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Re: Maintenance charging battery

Posted: Wed Sep 18, 2019 4:54 pm
by Canuk
There is lots of foam around the exit in my battery box so just ran the wires using the foam as protection. The lead has a fuse so even if it shorts out because of poor installations it will not harm the car.

Keep the cover on ,,keeps debris off the battery. But then for years batteries had no cover.

Re: Maintenance charging battery

Posted: Thu Sep 19, 2019 4:05 am
by Mamil
Just wanted to add a few clarifications to the information already on this thread...

1. There is no problem charging the DS battery in-situ with the small charging current used by a CTEK 5 charger. LR are just playing safe suggesting you remove the battery, and it's not an easy process, and requires some things re-setting on replacement so is a PITA.

2. No I wouldn't drive around with the battery cover off. AGM batteries are more sensitive to heat than wet cells, and can be cooked much more easily by the heat in the engine bay. That's why in the DS they are effectively in a separate compartment that has the air going to the internal air vents flowing over them. If you leave the cover off you are exposing them directly to the heat from the engine bay, and incidentally sucking in hot engine bay air to your ventilation system.

3. There is a sensitive bit of electronics called the BMS, attached directly to the negative terminal of the battery. This measures the flow of current in and out of the battery and provides this information to the car's ECU so it can calculate what state of charge the battery is at. If you connect the charger, or anything else for that matter like an accessory, direct to the battery negative post you are bypassing the BMS so it's calculation of battery state of charge will be inaccurate. That's one reason for connecting to the chassis ground point instead, or at very least to the non-battery side of the BMS. Second reason is that any voltage surges (sparks!) can easily damage the sensitive BMS. Not such a problem with the CTEK chargers because they are well protected, but other chargers and especially jump cables for jump starting can cause voltage spikes as you attach them which can damage the BMS. That's why it's safest as a general rule to only connect things to the chassis ground point on modern cars, not the negative battery terminal.

4. While it's OK to attach a charger at other points in the system, rather than direct to the battery, there can be issues. The accessory sockets/cigarette lighters on the DS are disconnected by a relay after a certain time the car is inactive, so are no use for charging. You need an always live direct connection. The trailer socket has such a wire, but it's a long way away from the battery and connected by a small gauge wire (2.5mm2), and there will be voltage drop as a result (the voltage at the end of the wire is not the same as what is put into it, the difference being lost as heat along the length of the wire). Why is this an issue - well the CTEK is quite a sophisticated charger and it relies on knowing the exact voltage of the battery at any point in time to decide on it's charging regime. If it's not sensing voltage accurately due to voltage drop it will not charge optimally. Also, it uses temperature compensated charging, ie. reduces the charging voltage if the battery is getting hot to avoid damaging it - especially important with AGM, as already mentioned above. If the charger is at the back of the car it won't be measuring accurately what the temperature of the battery is.

5. So, bringing all this together, the optimum solution is to connect charger by shortest and most direct route possible to the battery positive, and the chassis ground point (just behind the battery). Which is how I've wired mine and brought the socket out right next to the battery box so I don't have to take the lid off....

IMG_20190227_174628 (800x600).jpg


Re: Maintenance charging battery

Posted: Thu Sep 19, 2019 10:28 pm
by Lofty1
Thanks Mamil your advice is much appreciated.👍

Re: Maintenance charging battery

Posted: Wed Mar 25, 2020 3:46 pm
by Unclemort54
In these troubled times I’ll not be using the DS much, certainly won’t be towing our caravan. So, I’ve bought myself a CTek smart charger to help keep the battery in reasonably good condition. I’m going to wire in the connection plug so I won’t need to take the cover off each time it gets charged. I’ll do it pretty much in the manner that Mamil describes. However, after carefully surveying the job I noticed that next to the main chassis earthing point, which is where the wire from the negative terminal is bolted to the bulkhead (in the corner under the plastic trim) there is an unused threaded hole, M8x1.25. This will make a good earth for the CTek negative wire. Has anyone else noticed this hole?
By utilising this hole one can wire the CTek plug in without disconnecting any of the terminals. For the positive side I will put a clamping device on the battery terminal connector whilst I release the nut to then install the CTek positive wire. The wires will lead out as in Mamil’s picture.

