Solar Panel trickle charger for OBD

[welland]

I have a 2006 RX400h and am fed up of the weekly flat Battery caused by not using ut enough.  So, I'm going to get a solar panel trickle charger.  I believe that all the cigar lighter sockets are disconnected when the car is locked, but the OBD port remains connecte to the Battery - and thus is a suitable place to connect the charger.  Am I correct?  

I've seen this one on eBay for £22.90:  https://www.ebay.co.uk/itm/AA-Essentials-12V-Solar-Powered-Car-Battery-Charger-Solar-Panel-OBD-Version/233409015194?hash=item365842ed9a:g:pMsAAOSwnGld1P36

Has anybody got this one?  Is it satisfactory?  

Can it be beaten on price - or on performance for similar money?  

 

[ColinBarber]

You are correct, use the OBD port at it has a permanent 12v feed.

It seems a good price, Halford do ones for a similar price but don't come with the OBD connector as standard.

 

Just remember that the power it produces is very low. It won't charge your Battery but hopefully will maintain it with 12+ hours of daylight - so make sure it is fully charged first.

[scudney]

It also won't help much if your Battery is well past it sell by date,bought the AA one myself a  few weeks ago just to keep my Battery topped up as I only use the car occasionally at the moment 

[Chris Pritchard]

During this Covid malarkey I tried an Oxford Oximiser 888 to keep my LS430 fully charged. Having been a Biker for 50 plus years, these are common with bikers. I was a little unsure as to the difference in amperage resistance  between large car batteries and the much smaller motorcycle batteries, as these Optimisers are designed to be left on indefinitely with no danger of boiling a Battery, which would happen with a regular Battery charger. However after a few days measuring the input and retained voltage, everything was fine. To the point that I ordered 2 more for wife and daughters car. They retail at £25 each including delivery from Sportsbikeshop.Co. They show the voltage constantly on the tiny screen, and they monitor and top up the batteries constantly. Hope this helps.

[welland]

14 hours ago, Chris Pritchard said:

During this Covid malarkey I tried an Oxford Oximiser 888 to keep my LS430 fully charged. Having been a Biker for 50 plus years, these are common with bikers. I was a little unsure as to the difference in amperage resistance  between large car batteries and the much smaller motorcycle batteries, as these Optimisers are designed to be left on indefinitely with no danger of boiling a battery, which would happen with a regular battery charger. However after a few days measuring the input and retained voltage, everything was fine. To the point that I ordered 2 more for wife and daughters car. They retail at £25 each including delivery from Sportsbikeshop.Co. They show the voltage constantly on the tiny screen, and they monitor and top up the batteries constantly. Hope this helps.

This sounds good, but I was trying to achieve the convenience of not needing a 240v power supply.  

[welland]

17 hours ago, ColinBarber said:

You are correct, use the OBD port at it has a permanent 12v feed.

It seems a good price, Halford do ones for a similar price but don't come with the OBD connector as standard.

 

Just remember that the power it produces is very low. It won't charge your battery but hopefully will maintain it with 12+ hours of daylight - so make sure it is fully charged first.

Understand, Colin.  Thanks.  

[welland]

I've ordered it now.  

[Steve_S]

On 5/23/2020 at 6:38 PM, ColinBarber said:

You are correct, use the OBD port at it has a permanent 12v feed.

It seems a good price, Halford do ones for a similar price but don't come with the OBD connector as standard.

 

Just remember that the power it produces is very low. It won't charge your battery but hopefully will maintain it with 12+ hours of daylight - so make sure it is fully charged first.

 

Indeed and it may only barely maintain it if at all. I have the AA solar charger with OBD connector and it wasn't able to maintain the charge in the starter Battery (I have an IS300h) from a low state (It was previously flat, I got it jump started then put a few tens of miles on it before I had to park it again) sufficient to get the car started after one week of operation. That was having the charger panel on dash. But as it was a North facing aspect I wouldn't be getting 12+ hours of full sun.

The car is in for a service and they have trickled charged it back up to full. Maybe now with the panel I can some confidence that if I can't drive the car for a week+ it will still start.

[sylm_2000]

Thanks bought one this week and using it with my RX450H 2015 reg. I hope this would keep the Battery cozy during the lockdown and limited use period.

I have a similar (Oxford) solar panel for my bike to keep it topped up during the winter months as I am a fair weather rider.

I am using the OBD port so has anyone managed to check if the Battery is actually getting charged? I am looking for evidence :)

[sylm_2000]

And BTW - £21.99 free delivery https://bars4cars.co.uk/collections/chargers/products/aa-essentials-12v-solar-powered-car-battery-charger-solar-panel-obd-version

[Herbie]

53 minutes ago, sylm_2000 said:

has anyone managed to check if the battery is actually getting charged? I am looking for evidence 🙂

Then this chart may help you decide:

[sylm_2000]

On 7/23/2020 at 3:50 PM, Herbie said:

Then this chart may help you decide:

thank you - this is great! I will check and update the post as I have my Lexus on the driveway with Solar OBD connected for over 5 weeks. Hope it starts 🙂

[Britprius]

Solar chargers for car Battery use need to have an output of 10 to 12 watts per hour minimum.
The problem is they are rated at maximum output in bright sunlight pointing directly at the sun. On dull days the output is likely to be half of the rated output at best, and of course this is is only in the daylight hours. Over a 24 hour period the average output of a 12 watt panel is likely to be in the region of 2 to 3 watts translating to 0.2 amps per hour. A panel rated at 2.4 watts will have an output around 0.05 amps per hour or 50 milliamp hours. This is not enough to maintain a Battery with a capacity of 60 to 70 amp hours. The internal losses "self discharge rate" of car batteries along with the standby loading of the alarm, and entry system will be more than this.

