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Cupboard



Member Since: 21 Mar 2014
Location: Suffolk
Posts: 2971

United Kingdom 2011 Defender 110 Puma 2.4 HT Corris Grey
Split charge relays and long term battery charger use
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.
Post #674090 29th Dec 2017 1:46pm
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macfrank



Member Since: 05 Nov 2015
Location: somewhere in the north
Posts: 983

Germany 2015 Defender 110 Puma 2.2 SW Keswick Green
Good point. I never thought about wear and tear of the relay. Since they're speced to very high amps I would think low trickle charge currents shouldn't cause any damage to the contacts even over a long period of time. The spring... I don't know.

I leave mine engaged for weeks during winter (National Luna).

But if you want to disable the relay without fiddling with the battery terminals, I'd suggest you put an easily accessible switch in the ground connection of the VSR (this should be a relatively thin wire).

I did this, to switch the relay off e.g. when one battery gets really low or when reconditioning one battery. I have a CTEK plug on each of the batteries so I could treat them separately if necessary.
Post #674112 29th Dec 2017 3:15pm
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pannawonica



Member Since: 21 Nov 2010
Location: Clackline Western Australia
Posts: 568

Australia 
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! Thumbs Up
Post #674318 30th Dec 2017 2:05am
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Vogler



Member Since: 02 Nov 2014
Location: Brussels
Posts: 309

Belgium 2015 Defender 110 Td5 HT Chawton White
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
Post #674323 30th Dec 2017 3:38am
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Cupboard



Member Since: 21 Mar 2014
Location: Suffolk
Posts: 2971

United Kingdom 2011 Defender 110 Puma 2.4 HT Corris Grey
Thank you, I'll stop worrying then Smile

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.
Post #674562 30th Dec 2017 10:55pm
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Mdm



Member Since: 11 Sep 2013
Location: Sunny Lancashire
Posts: 1508

United Kingdom 
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.
Post #674619 31st Dec 2017 10:12am
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wyvern



Member Since: 13 Dec 2009
Location: Cornwall
Posts: 2066

United Kingdom 2012 Defender 110 Puma 2.2 XS CSW Firenze Red
Cupboard wrote:
Thank you, I'll stop worrying then Smile

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.


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
Post #674621 31st Dec 2017 10:21am
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MadTom



Member Since: 10 Sep 2013
Location: Olomouc
Posts: 556

Czech Republic 1999 Defender 130 Td5 HCPU Baltic Blue
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 Smile
Post #674741 31st Dec 2017 5:17pm
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jst



Member Since: 14 Jan 2008
Location: Taunton
Posts: 7664

2011 Defender 110 Puma 2.4 USW Stornoway Grey
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 XS Utility
130 Puma Station wagon/camper (in the making)
90 Puma Hardtop
Post #674817 31st Dec 2017 8:43pm
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walfy



Member Since: 29 Aug 2007
Location: Frome
Posts: 2637

 
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
Post #674904 1st Jan 2018 10:34am
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diesel_jim



Member Since: 13 Oct 2008
Location: hiding
Posts: 6026

United Kingdom 2006 Defender 110 Td5 SW Epsom Green
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.
Post #675315 3rd Jan 2018 7:40am
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Hendrix



Member Since: 04 Oct 2016
Location: North Notts
Posts: 102

England 2013 Defender 110 Puma 2.2 USW Santorini Black
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.
Post #675322 3rd Jan 2018 8:47am
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macfrank



Member Since: 05 Nov 2015
Location: somewhere in the north
Posts: 983

Germany 2015 Defender 110 Puma 2.2 SW Keswick Green
diesel_jim wrote:
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.


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.
Post #675342 3rd Jan 2018 10:39am
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Cupboard



Member Since: 21 Mar 2014
Location: Suffolk
Posts: 2971

United Kingdom 2011 Defender 110 Puma 2.4 HT Corris Grey
diesel_jim wrote:
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?



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.
Post #675570 3rd Jan 2018 10:00pm
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NoDo$h



Member Since: 18 Aug 2007
Location: Buried in deer guts in Dorset
Posts: 972

England 
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
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Post #675602 3rd Jan 2018 11:31pm
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