Re: Maintenance charging battery

Posted: Thu Mar 26, 2020 9:14 am
by EYR
Agree with everything 'Mamil' says for optimum charging.
I charge via my towing socket with my CTEK, during the winter I was only interested in topping up the battery due to short journeys, and I felt that the once fortnightly and approx 4 hours before 'float' appeared on my charger was sufficient.
It was not optimum charging, but was enough to put something back into the battery which the system appreciated, its all I wanted really and it worked.

Re: Maintenance charging battery

Posted: Tue Mar 31, 2020 5:10 pm
by Paul41
Hi
I have bought a solar trickle charger is there any reason why I can’t connect this to the car via the towing electrics socket, it would make it so convenient to connect & disconnect this way ? My car is fitted with the solar windscreen so I presume the panel would not work if placed on the dash and plugged in to the OBD2 port

Many thanks in advance for your help with this


Re: Maintenance charging battery

Posted: Thu Apr 02, 2020 2:01 pm
by BobbyBox
Unclemort54 wrote:
Wed Mar 25, 2020 3:46 pm
In these troubled times I’ll not be using the DS much, certainly won’t be towing our caravan. So, I’ve bought myself a CTek smart charger to help keep the battery in reasonably good condition. I’m going to wire in the connection plug so I won’t need to take the cover off each time it gets charged. I’ll do it pretty much in the manner that Mamil describes. However, after carefully surveying the job I noticed that next to the main chassis earthing point, which is where the wire from the negative terminal is bolted to the bulkhead (in the corner under the plastic trim) there is an unused threaded hole, M8x1.25. This will make a good earth for the CTek negative wire. Has anyone else noticed this hole?
By utilising this hole one can wire the CTek plug in without disconnecting any of the terminals. For the positive side I will put a clamping device on the battery terminal connector whilst I release the nut to then install the CTek positive wire. The wires will lead out as in Mamil’s picture.
I too have wired my CTEK in the way Mamil describes. However, the second smaller chassis earthing point was already occupied with a smaller gauge black wire terminating there so I added the ctek negative lead and tightened. We're all good now.

I especially like Mamils trick of using the captive dust cap on the CTEK direct connect lead to attach it to the bulkhead so it is retained and wont rattle or flap about. Just need to dig out my Dymo for a label now...
BB

Re: Maintenance charging battery

Posted: Fri Apr 03, 2020 3:58 pm
by DRBA22
On my MY20, there is a negative terminal distribution plate about 10mm above the battery -ve clamp. It is difficult to make out whether the gap accounts for the BMS transducer. However, as there are a number of connections taken from this plate, I assume that it is at the same potential as the chassis and therefore a safe connection for the CTEK comfort connector -ve. Photo attached.
Your comments would be appreciated.
PS The photo confirms the AGM battery type.

Re: Maintenance charging battery

Posted: Sun Apr 05, 2020 2:48 pm
by Unclemort54
I think the BMS is under the -ve distribution plate on the -ve battery terminal. The photos below show what I have done. The secondary earth (left hand of the three terminals) is the one BobbyBox (above) refers to. I think using this makes a neat job of it although I decided to utilise the spare threaded hole (right hand of the three terminals in the photo).
Hope these help.

IMG_0042.jpeg

IMG_0040.jpeg

IMG_0041.jpeg


Re: Maintenance charging battery

Posted: Sun Apr 05, 2020 4:31 pm
by Chris b
Thanks for this info.
Had the CTEK on the DS from this morning (not used for a week), so have just switched off, repositioned the charger earth clip and switched back on (soon went back up to light 4 where it had got to before)