Dual battery solar charger query

[Defender08]

I have a dual battery system (main LR Varta, auxiliary Optima Yellow top) with a Sure Power battery separator (not the one that was recalled back in 2011). I run a 60 L fridge off my auxiliary battery and want to use a solar panel to charge it when I stop somewhere for a few days.


I recorded the following from an earlier thread (Dual Battery Setup, Drivesafe, 6/9/15) "when charging a number of different battery types when they are wired in parallel there is no special needs required when charging from an alternator" ... "But when charging .. from solar, these devices need to have their maximum charge voltage set to the battery in the parallel mix that has the lowest safe charge voltage".


Whilst I'm sure the battery separator works to isolate the main from the auxiliary battery, I'm not sure whether it works in reverse. If it does, then I don't have a parallel mix and so I guess I can safely connect the
solar panel via a regulator to the auxiliary battery and select for the charge voltage appropriate to the sealed Optima Yellow top battery.


Alternatively if the battery separator does not isolate the auxiliary from the main battery when the charge to the auxiliary is above 13.2 V, then will connecting my solar panel to the auxiliary battery shorten the life of my main battery?


I'm don't know where to find information on the safe charge voltages for the Varta Land Rover and Optima Yellow top batteries. In another earlier post 14.4 V and 14.1 v was the recommended charge voltages for wet and sealed batteries. Would anyone be able to advise whether these figures would apply in my case?


Thanks in advance for any advice.

[Blknight.aus]

check your alternators peak charge rate and dont go over that and you should be fine... if youve got a smart charge style alternator, find out what its sustain charge rate is and use that.

[DiscoMick]

I'm no expert, but why would connecting your solar to the auxiliary battery shorten the life of the main battery?
Wouldn't the auxiliary battery charge until whatever setting was on your dual battery controller to connect the two batteries, and then send excess charge to the starting battery? How would that hurt the starting battery?
Neither battery is likely to be 100% charged, as it usually needs a 240 volt multi-stage charger to get near 100%. Once a battery hits about 90%, it's usually a very slow process to get that final 10% charge into it.
If your fridge is running it should ensure your auxiliary battery never gets to 100%, I guess.
We've run solar panels into the camper's AGM for up to two weeks and it's never caused a problem. Our solar just has a regulator, not an MPPT controller. Mind you, when I eventually install a solar panel on the roof rack I will be fitting an MPPT as permanent solar charging is a different thing to occasional solar charging. I'll probably fit a DC-DC charger with inbuilt MPPT to control the charging and protect the battery.
Solar on vehicles is an interesting subject.

[Homestar]

Mick, it's just got to do with the batteries maximum charge voltage. I run my solar panel into several batteries - full time, they never get disconnected and they are all fine. My regulator tops out at 14.1 volts which won't kill the AGM's I'm running but if the manufacturers maximum charge voltage on the cranking battery was 13.8 volts (like a lot of older lead acid batteries) then leaving the panel connected to it would shorten it's life quite a lot. You just need to understand the mix of batteries and cater for the one with the lowest maximum charge voltage and you're sorted. :)

[DiscoMick]

Ah thanks. I'm trying to figure this stuff out myself.
My situation might be different to the OP's. My folding panels (80 Ah from Jaycar with regulator) are currently running into a one-year-old 100 Ah AGM when we go camping and it doesn't seem to be an issue, but it's not permanently mounted.
For a permanent solar mounting, say on a roof rack, do you think a regulator is enough, as in your case, or is an MPPT necessary to protect the battery?
Also, do you see any benefit in fitting a DC-DC charger which is solar compatible to boost the charge from the solar, or is it unnecessary?

[Homestar]

The regulator that comes with it is fine for permanant connection. DC DC charger is unnecessary.

[DeanoH]

As far as I can tell the 'Sure Power battery separator' is basically a (battery) coupling solenoid with a bit of associated electronics whose role is to determine whether or not to operate the solenoid to couple the battery's.

It's pretty safe to assume that with the engine not running that this solenoid is not operated. Therefore the battery's are isolated from one another when the vehicles stopped, so no problem with a solar setup to keep the aux battery charged when stopped.

Your yellow top Optima is good for a charging voltage of 14 -14.9 volts and a float voltage of 13.2 - 13.8 volts so just about any half way decent multi stage solar reg will be fine. :)

In stating the above I'm assuming you have a Defender, maybe '08 vintage ? and not some god forsaken electronic go-cart :angel:. The Varta battery is of no consequence in this scenario but it would've been nice to have the model number or type (AGM, SLA etc) in case it was an issue. :) Not picking mind but vehicle type and equipment specs help a lot for us 'sages' when pontificating. ;):D:wasntme:

Deano :)

[DiscoMick]

The regulator that comes with it is fine for permanant connection. DC DC charger is unnecessary.

Thanks for that. I'm planning to connect an Anderson plug so I can plug in our portable panels when camping. Later I'll buy a flat panel with regulator to bolt to the roof rack and connect to the battery, possibly with an Anderson plug.

