Battery Charger

[JeffL]

I've got the following Battery charger, see link below. I charge my Battery once every 6 months and do the same with my wife's car as we both do very little mileage with plenty of 4 to 5 mile journeys. When first connected all the indicator lights on the charger light up and as charging progresses the lights go out until the only lights remaining are the '100%' and the 'Max' lights. The instructions don't tell me if the Battery is fully charged when these two remaining lights are the only ones lit or if I should wait for the '100%' light to also go out leaving only the 'Max' light lit. I've always disconnected when those two lights are the only ones remaining lit as I've assumed the Battery to be then fully charged. It's occurred to me today to ask the question if anyone else on here has the same or similar charger and what your understanding is? Thanks

https://www.amazon.co.uk/Brookstone-6Amp-Touring-Battery-Charger/dp/B0064M5M5G

 

 

[JeffL]

Re my post above. Just to confirm, the photo in the link shows 4 circles suggesting there are 4 lights but in fact there are 6 lights, one each for MAX, 100%, 75%, 50%, 0% and Min.

[Britprius]

Hi Jeff. Sorry to answer with a rather long post, but it may give you an answer, and an incite to Battery charging. 

The charger you have is the old school resistance charger. It uses a transformer to bring down the mains voltage, and a rectifier to change the AC supply to DC for charging. It then uses a wire wound resistor as a current regulator. Effectively the resistor drops the voltage depending on the amount of current being drawn "the higher the current the greater the voltage drop".

At the start of charging the Battery voltage will be low compared with the charger, and the current will be high so the resistor drops the voltage because it is carrying a high current. As the Battery charges it's voltage goes up towards the voltage maximum output voltage of the charger the current being drawn falls, and the voltage drop of the resistor decreases  raising the output voltage to maintain the current. This is called constant current charging.

The problem with this system is it tends to overcharge batteries if left on charge for too long a period. I would stop the charging when the 100% light is on with the others turned off.

Modern chargers use a program usually to give three different charging rates:-

A high voltage to give a high current charge to charge the Battery to around 80% to 90%. This is called bulk charging. At around this level the Battery begins to refuse to accept charging, and starts to heat up.

The next stage takes over charging the Battery at a steady lower rate until the Battery reaches it's full voltage. This is a voltage "for a 12 volt battery" of 13.8 volts up to 14.2 volts depending on the type of Battery. Flooded "standard car battery", AGM  "absorbed glass mat", and AGM gel "an AGM Battery with a jelly instead of  a liquid electrolyte".

At full voltage the Battery charge voltage is bought to a level where the Battery is being charged at a few milliamps. This is called float charging, and can usually be kept up indefinitely.

A flooded Battery will be fully charged at 13.8 to 14 volts
An AGM Battery will be fully charged at 14.2 to 14.4 volts
An AGM gel battery will be fully charged at 14.2 to 14.4, but it's charge rate must be kept at or below that of the manufacturers specification. The charge rate is limited because the Battery must not be allowed to gas. This is because the gel will hold the gas as a bubble against the plates of the Battery reducing the area of contact of the gel electrolyte to the plates. In a liquid Battery the gas would simply float to the surface. In a gel battery a gas bubble is almost impossible to remove reducing the capacity of the Battery. 

John.

[JeffL]

John, I've only just seen your reply this morning. Thank you for the explanation. If I decided to replace my Battery charger with a modern one, what would you suggest I buy? There was one recommended on here (I think) which might be this one https://www.amazon.co.uk/gp/product/B00FC42HAA/ref=ox_sc_saved_title_1?smid=A3P5ROKL5A1OLE&psc=1. All suggestions welcome.

Also.

I'm looking for a Portable Jump Starter to carry in the car. There was one highly recommended by someone on here, possibly Herbie or Royoftherovers? and I was looking for that thread when I came across your answer. So, I'm looking for a recommendation from someone who's actually used one, not just got one. I'll look for the other thread in the meantime. Thanks again.