John.

[sylm_2000]

Agree and yes I learnt that the hard way! I checked using the multi meter and today it was 11.46v - not pleased with the charger and performance.

 

[Britprius]

51 minutes ago, sylm_2000 said:

Agree and yes I learnt that the hard way!

I was going to give this a "like", but felt I would be saying I like the fact that you got stung by the advertising of the item bought, and that is not my intent. 
I would return the panel as being not fit for purpose.

John.

[sylm_2000]

6 minutes ago, Britprius said:

I was going to give this a "like", but felt I would be saying I like the fact that you got stung by the advertising of the item bought, and that is not my intent. 
I would return the panel as being not fit for purpose.

John.

I use a solar trickle charger for my (yamaha) bike and it has worked reasonably well so I thought the same should okay for the car Battery. I should have looked into the amperage a bit more consideration. I relied on the advert and less on my electronics engineering degree 😞  

[OldTrout]

I did return mine.

At best it would have put off the day when there just wasn't enough to start the car by a week or so but there was no way it could maintain the Battery.

I had a long exchange with one seller who told me I needed a special ammeter to measure the current. His advert was a mass of contradictions. I returned that one as well.

Going for a drive once a week if you can is a better solution.

J

[welland]

On 8/24/2020 at 1:14 PM, sylm_2000 said:

thank you - this is great! I will check and update the post as I have my Lexus on the driveway with Solar ODB connected for over 5 weeks. Hope it starts 🙂

Let us know how you get on.

[welland]

On 8/24/2020 at 3:14 PM, sylm_2000 said:

Agree and yes I learnt that the hard way! I checked using the multi meter and today it was 11.46v - not pleased with the charger and performance.

 

Well, in my experience with it, it definitely does extend the time taken for discharge to reach a level where the car won't start. However, it is very difficult to assess how much extra time one gets.  A week or two, depending on weather....?

[welland]

Wondering if another solution is to fit an additional small Battery somewhere discrete - in the boot to boost storage capacity.  

[sylm_2000]

49 minutes ago, welland said:

Let us know how you get on.

So a quick update. After six weeks (no drive), I measured the Battery with a multimeter and it was 11.46 so I was rightly furious as it was clear that the solar PV has not worked at all. However the car started without any hesitation, the boot door (powered) opened seamlessly and managed to have sufficient charge after 6 weeks. I had two hours of drive and connected the solar panel via OBD back to the car. It is 2.4w charger and whilst I can't see Battery improvements, it is doing the job. 

My RX450H is 2015 reg (from new) so might be the Battery needs replacement anyway. For the upcoming season with less sun I am wondering if the solar charger will keep the Battery alive. It does work very well for my bike which I have tested for two winters so there's hope as science has proved otherwise. 

[OldTrout]

Sylm,

A 2.4W panel is nowhere near enough. 25W would be much better BUT beware that many panels I found on-line say they were many more W than their own figures for current give. One company whose ad gave three different outputs said I needed a special ammeter to measure the current. The wattage quoted will almost certainly be a maximum under optimum conditions: bright sun out of doors with panel at right angles to suns rays. Put the panel inside the car either stuck to window or laid flat and the maximum is already well down. Also if the panel were to be in an optimum position at noon it will not be for all the rest of the day.

Your bike may not have the drain due to car's electronics - security etc. Britprius tells me this is about 40mA i.e. about 0.5W. Unless your panel can supply 24 x 0.5 = 12Wh every day your Battery will slowly discharge. A small panel will slow this discharge so you may last long enough. You also need to add in self discharge. 

I hope this helps a little.

John

[ColinBarber]

1 hour ago, OldTrout said:

25W would be much better

but potentially too much unless it has intelligent circuitry to stop charging when the Battery is fully charged. Constantly charging a car Battery will damaged it.

[OldTrout]

1 hour ago, ColinBarber said:

but potentially too much unless it has intelligent circuitry to stop charging when the battery is fully charged. Constantly charging a car battery will damaged it.

True but then so too will letting it go flat. When prolonged sunny weather is expected, cover up part of the panel. Uncover for winter.

As you say some might have intelligent circuitry though which removes the problem.

John

[Britprius]

In theory a 25 watt panel will give out a little under 2 amps in ideal conditions, but unless you keep moving the panel to face the sun "very impractical" the average output over 24 hours is likely to be about 500 ma. This is enough to maintain a Battery of between 40, and 90 amp hours safely while still under some load from the cars systems without the risk of any damage. 

As the capacity of the Battery gets smaller say 12 amp hours typical of motorbike batteries there is a "slight" risk of over charging. The reason is that all lead acid batteries of whatever type have a self discharge rate given as a percentage of capacity.
As the Battery gets bigger in capacity the number of amps discharged in an hour increases. The percentage remains the same against it's capacity. Large batteries such as those used in forklift trucks can have a discharge rate of many amps. Charging at even 2 amps continuously  the Battery will still end up after a period discharged. This is why Battery chargers invariably have a Battery capacity limit in the instructions. A 4 amp charger will tyipically be listed as suitable for up to around 100 AH capacity batteries, and often there will be a setting for small capacity motorbike batteries.

Charge dumping circuits are used extensively in off grid solar panel installations. This is because the output of multi panel systems can output many amps, and charge a bank of batteries. If the batteries are not sufficiently discharged to be able to take the output of the panels over a period unless the charge current is dumped in some way the batteries would be damaged.

John.