Sent from my GT-P5210 using AULRO mobile app

[Defender08]

Thanks everyone for your comments. The battery is a Varta that was installed in a 2014 110 Puma - I bought it from the wreck. I'm guessing it is lead-acid.

[DiscoMick]

Thanks everyone for your comments. The battery is a Varta that was installed in a 2014 110 Puma - I bought it from the wreck. I'm guessing it is lead-acid.
So I think you said your starter battery is a Varta lead acid and your second is an Optima yellow top? If the Varta is lead acid and you have it inside the vehicle make sure the vent tube is attached and running from the battery box down under the vehicle to vent excess fumes.
I'm no expert, but I'd be very surprised if you had any problem connecting your solar panel with a regulator to either of those batteries. Your regulator should control the rate of charge and your dual battery controller will take care of the amount of current that flows from one battery to the other.
If you're worried about keeping the Optima charged for the fridge then connect direct to the Optima. Once it's charged the excess will flow to the first battery.
I've just fitted an Anderson plug to our second battery AGM so I can do just that with our portable solar panels.

[DeanoH]

................................ I'm guessing it is lead-acid.

And you are correct. ALL car batterys are lead acid batterys of one type or another.

In this case the recommended Varta battery for a 2014 Defender is the Blue Dynamic E24. 12V, 70 Ah, 630 cca. This is a sealed lead acid battery or SLA. This is a type of 'flooded cell' lead acid battery ie. if you shake it you can hear the electrolyte sloshing around inside. There are no caps on the individual cells to access the electrolyte. This is the most common type of automotive battery. Sometimes calcium or silver is added to the mix and the batterys are referred to as calcium or silver batterys but they are still lead acid batterys. These batterys must be mounted right side up.

Another type of lead acid battery is the Gell Cell where the electrolyte is not a liquid but in paste form, these were widely used as wheel chair batterys but are not so common now, in most applications they were replaced with absorbed glass matt or AGM batterys where the electrolyte is held in a fibreglass matt between the lead plates. The Optima battery is an example of this technology. As the electrolyte is not a liquid SLA's can be mounted on their side if need be.

Mick, the OP's 'Sure Power battery separator' is a (battery) coupling solenoid with associated electronics to connect the batterys together. It is basically a smart on/off switch. When the engines running and the alternator voltage is 14+ Volts it couples the batterys, with the engine off the main battery voltage drops to say 13 Volts or less and the solenoid releases. It is not a smart charge sharing device like some more complex dual battery controllers.


Deano :)

[Defender08]

A local land rover mechanic suggested that if the Optima battery becomes deeply discharged, then a charging regime based on alternator will not restore it to full charge.
Rather, it will need a charger with multi stage charging profiles specific to the chemistry of the battery under charge.

[Homestar]

Was the Mechanic trying to sell you said charger?

[drivesafe]

A local land rover mechanic suggested that if the Optima battery becomes deeply discharged, then a charging regime based on alternator will not restore it to full charge.
Rather, it will need a charger with multi stage charging profiles specific to the chemistry of the battery under charge.

Hi Defender08, and first off he is a mechanic and he should stick to being a mechanic.

Next, there is a lot of myth and magic about using a charger that can be set to charge batteries with different "chemistry"

A lot of people, who either have no idea what they are talking about, or play up to unsuspecting potential customers, about having to use a device that can charge different battery "chemistry"

There is no secret charging voltage or the need for some upside down secret handshake to be able to charge a given battery type.

This is just sales hype B/S.

The different battery type settings on battery charges, solar regulators and and DC/DC devices do nothing more than set the maximum charging voltage the device will operate at.

If you select the type of battery setting for old type USA Gel batteries, the charger will operate at no more than 14.1v.

Older Standby type AGMs at 14.4v

Most new type Standby AGMs at 14.7v

Wet Cell batteries ( including all Calcium/Calcium batteries ) can be charged at over 15v for short BOOST periods and then at a constant charge of 14.7v

Optima batteries can be charged the same as a Wet Cell.

All Land Rover AGM cranking batteries are charged at 14.7v.

This is the only difference between the different battery "chemistries" settings on a charger, no matter what type it is.

To make this B/S worse, if you have an old type USA Gel in parallel with an Optima, you must set the charger to 14.1v, to avoid cooking the old type USA Gel.

Unfortunately there are heaps of experts out there, like your mechanic, who will now tell you the Optima will never fully charge.

This again, is nothing short of a truck load of B/S.

The only difference between charging the Optima at 14.1v vs 14.7v, is that it will take a LITTLE longer for the Optima to reach a fully charged state.

Don't get caught up with all the myths about the different battery "chemistry" settings.

All they mean is that a battery that can safely tolerate a higher charge voltage, will charge slightly faster than a battery that has a lower maximum charge voltage level.

[Judo]

Hi Tim, in all these cases is the fully charged voltage of the batteries still 12.7?

[drivesafe]

Hi Tim, in all these cases is the fully charged voltage of the batteries still 12.7?

YES.

But this would be after the vehicle's motor has been off for a few hours.

When you first remove a charging device from a battery, whether it be solar, battery charger or your alternator, there will be a SURFACE CHARGE or SURFACE VOLTAGE.

