[jaco_n]

Still investigating my solution..

I know it's been talked about many times, but there is no definite answer. So I was wondering what the other PJ owners out there use for charging the 2nd battery. Cole Hersee? NL Split Charger? DC-DC charger?.
I'm in two (actually three) of which solution to take of the three.

Why did you select the specific solution?

[Blister]

After much reading (Thank you for all the people I have been in contact for advice, by far too many to mention) the various forums and internet and the 4x4 shops (NL, etc.), I decided on the following;
1 Semi Deep Cycle "Deltec"
2 4 way Switch - Seaworld - to switch electrics off/ system operate on Batt 1/ System operate on Batt 2 or Both batteries
3 Cole Heresee Solenoid Relay
4 30A Relay protected with a Diode - as a latching circuit
5 35mm2 Welding Cable (approx 5m) plus lugs and soldering
6 2off 100A fuses (of which the wire was removed and modified to fit 35mm2 W Cable)
7 Cole Heresee Push Start (Manual Override)
8 Timer Relay
9 Low Voltage warning with LED and Piezzo Buzzer per Battery (Settings: Batt 1@ 75% & Battery 2@50%)
10 Equus Volt Gauge with toggle switch and individual blue LED to indicate which battery is being monitored
12 Six Fuse Box with a 40A relay that will isolate all loads (fridge, two way radios, camp lights,etc.) from Batt 2 on low Voltage

My system allows me to "automatically" charge Batt 2 but with a manual override if the timer plays up. Its nice to be able to have the flexibility to use the batteries between the primary circuit - start, lights, a/c, etc. and secondary circuit - fridge, two way radios, camp lights,etc. or together - jump start and or winching

The last of the cables are being installed as well as the last low voltage board is being put together

[HBannink]

This is a subject much like the old "what is the best oil?" discussion and I think that it would border on impossible to get a definitive answer so this is the route I went.

I started off doing a LOT of reading and research and I know a heck of a lot more about batteries than I used to. I have all the technical skill and experience to design my own custom circuit and build my own split charging system so I started costing and sourcing the needed bits and pieces. This is where reality kicked in and I found the savings made by doing it myself does not really justify the effort put in to the project. My system would have been based around the Cole Heresee solenoid and the cost of the materials came close to the nat luna split charging system. The deciding factor was the ultimate reliability of the system and the effect of finding out that I had overlooked a detail or two when the system fails somewhere in the bundu and all my steak defrosts.

So rather than reinventing the wheel I went with the nat luna and everything just worked out fine with the best part of the deal not coming in the package... Peace of mind
As soon as the alternator starts pumping power in to the starting battery a timer of 5min. is started and when it kicks in both batteries are connected to the alternator, when the vehicle is switched off the battery voltage stabilises at about 12.5 volt so when a voltage of 12.7 is reached the relay opens and only the second battery is drained. Simple and tested.

On the battery side I opted for a second crank battery as the time needed to fully charge a deep cycle was too long for me and I doubt that I will need to drop my voltage so low as to justify a deep cycle and with two 96 ah units I should be able to power a winch or weld without too much problem

One important point regardless of which system you go for is the wiring. Use the thickest cable you can get hold of (25mm - 35mm) and keep the runs as short as possible and solder all your joints to ensure good contact. Fit fuses to all your cable runs, 12v is a devil and folks tend to treat it with contempt, it wont shock you but it WILL start a fire quicker than you can blink your eyes.

[4ePajero]

I have a National Luna Box, but that was because I did not do research beforehand.

If I have to do it again, it will be a DC-DC charger.
I can't see any negatives except (initial) price, but the difference between the DC-DC charger and the comprehensive list as given in the original post can't be large.

Simplicity is the determining factor.

I have a Benton 220V AC intelligent charger (for out-of vehicle charging), but if you don't have one, the DC-DC charger can be used with a simple 220V AC - 12V DC converter to give an intelligent 220V charger.

[Greg_SA]

I am also busy planning my dual battery system... my requirement is to be able to run my NL fridge and a few LED lights for the campsite for about 2 days at a time. Then charging will be say 5 hours of driving the next day.

I will probably go for a NL Intelligent Solenoid, to sort out the switching - it is a neat simple solution that isn't too much more expensive than just buying a Cole Hersee solenoid itself. I won't get the battery mponitos, etc. I'll carry a multimeter, and my NL fridge has an indicator anyway.

The alternator output voltage is 14.25V as far as I remember. But i need to figure out which battery to buy... Deep-Cycle or High-Cycle. It sounds like 5 hours of driving won't be long enough to chrage a deep cycle (charging rate of 5-10 A/hour? can anyone confirm?). So a high-cycle (that has a safe depth of discharge of 20%) sounds like a better option.

With regards to the DC-DC cahrager... will this dramatically improve the chrage time? How high is the output voltage of these chargers? Much more than 14.25V ?

So far it looks like a NL solenoid and a high-cycle Deltec battery is my best option?

[4ePajero]

With regards to the DC-DC charger... will this dramatically improve the charge time? How high is the output voltage of these chargers? Much more than 14.25V ?

It is generally accepted that alternators have difficulty in charging deep cycle batteries to 100% capacity. Most users have intelligent 220V chargers to charge the batteries "out of vehicle".

The DC-DC is as efficient to charge the deep cycle battery as the 220V equivalents, USING THIN CABLES!

[Greg_SA]

Ah... thanks Gerhard. So if my alternator only charges the battery to say 90%, I obviously loose a bit of capacity, but are there any other problems? Will the battery get damaged because it always remainds slighly dischraged?

[4ePajero]

Why pay for a 105AH battery and then have a 95AH available?

Eventually it boils down to simplicity (for me).

[jaco_n]

I have a Benton AC - DC charger that I use for normal eskom charging. What would the negative be to use a inverter (12v - 220V) and use the Benton as a so called DC-DC charger?
I have also spoken to Jean in Cape Town that sells the BC 1212-15 DC - DC charger. Have a high AMP out put andthe device cost is about R1400.00

[4ePajero]

I have a Benton AC - DC charger that I use for normal eskom charging. What would the negative be to use a inverter (12v - 220V) and use the Benton as a so called DC-DC charger?

Should work.
The efficiency would not be great (% of losses would be high), but that would not prevent it from working.
The point is that you need an intelligent charging system for deep cycle batteries, which a vehicle alternator is not.