Alternators alternating!! How to...?

[Mickconnolly]

Hi all
In our Winnie we have 24volt (2x12vLA) starter battery and 12 v 2x200a/h LiFePo batteries for the house. Separated systems.

We have been travelling in sh1te weather for the past week and the solar which does a stellar job is just not up to the job at the moment. Currently the genie gets a one hour workout at least once a day.


I have to this point basically ignored the alternator in terms of a charging source for the house and to be honest I have not chased down anything about the charging of starting batteries either. The previous owner had the front dash “converted” to 12v from the OEM 24v. The dash leaks current like a sieve and due to batteries flattening on a regular basis I removed some fuses and have a “deadish” dash. Anyway that’s not the main point here. What I was wondering is if it is even possible let alone practical to wire up the output from the alternator to charge a 24v LA starter bank AND charge a LiFePo 12v pack AND stop the alternator from having a coronary!

Anyone have thoughts on this? I’m thinking it’s a complex solution that may cause more trouble than its worth.

[native pepper]

G'day Mick, I run a 12v charging system from a 24v start system. I have a redarc between the starter batteries and a 24v 60amp deep cycle bank, then it goes through a 24v-12v 60amp battery charger to either my 360ah gel (A/C), or 480ah lifepo4. The reason I don't run the 24v-12v charger from the start batteries, is to protect them from being drained.

It has worked really well over the years and always arrive somewhere with full batteries, when the gel pack fails, will replace it with 24v lifepo4. Can also switch the solar from lifepo4 to gel, so when the lifepo4 is full when camped, it charges the gel.

[T1 Terry]

Hi Mick, we have a few of the now NLA 24/12v 40 amp DC to DC chargers in stock here in Mannum and that would sort the alternator to house battery charging problem and can be wired to turn on/off with the ignition.
As far as the dash draining power, this could also be powered from an ignition switched relay so it was only powered while the alternator was running and powering the 24 to 12v DC to DC charger so it didn't drain the house battery.

T1 Terry

[Mickconnolly]

Thanks guys...I’m going to have to draw a picture to sort it out in my head.
So alternator to 24v stays as is.

Then 24v to 12v reduction to the LiFePos.

Two questions.
How can I make sure that the Starters are full before I start charging the house. It should not be a problem I don’t think and I guess the question is more “should I be concerned with this at all?”

The second is charging the LiFePo via the voltage reduction unit. This will require a charger as well???

Again thanks guys.

Mick

[T1 Terry]

Thanks guys...I’m going to have to draw a picture to sort it out in my head.
So alternator to 24v stays as is.

Then 24v to 12v reduction to the LiFePos.

Two questions.
How can I make sure that the Starters are full before I start charging the house. It should not be a problem I don’t think and I guess the question is more “should I be concerned with this at all?”

The second is charging the LiFePo via the voltage reduction unit. This will require a charger as well???

Again thanks guys.

Mick

The DC to DC is actually a 40 amp 12v charger and can be controlled by the T1 Lithium control system, just powered from the 24v battery. You can add in a relay that only allows it to turn on when the engine is running and because the output is 40amps @ 12v nominal, the input would only be 20 amps @ 24v nominal. The reason I add the "nominal" in there is because the alternator puts out anywhere up to 28v and the lithium battery requires anywhere up to 14v or even 14.4v on some occasions. With the 24v side being limited to 20 amps, the alternator has heaps of reserve capacity to continue charging the start battery all the time the engine is running so no need to hold off the lithium charging while you wait for the start battery to charge. Yet another benefit of using a DC to DC charger.
I asked Margaret to check the price and she came up with $300 plus postage, rather cheap compared to the $520 or so Redarc want for their unit Bernie has already put his hand up for one unit and we will need to hold some for jobs we do here, so as they say on TV "Stocks are limited" or something like that

T1 Terry

[Mickconnolly]

Thanks as usual Terry. I’ll contact you when we reach home on Friday week. To summarise...
- leave the current wiring alone from alternator to battery, alternator charges starter (24v) batteries 92x12volt wet acid.
- connect the DC to DC unit on to the 24 volt battery output. Connect the output of the DC to DC converter to the 12volt lifepo batteries as per any other connection at the terminals.
- the relay described protects the two starter batteries from being drained by charging the lifepo batteries while the alternator is not running, I.e. the truck is stopped.

Ok I think I got it!

Now can you tell me what the hell this is as you mentioned RedArc. They connected this to the batteries in both the starter pack and a seperate one on the house pack. It’s called a CE40 13.8. A charge equaliser ... I’m assuming it’s like a cross LA battery equaliser as one of the batteries is tapped for a 12 volt feed to the dash (previous owner got someone to change the dash accessories to 12 volt).
I’m assuming I simply leave this alone on the starter pack. I have already got rid of ithe one out of the house battery circuit.

Anyway, I got a spare one if anyone wants it...

Mick

[T1 Terry]

Keep hold of that Redarc battery equaliser and go on line to see exactly how you go about disconnecting it before you remove any battery terminals. Disconnection in the wrong order lets the smoke out instantly and no matter how hard you try you can't get the smoke back in.

For those that don't understand the smoke reference, there is theory that all electronic items are powered by smoke because as soon as you see or even smell the smoke that has escaped, the item no longer functions. The Lucas electrical system was designed using this smoke entrapment principle and as anyone who is familiar with anything British designed and built, it leaks, resulting in the electrical system no longer functioning as you had hoped it would

T1 Terry

[Mickconnolly]

Oooouuuuu!!! I must have been lucky... it’s disconnected and I think most of the smoke is still inside!!! Mind you I did take the batteries out first🤪