Project What has two seats, a mid-mounted 6 cylinder engine, and a turbo? Rewire complete - finally success!

[Stinkwheel]

On 08/12/2024 at 09:12, mat_the_cat said:

Only just seen your reply Jim. My worry is that seeing as L is +115V relative to earth, and N is -115V, if I create a N-E link then I'm going to get significant current flow! I've checked with a test lamp wired between L and E, and this does cause the RCD to trip, so I suspect the lower voltage just means that the test current on my RCD tester is insufficient to trip it.

I've added a further refinement to the charging system now, as I was just a little worried about constantly running the alternator on the edge of overheating.

So I've fitted this Victron unit between the charger and batteries. It works by using the fuse as a shunt, and by changing the fuse value it limits the charge current to 90% of the fuse capacity. This should limit things to around 70A as it stands.

Couldnt help but read Victron as Vectron in my head

That aside, nice job on the elastic trickery taming and distribution 

[mat_the_cat]

On 08/12/2024 at 09:12, mat_the_cat said:

I've fitted this Victron unit between the charger and batteries. It works by using the fuse as a shunt, and by changing the fuse value it limits the charge current to 90% of the fuse capacity. This should limit things to around 70A as it stands.

I hadn't actually tested it when I wrote that post, and once I fired it up was getting exactly zero charge into the batteries so not a win. It turns out these are only designed (and supported) to work with Victron batteries. But, by connecting a data cable between the two ports on the unit, apparently I can fool the unit into acting as though a battery is connected.

Rather than pay 40 quid for a Victron branded cable, seeing as it appeared simply a standard 3 terminal M8 connector, I bought one from RS for under a tenner. Not sure the brand will catch on...

This had the desired result of making the 'alternator enabled' light come on, so happy days! Or so I thought...

I'm only getting around 2 amps charge current, so something is clearly amiss. Might have to think again what I use, as maybe it does need a Victron battery to communicate with.

[mat_the_cat]

A bit of fact-finding later, and it turns out that on the original units then simply looping a cable between the two ports would fool it into thinking a healthy Victron battery was connected.

Quote

If it's just a matter of using current limiting, which is what the BMS does, then yes - you'll have to trick the BMS by connecting a BTV cable to the M8 connectors. But this is basically fooling the BMS; The Load and Charge Disconnect output no longer works and with it there is no battery protection. It is neither recommended nor supported.

There was then a redesign, which meant that it was no longer that simple. But fair play to Victron, even though it's not something they officially support, they do seem helpful and have suggested a workaround.

Quote

Hello, Yes, I know what the issue is and that's the fact that due to a redesign an unwanted phenomenon arises. The extention cable doesnt have enough resistance to work well so since this. So what's needed is to have a 56k resistor in line with each wire in the cable, then you should see the max power again.

All 3 soldered in place.

Looking promising!

And it works exactly how I want. I don't mind that I don't have the full functionality, as that's all taken care of by the BMS built into the batteries. Current is limited so I'm not hammering the alternator, and if I want I can stop charging at the flick of a switch.  Over 60 amps at little more than idle speed.

[mat_the_cat]

I'd previously mentioned that the shunt readout in the above picture was a bit of a game-changer, showing just how slowly the alternator alone was charging my previous LA batteries, and how little of their capacity I was actually using at high currents, before the voltage sag caused the inverter to shut down. So although cheap it did a useful job, but there are a few things I'm not 100% happy with.

The backlight is on whenever current is flowing - flashing to signify charging, and constant when being discharged. So another 10mA or so of drain 24/7.
The display has an pointlessly high resolution to 3 decimal places, reducing readability. The decimal point is tiny, so difficult to see whether I'm charging at 61.28A, or 6.128A
The 100% charged level is set upon installation, and now I have the LiFePO4 batteries, I can see that sometimes the full point (i.e. when the charge current tails off to next to nothing) doesn't correspond to 100%. I suspect that it's not measuring discharge and charge currents equally accurately, so getting out of sync after a few charge/discharge cycles. So I then have to reset it manually when I know the batteries are full.

So on Christmas day, full of food and booze and with Amazon vouchers to spend, I did some research. I don't want to sound like a brand snob, but the Victron equivalent ticked a lot of boxes.

Backlight can be set to either on, or timeout after a set period. Current drain is under 1mA. Would have preferred it to be powered from the sidelights but never mind.
Resolution to 1dp, although below 10A goes to 2dp.
It automatically sets the 100% level whenever over a certain voltage, current has dropped to a certain level, after a configurable delay.
It has an additional input I can use to monitor the starter battery.
It'll calculate the remaining battery life at the current...erm...current.
I can configure it to stop the charging above a set voltage, which may prove useful to avoid high voltage/low current charging whilst driving, which isn't ideal for longevity.
The accuracy specs are better, ±0.4% versus ±1%. 
As a bonus, it has bluetooth so can easily check stuff without looking at the dashboard. I can envisage time in bed doing exciting stuff like checking out the app.

