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DSC-off

Member Since: 16 Oct 2014
Location: North East
Posts: 1400

2015 Defender 110 Puma 2.2 XS CSW Aintree Green

Battery box with split charging.

I've added a simple split charge system to a leisure battery box that I've had for a number of years. The box had been used as a standalone power supply for a compressor fridge, and was fine for 4 or 5 days without needing charging.
A planned 2 week camping trip requires a way to charge up the battery while travelling. Both the battery and fridge are used in multiple vehicles, so a permanent fix in the Defender is not suitable.

The battery is a Numax XV27MF motorhome battery, 100AH and 900MCA. This was deliberately chosen over a pure leisure battery as it is capable of jump starting a vehicle if required, while still retaining a level of 'deep cycle' operation.
(Note, if jump starting, the jump leads would be connected directly to the battery terminals, not the box, and the split charge lead not plugged in)
The battery is housed in a Numax box:

Click image to enlarge

Rather than fit massive cables, oversize fuses and relay, I've chosen to replicate a caravan split charge system that has worked well for years on millions of caravans, where they charge through the trailer socket.
The voltage sensing relay used, Maypole MP2883, does not need an additional switch wire from the alternator and has a maximum load of 30 Amps. Cost £10 to £12.

Click image to enlarge
This is how it will be installed with fuses and a plug, note there are currently no fuses in the battery box:

Click image to enlarge

Starting at the Defender's battery, a Blue Sea battery post fuse box was fitted. Very easy to fit on a Puma, a great way to add permanently live fuses, and it leaves 3 spare.

Click image to enlarge
The wire from the 30A fuse was routed out of the under seat box via the heated seat wire grommet. Then under the carpet to the rear load area.

The Fast Plug used to disconnect/remove the battery box is suitable for upto 60 Amps, available at Halfords, normally used for audio amplifier power. One part is fixed, screwed to a trim panel between the window trim and wheel box. Positive is from the Blue Sea fuse box (above) and negative is grounded to the body via a suitable existing screw nearby.

Click image to enlarge

The other half of the plug has 2x positive wires and a single negative wire (brown wire). The relay requires 2 feeds, rather than a single 30 Amp, probably due to the size of the unit. So the 2 feeds are both fused at 15A before going to the relay.
The other 2 fuses in this box were used to add fuses for the cigar lighter socket (20A) and the battery indicator / voltmeter (3A).

Click image to enlarge

Click image to enlarge
Terminals 6 and 2 are connected to the isolation switch, the battery will not charge if the switch is 'off'. The relay ground terminal (0v) was connected to the negative screw terminal inside the box.
Terminal 4, not used, is permanently live if box is plugged into the Landrover and there is power going into the relay.

I added an LED voltmeter to give a more accurate reading, piggybacked onto the battery indicator, both of these only operate when a momentary switch is pushed. Adding additional 12v or USB sockets would be easy now the battery box has fuses.

It's been tried, both batteries were fully charged beforehand. The relay switched on as soon as the engine fired and the alternator started working. Apparently it's set to switch on at 13.5v and off at 12.9v. After stopping the engine it took a few seconds for the voltage to drop and then the relay turned off. All worked as expected.
I've not yet tried it with the leisure battery at a low charge, where it may put a higher current into the battery. That needs to be tested, just to be sure the fuses and wiring are OK.

A further improvement in progress is a new lower part for the box, with a better battery clamp and method of securing in the Defender.

Last edited by DSC-off on 21st Apr 2022 8:35am. Edited 1 time in total

20th Apr 2022 10:21pm

macfrank

Member Since: 05 Nov 2015
Location: somewhere in the north
Posts: 1072

2015 Defender 110 Puma 2.2 SW Keswick Green

Very well executed

21st Apr 2022 5:51am

Dinnu

Member Since: 24 Dec 2019
Location: Lija
Posts: 3414

2012 Defender 90 Puma 2.2 CSW Santorini Black

Very well planned too.

Maybe just install ferrules on the ends of the wires that go in the split charge relay. 1988 90 Hard Top, 19J Diesel Turbo, Shire Blue - Restoration ongoing
2012 90 CSW, 2.2TDCI, Santorini Black

21st Apr 2022 7:22am

DSC-off

Member Since: 16 Oct 2014
Location: North East
Posts: 1400

Thanks both.

Ferrules. - yes, great idea, I'll get some.

21st Apr 2022 8:39am

DSC-off

Member Since: 16 Oct 2014
Location: North East
Posts: 1400

Update.
Just got back from the camping trip. All worked well, no issues and the Stornoway black pudding got home safely.

Before the trip I made a new lower part for the box from plywood, stronger and with proper carrying handles. 2 tie down loops were added to the load shelf and a ratchet strap used to hold it down. The plywood board on top of the box is to spread the load on the lid.

Click image to enlarge

Before setting off the battery was fully charged at home and on the 3 days travelling to Stornoway the fridge was run from a power socket in the landrover. On arrival at the campsite the fridge was plugged into the batterybox, it ran for 4 days and the voltage dropped to 11.8v, still good for another day or so. (I turn the fridge off overnight, 10pm to 8 am to save power) On the 5th day I went for a drive and plugged the battery box in to charge it, came back with 13.8v.
For the rest of the trip, 6 days, the fridge was left connected to the battery box, which was charged up every day while driving. No issues, no switches to remember, dead easy, use and forget.

So for occasional use you don't need to spend £1000 plus on fancy batteries, chargers, wiring and battery trays.
A simple leisure battery, a £12 relay and few bit and pieces will do the job.
But it doesn't sound high tech and impressive

23rd Jul 2022 10:06am

macfrank

Member Since: 05 Nov 2015
Location: somewhere in the north
Posts: 1072

23rd Jul 2022 11:26am

Mo Murphy

Member Since: 01 Jun 2008
Location: Letchworth Garden City, Herts
Posts: 2223

1984 Defender 90 BMW M57 3.0 Diesel HT Auto Pennine Grey

A man after my own heart, although the shame of finding a solution that is not reassuringly expensive may stay with you 😉😁
Mo The Land Rover 90 - Many are called, few are chosen.

50 Shades of Pennine Grey

23rd Jul 2022 1:20pm

DSC-off

Member Since: 16 Oct 2014
Location: North East
Posts: 1400

23rd Jul 2022 5:49pm

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