 | Home > Technical > Split charge relays and long term battery charger use |
 
|
|
|
| Cupboard Member Since: 21 Mar 2014 Location: Suffolk Posts: 2971   
|
I have two batteries in my Defender and a Victron VSR that manages them.
I sometimes have cause to go away for extended periods, and when doing so I leave the Defender connected to a charger (it's a Lidl smart charger) to look after the battery whilst I'm away. So far, I've been disconnecting the split charge relay so that it isn't energised all the time, but is this necessary? It would save a lot of faffing around if I could just plug the charger in and not have to fiddle with battery terminals. Part of me is saying that it won't be good for the relay to be pulled in all the time, on the other hand lots of industrial equipment has master contactors that spend their life energised and it's not exactly strenuous for it. |
||
29th Dec 2017 1:46pm |
|
| pannawonica Member Since: 21 Nov 2010 Location: Clackline Western Australia Posts: 568 
|
I have a bluesea VSR and charge the starting battery when I’m away for some weeks. From what I’ve seem the VSR senses the elevated voltage and both batteries are maintained. I see this as a good thing! With the bluesea you can mechanically seperate the two batteries if required, however I have never done or seen a need. The charger overcomes the parasitic loss from the relay which is very small!
 |
||
|
30th Dec 2017 2:05am |
|
| Vogler Member Since: 02 Nov 2014 Location: Brussels Posts: 309  
|
Pannawonica is correct, and I can hardly imagine that the low current of a charger in maintenance mode would wear out the contacts.
I took a slightly different approach and have installed a Blue Sea Dual Switch in parallel to a BEP-branded digital VSR. The switch has four connections and two positions, setup like this: Connection 1: starter battery positive/charging current Connection 2: unused, available for extras on the starter battery circuit Connection 3: house battery positive Connection 4: house battery circuits Position 'Off' disconnects all, so I can switch off all extra's and prevent the risk of an appliance unexpectedly draining the battery, or both batteries should the VSR fail to disconnect (which I have known to happen to someone else) Position 1 to connect 1&2 and 3&4, so switching on two circuits while keeping them separate.The VSR connects the batteries/circuits as usual.. Position 2 to connect 1,2,3 and 4 so combining the two circuits. In daily life, the switch is in position 1. The VSR connects 1 and 3 and thus both circuits when voltage on the starter circuit reaches a minimum. Position 2 allows me to override the VSR and combine both batteries with a heavy duty connection (450A) that can handle high currents for an emergency start. (the Cyrix can do this for a short time too, the BEP can't however). . The BEP DVSR also has the option to switch it off manually, comparable to what macfrank mentiones, and being digital has a very small consumption (0,04A IIRC). Greetings, Joris |
||
|
30th Dec 2017 3:38am |
|
| Cupboard Member Since: 21 Mar 2014 Location: Suffolk Posts: 2971
|
Thank you, I'll stop worrying then
My Victron quotes a quiescent load of 4mA which is pretty good, running load is 300mA. There are other things like the alarm and Ultraguage running off the main battery, then the tracker from the aux. I was quite surprised when it started first pull after three weeks parked up with the temperature at 0 a few weeks back, I wasn't supposed to be away for that long so hadn't put the charger on it. The bog standard Varta battery that it came with six and a half years ago is damned good. I just tried it to see what would happen, expecting to have to link the batteries. |
||
|
30th Dec 2017 10:55pm |
|
| Mdm Member Since: 11 Sep 2013 Location: Sunny Lancashire Posts: 1628
|
on my current set up i have a manual split charge.
i have two hard wired c tek battery charger leads so i can charge each battery separately. this saves any wear on the relay and allows each of the agm batteries to get a decent charge. |
||
|
31st Dec 2017 10:12am |
|
| wyvern Member Since: 13 Dec 2009 Location: Cornwall Posts: 2117 
|
I leave my 110 parked up for 3 weeks out of every 6 as I work away offshore. it starts first time every time. (touch wood!) I have a split charge relay that keeps the2nd battery ‘hotel services’ running and I never disconnect the relay when its parked up, nor do I ever run a trickle charger to the batteries either. The 110 does a lot a miles when I’m at home and the batteries are never put under pressure to run down, however I do run the cab heater overnight when camping off the hotel battery. If the vehicle is run often and for a reasonable time them I’m pretty sure that the batteries are able to cope with being left for a while. Poppy - TDCI (Puma) 110XS 2.2 - Camper conversion - see the build here - https://www.defender2.net/forum/topic56530.html Elgar -TDCI(Puma) 110XS Dormobile - now sold Devon & Cornwall 4x4 Response - DC126  |
||
|
31st Dec 2017 10:21am |
|
| MadTom Member Since: 10 Sep 2013 Location: Olomouc Posts: 625  
|
Relays wear mainly during switching - burning the contacts and mechanically wearing the moving parts inside. There is not any problem with relay switched ON when connected the charger for long time.
