Solar battery maintainer

[Tim Scott]

Hi All,

Not sure if this will be of interest to anyone but inspired by an email exchange with Andy Willis, I've installed a Halfords solar battery maintainer on my garage roof and thought I'd mention it on here.

Like many of you, I guess, my 996 has sat in the garage for much of lockdown slowly flattening its battery. My garage is away from the house with no power so although I have a CTEK charger, I have to get the battery out of the car and bring it into the house to charge it. I haven't been able to keep it charged and it has gone flat a couple of times. Andy suggested I could try one of these maintainers: the Halfords one seemed to have decent reviews online (as long as you don't expect it to actively charge the battery, which I don't!) so it has been on the car for a few days now. It's too early to tell whether it'll be any use in the long term, but I am getting about 20V coming out of it during the day, so my fingers are firmly crossed...

 

[Mark Elder]

Tim - have you managed to point it towards the sun? I ask because I'm in same position as you (garage away from the house) and I installed a system (not this one) nearly a year ago but only option I had was flat on the flat garage roof. It worked great until mid November, but from then to mid-Jan it couldn't keep up with the natural 993 battery drain (plus I have a tracker which will be using some current). I guess the low sun/very short days (I'm in Stirlingshire) doesn't help. So it set off the "low-battery" alarm on the tracker a couple of times and I had to visit with my portable jumpstarter to get some volts back into it.

I've now invested in a second battery (connected in parallel) so the system has a bit more chance of having enough to get through the winter (next year).

I also have to keep an eye open for leaves getting stuck on it (if they land when wet, but dry out, they get stuck and it's interesting how the voltage drops significantly if only a low percent of cells are blocked).

 

[Tim Scott]

Hi Mark, my garage has a convenient brick "lip" which rises above the roofline against which I've secured the panel so it is at about a 45 degree angle, if that makes any sense! I'm hoping that will take care of any leaves etc but that's a great tip about making sure nothing is obscuring it. It isn't visible from sound level, so the odd trip up the ladder will be required!

I've just been out to the car and the multimeter shows that the battery has slightly more charge than when I left it on Wednesday, which I'm taking to be a good sign...

 

[T911UK]

In my experience 6 watt isn't really enough to maintain a battery in a modern Porsche in an English winter! Maybe ok in the middle of summer though, 10 watts at least really needed, you could double up and run them in parallel to give you 12 watts!

 

[Tim Scott]

I’m hoping I will maintain it through more frequent drives post-lockdown, leaving the panel just to keep it from draining too much in between... so far so good anyway, recognising that we are (hopefully!) over the worst of winter.

 

[SHRS2000]

I have the same problem!

I bought an Optimate 20W solar panel with a charge controller & battery monitor. It's been on the car for about eight weeks now & has been excellent. I had the Halfords one a while ago on another car & it did work well most of the time but wasn't so good in those short dark Winter days & I did end up with a flat battery once or twice. That said the panel was not placed optimally.

 

[Tim Scott]

Ah thanks, that’s good to hear and the Optimate definitely looks like the next step up!


I think the car’s battery may still need to be replaced after being discharged a few times over the last lockdown but hopefully having the panel up there will still help keep its replacement topped up!