Trickle charging

[goodoldboy]

I have the twin battery setup on my 95 & was wondering how to connect up to charge.Connect to one battery or one terminal on both? I'm going to use a 100 W solar panel & charge controller so it won't be big amps .A short daily commute for months , including going back for lunch & then a couple of weeks parked up meant it needed a jump start & now the batteries have lost some of their capacity & the self discharge rate is quite high - 24 hours after a run = 12.30 V .At the moment I'm only using the car once a week & as the batteries are only 2 years old I'm reluctant to change them.

 

[Chris]

Well the main problem is that it’s a dual battery set up to begin with. Once one battery goes it’s usually curtains for the other
I think the simplest connection would be to just connect where the existing alternate supply and earth are from the factory. The problem is because you won’t be generating huge amounts of ooomph either battery that starts to fail becomes a huge resistor in effect. If you connect across both you’ll most likely not get a decent charge in either. Personally I’d drop test both batteries and replace if weak. Then charge to the main battery which then slaves if you like to the additional one
Better still get a really decent charger
Trickle charging only works on good batteries that are already full in truth

 

[Towpack]

You don't say how your dual batteries are connected, permanently in parallel as in the 24 volt start 80's or via a split charge setup (leisure use). It will make a difference. Pretty much as Chris has said, first fully charge both batteries separately then drop test each one to gauge their condition. Both being in a similar state is more important than if both are down slightly on capacity compared to new. 100w at a nominal 14v is just over 7A, with losses through the charge controller and cabling you should still get around 5-6A which is more than enough to maintain both batteries.

 

[Shayne]

Even twin battery 90's are 12v i thought .

Assuming your aim is to save money would it not help to disconnect batteries while shes laid up and a cheap solar trickle charger could the be connected to either .

 

[StarCruiser]

The 80 charges at 12v and is only switched to 24v for starting.

As far as best way to charge goes, use something like a Ctek mains charger to condition the batteries and keep them in good condition. I’m guessing that’s not an option long term. If it is, just stick with it. There are plenty of magnetic connectors that can be fixed so that they disconnect if you forget to unplug and drive away.

At the very least charge each battery over a weekend (ideally) in isolation with the Ctek. I’ve revived aged and sluggish traction batteries this way with long term good results. Once they’ve been well charged, have them tested as TP has said and go from there. A trickle charger solar panel may be ok from then on with the occasional spell on the Ctek if needed.

 

[flint]

As far as connections go, this was the answer that I got when I emailed Ctek about in car charging for the 120, if it's of any help:

"Hi

If the batteries are connected in parallell you will charge both batteries when connecting the charger.

My recommenadation is to connect the red positive clamp to one of the batteries positive pole, and the black negative clamp to the cars chassis.
Or to the charge points recommended in the vehicle manual.

Best regards
Åsa
CTEK Support"

 

[goodoldboy]

Well the main problem is that it’s a dual battery set up to begin with.

Agreed.We've discussed this before & maybe its time to bite the bullet & convert to single battery , an expensive & complicated process here in Spain.Meanwhile ill charge both batteries & do the drop test.I've got a mains charger but it's a bit complicated here with our solar power system & I might have to run the generator .For this reason I'm exploring a solar panel trickle charge.If I can maintain 12.30 that's enough to start up with the current temperatures.Shayne is right the 90 series came with a "winter pack" as an option in UK spec but it's 12V .thanks all ,I'll report back in a,few days.

 

[Chris]

But with all that sunlight and a decent solar mppt you should get more than a trickle. In decent light my 130w panel kicks out over 13 v and 6 amps. What you need is plenty of volts to push the charge in. If you try to charge a 12v battery with 12v you won't get anywhere. If you can up the voltage then even if the current is only a couple of amps, you'll be getting somewhere. It's Spain. You must have some half decent solar input available. Just make sure it's a decent solar controller.

 

[StarCruiser]

How about solar input, through a Ctek or Intervolt? Up goes the cost!!

 

[Chris]

I have two panels. One works beautifully connected to the CTEK and the other resolutely refuses to do anything. I've tried it on two units with the same result. However, connected to the mppt controller, it's performing almost as well as the one through the CTEK. I was a bit surprised. And these things are cheap - unlike the CTEK of course.

 

[StarCruiser]

My thoughts on a Ctek of any description are that they have the pulse/intelligent charging that a straight MPPT will probably not have. This is crucial to rejuvenating a damaged or aged battery but less useful in maintaining charge, hence suggesting the batteries be first given the Ctek treatment then whatever keeps them nicely charged (An MPPT for example) after that.

 

[Chris]

Agree completely Rich, but really the OP was about maintenance of charged batteries rather than raising the dead. I did say in my response, check the batteries, replace if necessary and keep topped up but you're right that an mppt is less clever than a DC to DC. But you raised the issue of cost. As we know any of these special chargers are bloomin expensive. What the CTEK in particular does is once the target battery is fully charged, it will pulse charge any other battery connected to it. I caught mine doing this for the first time recently. The rear Optima was full and every 16 seconds it gave the starter battery a 4 second pulse. TBH I thought is was buggered so contacted CTEK. They put me straight.

 

[goodoldboy]

I have a Sterling ProCharge N - a 40A digital 3 stage Marine spec charger but it's hardwired into my solar power system so I have to take the batteries out of the landcruiser & cart them up to the installation - not accessible by 4x4 .I also have a spare steca pwm charge controller that works perfectly well with another small system we occasionally run in a more remote location on the property.This is what I intend to use as a charger.
MPPT chargers , according to boat & R.V. users give on average about 8% more charge.The manual for our main system MPPT controller claims up to 25% gains but uses an example of a seriously discharged battery bank , something that should be avoided for a decent life span & completely unnecessary if you have generator back-up or a correctly sized system.

