Kea Conqueror – Raising the Alternator Charge Volts to 14.5

Kea Conqueror – Raising the Alternator Charge Volts to 14.5

My ex rental 2009 Kea Conqueror is based on a 2008 Toyota VDJ78 Troop Carrier with a 4.5 litre V8 diesel.

When I changed the house battery to a 12 V 120AH AGM type, I wanted to charge the battery as quickly as possible via the alternator, after a night’s use on battery.

I inserted a 1N5404 diode in the alternator sense line, substituting the original fusible link with an ATC type blade fuse holder with the diode soldered across the base.
Toyota call the alternator sense wire “ALT S”.
This gives me high volts with no fuse inserted, and original volts when a blade 10 A fuse is inserted and shorts out the diode.
The diode is polarised so that the cathode or device “bar or ring” is towards the alternator.

I removed the original ALT S fusible link, and added my device between the battery positive and the connection block originally used to connect the fusible link.

The fuse-holder that I used is similar to Jaycar part SZ2045, chosen for robust build.

After installation, I sprayed INOX into my device and on the connectors.
And I have teased out the fuse and diode just for the photos; it is normally lashed back into the cable loom beside the battery out of harm’s way with large twist ties.

When the alternator is charging at 20 amps, my battery wiring (in 13.5 sq mm copper) and ammeter shunt resistance of 0.01 ohm, limit the current and thereby the charge voltage (by introducing calculated these discrete losses) to 14.3 at the battery terminals, rising to 14.5 at 5 amps.
The cable size was deliberately chosen to be not too large, so as to limit the current on high volts charge, and also to keep the volts high at a medium charge of 10 amps, and thus achieve a degree of constant current charging similar to three stage charging characteristic for AGM batteries. I learned this concept from a previous career, and an earlier Kea HiAce installation.

I am aware of the safety, fusible link removal, and battery implications of such a modification.
If you are unsure of these constraints, then don’t attempt this on your vehicle.
Photos give details of diode+fuse device, parts locations and numbers.

Hopefully of use to some,
Cheerio, mike

Attachment 262815Attachment 262816Attachment 262814Attachment 262817Attachment 262818

I now have two diodes in series, the second is relay switched in and out from a switch on the vehicle dash.
Each can be separately shorted (by ATC fuse) as well, so as to revert to "no diodes".

Vcharge (at +5 amp) 0D = 13,8, 1D = 14.2, 2D = 14.6 volts.

Second battery is 125AH AGM (and N70ZZ as the vehicle and starter).

Works well, especially on those days with limited charge time between night camps.

At home, both diodes are shorted out of circuit to avoid overcharge.
On a trip, I enable both diodes, and rest on the first diode at a Vcharge of 14.2V at 5A.

I don't charge above 25 amps, and switch low to high charge rate when Acharge falls below 15A.

It helps to have what I have, a dash mounted accurate bi-directional ammeter 0-20A switchable to 0-200A.

(Lucky also to have the time to do all this stuff).

Please just be very aware that using an elevated charge voltage will surely and eventually gas charge a vented battery, as the charge condition "tops up" and then "floats" at 14.6 volts with two diodes in the sense line.
This wont be a problem if you are continually charging and discharging, eg when you are in drive/camp/drive/camp mode.
But if you drive for a few days for long hours and your charge current falls right down, and your Vcharge rises, disable one or both diodes to avoid overcharging, heating and gassing.

And none of this should be a problem when touring just using one diode AND your alternator Vcharge is not over 14.2V.
When you get home, disable the diode(s).

Gassing in the short term is not a problem (and for short periods every now and then MAY be slightly beneficial), other than the possibility of some vented acid vapour possibly starting some small patches of corrosion around hold downs and battery trays.
Long term gassing is best avoided, and you will lose electrolyte, and have corrosion problems.

All of the above normally only applies to the vented type (eg N70ZZ series and similar) and which is possibly being parallel charged with the second or "house" battery.
Vented means that there are gas vent holes and or filler caps for each cell.
The second battery may be vented also, or AGM, or other.
There is less risk with overcharging AGM and "maintenance free" batteries, when using diodes in your alternator sense line.

I have recently removed my alternator diode arrangement, and installed a Redarc BCDC 1225 in car charger.

I have now optimised my vehicle battery and battery charging to what is best for me.

The reason for this post is to assist others in positioning the Redarc unit, as space in the vehicle is cramped.

After carrying out some temperature tests with a remote thermometer with sensor mounted in the engine bay, I decided to install my unit at the rear of the engine bay as per photo.
I also checked with the factory that the unit will not commence current fold-back due temperature until 55 deg C.

The unit is mounted on an "L" shaped aluminium plate, fixed to the firewall with two M5 screws into Rivnuts, and one M6x25 bolt under the Redarc unit into the top flat section of the firewall area.
Redarc mount bolts are 4 inverted M6x25 bolts with nuts, and using washers and Nylock nuts on top.

The unit is cabled to the house battery as per instructions (I used 13mm2 cable), and works well.
I have actually used an "LV" Redarc type in my 2008 vehicle, and a normal BCDC1225 will work just as well.
Caution with later vehicles; contact Redarc (not an agent) to confirm that you need a normal or "LV" type for your situation.

Attachment 358762