might be a bit of overkill. The bees knees of high impedance meters in the 1960/70's. And then someone invented FET's, and as they say........... its all history now.
Anyway enough reminiscing, done any super-sluething yet?

Deano

Quote:

---

Originally Posted by DeanoH

Cells in flooded lead acid batterys 'gas' at around 2.25 volts per cell, for a 6 cell nominal 12 volt battery. This is around 13.5 volts. As you increase the voltage the cells gas more vigorously leading to overcharging, loss of electrolyte and premature battery failure.

---

Hi DeanoH, at those low voltages, gassing is not really an issue.

All batteries will be gassing by the time you reach 13.8v BUT it’s minimal and only once you exceed 14.1v for USA type AGMs ( not including Optima, Odyssey, Orbital and the likes ), 14.4 for sealed maintenance free, gel cell and Asian AGMs, and 14.7v for your good old flooded wet cell batteries that gassing is a factorable problem.

Bellow the receptive voltages for the different battery groups above, gassing is not a problem.

Furthermore, you need to exceed those voltages for some time before it becomes an irreversible problem.

Quote:

---

Originally Posted by drivesafe

Hi DeanoH, at those low voltages, gassing is not really an issue.................................Furthermore, you need to exceed those voltages for some time before it becomes an irreversible problem.

---

Hi drivesafe
Sorry don't agree, gassing is neccessary to boost charge a battery to stir up the electrolyte and avoid stratification in static installations, and to break down insoluble lead sulphate from the plates. All excessive gassing (overcharging), does is decrease battery life.

Car electrical systems have been designed to boostcharge (gas) batterys all the time. This has the benefit of stopping sulphation which is probably the biggest cause of auto battery failure. It also results in short battery life, typically 2 years for an auto battery, which is great for battery manafacturers but not so good for consumers. For a sealed battery gassing is fatal. A bit like Lucas electrics, once the smoke gets out you can't put it back in again, the component has had it.
When a battery gasses it gives off hydrogen and oxygen from the water in the electrolyte, this can be replaced in a conventional lead acid battery, if the owner ever checks it, but not in a sealed lead acid battery. Once its gone it's gone forever.
For a Gel Cell or AGM type battery overcharging is a real worry as the electrolyte is held as a 'paste' between the plates and if 'gassed' does irrepairable damage.
I think we agree on the technicalitys, but I don't agree with your casual dismissal of un-neccessary gassing.:)

Deano:)

Sorry DeanoH, but until recently, most vehicles ran at around 14.v to 14.4v and on average they got much better than 2 years out of the cranking battery and more from their auxiliary batteries.

The biggest killer of batteries is Shopping Trolley Syndrome, where the vehicle is only driven for short time periods meaning the battery is never charged properly.

Vehicles used on regular basis and driven for decent periods of time are actually far less likely to shorten the cranking batteries life span but if we were to go by your theory, the longer we drive for the more likely we are to cook the battery.

This is just not what happens.

My 03 RR did 180,000kms in 5 years and and run at a constant 14.3 at all times and it still had the original starting battery in it when I sold it.