 

[goodoldboy]

pulse/intelligent charging that a straight MPPT will probably not have.

How does this differ from a normal 3 stage charger/charge controller? I've got another old charge controller hanging around , that still works that does bulk , absorption & float charge with a manual setting for equalize charging - it's about 15 years old.

 

[StarCruiser]

I’m not entirely sure but they do send pulses through the battery, https://www.ctek.com/education/battery_charging this tells a bit more.

 

[goodoldboy]

I’m not entirely sure but they do send pulses through the battery, https://www.ctek.com/education/battery_charging this tells a bit more.

"pulse maintenance mode" sounds like absorption & float charge stages.Absorption is when the controller keeps V at the maximum & lowers A .Float then lowers the V & maintains the current charge level.Once the V drops below a certain level bulk charging starts again.
The Sterling manual recommends a bulk charging V of 14.4 for sealed lead acid - about what a healthy alternator gives.The float V is given as 13.60
As for overcharging & gassing a battery this is called Equalize charging on a P.V. system something I do every month.A good quality MPPT controller will allow you to adjust this - mine is,set to 14.70 V but rises to 15.20 in the winter as the cold weather makes the panels more effective.This is to mix the electrolyte which tends to stratify in a stationary battery & level out any difference in voltage between individual cells.
Despite being "sealed" any such battery will loose electrolyte over time , even gel ones that are supposed to explode if you overcharge them! So I'm not sure if a Ctek or other expensive chargers are worth the money for maintaining an ordinary start battery but if you've got open lead acid leisure or solar batteries that are only used occasionally this seems ideal.

 

[StarCruiser]

All I can say is that the Ctek mains charger I have has performed extremely well in rejuvenating tired batteries as well as charging and maintaining them. As Chris has observed, the pulses last around 4 seconds.

At the end of the day, it appears you have your heart set on using your spare MPPT which will do a job. It’s clearly tricky to do anything else without either great effort or great expense so if neither is acceptable the only course is to use what you have.

I’m surprised the MPPT charger is allowing an over voltage which could be damaging to a battery. There have been batteries boiled in vehicles that have had such voltages from the alternator.

In a charging circuit it is the battery that controls the current it takes up to the maximum the charger can deliver. As its voltage rises, the potential difference between battery and charger decreases. An intelligent charger regulates the voltage to keep control over this current, especially being able to increase voltage when the battery is approaching a fully charged state.

Electrolyte is generally lost to evaporation especially if the battery is over charged and heated. I guess in higher ambient temps this can also contribute.

 

[Towpack]

Pulse charging has been around for quite a while. Ive still got a Pro-Peak Varipulse charger from my Model Helicopter flying days, must be almost 30 years old now. Cost £40 which was a lot at the time compared to other chargers. Fixed voltage with variable amps and Delta Peak cut off. Its aimed at NiCad/NiMiH batteries but I've recovered 6v LA batteries on it with good effect. I also have a Halfords 12v recovery/maintenance charger which must be 15 years old and works a treat. It recovered the old Vartas on the LC twice after they were drained really low with a relay fault.

 

[goodoldboy]

All I can say is that the Ctek mains charger I have has performed extremely well in rejuvenating tired batteries as well as charging and maintaining them. As Chris has observed, the pulses last around 4 seconds.

At the end of the day, it appears you have your heart set on using your spare MPPT which will do a job. It’s clearly tricky to do anything else without either great effort or great expense so if neither is acceptable the only course is to use what you have.

I’m surprised the MPPT charger is allowing an over voltage which could be damaging to a battery. There have been batteries boiled in vehicles that have had such voltages from the alternator.

In a charging circuit it is the battery that controls the current it takes up to the maximum the charger can deliver. As its voltage rises, the potential difference between battery and charger decreases. An intelligent charger regulates the voltage to keep control over this current, especially being able to increase voltage when the battery is approaching a fully charged state.

Electrolyte is generally lost to evaporation especially if the battery is over charged and heated. I guess in higher ambient temps this can also contribute.

I’m surprised the MPPT charger is allowing an over voltage

All modern charge controllers do this , as I've explained it's essential to long battery life.The process has to be carefully monitored of course & distilled water added after.Though varies on what the best bulk charge voltage is for a FLA battery.the manual for our sterling charger recommends 14.80 but I've seen a sticky on a forum that says 15.20V @80F .As for amps the C/8 rate shouldn't be exceeded.
The Ctek has a fine reputation , I wouldn't argue with that & would certainly be on my radar if I didn't already have 2 chargers & spare P.V. equipment lying around.Maybe I should look at some DC - DC connectors so I could take the Sterling down to the car?
As for recovering old batteries apart from adding Epson salts it would seem that prolonged trickle charging will de sufate an old battery.

 

[goodoldboy]

Update: after a few days of trickle charging each battery on its own the voltages are the same - I've got batteries that are 2 cm shorter than the spec so I've been swapping them over every 6 months - the self discharge rate is now zero over 25 hours.I noticed some pitting in one of the positive posts & when I started to connect everything up I noticed that the positive clamps wouldn't tighten properly ? WTF? The batteries are terminal type 1 as spec.I'm making up some shims att the moment (beer can , San Miguel if course) but obviously this isn't ideal , not sure what's going on here.