ND Best way to charge battery please?

Hi all, recently took the plunge and got a new 1.5 ND soft top. We used to take our old 2.5 off the road for the winter so I would took the battery off and give it the occasional charge. However we are planning to keep our new car on the road, but will probably only use it on ā€œniceā€ days. ie it may be sitting around for a while between drives.

Just wondering with all the modern electronics and stuff is it best to take the battery off and put it on charge occasionally, or just run it for 10mins every couple of weeks?

Any thoughts welcome,

Many thanks

My MK2.5 is run all year but less so in the colder months and I never use to get the timing of charging the battery right. In the end I bought a smart charge CTEK MXS 5.0 which I leave on when ever the car is not being used. Works well in my opinion and keeps the battery in optimum condition.

Buy an Aldi or Lidl smart charger and put it on every two weeks till it gets to the ā€˜maintainā€™ level. Cheap simple and effective. No need to remove the battery. Works for us.

ā€¦thanks for the reply. Ours is kept on the drive and I am not sure I want to leave a mains cable running across the drive. I will have a read of the manual and see if there is anything in there. I would be happy to run the charger out occasionally to give it a ā€œboostā€ā€¦  

Hi Malc, thans for that, I think you posted just before I replied to the last reply. Is there anything specific you need to do, or is ot just a question of connecting the charger to the main terminals? (Always a bit paranoid about modern car electrics!)

You could try a battery monitor.  I think they operate through Bluetooth, and smartphone app.

You can set an alarm for when the battery votage drops to a certain level. At which point you can

decide whether to put the battery on charge, or give the car a drive.

In my area, Lidl have their version, branded Ultimate Speed, on sale now for about Ā£20.

Iā€™ve also seen monitors on eBay for around the same price.

Some ā€œSmartā€ chargers (Ctek and Optimate for certain) come with a choice of connections either croc clips or permanent fittings.  If you fit the permanent ones (preferable!) you can just plug in their lead when necessary.  When (and if) youā€™re fitting the permanent connections to the battery terminals remember the usual practice applies, disconnect the negative terminal first and reconnect it last. 

I use both my NDā€™s infrequently and when idle I leave them connected to their ā€œOptimate 4ā€ smart chargers which keep the batteries in tip-top condition and ready to go!

  

Whatā€™s the point of paying Ā£20 for a monitor that tells you that you need to charge your battery!  Youā€™d be better off putting the money towards buying a decent ā€œSmartā€ charger!

Completely agree as a smart charger will monitor the battery condition anyway and automatically apply a charge when needed and then maintain.

I wonder if another option would be to use a solar powered trickle charger?

With the solar panel inside the car (behind the windscreen) thereā€™s no cables to trip over ??

 

No they are not ā€œSmart Chargersā€ and unless there is electronics in the solar unit to turn off the charger, that there is on a ā€œSmart Chargerā€ you could damage the battery.

I manage without a battery charger by taking my ND for a 20 min run every couple of weeks or so during the winter months. I just keep an eye on what the weather is doing and as long as itā€™s dry and the road hasnā€™t been salted I go for a spin. I think the carā€™s systems benefit from regular use and on a crisp winters day itā€™s exhilarating. 

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Have to say, I used a solar trickle charger every winter for three years and no problems with the Battery and that was on a 5 year + old battery

 

OP has already said that the car sits on the drive, and doesnā€™t want mains cables left running across the drive.

 I assume this means that he doesnā€™t want an Optimate or Ctek permanently hooked up to the car.

My MX5 gets little running in the winter, and sits on the drive, which is used by others, so Iā€™m in a similar position.

I have a multimeter, so every 10 days or so, I check the voltage. Donā€™t really need a monitor, but when it all gets

just too much effort to open the boot  to check the battery regularly ( or if I didnā€™t have a multimeter ) then a monitor

that does it all could be handy. 

Hi S, It is best practice to go directly to + on the battery with the red lead and use a handy nut for the - black lead. There a few nuts in close proximity to the battery!!!

