Flat Batteries and charging...

poison · Post by **poison** » Wed Jul 30, 2008 11:07 am

Like many others who don’t always get to use their MX5 regularly. I get in all ready to go just to find the battery has gone flat. So questions…

a) I have always disconnected the earth before charging the battery which is a bit of a pain, also having a battery back-up alarm system can be an issue when disconnecting the main battery. So is it OK to charge a car battery without disconnecting it? I have always assumed not due to fear of damaging the ECU, but maybe I don’t need to?
b) Has anyone used a trickle charger? Brand, cost etc?

RD5T3R · Post by **RD5T3R** » Wed Jul 30, 2008 12:16 pm

The only trickle charger I know of was a small one the size of the charger that powers Xmas lights and was a remacc alarms batt stabiliser on 06 844 1295. Just kept it topped up during the winter basically!

Cheers

Stu n Viv
RD5T3R
1998 MX5 BRG

[Posted via external email]

mx5mike · Post by **mx5mike** » Wed Jul 30, 2008 12:31 pm

I have one somewhere that I bought in the UK. It's a 12 volt 500 milliamp powerpack type charger with a couple of squeeze clamp things to go on the terminals.

It was really good over the winter when the car was outside in the cold and only driven in weekends.

Cheers.

Ian · Post by **Ian** » Wed Jul 30, 2008 12:36 pm

Yup.

I use a 'Projecta' 900mA charger from Repco. It is of the 'automatic' variety (charge and maintain), and is recommended for batteries of 100-350CCA Part number is AC150.
Have used it for 3 yrs....works a treat. Green light to indicate when battery is charged.
In my experience, Repco branches now tend to only hold in stock the next model up...1600mA, Part number AC250B. I have not used this particular one, but when I last enquired on behalf of someone else, the 900mA was available to order though the price of the two was very similar. Have always believed that slow charging is best, so very happy to continue to use the smaller one. After 2 weeks of not using the car (but alarm switched off), it fully charges my 'Panasonic' MX5 battery in about 5 hrs.

Ian

SLYDIT · Post by **SLYDIT** » Wed Jul 30, 2008 5:49 pm

i use an old battery drill charger power pack for 12 volt batteries. i think its 400mA (or is it 40mA???)charge rate. very easy .

Post by **zorruno** » Thu Jul 31, 2008 5:19 pm

poison wrote:a) I have always disconnected the earth before charging the battery which is a bit of a pain, also having a battery back-up alarm system can be an issue when disconnecting the main battery. So is it OK to charge a car battery without disconnecting it? I have always assumed not due to fear of damaging the ECU, but maybe I don’t need to?

Yes, it would be fine. The likelihood of damage to a modern ECU when connection a charger is pretty low - they have good reverse voltage protection and voltage regulation. I leave my charger connected with the battery connected for 2-3 weeks at a time sometimes. It is a 4 Amp charger with simple monitoring and trickle charge on completion (don't know what current the trickle charge is - I guess less than 100mA). I've had it charging longer, but use a better 100mA current limited power supply.

AGM batteries like the MX5 have seem to last much longer with long slow charges rather than higher current chargers for standard lead acids.

There is not a lot of stuff in a trickle charger - a regulator to produce under 200 or so mA at about 13.5 volts is about 4 components & probably less than $10 if you want to make one....

Post by **jif** » Thu Jul 31, 2008 8:31 pm

on the flip-side, I have had some unexpected FMLink-ECU (temporary) weirdness after having welding done on the exhaust ...