Why MHs should have Digital Voltmeter's in the Cab

Belt powered bonfires I like to call 'em.

Yeah I hate to disappoint.

Negotiations fell through on the 'nother alternator for obvious reasons. Chalk this one up in the bad bodge column methinks.
Laying a hardwood floor and skirtings in a double room without right angles at the moment so it'll be another week or two.

Living in a house these days. Don't care much for it myself but can't convince swmbo to see reason!

The relic is still misbehaving.

It's not an or situation.

Fair enough.

Reasons off the top of my head;
Alternator failure, alternator malfunction. Alternator overloading.
Cranking voltage drop (starter battery health).
Unloaded charge voltage (starter battery DOD)
Parallel battery drop (Auxilliary bank DOD).
Left the lights on and engine off and didn't open the door?
Fridge left on and engine off?
Want to use the cab radio for a few hours but not past 12.5V?
Unfused short circuit (main starter motor conductor).
Battery resting voltage (age, health, parasitic drain); Saves one cranking and further damaging a flattened battery.
Electrical diagnostics.


I also have a compass and a GPS
I have a hard time convincing myself I don't need another ammeter. :pac:

Linking two batteries makes one bigger battery so by deduction you can observe the aux. batteries from the engine battery.

Monitoring the engine battery in the cab would be all that's needed there.

In the living quarters I have a much more accurate and sophisticated battery monitor which watches split bank voltage, and single bank current and DOD. I also have two DMMs as well as a current and voltage readout on a PSU I use to charge from mains.

I spent years full time without a decent meter and yeah stuff works but you'd be amazed how much you can improve a system once you know what's going on, and further amazed at how woefully inadequate some manufacturers promises of battery maintenance are fulfilled by their products.

"New" alternator arrived today.

Someone dropped it on the B+ and smashed the rectifier into the casing.
..shorted diode somewhere...alas...round 3.

Can't vouch for most of these but the datasheets look good. Probably need illumination for night-time driving.
Is this for the cab. or the living compartment?

0.3% accuracy sounds like a lot but on a 12v scale you need that accuracy otherwise the decimal is inaccurate which is ~12% charge or 25% usable.



http://www.ebay.co.uk/itm/12v-24v-3-WIRE-BLUE-VOLTMETER-BATTERY-INDICATOR-DASH-GAUGE-LED-CARAVAN-SOLAR-/251861780068?pt=LH_DefaultDomain_3&hash=item3aa421c664 3 wire is a good sign, one for power, one for measurement, having a sense wire bodes well, if it wasn't accurate then they wouldn't bother (easier read red LEDs than blue in daylight)

Anything you get on Ebay will need verifying with a trusted meter, some of them have a trimpot for calibration adjustment. Others sometimes you can just hack them with a well placed resistor.

Precision Panel Mount #1




Precision Panel Mount #2





Bargain Alert Battery Monitor




Personal Favourite ...pity it hasn't got an ammeter included.
The alarm functions are actually voltage sensing relays, you can autostart/stop a generator with it :cool:




This looks like a decent analogue 52mm gauge. At least the scale is wide enough to be interpretable and doesn't look entirely like it belongs in a rude boy car.




Make sure you wire it on dedicated conductors. No piggybacking +ives!! If you put the meter on a load carrying conductor you are not measuring the battery but the circuit it's attached to.

I'm blaming you for this Mr. Moodrater...all I needed was a hot-wired 20W resistor.



Pulley swapped from my tindernator.
Tested fine on the drill: 1.5A on near enough fully charged battery @ 14.4v.

Things to do tomorrow:

• Fetch a bigger conductor >35mm². The 16mm² I have earmarked won't do now.
• Swap alternators, fit shorter belt.
• Test alternator on old loom.
• Disconnect old B+ and label.
• Make battery cable.
• Run new B+ (9 times fatter) in flexible HT oil resistant conduit and connect.
• Swap 40A maxi-blade fuse for 150A mega fuse on B2B conductor.
• Remove 300A B2B conductor and terminate lugs with solder proper like.
• Wire manual B2B switch through coil of 200A M&B relay (don't have a 200A switch).
• Extend 150A cable from relay to deep cycles.
• Resist temptation to install another volt meter and ammeter.
  
  I've decided to leave the second switched circuit through the solar controller as is. The circuit is rated for > 45A with a 40A fast acting MCB. I'll reserve that switch for absorption/float which is the only time I'd need it.

moodrater wrote: »

Nice one, when you're planning on keeping the vehicle its an investment otherwise a massive waste of time

I'm just disconnecting and insulating the stock wiring, there's no need to pull it, I can always swaperoony later.

moodrater wrote: »

Just make sure theres nothing funky on your b+ before you fire it up this time.

Plan is patch the new alt. into the old loom, if it all looks ok then stoke her up with the side cutters in hand, if it works, refit the relic and off to the electrical wholesalers, then install the blighter...2.1kW Mwahaha!

I've got it down to 7 mins an alternator these days.

moodrater wrote: »

You could double up the 16mm cable if you have it already.

Don't you worry M, I'll find a good use for that 16mm² in time.
Nah, I hate that. Few reasons only I'd care about; it's untidy, the conduit or heatshrink needs to be a greater diameter than required, added contact resistance and the load balancing along the conductors becomes a product of the resistance of the terminations.
Now having said that I may go 16mm² to the busbar and 35mm² to starter, battery etc.
Really I should be Y-ing off the alternator between the battery banks as a more direct route but I'd rather not clutter the running gear and it's not like I'm loosing a whole lot on a 95mm² link.

moodrater wrote: »

Why the massive fuse on the B2B cable surely you won't want anywhere near that current or are Mr and Mrs 6V planning a family?

'cause that's the spec. Maxi blades only go to 100A iirc. Cables ought to be good for 150A. If yer gonna buy expensive fuses best not blow them eh!. Yeah realistically I don't expect to see more than 70A down that road, tbh I'm not changing that fuse for a long while because I'll only be using the upper limits of the new alternator come Wintertime.
...it might be a case of I say it here because it's good practice but I don't actually do it until it bothers me.:o


235Ah is enough, I have a hard enough time discharging 10% most of the year.
Next time I buy lead it'll be 2V. :cool:

Just finished fitting the hinges custom brackets for my relay...turns out it's 250A :pac: ...it's nearly 1.5kg...beast

2.3L but there's a 90Ah starter battery, 235Ah deep cycles, 250W refrigeration & 90W dry cell battery charging downstream of that.
Not that max. loading is as big an issue as keeping the voltage drop to a minimum.

35mm² to starter motor -> 50mm² to starter battery (stock) -> 95mm² to deep cycles -> 12mm² x2 circuits to DC loads

No idea, 600CCA on the label maybe, I'll confirm tomorrow.
Biggest I could shoehorn in there. I think she's 75Ah from factory.

50mm² from the battery, a feed from the busbar, and a send to the rearward loom iirc.

She's old, copper was cheaper 20 years ago.

Yup and it's still working too!
Mercedes T Series

Wiring doc here, see M1 pic. 5