I have a different solution - I use standard 14,0V 10A switching power supply (from Meanwell), set to 14,4V and high current schottky diode in series between the supply and battery. 2 diodes in case of two batteries - each between supply and a battery. I use it not only for stand-by charging. Serial diodes are there to decouple the power supply from the battery and batteries to each other. 10A supply can fully charge flat battery in less than day and also power fridge of webasto heater during camping. For just trickle charge 1A is enough. Good 12V battery connected to 14,0V supply for a few day takes approx. 0,1A of less current - this is just the battery internal current to cover the loss in batteries made by self discharge. Instead of the power supply it is possible to use a solar cell with appropriate regulator - but only in summer. It is better to charge the battery with some sort of stand-by charging, than leave the battery go flat. "Drobek" = The Small One - Discovery 2, "Blufínek" = The Blue Thing - Defender 130, and for me at least Ford Mondeo |
||
|
31st Dec 2017 5:17pm |
|
| jst Member Since: 14 Jan 2008 Location: Taunton Posts: 8065  
|
i have a National Luma system and plug charger into the main battery, once thats up to spec the relay opens and both batts charge. Cheers
James 110 2012 XS Utility 130 2011 M57 bespoke Camper 90 2010 Hardtop 90 M57 1988 Hardtop |
||
|
31st Dec 2017 8:43pm |
|
| walfy Member Since: 29 Aug 2007 Location: Frome Posts: 2661
|
Not sure what brand I have but it's what ever Mobile Centre sell as a kit. Running 2 Odyssey batts. Thought I was having a prob with the aux batt which would of been a pain. But I managed to locate the issue. My traffic cam had thrown a hissy fit and would randomly start and not shutdown. Disconnected that and my charging issues with the aux batt stopped.
It doesn't matter what kit you get, the important bit is having it wired in properly with the correct rate of cabling 110 D250 SE HT 110 USW SOLD RRE HSE Dynamic Gone, wife killed it VOLVO XC60 R Dynamic with some toys Polaris RZR 900XP SOLD |
||
|
1st Jan 2018 10:34am |
|
| diesel_jim Member Since: 13 Oct 2008 Location: hiding Posts: 6098 
|
Just to get my head around these split charge relays.....
When they're rated to 140amps, or 500amps in come case... is this what they'll handle between batteries, or what they'll handle as an output from the alternator? so, if for example, your aux battery was connected to a winch (and some other device that maybe cause a drain during the day, hence why you'd have the split charge in the first place, otherwise for just a winch you wouldn't bother with a split) then you started winching, the winch pulls a lot of current... is this is where the current carrying capacity is measured? I would asume the output from an alternator flowing through the split relay would cause the same damage (if it were going to) as a high current load flowing into the aux battery. |
||
|
3rd Jan 2018 7:40am |
|
| Hendrix Member Since: 04 Oct 2016 Location: North Notts Posts: 103  
|
Slightly different approach I fitted a solar panel to help keep aux battery topped up when we are away using the fridge. Just used the secondary output from the solar regulator to keep the vehicle battery topped up. We have left the Defender parked up for a couple of months without issue. It does live outside mind, but i guess most Defenders do.
|
||
|
3rd Jan 2018 8:47am |
|
| macfrank Member Since: 05 Nov 2015 Location: somewhere in the north Posts: 1081  
|
From the NL manual: Click image to enlarge Click image to enlarge So the relay is between batteries. With a winch the alternator should provide most of the current directly to the winch. In practise (without a winch) I measured a max. current of 30A between the batteries when one was flat and the relay engaged after connecting a CTEK. |
||
|
3rd Jan 2018 10:39am |
|
| Cupboard Member Since: 21 Mar 2014 Location: Suffolk Posts: 2971
|
It's the maximum current through the relay. For instance, mine is rated at 230A continuous which is more than enough. If I'm running my winch (connected to the main battery) it will draw something like 100A from the alternator, and 150A from each battery. The worst case scenario for the relay would be jump starting myself, and it's rated at a much higher current short term for that purpose. Note that ratings are often different for AC vs DC and depend on the type of load too. That's all down to the contacts breaking the load rather than the conductors overheating. |
||
|
3rd Jan 2018 10:00pm |
|
| NoDo$h Member Since: 18 Aug 2007 Location: Buried in deer guts in Dorset Posts: 972
|
Don't forget that most smart chargers pulse the current, which tends to lead to the VSR rapidly switching with each pulse if that pulse is above the "relay closed" threshold. I spotted this when charging my cranking battery using my CTEK as I could hear a rapid clicking that I swiftly realised was the VSR.
I now pull the fuse from the VSR trigger wire when charging with the CTEK.
54 Freelander modded for mud 2008 D3 SE 2010 90 XS SW 1978 88 Series 3 undergoing surgery with a new owner 2007 90 County Truck Cab - gone 2006 D3 SE - gone 2004 Freelander Sport - gay 1999 Disco V8 ES rotted to bits |
||
|
3rd Jan 2018 11:31pm |
|
|
|
| All times are GMT |
< Previous Topic | Next Topic > |
Posting Rules
|
Site Copyright © 2006-2024 Futuranet Ltd & Martin Lewis