 

[wendle]

I brought two of this, one for me and the other for my daughter, i have used it once on next doors van and it worked perfectly. you can get different sizes for various size engines, 

 

https://www.amazon.co.uk/dp/B01MXKJTJT/ref=pe_3187911_189395841_TE_dp_1

[Herbie]

I've got this one here and although I've not needed to use it on my own car (yet) I have used it twice to get other people started and it worked brilliantly, no problem whatsoever.

EDIT: Forgot to say that yes, that's a great choice of Battery charger.

[Britprius]

51 minutes ago, JeffL said:

John, I've only just seen your reply this morning. Thank you for the explanation. If I decided to replace my battery charger with a modern one, what would you suggest I buy? There was one recommended on here (I think) which might be this one https://www.amazon.co.uk/gp/product/B00FC42HAA/ref=ox_sc_saved_title_1?smid=A3P5ROKL5A1OLE&psc=1. All suggestions welcome.

Also.

I'm looking for a Portable Jump Starter to carry in the car. There was one highly recommended by someone on here, possibly Herbie or Royoftherovers? and I was looking for that thread when I came across your answer. So, I'm looking for a recommendation from someone who's actually used one, not just got one. I'll look for the other thread in the meantime. Thanks again.

 

Jeff. The charger you have listed is a very good charger I have to say somewhat expensive, but does come with some useful attachment leads other than crocodile clamps.
At the other end of the price scale is a similar offering from Aldi at £12-95 still with the smart functions. It has a liquid crystal display screen, settings for motor bike, car,and cold weather, and comes with a three year guarantee. It's down side is that if the electrical supply is interrupted it does not turn back on automatically.
I have two of these. One keeps my sit on mower Battery charged over the winter, and the other keeps my caravan Battery fully charged over long periods of non use. This is important because the caravan is fitted with remote control electric motor movers allowing the van to be moved by hand held remote control from outside to get it out of it's tight parking area.

I do not have experience of any jump packs. I have fitted a system in my car "basically a 300v to 12 volt inverter" that can be turned on to charge the 12volt Battery from the HV traction Battery if the 12 volt Battery should become discharged for some reason. This is a bit of overkill as I also have a 110 AH 12 volt Battery fitted, but although being disabled I like to be independent.

John.

[Alfalfa]

I replaced my Battery 3 weeks ago and have a usb with volt meter in the car and after 14 days with only short trips i did go for an 1 hour trip, the charging volt was 14.2v allmost all the way and did go down to not charging after 55min. So if you use the car like me with only 10 min trips, charging the Battery maybe once a month will make your Battery happy and last longer.

 

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[TRWeasle]

Hello there JeffL, 

I can confirm that the CTEK brand in general are excellent chargers and you can even leave it on to maintain the charge if you go away on holiday or otherwise.  
I was recommended it by a neighbour who collects classic cars.  He has 4 or 5 of those chargers permanently attached to his cars in his garage to keep them up to scratch.  

I have bought one too and have not yet used it... getting to the Battery of an RX 450h from 2012 is a feat... But I'll get there soon.  I'm actually waiting for a normal extension lead (not their pricey one) to be able to reach the Battery charge point in the fuse box.  

[i-s]

We have a CTEX MXS3.8 in our 2015 GS450h since the 12V Battery started having problems. Still haven't got to replacing the 12V, but the CTEK looks after it, and like Britprius said, it comes with a connector that you can permanently plumb into the Battery so you're not messing with croc clips - plug in and go. 

[JeffL]

Thanks for the responses on the Battery charger and the portable jump starter. I'm going to start a new thread for the portable jump starter to see if there's any other opinions. I do like the specifications of the two suggested by Wendle and Herbie but when looking at the reviews on amazon it's annoying to see quite a few people saying they're received faulty ones or they've become faulty after a short while. Anyway, let's have this discussion in the thread!.