This Surface Voltage can give high readings of well over 13v for a fully charge battery, which is not a problem. But it could give you a reading of 12.7v on a battery that is no where near fully charged.

So again, as long as the voltage measurement is taken a few hours after charging has ceased, then a fully charged battery should read from 12.5v ( over 90% ) to 12.75v

[DeanoH]

Some good information from Optima's website



VERY FEW BATTERIES DIE A NATURAL DEATH, MOST ARE KILLED

Tips to extend battery life - Never leave it flat

For best battery life, it is advisable to fully charge your battery prior to installation, as it can take between 10 and 50 cycles to reach full capacity (depending on battery type).

All batteries are damaged if left flat, so always remember to fully recharge your battery as soon as possible after use. Never leave it flat. Make sure your battery is maintained in a state of full charge between use.

Your battery must kept as clean as possible. Your terminals should be kept clean and tight. If your battery is flooded technology, then ensure it is watered regularly, so that the plates are always covered.

All batteries gas when in service. With valve regulated AGM and Gel batteries this gassing in normal service is recombined inside the battery whereas with flooded batteries this gas is vented externally. Even with the valve regulated technology, in cases of severe and protracted overcharge the valves may release excess gassing to ensure worse case scenarios do not occur. so please remember do not fit batteries into fully sealed air tight containers.

Charging batteries to ensure they are returned to a full state of charge and maintained that way is not rocket science. All it requires is a correctly sized battery charger set to the charge voltages recommended for the batteries you have. So please know or ask what voltage the particular battery requires to recharge correctly, and then make sure the charger has the capacity to fully charge your battery in 8 - 12 hours. A simple rule is to ensure the charger has a current output at least 10% of the C 20 A/H rating and remember always use a regulated and automatic multi-stage charger.


Deano :)

[drivesafe]

Some good information from Optima's website



VERY FEW BATTERIES DIE A NATURAL DEATH, MOST ARE KILLED

Tips to extend battery life - Never leave it flat

For best battery life, it is advisable to fully charge your battery prior to installation, as it can take between 10 and 50 cycles to reach full capacity (depending on battery type).

All batteries are damaged if left flat, so always remember to fully recharge your battery as soon as possible after use. Never leave it flat. Make sure your battery is maintained in a state of full charge between use.

Your battery must kept as clean as possible. Your terminals should be kept clean and tight. If your battery is flooded technology, then ensure it is watered regularly, so that the plates are always covered.

All batteries gas when in service. With valve regulated AGM and Gel batteries this gassing in normal service is recombined inside the battery whereas with flooded batteries this gas is vented externally. Even with the valve regulated technology, in cases of severe and protracted overcharge the valves may release excess gassing to ensure worse case scenarios do not occur. so please remember do not fit batteries into fully sealed air tight containers.

Charging batteries to ensure they are returned to a full state of charge and maintained that way is not rocket science. All it requires is a correctly sized battery charger set to the charge voltages recommended for the batteries you have. So please know or ask what voltage the particular battery requires to recharge correctly, and then make sure the charger has the capacity to fully charge your battery in 8 - 12 hours. A simple rule is to ensure the charger has a current output at least 10% of the C 20 A/H rating and remember always use a regulated and automatic multi-stage charger.


Deano :)

Hi Dean, and some good info but just be careful of the last paragraph. This info relates to batteries being used in a 24 hour cycle, like batteries in an electric forklift or being used in golf carts.

That time duration is not relevant when charging while driving, where you need to get the batteries charged as quick as possible.

[DeanoH]

A local land rover mechanic suggested that if the Optima battery becomes deeply discharged, then a charging regime based on alternator will not restore it to full charge.
Rather, it will need a charger with multi stage charging profiles specific to the chemistry of the battery under charge.

Whilst the information given to the OP by his mechanic is incorrect it is very easy to understand why especially when a reputable battery manafacturer such as Optima continues to publish rubbish like this to sell the product.


Optima Yellow Top Batteries - optima batteries (http://www.optima-batteries.com.au/optima-yellow-top-batteries.html?gclid=CPWTqu-MvMkCFQJ8vQod-88Mrg)




As Optima Batteries are all AGM batteries they do require specialized charging conditions. AGM batteries require 14.4v to charge correctly and a standard car alternator will only output 13.6v. This is where the Sterling Alternator Regulator comes in.........................

Whilst this information may have been relevant 30 years ago it is not applicable to 'modern' vehicles and IMO extremely misleading if not deceptive to use this argument in selling the product.

The last vehicle I owned that had a 13.6 volt (Lucas) alternator was my 1985 RRC so hardly a valid argument in todays environment.


Deano :)

[DiscoMick]

Yeah, my Defender is keeping the vehicle's electrical system at 13.9-14.0 volts according to the voltmeter I have plugged in, so it should have no trouble getting a battery up to the real full charge of 12.7 volts, you would think.
I thought the real benefit of a multi-stage charger was not if it would get a battery fully charged, but if it would then stop and go into float mode while some charge was used and then test and resume charging.