It arrived and I've now fitted it, although yet to route the cable properly. Despite the display being smaller, it's actually easier to read.

The shunt however, is a fair bit bigger than the old one which I had just managed to tuck under the seat base lid. This one, I've had to cut a bit of a hole; equivalent to a supercharger poking through the bonnet

[cobblers]

Another benefit of the victron one is that you don't even have to be in the van to check the voltage... just near it. I'm sat on the sofa and I can tell that I've left the fridge on in my van over xmas so the battery is at 55% and I could probably do with going out there and turning it off.

I bought the one with the screen, but the screen is actually inside  a cupboard and I never look at it - I always use the app.

The relay function on them is very handy - you can set it to trigger when charging, ot at certain voltages, or at certain battery percentages - I used the one on my old van to disable the water heater automatically at 85% capacity, and then I could manually override it if I was certain I wanted hot water. That way I could just leave the water on all the time, it would automatically heat and keep hot when I was driving, or the solar was charging hard.

 On the new van (with lithium) I have it set to disable the DC-DC charger when the battery gets to 80% - it will improve the life of the battery which has way more capacity than I need, and it saves some space so that the solar will always be worked as hard as it can.

[mat_the_cat]

16 minutes ago, cobblers said:

On the new van (with lithium) I have it set to disable the DC-DC charger when the battery gets to 80% - it will improve the life of the battery which has way more capacity than I need, and it saves some space so that the solar will always be worked as hard as it can.

With the Victron BMS I've now got (albeit merely acting as a current limiter) there is a pair of terminals which are looped out by default to allow it to pass current. I can now run that loop via the NC contacts of the gauge's relay, and easily disable charging at a set level. I could also route the mains charger through the same BMS, and cut that charge current at the same level, meaning I can leave the mains charger on all winter to keep the starter battery on float charge, without worrying about the LBs. I didn't realise it until now, but the relay is actually a bistable one, so whichever position it's in it still won't draw more than the nominal 1mA.

[cobblers]

Like you I spent ages avoiding victron stuff because it seemed needlessly expensive for the advertised specs, but I've realised it's made and tested to be actually used. It generally does work, and is configurable to work quite well.

Aint nobody got the money for their batteries though 😱

[cobblers]

If it's any help, I've put some cycles on the battery in the workshop with our programmable dc loads and a charger on a timer switch to sort of simulate a few weeks of general use, being charged at 60A for an hour, discharged continually at a varying current from 0.5A to 40A, trickled at 5A for a few hours a day to simulate a solar panel but never let it get more than about 75% full. The victron recommended battery settings work quite accurately at tracking the capacity even when it's had small cyclical loads without ever getting full up. If you leave the settings as lead acid (with a lower charge efficiency particularly) then the battery monitor will drift down to reporting a incorrectly lower remaining capacity over time.

I changed the "charged voltage" to 14.3 as my battery was still drawing a bit of current occasionally at that voltage.

 

Incidentally I think these batteries use the 280AH cells, not 305AH - there are several other manufacturers selling the same super budget "300AH" battery in the same case and people have tore them down to find 280ah cells. A little disappointing - the capacity will probably drop from 305ish to 285 ish over the first 20 cycles, then plateau at that. 

 

 

 

[mat_the_cat]

Think my settings are fairly similar to that, although still tweaking them.

I've set it to show 100% full at the point the current is next to nothing; with me not discharging them heavily at the moment it's always 90%+.

Next job is the overdue service...got all the bits, just need the time!

[mat_the_cat]

Just a few finishing off jobs now done.

I needed to route the wiring properly for the new meter,  But Victron had supplied probably around 10 metres of cable which I didn't really want to try and coil up out of sight. It was just a standard RJ12 lead, so a simple job to trim to length, and just fit another plug to it.

I also bought a new remote control for the replacement mains charger. The only real functionality it has (apart from a status LED) is being able to switch on and off Sleep mode without messing about with the DIP switches on the charger. I suspect that's a crafty move to make you buy the remote! Sleep mode is just a half power charge (40A) without the rather loud cooling fans running, although it turns out that it'll still run in full power mode until the temperature rises.

Unfortunately the remote for the previous charger was bigger than the new one...

...and due to a numpty moment whilst cutting out the original hole, the new one no longer covered the butchery.

The nearest solution I could think of was to use a matching blanking plate to the FCU , and cut a hole in that for the remote.

Two small holes to fill, but easy to do without being obvious.