The later Aldi/Lidl smart chargers show the voltage of the battery but a multi-meter is always handy to have in the tool box. So that is two Christmas presents sorted.

This would certainly be the case if we were in Spain where there is useful sunshine (insolation) falling on a correctly aimed Solar Panel.

However with our short winter days, low sun on the horizon, weedy panels on the market, the chances of actually finding any useful charge let alone overcharge are small. 

With the NOCO BLSOLAR2 panel I have, when I last tested it at midday midwinter on a ā€œbright sunny dayā€ in London it could barely put out enough to overcome the NC dark current, let alone cook the battery.  If I surrounded it with reflectors (opening the effective aperture) in bright midsummer then it almost rose to the rated output.

 

Hereā€™s a bit of background using my NOCO (nominally 2.5Watt) panel as an example.

The Wiki article ā€œTheory of Solar Cellsā€ gives us an excellent in-depth explanation of how they work, and if you need more info it is well worth a look.  Photons (light) enter the cell and electrons (current) leave it, and various factors affect the efficiency.  The article gives us the equations and the diagrams and the theoretical details as well as an overview.  Iā€™ll try and apply it to this device below.

 The limitations of the photovoltaic array are;

  1. The surface area (how much light it can catch, and therefore how much current.)  This is crucial.

  2. The number of cells in the array (setting the maximum open-circuit voltage.)

  3. The `intrinsicā€™ (internal) series resistance (which limits the short-circuit current regardless of how much light is hitting it.)

  4. How hot it gets (hotter means more internal leakage and lower open-circuit voltage.)

 This particular array has 31 cells (photo-diodes) arranged as stripes across the panel, and the open-circuit voltage (when it self-discharges through the 31 diodes) depends on how much light is coming in and varies from about 18V (bright indoors light, about 5mA short-circuit current) to about 27V (very bright sunlight, about 350mA short-circuit current, and that measurement in mid-summer at noon had the help of some mirrors to concentrate more light.)

 Maximum output power available from an array is a trade-off between load voltage and current and intrinsic resistance.  In the case of this Noco panel it is at its best with a normal 12V battery charging at about 13.5V with the nominal 180mA, because of the panelā€™s intrinsic series resistance of about 75 Ohms.  However it will still charge lower voltage batteries (eg 6V) with similar amounts of current, just also with lower power because more of the power is being lost in the intrinsic resistance of the panel.

 Under normal circumstances here in the UK expect it to charge at between 30mA to 100mA at midday.  So over 24 hours in winter, expect maybe 0.15AH per sunny day! And in mid summer maybe 1.2AH could be harvested.

Hello, just been reading up on this topic as due to the recent wet weather Iā€™ve not had the MX out much, if you canā€™t take the top off whatā€™s the point. Iā€™ve been having the problem of the battery going flat over a couple of days and having to connect a charger. 

Naturally Iā€™ve scoured the internet to see if its s common problem and according to another nutty MX forum if the cruise control is left on it increases the drain on the battery considerably. Now the cruise in something I donā€™t pay much attention to and it gets left on set or not. Anyway last night I made sure it was switched off and the battery last night was 12.8 and its 12.8 this morning. So there may be something in it.

 

 

 

TSB - seems to affect some RFā€™s made up to 16 May 2017.

https://www.miata.net/garage/tsb/RF%20Engine%20will%20not%20start%20due%20to%20Battery%20being%20discharged.pdf

 

Thereā€™s no particular reason why a ā€˜smartā€™ charger canā€™t go directly onto the battery terminals.  I found there was enough ā€˜spareā€™ thread on the clamps on my car to add a second nut to connect a CTEK cable.  The main reason behind this ā€˜connect the earth to the bodyā€™ I think relates to jump starting a car with a flat battery.  Having tried the starter  a few times and found it wonā€™t start the car, the car battery is likely to have gassed off some hydrogen.  Itā€™s suggested to connect the positive lead from the ā€˜back-upā€™ battery to the car battery positive first and then connect the negative of the back up battery to the car body.  Any sparks when this connection is made are then remote from the car battery.   Connecting a smart charger lead to the battery is a different scenario. 

JS